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This study investigated the influence of hemicelluloses and lignin removal on the sorption and electric properties, as well as fineness of hemp fibers. Hemp fibers with different content of either hemicelluloses or lignin were obtained by chemical treatment with 17.5% sodium hydroxide or 0.7% sodium chlorite. The sorption properties of hemp fibers were evaluated as moisture and iodine sorption, while electric properties were evaluated as volume electric resistance. Hemicelluloses removal increases in higher extent fiber liberation than lignin removal; the modified hemp fibers were finer up to 12 times in relation to unmodified fibers. Furthermore, hemicelluloses removal increased the moisture and iodine sorption, as well as electric resistance of hemp fibers compared to unmodified fibers, while lignin removal decreased both moisture and iodine sorption, and only slightly increased the electric resistance of modified hemp fibers.

U teorijskom delu rada su sistematizovani najznačajniji literaturni podaci u vezi sa hemijskim sastavom, reaktivnošću pratećih supstanci, molekulskom i nadmolekulskom strukturom, svojstvima i postupcima modifikovanja vlakana konoplje. Obzirom na to, da vlakna konoplje imaju heterogen hemijski sastav u kome preovlađuje celuloza, u teorijskom delu je prvo ukazano na: naučni razvoj modela strukture nativne celuloze, celulozne alomorfizme i oblike kristalnih rešetki, kao i na reaktivnost nativne celuloze prema različitim reaktivima, što predstavlja osnovu za eksperimentalni deo ovog rada, tj. izbor odgovarajućih postupaka modifikovanja vlakana konoplje. Uzimajući u obzir da u hemijskom sastavu vlakana konoplje, kao konstituenti, pored celuloze učestvuju i prateće materije (supstance rastvorne u vodi, masti i voskovi, pektini, odrvenjena komponenta-lignin i hemiceluloze), izvršeno je njihovo definisanje (hemijski sastav, reaktivnost) i objašnjen je uticaj ovih komponenata na reaktivnost celuloze. Kao posebna celina u okviru teorijskog dela doktorske disertacije obrađeni su mogući postupci modifikovanja vlakana konoplje sa posebnim osvrtom na promene koje pri tome mogu nastati. Ove promene se uglavnom odnose na hemijski sastav, strukturu, fizičko-hemijska i elektrofizička svojstva vlakana konoplje. U eksperimentalnom delu doktorske disertacije proučavan je uticaj parametara hemijskog modifikovanja vlakana konoplje (17,5 % NaOH, sobna temperatura, tokom 5, 10, 20, 30 i 45 minuta, u cilju postupnog uklanjanja hemiceluloza i 0,7 % NaClO2, temperatura ključanja, tokom 5, 15, 30 i 60 minuta, u cilju postupnog uklanjanja lignina), na njihov hemijski sastav, strukturu, fizičko-hemijska i elektrofizička svojstva. Parcijalno uklanjanje hemiceluloza dovodi do povećanja sorpcije vlage i smanjenja sposobnosti zadržavanja vode u vlaknima konoplje, dok uklanjanje lignina utiče na smanjenje sadržaja vlage i povećanje sposobnosti zadržavanja vode vlakana. Takođe, dolazi do poboljšanja kapilarnih svojstava vlakana konoplje, jer je ravnotežna visina kapilarnog penjanja tečnosti modifikovanih vlakana povećana i do 2,7 puta u odnosu na nemodifikovana vlakna konoplje. Dobra sorpciona svojstva i promena u strukturi modifikovanih vlakana konoplje, omogućavaju upotrebu ovih vlakana za sorpciju jona teških metala iz njihovih vodenih rastvora. Rezultat modifikovanja vlakana konoplje je visok stepen njihove deljivosti, što pokazuju vrednosti za finoću. Gipkost ovih vlakana je takođe povećana, a u nekim slučajevima je poboljšana i njihova jačina. Zapreminska električna otpornost alkalno modifikovanih vlakana konoplje je povećana, dok je za oksidisana vlakna skoro ista kao kod polaznih vlakana. Na sve ove promene u velikoj meri je uticalo uklanjanje hemiceluloza iz interfibrilarnih oblasti i lignina iz srednje lamele vlakana konoplje, što je imalo uticaj na prostorni raspored i orijentisanost fibrila, a samim tim i na strukturu i mikroporoznost vlakana. Dobijeni rezultati istraživanja su omogućili da se sa fundamentalnog aspekta sagleda problematika bitna za preradu i upotrebu vlakana konoplje i proizvoda dobijenih od ove vrste vlakana. In the theoretical part of this thesis, the most relevant literature data on chemical composition, properties, molecular and supramolecular structure of hemp fibers as well as reactivity of their accompanying substances and modification procedures are reviewed. Taking into account the heterogeneous chemical composition of hemp fibers with cellulose as a main component, the development of native cellulose model, the cellulose alomorphisms, types of crystal lattices and the reactivity of native cellulose towards different chemical reagents are described in detail. This review was the basis for the experimental part, i.e. the selection of appropriate procedure for modification of hemp fibers. In addition to cellulose, different accompanying substances (water-soluble substances, fats, waxes, pectins, lignin and hemicelluloses) are defined (chemical composition, reactivity) and their influence on the reactivity of cellulose was analyzed. The developed procedures for modification of hemp fibers so far are described with particular emphasis on the induced overall fiber changes. These changes mainly correspond to chemical composition, structure, physico-chemical and electro-physical properties of hemp fibers. In experimental part, influence of parameters of chemical modification of hemp fibers (17.5 % NaOH, at room temperature, for 5, 10, 20, 30 and 45 minutes, in an attempt to gradually remove hemicelluloses and 0.7 % NaClO2, at boiling temperature, for 5, 15, 30 and 60 minutes, in an attempt to gradually remove lignin), on their chemical composition, structures, physico-chemical properties and electrophysical properties, was studied. Hemicelluloses removal increases the moisture sorption and decreases the water retention values of hemp fibers, while lignin removal decreases the moisture sorption and increases the water retention ability of hemp fibers. Also, the capillary properties of hemp fibers are improved, i.e. capillary rise height of modified fibers is increased up to 2.7 times in relation to unmodified fibers. Good sorption properties and changes in the structure of modified hemp fibers, allow the use of these fibers for sorption of heavy metals ion from their water solution. Results of modification of hemp fibers were a high level of divisibility, which showed with values of fineness. Modified hemp fibers have higher flexibility and in some cases tensile properties are improved. Volume electric resistance of alkali modified hemp fibers are decreased, but for oxidizing hemp fibers values of volume electric resistance are almost like as the unmodified fibers. Changes of physico-chemical and electrophysical properties are result of removing of hemicelluloses from interfibrillar region and lignin from middle lamelae, which influence on space arrangement and orientation of fibriles, and on structure and microporosity of fibers. This research results have enabled to recognize fundamentally the issues relevant for processing and using of hemp fibers and products from these fibers.

