Search

Ogljikove nanocevke predstavljajo superiorna multifunkcijska nanopolnila v polimernih nanokompozitih, saj omogočajo odlično mehansko ojačitev, električno prevodnost in druge podobne lastnosti. Z uporabo nanoindentorja smo v sklopu diplomskega dela obravnavali vpliv koncentracije eno-stenskih ogljikovih nanocevk na mehansko ojačitev polimernih nanokompozitov iz polietilena nizke in polietilena visoke gostote. Rezultati so pokazali, da geometrijski preplet nanocevk znotraj polimernega veziva vpliva na dodatno mehansko ojačitev, vendar le od kritičnega masnega deleža nanopolnila (0,7 mas.% nanocevk). Največjo izboljšavo smo ugotovili pri približno 4 mas.% nanopolnila, kjer se modul elastičnosti v primerjavi z osnovnim materialom (brez dodanega nanopolnila) poveča za 274 % in trdota za 246 % polietilenu z nizko gostoto. Polietilenu z visoko gostoto se modul elastičnosti v primerjavi z osnovnim materialom (brez dodanega nanopolnila) poveča za 70 % in trdota za 73 %. Pri 5 mas.% dodanega nanopolnila se pojavi aglomeracija, kar je razvidno iz upada mehanskih lastnosti. Koncentracija nanopolnila na hrapavost površine nima bistvenega vpliva. S preizkusom praske smo pridobili hrapavost površine, največjo obremenitev, globino obremenitve in prečni presek. Iz dobljenih rezultatov sta vidni globina in širina praske ter višina nakopičenega materiala ob praski. Carbon nanotubes represent superior multifunctional nanofillers in polymer nanocomposites, as they enable excellent mechanical reinforcement, electrical conductivity and other similar properties. Using a nanoindenter, we studied the influence of the concentration of single-walled carbon nanotubes on mechanical strengthening of polymer nanocomposites made of low-density polyethylene and high-density polyethylene. The results showed that the geometric entanglement of carbon nanotubes leads to the additional mechanical reinforcement when the critical mass fraction of the nanofiller (0,7 % mass.) is exceeded. The best improvement was found at about 4 %wt. of nanofiller, where the modulus of elasticity, compared to the same material without any nanofillers increases by 274 % and the hardness by 246 % for low-density polyethylene. For high-density-polyethylene the modulus of elasticity, compared to the same material without any nanofillers increases by 70 % and the hardness by 73 %. At 5 %wt. of the added nanofiller, the agglomeration occurs, which is evident from the decrease of mechanical properties. The concentration of the nanofiller has no significant effect on the surface roughness. With the scratch test we obtained the surface roughness, the maximum load, the depth of the load, the cross-section.

Laser beam machining (LBM) is used to machine a variety of materials economically and to obtain the required quality metrics. The quality of the surface finish of laser-machined components is affected by the improper selection of process parameters during machining. In this paper, microchannels were machined on Al/TiB2 nanocomposite using an Nd: YAG laser system. An atomic force microscope was used to obtain the surface roughness of microchannels. The aim of this process is to identify the influence of the individual and interactive effect of the process parameters on the surface roughness of the microchannels and to identify the optimum combination of the process parameters for minimum surface roughness. Taguchi’s L9 orthogonal array-based Design of Experiment (DoE) was implemented to conduct the experimental study. A statistical analysis of the results was performed for the experimental data. The results are presented in detail.

Ogljikove nanocevke zaradi svojih inherentnih lastnosti (npr. izjemna trdnost, efektivni prenos elektronov itd.) in paličaste geometrije, predstavljajo enega izmed najpotencialnejših nanopolnil v polimernih nanokompozitih. V polimernem materialu vzpostavijo tako imenovano omrežje, ki služi kot mehanska ojačitev, prevodna pot, kar lahko izrabimo v različnih trenutnih in prihodnje nastajajočih tehnologijah. V okviru magistrskega dela smo se osredotočili na vpliv ogljikovih nanocevk na časovno odvisno mehansko vedenje, kjer smo preverili vpliv dodatka nanocevk na mehansko ojačitev ter hitrost lezenja polimerne matrice. Rezultati so pokazali, da dodajanje nanocevk pripomore k izboljšanju mehanske ojačitve do 300 %, kar je posledica geometrijskega prepleta cevk znotraj matričnega materiala. Poleg omenjenega smo ugotovili, da nanocevke upočasnijo hitrost primarnega lezenja, vendar zaradi zmanjšanja urejenosti matričnega materiala (padca kristaliničnosti) pospešijo hitrost sekundarnega in terciarnega lezenja. Carbon nanotubes represent one of the most promising nanofillers in polymer-based nanocomposites, due to their rod-like geometry and other inherent properties (e.g. exceptional strength and effective electron transfer). Within the polymeric material, they establish a network that serves as a mechanical reinforcement or a conductive pathway, which is useful in various current and emerging technologies. As part of this master’s thesis, we discussed the effects of carbon nanotubes on time-dependent mechanical behavior, primarily focusing on the effects of nanotubes on mechanical reinforcement and creep rate. Results showed that adding nanotubes could increase the mechanical reinforcement up to 300% because of the network formation within the matrix material. Moreover, it was shown that adding nanotubes slows down the rate of the primary creep and also reduces the degree of crystallinity, which accelerates the rate of the secondary and tertiary creep.

Polietilen je zaradi svojih mehanskih in kemičnih lastnosti eden najpogosteje uporabljanih polimernih materialov, tudi za matrični material kompozitov. V kombinaciji z ogljikovimi nanocevkami, ki zagotavljajo izredne karakteristike, tvorijo revolucionarne nanokompozite, katere je možno aplicirati v najzahtevnejša področja današnje znanosti. V sklopu naloge smo obravnavali vpliv omrežja ogljikovih nanocevk na mehanske lastnosti, kjer smo z uporabo nanoindenterja določili elastični modul, trdoto, ter površinske lastnosti, kot so hrapavost ter odpornost na praske. Teste smo izvedli na vzorcih polietilena nizke in visoke gostote z različno vsebnostjo enostenskih ogljikovih nanocevk. Rezultati so pokazali da omrežje (geometrijski preplet nanocevk) nastane pri ?0.7% in je glavni faktor pri ojačitvi oziroma izboljšanju mehanskih lastnosti nanokompozitov. V primeru LDPE-nanokompozitov se elastični modul izboljša za 250% ter trdota za 225%, v primeru HDPE-nanokompozitov pa se omenjeni lastnosti izboljšata za 122% in 130%. Ugotovljeno je bilo tudi to, da se hrapavost z dodajanjem nanopolnila poveča za 100nm, tako v primeru LDPE- kot HDPE-nanokompozitov. Polyethylene is since its mechanical and chemical properties one of the most common used polymer materials additionally as matrix composite material. In combination with carbon nanotubes, thus hold extraordinary characteristics, they form revolutionary nanocomposites that are possible of application into the most demanding fields of nowadays' science. Within the framework of the thesis, we discussed the influence of the carbon nanotube networking on mechanical properties, where we determined the elastic modulus, hardness, and surface properties, such as roughness and resistance to scratch, using a nanoindenter. The tests were performed on low- and high-density polyethylene samples with different mass frictions of single-walled carbon nanotubes. The results showed that the network (geometric entangling of nanotubes) is formed at ~0.7% and is the main factor in strengthening or improving the mechanical properties of nanocomposites. In the case of LDPE nanocomposites, the elastic modulus improves by 250% and the hardness by 225% , while in the case of HDPE nanocomposites, the mentioned properties improve by 122% and 130%. It was also found that the roughness increases by 100 nm with the addition of nanofillers in both LDPE and HDPE nanocomposites.

