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Polyurethane foams were prepared using starch as a main component of polyols and their structural, mechanical, and absorbing properties for organic solvents were investigated. Fourier transform infrared spectra showed that urethane linkage was formed by the reactions between À ÀNCO of diisocyanates and À ÀOH of polyols. When polyurethane foams were prepared at high molar ratio of À ÀNCO/À ÀOH, the unreacted À ÀNCO groups were detected. Also, urea linkage was formed by the reaction between diisocyanate and water, which was used as the foaming agent. The micrographs showed that the polyurethane foams had closed-cell structure, of which the cell size increased with À ÀNCO/À ÀOH molar ratio. The density of polyurethane foams increased with molecular weight of polyethylene glycol. The compressive moduli of polyurethane foams increased with À ÀNCO/À ÀOH molar ratio. Polyurethane foams prepared using toluene-2,4-diisocyanate as diisocyanate had the highest modulus, while those prepared using hexamethylene diisocyanate had the lowest modulus. In case of the absorbency for the organic solvents, the polyurethane foams prepared at À ÀNCO/À ÀOH molar ratio of 0.8 had the maximum absorbency. Among several organic solvents, the absorbency for dimethyl sulfoxide was the highest, while the absorbency for tetrahydrofuran was the lowest.

ABSTRACT:In this study, expanded starch/PVA/CaCO 3 blends (ESPCs) were prepared using the pilot system composed of a supermixer and a twin-screw extruder to investigate the effects of CaCO 3 as the expanding inhibitor on the structural and mechanical properties of ESPCs. The pore ratio of ESPCs with the interconnecting open-cell structure decreased with increasing CaCO 3 content and the structure of ESPCs became more compact. The inhibiting process of CaCO 3 during the expansion of starch/PVA blends was proposed and certified by FTIR spectroscopy and X-ray diffraction. At least two parts of CaCO 3 were required to obtain a sufficient inhibiting effect on the expansion. The mechanical properties of ESPCs such as tensile strength, elongation at break, modulus, and specific work of rupture were improved by the addition of CaCO 3 as the expanding inhibitor. As CaCO 3 content increased from one to four parts, the tensile strength increased 2.6-fold, from 70 to 180 kPa, whereas elongation at break increased about 1.5-fold. The moduli of ESPCs also increased with increasing CaCO 3 content.

Superabsorbent polymers (SAPs) are crosslinked hydrophilic polymers that are capable of absorbing large amounts of water. Commercial SAPs are mostly produced with acrylic acid that cannot be easily biodegraded. Therefore, in this study, polysaccharide-based SAPs using carboxymethyl cellulose as a major component were prepared. Starch aldehydes and citric acid were selected due to their environment-friendly, non-toxic, and biodegradable properties compared to conventional crosslinking agents. Starch aldehydes were prepared by periodate oxidation, which forms aldehyde groups by taking the places of C–OH groups at C-2 and C-3. Furthermore, starch aldehydes were analyzed through the change in FT-IR spectra, the aldehyde quantitation, and the morphology in FE-SEM images. In the crosslinking of polysaccharide-based SAPs, the acetal bridges from starch aldehydes led to a large amount of water entering the network structure of the SAPs. However, the ester bridges from citric acid interfered with the water penetration. In addition, the swelling behavior of the SAPs was analyzed by the Fickian diffusion model and the Schott’s pseudo second order kinetics model. The relationship between swelling behavior and morphology of the SAPs was analyzed by FE-SEM images. In conclusion, polysaccharide-based SAPs were well prepared and the highest equilibrium swelling ratio was 87.0 g/g.