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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.

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.

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.

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.).

Kompozitni nanodelci, ki vsebujejo superparamagnetno maghemitno jedro, prevlečeno s tanko plastjo amorfnega silicijevega oksida so zelo obetaven material za uporabo v biomedicini. Magnetno jedro omogoča manipulacijo z delci z zunanjim magnetnim poljem, medtem ko plašč amorfnega silicijevega oksida omogoča vezavo različnih molekul na njihovo površino. Vezava različnih organskih molekul, na primer zdravilnih učinkovin, zahteva pripravo nanodelcev, ki imajo na površini sloj funkcionalizacijskih molekul z različnimi funkcionalnimi skupinami. Funkcionalizacijo nanodelcev smo dosegli s kovalentno vezavo različnih silanskih molekul: (3-aminopropil)trietoksisilan (APS) in viniltrietoksisilan (VTS), na njihovo površino. Reakcija je potekla v mešanici etanola, v katerem je bila predhodno raztopljena izbrana silanska molekula, in stabilne vodne suspenzije kompozitnih nanodelcev. Vezavo različnih silanskih molekul na površino nanodelcev smo spremljali z elektrokinetičnimi meritvami in s konduktometrično meritvijo koncentracije molekul na njihovi površini. Izkazalo se je, da lahko vežemo na delce molekule APS v površinski koncentraciji, ki se sklada s koncentracijo silanolnih skupin na površini amorfnega silicijevega oksida. Composite nano-particles of superparamagnetic maghemite particles coated with a thin layer of silica are very promising material for biomedical applications. The magnetic core of the composite nano-particles allows manipulation of particles with external magnetic field while the silica shell allows additional bonding of molecules to the surface. Different organic molecules, such as medical drugs, require nano-particles with a layer of functionalization molecules with different functional groups. The functionalization of nano-particles was achieved with covalent bonding of different silanol molecules: (3-aminopropyl) triethoksysilane (APS) and vinyltriethoksysilane (VTS) to their surface. Reaction took place in a mixture of ethanol with previously dissolved silane and stable aqueous suspension of composite nano-particles. The bonding of different silanol molecules was monitored with electro-kinetic measurements and with conductometric measurements of molecules on the surface. The concentration of APS molecules which can be bondend to the surface of the composite nano-particles is in accordance with the concentration of silanol groups on the surface of silica.

