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Modification of polymer blends based on polyhydroxybutyrate and their properties
Melčová, Veronika ; Tocháček, Jiří (oponent) ; Přikryl, Radek (vedoucí práce)
Theoretical part of this work describes properties and modification possibilities of poly(3-hydroxy butyrate) (PHB) and amorphous poly(lactic acid) (PLA) and their blends. In experimental part, reactivity of Joncryl, Raschig, and phosphite reagents triphenyl phosphite, tris(nonylphenyl) phosphite, and diphenyl isodecyl phosphite with neat PLA and PHB are studied. Raschig, an oligomeric polycarbodiimide based additive, was proven to enhance melt viscosity of both polymers in amount 2%wt., therefore was used for preparation of blends in five PHB/(PHB+PLA) ratios. Samples with Raschig and corresponding non-reactive samples were studied using rheology, gel permeation chromatography and modulated differential scanning calorimetry. Results showed possible reaction of Raschig and PHB/PLA blends leading to branched structures. However, the rate of reaction is not sufficient to completely compensate decrease in viscosity due to processing degradation. Thus, non-reacted amount of Raschig remains in matrix. On the basis of these findings, it is concluded that Raschig behaves rather as a relatively effective stabilizer of rheological properties than as a reagent for the intentional modification of PHB/PLA blends’ structure. In order to study mechanical properties of these blends, samples plasticized with acetyltributylcitrate were prepared using twin screw extruder.
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Funkcionalizace polyethylenu roubováním
Hofmann, Jan ; Figalla, Silvestr (oponent) ; Petrůj, Jaroslav (vedoucí práce)
Bakalářská práce se zabývá funkcionalizací polyethylenu roubováním. Teoretická část shrnuje poznatky o různých typech kopolymerů, radikálovém roubování a faktorech, které ovlivňují vlastnosti modifikovaných polymerů a jejich biodegradabilitu. Experimentální část se zabývá modifikací polyethylenu v hnětiči za různých procesních podmínek. Hnětené směsi se skládají z polyethylenu, kyseliny polymléčné a dalších aditiv (iniciátor, stabilizátory). V průběhu hnětení jsou snímány točivý moment a teplota. Některé mechanické vlastnosti vzniklých materiálů jsou testovány na přístroji Zwick Z010. Reologické vlastnosti vzorků byly vyšetřovány pomocí indexu toku taveniny.
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Functionalization of Poly(Lactic Acid)
Petruš, Josef ; Pospíšil, Ladislav (oponent) ; Alexy,, Pavol (oponent) ; Petrůj, Jaroslav (vedoucí práce)
The theoretical part of proposed thesis describes principle of radical grafting as well as the most important controlling factors affecting reaction course. Radical grafting of poly(lactic acid) (PLA) via reactive modification is the most promising technique for the preparation of biodegradable polymeric materials with various properties. Actual knowledge of PLA modification via radical grafting in melt is mentioned in the literature review as well as its potential applications. Experimental part deals with functionalization of PLA with itaconic anhydride (IAH) via radical grafting in the melt. Grafting reaction was initiated by 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (L101). In the first part, radical grafting is investigated “in situ” using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Exothermic peak on DSC thermogram reflects grafting reaction which allows calculation of activation energy of reaction. With regard to “in situ” TGA thermogram, formation of byproducts during radical modification was observed. In the second part, functionalization of PLA was achieved in discontinuous internal mixer under defined reaction conditions which were tailored to half-life time of chosen initiator and PLA processing parameters. Reaction temperature 190 °C was calculated according to Arrhenius equation and reaction time 6 min. These conditions were considered to be convenient with respect to decomposition kinetics of L101 and suppression of PLA degradation. IAH was succesfully grafted onto PLA backbone which was proved by Fourier transform infrared spectroscopy (FTIR) due to presence of –CH2 vibrations at 2860 and 2920 cm-1. Increase of integral intensity of the absorption band centered at 1750 cm-1 proved appearance of anhydride C=O vibrations overlapped by C=O vibrations of PLA backbone. Nuclear magnetic resonance (1H-NMR) did not detect oligomeric IAH grafted onto PLA. Different concentration of reactants (0.5–10 wt % of IAH, 0.1–2 wt % of L101) was applied in order to evaluate its influence on grafting yield and the extent of side reactions such as -scission, branching and crosslinking. At high concentration of both IAH and L101, IAH homopolymerization occurs although it is neglected in the most of research works. This argument is supported by colorimetric analysis, characterization of samples prepared by polymerization of IAH under grafting conditions and thermal stability of fractions extracted from PLA-g-IAH. Radical modification of PLA improves chain flexibility due to bulky IAH which was detected as a decrease of glass transition temperature (Tg). Increased content of amorphous phase, improved hydrophilicity, branched structure and chain scission enhanced biodegradability of PLA-g-IAH compared to neat PLA. Non-radical degradation during processing was proved by change of melt behaviour. This undesired effect was suppressed by addition of chain extender with reactive epoxy groups. Reaction between epoxy groups of chain extender and carboxyl groups of PLA was proved by structure analysis and change of rheological behavior of PLA-g-IAH.
