Poly(L-lactic acid) (PLLA) filament fibers were prepared by one-step melt spinning process and the effects of variations in take-up speed on their thermal properties, mechanical properties, and crystalline structures were investigated. Differential scanning calorimetry (DSC) results revealed that the PLLA fibers showed multiple melting peaks and that the melting peak appearing at a lower temperature moved lower while that at a higher temperature moved higher with increasing take-up speed. The glass transition temperature (T g ) obtained from dynamic mechanical analysis (DMA) increased with increasing take-up speed. The tenacity increased and the boiling water shrinkage (BWS) decreased with increasing take-up speed. However, these mechanical and thermal properties were stabilized at take-up speeds over 3500 m/min. The melt-spun PLLA fibers of this study showed an a-form crystal structure which was not affected by the take-up speed. The change in the tendency of the thermal and mechanical properties at around 3500 m/min did not appear to result from the change in crystal form but rather from the change in crystallite size and crystallite orientation.

Polyvinyl alcohol (PVA) nanocomposites were made using two different cellulose nanocrystals (CNCs). Sugarcane bagasse‐based CNC and a commercial CNC were used in preparing nanocomposites. Both types of nanocomposites were prepared by solution casting method at 5 wt% CNC. PVA and nanocomposites films were also stretch‐drawn four times to study the nature of reinforcement by two different CNCs. Fourier transform infrared spectroscopy was used to examine functional group characteristics. Nanocomposite morphology and crystalline structures were analyzed using a scanning electron microscope and X‐ray diffraction, respectively. Thermogravimetric analysis and differential scanning calorimetry were used to study thermal properties. Tensile properties were used to study mechanical properties. Commercial CNC reinforcement improves the tensile properties of PVA. However, laboratory CNC reinforcement decreases the tensile properties of PVA due to nanocrystal agglomeration and uneven dispersion. All stretch‐drawn nanocomposite films showed a significant increase in tensile strength and modulus values at the expense of strain at break. Water absorption of PVA/commercial CNC nanocomposites was slightly higher than that of pure PVA.

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This study investigated the effects of N-vinyl-2-pyrrolidone (NVP) and methacrylic acid (MA) comonomers on the curing characteristics and properties of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel for soft contact lenses. A real-time temperature measurement system was devised and the exothermic behaviors of hydrogel contact lenses comprising PHEMA, P(HEMA/NVP), and P(HEMA/ MA) during oven-curing condition were analyzed. The results of the real-time temperature measurement were compared with the experimental analysis by using differential scanning calorimetry at different heating rates. NVP and MA content changes affected the HEMA-based hydrogel's equilibrium water content (EWC), contact lens diameter, and gel fraction. HEMA-based hydrogel sheets with varying NVP and MA contents were fabricated and mechanically characterized. The temperature at which the exothermic reaction occurred varied depending on the type of added comonomer and the exothermic reaction of HEMA containing NVP was delayed. When NVP was added, the mechanical strength and EWC were lower than when MA was added. In order to maintain the mechanical properties while improving the equilibrium moisture content of the lens, it was found that the use of MA is more advantageous than the use of NVP.