Improving Impact Value of Interlayered Glass Fiber Chopped Strand Mat Reinforced Thermoplastic Polypropylene Externally Irradiated by Homogeneous Low Potential Electron Beam

Abstract

We propose a new method of applying homogeneous low potential electron beam irradiation (HLEBI) externally to both sides of glass fiber (GF) chopped strand mat (GF-CSM) reinforced thermoplastic polypropylene (PP) interlayered samples (CSM-GFRTP) after lamination assembly and hot press with layup of [PP]₆[GF-CSM]₅. The external process apparently improved the Charpy impact values (a_uc) over that of untreated. HLEBI dose from 0.22 to 0.43 MGy apparently enhanced the a_uc at low cumulative probability of fracture (P_f = 0.06) 40% over the untreated from 48 to 67 kJ/m². Moreover, based on the 3-parameter Weibull equation, applying 0.30 MGy HLEBI increased the statistically lowest impact value, a_s at P_f = 0 significantly 120% over that of the untreated from 29 to 64 kJm⁻². The improvements of weakest samples in the data set indicate increase in reliability and safety. The improvement in a_uc can be attributed to HLEBI generating dangling bonds in the PP polymer evidenced by an ESR peak with inflection point at B = ～322.5 mT. The HLEBI apparently acts to generate nano-compressive stresses from repulsive forces between the severed bond electrons in the PP and GFs hence strengthening the GF and PP as well as GF/PP interface causing rise in impact energy. Therefore, the external HLEBI application aims to be a viable method to increase Charpy impact value in articles of GF-CSM reinforced PP (CSM-GFRTP) for industry such as automotive, aerospace and construction.