V pričujočem delu sem se ukvarjala z vgradnjo ATH nanodelcev v akrilne sisteme. Nanodelci so bili sintetizirani po sol-gel postopku na Nanotesla Institutu v Ljubljani. Za karakterizacijo delcev smo uporabili različne metode. Velikost delcev smo določili z BET metodo, porazdelitev in velikost z DLS, sestavo smo proučili z XRD. Preliminarne raziskave so pokazale, da je nemogoče pripraviti utrjene nanokompozitne plošče in hkrati ohranili transmisijo PMMA, z neposrednim vnosom ATH koloida v akrilatno vezivo, pripravljeno iz MMA. Zaradi večje kompatibilnosti polimerne matrice in polnila, smo ATH nanodelce integrirali v hidrofilna veziva, izdelana iz monomerov, ki so vsebovali hidroksilno skupino. Iz HEMA, HEA in HPA monomerov smo z radikalsko polimerizacijo v 2-propanolu sintetizirali omenjena hidrofilna veziva z različnimi stopnjami konverzije, ki smo jo zasledovali z metodo določanja suhe snovi. Iz ATH koloida, hidrofilnih veziv in dodatkov smo izdelali predpolimerizacijske mešanice, ki so se med sabo razlikovale glede na uporabljeno hidrofilno vezivo in na vsebnost suhe snovi v vezivu. V naslednji fazi smo prav tako z radikalsko polimerizacijo MMA izdelali akrilno vezivo, z 20 ± 5 % vsebnostjo suhe snovi. Iz izdelanega akrilnega veziva in predpolimerizacijske mešanice smo pripravili utrjene akrilne nanokompozite v obliki 3 ± 0,2 mm ploščic. Ugotovili smo, da nanodelci upočasnjujejo hitrost polimerizacije. Izdelali smo plošče z 5 ut. % in 10 ut. % predpolimerizacijske mešanice. Nanokompozitnim ploščam smo določili mehanske, termične in optične lastnosti, ter testirali njihovo odpornost na ogenj. Ugotovili smo, da je na lastnosti utrjenih nanokompozitov vplivala tako koncentracija predpolimerizacijske mešanice, kot tudi vezivo, ki smo ga uporabili za izdelavo le-te. Izdelani nanokompoziti so bili različno odporni na ogenj. Pri spremljanju hitrosti gorenja smo opazili, da so vzorci, ki so vsebovali predpolimerizacijsko mešanico izdelano s HEMA hidrofilnim vezivom goreli počasneje. V okviru disertacije smo proučevali tudi sinergijske učinke nanodelcev ATH s komercialno dosegljivim TEP. Plošče izdelane z obema dodatkoma so v primerjavi z vzorci, ki so vsebovale le ATH nanodelce pokazale večjo odpornost na ogenj. Vzorci so goreli z zmanjšano hitrostjo ali pa so celo ugasnili. Poleg samega gorenja, ki predstavlja neposredno nevarnost, med gorenjem nastajajo tudi toksični plini, ki predstavljajo nevarnost za človeka in okolje. Zato smo se odločili in v okviru disertacije izmerili koncentracijo plina CO2 in CO med gorenjem vzorcev, ki sta izkazala največjo odpornost na ogenj. Testiranje je pokazalo, da nanodelci ATH in TEP vplivajo tako na hitrost gorenja, kot tudi na količino nastalih toksičnih plinov. V primeru uporabe omenjenih dodatkov so bile vrednosti merjenih plinov nižje. Vzorec, ki je vseboval nanodelce ATH in TEP, je med samim testiranjem celo ugasnil. Present work describes the integration of ATH nanoparticles into acrylic systems. Nanoparticles were synthesized by sol-gel procedure at the Nanotesla Institute Ljubljana. For particle characterization different methods were used. Particle size and distribution were determined using BET method and dynamic light scattering, crystallographic structures were examined by X-ray diffraction. Preliminary study clearly demonstrated that it was impossible to prepare PMMA nanocomposite sheets with integrated ATH nanoparticles while at the same time retaining the transparency of pure PMMA. To achieve better compatibility of nanoparticles and polymer matrix, ATH nanoparticles were firstly integrated into hydrophilic acrylic resin made of monomers with a hydroxyl group. From HEMA, HEA and HPA monomers during the radical polymerization in 2-propanol, hydrophilic acrylic resins with different conversions were made. The degree of conversion was followed by determination of non-volatile matter. ATH colloid, hydrophilic acrylic resin and additives were used to prepare premixes, which differed in type of used hydrophilic acrylic resin and in the degree of non-volatile matter of resin. Furthermore, during MMA polymerization, PMMA acrylic resin with 20 ± 5 % of dry matter was prepared. PMMA resin and premixes were used for the preparation of 3 mm nanocomposite sheets. Nanocomposite sheets with 5 wt. % and 10 wt. % of premix were made. Temperature and rate of polymerization were followed by temperature sensors. Integration of nanoparticles showed negative effect on the rate of polymerization. Mechanical, thermal and optical properties of cured sheets were measured and resistance to fire was tested. We have found that the properties of the nanocomposite sheets are affected both the concentration of the premix and the hydrophilic acrylic resin which was used for the manufacture thereof. During the measurements of the rate of burning it was observed that the samples containing premix manufactured with HEMA acrylic resin burned slower. As a part of the thesis we have also studied the synergistic effects of nanoparticles ATH with commercially available TEP. Nanocomposite sheets made with both additives, compared with samples that contained only ATH nanoparticles showed better resistance to fire. These samples burned at low speed or even stopped burning. Besides fire, which poses an immediate danger, toxic gases are also produced during combustion and pose a threat to human health and environment. We measured the concentration of CO2 and CO during combustion of samples that showed the greatest resistance to fire. Testing showed that nanoparticles ATH and TEP affect both the combustion and the formation of toxic gases. The sample which contained ATH and TEP nanoparticles even extinguished during the testing.

