Laboratory evaluation of the resistance of plastics to the subterranean termite Coptotermes formosanus (Blattodea: Rhinotermitidae)

Abstract

Since preliminary studies demonstrated unsuitability of the existing Japanese standardized methods for evaluating the termite-resistance of plastics, a new laboratory method was tested for its applicability. Assembled units, each consisting of a plastic material and a wood attachment surrounding a plastic sample, were placed around a laboratory nest of Coptotermes formosanus for 6 weeks at 28 ± 2 °C and over 80% relative humidity, and the termite attack was assessed visually. Amorphous polyamide performed best, and low-density polyethylene did worst. This new laboratory method succeeded in demonstrating termite damage to materials that are susceptible under actual service conditions, although it is not applicable to evaluating insecticide-incorporated plastics. A modified JWPA Standard No. 17 test method was employed to determine the minimum number of termites required to attack high-density polyethylene film so that it was possible to standardize the method to compare termite-resistance of non-woody materials with or without chemical treatment. It was concluded that 300 workers of C. formosanus in 12.6 cm2 of foraging area, which was equivalent to the termite density (pressure) of 24 workers cm−2 foraging area, were required for termites to attack from a straight scratched surface.