Assessing the slow crack growth resistance of polyethylene resins and pipe service lifetimes predictions [PE]

Many different tests and methods have been proposed to assess SCG resistance of Polyethylene (PE) resins and pipes. Among them, the PENT test has found widespread popularity and use as a measure of the Slow Crack Growth (SCG) performance of PE pipe resins. More recently, a relationship was even proposed in the literature that utilizes PENT test results to estimate the service lifetimes of PE pipe. However, our experimental data showed that the PENT test neither consistently reflects SCG performance nor correlates well with other established SCG tests such as Notch Pipe Test (NPT) or Natural Draw Ratio (NDR). Furthermore, experimental results are presented for standard PENT specimens of variable thickness, which demonstrate the dependence of the PENT failure times on specimen geometry, contrary to expectations based on the guidelines of the governing PENT test standard. The implications of the geometry dependence with respect to using PENT test results to rank SCG performance and estimate service lifetimes for PE pipe are discussed.