Debris formation during the vibration welding of thermoplastics

Vibration welding is a common industrial technique used to join thermoplastic components. One of its drawbacks is the generation of small particulate debris during welding. Preheating the weld interface is currently the primary technique that minimizes debris formation; however, it incurs a cycle time penalty. This study is the first to examine the effect of vibration welding conditions on the formation of debris using a wide range of unreinforced and glass fibre–reinforced polypropylene polymers and compounds. The work shows that all materials form small, twisted strand-like debris particles. Generally, brittle grades form more debris than ductile materials. Surprisingly, higher weld pressures decrease the quantity of debris. The volume of debris is not greatly affected by the meltdown suggesting that debris is formed in the initial stage of the welding. The work then focused on the formation of relatively long strands, referred to as fibrils, very early in the process. The shape and texture of the fibrils are very similar to those of the debris particles suggesting that debris is related to the formation and rupture of the fibrils. A mechanism is proposed that explains how fibrils are created during welding and their relation to debris.