Fatigue-Crack Propagation of High-Density Polyethylene Homopolymers: Influence of Molecular Weight Distribution and Temperature
نویسندگان
چکیده
The present study focuses on the influence of molecular weight distribution (MWD) crack-growth kinetics fatigue-crack propagation in high-density polyethylene (HDPE) homopolymers. Compact-tension specimens HDPE homopolymer grades, with polydispersities ranging from 2 to 45 and weight-averaged molar mass 49 450 kg/mol, are tested cyclic loading at temperatures between 23 92 °C. Through a variation sample thickness, linear elastic-fracture mechanics is shown apply for chosen geometry (compact tension). It was found that crack-propagation obey Paris–Erdogan law, which exponent m (highly) similar all grades (m = 3.9), implying prefactor A governing parameter kinetics. Relatively poor correlations observed when plotted as function both tie-molecule fraction derived theoretical model by Huang Brown, J. Mater. Sci. 1988, 23, 3648, average number effective physical cross-links per chain Tervoort et al., Macromolecules 2002, 35, 8467. far better correlation weight-average (Mw), improved further Mw corrected width MWD, taking into account z-average Mz, through ratio Mz/Mw. power-law width-corrected reveals slopes ?3.4 ?3.3, respectively. Because slip within fibrils would require transport crystalline blocks, temperature dependence fatigue-crack-growth investigated identify underlying processes. This investigation existence high-temperature low-temperature deformation process, can be related chain-slip mechanisms their respective activation energies (125 50 kJ/mole), considerably lower than required scission (430 kJ/mol). This, combined ?3.4, suggest possible connection failure craze reptation-like dynamics. Furthermore, experiments elevated selection MWD has no
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ژورنال
عنوان ژورنال: Macromolecules
سال: 2021
ISSN: ['0024-9297', '1520-5835']
DOI: https://doi.org/10.1021/acs.macromol.1c01945