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The study analysed the tribological performance of five different polymer composites: polyetheretherketone reinforced with 30% carbon fibres—PEEK CF30, polyetheretherketone reinforced with 10% carbon fibres, 10% graphite and 10% polytetrafluoroethylene—PEEK MOD, polytetrafluoroethylene reinforced with 25% carbon fibres—PTFE CF25, polyoxymethylene with 30% carbon fibres—POM CF30 and ultra-high molecular weight polyethylene—UHMW PE. The polymers were tested under the sliding regime of a reciprocating stainless-steel ball on a polymer disc, with test parameters expected for hydraulic valves. Two environmentally safe lubricants were used: glycerol and water. The selected polymer materials and their tribological properties were compared based on the coefficient of friction and the specific wear rate. The worn surfaces were examined using scanning electron microscopy, and the transfer film was analysed using the energy dispersive spectroscopy technique. When tested in glycerol, a comparable and low coefficient of friction was measured for all polymers (~0.02). At the same time, a significantly lower coefficient was measured for all polymers in glycerol compared to water-lubricated conditions (~0.06–0.22). The polymers differed in the measured specific wear rate, which increases significantly in water for all polymers. A lower specific wear rate was measured for three polymers with higher microhardness: PEEK CF30, PEEK MOD and POM CF30. In water, PEEK CF30 showed superior tribological properties under harsh conditions but was well followed by POM CF30, which showed the most intense transfer film.

Uvod: Za izdelavo ortoz in protez pogosto uporabljamo plastiko in polimerne kompozite z ogljikovimi vlakni. V današnjem času pa so zaradi vse večjega povpraševanja po okolju prijaznih materialih in želji po znižanju cen kompozitnih materialov raziskovalci začeli posvečati pozornost naravnim vlaknom in matricam naravnega izvora. Namen: Glavni namen diplomskega dela je bil prepoznati in preučiti materiale na naravni osnovi, ki se uporabljajo pri izdelavi ortoz in protez. Metode dela: Za pisanje diplomskega dela je bila uporabljena deskriptivna metoda za iskanje domače in tuje internetne literature. Zbrano literaturo, ki je v angleškem jeziku smo iskali v različnih podatkovnih bazah kot so Science Direct, PubMed, Google Schoolar in Cochrane Library. Rezultati: Uporaba materialov iz naravnih virov se je po vsem svetu povečala zaradi okoljskih vidikov in gospodarskih koristi v primerjavi z uporabo neobnovljivih virov. Prednosti kompozitov iz naravnih vlaken so večja elastičnost, biološka razgradljivost, prijaznost do okolja in cenovne ugodnosti, izkazujejo pa tudi veliko trdnost, togost in korozijsko odpornost. Razprava in zaključek: Na podlagi študij smo ugotovili, da so naravna vlakna primerna za izdelavo protetičnih pripomočkov, saj zadostujejo vsem potrebnim kriterijem v ortotiki in protetiki. Če je ležišče izdelano iz naravnih materialov kot so kenaf, bambus, juta in ostala naravna vlakna, je okolju prijazno in hkrati povzroča človeškemu telesu manj alergij, povezanih z umetno izdelanimi materiali. Introduction: Plastic and polymer composites with carbon fibers are often used to make orthoses and prostheses. Nowadays, however, due to the increasing demand for environmentally friendly materials and the desire to reduce the price of composite materials, researchers have begun to pay attention to natural fiber and matrix of natural origin. Purpose: The main purpose of the thesis was to identify and study the natural materials used in the manufacture of orthoses and prostheses. Methods: A descriptive method for searching home and foreign internet literature was used to write the thesis. The collected literature, which is in English, was searched in various databases such as Science Direct, PubMed, Google Scholar and Cochrane Library. Results: The use of materials from natural resources has increased worldwide due to environmental considerations and economic benefits, compared to the use of non-renewable resources. The advantages of natural fiber composites are greater elasticity, biodegradability, environmental friendliness and cost benefits, but they also exhibit great strength, stiffness and corrosion resistance Discussion and conclusion: On the basis of studies, we found that natural fibers are suitable for the production of prosthetic devices, as they meet all the requirements needed in orthotics and prosthetics. If the bed is made of natural materials, such as kenaf, bamboo, jute and other natural fibers, it is environmentally friendly and at the same time causes fewer artificially produced materials connected allergies to the human body.

Lanena i staklena vlakna imaju usporediva mehanička svojstva, no povezivanje polarnih bioloških vlakana s apolarnom polimernom matricom predstavlja problem kod prenošenja opterećenja s matrice na ojačalo. U ovom radu istražen je utjecaj vrste smole i ojačala na rastezna svojstva kompozita. Epoksidna (EP) i poliesterska smola (UP) ojačane su lanenim i staklenim vlaknima. Načinjeni su kompoziti UP/lan, UP/staklo, EP/lan te dva kompozita EP/lan/staklo slagana na način da su staklena vlakna u jednom od njih u sredini, dok su kod drugog u blizini vanjskih ploha. Rezultati ispitivanja uspoređeni su s pravilima Hrvatskog registra brodova (HRB) za kompozite ojačane staklenim vlaknima. Rastezna svojstva istraženih kompozita bolja su od minimalnih propisanih vrijednosti s izuzetkom posljednjeg hibrida kod kojeg je došlo do grešaka pri izradi. Kompozit ojačan staklenim vlaknima superioran je kompozitima s lanenim vlaknima, što pokazuje važnost dobre povezanosti matrice i ojačala. Međutim rastezna svojstva kompozita s lanenim vlaknima također su u skladu s pravilima HRB-a. Flax and glass fibers have comparable mechanical properties, but the adhesion of polar biological fibers with an apolar polymer matrix presents a problem in transferring the load from the matrix to the reinforcement. In this work, the influence of the type of resin and reinforcement on tensile properties of composites was investigated. Epoxy (EP) and polyester resin (UP) are reinforced with flax and glass fibers. Composites UP/flax, UP/glass, EP/flax and two composites EP/flax/glass were prepared in such a way that the glass fibers in one of them are in the middle plane, while in the other they are near the outer surfaces. The test results were compared with the rules of the Croatian Register of Shipping (CRS) for composites reinforced with glass fibers. The tensile properties of the investigated composites are better than the minimum prescribed values, with the exception of the last hybrid composite, where manufacturing errors occurred. Composites reinforced with glass fibers are superior to those with flax fibers, which shows the importance of a good bonding between the matrix and the reinforcement. However, the tensile properties of composites with flax fibers are also in accordance with the CRS rules.

This study presents the results of acoustic emission (AE) measurements and characterization in the loading of biocomposites at room and low temperatures that can be observed in the aviation industry. The fiber optic sensors (FOS) that can outperform electrical sensors in challenging operational environments were used. Standard features were extracted from AE measurements, and a convolutional autoencoder (CAE) was applied to extract deep features from AE signals. Different machine learning methods including discriminant analysis (DA), neural networks (NN), and extreme learning machines (ELM) were used for the construction of classifiers. The analysis is focused on the classification of extracted AE features to classify the source material, to evaluate the predictive importance of extracted features, and to evaluate the ability of used FOS for the evaluation of material behavior under challenging low-temperature environments. The results show the robustness of different CAE configurations for deep feature extraction. The combination of classic and deep features always significantly improves classification accuracy. The best classification accuracy (80.9%) was achieved with a neural network model and generally, more complex nonlinear models (NN, ELM) outperform simple models (DA). In all the considered models, the selected combined features always contain both classic and deep features. Ta študija predstavlja rezultate meritev akustične emisije (AE) in karakterizacijo pri obremenjevanju biokompozitov pri sobnih in nizkih temperaturah, ki jih lahko opazimo v letalski industriji. Uporabljeni so bili senzorji z optičnimi vlakni (FOS), ki lahko prekašajo električne senzorje v zahtevnih delovnih okoljih. Standardne značilke so bile pridobljene iz meritev AE, za pridobivanje globokih značilk iz signalov AE pa je bil uporabljen konvolucijski autoenkoder (CAE). Za izdelavo klasifikatorjev so bile uporabljene različne metode strojnega učenja, vključno z diskriminantno analizo (DA), nevronskimi mrežami (NN) in ekstremnimi učnimi stroji (ELM). Analiza je osredotočena na klasifikacijo izpeljanih AE značilk za razvrstitev izvornega materiala, za ovrednotenje prediktivne pomembnosti izpeljanih značilk in za ovrednotenje zmožnosti uporabljenega FOS za oceno obnašanja materiala v zahtevnih nizkotemperaturnih okoljih. Rezultati kažejo robustnost različnih konfiguracij CAE za izpeljavo globokih zanačilk. Kombinacija klasičnih in globokih značilk vedno bistveno izboljša natančnost klasifikacije. Najboljša klasifikacijska natančnost (80,9 %) je bila dosežena z modelom nevronske mreže in na splošno so kompleksnejši nelinearni modeli (NN, ELM) boljši od enostavnih modelov (DA). Pri vseh obravnavanih modelih izbrane kombinirane značilke vedno vsebujejo tako klasične kot tudi globoke značilke.

Characterization of acoustic emission (AE) signals in loaded materials can reveal structural damage and consequently provide early warnings about product failures. Therefore, extraction of the most informative features from AE signals is an important part of the characterization process. This study considers the characterization of AE signals obtained from bending experiments for carbon fiber epoxy (CFE) and glass fiber epoxy (GFE) composites. The research is focused on the recognition of material structure (CFE or GFE) based on the analysis of AE signals. We propose the extraction of deep features using a convolutional autoencoder (CAE). The deep features are compared with extracted standard AE features. Then, the different feature sets are analyzed through decision trees and discriminant analysis, combined with feature selection, to estimate the predictive potential of various feature sets. Results show that the application of deep features increases recognition accuracy. By using only standard AE-based features, a classification accuracy of around 80% is obtained, and adding deep features improves the classification accuracy to above 90%. Consequently, the application of deep feature extraction is encouraged for the characterization of loaded CFE composites.

The high cycle fatigue behaviour of autoclave-cured carbon fibre-reinforced polymer (CFRP) composite gears is investigated. The CFRP gears were milled from a composite plate and tested in mesh with a steel drive gear under five torque loads ranging between 0.4 and 0.8 Nm in unlubricated conditions. A detailed gear damage analysis is conducted by employing scanning electron microscopy and high-resolution optical microscopy. Epoxy matrix microcracking is found to be the damage mechanism that leads to the final delamination failure. CFRP gears exhibited a significantly improved performance and a longer fatigue lifespan in comparison with the polymer and polymer composite gears.

