Anchoring Ties: Improving Environmental Stress Crack Resistance in HDPE with Styrenic Triblock Copolymer

Postconsumer recycled plastics typically exhibit low environmental stress cracking resistance (ESCR), which limits their use in the rigid packaging industry. A styrenic triblock copolymer increased the ECSR of virgin and recycled high-density polyethylene (HDPE) to 130%. Scanning electron microscopy revealed well-dispersed styrene-b-ethylene-b-ethylene/propylene-b-styrene copolymer domains within HDPE spherulites. It is postulated that the rigid polystyrene domains, interconnected by flexible polyolefin midblocks, act as anchors that delay disentanglement and pullout of the tie molecules. Strain hardening modulus and in situ Fourier-transform infrared-tensile tests validated this reinforcing effect, indicating a promising approach to improving the recyclability of HDPE.