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In recent years, composite materials such as carbon-fibre-reinforced plastic (CFRP) have been widely used in medical devices, industries, marine and aerospace applications due to their high resistance-to-weight ratio toughness, corrosion resistance, and other novel properties. The machining of these composite materials using conventional machines results in poor precision and surface finishing due to excess heat generation at the tool-material contact zone. The drawbacks of the conventional machining process can be overcome with the adoption of a novel cutting technique using pressurized water, which can dissipate the heat generated by the impact of abrasive particles against the material in order to eliminate the poor precision and surface finishing caused by overheating. In this experimental study, the performance of surface quality (roughness and kerf angle) of CFRP machining using an abrasive water jet technique has been studied for a wide range of cutting parameters, such as water pressure and cutting speed.

Polimerni materiali so s pospešenim razvojem tehnologije in industrije v zadnjih letih pridobili pomemben status v našem vsakdanjem življenju. Kljub mnogim prednostim, ki jih prinašajo polimerni materiali (nizka gostota, visoka trdnost, prikladnost večstranske uporabe...), predstavljajo veliko grožnjo našemu ekosistemu. Kot odpadek predstavljajo velik izziv, saj je pred postopki njihove razgradnje potrebno nadzorovano ravnanje z odpadkom (sortiranje). S tem razlogom je v zadnjem času moč zaznati razvoj na področju iskanja trajnostnih rešitev uporabe polimernih materialov v zunanjem okolju. V diplomski nalogi sem opisal dva pristopa, ki stremita k tem rešitvam. Prvi pristop temelji na kompozitnih materialih, ki so sestavljeni iz dveh ali več komponent, katere so izbrane na podlagi individualnih lastnosti, za katere želimo, da se ohranijo oziroma izrazijo v novonastalem kompozitu. Z ustrezno sestavo in procesom izdelave kompozita ima ta izboljšano zmogljivost oziroma boljšo funkcionalnost od individualnih osnovnih komponent. Drugi pristop, ki sem ga predstavil je samoceljenje polimernih materialov. Samoceljenje je lastnost nekaterih pametnih materialov, za katere je značilno, da se odzivajo na zunanje dražljaje. Material s sposobnostjo samoceljenja lahko definiramo kot material, ki ob nastali poškodbi takoj in avtonomno obnovi poškodovano mesto. Oba pristopa sta osredotočena na podaljševanje življenjske dobe polimernih materialov. S tem se v praksi izognemo raznim okvaram, popravilom in menjavi delov ter s tem zagotovimo trajnost produkta na področjih, kjer je to pomembno. V sklopu svojega diplomskega dela sem princip obeh pristopov povzel na primeru izdelave ter praktične uporabe specifičnega polimernega materiala s sposobnostjo samoceljenja, ki je ojačan z ogljikovimi vlakni (CFRP). With recent rapid development of technology and industry, polymeric materials have gained an important status in our everyday life. Despite many advantages, that polymeric materials are providing (low density, high strength, suitability of multilateral use…), they represent a significant threat to our ecosystem. As a form of waste, they represent a great challenge because the procedures of their decomposition demand controlled waste management (sorting). For that reason, it is possible to detect recent developments in the search for sustainable solutions in the field of polymeric materials applied in external environment. In my thesis I described two approaches, that strive for these solutions. The first approach is based on composite materials, that are composed of two or more components, which are selected on the basis of individual properties that we want to preserve or express in the newly formed composite. With the appropriate composition and manufacturing process of the composite, the performance and functionality of individual basic components are improved. The second approach I presented is self-healing of polymeric materials. Self-healing is a property of some smart materials, for which it is typical to respond to external stimuli. Material with the ability of self-healing can be defined as a material that with the occurrence of an injury, immediately and autonomously restores the damaged area. Both approaches are focused on the extension of longevity of polymeric materials. In practice, this allows us to avoid various defects, repairs and replacements of parts, thus ensuring the durability of the product in areas where it is of importance. Within my thesis, I have summarized the principle of both approaches with an example of manufacture and practical use of a specific polymeric material with self-healing ability, reinforced with carbon fiber (CFRP).

