INVESTIGATION ON THE ALLOWABLE TEMPERATURE DURING ELECTROFUSION WELDING OF POLYETHYLENE PIPE

摘要

Polyethylene (PE) pipe material may degrade into lower carbon number volatiles quickly during the electrofusion welding process when the welding temperature rises up to more than about 370°C. Meanwhile, PE may also degrade into lower molecular weight (MW) polymer when subject to a lower temperature. As a result, the allowable temperature during electrofusion welding is uncertain. In this paper, a typical PE100 material was chosen to conduct thermogravimetic analysis (TGA) and Gel permeation chromatography (GPC) test. The thermal degradation behavior of PE100 was investigated in Dynamic and isothermal mode. And the composition of the thermal degradation residue was determined through MW and molecular weight distribution (MWD) measurements of the residue. 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 thermal degradation degree of PE in a required range in thermal welding process, the preliminary allowable welding temperature for typical commercial PE100 material was determined. In addition, some regular information was obtained, which could promote the ultimate determination of the allowable welding temperature.