ENVIRONMENTAL-STRESS CRACKING RESISTANCE OF BLENDS OF HIGH-DENSITY POLYETHYLENE WITH OTHER POLYETHYLENES

A special modified tensile creep test was used to investigate the stre ss cracking behavior of various high-density polyethylenes (HDPE). Ble nds of HDPE with other HDPEs, with linear low-density polyethylene (LL DPE), and specifically with various slightly long-chain branched linea r low-density polyethylenes (HBPE) were tested for their failure times . Whereas HDPE blends, including higher-molecular-weight HDPE componen ts, yield only a minor improvement in stress cracking resistance, a co nsiderable improvement was produced when an LLDPE weight fraction of 0 .3 or more was used. Adding HBPE also improves the environmental stres s cracking resistance. Environmental stress cracking resistance improv es with increasing HBPE content, and, for a constant HBPE concentratio n, it increases with increasing octene content of the HBPE. Adding HBP E, with a low octene content, however, results in reduced failure time s of the blend compared with HDPE blends that exhibit relatively good environmental stress cracking behavior. The results are explained in t erms of the tie-molecule density.