Nanocomposites based on 13X zeolite (13XZ), calcium oxide (CaO) and metal zinc particles (Zn) were prepared. The resulting nanocomposites were characterized by different techniques. Then, a comparative study on catalytic and noncatalytic pyrolysis of biomass waste was performed to establish the influence of nanocomposites used as catalysts on the yields and characteristics of liquid and solid products. Residual rapeseed biomass (RRB) was employed for pyrolysis experiments and a fixed bed reactor was used. By introducing CaO and metal zinc particles into 13X zeolite mass, the surface area (SBET) of nanocomposites was reduced, and this decrease is due to the introduction of nano-calcium carbonate and nano-zinc particles, which occupied an important space into zeolite structure. By adding CaO to 13XZ, the pore structure was changed and there was a decrease in the micropores volume. The analysis of the pore area distribution showed a hierarchical pore structure for nanocomposites. The elements composition showed that the main elements contained in nanocomposites are Si, Al, Ca and Zn, confirming the preservation of the zeolite structure. Using these nanocomposites as catalysts in pyrolysis process, the residual biomass could be valorized, producing bio-oil and biochar for the management and sustainability of this low-value waste.

The reinforcing and conductive performance of carbon nanotube polymer-based nanocomposites depends on the established network and its configuration. Within this study, we report on the underlying mechanisms of such network formation utilizing single-walled carbon nanotubes (SWCNTs) in low- and high-density polyethylene matrices. Mechanisms were theoretically evaluated through Doi-Edwards theory and experimentally confirmed through plasma etching coupled with electron microscopy as well as rheological flow tests. Results showed that the established network is constructed from SWCNT bundles, which geometrically entangle at a critical volume fraction [phi]v,crit (number of rods: [beta approximately equal to] 30). Below [phi]v,crit, the bundles behave as individual units and may align in the flow direction. Above [phi]v,crit, the rotation of bundles is constrained by neighboring units, leading to a random network configuration. Moreover, the theory successfully explains SWCNT bundle behavior as a Brownian entity and predicts network formation through diminishing thermo- and hydro-dynamically driven diffusion, which can be manipulated during the production to enhance reinforcing/conductive functionality of such materials.

Nanokompoziti, izdelani z ogljikovimi nanocevkami, odpirajo nova področja uporabe nanokompozitov in razumevanja fizikalno-kemijskih povezav, kjer nanocevke zaradi svojih unikatnih lastnosti predstavljajo superiorno nanopolnilo. Izjemna trdnost in sposobnost efektivnega prenosa elektronov sta le dve od lastnosti, ki jim dajejo posebno mesto v mehaniki in elektroniki. Izkaže se, da nanocevke vzpostavijo naključno povezano omrežje v matričnem materialu že pri nizkih koncentracijah, kar močno spremeni fizikalne lastnosti materiala. V predstavljenem delu smo preučili vpliv volumskega deleža na ojačitev materiala in spremembo časovno odvisnih lastnosti. Ugotovili smo, da z dodajanjem nanocevk izboljšamo mehansko vedenje materiala le v primeru, ko se vzpostavi omrežje. Vzpostavitev omrežja nad perkolacijsko mejo pospeši časovno odvisne procese, le to material oslabi. Nanocomposites prepared with carbon nanotubes open up new areas of application of nanocomposites and understanding of physicochemical inteactions, where nanotubes are a superior nanofiller due to their unique properties. Their exceptional strength and ability to efficiently transfer electrons are just some properties that give them a special place in mechanics and electronics. It turns out that nanotubes form a randomly connected network in the matrix material already at low concentrations, which significantly changes the physical properties of the material. In the presented work, we studied the effect of volume fraction on material reinforcement and the change of time-dependent properties. The results showed that the addition of nanotubes improves the mechanical behaviour of the material only when a network is established. The formation of the network above the percolation limit speeds up time-dependent processes, which weakens the material.

Kompoziti kalcijevih fosfata i titanatnih nanomaterijala, zbog komplementarnih svojstava komponenti, privlače sve veću pažnju kao napredni materijali za regeneraciju čvrstih tkiva. Dosadašnja istraživanja takvih nanokompozita većinom su usmjerena na prekrivanje nanostrukturiranih TiO2 površina kalcijevim fosfatima kako bi se poboljšala njihova bioaktivnost. Cilj ovog doktorata sustavno je istražiti biomimetsko nastajanje nanokompozita kalcijevih fosfata i titanatnih nanomaterijala u uvjetima što bližim fiziološkim. Uspoređena su dva načina sinteze nanokompozita, inkubiranjem u simuliranoj tjelesnoj tekućini te taloženjem iz suspenzije. Također je određen utjecaj biološki aktivnih molekula, albumina iz goveđeg seruma (BSA) i kitozana, na nastajanje nanokompozita. Kako bi se dobio uvid u ponašanje sintetiziranih kompozita in vivo, određeni su parametri adsorpcije i vezanja albumina iz seruma, proteina koji se pri ugradnji prvi veže na površinu implantata. Dobiveni rezultati ukazuju da je taloženje brza i svestrana metoda priprave nanokompozita kalcijevih fosfata i titanatnih nanomaterijala u kojoj se, neovisno o vrsti titanatnih nanomaterijala, ne mijenja sastav niti struktura kalcijevih fosfata. Takvi nanokompoziti pokazuju poboljšana svojstva adsorpcije proteina u odnosu na čiste kalcijeve fosfate, što ukazuje na njihov potencijal u biomedicinskim primjenama. Calcium phosphates and TiO2 nanomaterials composites are attracting attention as advanced materials for bone regeneration due to the complementary properties of the components. Current studies of such composites focus on coating TiO2 nanostructures with calcium phosphate layers to improve their bioactivity. The aim of this doctoral thesis was to systematically investigate the biomimetic preparation of nanocomposites based on calcium phosphate and titania nanomaterials under physiological conditions. Two methods of nanocomposite synthesis were compared, immersion in simulated body fluid and precipitation from a suspension. In addition, the influence of biologically active molecules, bovine serum albumin and chitosan, was determined. To evaluate the in vivo behavior of the prepared composites, the adsorption and binding parameters of serum albumin were determined, since this protein is the first to interact with the implant materials after implantation. The obtained results showed that precipitation from solution is a rapid and versatile method for preparing TiO2 and calcium phosphate composites, in which no changes in the composition or structure of the calcium phosphate phase depending on the type of titanium nanomaterials was observed. Such composites exhibit improved protein adsorption properties, indicating their potential for biomedical applications.

