Improving the consistency of environmental stress cracking resistance testing for polyethylenes

Abstract This paper explores a novel modification to the Bell Test (ASTM‐D1693) for minimizing its variability in failure time by the introduction of heat notching. The new notching technique for assessing environmental stress cracking resistance was evaluated with four different grades of polyethylene and compared to results using the ASTM standard for notching. Differences in both the failure time and the associated variability were witnessed with this technique, evaluated at various annealing conditions between the cold crystallization temperature and crystal melting temperature of a polyethylene. Best results were found using the midpoint temperature between these two conditions for the heated blade. Localized elastic moduli for the notched samples were obtained by force mapping via atomic force microscopy, showing decreased crystallinity content at the point of concentrated stress was favored for more consistent failure times. The work highlights the critical nature of local phase morphology at the notch in the assessment of environmental stress cracking resistance.