Effects of Recycled HDPE and Nanoclay on Stress Cracking of HDPE by Correlating \u3ci\u3eJ\u3csub\u3ec\u3c/sub\u3e\u3c/i\u3e with Slow Crack Growth

摘要

The effects of recycled high density polyethylene (HDPE) and nanoclay on the stress crack resistance (SCR) of pristine HDPE were evaluated using the Notched Constant Ligament Stress (NCLS) test. The test data were analyzed by both linear elastic fracture mechanics (LEFM) and elastic plastic fracture mechanics (EPFM). The LEFM approach uses the stress intensity factor K to define the two failure mechanisms: creep and slow crack growth (SCG). In contrast, using the J-integral in EPFM, which emphasizes the nonlinear elastic-plastic strain field at the crack-tip, revealed a short-term failure stage prior to the creep failure. In this article, a power law correlation between the fracture toughness Jc and SCG was found under a planestrain condition. Increasing recycled HDPE content lowered the SCG resistance of pristine HDPE by decreasing Jc. Adding nanoclay up to 6 wt% also decreased Jc while simultaneously, lowering the stress relaxation of nanocomposites, leading to longer SCG failure times at low J values.