V pričujočem delu sem se ukvarjal s sintezo superparamagnetnih nanokompozitov na osnovi nanodelcev γ-Fe2O3 in PMMA. Nanodelce sem sintetiziral s koprecipitacijo Fe2+/Fe3+ ionov v vodni raztopini. Nanodelce prevlečene z oleinsko ali ricinolejsko kislino sem sintetiziral s koprecipitacijo Fe2+/Fe3+ ionov v vodni raztopini v prisotnosti oleinske oz. ricinolejske kisline. Preliminarne raziskave so jasno pokazale, da je nemogoče pripraviti superparamagnetne nanokompozite γ-Fe2O3 v PMMA matrici brez ustrezne funkcionalizacije površine magnetnih nanodelcev. Iz slik s presevnega elektronskega mikroskopa (TEM) sem zaključil, da je vzorec pripravljen z mešanje nanodelcev γ-Fe2O3 s PMMA v acetonu in kasnejšim obarjanjem polimera v vodi, fazno separiran. Vzorec je sestavljen iz aglomeratov nanodelcev γ-Fe2O3, ki niso vgrajeni v polimerno matrico. Nanokompozite sem pripravil z obarjalno polimerizacijo PMMA v prisotnosti nanodelcev prevlečenih z oleinsko kislino. Koloidno stabilni suspenziji nanodelcev prevlečenih z oleinsko kislino v n-dekanu sem dodal monomer metil metakrilat. Polimerizacijo monomera sem izvedel pri povišani temperaturi. Delež nanodelcev v nanokompozitu sem kontroliral preko razmerja nanodelci/monomer. S pomočjo TEM analize sem ugotovil, da so nanodelci homogeno porazdeljeni v polimerni matrici. Z višanjem razmerja prehaja mehanizem nastanka polimernih zrn preko homogene v heterogeno nukleacijo. Nanokompozit ohrani superparamagnetno naravo tudi ob vgradnji relativno velikega deleža vgrajenih nanodelcev, do 48 ut. %. Vgradnja velikega deleža magnetnih nanodelcev je razlog za visoko nasičeno magnetizacijo nanokompozitov, do 31 emu/g. Nanokompozitne delce sem pripravil s polimerizacijo monomera metil metakrilata v prisotnosti nanodelcev v miniemulziji. Koloidno stabilno suspenzijo sestavljeno iz nanodelcev prevlečenih z ricinolejsko kislino, ultrahidrofoba in iniciatorja v monomeru, sem dodal k vodni raztopini surfaktanta. Miniemulzijo sem pripravil s pomočjo ultrazvoka. Polimerizacijo sem izvajala pri povišani temperaturi. S spreminjanjem deleža surfaktanta sem prilagajal povprečni premer nanokompozitnih delcev v razponu med ~25 nm in ~50 nm. Zaradi visokega ζ-potenciala je suspenzija nanokompozitnih delcev v vodi koloidno stabilna. S TEM slik nanokompozitnih delcev sem ugotovil, da so nanokompozitni delci sestavljeni iz nanodelcev, ki tvorijo jedro delca in tankega sloja polimera okrog jedra. V nanokompozitne delce sem uspel vgraditi do 39 ut. % magnetnih nanodelcev, ne glede na velikost nanokompozitnih delcev. Nasičena magnetizacija nanokompozitnih delcev znaša 27 emu/g. Presented work describes synthesis of superparamagnetic nanocomposites, based on superparamagnetic γ-Fe2O3 nanoparticles and PMMA. Nanoparticles were synthesized by the coprecipitation of Fe2+/Fe3+ ions from an aqueous solution. Oleic or ricinoleic acid coated nanoparticles were synthesized by the coprecipitation of Fe2+/Fe3+ ions from an aqueous solution in the presence of oleic or ricinoleic acid. Preliminary study clearly demonstrated that it is impossible to prepare superparamagnetic nanocomposite of the γ-Fe2O3 in the PMMA matrix without nanoparticles functionalization. Sample prepared by the mixing of the γ-Fe2O3 and the PMMA in the acetone and subsequent precipitation of the polymer by water addition, was composed of two separated phases, as observed by transmission electron microscopy (TEM). The phases were identified as agglomerates of the γ-Fe2O3 which were not encapsulated by the PMMA matrix. Nanocomposites were prepared by the precipitation polymerization of the methyl methacrylate in the presence of oleic acid coated nanoparticles. Methyl methacrylate was added to the colloidal suspension of the oleic acid coated nanoparticles in n-decane and in-situ polymerization was carried out at elevated temperatures. The content of nanoparticles was controlled by varying the nanoparticles/monomer ratio. The TEM analysis showed that the nanoparticles were well dispersed in the polymer matrix. The mechanism of formation of the polymer grain changes from homogeneous to heterogeneous nucleation as the ratio is increased. Nanocomposites retained their superparamagnetic nature even when encapsulated by polymer with concentrations up to 48 wt. %. The high loading of magnetic nanoparticles resulted in relatively high saturation magnetizations of the nanocomposites, up to 31 emu/g. Nanocomposite particles were prepared using the mini-emulsion polymerization of a monomer in the presence of the nanoparticles. A colloidal suspension composed of ricinoleic acid coated iron-oxide nanoparticles, the initiator and the ultrahydrophobe in the monomer, methyl methacrylate, was added to an aqueous solution of surfactant and then ultrasonified to promote the formation of the mini-emulsion. The polymerization was initiated by raising the temperature. By changing the content of surfactant, nanocomposite particles with an average diameter ranging from 25 to 50 nm were obtained. Because of the high ζ-potential, the nanocomposite particles formed a stable suspension in water. TEM showed that the core of the prepared nanocomposite particles was composed of iron-oxide nanoparticles homogeneously distributed within a polymer matrix and a thin polymer shell. The content of magnetic nanoparticles dispersed in the polymer was as high as 39 wt. %, resulting in a high saturation magnetization of 27 emu/g.