Tehnologija 3D-tiska je prinesla nove možnosti za izdelavo piezoupornostnih merilnih zaznaval. Tehnologija je relativno nova in je na področju električno prevodnih materialov pomanjkljivo raziskana. Zaključno delo obsega teoretično opredelitev piezoupornostnega učinka v različnih materialih, pri različnih vrstah obremenitve in mehanizme njegovega delovanja. V sklopu zaključnega dela je bilo predstavljeno 3D-tiskanje in procesni parametri, ki vplivajo na električno prevodnost polimernih kompozitov. Predstavljena je bila tudi razlika med statično in dinamično piezoupornostjo. Ob dinamični piezoupornosti kompozitov so bili predstavljeni uspešno izdelani koncepti 3D-natisnjenih pospeškomerov in njihove lastnosti. 3D printing technology has brought new options for production of piezoresistive gauges. The technology is relatively new and the research is limited when it comes to electrically conductive materials. The final thesis gives a theoretical definition of the phenomenon of piezoresistivity in different materials and under different types of loads. It also gives a theoretical overview of different mechanisms of piezoresistivity. As part of the final thesis, 3D printing and process parameters that affect the electrical conductivity of polymer composites have been presented. The difference between static and dynamic piezoresistivity has also been presented. Along with the dynamic piezoresistivity of composites, successfully developed concepts of 3D printed accelerometers and their properties have been presented.

Analizirani so bili karakteristični signali akustične emisije, ki nastanejo kot posledica različnih mehanizmov lomov v materialu. Signali so bili pridobljeni z upogibnega obremenjevanja polimernih kompozitov s steklenimi in karbidnimi vlakni. Popis značilnosti signalov v časovni ali frekvenčni domeni ni zadostoval za nastanek razločljivih gruč v prostoru vektorjev značilk. Iz tega razloga so bile uporabljene nove značilke, izpeljane z globokim učenjem konvolucijskega avtoenkoderja, ki so vsebovale informacijo o vsebini zvezne valčne transformacije. Po odstranjevanju točk osamelcev z metodo DBSCAN je bilo z vektorji značilk doseženo tvorjenje bolj razločljivih gruč kot s prvotnimi vektorji značilk. Nenadzorovano razvrščanje vektorjev značilk karakterističnih signalov vsakega kompozita posebej je bilo izvedeno z metodo K-means. Primerjava izpeljanih vektorjev značilk visokofrekvenčnih karakterističnih signalov kompozitov z različnimi vlakni je razkrila raznolike gruče, ki so bile uspešno razvrščene z metodo spektralnega razvrščanja. The characteristic acoustic emission (AE) signals generated as a result of different damage mechanisms in the material were analyzed. The signals were obtained from bending of glass (GFE) and carbon fibre epoxy (CFE) composites. Characterization of signals in the time or frequency domain was not sufficient for the formation of distinct clusters in the space of feature vectors. For this reason, new features with time-frequency domain content were extracted from deep convolutional autoencoder. After removing the isolated points by the DBSCAN method, the formation of more distinct clusters was achieved with respect to the original feature vectors. The unsupervised classification of the feature vectors was performed separately for each composite using the K-means method. Comparison of the extracted feature vectors of high-frequency characteristic signals of GFE and CFE composites revealed diverse clusters that were adequately sorted using the spectral clustering method.

V diplomski nalogi smo najprej opravili pregled literature kompozitnih materialov in veziv za popravilo čevljev za smučarske skoke. Opisan je postopek popravila z izboljšavo lastnosti smučarskega čevlja v pregibu, s čimer ne podaljšamo le življenjske dobe čevlja, ampak omogočimo skakalcu tudi boljši občutek v vseh fazah skoka. Po dolgotrajni uporabi pa se na pregibu v kompozitu pojavljajo delaminacije in razpoke, ki so posledica nizke oprijemne trdnosti med plastmi. Na podlagi literature o kompozitnih materialih, tkaninah in njihovih površinskih obdelavah, ki omogočijo večjo oprijemno trdnost med plastmi smo izbrali dve vrsti steklenih tkanin (platno, keper) in ju primerjali glede trdnosti in kakovosti adhezijskega oprijema s strižnimi in upogibnimi preizkusi ter z mikrostrukturno analizo porušenih standardnih vzorcev. Na osnovi rezultatov in analiz smo ugotovili, da so vlakna s keper pletenjem bolj primerna za popravilo, saj se ob manjši razslojitvi predvideva tudi kasnejša obraba kompozita zaradi zunanjih vplivov, predvsem vlage, ki je stalno prisotna na ojačanem delu. In the diploma thesis, the literature review of composite materials and binders for the repair of ski boots with reinforcement of the bend was made. The repair process leads to improvement of the properties of the ski boot in the bend section, which not only prolongs the life-span of the boot, but also allows for a better feel during all phases of jump. After a long-term use, delaminations and cracks appear on the bend, which are the result of low inter-laminar strength between the layers. Aim of the research was evaluate different type of fabrics which would yield to a higher quality of material. A review of the literature on composite materials, fabrics, and their surface treatments, which provide greater grip strength between layers, was performed. We selected and compared the strength and quality of the adhesion of two types of glass fabrics (plain, twill) using shear and bending test, followed by microscopy of failed specimens. Based on the results and analyzes, we found that the fibers with twill knitting are more suitable for repair, as with less stratification, later wear of the composite due to external influences, especially moisture, which is constantly present on the reinforced part.

Kompozitni materiali se pogosto spajajo z lepljenjem. Problem lepljenih spojev pa je, da so nezanesljivi, saj lahko pride do nenadne porušitve. Lepljene spoje zato pogosto predimenzioniramo, delno pa lahko ta problem rešimo s hibridnimi spoji, kar pomeni, da lepljeni spoj ojačamo z mehanskimi pritrdilnimi elementi, ki delujejo kot varnostni člen v spoju in prenašajo del obremenitev. V tem delu smo izdelali in natezno testirali različne kombinacije lepljenih in hibridnih enojnih prekrovnih spojev z lepljenci iz aluminija 2017-T4 in kompozitnega polimera, ojačanega z ogljikovimi vlakni. Ugotovili smo, da lepljeni spoj z dvema kompozitnima lepljencema prenese približno 2-krat večjo obremenitev, če sta se lepljenca utrdila skupaj z lepilom, kot če se je lepilo utrdilo posebej. Ugotovili smo tudi, da ima kombinacija lepljencev vpliv na trdnost spoja, in sicer lepljeni spoj kompozit-aluminij prenese ~21 % večjo obremenitev, kompozit-kompozit pa ~50 % večjo obremenitev v primerjavi z lepljenim spojem aluminij-aluminij. Trdnost hibridnih spojev, ki smo jih dodatno zavarovali s kompozitnimi zatiči iz ogljikovih vlaken, ni bila višja od lepljenih spojev. Pri spojih z zatiči iz aramidnih vlaken pa se je trdnost povečala v manjši meri. Pri obeh vrstah pa sta zatiča nekaj časa vzdrževala oba spajana dela skupaj tudi po porušitvi lepljenega spoja, pri čemer se je razteznost spoja podaljšala. Composite materials are often joined together by adhesive bonding. However, the problem is the unreliability of adhesive joints, which means they can suddenly fracture. Due to this, adhesive joints are often overdesigned, but the problem can be partially solved by using hybrid joints. This means that the adhesive joint is reinforced with mechanical fasteners, which serve as a safety element and carry a part of the load. In our research, we have created and tested different combinations of adhesive and hybrid single lap joints with adherends of aluminium 2017-T4 and carbon fiber reinforced composite. Our research shows that the adhesive joint with two composite adherends can carry approximately 2-times greater load if the adherends have been cured together with the adhesive, compared to the adherends and the adhesive being cured separately. Our research also shows that the combination of adherends has an effect on joint strength, namely composite-aluminium can carry a ~21 % greater load, while composite-composite a ~50 % greater load in comparison to the adhesive joint aluminium-aluminium. We have not found any improvement by using composite pins made out of carbon fiber, and only a small improvement of the maximal load that the hybrid joint can take by using a pin made out of aramid fibers in comparison to adhesive joint. However, both types of pins have kept the joined parts together even after adhesive failed, resulting in higher joint strain.

