Study on the Allowable Temperature for Preventing Over Welding During Thermal Welding of Polyethylene Pipe

Polyethylene (PE) pipe material may degrade into lower carbon number volatiles quickly during thermal welding when the welding temperature rises up to very high temperature. However, PE may also degrade into lower molecular weight (MW) polymer when subjected to a lower temperature. As a result, determination of the allowable temperature during thermal welding is crucial for guaranteeing the quality of welding joint. In this paper, a typical commercial PE100 material was chosen to conduct thermogravimetic analysis (TGA) and gel permeation chromatography (GPC) tests. The thermal degradation behavior of PE100 was investigated in dynamic and isothermal mode. The composition of the residue after thermal degradation was also analyzed through MW and MW distribution (MWD) measurements. Based on the experimental results, the initial temperature of thermal degradation with volatilization was derived and the thermal degradation process was studied in detail. To limit the degree of thermal degradation within a certain range during thermal welding of PE pipe, the allowable welding temperature for typical commercial PE100 material was determined.