Grafen je enoslojna oblika grafita povezana z sp2 hibridiziranimi ogljikovimi atomi v heksagonalno kristalno strukturo. Grafenski nanotrakovi so trakovi grafena, ki imajo visoko razmerje med dolžino in širino in so sestavljeni iz ene ali več plasti grafena. Imajo kvazi 1D strukturo ter zanimive lastnosti – drugačne od grafena. Kljub debelini največ nekaj atomov, je eden izmed najtrših materialov, ki je hkrati odličen toplotni in električni prevodnik. Zaradi teh unikatnih lastnosti potekajo številne raziskave na področju izboljšanja mehanskih, toplotnih in električnih lastnosti materialov. Ena od možnih aplikacij grafenskih nanotrakov je izboljšanje mehanskih lastnosti kompozitnih materialov. Problem pri uporabi se pojavlja pri dispergiranju grafenskih nanotrakov v epoksi smolo, ki predstavlja ključen korak pri izdelavi kompozitnih materialov. S postopkom funkcionalizacije lahko modificiramo grafenske nanotrakove tako, da bo dispergiranje veliko učinkovitejše. S tem namenom sem v svojem magistrskem delu sintetiziral nefunkcionalizirane grafenske nanotrakove ter z epiklorohidrinom funkcionalizirane grafenske nanotrakove. Sledilo je dispergiranje pripravljenih nanotrakov v epoksi smolo ter izdelava kompozitnih materialov. S pomočjo karakterizacijskih metod sem ugotavljal uspešnost sinteze in funkcionalizacije, z mehanskimi meritvami pa ugotavljal, ali dodajanje grafenskih nanotrakov izboljša mehanske lastnosti kompozitnih materialov. Graphene in a single-layer form of graphite with sp2 hybridized carbon atoms bonded in hexagonal crystalline structure. Graphene nanoribbons are strips with high aspect ratio and may consist of one or more layers of graphene. They have a quasi 1D structure and possess additional interesting properties compared to graphene. Despite its thickness of just a few atoms, it is one of the most durable materials with excellent thermal and electrical properties. Because of these unique properties, many studies are underway to improve the mechanical, thermal and electrical properties of materials. One of the possible applications of graphene nanoribbons is the improvement the mechanical properties of composite materials. However, dispersibility of graphene nanoribbons into epoxy resin, which is a key step in the manufacture of composite materials, represents a barrier in application. Through the functionalization process graphene nanoribbons can be modified to enhance dispersibility. Herein, I synthesized non-functionalized graphene nanoribbons and graphene nanoribbons functionalized with epichlorohydrin. This was followed by the dispersion of the prepared nanoribbons into epoxy resin and the production of composite materials. The characterization methods were used to determine the yield of synthesis and degree of functionalization. Further, the mechanical measurements were done to determine mechanical properties of graphene based nanocomposite materials.

V diplomski nalogi je predstavljeno načrtovanje laminatnega materiala in določevanje materialnih lastnosti. Temo sem si izbral zato, da prikažem del postopka razvijanja šasije pri Formuli Študent. Osrednji področji naloge sta določitev laminacije materiala s pomočjo numerične analize in primerjava med numeričnim in realnim preizkusom na preizkuševalnim stroju. V prvih poglavjih so predstavljeni in opisani pojmi, s katerimi se srečamo v nalogi. Drugi del pa se posveti simulaciji in preizkusom. In my diploma thesis I presented the planning of laminate material and gathering material properties. The theme was chosen to show part of the process of developing chassis at Formula Student. The two main subjects are determination of lamination of the material with the help of numerical analysis and a comparism between the numerical and real test. In the first chapter are represented and described concepts, which we encounter in the assignment. The second part focuses on simulation and test.

Diplomsko delo opisuje razvoj delov športnega avtomobila, ki jih izdelamo s pomočjo kompozitnih materialov. Predmet obravnave diplomskega dela so izbrane komponente za športni avtomobil – TUSEK TS 900 APEX. Predstavljeni so kompozitni materiali, njihove lastnosti ter postopek izdelave strehe avtomobila. Prikazani so posamezni koraki snovanja načrta za izdelavo kalupa, nato pa tudi postopek dela, kako iz epoksidne smole in steklenih ter ogljikovih tkanin izdelamo streho. Diploma work represents engineering details of developing different parts of sport car, which are made of composite materials. The subject of the hearing thesis is dealing with the sport cat – TUSEK TS 900 APEX. Presented are the composite materials, their characteristics and the manufacturing process of the sport car roof. Shown are the individual steps from the designed plan to produstion of the mold, the whole process of work – how the roof is made of epoxy resin, glass and carbon fibres.