Ogljikove nanocevke zaradi inherentnih lastnosti predstavljajo superiorna funkcionalna polnila v polimernih nanokompozitih, saj omogočajo odlično mehansko ojačitev, električno prevodnost in druge podobne lastnosti. Rezultati doktorskega dela so pokazali, da se ogljikove nanocevke med predelavo razpletejo v obliki snopov (sekundarnih aglomeratov), ki pa jih lahko obravnavamo kot Brownove (termo- in hidrodinamsko gnane), palicam podobne enote. Te se pri kritičnem volumskem deležu ?(v,krit) (ß?30) v polimernem materialu geometrijsko prepletejo ter vzpostavijo naključno povezano omrežje v skladu s teorijo reptacije paličastih sistemov. Vzpostavljeno omrežje spremeni morfološko sliko nanokompozitov, ki je predvsem vezana na skeletno strukturo makromolekul matričnega materiala in neposredno vpliva na mehansko vedenje nanokompozitov (mehansko ojačitev, časovno odvisnost, an/izotropijo itd.). Due to their inherent properties, carbon nanotubes (CNT) present a superior functional filler (mechanical reinforcement, electrical conductivity, etc.) in so-called polymer nanocomposites. The results of the PhD thesis showed that during precessing, CNT disentangle in the form of bundles (secondary agglomerates), which can be considered as Brownian (thermally and hydrodynamically driven) rod-like particles. At critical volume fraction Φ(v,crit) (β⡈30), those rods establish randomly connected network in the polymeric material (following a reptation theory of rod-like systems). The established network changes the morphological picture, which is mainly connected to the skeletal molecular structure of matrix material and directly affects the mechanical behavior of CNT nanocomposites (mechanical reinforcement, time-dependence, an/isotropy, etc.).

Uz lokanu vadošo polimēru nanokompozītu bāzes veidoti termoelektriskie ģeneratori ir viens no perspektīvākajiem valkājamu elektrisko ierīču enerģijas avotiem. Tomēr šo ģeneratoru izveidei problēmas galvenokārt sagādā n-tipa strāvu vadošo polimēru zemā stabilitāte. Šajā darbā tika izveidoti termoelektriskie nanokompozīti un ģenerators uz strāvu nevadošu polimēru bāzes kā veiksmīga alternatīva nanokompozītiem, kas veidoti no strāvu vadošajiem polimēriem. Par termoelektrisko pildvielu tika izmantotas Bi2Se3 un Sb2Te3 un oglekļa nanocaurulīšu (CNT) heterostruktūras, kuru īpašības pēdējā laikā arvien biežāk piesaista pētnieku uzmanību arī citur pasaulē. Bi2Se3 un Sb2Te3 nanostruktūras tika sintezētas uz CNT tīklojumiem, izmantojot bezkatalizatora fizikālo tvaiku nogulsnēšanas metodi. Iegūtās Bi2Se3/CNT un Sb2Te3/CNT heterostruktūras tika iemaisītas un iekapsulētas strāvu nevadošu polimēru matricās. Iegūto heterostruktūru un nanokompozītu morfoloģija un ķīmiskais sastāvs tika analizēts, izmantojot skenējošo un transmisijas elektronu mikroskopiju un enerģijas dispersīvo rentgenstaru analīzi. Termoelektriskās un elektriskās īpašības tika mērītas ar laboratorijā veidotu iekārtu un fizikālo īpašību mērījumu sistēmu. Tika salīdzinātas polimēru nanokompozītu īpašības pēc heterostruktūru iemaisīšanas un iekapsulēšanas polimēros un analizēti to pielietojumi termoelektriskās ierīcēs., Thermoelectric generators based on flexible conductive polymer nanocomposites are one of the most promising energy sources for wearable electronic devices. However, the low stability of n-type conductive polymers is a major problem for the further development of these generators. In this work thermoelectric nanocomposites and a generator based on non-conductive polymers were developed as a successful alternative to nanocomposites based on conductive polymers. Hybrid structures of Bi2Se3 and Sb2Te3 and carbon nanotubes (CNTs) were used as thermoelectric filler, the properties of which have recently attracted the attention of researchers in other parts of the globe. Bi2Se3 and Sb2Te3 nanostructures were synthesized on CNT networks via a catalyst-free vapour-solid deposition technique. The obtained Bi2Se3/CNT and Sb2Te3/CNT hybrid structures were mixed and encapsulated in non-conductive polymer matrices. The morphology and chemical composition of the obtained hybdrid structures and nanocomposites were analyzed by using scanning and transmission electron microscopy and energy dispersive X-ray analysis. Thermoelectric and electrical properties were measured with a laboratory-made experiment setup and a physical property measurement system. The properties of polymer nanocomposites after mixing and encapsulation of hybrid structures in polymers were compared and their applications in thermoelectric devices were analyzed.

