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Effect of sub-micrometer structural features on rheology of polymer nanocomposites
Lepcio, Petr ; Chodák,, Ivan (oponent) ; doc.Ing.Marián Lehocký, Ph.D. (oponent) ; Jančář, Josef (vedoucí práce)
Polymer nanocomposites (PNCs) hold a great promise as future lightweight functional materials processable by additive manufacturing technologies. However, their rapid deployment is hindered by their performance depending strongly on the nanoparticle (NP) spatial organization. Therefore, the ability to control the nanoparticle dispersion in the process of PNCs preparation is a crucial prerequisite for utilizing their potential in functional composites. This work investigates solution blending of PNCs in a model glass forming polymer matrix, a bulk processing technique of a tailored NP spatial organization controlled by structural and kinetic variables of the preparation protocol. The presented results describe the differences between nanoparticle induced changes on the rheological behavior of a polystyrene solution under large amplitude oscillation shear (LAOS). High-affinity OP-POSS NPs seem to interact with the PS at low filler loadings and form stiffened aggregates, whereas low-affinity OM-POSS NPs remained rather uninvolved in the polymer deformation at these conditions. Furthermore, an interest was focused on the impact of the blending solvent on the NP spatial arrangement in silica/PMMA and silica/PS nanocomposites, which has already been suggested as the controlling parameter of the solid-state structure. An emphasis was put on the qualitative differences between “poorly dispersed” NP arrays which, by combination of rheological assessment and structural analysis (TEM, USAXS), were identified as chain bound clusters and two types of aggregates, one of thermodynamic and the other of a kinetic origin, which are characterized by substantially distinct formation kinetics and mismatched properties compared to individually dispersed NPs and each other. The currently observed types of NP dispersion were quantitatively linked with their rheological properties during the solution blending step and the amount of polymer adsorption and depletion attraction. The results were compared to the PRISM theory. Finally, the importance of NP spatial organization was demonstrated on the comparison of glass transition temperatures of various structures at constant chemical composition.
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Vývoj metody termoporozimetrie polymerních prášků
Urbánková, Radka ; Salajka,, Zdeněk (oponent) ; Kratochvíla, Jan (vedoucí práce)
Termoporozimetrie je metoda založená na depresi teplot tání a krystalizace a je vhodná ke stanovení velikosti malých pórů. Teplotní posun byl stanoven pomocí diferenční kompenzační kalorimetrie (DSC). Vývoj metody byl proveden na silice se známou úzkou distribucí velikostí pórů. Byla sledována řada faktorů ovlivňující depresi teplot tání a krystalizace (např. použití vhodného rozpouštědla, doba a frekvence odstřeďování, doba odpařování atd.). Práce je zaměřena především na optimalizaci podmínek na silice. Na základě stanovených optimálních podmínek na silice, bylo navrženo experimentální provedení metody pro polypropylenové prášky. Následně bylo vybráno několik polypropylenových prášků, syntetizovaných na různých katalyzátorech a stanovena jejich porozita. Morfologie a struktura polymerních prášků byly hodnoceny pomocí standardních metod. Porozita získaná pomocí termoporozimetrie byla porovnána s porozitou získanou sorpční a BET metodou.
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Effect of sub-micrometer structural features on rheology of polymer nanocomposites
Lepcio, Petr ; Chodák,, Ivan (oponent) ; doc.Ing.Marián Lehocký, Ph.D. (oponent) ; Jančář, Josef (vedoucí práce)
Polymer nanocomposites (PNCs) hold a great promise as future lightweight functional materials processable by additive manufacturing technologies. However, their rapid deployment is hindered by their performance depending strongly on the nanoparticle (NP) spatial organization. Therefore, the ability to control the nanoparticle dispersion in the process of PNCs preparation is a crucial prerequisite for utilizing their potential in functional composites. This work investigates solution blending of PNCs in a model glass forming polymer matrix, a bulk processing technique of a tailored NP spatial organization controlled by structural and kinetic variables of the preparation protocol. The presented results describe the differences between nanoparticle induced changes on the rheological behavior of a polystyrene solution under large amplitude oscillation shear (LAOS). High-affinity OP-POSS NPs seem to interact with the PS at low filler loadings and form stiffened aggregates, whereas low-affinity OM-POSS NPs remained rather uninvolved in the polymer deformation at these conditions. Furthermore, an interest was focused on the impact of the blending solvent on the NP spatial arrangement in silica/PMMA and silica/PS nanocomposites, which has already been suggested as the controlling parameter of the solid-state structure. An emphasis was put on the qualitative differences between “poorly dispersed” NP arrays which, by combination of rheological assessment and structural analysis (TEM, USAXS), were identified as chain bound clusters and two types of aggregates, one of thermodynamic and the other of a kinetic origin, which are characterized by substantially distinct formation kinetics and mismatched properties compared to individually dispersed NPs and each other. The currently observed types of NP dispersion were quantitatively linked with their rheological properties during the solution blending step and the amount of polymer adsorption and depletion attraction. The results were compared to the PRISM theory. Finally, the importance of NP spatial organization was demonstrated on the comparison of glass transition temperatures of various structures at constant chemical composition.
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Vývoj metody termoporozimetrie polymerních prášků
Urbánková, Radka ; Salajka,, Zdeněk (oponent) ; Kratochvíla, Jan (vedoucí práce)
Termoporozimetrie je metoda založená na depresi teplot tání a krystalizace a je vhodná ke stanovení velikosti malých pórů. Teplotní posun byl stanoven pomocí diferenční kompenzační kalorimetrie (DSC). Vývoj metody byl proveden na silice se známou úzkou distribucí velikostí pórů. Byla sledována řada faktorů ovlivňující depresi teplot tání a krystalizace (např. použití vhodného rozpouštědla, doba a frekvence odstřeďování, doba odpařování atd.). Práce je zaměřena především na optimalizaci podmínek na silice. Na základě stanovených optimálních podmínek na silice, bylo navrženo experimentální provedení metody pro polypropylenové prášky. Následně bylo vybráno několik polypropylenových prášků, syntetizovaných na různých katalyzátorech a stanovena jejich porozita. Morfologie a struktura polymerních prášků byly hodnoceny pomocí standardních metod. Porozita získaná pomocí termoporozimetrie byla porovnána s porozitou získanou sorpční a BET metodou.
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