Abstract
Thermal and photo-degradation of glass fiber reinforced rigid polyurethane foams (FRU) with different glass fiber lengths and different expansion ratios of matrix (PUF) have been studied.
The results obtained are summarized as follows:
(1) The reduction in flexural strength and flexural modulus by heat treatment was more remarkable for the samples containing shorter length glass-fiber.
(2) No significant difference was observed in activation energy of thermal degradation between FRU and PUF: about 12-21kcal/mole for flexural modulus, and about 12-17kcal/mole for flexural strength. With a few exceptions, the samples of higher apparent density tended to show slightly higher activation energy.
(3) The similar tendency was observed also for the decline in interlaminar shear strength by heat treatment. Probably the degradation of this type arises from both the reduction in shear modulus of matrix and that in bonding strength between fiber and matrix.
(4) The reduction in flexural properties by WOM exposure was nearly the same for FRU and PUF, but was slightly larger for the samples of higher apparent density.
(5) IR analysis proved a decrease of urethane linkage after WOM exposure.