Istraživanja u okviru teze imaju za cilj dobijanje polimernih mreža kod kojih se regulacijom sirovinskog sastava i uslova sinteze mogu menjati svojstva siloksanskih materijala u skladu sa krajnjom primenom. Osnovni cilj istraživanja ove teze je razvoj novih postupaka sinteze hibridnih siloksanskih nanokompozita na osnovu različitih prekursora mreža. Takođe, ispitan je i uticaj različitih tipova funkcionalizacije površina nanopunila silicijum(IV) oksida (sa hidrofobnom i hidrofilnom površinom) na svojstva kompozitnih materijala za specifične namene. Nanokompoziti na osnovu polimernih mreža se uglavnom koriste u onim primenama gde tradicionalne polimerne mreže ne mogu da zadovolje potrebe koje se pred njih stavljaju. Zato je potrebno razviti postupak koji bi omogućio dobijanje materijala na osnovu polimernih mreža sa poboljšanim mehaničkim, elastičnim i toplotnim svojstvima. Motivacija je vođena potrebom razvoja novih kompozitnih materijala koji imaju jedinstvena mehanička, toplotna, termomehanička svojstva sa mogućnošću da pomognu u rešavanju problema okoline, kao što su problem sa prostorom, sa automobilima, u elektronici i infrastrukturi, i naravno, oni će biti veliki izazov u nauci materijala i industriji.Siloksanske mreže su dobijene od α, ω-divinil poli(dimetilsiloksana) i poli(metil-hidrogensiloksana) u odnosu 60/40; 50/50 i 40/60. Nanokompoziti su sintetisani dodavanjem različitih sadržaja nanopunila silicijum(IV) oksida (1, 2, 5, 10 i 20 mas.%). Za potvrdu pretpostavljenog mehanizma reakcije umrežavanja siloksana korišćena je FTIR spektroskopija. TEM analiza je korišćena za procenu topologije i potvrdila je dobru disperziju punila u polimernom matriksu. Dodavanje nanopunila poboljšava mehanička svojstva dobijenih materijala i povećanje vrednosti prekidne jačine za kompozite sa hidrofobnim silicijum(IV)oksidom je veće u poređenju sa kompozitima sa hidrofilnim punilima, što je očekivano zbog bolje kompatibilnosti hidrofobne matrice i hidrofobnih punila. Termogravimetrijska analiza korišćena je za analizu uticaja vrste funkcionalizacije silicijum(IV) oksida na termičku stabilnost siloksanskih elastomernihmaterijala. Kao što se i očekivalo, porast sadržaja nanopunila povećava termičku stabilnost dobijenih hibridnih materijala. Uticaj punila na temperature faznog prelaza siloksanskih materijala analiziran je diferencijalnom skenirajućom kalorimetrijom. Zbog slabije kompatibilnosti hidrofilnog punila i hidrofobne matrice primećeno je smanjenje vrednosti Tm, a najmanja vrednost temperature topljenja primećena je za uzorak sa najvećim udelom hidrofilnog punila.Uticaj nanopunila na mehaničke i termičke karakteristike dobijenih materijala biće detaljno analiziran, pri čemu je potvrđeno poboljšanje mehaničkih svojstava siloksanskih elastomera dodatkom nanopunila. U cilju razvoja novih biokompatibilnih materijala i poboljšanja svojstava biorazgradivosti siloksanskih materijala biće sintetisani ABA blok kopolimeri koji se sastoje od segmenata poli(dimetilsiloksana) i poli(laktida). Kao makroinicijator za sintezu blok kopolimera korišćen je polidimetilisiloksan, pa je polimerizacija laktida inicirana hidroksilnim grupama siloksana. Poli(laktid) se odlikuje veoma dobrim mehaničkim svojstvima i biorazgradivošću, dok se kopolimerizacijom sa siloksanima utiče na mehanička svojstva kao i na svojstva površine sintetisanog kopolimera., Research in the thesis aims to obtain polymeric networks in which the regulation of the rawmaterial composition and the conditions of the synthesis can alter the properties of the siliconematerials in accordance with the final application. The main goal of the research of this thesis isthe development of new procedures for the synthesis of hybrid silicone nanocomposites based ondifferent precursors. The influence of different types of surface functionalisation of nanofillers(with hydrophobic and hydrophilic functionalised surface) on the properties of compositematerials for specific purposes was investigated. Nanocomposites based on polymer networks aremainly used in those applications where traditional polymer networks cannot meet the needs thatare expected. It is therefore necessary to develop a process that would enable the production ofmaterials based on polymeric networks with improved mechanical, elastic and thermal properties.Motivation is driven by the need to develop new composite materials that have uniquemechanical, thermal, thermo-mechanical properties with the ability to help solve environmental problems, such as space problems, cars, electronics and infrastructure, and of course they will bea challenge in the material science and industry. Siloxane networks were prepared from α,ω-divinyl poly(dimethylsiloxane) and poli(methyl-hydrogen siloxane) with a ratio 60/40; 50/50 and40/60. Nanocomposites were synthesised with the addition of different contents of silicananofiller (1, 2 5, 10 and 20 wt%). For the confirmation of the presumed mechanism of siloxanecrosslinking reaction FTIR spectroscopy was used. TEM analysis was used for topologyevaluation and confirmed good dispersion of the fillers into the polymer matrix. Addition ofnanofillers increased the mechanical properties of obtained materials and greater increase of thetensile strength for the composites based on hydrophobic silicon(IV)-oxide was assessed,compared with the hydrophilic ones. It was expected due to better compatibility of hydrophobicsilicone matrix and hydrophobic filler particles. Thermogravimetric analysis was used for theevaluation of the influence of the types of silicon(IV)oxide functionalisation, on the thermaldegradation of elastomeric materials. As it was expected the increases of nanofillers contentincreased the thermal stability of obtained hybrid materials. The influence of fillers on the phasetransition temperatures of siloxanematerials was analysed with the differential scanningcalorimetry. Due to the lower compatibility of hydrophilic filler and hydrophobic matrixdecreasing of Tm values was observed, and the lowest value of melting temperature was noticedfor the sample with the highest loading of hydrophilic filler.In order to develop new biocompatible materials and improve the biodegradability properties ofsilicone materials, ABA types of block copolymers consisting of segments ofpoly(dimethylsiloxane) and poly(lactide) was synthesized. As a macroinitiator for the synthesis ofthe block copolymer, poly(dimethylisiloxane) was used, so the lactide polymerization starts fromthe hydroxyl groups of siloxanes. Poly(lactide) is characterized by poor mechanical propertiesand biodegradability, while copolymerization with silicones will affect the mechanical andsurface properties of the synthesized copolymer.

Ultra-high molecular-weight polyethylene (UHMWPE) composites reinforced with Graphene Oxide (GO), Nanodiamonds (ND), and Short Carbon Fibres (SCF) are characterised for their mechanical performance in tensile and short-term creep tests. A methodology to separate and analyse the materials’ viscoelastic (VE) and viscoplastic (VP) responses is applied and evaluated. The results show a clear dependence of the performance on size scale/morphology of the reinforcements. All composites show time-dependent VP responses that can be expressed by Zapas model and fit the experimental data with high accuracy. The analysed VE strains and creep compliance curves reveal the nonlinear stress-dependent VE behaviour of all composites at all tested creep stresses. Combining multiscale reinforcements results in an improvement that surpasses that of individual reinforcements. The results of this work offer valuable input for the design and selection of polymer-based materials in demanding applications where prolonged use under service conditions is critical to their performance.

The aim of this in vitro study was to evaluate cytotoxicity and genotoxicity of six diff erent dental nanocomposite materials, three conventional ones and three fl owable composite resin materials, in human lymphocytes. Th e following materials were tested: Tetric EvoCeram, Tetric Evo-Flow, Filtek Ultimate, Filtek Ultimate Flow, G-aenial and G-aenial Flo. Cytotoxicity was evaluated for two mass concentrations (0.007 g/mL and 0.013 g/mL) of each material, non-cured and cured, after 4 hours and 24 hours. Genotoxicity was evaluated using micronucleus assay under the same conditions as applied during the investigation of cytotoxicity. Uncured forms of Tetric EvoCeram, Tetric EvoFlow and Filtek Ultimate Flow in higher mass concentration caused genotoxic eff ect. Uncured G-aenial Flo in higher mass concentration induced apoptosis and necrosis. Uncured Tetric EvoFlow and uncured Filtek Ultimate Flow in higher mass concentration induced early apoptosis after both test periods. None of the conventional composite resin materials tested showed cytotoxicity except for uncured G-aenial, which induced apoptosis in higher mass concentration in both test periods. In conclusion, under the conditions of this in vitro study, cured conventional composites did not show cytotoxic or genotoxic eff ect, which is important for clinical application of these materials, whereas uncured forms exhibited certain level of cytotoxicity and genotoxicity, mainly because of monomers in their composition., Svrha ovoga istraživanja bila je ispitati in vitro citotoksični i genotoksični učinak šest različitih nanokompozitnih materijala, tri tekuća i tri konvencionalna kompozitna materijala na stanicama ljudskih limfocita. Istraživanje je provedeno na materijalima: Tetric EvoCeram, Tetric EvoFlow, Filtek Ultimate, Filtek Ultimate Flow, G-aenial i G-aenial Flo. Ispitivan je citotoksični učinak dviju masenih koncentracija (0,007 g/mL i 0,013 g/mL) svakog ispitivanog polimeriziranog i nepolimeriziranog materijala nakon 4 sata i 24 sata. Genotoksični učinak je ispitivan primjenom mikronukleus testa u istim uvjetima kao što je učinjeno u ispitivanju citotoksičnog učinka. Nepolimerizirani oblici materijala: Tetric EvoCeram, Tetric EvoFlow i Filtek Ultimate Flow u većoj masenoj koncentraciji pokazali su genotoksični učinak. Nepolimerizirani G-aenial Flo je u većoj masenoj koncentraciji izazvao apoptozu i nekrozu. U oba ispitivana razdoblja nepolimerizirani Tetric EvoFlow i nepolimerizirani Filtek Ultimate Flow su u većoj materijala nije uzrokovao citotoksični učinak osim nepolimeriziranog G-aeniala koji je izazvao apoptozu u većoj masenoj koncentraciji u oba ispitivana razdoblja. Ovo istraživanje provedeno je u in vitro uvjetima. Polimerizirani oblici konvencionalnih kompozitnih materijala nisu pokazali citotoksični i genotoksični učinak koji bi bio važan za kliničku primjenu ovih materijala, dok su nepolimerizirani oblici ukazali na citotoksični i genotoksični učinak uglavnom kao rezultat djelovanja monomera koji se nalaze u sastavu kompozitnih materijala.

