Relationship between structure and properties of reprocessed glass fiber reinforced flame retardant poly(butylene terephthalate)

Abstract

Abstract Considering environment protection and economic requirements, the reuse of glass fiber reinforced flame retardant PBT (GFFRPBT) is of significant importance. In this paper, the properties of reprocessed GFFRPBT (RGFFRPBT) including rheological, mechanical, thermal and flame retardant properties were evaluated. To explore the relationship between structure and properties of RGFFRPBT, the carboxyl content and intrinsic viscosity of PBT, average length of glass fiber and its distribution, and the microscopic appearance of RGFFRPBT were investigated. The results demonstrated that when GFFRPBT was injection molded for five cycles, the intrinsic viscosity of PBT, average length of the glass fiber and the percentage of glass fiber length, which was higher than critical length decreased, whereas, the carboxyl content of PBT increased significantly. The rheological and mechanical properties became sensitive to these variations: the shear viscosity, impact strength, tensile and flexural strength of RGFFRPBT decreased. Furthermore, the influence of degradation on the PBT molecular weight and the glass fiber length after the reprocessing cycles were negative on the thermal properties of RGFFRPBT. However, the flame retardant properties of RGFFRPBT was independent on the degradation; RGFFRPBT with five injection molding cycles could achieve a UL-94 V-0 classification 32.0 LOI, and pass the GWIT (775 °C) test. The results showed that, when GFFRPBT was reprocessed twice, its properties matched the requirements of electronic and electric fields well.