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Polimerni nanokompoziti su kompoziti kod kojih se barem jedna faza nalazi u nanodimenzijama. Različiti polimeri kao što su termoplasti i elastomeri mogu se koristiti za proizvodnju polimernih nanokompozita. Nanopunila mogu poboljšati mehanička svojstva samih polimernih materijala ako su manjih dimenzija od 100 nm. Tema istraživanja ovog rada je utjecaj višestjenih ugljikovih nanocjevčica (multiwalled carbon nanotubes - MWCNT) na toplinska svojstva, proces kristalizacije, mehanička svojstva te na morfologiju čistog polikaprolaktona (PCL) i nanokompozita (PCL/CNT) s različitim udjelom nanocjevčica. Nanokompoziti PCL/CNT dobiveni su na dva načina, umješavanjem MWCNT u taljevinu PCL-a u Brabender gnjetilici i dodavanjem MWCNT u otopinu PCL-a i tetrahidrofurana (THF). Toplinska karakterizacija materijala provedena je tehnikama toplinske analize: diferencijalnom pretražnom kalorimetrijom (DSC); dinamičko mehaničkom analizom (DMA). Mehanička svojstva ispitana su na mehaničkoj kidalici, a morfologija PCL i PCL/CNT nanokompozita snimljena je pretražnim elektronskim mikroskopom (SEM). Dobiveni rezultati pokazali su da je bolji način pripreme nanokompozita PCL/CNT u Brabender gnjetilici u odnosu na otopinu PCL/THF. Polymer nanocomposites are composites in which at least one phase is expressed in nanometers. Different polymers such as thermoplastic and elastomers can be used for polymer nanocomposites preparation. Nanofillers can improve mehanical properties of polymer materials if they are smaller than 100nm. The aim of this study is the influence of multiwalled carbon nanotubes (MWCNT) on thermal properties, crystallization process, mehanical properties and morphology of polycaprolactone (PCL) and nanocomposites (PCL/CNT) with different weight ratios of MWCNT. PCL/CNT nano-composites were obtained in two ways, first one was by mixing MWCNT in PCL melt in Brabender mixer and the second one was dissolving PCL in tetrahydrofuran (THF) and than adding MWCNT to solution. Thermal characterization was obtained by thermal analysis: differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA). Mehanical properties were determined with universal testing machine. The morphology of PCL and PCL/CNT nanocomposites was recorded by scanning electron microscopy (SEM). The obtained results were compared and showed that a better way of preparing PCL/CNT nanocomposites is in Brabender mixer than dissolving PCL in THF.

U ovom radu istraživan je učinak dodatka višestjenih ugljikovih nanocjevčica (MWCNT) te MWCNT-a modificiranog skupinama COOH (MWCNT-COOH) u rasponu masenih udjela od 0 do 4 % na svojstva termoplastičnog poliuretana (PU). Uzorci nanokompozita pripravljani su postupkom polaganog sušenja iz smjese poliuretana i nanopunila u acetonu pri sobnoj temperaturi. Učinak dodatka nanopunila na sferolitnu morfologiju poliuretana te raspodijeljenost nanopunila u matrici PU analizirana je optičkom polarizacijskom mikroskopijom. Toplinska svojstva u neizotermnim i izotermnim uvjetima istraživana su diferencijalnom pretražnom kalorimetrijom (DSC). Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., In this work, the influence of multiwalled carbon nanotubes (MWCNT) and carbon nanotubes modified with COOH groups (MWCNT-COOH) on the structure and properties of thermoplastic polyurethane (PU) were investigated. The samples of nanocomposite were prepared from a mixture of polyurethane and MWCNT in acetone by slow drying at room temperature. The effect of the addition of nanofillers on the spherulite structure of polyurethane and the distribution of the nanofillers in the PU matrix were analysed with optical polarization microscopy. Thermal properties in non-isothermal and isothermal conditions were investigated by differential scanning calorimetry (DSC). The results of contact angle measurement imply that modification of MWCNT surface with COOH groups changes its surface from hydrophobic to hydrophilic (Fig. 2 and Table 1). Optical polarization microscopy showed that the addition of both nanofillers disrupts the coarse spherulite morphology of the polyurethane matrix (Fig. 4 and Fig. 5). It was observed that, at the macro level, the modified MWCNT-COOH filler is better distributed in the PU matrix than is the MWCNT filler (Fig. 5). The DSC results showed that, in non-isothermal conditions, up to a certain amount, both nanofillers accelerate the crystallization of the soft segments of polyurethane. This effect is more pronounced in systems with MWCNT filler (Fig. 9). The results of the crystallization enthalpy during cooling showed that MWCNT filler, despite its worse distribution in the PU matrix, more significantly enhances crystallization of PU’s soft segment than does the MWCNT-COOH filler (Fig. 10). This conclusion can be ascribed to better compatibility between the nonpolar MWCNT filler and the nonpolar soft phase of the PU matrix, as well as to the previous scientific finding that functional groups at MWCNT surface decrease the nucleation effect of MWCNT. By analysing the melting peaks, it can be concluded that the PU systems with MWCNT compared to systems with MWCNT-COOH contain a higher proportion of less ordered crystalline soft phase (Fig. 11). In isothermal conditions, the MWCNT filler accelerates crystallization more significantly than does the MWCNT-COOH filler (Fig. 16). This work is licensed under a Creative Commons Attribution 4.0 International License.