&nbsp, The aim of the study was to characterize and compare films made of cellulose nanocrystals (CNC), nano-fibrils (CNF), and bacterial nanocellulose (BNC) in combination with chitosan and alginate in terms of applicability for potential food packaging applications. In total, 25 different formulations were made and evaluated, and seven biopolymer films with the best mechanical performance (tensile strength, strain)—alginate, alginate with 5% CNC, chitosan, chitosan with 3% CNC, BNC with and without glycerol, and CNF with glycerol—were selected and investigated regarding morphology (SEM), density, contact angle, surface energy, water absorption, and oxygen and water barrier properties. Studies revealed that polysaccharide-based films with added CNC are the most suitable for packaging purposes, and better dispersing of nanocellulose in chitosan than in alginate was observed. Results showed an increase in hydrophobicity (increase of contact angle and reduced moisture absorption) of chitosan and alginate films with the addition of CNC, and chitosan with 3% CNC had the highest contact angle, 108 ± 2, and 15% lower moisture absorption compared to pure chitosan. Overall, the ability of nanocellulose additives to preserve the structure and function of chitosan and alginate materials in a humid environment was convincingly demonstrated. Barrier properties were improved by combining the biopolymers, and water vapor transmission rate (WVTR) was reduced by 15–45% and oxygen permeability (OTR) up to 45% by adding nanocellulose compared to single biopolymer formulations. It was concluded that with a good oxygen barrier, a water barrier that is comparable to PLA, and good mechanical properties, biopolymer films would be a good alternative to conventional plastic packaging used for ready-to-eat foods with short storage time.&nbsp

Photocatalysis is a well-known process for the last few decades it is predominantly used for water and air purification, but also for self-cleaning and antibacterial surfaces. The photocatalytic process is one of the advanced oxidation processes, where semiconductors are mainly used as photocatalysts. The most known and used semiconductor is nanosized titania, which can non-selectively decompose organic matters. One of the side effects of nano TiO2 under UV irradiation is photoinduced hydrophilicity, which furthermore improves the self-cleaning effect. The main drawback of TiO2 is that for its activation UV light is needed, which represents only 5 percent of the solar spectrum. Consequently, actinic irradiance power is low and the response of photocatalyst is limited. Novel approaches are being introduced to improve TiO2 response to visible light such as doping, coupling, modification of surface morphology and others. The thesis consists of five principal chapters. The first chapter is focused on a short literature review and explanation of some basic terms and principles that are related to this thesis. The aim of the research was to prepare transparent photocatalytically active thin films on glass and thermosensitive substrates. Four thermosensitive substrates were used: polyvinyl chloride (PVC) foil, polymethyl methacrylate (PMMA) sheet and polyester (PES) fabric coated with a polyvinyl and acrylic coating, with (D1) or without (D2) an additional polyvinylidene fluoride topcoat. The synthesis of films was modified with the introduction of zirconium aiming at improving the photocatalytic activity of the TiO2 films, and the final films had a SiO2 phase present for increased mechanical robustness. The third chapter is dedicated to the experimental part of the thesis. The detailed process of synthesis is described. The sol-gel process was used to prepare initial Ti-Zr sols, colloidal aqueous solutions with TiO2 and ZrO2 nanoparticles derived from titanium and zirconium alkoxides. The four different Ti-Zr sols were prepared with 0, 5, 10 and 20 molar % of Zr according to Ti. The depositing solution was prepared by mixing Ti-Zr sol, SiO2 sol binder, 1-propanol and 2-propoxyethanol, and then thin films were deposited by dip-coating technique. After the deposition, samples did not require high-temperature calcination since the photocatalytic anatase phase was present already after drying the deposited layers. Coated glass slides were put into a furnace at 150 °C, while samples on thermosensitive substrates were just treated by a heat gun. Samples in powder and thin film form were characterized by UV-Vis, FTIR-ATR and laser beam deflection spectroscopy, X-ray diffraction, scanning electron microscopy and thermal analysis. One of the main aspects of the photocatalyst is its activity. Photocatalytic activity of the thin films was determined, either quantitatively by the formation of fluorescent hydroxyterephthalic acid, one of the first degradation products of terephthalic acid deposit, or qualitatively by a visual-based method where degradation of resazurin ink was observed. Two additional methods were used on glass samples, electron paramagnetic resonance, and degradation of methyl stearate by observing the change in water contact angle under UVA irradiation. Mechanical stability of films on various substrates is an essential factor, describing how successful was immobilization of the photocatalytic materials on the substrate. It was determined by the pencil hardness test, i.e., Wolff-Wilborn method. In the fourth chapter, titled “Results and Discussion,” the most important part of the thesis is placed. Materials characterization and associated discussion of the results are divided into three major parts: i) powder samples characterization ii) characterization of thin films on a glass substrate, and iii) characterization of films on thermosensitive substrates. In the conclusions, the main findings of the Ph.D. research work are summarized. One of our initial hypotheses was disapproved, thin films were not more active with a higher content of zirconium. However, they were more durable. All the obtained films were transparent and photoactive, despite the low-temperature synthesis procedure. Besides commonly used glass substrate, immobilization on thermosensitive substrates was also successful. Fotokataliza je postala v zadnjih nekaj desetletjih zelo razširjena uporablja se predvsem za čiščenje vode in zraka, za samočistilne ter protibakterijske površine. Fotokatalitski proces spada med napredne oksidacijske procese in kot fotokatalizatorji so največkrat uporabljeni polprevodniki. Najbolj znan in najpogosteje uporabljen polprevodnik je (nano) titanov dioksid, ki lahko neselektivno razgradi organske snovi ob UV sevanju. Pri obsevanju TiO2 z UV svetlobo se pojavi tudi fotovzbujena hidrofilnost, ki še dodatno izboljša samočistilni učinek. Ena od glavnih pomanjkljivosti TiO2 je, da se za njegovo fotoaktivacijo uporablja UV svetloba, ki predstavlja le pet odstotkov sončnega spektra. Za boljši odziv TiO2 na vidno svetlobo se razvijajo novi postopki, na primer dopiranje, kombiniranje z drugimi polprevodniki, modifikacija morfologije površine itd. Doktorsko delo ima pet glavnih poglavij. Prvo poglavje je osredotočeno na krajši pregled obstoječe literature in razlago nekaterih osnovnih pojmov. V drugem poglavju je predstavljen namen doktorskega dela. Pripravila sem transparentne fotoaktivne tanke plasti na steklu in temperaturno občutljivih podlagah. Izbrala sem štiri različne občutljive podlage: polivinil kloridna (PVC) folija, polimetil metakrilat (PMMA) plošča in poliesterska (PES) tkanina, prevlečena s slojem polivinila in akrila z (D1) ali brez (D2) dodatne poliviniliden fluoridne (PVDF) prevleke. Postopek priprave filmov smo obogatili z vpeljavo cirkonija, tako naj bi izboljšali aktivnost samih TiO2 filmov, končni raztopini je bil dodan tudi SiO2, ki je izboljšal mehanske lastnosti filmov. Tretje poglavje je posvečeno eksperimentalnemu delu. V poglavju je opisan podroben proces sinteze tankih plasti. Sol-gel postopek sem uporabila za pripravo začetnih Ti-Zr solov izhajajoč iz titanovega in cirkonijevega alkoksida. Pripravila sem štiri različne Ti-Zr sole z 0, 5, 10 in 20 množinskimi % cirkonija glede na titan. Raztopine za nanašanje so vsebovale Ti-Zr sol, SiO2 vezivo, 1-propanol in 2-propoksietanol tanke plasti pa so bile nanešene s tehniko potapljanja. Tanke filme po nanosu ni bilo potrebno termično obdelati na visoki temperaturi, ker je fotoaktivna anatazna faza že prisotna po sušenju vzorcev. Tako so bili vzorci na steklu toplotno obdelani v peči pri 150 ° C, vzorce na termično neobstojnih podlagah pa sem utrdila zgolj s toplotno pištolo. Praškaste vzorce in tanke plasti smo karakterizirali z naslednjimi metodami: UV-Vis, FTIR-ATR spektroskopijo in spektroskopijo z odklonom laserskega žarka, rentgensko praškovno difrakcijo, presevno elektronsko mikroskopijo in termično analizo. Najpomembnejša lastnost fotokatalizatorja je fotoaktivnost, ta je bila določena na tankih plasteh z dvema različnima metodama kvantitativno z merjenjem koncentracije hidroksiteraftalne kisline po razgradnji teraftalne kisline in kvalitativno, z opazovanjem razgradnje barvila resazurin. Z dvema dodatnima metodama smo izmerili fotoaktivnost tankih plasti na stekleni podlagi, z elektronsko paramagnetno resonanco in z merjenjem kontaktnega kota po razgradnji metil stearata pri UV obsevanju. Zelo pomembna lastnost tankih plati je mehanska odpornost in z merjenjem le te lahko ocenimo, če je bila imobilizacija na podlago uspešna. Mehansko stabilnost filmov smo določili z Wolff-Wilborn-ovo metodo. V četrtem poglavju je opisana karakterizacija materialov s spremljajočo razpravo o rezultatih, ki je razdeljena na tri glavne dele: i) karakterizacija praškastih vzorcev ii) karakterizacija tankih plasti na stekleni podlagi in iii) karakterizacija tankih plasti na termično neobstojnih podlagah. V zaključku so povzete glavne ugotovitve. Ena od naših začetnih hipotez ni bila potrjena, saj tanke plasti z višjo vsebnostjo cirkonija niso bile aktivnejše, izkazovali pa so večjo mehansko odpornost. Vsi vzorci so bili, kljub nizki temperaturi pripravi, transparentni in fotoaktivni. Imobilizacija fotokatalizatorjev je bila uspešna na steklu kot tudi na termično neobstojnih podlagah.

