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Vliv chemické struktury změkčovadla na vlastnosti bioplastu na bázi polyhydroxybutyrátu
Stehnová, Ivana ; Alexy, Pavol (oponent) ; Přikryl, Radek (vedoucí práce)
Diplomová práce se zabývá změkčováním poly(3-hydroxybutyrátu), kyseliny polymléčné a jejich směsi. Zjišťuje vliv chemické struktury změkčovadla na mechanické vlastnosti této polymerní směsi i na jeho difúzi z ní. Byla syntetizována změkčovadla na bázi oligomerních polyadipátů, citrátů, polylaktidu a esterů kyseliny 2-ethylhexanové s poly(ethylenglykolem). Distribuce molekulových hmot-ností syntetizovaných změkčovadel byla stanovena pomocí gelové permeační chromatografie. Poly(3-hydroxybutyrát), kyselina polymléčná i jejich směs byly měkčeny syntetizovanými a komerčními změkčovadly. Z komerčních byla vybrána změkčovadla na bázi citrátů a esteru kyseliny 2-ethylhexanové s poly(ethylenglykolem). Pomocí termogravimetrické analýzy byla studována termická stabilita vybraných komerčních změkčovadel v kyselině polymléčné. Sledována byla také difúze změkčovadel z poly(3-hydroxybutyrátu), kyseliny polymléčné a z jejich směsi při 110 °C. Pomocí tahové zkoušky byly testovány mechanické vlastnosti připravených směsí. Téměř všechna změkčovadla vykazovala ve směsi pozitivní změkčující efekt. Nejvyšší tažnost byla zaznamenána u směsi s komerčním acetyltributylcitrátem, u níž tažnost dosáhla 328 % oproti 21 % pro neměkčenou směs.
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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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Vliv chemické struktury změkčovadla na vlastnosti bioplastu na bázi polyhydroxybutyrátu
Stehnová, Ivana ; Alexy, Pavol (oponent) ; Přikryl, Radek (vedoucí práce)
Diplomová práce se zabývá změkčováním poly(3-hydroxybutyrátu), kyseliny polymléčné a jejich směsi. Zjišťuje vliv chemické struktury změkčovadla na mechanické vlastnosti této polymerní směsi i na jeho difúzi z ní. Byla syntetizována změkčovadla na bázi oligomerních polyadipátů, citrátů, polylaktidu a esterů kyseliny 2-ethylhexanové s poly(ethylenglykolem). Distribuce molekulových hmot-ností syntetizovaných změkčovadel byla stanovena pomocí gelové permeační chromatografie. Poly(3-hydroxybutyrát), kyselina polymléčná i jejich směs byly měkčeny syntetizovanými a komerčními změkčovadly. Z komerčních byla vybrána změkčovadla na bázi citrátů a esteru kyseliny 2-ethylhexanové s poly(ethylenglykolem). Pomocí termogravimetrické analýzy byla studována termická stabilita vybraných komerčních změkčovadel v kyselině polymléčné. Sledována byla také difúze změkčovadel z poly(3-hydroxybutyrátu), kyseliny polymléčné a z jejich směsi při 110 °C. Pomocí tahové zkoušky byly testovány mechanické vlastnosti připravených směsí. Téměř všechna změkčovadla vykazovala ve směsi pozitivní změkčující efekt. Nejvyšší tažnost byla zaznamenána u směsi s komerčním acetyltributylcitrátem, u níž tažnost dosáhla 328 % oproti 21 % pro neměkčenou směs.
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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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