Ogljikova vlakna so snovi, zgrajena iz ogljikovih atomov in imajo izjemne lastnosti, predvsem, ko sestavljajo kompozit. Njihova izdelava je zahtevna, toda končni produkt je kakovosten in zaradi tega dosega tudi visoke cene na trgu. Ogljikova vlakna so kar petkrat močnejša od železa, imajo visoko trdnost in so korozijsko odporna. So odlično električno prevodna, imajo visoko natezno trdnost in nizek koeficient toplotnega raztezka. Niso škodljiva za človeka in kar je skoraj najboljša lastnost, so nevnetljiva. Čeprav so ogljikova vlakna nevnetljiva, je vnetljivost še vedno velik problem, ko ogljikova vlakna združujemo v polimerne kompozite. Poznamo tri najpogostejše polimerne osnove, ki se uporabljajo v kompozitih. To so epoksi, vinilester in poliesterska smola (poliesterska smola je le redko uporabljena z ogljikovimi vlakni). Vsak kompozit ima polimerno osnovo, ki je vnetljiva, zato se za visoko stopnjo nevnetljivosti, kompozitom dodajajo snovi, ki vnetljivost zavirajo. Pravimo jim zaviralci gorenja. Zaviralce gorenja lahko nanašamo v kompozit na različne načine. Lahko jih vmešamo v polimer med procesom izdelave, lahko jih kemijsko vgradimo v glavno polimerno verigo. Uporabimo lahko tudi zaviralce gorenja, ki se nanašajo kot zaščitna plast ali pa sami od sebe tvorijo zaščitno last, ko pridejo v stik z dovolj visokimi temperaturami. Zaviralce gorenja v splošnem delimo na fosforjeve, dušikove, halogenske, intumescenčne ter anorganske. Halogenski zaviralci gorenja temeljijo na dveh elementih, kloru in bromu, anorganski pa na aluminiju in magneziju. Anorganski zaviralci gorenja večinoma dodajamo le kot katalizatorje, da pospešijo delovanje drugih zaviralcev gorenja, ki so dodani kompozitu. Intumescenčni zaviralci gorenja ob povišanih temperaturah tvorijo zaščitno plast, ki varuje kompozit pred vžigom in razpadom. Za polimerne kompozite z ogljikovimi vlakni se večinoma uporabljajo halogenski in fosforjevi zaviralci gorenja. Prav fosforjevi zaviralci gorenja so začeli nadomeščati halogenske predvsem zato, ker so halogenski zaviralci gorenja škodljivi za človeka in okolje. Učinkovitost zaviralcev gorenja lahko določamo z različnimi tehnikami. Navadno merimo mejno vrednost kisika, to je koncentracija kisika, pri kateri snov še gori, lahko izvedemo skupino testov UL-94 ali pa s kalorimetrijo izmerimo sproščanje toplote in z rentgensko fotoelektronsko spektroskopijo spremljamo sestavo kompozita. Z dodajanjem zaviralcev gorenja kompozitnim materialom, se soočamo tudi z nevšečnostmi. Če pride do vžiga materiala in zaviralec ni učinkovit, lahko pride do učinka svečnega stenja, kjer gori polimer na ogljikovih vlaknih, vse dokler gorenje ni umetno prekinjeno oz. zmanjka goriva. Problem nastane tudi v polarnosti zaviralcev, kajti bolj polaren zaviralec gorenja kot polimerna osnova oslabi strukturo kompozita in privede do slabših mehanskih lastnosti. Danes se v kompozitih z ogljikovimi vlakni uporablja epoksi smola. Ker so materiali, zgrajeni iz epoksi smole lahki, lahko nadomestijo druge, prej težje materiale, kar je uporabno predvsem v letalski in avtomobilski industriji. Sprva so se takšnim kompozitom dodajali halogeni zaviralci gorenja, danes pa se zaradi nevarnosti vedno bolj uporabljajo fosforjevi. Potrebno je dobro poznati tako lastnosti zaviralcev gorenja kot tudi kompozita, da lahko dosežemo dobro odpornost proti vnetljivosti in tako še izboljšamo lastnosti polimernim kompozitom z ogljikovimi vlakni. Carbon fibres mainly consist of carbon atoms and they have some outstanding properties, especially when it is integrated in a composite. Although the production of carbon fibres is complex, the final product has great quality, which is why carbon fiber materials are expensive in the market. Carbon fibres are five times stronger than iron as well as rigid and corrosion resistant. Electric conductivity of carbon fibres and their tensile strength are high and thermal expansion coefficient is low. They are not poisonous for people in addition to not being flammable, which is one of their best features. Flammability, however is still a very big problem, when carbon fibres are put into polymer composites. There are three main polymer matrices, which can be used in polymer composites: epoxy resin, vinylester resin and polyester resin , which is rarely used with carbon fibres. Since almost every polymer has a polymer matrix which is flammable, special materials are added to the composites in order to make them non-flammable. They are called flame retardants and they can be integrated into composites in different ways. They can either be added to polymer matrix during the production process or they can be integrated in the main polymer chain. Flame retardants, which are added as protective coating or which form protective coatings during the exposure to high temperatures can also be used. In general, flame retardants can be divided to phosphorous, nitrogen, halogen, intumescent and inorganic flame retardants. Halogen flame retardants mainly contain one of two elements (chlorine or bromine) and inorganic flame retardants are generally made of aluminium or magnesium. Inorganic flame retardants are mostly used as catalysts, so they speed up the effect of other flame retardants added to the composite. Intumescent flame retardants create a protective layer at high temperatures, which protects composite from ignition and degradation. Mainly halogen and phosphorus flame retardants are used for polymer composites with carbon fibres. Since halogen retardants appear to be harmful to people and to the environment, phospohorous flame retardants started to be used as a substitute. Effectiveness of flame retardants can be determined by using various techniques. Most commonly the limiting oxygen index, and shows the percentage, where material still burns. In addition group of UL-94 tests can be performed or determine heat release with calorimetry or we can watch a chemical composition of product with x-ray photoelectron spectroscopy. Because of the addition of flame retardants to composite materials, several problems emerge. If the ignition of material happens and the flame retardants are not effective, a candlewick effect could happen. This means that the polymer is burning on carbon fibres until fire is turned down artificially or the fuel runs out. Another problem occurs in the polarity of flame retardants if flame retardant is more polar than polymer matrix, structure of composite becomes weak, which leads to bad mechanical properties. Nowadays, epoxy resin is mostly used in polymer composites with carbon fibres. Materials from such substances can replace other, heavier materials, which is very useful in aviation and automobile industry. Firstly, halogen flame retardants were added to such composites, and because halogen flame retardants are toxic, more and more phosphorus flame retardants are used. Properties of flame retardants and composites have to be well researched, so that good flame retardancy can be reached and that is how polymer composites with carbon fibres properties are even improved.

Zbog održavanja ili poboljšanja kvalitete života, nastoji se smanjiti proizvodnja sintetskih polimera, a naglasak staviti na biorazgradljive polimere. Jedan od predstavnika biorazgradljivih polimera, polikaprolakton, najveću primjenu pronalazi u području biomedicine. Čisti polikaprolakton posjeduje dobra mehanička svojstva što ga čini čes-tim izborom, no svojstva se mogu i poboljšati pripremom kompozitnih materijala. Odlike kompozitnih materijala s polimernom matricom brojna su kvalitetna svojstva koja im omogućuju široku primjenu te vrlo često zamjenjuju klasične materijale. Njihova izrada omogućuje formiranje materijala s poboljšanim svojstvima u odnosu na svojstva poje-dinih komponenti. U novije vrijeme, sve je veća potražnja i primjena polimernih kompozita na bazi polikaprolaktona jer posjeduju modificirana svojstva koja omogućuju širu primjenu i iskoristivost polikaprolaktona kao biorazgradljivog polimera. Njihova je najčešća primjena u koštanom i tkivnom inženjerstvu gdje se kao visokokvalitetni materijali ko-riste za izrade koštanih i tkivnih konstrukcija. U ovom je radu dan literaturni pregled polimernih kompozita na bazi polikap-rolaktona, opisana su provedena ispitivanja, svojstva i potencijalne primjene ovakvih materijala.

Polietilen se često upotrebljava kao matrica u kompozitima zbog svoje lake preradljivosti, kemijske otpornosti te dobrih mehaničkih svojstava. Izradom kompozita omogućuje se šira primjena u odnosu na čisti polimerni materijal. Željezovi oksidi prikladni su za širok spektar primjena pa i kao punila u polimernim kompozitima. Primjerice, imaju potencijal za ulogu UV stabilizatora u polimernoj matrici. U ovom su radu polimerni kompoziti sa željezovim oksidima ispitani metodom diferencijalne pretražne kalorimetrije. Kompoziti su sačinjeni od LDPE-a kao polimerne matrice (kontinuirane faze) te željezovih oksida kao nanopunila (diskontinuirane faze). Korišteni su sljedeći željezovi oksidi: akaganeit i hematit. Uzorci su podijeljeni u dvije skupine od kojih je jedna podvrgnuta UV starenju u UV komori. Rezultati pokazuju da su ispitani uzorci otporni na UV starenje, odnosno da navedeni oksidi pružaju efektivnu zaštitu polietilenu niske gustoće.

Automobilska industrija jedna je od najvažnijih grana industrije u svijetu, a potreba za zamjenom konvencionalnih metalnih materijala sve je veća zbog nametnutih visokih zahtjeva koje proizvođači moraju zadovoljiti. Najvažniji zahtjev je smanjenje emisije štetnih plinova koji se postiže upotrebom manje količine energije potrebne za vožnju. Manja masa vozila znači i manju potrošnju energije. Pravilnim odabirom materijala, a koji će ujedno zadovoljiti svojim mehaničkim svojstvima te otpornošću na koroziju i atmosferilije, može se značajno smanjiti ukupna masa vozila. Dobar odabir su polimerni kompoziti, materijal koji zadovoljava sve kriterije i ima mogućnost projektiranja svojstva. U ovom završnom radu prikazan je jedan od postupaka izrade kompozitnih automobilskih dijelova, a u te svrhe izrađen je krovni spojler postupkom ručnog laminiranja. U kompozitu od kojeg je spojler izrađen korišteno je ojačanje staklenim vlaknima, a materijal matrice je poliesterska smola. Opisan je postupak izrade od prototipa, kalupa do gotovog proizvoda kao i korišteni materijali. The automotive industry is one of the largest industry branches in the world. Comparatively, the urgency for the replacement of conventional materials is also growing ever-larger, as the car manufacturers have to meet the strict and levied demands. The most important demand is the reduction of the exhaust of harmful gasses, which is achieved by lowering the power consumption needed to drive the vehicle. By appropriately choosing materials which simultaneously meet the required mechanical standards and offer resistance to corrosion and weather effects, the manufacturers can significantly lower the total mass of the vehicle. Such materials include polymer composites, which meet all standards and are customizable. This Bachelor thesis presents one of the processes of composite automotive part production. A roof spoiler was manually laminated and constructed for the thesis purpose. The composite used in the construction of the spoiler was reinforced with glass fibres and the material used for the matrix was polyester resin. In addition to this, the manufacturing process from the prototype, to the mould and up until the finished product, as well as the materials used are presented.

This study investigated the effect of untreated and heat-treated ash and black pine wood flour concentrations on the selected properties of high density polyethylene (HDPE) composites. HDPE and wood flour were used as thermoplastic matrix and filler, respectively. The blends of HDPE and wood fl our were compounded using single screw extruder and test samples were prepared through injection molding. Mechanical properties like tensile strength (TS), tensile modulus (TM), elongation at break (EatB), fl exural strength (FS), fl exural modulus (FM) and impact strength (IS) of manufactured composites were determined. Wood fl our concentrations have significantly increased density, FS, TM and FM and hardness of composites while reducing TS, EatB and IS. Heat-treated ash and black pine fl our reinforced HDPE composites had higher mechanical properties than untreated ones. Composites showed two main decomposition peaks; one coming from ash wood flour (353-370 °C) and black pine wood fl our (373-376 °C), the second one from HDPE degradation (469-490 °C). SEM images showed improved dispersion of heat-treated ash and black pine wood flour. The obtained results showed that both the untreated and heat-treated ash/black pine wood flour have an important potential in the manufacture of HDPE composites., U radu je opisano istraživanje utjecaja koncentracije drvnog brašna od nemodifi ciranog i toplinski modificiranog drva jasena i crnog bora na odabrana svojstva kompozita visoke gustoće na bazi polietilena (HDPE). HDPE i drvno brašno upotrijebljeni su kao termoplastična matrica i punilo. Mješavine HDPE-a i drvnog brašna pripremljene su uz pomoć ekstrudera s jednim vijkom, a ispitni su uzorci izrađeni injekcijskim prešanjem. Istraživanjem su određena mehanička svojstva proizvedenih kompozita poput vlačne čvrstoće (FS), modula elastičnosti pri vlačnom ispitivanju (FM), istezanja pri lomu (EatB), čvrstoće na svijanje (FS), modula elastičnosti pri tlačnom ispitivanju (FM) i udarne čvrstoće (IS). Koncentracije drvnog brašna značajno su povećale gustoću, tvrdoću, FS, TM i FM, a smanjile TS, EatB i IS. HDPE kompoziti ojačani drvnim brašnom od toplinski modifi ciranog drva jasena i crnog bora imali su bolja mehanička svojstva od kompozita ojačanih drvnim brašnom od nemodifi ciranog drva jasena i crnog bora. Kompoziti su pokazali dva glavna područja razgradnje: prvo, razgradnju drvnog brašna drva ariša (353 – 370 °C) i drvnog brašna drva crnog bora (373 – 376 °C) te, drugo, razgradnju HDPE-a (469 – 490 °C). SEM slike potvrdile su poboljšanu raspodjelu drvnog brašna od toplinski modifi ciranog drva jasena i crnog bora. Rezultati su pokazali da drvno brašno od nemodifi ciranoga i toplinski modifi ciranog drva jasena i crnog bora imaju velik potencijal u proizvodnji HDPE kompozita.