Zbog velike kristalne savršenosti, toplinske stabilnosti te poželjnih mehaničkih svojstava, ali i izražene polarnosti, nanoceluloza se postavila kao potencijalno ojačavalo polimetakrilatnih matrica. Svrha ovog rada bila je ispitati utjecaj nanoceluloznog punila (celuloznih nanokristala) na raspodjelu molekulskih masa pripadajućih matrica, njihove toplinske prijelaze (temperature staklastog prijelaza), toplinsku stabilnost, svojstva površine (kontaktni kut) te mehanička svojstva pripremljenih nanokompozita. U radu su ispitani ex situ priređeni kompoziti nanoceluloze, tj. celuloznih nanokristala (1, 2,5 i 5 mas.%; 10-20 nm × 300-900 nm s udjelom kristalnosti od 92 %) s poli(metil-metakrilatom) (PMMA) i MMA/dimetilaminoetil-metakrilatnim kopolimerom (90/10 mol.%), gdje aminoskupina dodatno doprinosi polarnosti matrice. Mikrografije skenirajućeg elektronskog mikroskopa poslužile su kako bi se ustanovilo tvori li nanoceluloza aglomerate u polimetakrilatnoj matrici. Pripremljeni kompoziti su karakterizirani kromatografijom isključenja po veličini kako bi se utvrdio utjecaj nanoceluloznog punila na molekulske mase i disperznost polimernih matrica i diferencijalnom pretražnom kalorimetrijom kako bi se utvrdio pomak staklišta. Termogravimetrijska analiza provedena je kako bi se odredio utjecaj nanoceluloze na toplinsku stabilnost pripremljenih kompozita. Provedeno je mjerenje kontaktnog kuta kako bi se ocijenilo utječe li nanoceluloza na kvašenje površine kompozita vodom. Pretraživanjem lomne površine uzoraka skenirajućom elektronskom mikroskopijom pretpostavljeno je kako je sva nanoceluloza homogeno raspodijeljena kroz uzorke. Prema rezultatima diferencijalne pretražne kalorimetrije mogao se uočiti trend povećanja temperature staklastog prijelaza s povećanim udjelom celuloznih nanokristala kod kompozita s oba tipa matrica. Rezultati kromatografije isključenjem po veličini ukazuju da je prešanje na povišenim temperaturama u određenoj mjeri dovelo do blage degradacije kompozita pripravljenih s PMMA. Kod kompozita pripravljenih s kopolimerom, pronađena su dva signala; pretpostavlja da signal manjih molekulskih masa pripada neumreženom polimeru, a signal većih molekulskih masa umreženom polimeru koji je nastao u procesu prešanja. Rezultati termogravimetrijske analize potvrđuju visoku toplinsku stabilnost nanoceluloze, međutim, dodatak nanoceluloznog punila nije utjecao na temperaturu početka toplinske razgradnje. Utjecaj njenog masenog udjela u kopolimeru na toplinsku stabilnost pripremljenih kompozita nije jednoznačan; u slučaju matrice poli(metil-metakrilata) povećanje udjela nanoceluloze pomiče krivulju razgradnje prema nižim temperaturnim vrijednostima, dok je kod matrice kopolimera učinak suprotan; kompoziti s većim udjelom nanoceluloze imaju termogravimetrijske krivulje pomaknute prema većim vrijednostima. Mjerenje kontaktnog kuta ukazuje na smanjenje kontaktnog kuta s povećanim udjelom celuloznih nanokristala. Because of its high crystallinity, thermal stability and desirable mechanical properties, but also expressed polarity, nanocellulose was set up as potential reinforcment for polymethacrylate matrices. The purpose of this study was to investigate the influence of nanocellulose (cellulose nanocrystal) fillers on the distribution of molecular weights of the respective matrices, their thermal transitions (glass transition temperatures), thermal stability, surface properties (contact angle) and mechanical properties of prepared nanocomposites. This thesis included ex situ preparation of composites with nanocellulose (1, 2.5 and 5 wt%, 10-20 nm × 300-900 nm with 92% crystallinity) with poly(methyl -methacrylate) (PMMA) and MMA/dimethylaminoethyl methacrylate copolymer (90/10 mol.%) matrices. Amino group in copolymer additionally contributes to the polarity of the matrix. Scanning electron microscope micrographs were used to determine whether nanocellulose forms agglomerates in the polymethacrylate matrix. Prepared composites were characterized by size exclusion chromatography to determine the influence of nanocellulose fillers on the molecular weight and the dispersion of polymer matrices. Differential scanning calorimetry was used to determine the nanocellullse influence on the glass transition temperature. Thermogravimetric analysis was performed to determine the influence of nanocellulose on the thermal stability of the prepared composites. Contact angle measurement with water droplets was performed to assess whether nanocellulose affects the surface wetting. By scanning the surface of the samples by scanning electron microscopy, it was assumed that all the nanocellulose was homogeneously distributed throughout samples. According to the results of differential scanning calorimetry, a trend of increased glass transition temperature with increased mass fraction of cellulose nanocrystals in composites with both matrices could be observed. Size-exclusion chromatography results indicate that hydraulic pressing at elevated temperatures led to a slight degradation of PMMA-prepared composites. For composites prepared with a copolymer, two signals were found; it is assumed that the smaller molecular weight signal belongs to the non-cross-linked molecules and the signal of higher molecular weight to the cross-linked polymer that had formed during hydraulic pressing. The results of thermogravimetric analysis confirm the high thermal stability of the nanocellulose, however, the addition of the nanocellulose filler did not affect thermal decomposition onset temperature of prepared composites. The influence of its mass fraction in the copolymer on the thermal stability of prepared composites is not equivocal; in the case of the PMMA matrix, an increase in the nanocellulose content shifts the degradation curve towards lower temperature values, whereas for the copolymer matrix the opposite is the effect; composites with a higher content of nanocellulose have thermogravimetric curves shifted to higher values. Measurement of the contact angle indicates a decrease in the contact angle with an increased mass fraction of cellulose nanocrystals.

