Journal of Applied Polymer Science, Vol.83, No.11, 2288-2294, 2002
Effects of aging and moisture on the dynamic viscoelastic properties of oriental lacquer (urushi) film
The effects of aging and moisture on the dynamic viscoelastic properties of three oriental lacquer films were investigated. With aging over 1000 days at room temperature, the glass-transition temperature of the lacquer films (T.) shifted to higher temperatures, the maximum loss tangent (tandelta(alpha)) decreased, and the storage modulus at 20degreesC (E) increased. These changes were analogous irrespective of lacquers. With increasing moisture content, E decreased and tandelta increased at room temperature. Although the equilibrium moisture content of the virgin lacquer (sap) film was higher than that of the clear lacquer film, its E and tandelta were more stable with an increase of moisture content. It was speculated that the polysaccharides aggregated in the sap film did not effectively contribute to the mechanical properties of the film, while their hygroscopicity resulted in higher moisture content,