Yoshio Hayakawa

Instrumental analyses of nanostructures and interactions with water molecules of biomass constituents of Japanese cypress

Nanostructures consisting of the biomass constituents of the denatured Japanese cypress (Chamaecyparis obtusa) were examined by instrumental analyses at multiple hierarchical levels. Delignification with NaClO2 solution smoothly proceeded to reveal a distorted cell by scanning electron microscopy; however, a trace amount of lignin still remained in the delignified sample according to attenuated total reflection infrared spectra (ATR-IR). Although hemicellulose could be removed by a treatment with NaOH solution, thermogravimetric analysis and 13C cross-polarization/magic angle spinning (CP-MAS) NMR showed a certain amount of hemicellulose remaining. Reaction of the delignified sample with NaOH solution produced a shrunken cell wall that consisted of cellulose with small amounts of lignin and hemicellulose, which were detected by ATR-IR and 13C CP-MAS NMR, respectively. These samples from which lignin and/or hemicellulose had been removed easily released water molecules, producing a decrease in the 1H signal intensity and longer 1H spin–lattice relaxation time (T1H) values in variable temperature 1H MAS NMR. The T1H values provided information about nano-scale molecular interaction difficult to obtain by other instrumental analyses and they greatly changed depending on the water content and ratio of the biomass constituents. The spin–lattice relaxation of all samples occurred via water molecules under humid conditions that provided sufficient water. Under heat-dried conditions, the spin–lattice relaxation mainly occurred via lignin for the samples with lignin remaining while it occurred via cellulose/hemicellulose for the samples without lignin. The variable temperature T1H analysis indicated that predominant spin–lattice relaxation route via lignin was caused by higher molecular mobility of lignin-containing samples compared with lignin-free samples.

Integrated analysis of solid-state NMR spectra and nuclear magnetic relaxation times for the phenol formaldehyde (PF) resin impregnation process into soft wood

The effects of phenol formaldehyde (PF) resin impregnation into Japanese cedar plates were studied by the integrated analysis of solid-state NMR spectra and relaxation times. 13C cross-polarization/magic angle spinning (CP-MAS) NMR spectra showed that PF resin permeated near carbohydrate polymers as well as lignin regions, providing hydrophobicity in a woody material. Additionally, 13C pulse saturation transfer/magic angle spinning (PST-MAS) NMR spectra revealed that the molecular mobility of cellulose endocyclic groups was suppressed by the PF resin impregnation. Spin-lattice relaxation times in the laboratory frame, T1H and T1C, for both untreated and impregnated woods decreased in humid conditions while they were increased by the PF resin impregnation. Meanwhile, spin-lattice relaxation in the rotation frame, T1ρH, decreased in humid conditions as well as being a result of the PF resin impregnation. According to the tendencies of the T1H, T1C, and T1ρH values associated with the PF resin impregnation, although faster molecular motions of lignin OCH3 group were increased in the MHz frequency range, slower molecular motions of the cellulose ring were suppressed in the kHz frequency range, which confirmed the result from the 13C PST-MAS NMR spectra.

Effects of Additives on Tensile Properties of Polyhydroxyalkanoate/Polycaprolactone Polymer Blends

Bioplastics have attracted attention over the years from a perspective of environmental protection. Recently, attention is focused on bioplastics derived from inedible objects. Polyhydroxyalkanoates (PHAs) are known as a microbial origin plastic and expected to deal effectively with the food security issue. In this study, in order to use PHA for industrial and machinery parts and products, polycaprolactone (PCL) was blended with a PHA-based pellet to improve ductility and tensile strength. The effects of additives on tensile strength and elongation at break, dynamic tensile tests of the polymer blends were examined using split Hopkinson bar (SHPB) method at high strain rates.

Anti-Staining Polymer Composites Consisting of a Methacrylic Resin Matrix Containing Biphenyl and Fluorinated Moieties

Methacrylic monomers with biphenyl cores and those with fluorinated substituents were copolymerized to afford fluorinated composites having good mechanical properties and inertness. Adding a large amount of silica fillers to the polymer precursors followed by molding and complete thermal curing gives polymer composites that can be used as an artificial tooth material with improved durability and anti-fouling properties.