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Funkcionalizace polyethylenu roubováním
Hofmann, Jan ; Figalla, Silvestr (oponent) ; Petrůj, Jaroslav (vedoucí práce)
Bakalářská práce se zabývá funkcionalizací polyethylenu roubováním. Teoretická část shrnuje poznatky o různých typech kopolymerů, radikálovém roubování a faktorech, které ovlivňují vlastnosti modifikovaných polymerů a jejich biodegradabilitu. Experimentální část se zabývá modifikací polyethylenu v hnětiči za různých procesních podmínek. Hnětené směsi se skládají z polyethylenu, kyseliny polymléčné a dalších aditiv (iniciátor, stabilizátory). V průběhu hnětení jsou snímány točivý moment a teplota. Některé mechanické vlastnosti vzniklých materiálů jsou testovány na přístroji Zwick Z010. Reologické vlastnosti vzorků byly vyšetřovány pomocí indexu toku taveniny.
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Modification of polymer blends based on polyhydroxybutyrate and their properties
Melčová, Veronika ; Tocháček, Jiří (oponent) ; Přikryl, Radek (vedoucí práce)
Theoretical part of this work describes properties and modification possibilities of poly(3-hydroxy butyrate) (PHB) and amorphous poly(lactic acid) (PLA) and their blends. In experimental part, reactivity of Joncryl, Raschig, and phosphite reagents triphenyl phosphite, tris(nonylphenyl) phosphite, and diphenyl isodecyl phosphite with neat PLA and PHB are studied. Raschig, an oligomeric polycarbodiimide based additive, was proven to enhance melt viscosity of both polymers in amount 2%wt., therefore was used for preparation of blends in five PHB/(PHB+PLA) ratios. Samples with Raschig and corresponding non-reactive samples were studied using rheology, gel permeation chromatography and modulated differential scanning calorimetry. Results showed possible reaction of Raschig and PHB/PLA blends leading to branched structures. However, the rate of reaction is not sufficient to completely compensate decrease in viscosity due to processing degradation. Thus, non-reacted amount of Raschig remains in matrix. On the basis of these findings, it is concluded that Raschig behaves rather as a relatively effective stabilizer of rheological properties than as a reagent for the intentional modification of PHB/PLA blends’ structure. In order to study mechanical properties of these blends, samples plasticized with acetyltributylcitrate were prepared using twin screw extruder.
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Functionalization of Poly(Lactic Acid)
Petruš, Josef ; Pospíšil, Ladislav (oponent) ; Alexy,, Pavol (oponent) ; Petrůj, Jaroslav (vedoucí práce)
The theoretical part of proposed thesis describes principle of radical grafting as well as the most important controlling factors affecting reaction course. Radical grafting of poly(lactic acid) (PLA) via reactive modification is the most promising technique for the preparation of biodegradable polymeric materials with various properties. Actual knowledge of PLA modification via radical grafting in melt is mentioned in the literature review as well as its potential applications. Experimental part deals with functionalization of PLA with itaconic anhydride (IAH) via radical grafting in the melt. Grafting reaction was initiated by 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (L101). In the first part, radical grafting is investigated “in situ” using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Exothermic peak on DSC thermogram reflects grafting reaction which allows calculation of activation energy of reaction. With regard to “in situ” TGA thermogram, formation of byproducts during radical modification was observed. In the second part, functionalization of PLA was achieved in discontinuous internal mixer under defined reaction conditions which were tailored to half-life time of chosen initiator and PLA processing parameters. Reaction temperature 190 °C was calculated according to Arrhenius equation and reaction time 6 min. These conditions were considered to be convenient with respect to decomposition kinetics of L101 and suppression of PLA degradation. IAH was succesfully grafted onto PLA backbone which was proved by Fourier transform infrared spectroscopy (FTIR) due to presence of –CH2 vibrations at 2860 and 2920 cm-1. Increase of integral intensity of the absorption band centered at 1750 cm-1 proved appearance of anhydride C=O vibrations overlapped by C=O vibrations of PLA backbone. Nuclear magnetic resonance (1H-NMR) did not detect oligomeric IAH grafted onto PLA. Different concentration of reactants (0.5–10 wt % of IAH, 0.1–2 wt % of L101) was applied in order to evaluate its influence on grafting yield and the extent of side reactions such as -scission, branching and crosslinking. At high concentration of both IAH and L101, IAH homopolymerization occurs although it is neglected in the most of research works. This argument is supported by colorimetric analysis, characterization of samples prepared by polymerization of IAH under grafting conditions and thermal stability of fractions extracted from PLA-g-IAH. Radical modification of PLA improves chain flexibility due to bulky IAH which was detected as a decrease of glass transition temperature (Tg). Increased content of amorphous phase, improved hydrophilicity, branched structure and chain scission enhanced biodegradability of PLA-g-IAH compared to neat PLA. Non-radical degradation during processing was proved by change of melt behaviour. This undesired effect was suppressed by addition of chain extender with reactive epoxy groups. Reaction between epoxy groups of chain extender and carboxyl groups of PLA was proved by structure analysis and change of rheological behavior of PLA-g-IAH.
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