Diplomsko delo obravnava proizvodnjo izdelkov iz kompozitnih materialov v podjetju Trixy Aviation d.o.o.. Osredotočeno je na proces ročne laminacije z zračnim mehurjem in njegovo optmizacijo. Eksperimentalni del je sestavljen iz treh poskusov pri katerih se tlaki in časi med napenjanjem mehurja razlikujejo. Cilj naloge je pridobiti izdelek s čim manjšo maso in kvalitetno površino, ki bo ustrezal strogim standardom letalske industrije. The following diploma work studies products built out of composite materials and their manufacturing at Trixy Aviation d.o.o. company. Its main focus is on bladder moulding process optimisation. The experimental part consists of three diverse experiments in which amounts of pressure and time period between bladder tensions differ. The main goal of this work is to achieve a product that has the lowest possible mass and quality surface while still meeting the aviation industry`s strict standards.

V magistrski nalogi je predstavljen postopek določitve materialnih podatkov kompozitnega materiala, izdelanega z različnimi tehnologijami in z uporabo različnih ojačitvenih faz. Predstavljene so osnove kompozitnih materialov, ASTM-standard, natezni preizkus, analitični pristop, s katerim so primerjani rezultati nateznega preizkusa, ter numerična simulacija tlačne posode, kjer je z numerično analizo določena razporeditev slojev za dosego optimalne trdnosti in primerjana z uporabo kovinskih materialov. The master's thesis presents a determination process of material data of composite materials which are made with different technologies and using various reinforcement phases. Basics of composite materials, ASTM standard and tensile test are presented in this work, including analytical approach which is compared with results from tensile tests. Numerical simulation of the pressure vessel is used to determine composite layers for optimal strength and compared with use of metal materials.

Anizotropno trenje ima ključno vlogo pri procesu preoblikovanja polizdelkov iz ogljikovih vlaken. Ta kompleksni pojav otežuje načrtovanje preoblikovalnih orodij in določanje procesnih parametrov. Pri tem si lahko pomagamo s pomočjo numeričnih simulacij na osnovi metode končnih elementov. Da bi natančno napovedali proces preoblikovanja je v simulacijo kontakta med posameznimi plastmi ogljikovih vlaken potrebno vključiti model anizotopnega trenja. V magistrskem delu sta predstavljena dva postopka simuliranja anizotropnega trenja z metodo končnih elementov v programskem okolju Abaqus. Prvi od modelov (M1) je standardno vključen v Abaqus okolje in ponuja eliptično razporeditev tornih sil glede na smer gibanja in usmeritev ploskev. Drugi model (M2) je del uporabniškega podprograma, ki je bil razvit v sodelovanju z razvijalci programa Abaqus in uporablja eksperimentalno določene vrednosti koeficientov trenja, ki jih uporabnik določi v obliki diskretnih vrednosti relativnih usmerjenosti ploskev v kontaktu. Da bi zagotovili pravilno delovanje simulacij je potrebno validirati osnovne modele, ki v simulacijah popisujejo kontakt dveh teles. V ta namen so simulacije v okviru magistrskega dela izvedene na preprostih geometrijah togih teles v obliki ravnih ploskev, ki ne vključujejo materialnih lastnosti. Na ta način zagotovimo opazovanje le kontaktnih modelov brez učinkov mehanskih modelov materiala. Prve simulacije vključujejo le obremenitve v smeri normal ploskev, brez relativnih premikov med ploskvama. Pri teh simulacijah smo opazili napačno razporeditev kontaktnega tlaka, ki se pojavlja pri določenih nastavitvah kontaktnega algoritma. Ker so torne sile neposredno povezane s tlakom na kontaktni površini smo v naslednjem svežnju simulacij ocenjevali vpliv napačne tlačne porazdelitve na ravnovesje sil in momentov v telesih. Opazili smo, da pri določenih nastavitvah prihaja do pojava vrtilnih momentov, ki niso v skladu s teorijo anizotropije trenja ter eksperimentalnimi rezultati. Na podlagi prvih simulacij smo izluščili najbolj primerne nastavitve za simulacijo trenja med dvema ploskvama. Z nadaljnimi simulacijami smo testirali delovanje modela M1 in ocenili zmožnost da popiše anizotropne lastnosti polizdelkov iz ogljikovih vlaken. V ta nemen smo rezultate iz numeričnih simulacij smo primerjali z rezulati eksperimentov trenja med posameznimi plastmi ogljikovih vlaken. Ugotovili smo, da standardni model M1, ki predvideva eliptično porazdelitev tornih sil ne zadošča za modeliranje omenjenih lastnosti zaradi monotonosti eliptične funkcije. Vzporedno smo predstavili zasnovo uporabniškega podprograma (M2) in testirali njegove osnovne funkcije. Ugotovili smo, da v trenutni obliki uporabniški podprogram omogoča natančno simuliranje tornih sil za kombinacije usmeritev materiala in smeri gibanja za katere lahko neposredno določimo koeficiente trenja. Za simuliranje celotnega spektra kombinacij, kjer je potrebna interpolacija med posameznimi vrednostmi koeficientov, pa so potrebna nadaljna testiranja in razvoj algoritma. Rezultat magistrske naloge je uporabniški podprogram, ki predstavlja osnovo za nadaljni razvoj ter omogoča razširitev modela anizotropnega trenja z drugimi parametri v postopku preoblikovanja ogljikovih vlaken kot so na primer temperaturna odvisnost, viskozne in kohezivne lastnosti veziva in hitrost preoblikovanja. Za validiranje takšnega modela so potrebne nove eksperimentalne študije ter razvoj in obsežno testiranje kontaktnega algoritma. Forming of complex carbon fibre preforms predominantely depends on the effects of anisotropic friction. Simulation of the forming process using finite elements method enables succesfull definition of manufacturing proces parameters. Two simulation approaches of anisotropic friction in Abaqus software are presented in the thesis including testing of basic contact interaction models. An existing anisotropic model does not suffice for carbon fibre preforming simulations. Outline and functioning of a user subroutine for anisotropic friction modellling are presented and developed to include basic functionalities.

