Thermal and Photo-Degradation Behaviors of Glass-Fiber Reinforced Rigid Polyurethane Foam

Abstract

Thermal and photo-degradation of rigid polyurethane foams (PUF) and glass fiber reinforced rigid polyurethane foams (FRU) have been studied.It was found that FRU and PUF showed the nearly the same degradation behavior for flexural properties. In general, slightly higher degradation was observed with samples of lower expansion ratio, higher apparent density and containing glass fiber of shorter length.Measurement of interlaminar shear strength of heat-treated samples suggested that reduction in this property would be ascribable to the reduction in both the shear modulus of matrix and the bonding strength between matrix and fiber. No significant difference was observed among the types of samples in the degradation behaviors for flexural properties after WOM exposure, but samples of higher apparent density tended to show a slightly higher degradation. IR analysis revealed that some of the urethane linkages contained have been lost after WOM exposure.

Long-Term Durability of Fiber/Matrix Interfacial Bonding in Hygrothermal Environments

“…or where k * = k S~ ^-1 and is termed the effective rate constant of bond strength loss. Similar assumptions have been made in an investigation of the heat-induced degradation of polymers, where the service lives of the polymers in question were also assessed on the basis of kinetic theory[10].In the form above, Equation (5b) describes a reaction where FM complexes are assumed to interact until no stable FM complexes remain, or the interfacial bond strength equals zero. However, it is suggested that it is more realistic to describe the interfacial bond as a collection or a spectrum of bond or complex types, each requiring a different amount of energy (activation energy) in order to interact with water.…”