Polimerni kompoziti z ogljikovimi vlakni se v zadnjem obdobju ne uporabljajo samo za toge elemente, temveč tudi za fleksibilne elemente. V sklopu zaključne naloge smo izvedli analizo vpliva debeline na lastnosti in sposobnosti uporabe kompozitnega zakrilca kot deformabilen aerodinamičen element. Izdelali smo vzorce različnih debelin, ki so bili zgrajeni iz polimernega kompozita, ojačanega z ogljikovimi vlakni s postavitvijo [0 stopinj]. Uporabo zakrilc smo simulirali z dinamičnim obremenjevanjem do prednastavljenih naklonov. Na podlagi ugotovitev smo določili debelino zakrilca, ki ustreza takšnemu načinu aplikacije. Ugotovljeno je bilo, da ustrezna debelina zakrilc, obremenjenih do naklona 30 stopinj, znaša dve plasti laminata ogljikovih vlaken (0,54 mm). Carbon fiber reinforced polymer composites have recently not only been used for rigid elements, but also for flexible elements. We have performed an analysis on influence of thickness on the properties and ability to use a composite flap as a deformable aerodynamic element. We have created samples of different thicknesses, which were constructed from a carbon fiber reinforced polymer with a layout of [0 degree]. The use of flaps was simulated by dynamic loading to preset slopes. Based on the findings, we have then determined the optimal flap thickness for this application. The results have shown that the optimal thickness of flaps loaded to a slope of 30 degree is two layers of carbon fiber laminate (0.54 mm).

Tema ovog rada su polimerni kompoziti ojačani prirodnim česticama. S obzirom na ubrzan razvoj tehnologije i sve veće potrošnje sirovina prilikom proizvodnje, pronalazak obnovljive sirovine je nešto čemu treba težiti. Prirodna ojačavala su ekološki prihvatljiva alternativna sintetičkim ojačavalima zbog svoje recikličnosti, obnovljivosti i manje potrošnje energije prilikom izrade. Polimerni kompoziti ojačani prirodnim vlaknima, česticama ili drugim oblikom obnovljih sirovina imaju svijetlu budućnost među proizvodnim materijalima, a optimalan proizvod može se izraditi upotrebom i biorazgradive matrice. Cilj rada je istražiti polimerne kompozite ojačne česticama raznih biljaka i plodova, svojstva takvih kompozita te zaključiti hoće li se u budućnosti isplatiti razvijati ovakav tip kompozita kako bi se smanjilo opterećenje na okoliš. The thesis of this paper are polymer composites reinforced with natural particles. Given the accelerated development of technology and the increasing consumption of raw materials during production, the invention of renewable raw materials is something to strive for. Natural reinforcements are an environmentally friendly alternative to synthetic reinforcements due to their recyclability, renewability and lower energy consumption during manufacturing. Polymer composites reinforced with natural fibers, particles or other forms of renewable raw materials have a bright future among the production materials, and optimal products can be made not only using natural reinforcement but adding biodegradable matrices as well. The aim of this paper is to look into polymer composites reinforced with particles of various plants and fruits, the properties of such composites and to conclude whether it’s cost effective to develop this type of composites in the future in order to reduce the impact on the environment.

Unatoč činjenici da zbog svojih svojstava polimerni materijali pronalaze široku primjenu, ponekad oni ne ispunjavaju uvjete za primjenu u određenom području. Polietilen (PE) jedan je od najčešće primjenjivanih polimera zbog odličnih mehaničkih, toplinskih i optičkih svojstava te kemijske inertnosti. Svojstva različitih vrsta PE variraju, a polietilen niske gustoće (LDPE) najvažniji je materijal za proizvodnju ambalaže. Polimerni materijali, kao jedni od najšire primjenjivanih materijala modernog doba, suočavaju se s problemom osjetljivosti na UV zračenje koje uzrokuje UV degradaciju. UV degradacija se očituje promjenom kemijske i fizikalne strukture polimernog lanca čime dolazi do skraćenja uporabnog vijeka proizvoda. Dodatak UV stabilizatora polimernoj matrici može umanjiti negativan utjecaj UV zračenja ometajući i usporavajući proces degradacije. Željezovi oksidi imaju potencijal za primjenu u ulozi UV stabilizatora u polimernoj matrici. Akaganeit je željezov oksihidroksid koji pripada skupini željezovih oksida, a njegovu je sposobnost UV stabilizacije potrebno istražiti. U ovome je radu prikazan tijek provedene karakterizacije uzoraka kompozita polietilen niske gustoće/akaganeit, korištene metode karakterizacije te rezultati dobiveni istraživanjem. Despite the fact that polymer materials are widely applied because of their properties, sometimes they don't fulfill the requirements for the application in a specific field. Polyethylene (PE) is one of the most popular polymers because of its excellent mechanical, thermal and optical properties and because it is chemically inert. The properties of different types of PE are varying, whereas low density polyethylene (LDPE) is the most important material in packaging manufacturing. Polymer materials, as one of the most widely applied materials of the modern age, are facing the problem of sensitivity to UV radiation which causes UV degradation. UV degradation is manifested by the change in the chemical and physical structure of the polymer chain which causes the shortening of the product's service life. The addition of UV stabilizers to the polymer matrix can ease the negative effect of UV radiation by disturbing and slowing the process of degradation. Iron oxides have great potential for the application in the role of UV stabilizers in a polymer matrix. Akaganeite is a ferric oxyhydroxide which belongs to the group of iron oxides, and in order to know its UV stabilization properties, further research is needed. This study presents the course of the carried research of the samples of low density polyethylene/akaganeite composites, used methods of characterization and the results of the research.

Cilj ovog rada bio je utvrditi učinkovitost zaštite polietilena niske gustoće od ultraljubičastog (UV) zračenja dodatkom hematita (α-Fe2O3) i utjecaj njegovog udjela (0,5 phr, 1,0 phr i 2,0 phr) na strukturu i svojstva polimerne matrice. Uzorci su stareni u UV komori 10 dana, a nakon toga uslijedilo je analiziranje i uspoređivanje rezultata dobivenih infracrvenom spektroskopijom s Fourierovim transformacijama, termogravimetrijskom analizom i vlačnim ispitivanjima. Utvrđeno je da dodatak hematita u polimernu matricu dovodi do zaštite materijala od UV degradacije, povećanja toplinske stabilnosti, povećanja čvrstoće i smanjenja istezljivosti, a u većini slučajeva najboljim se pokazao kompozit s 1,0 phr hematita. Uzimajući u obzir dobivene rezultate i činjenicu da je hematit jeftin, lako dostupan i bezopasan za ljudsko zdravlje i okoliš, hematit bi u budućnosti mogao zamijeniti neke UV apsorbere trenutno u primjeni, stoga bi bilo potrebno provesti daljnja istraživanja i usporediti njihova svojstva. The main goal of this work was to determine the efficiency of using hematite (α-Fe2O3) to reduce the ultraviolet (UV) radiation-induced degradation of low-density polyethylene (LDPE). The work also sought to evaluate how would various concentrations of hematite (0,5 phr, 1,0 phr and 2,0 phr) affect the structure and properties of polyethylene matrix. The samples were weathered in a UV chamber for 10 days and analysed afterwards using Fourier-transform infrared spectroscopy, thermogravimetric analysis and tensile testing. It was determined that, when compared to pure polyethylene, LDPE/hematite composites exhibit lower degrees of photodegradation, greater thermal stability and tensile strength, but also somewhat reduced engineering strain. LDPE/hematite (1,0 phr) composite appears to have the best performance in most instances. Taking these findings into consideration, along with the fact that it is cheap, easily available and harmless to humans and the environment, hematite could replace some UV absorbers currently on the market. Therefore, further testing and performance comparisons may be needed in the future.

Polylactic acid (PLA) is one of the most suitable materials for 3D printing. Blending with nanoparticles improves some of its properties, broadening its application possibilities. The article presents a study of composite PLA matrix filaments with added unmodified and lignin/polymerised lignin surface-modified nanofibrillated cellulose (NFC). The influence of untreated and surface-modified NFC on morphological, mechanical, technological, infrared spectroscopic, and dynamic mechanical properties was evaluated for different groups of samples. As determined by the stereo and scanning electron microscopy, the unmodified and surface-modified NFCs with lignin and polymerised lignin were present in the form of plate-shaped agglomerates. The addition of NFC slightly reduced the filaments’ tensile strength, stretchability, and ability to absorb energy, while in contrast, the initial modulus slightly improved. By adding NFC to the PLA matrix, the bending storage modulus (E’) decreased slightly at lower temperatures, especially in the PLA samples with 3 wt% and 5 wt% NFC. When NFC was modified with lignin and polymerised lignin, an increase in E’ was noticed, especially in the glassy state.