V diplomskem delu je predstavljen razvoj kompozitnega pokrova za mobilni skuter od razvoja do prototipa. Izdelek ima vlogo zaščite elektronskih in drugih ostalih delov pred mehanskimi in drugimi vplivi. Ima tudi estetsko vlogo. V delu so predstavljene tehnologije, ki bi lahko prišle v poštev za izdelavo samega izdelka. Opisan je postopek izdelave kalupa za željeni izdelek in tudi sama izdelava končnega produkta. S pomočjo programa Abaqus je ob predpostavljenih obremenitvah analiziran model pokrova. V analizi je preverjeno do kakšnih deformacij lahko pride in kakšen je indeks Tsai-Wu porušitvenega kriterija. In this graduation thesis the development and manufacturing of a composite cover of mobility scooter is fully presented. The function of the prototype is protection of electronic and other parts from weather and other effects. The composite cover is also meant to give the scooter better aesthetics. All possible manufacturing methods are introduced in this work. Manufacturing process of the mould is described. Final laminating is presented. With the analyse program Abaqus, the model is tested under assumed conditions. In simulation deformation and index of Tsai-Wu the failure method is tested.

Perutninska industrija s svojim delovanjem bistveno prispeva h količini odpadnega perutninskega perja, ki je okoljsko zelo obremenjujoč in za odlaganje zelo zahteven odpadek. Ocenjeno je, da v svetu letno nastaja 5 mio. ton odpadnega perja, zato potekajo obširne raziskave možnosti ponovne uporabe tega materiala. Ena izmed možnosti je uporaba perja kot adsorpcijsko sredstvo za olja iz vode, saj je zaradi svojih fizikalno-kemičnih lastnosti perje pokazalo odlične rezultate pri vezavi oljnih nečistoč v svojo strukturo. Namen magistrskega dela je bil razviti kompozitni material na osnovi odpadnega perutninskega perja za odstranjevanje oljnih razlitij na površini vode. Z dodajanjem keramičnih delcev sepiolita, ki velja za odličen oljni adsorbent, odpadnemu perju, smo želeli izdelati kompozit z izboljšano adsorpcijsko sposobnostjo v primerjavi z osnovnimi komponentami. Za karakterizacijo osnovnih materialov smo uporabili svetlobno mikroskopijo, vrstično elektronsko mikroskopijo, sejalno analizo delcev ter metode določanja osnovnih lastnosti olja. Za izdelavo kompozitov smo med drugim uporabljali postopke mehanskega in termičnega stiskanja. Adsorpcijske lastnosti materialov smo določali v skladu s standardom ASTM F726-12. Ugotovili smo, da dodatek sepiolita ne prispeva bistveno k adsorpcijskim lastnostim kompozita, saj zaradi višje gostote in nižje relativne adsorpcijske sposobnosti zmanjšuje vrednosti adsorpcije kompozitnega materiala. Rezultati so potrdili najučinkovitejšo adsorpcijo olja v primeru blazinic, sestavljenih iz poliestrne tkanine in napolnjene s čistim perjem. Poultry industry has a huge impact on the amount of the scrap poultry feathers which are onerous for the environment and course problems with their disposal. Assessments show that more than 5 Mio tons of poultry feathers are being disposed every year which lead to extensive researches about the options for reusing. One of those is the reuse as an adsorbent agent for production of oils out of water, due to the physical and chemical properties that show great results in binding with the impurities in oils. Purpose of this written thesis was the development of composite material based on the waste poultry feathers to remove oil spills on the water surfaces. Our goal was to develop a composite with better adsorption capacity in comparison to its basic compounds. We tried to achieve our goal by adding ceramic parts of sepiolite, which are classified as a great oil adsorbent, to the poultry feathers. We used optical microscopy, scanning electron microscopy, separation analysis of particles and method of determination for the properties of oil. For preparation of composites we used methods of mechanical and thermal compression, among others. We used ASTM F726-12 standard to determine the adsorption properties of materials. Our finding show that adding sepiolite does not have a great influence on the adsorption properties of composition, as values of adsorption of composite material lower due to the higher density and lower relative adsorption rates. Our findings conformed the best results of oil adsorption can be reached with the usage of pillow made of polyester and filled with poultry feathers.