The mesh formation of single-walled carbon nanotube (SWCNT) superstructure, i.e. nano-mesh, in low- and high-density polyethylene (LDPE and HDPE) matrices was observed by using plasma etching technique and SEM analysis. Nano-mesh was established by two mechanisms: i) alignment of SWCNT bundles (forming network backbone) and ii) shish-kebab induced crystallization (forming network net). The network was formed at low SWCNT content due to the high aspect ratio of nano-filler, which additionally contributed to alignment. Established nano-mesh superstructure caused confinement effect disrupting crystallization and melting kinetics, which directly affected mechanical properties. Although mechanical properties of LDPE and HDPE nanocomposites profoundly improved, i.e. Young’s modulus increased for 230% and 30%, respectively, at only 1 wt% of SWCNTs, HDPE nanocomposites showed visible confinement that reduced effective reinforcement. It seems that HDPE nanocomposites cannot achieve full reinforcing potential since confinement effect restricts the crystal growth, which gradually reduces effective reinforcement in semi-dilute regime.

Nanokompoziti su novi materijali u kojima punilo nanometarskih dimenzija pridonosi novim, poboljšanim svojstvima polimerne matrice. U ovome radu ispitana je priprava nanokompozita poli(etilen- oksid)/fenil hepta izobutil polihedralni oligomerni silseskvioksan (PEO/fenil hib-POSS) miješanjem polimerne matrice poli(etilen-oksida) (PEO) i nanopunila fenil hepta izobutil polihedralni oligomerni silseskvioksan (fenil hib-POSS) u otopini (voda/etanol i kloroform) i u taljevini, u masenim postotcima PEO/fenil hib-POSS od 99/1, 97/3 i 95/5. Uzorci PEO/fenil hib-POSS nanokompozita dobiveni iz otopine i taljevine istraživani su diferencijalnom pretražnom kalorimetrijom u inertu. PEO je djelomično kristalni polimer s približno 70% kristalne faze. Dodatak fenil hib-POSS-a ne utječe na karakteristike DSC krivulja, odnosno na fazne prijelaze PEO-a, niti na udio kristalne faze polimera. FT-IR spektroskopijom također nije uočen utjecaj dodatka fenil hib-POSS-a na svojstva PEO-a. Nanocomposites are new materials in which fillers with nanometric dimensions contribute to the new improved characteristics of polymer matrix. In this thesis, nanocomposite preparation of poly(ethylene oxide)/phenyl hepta isobutyl polyhedral oligomeric silsesquioxane (PEO/phenyl hib-POSS) by mixing of polymer matrix poly(ethylene oxide) (PEO) with nanometric filler phenyl hepta isobutyl polyhedral oligomeric silsesquioxane (phenyl hib-POSS), was studied. The preparation was carried out in the solution (water/ethanol and chloroform, respectively) and in the melt, where PEO/phenyl hib-POSS mass ratio were 99/1, 97/3 and 95/5. The samples of PEO/phenyl hib-POSS obtained from the solution and from the melt were examined by differential scanning calorimetry in inert. PEO is partly crystalline polymer with approximately 70% of crystalline phase. Addition of phenyl hib-POSS does not affect on characteristics of DSC curves, respectively PEO phase transition nor share of polymer crystalline phase. No influence of phenyl hib-POSS addition on the PEO characteristics was observed by the mean of FT-IR spectroscopy, as well.

U radu je ispitan utjecaj monomera i oligomera poliedarskih oligomernih silseskvioksana (POSS) na dinamiku lanaca epoksidne mreže temeljene na diglicidil eteru bisfenola A (DGEBA) i poli(oksipropilen)diaminu (Jeffamine D2000). Staklišta čiste epoksidne matrice i ispitivanih nanokompozita određena su metodom razlikovne pretražne kalorimetrije (DSC). Promjene u dinamici lanaca polimera ispitane su metodom spinske probe u elektronskoj spinskoj rezonanciji (ESR). Rezultati pokazuju da nakon ugradnje monomera POSS ne dolazi do značajnijeg ojačanja epoksidne matrice. Pri većem udjelu molekula POSS dolazi do njihove agregacije čime se stvaranju šupljine u polimernoj matrici. Zbog toga se povećava gibljivost lanaca polimera te smanjuje staklište ispitivanih nanokompozita. Nasuprot tome, prisutnost oligomera POSS uzrokuje snažne interakcije sa epoksidnom matricom što se očituje velikim porastom staklišta i znatnim smanjenjem mobilnosti lanaca polimera. In this thesis, the influence of monomers and oligomers of polyhedral oligomeric silsesquioxanes (POSS) on the dynamics of epoxy network based on bisphenol A diglycidyl ether (DGEBA) and poly(oxypropylene)diamine (Jeffamine D2000) has been investigated. The glass transition temperature of pure epoxy matrix and investigated nanocomposites was determined by differential scanning calorimetry (DSC). Changes in polymer chain dynamics were investigated by spin probe electron spin resonance spectroscopy (ESR). The results show that the incorporation od POSS monomers does not lead to a significant reinforcement of the epoxy matrix. Higher amount of POSS molecules causes their aggregation and formation of cavities in the polymer matrix. As a result, the mobility of polymer chains increases and the glass transition temperature of the investigated nanocomposites decreases. In contrast, the presence of POSS oligomer causes strong interactions with epoxide matrix which is reflected in the large increase of glass transition temperature and significant reduction in the mobility of polymer chains.