okviru ove doktorske disertacije ispitana je mogućnosti modifikacije površine monokristala tokom sinteze optoelektronskih kompozitnih materijala s polimernom matricom kontrolisanih optičkih svojstava. Na ovaj način se poboljšava povezanost strukture kao i veza matrica-monokristal što utiče na fizičko-mehanička svojstva kompozita. Izbor materijala pao je na poli(metil-metakrilat)-PMMA kao polimernu matricu i monokristale kalcijum volframata dopiranog neodijumom (CaWO4:Nd3+ ) i kvantne tačke kadmijum selenid/cink sulfid (CdSe/ZnS). Poli(metil-metakrilat) je polimer izuzetnih optičkih svojstava i transparentan je u celoj oblasti vidljivog elektromagnetnog zračenja. Zbog toga ne bi trrebalo da utiče na optička svojstva ugrađenih monokristala. Kao modifikator površine korišćen je silan i to 3-merkaptopropil-trimetoksi-silan (MPTMS) zbog obezbeđivaja dobre transparentnosti u kompozitu. Istraživanja su izvedena u dva pravca: a) sinteza monokristalnog CaWO4:Nd3+ kao funkcionalnog nosioca u kompozitu, modifikacija površine i procesiranje laminatnog kompozita sa poli(metilmetakrilatom); b) sinteza i karakterizacija kompozita ugradnjom modifikovanih kvantnih tačaka CdSe/ZnS. Na ovako organizovan način istraživanja može se pratiti uticaj modifikacije površine monokristala na optička, termička i mehanička svojstva dobijenog kompozita. Dobijen je i karakterisan visoko kvalitetni monokristal (CaWO4:Nd3+) metodom po Čohralskom. Nakon sečenja kristala u planparalelne pločice, procesirani su laminatni kompoziti sa poli(metil-metakrilat)-om. Ugradnjom optoelektronskih čestica ili pločica u polimernu matricu menja se granična površina prelamanja elektromagnetnog zraka, sa vazduh-kristal na polimer-kristal. Modifikacijom površine čestice pojavljuje se jos jedna granična površina kristal/silan-polimer. Pored toga, optička svojstva procesiranih kompozita zavise od veličine, oblika, sadržaja i raspodele monokristalnih čestica tako da takođe treba uspostaviti korelaciju između ovih parametara. Zbog toga je tokom istraživanja ispitan uticaj modifikatora površine monokristala i na makro i na nano nivou, tj. kod laminatnog kompozita i kod nanokompozita s kvantnim tačkama. Pokazalo se da modifikacija kod 7 laminatnog kompozita ne remeti optička svojstva, dok kod nanokompozita čak i popravlja one pomeraje u spektru koji su se dogodili tokom ugradnje čestica u polimer. U svakom slučaju, termička i mehanička svojstva kompozita su bitno poboljšana, što uz održana, pa čak i poboljšana optička svojstva, dovodi do dobijanja visokokvalitenih otičkih polimernih kompozita. Within this doctoral dissertation the possibility of modification of the surface of single crystals during the synthesis of optoelectronic composite materials with a polymer matrix of controlled optical properties was examined. In this way, the connection between the structure and the matrix-single crystals bond is improved, which affects the physic-mechanical properties of the composite. Poly(methyl-methacrylate) - PMMA was used as a polymeric matrix and single crystals of neodymium doped calcium tungstate (CaWO4:Nd3+) and quantum dots cadmium-selenide/zinc-sulfide (CdSe/ZnS). Poly(methyl-methacrylate) is a polymer of exceptional optical properties and it is transparent throughout whole wavelength range of visible electromagnetic radiation. Therefore, it should not have to affect the optical properties of the embedded single crystals. 3-mercaptopropyl-trimethoxy-silane (MPTMS) was used as a surface modifier with aim to provide good transparency in the composite. The investigations were conducted in two directions: a) synthesis of single crystal CaWO4: Nd3+ as a functional carrier in the composite, surface modification and processing of laminate composite with poly (methyl methacrylate); b) synthesis and characterization of composites by incorporating modified quantum points CdSe/ZnS. In this way, the influence of modification of the surface of the single crystals on the optical, thermal and mechanical properties of the composite obtained can be monitored. A high quality single crystal of neodymium doped calcium tungstate CaWO4: Nd3+ was obtained by Czochralski method. After plating the crystals, laminate composites with poly (methyl methacrylate) were processed. By installing optoelectronic particles or sheets in the polymer matrix, the boundary surface of the electromagnetic reflection is changed, with the air-crystal on the polymer-crystal. By modifying the surface of the particle, another boundary surface of the crystal/silane polymer appears. In addition, the optical properties of processed composites depend on the size, shape, content, and distribution of single crystalline particles, so also the correlation between these parameters should also be established. Therefore, during the 9 research, the influence of the surface modifier on the surface of the single crystals was studied both at macro and nano levels, in the laminate composite and in the nanocomposite with quantum dots. It has been shown that the modification in the laminate composite does not disturb the optical properties, while in the nanocomposite it even corrects those scattering in the spectrum agreed upon during the incorporation of the particles into the polymer. In any case, the thermal and mechanical properties of the composites have been significantly improved. So, optical polymer composites of high quality with undisturbed, moreover improved optical properties were processed.

Polimerni kompoziti se v ladjedelništvu uporabljajo že dobrega pol stoletja, saj omogočajo gradnjo bolj ekonomičnih in trajnejših plovil. Kompoziti imajo mnoge prednosti ter tudi nekaj pomanjkljivosti. Ena od večjih pomanjkljivosti polimernih kompozitov je gorljivost, ki smo jo v predstavljeni nalogi testirali na izbranih materialih na podlagi standarda UL 94 – horizontalni test. Za testiranje smo izbrali dve epoksi smoli z visoko temperaturo steklastega prehoda, katerima smo dodajali zaviralec gorenja, aluminijev hidroksid. Po testiranju smo prišli do ugotovitve, da se večja koncentracija zaviralca gorenja odraža v boljši odpornosti na gorenje. Z večanjem vsebnosti aditiva smo dosegli nižjo hitrost gorenja in manjšo količino zgorelega materiala. Aditivi prav tako vplivajo na mehanske lastnosti materialov, zato smo pri proučevanih vzorcih izvedli natezni test, čigar rezultati so pokazali, da se togost in krhkost smole načeloma povečujeta z večanjem vsebnosti aditiva. Kljub izbiri materiala z visoko temperaturo steklastega prehoda in dodatku zaviralca gorenja zaenkrat pri uporabi proučevanih polimernih kompozitov še ne moremo zagotavljati enake požarne varnosti, kot jo zagotavlja jeklo. Polymer composites have been used in shipbuilding for over half a century, as they enable more economical and durable ship construction. Composites have numerous advantages, but also some disadvantages. Their biggest shortcoming is their flammability, which was tested in the presented thesis with selected material samples in accordance with the UL 94 standard - Horizontal Test. For the purpose of testing, two epoxy resins with a high glass transition temperature were chosen. A flame retardant, aluminium hydroxide, was added in various concentrations. The results showed that a higher concentration of flame retardant resulted in a slower rate of combustion and less material was burnt. Because additives affect the mechanical properties of materials, tensile tests on the chosen samples were performed. The results showed that stiffness and brittleness increase with increasing additive content. Despite choosing a material with a relatively high glass transition temperature and the addition of a flame retardant, we still cannot guarantee the same fire safety as that of steel when using the studied material composites.

Svojstvo otpornosti na UV zračenje vrlo je važno u primjeni polimernih materijala. Kako bi određeni polimer postao otporan na degradabilno djelovanje UV zračenja, dodaju se aktivne komponente (različiti antioksidansi i UV stabilizatori) koji usporavaju ili zaustavljaju proces degradacije. U ovom radu ispitivani su kompoziti na bazi polietilena niske gustoće (LDPE) u čiju su polimernu matricu dodani metalni oksidi s potencijalnim svojstvom UV blokiranja (TiO2, ZnO i SiO2) te isti metalni oksidi uz dodatak čestica srebra. Uzorci su karakterizirani FTIR spektroskopijom i termogravimetrijskom analizom. Rezultati provedenih analiza pokazali su kako je dodatak čestica metalnih oksida povećao stabilnost i otpornost na UV zračenje polietilena niske gustoće. Manja otpornost prema degradaciji kod nekih se uzoraka pripisuje aglomeraciji dodanih metalnih oksida. The ability to resist UV radiation is very important property of polymer materials in their common application. In order to improve resistance of polymer materials to the degradable UV activity, active components (various antioxidants and UV stabilizers) can be added to the polymer matrix in order to slow down or prevent process of degradation. In this work, low density polyethylene (LDPE) composites with metal oxides (TiO2, ZnO and SiO2) with potential UV blocking properties are characterized. The experiments were repeated and carried out with the same metal oxides incorporated in LDPE with the addition of silver particles. The samples were characterized by FTIR spectroscopy and thermogravimetric analysis. The results show that the addition of metal oxide particles increases stability and resistance of low density polyethylene to UV radiation. The agglomeration process of added metal oxides in some samples caused their lower resistance to UV degradation.

Znano je, da se poraba polimernih materialov iz dneva v dan povečuje. Posledično izrazito narašča tudi količina polimernih odpadkov, ki vstopajo na trg. Čim hitreje je potrebno najti pot, ki nas bo vodila do učinkovite izrabe sekundarnih polimernih surovin. To raziskovalno delo je opravljeno z namenom karakterizacije mehanskih in mikrostrukturnih lastnosti mešanic kompozitov s polimerno matico iz recikliranih polimerov v kombinaciji z različnimi polnili. V laboratoriju smo izvedli analizo ekstrudiranega materiala ter določili vpliv različnih pogojev izdelave na končno karakteristiko samega kompozita. Delo predstavlja tudi možnosti uporabe takšnega materiala in standarde, ki jih takšen kompozitni produkt mora izpolniti za uspešen prodor na trg. Raziskava je pokazala, da imajo kompozitni materiali s polimerno matico iz recikliranega polimera karakteristike, ki so povsem primerljive s karakteristikami primarnih polimernih materialov. Potrdili smo tezo, da je iz recikliranih polimernih materialov skupaj s kombinacijo različnih polnil mogoče izdelati preproste izdelke s primerljivimi ali celo izboljšanimi karakteristikami, ki so tako primerni za vsakdanjo uporabo. It is well known that the consumption of Polymeric materials is increasing day by day. Consequently, the quantity of polymeric waste which is entering the market is also rapidly increasing. In order to reduce the problem we need to find a path, that will lead us to the efficient use of secondary polymeric raw materials. This research work is carried out with the purpose of characterizing the mechanical and microstructural properties of composites based on recycled polymers with combination of various fillers. In the laboratory we have performed an analysis of the extruded material and determined the influence of the different manufacturing conditions on the final characteristic of the composite itself. The work also presents the possibilities of using such material and the standards that such a composite product must fulfill in order to be successfully implemented on today’s demanding market. The study showed that composite materials with polymer base consisting only recycled polymers have characteristics that are completely comparable to the characteristics of primary polymer materials. We have confirmed the thesis that simple products with comparable or even improved characteristics can be made by recycled polymeric materials, together with a combination of various fillers and are therefore suitable for everyday use.

