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

Abstract

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.

Influence of Acetone and Primer on Strength and Ductility of Chlorinated Poly(vinyl chloride)

“…Such thickness was selected so that the specimens could be handled relatively easily for the mechanical testing, but still allowed saturation of the solvents in a reasonably short immersion period. The pipe was commercial CPVC 4120 SCH80 2-inch (~50 mm) pipe, which was the same grade as the one used in a previous study [ 13 ], to examine the influence of the chemical solvents on strength and ductility in the hoop direction of the pipe.…”

“…Dog-bone specimens were waterjet cut from the CPVC sheets with a gauge section of 11 mm long and 8 mm wide, and the pipe ring specimens from the CPVC pipe with dimensions same as those used previously [ 13 ]. Dimensions for these two types of specimens are given in Figure 1 .…”

“…Acetone was ACS reagent grade of from Sigma-Aldrich (St. Louis, MO, USA), purchased from the Chemical Stores at the University of Alberta. Primer used in this study is known as clear primer, purchased from McMaster-Carr which was same as the one used in the previous study [ 13 ], containing acetone of 60% by weight.…”

“…Setup for the immersion treatment was same as that used previously [ 13 ], for both dog-bone and pipe ring specimens, as depicted in Figure 2 a using a pipe ring specimen as an example. In the immersion treatment, the chemical solvents were replaced when tiny CPVC bits were seen in the solvents, so that the specimens were immersed in the relatively fresh chemical solvents.…”

“…For the pipe ring specimens, the immersion time was selected to be fixed at 30 min for both primer and acetone, in order to be consistent with that used in the previous study for the immersion treatment in primer [ 13 ]. The previous study has suggested that for this immersion period in primer, cross section of the specimens showed a core-shell structure, with the shell thickness of around 0.5 mm.…”