Advanced pore morphology (APM) structures are composite metal foams, which are assembled from a large number of small spherical elements with cellular structure, and are bonded into a composite with polymeric adhesive. The result of such composition is a wide spectrum of achievable mechanical behaviour in APM structures. To explore their full potential, efficient computational models are needed, which allow for simple parameter variation. Unfortunately, the current computer models do not allow for efficient simulations of porous composite structures with advanced pore morphology, as they employ complex discretisation approaches. A new approach to simulation is presented in this work, based on the discrete particle method (DPM), where every element of APM structure is discretised with a single node. This enables more efficient simulations of APM structures, while still allowing for simple variation of structural parameters. The DPM method was augmented with constitutive models of normal and tangential contact behaviour of APM elements and bonds between them, which were formulated based on an extensive experimental study of APM structure's geometry and mechanical behaviour. Consequently, the models enable simulations of large APM structure's behaviour by modelling the contact behaviour of individual elements. The implementation of new models was verified on a set of analytically solvable examples, and the accuracy of the models was validated with very good correspondence between computational and experimental results. Moreover, the models were validated on a wide set of examples, also taking into account the various strain rates and the absence of the bonds. The applicability of new models was demonstrated in a comprehensive parametrical study, where the influential structural parameters and properties were identified for low and high strain rate deformations. The study also demonstrated the possibility of customising the mechanical behaviour with property gradation, and with introduction of regular, as well as geometrically complex APM element assemblies. The possibility of coupled discrete particle method and finite element method simulations was also addressed. The newly developed models represent a breakthrough in the field of computational investigation of APM structures, and provide for simpler and more efficient investigations of APM structures in the future. Strukture z napredno morfologijo por (APM strukture) so kompozitne kovinske pene, sestavljene iz velikega števila majhnih okroglih elementov z celično notranjo zgradbo, ki so spojeni v kompozit s polimernim vezivom. Rezultat takšne zgradbe je širok spekter dosegljivega mehanskega obnašanja v APM strukturah. Za raziskanje njihovega resničnega potenciala potrebujemo učinkovite računske metode, ki omogočajo preprosto variiranje parametrov. Trenutni računalniški modeli žal ne omogočajo učinkovitih simulacij poroznih kompozitnih struktur z napredno morfologijo por, saj temeljijo na kompleksnejših pristopih k diskretizaciji. V tem delu je predstavljen nov pristop k simulacijam, ki temelji na metodi diskretnih delcev (metodi DPM), v kateri je vsak element APM strukture diskretiziran z enim samim vozliščem. To omogoča učinkovitejše simulacije APM struktur, vendar še zmeraj omogoča preprosto variiranje strukturnih parametrov. DPM metoda je bila razširjena s konstitutivnimi modeli normalnega in tangencialnega kontaktnega obnašanja APM elementov in njihovih povezav, ki so bili oblikovani na osnovi obširne eksperimentalne študije geometrije in mehanskega obnašanja APM struktur. Modeli zato omogočajo simulacije mehanskega obnašanja velikih APM struktur na osnovi modeliranja kontaktnega obnašanja posameznih elementov. Izvedba novih modelov je bila preverjena na nizu analitično rešljivih primerov, natančnost modelov pa je bila potrjena z zelo dobrim ujemanjem med računskimi in eksperimentalnimi rezultati. Modeli so bili tako potrjeni na širokem nizu primerov, ki so zajemali tudi različne hitrosti deformacije in odsotnost vezi. Uporabnost novih modelov je bila dokazana v obsežni parametrični študiji, v kateri so bili identificirani vplivni strukturni parametri in lastnosti pri majhnih in velikih hitrostih deformacije. Študija je tudi dokazala možnost prirejanja mehanskega obnašanja s stopnjevanjem lastnosti ter z vpeljavo urejenih, kakor tudi geometrijsko zapletenih sestavov APM elementov. Naslovljena je bila tudi možnost sklopljenih simulacij po metodah diskretnih delcev in končnih elementov. Novo razviti modeli predstavljajo preboj na področju računalniških raziskav APM struktur ter zagotavljajo enostavnejše in učinkovitejše raziskave APM struktur v prihodnje.

