RESUMEN
A series of polyurethane hydrogel and polyurethane thermoplastic elastomer composite based separation membranes were successfully prepared via wet phase inversion method. The morphology, chemical structure, phase transition temperature and crystallinity of the polyurethane (PU) membranes were characterized by SEM, FTIR, DSC, and XRD, respectively. The SEM observation showed that the PU membranes exhibited irregular porous structure on the surface and path of the hole was flexural and asymmetrical in cross-section. The FTIR analysis demonstrated that thermalsensitive groups and pH-sensitive components (-N(CH3)-) were incorporated into the PU network. The DSC experiment and XRD experiment showed that the regular arrangement of PU network was destroyed partly due to the introduction of polyurethane thermoplastic elastomer. The equilibrium swelling ratio (ESR) and water flux (J) for PU membranes clearly decreased and increased with functional groups and sophisticated structure of PU membranes, respectively. In addition, the permeation experiments indicated that the permeation percentage (P) of the glycine was strongly affected by the external temperature and pH value.
RESUMEN
Isotactic polypropylene (iPP) is a commonly used thermoplastic polymer with many excellent properties. But high brittleness, especially at low temperatures, limits the use of iPP. The presence of transcrystallization of iPP makes it possible for fiber-reinforced iPP composites with higher strength. Bacterial cellulose (BC) is a kind of cellulose with great potential to be used as a new filler to reinforce iPP due to its high crystallinity, biodegradability and efficient mechanical properties. In this study, the iPP/BC hamburger composite was prepared by a simple hot press and maleic anhydride grafted polypropylene (MAPP) was used to improve the interface compatibility of iPP and BC. The polarizing microscope (POM) photograph shows that BC successfully induces the transcrystallization of iPP. The differential Scanning Calorimeter (DSC) date proves that the addition of BC could improve the thermal properties and crystallization rate of the composite. Especially, this change is more obvious of the iPP/MAPP/BC. The mechanical properties of the iPP/BC composites were greatly increased. This DSC date is higher than BC; we used BC particles to enhance the iPP in our previous research. The scanning Electron Microscope (SEM) analysis intuitively shows that the interface of the iPP/MAPP/BC is more smooth and flat than the iPP/BC. The fourier Transform infrared spectroscopy (FT-IR) analysis of the iPP/BC hamburger composites was shown that a new C=O group vibration appeared at 1743 cm-1, which indicated that the hydrogen bond structure of BC molecules was weakened and some hydroxyl groups were substituted after modification which can increase the lipophilicity of BC. These results indicated that the BC fiber can easily induce the transcrystallization of iPP, which has excellent mechanical properties. Moreover, the addition of MAPP contributes greatly to the interface compatibility of iPP and BC.
RESUMEN
Bacterial cellulose (BC) is a new kind of cellulose with great potential in enhancing preparation of isotactic Polypropylene (iPP) composites, which have been found with excellent performance. However, the interface compatibility between BC and iPP is poor. In this study, iPP/BC composites were prepared by solution mixing. Esterification modified BC (CO) and Maleic anhydride grafted polypropylene (MAPP) added as a compatibilizer was both used to improve the interfacial compatibility of the iPP/BC composites. The rheology and isothermal crystallization behavior of the composites was tested and discussed. The result shows that the complex viscosity and storage modulus of the composite significantly increase in the rule iPP, iPP/BC2, iPP/CO2, and M-iPP/BC3, which indicates that the compatibility of the composite increases as this rule. According to the isothermal crystallization kinetics result, the crystal growth mode of iPP was not affected by the addition of BC and the interfacial compatibility. The spherulite growth rate of the iPP/BC composite increases with increasing crystallization temperature. Especially, the value decreases as the same rule with the complex viscosity and storage modulus of the composite at the same isothermal crystallization temperature. These results suggest that the interface compatibility of iPP/BC composites is greatly improved and the interface compatibility of the M-iPP/BC3 is better than the iPP/CO2.
