Long-Term Behavior Prediction of HDPE Containing Postconsumer Recycled Material Using Stepped Isostress Method

Abstract

To predict the long-term behavior of high-density polyethylene (HDPE) drainage pipes, HDPE coupon specimens with 0%, 49%, and 98% postconsumer recycled (PCR) material content were loaded incrementally in tension following the stepped isostress method (SSM) to establish their master creep curves. A reference stress of 15% ultimate tensile strength and a dwell time of 24 h were used. The 0% and 49% PCR content specimens elongated by more than 600%, whereas the 98% PCR content specimen elongated much less and broke a few minutes after adding the final load. The trend of the SSM shift factors in terms of creep stress agreed with the Eyring equation for all the HDPE coupon specimens. From the rupture time results, it was shown that as the percentage of recycled material increased, the coupon ruptured faster. The maximum percentage of recycled material allowed in HDPE is interpolated at 57% (39%) for 50-year (75-year) service life and the corresponding linear notched constant ligament stress (NCLS) failure time is interpolated at 15.2 h (21 h).