Abstract
AbstractThe effects of melt cooling rate on the morphology and environmental stress cracking resistance (ESCR) of a commercial‐grade high‐density polyethylene (HDPE) were investigated by DSC, WAXS, Raman spectroscopy, DMTA, microhardness, and standard Bell test. The results showed exclusion of short chain branches from the crystallites leading to their perfection by decrease in the melt cooling rate. Accordingly, samples' ESCR increased because of the aforementioned crystal thickening. In addition, quantitative evaluation of crystal strength was performed for the first time by microhardness technique. Crystal strength or the required energy for plastic deformation of unit area of the crystals, Δh·ℓc, complemented crystal thickening hypothesis. The product of Δh and average crystal thickness, ℓc, was also proportional with storage modulus of the samples at ESCR test temperature. The evaluation of the results using the recently proposed model based on the analogy of crack growth through amorphous phase of semicrystalline polymers in harsh environments with crack growth at adhesive polymer–substrate interfaces showed reasonably good correlation. Finally, the comparison of literature and current research data based on the new model delineated new directions for phenomenon generalization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
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