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Effect of cellular uniformity on the necking propagation of foam injection Molded PP/HDPE blend parts
Author(s) -
Zhou YingGuo,
Cao GangHe,
Cheng YiFan
Publication year - 2020
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.49124
Subject(s) - necking , materials science , composite material , ultimate tensile strength , high density polyethylene , polypropylene , tensile testing , scanning electron microscope , molding (decorative) , polyethylene , polystyrene , polymer
Necking propagation (NP) is an important phenomenon that is facilitated by the superductility of many materials, although necking is often considered to be a type of unstable and heterogeneous deformation under tensile loading. In this study, the NP of samples produced with injection molding of polypropylene (PP) and high‐density polyethylene (HDPE) blends with or without a blowing agent was investigated by standard tensile testing, and the foam morphology and cellular structure were characterized with scanning electron microscopy. It was found that the foam parts fabricated with the PP/HDPE blends had the ability to be superductile under a low tensile test speed, which was attributed to the necking spreading throughout the tested gauge section stably and reliably. However, the NP of the foam PP/HDPE blend samples strongly depended on the distribution of the cellular foam. To investigate the relationship between the cellular structure and NP, a design of experiment approach based on the Taguchi method was used to fabricate many samples with different foam structures. The tensile test results of these samples suggested that the cellular uniformity, which was determined based on the statistical results of the fracture surface morphology, played an important role in the NP. The results suggested that there is a close relationship between the NP and the cellular uniformity. Using nonlinear fitting, it was straightforward to obtain a model between the NP length and cellular uniformity index for PP/HDPE molded foam parts.