V okviru doktorske disertacije smo s polimerizacijo v masi proučevali vpliv pogojev na pripravo glicidil metakrilatnih poroznih polimernih nosilcev. Proučili smo vplive zamreževala etilenglikol dimetakrilata in različnih porogenih topil na morfologijo poroznih nosilcev. Nosilce smo funkcionalizirali z različnimi amini in tioli. Dobljene porozne monolite smo tudi naknadno zamrežili, da smo povečali specifično površino. Pripravili smo tudi emulzije z visokim deležem notranje faze v organski fazi smo imeli raztopljen monomer. Kot monomer smo uporabili divinil adipat, ki je difunkcionalen vinil ester. Proučevali smo: vpliv sestave emulzije, tipa termičnega iniciatorja, dodatka topil in reakcijskih pogojev na stabilnost emulzije, morfologijo pripravljenih monolitov, obliko in velikost por ter poroznost. Divinil adipat kot samostojno uporabljen monomer še ni bil opisan, zato smo raziskali vpliv razmerja med hidrofilno in hidrofobno fazo emulzije na pripravo stabilne emulzije. Potreben je bil izbor primernih surfaktantov, kombinacije različnih surfaktantov ter količine topila. Pripravljene emulzije smo termično polimerizirali. Za radikalsko iniciacijo smo uporabili različne termične iniciatorje prav tako smo testirali uporabo fotokemičnih iniciatorjev. Proučili smo vpliv segrevanja in staranja emulzije na njeno stabilnost ter na združevanje kapljic emulzije. S segrevanjem emulzije smo dosegli 5-kratno povečanje kapljic, s staranjem 25 ur pa 0,4-kratno povečanje. Pripravili smo tudi emulzije brez soli v vodni fazi in tako povzročili Ostwaldovo rast in koalescenco kapljic v emulziji. Na ta način smo povečali velikost kapljic za dvakrat. Pri vseh metodah smo spremljali velikost kapljic emulzije in velikost primarnih por monolita, saj je velikost por polimera običajno sorazmerna z velikostjo kapljic notranje faze emulzije. Pripravljene monolite smo izpostavili različnim medijem z različnimi koncentracijami ter tako ugotavljali primernost medija in hitrost biorazgradnje. Pripravili smo tudi porozne polimere iz emulzije z visokim deležem notranje faze, nasičene z aluminijevim oksidom. Kot monomere smo uporabili propoksiliran trimetilol propan triakrilat in metil metakrilat, zamrežen z etilenglikol dimetakrilatom. Raziskali smo vpliv sestave emulzije na morfologijo monolitov: vpliv topila, surfaktanta, disperzanta in količino vodne faze. Z elektronsko mikroskopijo smo preučevali morfologijo pripravljenih monolitov. Vzorce z ustrezno poliHIPE morfologijo smo postpolimerizacijsko obdelali. V cevni peči smo s počasnim intervalom segrevanja do 1400°C izžgali organske komponente monolita. Ostal je skelet iz aluminijevega oksida, ki smo ga okarakterizirali z adsorpcijo/desorpcijo dušika, živosrebrno porozimerijo, helijevo piknometrijo in elektronsko mikroskopijo. Ustvarili smo visoko porozen polimer iz aluminijevega oksida z značilno poliHIPE morfologijo. Ugotovili smo tudi, da se med segrevanjem morfologija bistveno ne spremeni. Influences of reaction conditions on the structure of porous glycidyl methacrylate type polymer supports were studied. Glycidyl methacrylate was chosen as the main functional monomer due to availability and possibility of nucleophilic modifications of epoxy groups. We studied the influence of crosslinker ethylene glycol dimethacrylate and various porogenic solvents on the morphology of porous polymer supports. Porous polymer supports were subsequently functionalized with various amines and thiols. Furthermore, porous polymers were hypercrosslinked, with an aim of increasing specific surface area of polymers. Furthermore, high internal phase emulsions internal phase containing dissolved monomer were prepared. Divinyl adipate was chosen as monomer because it is a reactive difunctional vinyl ester that consists of two ester bonds which can undergo hydrolytic attack. Influences of different compositions of emulsions, different types of initiator, addition of solvents and reaction conditions on emulsion stability and morphology of prepared polymer supports were studied. Appropriate surfactants and solvent were chosen for the formations of stable emulsions. Thermal initiator was used for polymerisation of emulsions and the use of photochemical initiator was also studied. We also studied the size and the shape of droplets from emulsions being heated during the preparation and aging of emulsions. An increase in droplet size of 5 fold and with aging after 25 hours increase of 0.4 fold was achieved. Emulsion preparation without salt in aqueous phase which promotes Ostwald ripening and coalescence of emulsion