No.7（2004）16.Development of new natural wood adhesives using silk protein

Kensuke KAWARADA, Takahiko IIDA, Masaharu OHMI, Hiroshi TOMINAGA, Kiyoharu FUKUDA

We carried out compressive shear tests and characterization analysis of the film prepared from EIC and SF to explore the possibility of utilizing silk fibroin (SF) as a wood adhesive and to improve the water durability of the SF by adding an aqueous emulsion-type isocyanate resin (EIC). The bond strength of SF in air dry conditions was 6.1MPa and that of SF in wet conditions (immersion in 30℃ water for 3 hours) was 5.7MPa. The bond strength was modified with an increase in the EIC/SF ratios, although wood failure in all specimens were less than 10% with immersion of the specimens in 60℃ hot water for 3 hours. The results of tensile test of EIC/SF films suggested that the lower wood failure was caused by a decrease in the cohesion force of the adhesive layer through a sorption of water. The glass transition temperature of EIC/SF films shifted to a lower temperature and the thermal expansion coefficient increased as the EIC/SF ratio increased. Consequently, the crystal formation of silk fibroin including silk II formation serves as the hard segment of the EIC/SF films and EIC that reacted with water or polyols included in denatured EIC serves as the soft segment.

Keywords
Silk fibroin, Wood adhesive, Isocyanate resin, Bond strength

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