Welding Mechanisms of Plastics: A Review

Strength of welded joints is a function of technological parameters of the production process. The type of function is dependent on the welding mechanism. Different mechanisms were found under various welding conditions. The processes included in the plastic welding mechanism are divided into two groups: 1) Processes which realize the joining of the parts. 2) Processes which create conditions for the first group to proceed. The first series of processes includes: a) diffusion of macroradicals, molecular segments or molecules of the polymer which can be either in a solid, melted or dissolved state. b) convective mass transfer. c) recombination of macroradicals across the contact surface. d) physical (surface) interaction. e) any combination of processes described above. The second group contains: a) formation of the real contact surface. b) formation of the macroradicals. c) destruction and removal of inert layers which prevent real contact of active material. Each process and the conditions of its proceeding are discussed individually.