Cilj ovog rada bio je karakterizirati navedene materijale: Selenis Safe FT 104 – PET 104, Selenis Safe TT 100 – PET 100 te glikolom modificirani navedeni materijali (PET-G), a zatim proizvesti filamente koji bi se koristili za proizvodnju rastaljenim filamentom. Filamente tog polimernog materijala nije bilo moguće izraditi jer ih je tijekom preradbe karakterizirala mala viskoznost te ih je kod ekstruzije gravitacija previše rastezala. Dobiveni su filamenti vrlo malih promjera koji se nisu mogli koristiti za dobivanje filamenata koji bi se koristili u 3D-ispisu kao što je bio prvotni cilj rada. Ispitivani materijali su se ponovo ekstrudirali, ovaj put uz prethodno sušenje po propisima koje je naveo proizvođač. Tako dobiveni filamenti također su išli u granulator te se vršila karakterizacija dobivenih materijala sa i bez prethodnog sušenja i utvrdilo se postoji li ikakva razlika u mehaničkim svojstvima, stabilnosti te morfologiji. Određena su mehanička i toplinska svojstva čistih komponenata i pripremljenih kompozita te polimernih mješavina. Također, ispitana je morfologija, na temelju mehaničkih svojstava odabranih uzoraka. Snimljeni su FTIR spektri i provedena je analiza površinskih svojstava mjerenjem kontaktnog kuta ispitivanih materijala. Na temelju dobivenih rezultata zaključeno je da se adekvatnim sušenjem uzoraka mijenjaju mehanička svojstva navedenih materijala. Primjenom DSC analize utvrđeno je da uzorci podvrgnuti različitim toplinskim postupcima postižu različite stupnjeve kristalnosti. FTIR spektroskopijom dobivene su karakteristične vrpce ispitivanih materijala. Proučavanjem morfologije čistih materijala i kompozita potkrijepljeni su rezultati mehaničkih ispitivanja. Provedenom analizom mjerenja kontaktnog kuta utvrđeno je da netretirani kalcijev karbonat i kalcijev karbonat tretiran stearinskom kiselinom ne utječu značajno na površinska svojstva hidrofobnosti kompozita. The objective of this study was to characterize the following materials: Selenis Safe FT 104 – PET 104, Selenis Safe TT 100 – PET 100 and glycol modified materials (PET-G). Besides the characterization, the objective was to make filaments that would be used for the fused filament fabrication. The filaments from these polymeric materials could not be made because during production they had low viscosity and were too stretched by gravity during extrusion. The obtained filaments had very small diameter that could not be used for the production of filaments used for 3D printing which was the primary objective of the study. The test materials were extruded again, this time with pre-drying according to the manufacturer's instructions. The obtained filaments were treated (processed) in granulator. The obtained materials were characterized with and without prior drying, and determined whether there was any difference in mechanical properties, stability and morphology. The mechanical and thermal properties of pure components, prepared composites and polymer blends were determined. Moreover, the morphology was examined, based on the mechanical properties of the selected samples. FTIR spectra were recorded and surface properties were analysed by measuring the contact angle of the tested materials. Based on the obtained results, the conclusion is that the mechanical properties of these materials are changing with proper drying of the samples. Using DSC analysis, it was found that samples subjected to different thermal processes achieved different degrees of crystallinity. FTIR spectroscopy obtained characteristic bands of the test materials. Examining of the morphology of pure materials and composites gave the results of mechanical testing. Conducted analysis of contact angle measurements revealed that untreated calcium carbonate and calcium carbonate treated with stearic acid did not significantly affect the surface properties of the composite hydrophobicity.

Predmet istraživanja u disertaciji su fotodielektrične osobine polimera i polimernih kompozita. U okviru disertacije prezentovane su dvije modifikovane metode dielektrične spektroskopije za određivanje površinskih i zapreminskih dielektričnih parametara polimernih kompozita. Dizajnirana je mjerna ćelija za fotodielektrična mjerenja u opsegu relativnih vlažnosti od 9% do 100%, kao i mjerna ćelija za zapreminska beskontaktna dielektrična mjerenja sa transparentnom gornjom elektrodom (staklo obloženo sa ITO). Proučavani su efekti UV-Vis zračenja, temperature, relativne vlažnosti i primjesa na dielektrične osobine polimernih materijala, kao i primjena ovih materijala u novom patentiranom tipu fotoćelije (P-2015/0529). Ispitivano je više tipova polimernih matrica: nepolarne (LDPE, iPP), polarne (PEO, PC, PBT, PVDF, PMMA) i biopolimerne matrice; kompozitni uzorci su pravljeni sa različitim fotoaktivnim puniocima (Ag, Alq3, CNT, ugljenik, ZnO, TiO2, BaTiO3, Fe3O4, Y3(Al, Ga)5O12, emodin, ferocen, fenilfosfonska kiselina) kako bi se prepoznali kompoziti sa najpodesnijim osobinama za dizajniranje nove generacije jeftinijih i efikasnijih jednoslojnih fotoćelija. U eksperimentima su korišćene živine UV lampe talasnih dužina 256 nm i 365 nm, čija je snaga zračenja 1 Wm-2 i LED lampe talasnih dužina: 620 nm; 520 nm; 440 nm i 395 nm i snage zračenja 17 Wm-2, kao i LED lampe koje daju bijelu svjetlost... The subject of research in this dissertation is photoelectric properties of polymers and polymer composites. Within the dissertation, two modified methods of dielectric spectroscopy were presented for the determination of surface and volume dielectric parameters of polymer composites. The measuring cell is designed for photodielectric measurements in relative humidity range from 9% to 100%, as well as a measuring cell for volumetric non-contact dielectric measurements with transparent top electrode (ITO coated glass). The influences of UV-Vis radiation, temperature, relative humidity and fillers on the dielectric properties of polymer materials have been researched, as well as the application of these materials in the new patented photocell type (P-2015/0529). Several types of polymer matrices were tested: nonpolar (LDPE, iPP), polar (PEO, PC, PBT, PVDF, PMMA) and biopolymer matrices; composite samples were made with various photoactive fillers (Ag, Alq3, CNT, Carbon, ZnO, TiO2, BaTiO3, Fe3O4, Y3 (Al, Ga) 5O12, emodine, ferrocene, phenylphosphonic acid) to find composites with most promising properties for designing a new generation of cheaper and more efficient single-layer photocells. In experiments were used Mercury based UV lamps with 256 nm and 365 nm wavelengths, with a radiation power of 1 Wm-2, and LED wavelengths of 620 nm; 520 nm; 440 nm and 395 nm and radiation power of 17 Wm-2, as well as white LED lamp. The irradiation power was determined using the MINI-KLA PV I-V Curve Analyzer INGENIEURBURO Mencke & Tegtmeyer...

Polimerni kompoziti s UV blokirajućim djelovanjem posebna su vrsta aktivnih polimernih materijala. UV blokiranje se postiže dodavanjem aktivnih komponenti (koje karakterizira funkcijsko svojstvo UV zaštite) u polimernu matricu. U ovom radu, pripremljeni su kompoziti na bazi polietilena niske gustoće (LDPE). Kao punilo, tj. aktivna tvar s potencijalnim svojstvom UV blokiranja, u polimernu su matricu dodani metalni oksidi (TiO2, SiO2 i ZnO) ili isti metalni oksidi uz dodatak srebra. Polimerni kompoziti pripremljeni su u Brabender gnjetilici te su zatim isprešani u folije. Tako pripremljeni uzorci karakterizirani su UV/Vis spektroskopijom, FTIR spektroskopijom, termogravimetrijskom analizom te su im ispitana mehanička i barijerna svojstva. Provedene analize pokazale su kako dodatak nanopunila poboljšava prvotna svojstva čistog polimera te ga čini prikladnim materijalom za ambalažu. Rezultati pokazuju kako dodatak nanopunila u maloj količini može postići zadovoljavajuću UV zaštitu dok dodatak srebra povećava apsorpcijsku moć metalnih oksida te tako polimerne kompozite čini još stabilnijim na UV/Vis zračenje. Polymer composites with UV blocking action are a special type of active polymer materials. UV blocking is achieved by adding active components (with a functional property of UV blocking) to the polymer matrix. In this paper, low density polyethylene (LDPE) composites are prepared. As a filler, i.e. an active substance with potential UV blocking property, metal oxides (TiO2, SiO2 and ZnO) are added to the polymer matrix, or the same metal oxides with the addition of silver. Polymer composites are prepared in Brabender plasticoder and then pressed to obtain a foil. Such prepared samples are characterized by UV/Vis spectroscopy, FTIR spectroscopy, thermogravimetric analysis and their mechanical and barrier properties were examined. The analysis has shown that the nanofiller addition improves the original properties of pure polymers and makes them suitable as packaging materials. The results show that the addition of a nanofiller in a small amount can achieve satisfactory UV protection while the addition of silver increases the absorption power of metal oxides and thus the polymer composites become more stable to UV/Vis radiation.

U ovom radu istraživan je utjecaj dodatka magnezijeva hidroksida Mg(OH) 2 na kristalnost i toplinske prijelaze (staklište, talište) poli(L-laktida) (PLLA). Magnezijev hidroksid je prethodno modificiran stearinskom kiselinom (udio stearinske kiseline 4, 6, 8%). Uzorci PLLA/Mg(OH) 2 masenih omjera 90/10, 85/15 i 80/20 pripravljeni su suhim miješanjem, a zatim ekstrudiranjem. Primjenom diferencijalne pretražne kalorimetrije određeni su toplinski prijelazi (staklište, talište), a temeljem entalpije taljenja izračunata je kristalnost PLLA. Utvrđeno je da dodatak Mg(OH) 2 uzrokuje porast staklišta PLLA, ali taj porast ne ovisi o udjelu Mg(OH) 2 i njegovoj površinskoj modifikaciji stearinskom kiselinom. Zbog porasta staklišta PLLA smanjuje se gibljivost segmenata makromolekula te se time otežava kristalizacija. Ovim mjerenjem je utvrđeno da PLLA kompoziti koji imaju veći udjel Mg(OH) 2 imaju manji stupanj kristalnosti. Izvorni PLLA ima talište koje karakterizira jedan pik, dok PLLA u kompozitu ima dva pika taljenja. In this thesis the influence of adding magnesium hydroxide Mg(OH) 2 to the poly (L-lactide) (PLLA) thermal transitions (glass transition, T g and melting temperature, T m ) was investigated. Magnesium hydroxide was previously modified with stearic acid (the fraction of stearic acid was 4, 6, 8 %). Samples of PLLA/Mg(OH) 2 with mass fraction 90/10, 85/15 and 80/20 were prepared by dry mixing and then by extrusion. Using differential scanning calorimetry, the glass transition and melting point temperatures as well as the PLLA crystallinity were determined. It was found that the addition of Mg(OH) 2 causes an increase in PLLA T g , but this increase does not depend on the fraction of Mg(OH) 2 and its surface modification with stearic acid. Due to the increase of T g , the macromolecular motionsare reduced, making it more difficult to crystallize. By this measurement, it was found that PLLA in composites having a higher content of Mg(OH) 2 have a lower degree of crystallinity. The original PLLA has a melting point characterized by one peak, while the PLLA in the composite has two melting peaks.

