This study investigated the effects imparted to paper handsheets by the addition of reed cellulose nanofibrils (RCNF) and ultrasonic treatment of the handsheets. RCNF addition, especially when combined with ultrasonic treatment, increased the density and tensile strength of the handsheets. The tensile strength increased from 38.9 to 62.6 N・m/g, when 5 wt% RCNF were added and ultrasonic treatment was performed for 20 min. Basically, the increase in tensile strength was due to an increase in the inter-fiber bonding strength, which conformed to the Page equation. The addition of RCNF decreased the number of voids at the handsheet surface and increased the inter-fiber bonding, as confirmed by scanning electron microscopy images. The number of such voids was further reduced and inter-fiber bonding was increased by the ultrasonic treatment.
Paramylon—a β-1,3-glucan photoproduced by Euglena—is a promising raw material for bio-based plastics. Three kinds of paramylon ester derivatives—paramylon propionate (PaPr), paramylon butyrate (PaBu), and paramylon valerate (PaVa)—were synthesized to manufacture melt-spun fibers. The melt processing temperatures were determined by combining differential scanning calorimetry (DSC) and a melt flow test. The molecular orientation, crystallinity, and tensile properties of the melt-spun fibers were investigated using a polarized optical microscope (POM), wide-angle X-ray diffraction (WAXD), and tensile testing, respectively. The POM revealed that the PaPr molecular chains were aligned along the spinning direction, despite variation in the take-up rate. However, WAXD confirmed that crystallization only occurred in PaPr fibers spun at a higher take-up rate of over 108 m/min, suggesting that crystallization is induced by high shearing force. This phenomenon seems to be due to the rigid mainchain structure consisting of pyranose rings. With further annealing of the PaPr fibers, the tensile strength increased with an increase in crystallinity. These tendencies were also observed in the PaBu and PaVa melt-spun fibers. The melt-spun fibers of paramylon ester derivatives were manufactured from powders without any additives.
The effects of melt-spinning speed (400–1200 m/min) on fiber structure development after necking were analyzed by wide-angle X-ray diffraction (WAXD) / small-angle X-ray scattering (SAXS) images taken with the time resolution of 0.19–0.34 ms during continuous drawing under the same drawing stress. Whereas an a*-axis oriented crystal and a low-oriented long-period structure was formed at lower speeds, a c-axis oriented crystal and highly oriented long-period structure were formed at higher speed. The long-period structure and low-oriented crystal survived for several hundred microseconds after necking, and after the breakdown of that structure, a highly c-axis oriented long-period structure and mesophase were reconstructed. A longer time was required for the structural change in the fibers spun at lower speed, likely because of stress bearing of the surviving a*-axis oriented crystals.