droplets was further studied. Prepared divinyl adipate porous polymer supports were exposed to PBS buffer and sodium hydroxide with different concentrations for studying the rate of degradation and adequacy of these media for degradation. In the last part of the thesis work, emulsions with incorporated inorganic component namely aluminium oxide in the continuous phase, were prepared. Propoxylated trimethylolpropane triacrylate and methyl methacrylate were used as monomers. Influence of solvent, amount of water phase, surfactant and dispersing agent on emulsion stability and morphology were studied. Samples with open cellular structure were treated thermally after the polymerisation. At 1400° C the entire organic component was burned and only the inorganic component remained. The aluminium oxide, which was fused together by the high temperature formed a solid. These sintered materials obtained the initial morphology of the precursor polyHIPE.

V diplomskem seminarju obravnavamo optične lastnosti materialov, ki postanejo optično aktivni v zunanjem magnetnem polju. Osredotočimo se na nanokompozitni material, sestavljen iz optično aktivnega gostitelja ter optično aktivne primesi. Izračunamo efektivni tenzor dielektričnosti za tak material in nato še Verdetovo konstanto. In this seminar we present optical properties of materials which become optically active in external magnetic field. We focus on nanocomposite materials, which consist of optically active host and optically active inclusion. We calculate the efective dielectric tensor and the Verdet constant for such material.

Tradicionalne metode za procesiranje polimerov uporabljajo nevarna hlapna organska topila in kloro-floro-ogljikovodike. Zaradi povečanih izpustov nevarnih topil se pojavlja potreba po uporabi čistejših metod za procesiranje polimerov. Eno možnost predstavlja superkritični ogljikov dioksid (scCO2) kot mehčalo pri procesiranju polimerov. Velika uporabnost superkritičnih fluidov se kaže pri procesiranju polimerov za potrebe biomedicinskih pripomočkov (kot so mikrodelci, mikrokapsule, pene, membrane, kompoziti). Prednosti metode so predvsem v odsotnosti nevarnih organskih topil, učinkoviti ekstrakciji topil in nečistoč, procesnih pogojih, nižji temperaturi, nadzorovanemu oblikovanju delcev in pen z enostavnim reguliranjem tlaka in temperature. Navkljub velikemu potencialu scCO2 kot “zelenemu” topilu za procesiranje biokompatibilnih in biorazgradljivih polimerov, je podaktov o faznih ravnotežjih, ki so potrebni za načrtovanje postopka, dokaj malo. Nadaljnje raziskave so potrebne za optimiranje procesnih tehnik in parametrov (tlak, temperatura). Podatkov o uporabi scCO2 za procesiranje kompozitov polimer/keramika za biomedicinske aplikacije je še posebej malo na razpologo. Cilj te disertacije je uporaba scCO2 kot “zelenega” topila za procesiranje biorazgradljivih polimerov in kompozitov, ki se uporabljajo kot biomateriali. V raziskavah smo uporabili dva biorazgradljiva polimera, poli(L-laktid) (PLLA) in poli(D,L-laktid-ko-glikolid) (PLGA). Raziskali smo tudi kompozite polimerov z bioaktivnim keramičnim prahom, hidroksiapatitom (HA). Glavni cilj raziskav je bil pridobiti porozen polimer ali kompozit, primeren za tkivni inženiring, pri nizki temperaturi in brez uporabe dodatnih organskih topil. Študirali in razložili smo obnašanje obeh polimerov v zmesi s CO2. Z določitvijo topnosti in difuzijskega koeficienta CO2 v polimerih pri določeni temperaturi in tlaku, smo pridobili več podatkov o faznem ravnotežju polimer-plin, ki so pomembni za razumevanje vpliva in optimiranje procesnih parametrov. Topnost CO2 v polimerih smo izmerili pri treh različnih temperaturah (308, 313 in 323 K) in v območju tlaka 10 – 30 MPa. Izbrane temperature so bile višje od kritične temperature za CO2, vendar še vedno dovolj nizke, da ne bi vplivale na bioaktivnost spojin ali proteinov dodanih v sistem med procesiranjem. Pri testiranju poimerov in kompozitnih materialov smo uporabili enako temperaturno in tlačno območje. Raziskali smo učinkovitost mešanja v prisotnosti scCO2 za pridobivanje kompozitnega materiala iz PLLA in HA ter PLGA in HA in postopek primerjali s postopkom koprecipitacijie. Nadalje smo določili topnost in difuzijski koeficient CO2 v kompozitnih materialih ter jih primerjali z rezultati pridobljenimi za čiste polimere. Tako smo lahko določili vpliv keramičnega polnila na absorpcijo plina. Ocenili smo možnosti pridobivanja poroznih struktur z uporabo visokotlačne tehnike s CO2 kot vpihovalnim medijem brez oziroma z dodanim porogenom. Raziskali smo vpliv