Effect of thermo‐oxidative aging on the mechanical and flame retardant properties of long glass fiber‐reinforced polypropylene composites filled with red phosphorus

Abstract

In this work, the long glass fiber‐reinforced polypropylene/red phosphorus (PP/LGF/RP) flame retardant composites were prepared by melting blend. The effects of thermo‐oxidative aging on the mechanical properties, morphologies, and fire resistances of the PP/LGF/RP composites with different thermal exposure time at 140°C were investigated and discussed. The results showed that the crystallinity of PP in the PP/LGF/RP composites decreased and the mechanical properties decreased significantly with increasing the aging time. The scanning electronic microscopy photos indicated that the obvious reticular crack appeared on the surface of PP/LGF/RP composites and larger cracks appeared in local scope with an increase of aging time. The results from energy dispersive X‐ray analysis (EDAX) proved that RP migrated from the inner to the surface of the composites. And the corresponding temperatures of maximum weight loss rate (Tmax) of the PP/LGF/RP composites remained nearly unchanged, but the initial decomposition temperature (T5%) increased firstly, and then decreased. The flame retardant performances from the UL‐94 tests, limiting oxygen index, and cone calorimeter test showed that the thermo‐oxidative aging had a little effect on the flammability of the PP/LGF/RP composites. The thermal stability of PP/LGF/RP composites was improved slightly after thermo‐oxidative aging. POLYM. COMPOS., 39:2634–2642, 2018. © 2016 Society of Plastics Engineers