In this paper, short history ofjeans are given, and tertile fibers used forjeans production and their most important properties are revievved. U radu je pored kratke istorije džins odeće, dat i pregled tekstilnih vlakana koja se koriste za proizvodnju džinsa, sa njihovim najznačajnijim svojstvima.

Each year more and more people focus on healthy, ecological and environmental-friendly living. Environmentally friendly lifestyle doesn’t mean that we are using only natural products, but attention is pointed to the manufacturing and production process also. The rapid development of recycled and biodegradable products causes expanding usage of hemp fibers both in household and technical textiles. The analysis of hemp cultivation and usage trends in the world and Europe shows that hemp cultivation and processing in Latvia has good perspectives. Product quality is influenced by raw materials. In this case it is hemp fiber descriptive characteristics. Hemp fibers are natural fibers and their properties varies according to plant growing regional climatic conditions, amount of manure, plant density, harvesting time and pre-treatment technological processes. There are studied the influence of above mentioned factors on chemical composition, geometrical and physical properties of the Latvian hemp fiber both local and foreign cultivars. The work was carried out in cooperation between Riga Technical University, Textile Technology and Design Institute and the Agriculture Science Centre of Latgale.

The objective of this research is to study the influence of several recycling cycles on the mechanical properties of four different materials made by the injection of polystyrene. The four materials studied have different characteristics. The first one is polystyrene (PS), the second one is polystyrene reinforced with hemp fibers (PSf), the third one is polystyrene reinforced with hemp fibers modified with AKD (PSft) and the last one is polystyrene reinforced with fiberglass (PSfv). With all these materials tensile strength, bending, hardness and impact is measured. After the measurement of these physical properties, materials are recycled to obtain new injection samples, and its physical properties are measured again. This process is repeated during 24 cycles.After each recycling cycle material physical properties are related with polystyrene molecular weight, melt flow, FTIR spectra and DSC.From reinforced materials, fibers are recovered and through microscopy and image analysis they are characterized to study the influence that recycling has on its structure.

Practiced for more than three thousand years, Chinese painting stresses the notion of "implicit meaning" in which painters use a minimum amount of strokes to express their deepest feelings. Chinese landscape and figure paintings are the two major themes of Chinese painting. Of relevant interest is more thoroughly understand Chinese art by analyzing basic rules of Chinese painting. This paper proposes two novel methods capable of synthesizing rock textures in Chinese landscape painting and synthesizing portraits in Chinese figure painting, respectively. In addition to saving time during trial and error, these two methods attempt to synthesize painting styles. After users only specify the contour and parameters, our methods underwrite the complete painting process. With the requirement of familiarity with painting skills, individuals can paint various styles of Chinese painting.