tlaka, temperature, ekspanzijske hitrosti in prisotnost porogena na končno porozno strukturo. Eksperimentalne rezultate smo primerjali s podatki iz literature in z rezultati dobljenimi z matematičnim modeliranjem. Rezultati kažejo, da postopek plinskega penjenja biorazgradljivih polimerov predstavlja obetavno tehniko pridobivanja opornih tkiv z željeno strukturo. V prihodnjih raziskovah bodo potrebne nadaljnje študije in optimiranje procesnih parametrov glede na naravo substrata in željen končni produkt. The traditional methods for polymer processing use environmentally hazardous volatile organic solvents and chlorofluorocarbons. Due to the increase of hazardous solvent emission and generation of aqueous waste streams, there is an obvious need of finding new and cleaner methods for the processing of polymers. Supercritical carbon dioxide (scCO2) has attracted particular attention for these applications due to its tremendous potential as a plasticizer in polymer processing. A particular interest is shown to the use of supercritical fluids for processing polymers destined for biomedical applications (as microspheres, microcapsules, foams, membranes, polymer/drug composites). The method offers important advantages related to the absence of harmful organic solvents or, when necessary, the efficient extraction of solvents and impurities, the mild processing conditions and the control of particle and foams morphology by simple variation of pressure and temperature. Despite the huge potential of scCO2 as a “green” solvent for processing biocompatible and biodegradable polymers, the phase equilibrium data, essential for process design, are quite scarce. Optimum processing techniques and parameters (pressure, temperature) still need consideration and study. The data are especially scarce regarding the scCO2 processing of polymer/ceramic composites for biomedical applications. On this basis, this thesis is aimed to open new perspectives over the use of scCO2 as a “green” solvent for the processing of biodegradable polymers and composites used as biomaterials. Two biodegradable polymers were chosen for this study, poly(L-lactide) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA). Their composite with a bioactive ceramic powder, hydroxyapatite (HA), was also studied. The main idea followed by this thesis was the obtaining of porous polymeric or composite material scaffolds suitable for tissue engineering under mild temperature conditions and without the use of additional organic solvents. The behavior of the two polymers under dense CO2 had been studied and explained. More data about the polymer-gas phase equilibrium, necessary for understanding and optimizing the effect of processing parameters, were obtained by determining the solubility and diffusion coefficients of CO2 in the polymers for certain values of temperature and pressure. The solubility of CO2 was measured for each polymer for three different temperatures (308, 313 and 323 K) in the pressure range 10 – 30 MPa. The temperatures were chosen higher than the critical temperature for CO2, but still low enough so as not to affect the bioactivity of any drugs or proteins that could be introduced in the system during processing. The same range of temperature and pressure was employed for all tests involving the studied polymers or their composite materials. The efficiency of mixing in the presence of scCO2 for obtaining composite materials from PLLA and HA and respectively PLGA and HA was studied by comparison with coprecipitation. The solubility and diffusion coefficient of CO2 in the composite materials were afterward determined, and the results were compared with the ones obtained for the polymer alone in order to determine the effect of the ceramic filler on the gas uptake. The possibility of obtaining porous scaffolds was assessed by using a pressure quench technique using dense CO2 as blowing agent, with and without the presence of a porogen. The effect of pressure, temperature, depressurization rate and porogen on the final porous structure was investigated. The experimental results were compared with literature data and with data obtained by mathematical modeling, employing equations of state commonly used for polymers or polymer/solvent systems. The results indicate that gas foaming of biodegradable polymers represents a promising technique for obtaining tissue engineering scaffolds with the desired structure. Still the processing parameters need to be studied and optimized, according to the nature of the substrate and of the aimed final product.