Kompozitni materijali su relativno nova vrsta materijala vrlo popularna zbog svojih iznimnih svojstava. Najzastupljeniji postupci proizvodnje rezultiraju izradcima koji zahtjevaju relativno malo dodatne obrade uz iznimku postupka obrade odvajanjem čestica tj. bušenje. Prilikom izrade provrta kod određenih tipova kompozita dolazi do raslojavanja (delaminacije) slojeva u kompozitu što nepovoljno utječe na mehanička i druga svojstva kompozita. U ovom završnom radu su obrađeni podaci dobiveni bušenjem provrta u polimernom kompozitu sa staklenim vlaknima te je zatim izrađena programska podrška za neuronsku mrežu koja na osnovu mjerenih značajki sila te parametara obrade klasificira stupanj delaminacije. Composite materials are a relatively new type of material which is very popular due to their extraordinary properties. The most common procedures of manufacturing result in products that require relatively little additional machining with the exception of drilling. Delamination occurs during hole drilling in certain types of composites which negatively impacts the mechanical and other properties. Data collected during drilling of holes in polymer composites with glass fibers reinforcement was processed in this undergraduate thesis and then program support for a neural network was developed. The neural network will classify the resulting delamination from measured forces and the parameters of drilling

Jedna od posebnih vrsta aktivnih polimernih materijala su polimerni kompoziti s UV blokirajućim djelovanjem. Da bi se postiglo UV blokiranje, potrebno je u polimernu matricu dodati aktivne komponente koje karakterizira funkcijsko svojstvo UV zaštite. U ovom radu, pripremljeni su kompoziti na bazi polietilena niske gustoće (LDPE) s punilom, tj. aktivnom tvari s potencijalnim svojstvom UV blokiranja. Kao punilo u polimernu matricu dodani su metalni oksidi (TiO2, ZnO i SiO2) ili isti metalni oksidi uz dodatak srebra. Polimerni kompoziti pripremljeni su u Brabender gnjetilici te su zatim isprešani u folije kako bi se provela karakterizacija uzoraka. Tako pripremljeni uzorci karakterizirani su FTIR spektroskopijom, termogravimetrijskom analizom, UV/Vis spektroskopijom te su im ispitana barijerna i mehanička svojstva. Provedene analize pokazale su kako dodatkom punila dolazi do poboljšanja prvotnih svojstava čistog polimera te ga čini prikladnim materijalom za ambalažu. Rezultati pokazuju da se dodatkom punila i u maloj količini može postići zadovoljavajuća UV zaštita. Dodatak srebra povećava apsorpcijsku moć metalnih oksida, a samim time polimerne kompozite čini još stabilnijim na UV/Vis zračenje.

U ovom radu analizirana je konstrukcija HALE (High Altitude Long Endurance) bespilotnih letjelica te materijali koji se koriste za njihovu izradu. Uvodni dio opisuje prošlost bespilotnih letjelica te kada je počela upotreba HALE letjelica. Dalje su opisani polimerni kompoziti s vlaknima, čija je uloga značajna kod izrade krila HALE letjelica te njihova svojstva. U eksperimentalnom dijelu rada izrađeni su polimerni kompoziti kojima su ispitana mehanička svojstva. Na temelju ispitanih mehaničkih svojstava donesen je zaključak. In this study, the structure of HALE (Long Altitude Long Endurance) unmanned aerial vehicles and materials used for their construction was analyzed. Introduction part describes the history of unmanned aerial vehicles and the time when use of HALE aircraft began. Further, fiber-reinforced polymers and their properties are described, whose role is significant in the design of the HALE wing structure. In the experimental part, polymeric composites with fibres were made and tested for mechanical properties. Based on the examined mechanical properties, a conclusion was made.

Kompozitni materijali danas se sve više razvijaju i primjenjuju u različitim industrijama zbog svojih mnogobrojnih prednosti. Automobilska industrija jedna je od velikih potrošača polimernih kompozita zbog toga što uz dobra mehanička svojstva imaju i malu masu što pozitivno utječe na ukupno smanjenje mase vozila i bolju iskoristivost goriva. Polimerni kompoziti zadovoljavaju potrebne zahtjeve u automobilskoj industriji kao što su trajnost, čvrstoća, krutost, postojanost prema koroziji, mogućnost apsorpcije energije, smanjenje vibracija i buke. Od polimernih se kompozita, kao zamjena za konvencionalne materijale, izrađuje automobilski branik koji ima važnu ulogu pri naletu automobila na neku prepreku ili pješaka. Uloga branika je da mora što bolje apsorbirati energiju udara kako ne bi došlo do oštećenja ostalih dijelova automobila, putnika i pješaka. U radu je prikazana uloga branika u automobilima, opisani materijali i postupci prerade za proizvodnju kompozitnog branika. U eksperimentalnom dijelu rada izrađene su ispitne kompozitne ploče od različitih vrsta vlakana i smola. Provedeno je ispitivanje sile udarca na ispitne ploče primjenom dodatnog apsorbirajućeg materijala od polimerne pjene. Svrha ovog rada je ispitati kako primjena različitih kompozitnih tvorevina s različitim debljinama i gustoćama dodatnog apsorbirajućeg materijala utječe na apsorpciju udara. Composite materials are increasingly being developed and applied in different industries due to their many advantages. The auto industry is one of the major users of polymer composites because of their good mechanical properties along with a small mass that has a positive impact on total vehicle weight reduction and better fuel economy. Polymer composites meet the demands of the auto industry such as durability, strength, stiffness, corrosion resistance, energy absorption, vibration and noise reduction. Polymer composites, as a substitute for conventional materials, make a car bumper that plays an important role during car crashes with some obstacle or pedestrians. The bumper's role is that it has to absorb the shock energy more efficiently so as not to damage other parts of the car, the passengers or the pedestrians. This thesis shows the role of bumper in cars, and the materials and processes for the production of a composite bumper are described. In the experimental part, test composite plates of different types of fibers and resins were made. Testing of the impact force on the test plates was conducted using an additional polymer foam absorbing material. The purpose of this thesis is to examine how the usage of different composite structures of different additional absorbent material thicknesses and densities affects the absorption of the impact.

Polimerni kompozitni materiali so eni izmed najbolj razširjenih materialov v industriji in v splošni uporabi. V sklopu zaključne naloge bomo merili vpliv različnih tehnoloških postopkov izdelave in orientacije vlaken na splošne mehanske lastnosti materiala ter njihov vpliv na viskoelastične lastnosti smole. Šest različnih polimernih kompozitnih vzorcev ojačanih z ogljikovimi vlakni bomo preizkušali na štiri-točkovnem upogibnem testu. Trije vzorci so bili izdelani po postopku ročne mokre lamincaije z vakuumeranjem ter z [0°]8, [(45°/0°)2]s in [±45°]8 orientacijo vlaken. Drugi trije vzorci pa so bili izdelani po postopku avtoklave s pred-impregniranimi vlakni z isto orientacijo vlaken. Rezultati, pridobljeni z eksperimentalnimi meritvami kažejo, da imata tehnološki postopek izdelave in orientacija vlaken vpliv na mehanske in viskoelastične lastnosti materiala. Polymer composites are one of the most common materials in the use of industry and in everyday use. We measured influence of the orientation of the reinforcement in the composite made by two different technological methods of fabrication. In addition, how this effects viscoelastic behaviour of the material. Six different polymer composite samples reinforced by carbon fibres were studied in the four-point bend test. Three of the samples were made by the process of hand lay-up with vacuum bagging and the [0°]8, [(45°/0°)2]s and [±45°]8 orientation of the fibres. The other three samples were made by the autoclave method with pre-impregnated fibre with the same orientation of the fibres. The results have showed us that the technological methods of fabrication and the orientation of reinforcement have influenced on the mechanical properties of material as well as on viscoelastic behaviour of material.

The incorporation of magnetic barium hexaferrite nanoparticles in a transparent polymer matrix of poly(methyl methacrylate) (PMMA) is reported for the first time. The barium hexaferrite nanoplatelets doped with Sc3+, i.e., BaSc0.5Fe11.5O12 (BaHF), having diameters in the range 20 to 130 nm and thicknesses of approximately 5 nm, are synthesized hydrothermally and stabilized in 1-butanol with dodecylbenzenesulfonic acid. This method enables the preparation of monolithic nanocomposites by admixing the BaHF suspension into a liquid monomer, followed by in-situ, bulk free-radical polymerization. The PMMA retains its transparency for loadings of BaHF nanoparticles up to 0.27 wt.%, meaning that magnetically and optically anisotropic, monolithic nanocomposites can be synthesized when the polymerization is carried out in a magnetic field. The excellent dispersion of the magnetic nanoparticles, coupled with a reasonable control over the magnetic properties achieved in this investigation, is encouraging for the magneto-optical applications of these materials.

Tema završnog rada su prirodna vlakna u industriji polimernih kompozita. Tema daje uvid u mogućnosti primjene prirodnih vlakana u polimernim kompozitima, njihove prednosti i nedostatke. Navode se biljke koje su najprikladnije za takvu primjenu od kojih su izdvojene: bambus, banana, lan i industrijska konoplja. Za svaku od ovih biljaka prikazana je njihova primjena i mehanička svojstva. Dissertation is about natural fibers in polymer composites industry. The theme gives insight into the possibilities of using natural fibers in polymer composites, their advantages and disadvantages. It names the plants that are the most convenient for such applications of which are distinguished: bamboo, banana, flax and industrial hemp. For each of these plants an insight into their use and their mechanical properties is given.

Kompozitni materijali danas predstavljaju najmodernije materijale kao alternativa konvencionalnim konstrukcijskim materijalima. Posjeduju iznimno dobra mehanička svojstva kao što su visoka specifična čvrstoća i specifična krutost. Iz tog razloga sve se više koriste u područjima sporta, pa se od njih izrađuju oplate natjecateljskih motocikala. Kriteriji koji se postavljaju na materijal oplate iznimno su visoki pa materijali koji se koriste moraju imati najbolja svojstva. U radu su opisani materijali i tehnologije korištene u proizvodnji dijelova oplate natjecateljskih motocikala. U eksperimentalnom dijelu rada izrađeni su ispitni uzorci polimernih kompozitnih materijala ojačanih različitim ojačanjima. Svrha ovog rada je upoznavanje tehnologija izrade suvremenih kompozitnih materijala i određivanje utjecaja različitih vrsta ojačanja na mehanička svojstava polimernih kompozita. Composite materials represent the current state of the art materials which serve as an alternative to conventional construction materials. They have great mechanical properties such as the high tensile strength and specific stiffness. Therefore, their application in different sports is increasing. This is also true for motorcycle racing where most of the bodyworks are made out of composite materials. Requirement levels are set high so the materials in use need to have the best possible properties. In this thesis the materials and production techniques used in producing racing motorcycle bodyworks are presented. Within the experimental part of the thesis test samples reinforced with different kind s of reinforcement materials have been made. The purpose of the thesis is to study the composite materials production processes and to determine the influence of the applied reinforcement on the mechanical properties of the polymer composite materials.

