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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.

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250, 300 o C was conducted in order to remove non-cellulosic compounds without damaging the structure of the cellulose in jute fibers. The chemical, morphological, and mechanical aspects of prepared low-temperature pyrolyzed jute fibers were investigated by Fourier transform infrared (FTIR) spectroscopy, the wettability test in water/dichloromethane system, moisture content measurement, X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), and tensile test using universal testing machine (UTM). It was confirmed that hydrophilic compounds including absorbed water, low molecular weight compounds such as waxes, hemicellulose, and lignin were largely removed from the fibers. Increasing amounts of non-cellulosic compounds were removed as the maximum pyrolysis temperature was increased. The degree of hydrophilic nature of jute fibers were reduced by low-temperature pyrolysis and thus water absorptivity of pyrolyzed jute fibers was reduced as maximum pyrolysis temperature increased. Furthermore, XRD analysis and morphological studies by SEM indicated that the crystalline structure of native cellulose was rarely damaged after pyrolysis up to 300 o C. In case of mechanical properties, breaking tenacity and breaking strain of the fibers decreased with increasing maximum pyrolysis temperatures because flaws formed on the surface of pyrolyzed jute fibers acted as weak-links. In agreement with predictions made according to Weibull's weakest-link theory, it was found that shortened pyrolyzed jute fibers could have higher breaking tenacities compared with raw jute fibers of the same length. In addition, the compatibility with hydrophobic matrix was investigated by the mechanical properties of polypropylene (PP) reinforced with jute fibers. Consequently, it was hypothesized that low-temperature pyrolysis could be used to process raw jute fibers for use as short fiber reinforcements in fiber-polymer systems or be a simple and effective pretreatment method for a wide range of further chemical treatments.

Abstract:In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide) (PPS), as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs) via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can be seen from a Field-Emission Scanning Electron Microscope (FE-SEM) images. The thermal properties of the PPS/MWCNTs composites were characterized using a thermal conductivity analyzer, and a differential scanning calorimeter (DSC). To analyze the crystallization behavior of polymers under conditions similar with those in industry, the non-isothermal crystallization behaviors of the PPS/MWCNTs composites were confirmed using various kinetic equations, such as the modified Avrami equation and Avrami-Ozawa combined equation. The crystallization rate of PPS/1 wt % pristine MWCNTs composite (PPSP1) was faster because of the intrinsic nucleation effect of the MWCNTs. However, the crystallization rates of the composites containing covalently-functionalized MWCNTs were slower than PPSP1 because of the destruction of the MWCNTs graphitic structure via covalent functionalization. Furthermore, the activation energies calculated by Kissinger's method were consistently decreased by covalent functionalization.