Cilj ove doktorske disertacije je dobijanje srebro/polivinil-alkohol (Ag/PVA) i srebro/polivinil-alkohol/grafen (Ag/PVA/Gr) nanokompozita elektrohemijskom sintezom nanočestica srebra u PVA rastvoru, odnosno PVA/Gr koloidnoj disperziji. Elektrohemijska reakcija izvodi se pri galvanostatskim uslovima, pri čemu je količinu, oblik i veličinu nanočestica srebra (AgNPs) moguće kontrolisati izborom vrednosti gustine struje i vremena sinteze, te je međusobna zavisnost ovih parametara detaljno ispitana u ovom radu. Svojstva nanokompozita dobijenih u vidu koloidnih disperzija, filmova i hidrogelova ispitane su u cilju potencijalne biomedicinske primene... The goal of this doctoral dissertation is to obtain silver/poly(vinyl alcohol) (Ag/PVA) and silver/poly(vinyl alcohol)/graphene (Ag/PVA/Gr) nanocomposites by electrochemical synthesis of silver nanoparticles (AgNPs) in the PVA solution, or PVA/Gr colloidal dispersion. The electrochemical reaction is performed under galvanostatic conditions, whereby the quantity, shape and size of the silver nanoparticles can be controlled by selecting the value of the current density and the time of the synthesis, and the relation between these parameters is thoroughly examined in this paper. The properties of the nanocomposites obtained in the form of colloidal dispersions, films and hydrogels were examined for potential biomedical application...

Medium-density fi berboards (MDF) were produced, using two different resins of urea-formaldehyde (UF) and phenol-formaldehyde (PF) at 10 % and 8 % contents, respectively. In order to find new source of raw material to satisfy the increasing need of composite manufacturing industry, 10 % of chicken feather was added to the furnish. Moreover, nano-clay was added to investigate its potential improving effects on MDF panel properties. Results showed that panels with PF resin demonstrated significantly lower water absorption and thickness swelling values in comparison to the panels with UF resin. However, mechanical properties of panels containing UF resin were generally higher; this was partially attributed to the higher resin content. It was concluded that panels with PF resin are recommended for applications where panels may be more exposed to water and vapor. In cases where the mechanical properties are of prime importance, panels with UF resin are more preferable. NC can be recommended in panels containing UF-resin to improve the properties, while it is not recommended in panels with PF-resin. Moreover, chicken feather can be included in MDF furnish to provide part of raw materials, though its addition can have diminishing effect on the properties to some extent., Ploče vlaknatice srednje gustoće (MDF) izrađene su uz dodatak dviju različitih smola, ureaformaldehidne (UF) i fenolformaldehidne (PF), i to u udjelu od 10 odnosno 8 %. Kako bi se pronašao novi izvor sirovine i pritom zadovoljile povećane potrebe industrije kompozitnih materijala, smjesi sirovine za izradu ploča vlaknatica dodano je 10 % pilećeg perja. Nadalje, dodana joj je i nanoglina da bi se istražilo moguće poboljšanje MDF ploča. Rezultati su pokazali da su ploče s PF smolom znatno slabije upijale vodu i da im je debljinsko bubrenje u odnosu prema pločama s UF smolom bilo manje. Međutim, mehanička svojstva ploča koje su sadržavale UF smolu u osnovi su bila bolja, što je djelomično povezano s većim udjelom smole. Zaključeno je da se ploče s PF smolom preporučuju za primjenu u uvjetima veće izloženosti vodi i pari. Kada su, pak, važnija mehanička svojstva ploča, pogodnije su one s UF smolom. Nanoglina se preporučuje za poboljšanje svojstava ploča koje sadržavaju UF smolu, a ne preporučuje se za ploče s PF smolom. Nadalje, pileće se perje može dodati sirovini za izradu MDF ploča iako ono može donekle pridonijeti pogoršanju svojstava ploče.

Epoksidni nanokompoziti (NK) na bazi diglicidil-etra bisfenola A (DGEBA) pretpolimera i višefunkcionalnog poli(amidoamina) (PAA) kao umreživača su pripremljeni in situ polimerizacijom u prisustvu komercijalnih hemijski modifikovanih montmorijonita (Cloisite®30B; Cloisite®15A) i onih sintetisanih reakcijom jonske izmene sa protonovanim heksadecilaminom (HDA-Mt) i umreživačem (PA-Mt). Pri pripremi NK, 0,5–10 mas.% montmorijonita (Mt) je direktno umešavano sa rastvorom DGEBA, odnosno prethodno dispergovano u pogodnom sistemu rastvarača... Epoxy nanocomposites (CPN) based on diglycidyl ether of bisphenol A (DGEBA) prepolymer and multifunctional poly(amidoamine) (PAA) curing agent were prepared by in situ polymerization in the presence of commercial chemically modified montmorillonites (Cloisite®30B; Cloisite®15A), as well as ones synthesized by ion exchange reaction with protonated hexadecylamine (HDA-Mt) and PAA (PA-Mt). The 0.5–10 wt.% of montmorillonite (Mt) was directly mixed with DGEBA solution or previously dispersed in a suitable solvent system...

U ovoj tezi je ispitana mogućnost sinteze novih, poboljšanih biomaterijala na bazi alginata, agara i cinka, primenom biomimetičkog principa dizajna – biomineralizacije. Cilj istraživanja je bio dizajn i karakterizacija novih nanokompozitnih biomaterijala, sa potencijalnom primenom u biomedicini i pakovanju hrane... The aim of this study was to test the hypothesis whether biopolymer-based biomineralization, with essential metal salts, Zn-minerals, can be considered a good platform for designing nanocomposite biomaterials for potential biomedical and active food packaging applications...

U sredstvima lične balističke zaštite koriste se kompozitni materijali na bazi tkanina velike žilavosti i zatezne čvrstoće, poput aramidnih tkanina impregnisanih polimernim vezivom, uglavnom nekim termoplastičnim ili termoumrežavajućim polimerom. Kompoziti sa nanočestičnim puniocima su perspektivni materijali širokog spektra primene, koji objedinjuju svojstva i prednosti matrice (polimera) i punilaca. Tendencija je da se i u balističkim kompozitnim sistemima postigne maksimum ojačanja, i to uvođenjem nanočestica različitih svojstava i strukture... In the means of personal ballistic protection, composite materials based on fabric of high toughness and tensile strength are used, such as aramid fabrics, impregnated with polymeric binder, mainly some thermoplastic or thermosetting polymer. Composites with nanoparticle fillers are promising materials for a wide range of applications, which combine the properties and benefits of matrix (polymer) and fillers. There is also a tendency in ballistic composite systems to achieve maximum reinforcement by introducing nanoparticles of different properties and structures...