U završnom radu ukratko je opisana povijest kompozitnih materijala, te njihova podjela prema vrsti matrice i prema vrsti ojačavala. Ukratko su opisana svojstva pojedinih vrsta kompozita. U drugom dijelu su prikazani primjeri upotrebe kompozitnih materijala u sportovima na vodi. Opisane su vrste materijala koje se primjenjuju za proizvodnju polimernih kompozita u izradi opreme za primjenu u; natjecateljskom plivanju, sportskom ribolovu, surfanju na vodi i utrkama čamaca. Opisana su svojstva koja ti polimerni kompoziti imaju i koja su važna za njihovu upotrebu u sportovima na vodi. This paper shortly describes the histoy of composite materials and their categorization in terms of type of material used for matrix and type of reinforcement. Properties of certain types of composite materials are described. The second part gives examples of application of polymer composites in water sports. In the paper it is described types of polymer composites used in equipment for use in competitive swimming, sport fishing, surfing and boat racing. It is also described properties of polymer composite, which are important for their application in water sports.

In this work composite materials of improved properties based on styrene and methacrylate copolymers with differently functionalized multiwalled carbon nanotubes (CNT) were prepared. In order to obtain a fine dispersion and to enhance the interfacial interaction of CNT with surrounding polimer matrix a chemical modification of the surface of carbon nanotubes was performed. Various types of functionalized multiwall carbon nanotubes were used: oxidized (CNT-COOH) and their ester analogues (methyl, dodecyl and ethylbenzene). The reaction of covalent functionalization of CNT-COOH with NaOH and further with (2-bromethyl)-benzene and hexadecyl-trimethylammonium bromide into CNT-COOEtBz was successfully performed. Also, oxidized multiwall carbon nanotubes were reacted with thionyl chloride and further in esterification reaction with given alcohols transformed into corresponding methyl or n-dodecyl ester. Functionalization of CNTs was confirmed by FTIR, Raman and X-ray photoelectron spectroscopy as well as by thermogravimetric analysis. Dodecyl and ethylbenzene ester modified carbon nanotubes showed contact angle for water 150 and 141 degrees, while the oxidized and methyl ester modified carbon nanotubes displayed seepage. Dispersibility of all modified carbon nanotubes in methanol and toluene was quantified by UV-Vis spectroscopy and differs considerably in both solvents for all systems, due to the significant change in chemistry of surface of CNTs. Mixtures of styrene / methacrylate monomer with up to 1 wt. % of CNT in toluene were reacted in a radical in-situ polymerization reaction. The synthesized composites were characterized by the SEC, TGA, DSC, DMA, SEM and contact angle method. The improvement of the properties of polymer/CNT composite can be attributed to better interaction between nanotubes and the polymer matrix.

U završnom radu ukratko je opisana povijest automobila i polimernih kompozita. Prikazane su svojstva i vrste matrica i ojačavala polimernih kompozita koji se upotrebljavaju u automobilskoj industriji. Obrađeni su i postupci izrade kompozita te detaljnija primjena razvrstana po segmentima automobila. U zadnjem je dijelu ukazano na zahtjeve koji se postavljaju na materijale te nove trendove na tom području.

Krčenje polimernih kompozitov med strjevanjem, kljub stalnemu napredku in razvoju, še vedno povzroča težave v dentalni medicini. Skrček je odvisen predvsem od sestave matice, a delno lahko nanj vpliva tudi način polimerizacije t.j. jakost svetlobnega toka in čas potreben za polimerizacijo kompozitov. Polimerizacijske lučke v dentalni medicini imajo večinoma dvajset sekundni interval polimerizacije. Lučka Flashmax P3 podjetja CMS potrebuje za polimerizacijo kompozitov le tri sekunde in je novost na trgu. Njen vpliv na skrček med polimerizacijo kompozitov še ni bil raziskan. Podjetje Drevenšek & Drevenšek d.o.o. je zastopnik za lučko FlashMax P3 v Sloveniji in je pokazalo zanimanje za takšno raziskavo. Narejena je primerjalna raziskava vpliva lučke FlashMax P3 in lučke Radii Plus podjetja SDI na polimerne kompozite Ice in Glacier podjetja SDI, Gradia podjetja GC in Charisma podjetja Heraeus Kulzer. Vse naštete produkte je priskrbelo podjetje Drevenšek & Drevenšek d.o.o., saj so želeli s podrobno raziskavo izdelkov in storitev, ki jih ponujajo, potrditi njihovo odličnost in neoporečnost. Namen in cilj diplomske naloge je jasno pokazati vpliv vrste polimerizacijskih lučk in časov zamreženja na skrček polimernih kompozitov. Za dokazovanje so uporabljene tri različne metode in sicer metoda prostega krčenja polimernih kompozitov v jeklenih cevkah, metoda vezanega krčenja polimernih kompozitov v zobeh in metoda izvleka oziroma »pull-out« metoda. Shrinkage of polymer composites during polymerisation, despite ongoing progress and development, continues to cause problems in dental medicine. Shrinkage depends mainly on the resin composition, but partialy it is also affected by the method of polymerization, meaning luminous intensity and time required for curing composites. Polymerization lights in dental medicine mostly have twenty-second curing interval. LED light FlashMax P3 from the compay CMS is new on the market and needs only three seconds for curing of the composites. Its impact on the polymerization shrinkage of composites has not yet been studied. The company Drevenšek & Drevenšek d.o.o. is the Slovenian representative for light FlashMax P3 and has shown interest in such a study. We made a comparative study of impact made by Flashmax P3 light from CMS and Radii Plus light from SDI on polymer composites Ice and Glacier – SDI company, Gradia – GC company and Charisma – Heraeus Kulzer company. All of these products had been provided by Drevenšek & Drevenšek d.o.o. because they required a detailed survey of those products to confirm the excellence and integrity of the products and services they offer. The purpose and aim of this thesis is to clearly show the influence of the type of polymerization lights and curing time on the shrinkage of polymer composites. We used three different methods to demonstrate it: the method of free shrinkage of polymer composites in steel tubes, method of bonded shrinkage of polymer composites in teeth and pull-out method.

U svrhu ispitivanja utjecaja udjela i raspodjele punila u polimernoj matrici na toplinska svojstva HIPS/EVA kompozita (polistiren visoke gustoće/etilen-vinil-acetat), pripremljeni su kompoziti na dvopužnom ekstruderu. Uzorcima je dodano mikropunilo aluminijev hidroksid i nanopunilo silika. Toplinska svojstva dobivenih kompozita određena su termogravimetrijskom analizom (TGA) gdje su određene temperature početka razgradnje (T90), temperature maksimalne brzine razgradnje (Tmax) te ugljenizirani ostatak. Morfologija pripemljenih kompozita određena je skenirajućom elektronskom mikroskopijom (SEM). Rezultati su pokazali da uzorci pripremljeni s nižim udjelom nanopunila imaju bolju toplinsku postojanost od uzoraka s većim udjelom kod kojih dolazi do agregiranja čestica. Nadalje, površina kompozita pripremljenih s aluminijevim hidroksidom je gruba i stvara zasebne domene zbog nastajanja agregata što je posljedica slabe povezanosti punila s polimernom matricom. Disperzija nanopunila je homogenija u odnosu na disperziju mikropunila, a to je posebno vidljivo kod nižih koncentracija nanopunila dok je kod uzoraka s većim udjelom nanopunila primjećena pojava agregata.

Cilj istraživanja je uspoređivanje odnosa između strukture i svojstava hibridnih ternarnih kompozita polipropilen/silika/elastomer s binarnim polipropilen/silika kompozitima i polipropilen/elastomer mješavinama te s čistim komponentama. Izotaktni polipropilen modificiran je s četiri vrste silike (mikro/nanosilika, površinski obrađena/neobrađena silika) te s četiri vrste elastomera (stirenski blok-kopolimeri te metalocenski kopolimeri polipropilena) koji se dodaju istovremeno kao kompatibilizatori i modifikatori žilavosti, s ciljem poboljšanja žilavosti i slabe interaktivnosti na međupovršini iPP-silika. Istraživanja morfologije različitim vrstama mikroskopija te studij fazne strukture, transformacije, orijentacije kristalita i čestica te stupnja kristalnosti metodom rentgenske difrakcije pokazala su da dodatak silike i elastomera utječe na restrukturiranje iPP matrice (kao dispergirane čestice, nukleatori i kao modifikatori viskoznosti taline i različitih utjecaja za vrijeme solidifikacije matrice). Istraživanja mehaničkih svojstava su pokazala da, osim konstituenata i interakcija među njima, restrukturirana matrica izotaktnog polipropilena utječe na mehanička svojstva binarnih kompozita, mješavina te hibridnih ternarnih kompozita. Studij interakcija u mješavinama i kompozitima, mjerenjem kontaktnog kuta i računanjem interakcijskog parametra B, pokazao je da međudjelovanje između komponenata u sustavu ima ključnu ulogu u određivanju konačnih svojstava mješavina i kompozita. Optimalna adhezija u mješavinama te kompozitima, odnosno interaktivnost između matrice i komponenata te međudjelovanje između punila i elastomera rezultira optimalnim mehaničkim svojstvima, posebno svojstvima udarne žilavosti.

U poglavljima završnog rada obrađena je tema poliesterskih laminata ojačanih staklenim vlaknima. Uvodni dio rada odnosi se na osnovne podatke o kompozitnim materijalima, njihovoj primjeni i svojstvima te postupcima njihova oblikovanja, s težištem na ručni i "RTM" postupak istiskivanja mjehurića zraka. Težište rada je stavljeno na izradu uzoraka i eksperimentalno ispitivanje uzoraka. Rezultati ispitivanja su iskorišteni za analizu sa ciljem međusobne usporedbe uzoraka i određivanje moguće primjene poliesterskih laminata od kojih su uzorci izrađeni. Sveukupno, prvim radom došlo se do spoznaje da su poliesterski laminati ojačani staklenim vlaknima kvalitetan i pristupačan materijal koji opravdano ima široku i raznovrsnu primjenu.