Repairability of plastic automobile bumpers by hot gas welding

Abstract

Abstract Problems associated with the repair of fractured plastic car bumpers by traditional hot gas welding have been identified. In particular, interfacial cracks arising due to contraction stresses, weld pores, root notches, and voids in filler rods have been observed. These result in welds with inferior mechanical properties. Even so the impact properties and strength of plastic bumpers which were fractured and have been repaired by hot gas welding are likely to be acceptable for the purposes that the bumpers are intended. We have considered three materials: a polycarbonate/polyester blend, poly(butylene terephthalate), and an ethylene‐propylene‐diene rubber. Improvements in weld strength and interfacial bonding arise if a heated roller immediately following the welding torch is used to consolidate and compress the molten plastic. Porosity is reduced if the hot gas can escape easily from beneath the weld.