Strength and Ductility Loss of CPVC Pipe Due to Exposure to Primer

This paper investigates the influence of primer on mechanical properties and fracture behavior for ring specimens, prepared from the commercial chlorinated polyvinyl chloride (CPVC) pipe. After immersing the specimens in primer for 30 min, the specimens were dried for eight different periods, ranging from half day to 113 days, and then fractured in tension along the hoop direction. The results suggest that the longer the drying time, the higher the recovered strength. After the longest drying time of 113 days, the primer-affected-zone showed strength recovery up to 63% of the strength for the virgin pipe. However, such a level of recovery cannot be achieved for ductility. The examination of specimens indicated that the exposure to primer created a core–shell structure on the cross section, of which the area ratio was independent of the drying time. It is believed that exposure to primer caused swelling and formed the shell region. The presence of the shell region has two roles in the ductility reduction. One is to provide multiple sites along the border between the shell and the core regions for crack initiation and the other to enhance stress concentration at the crack tip. This paper concludes that exposure to primer in the solvent welding process may reduce ductility of the CPVC pipe, thus affecting its resistance to slow crack growth in long-term applications.