Localized effects of dynamic melt manipulation on flow induced orientation and mechanical performance of injection molded products |
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| Authors: | Gregory S. Layser John P. Coulter |
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| Affiliation: | 1. Manufacturing Science Laboratory, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015‐3006;2. Manufacturing Science Laboratory, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015‐3006Manufacturing Science Laboratory, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015‐3006 |
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| Abstract: | This study investigates the effects that dynamic melt manipulation based injection molding has on the locally induced molecular orientation and tensile strength of injection molded polystyrene. Melt manipulation refers to a process where the polymer melt is manipulated during molding beyond the extent normally encountered in conventional injection molding. The specific melt manipulation process investigated in this article is vibration assisted injection molding, where a conventional injection molding machine is augmented by oscillating the injection screw (in the axial direction) during the injection and packing phases of the molding cycle. The localized final molecular orientation and morphology that results dictates the resultant product response, and typically improved mechanical properties are observed. Specimens with molecular orientation distributed more uniformly along the gage length typically exhibited higher tensile strength than samples with a gradient of orientation along the gage length. Smaller test specimens machined along the gage length of larger molded specimens showed dramatic tensile strength increase in the regions of higher melt manipulation, further supporting the promise of this novel processing methodology. POLYM. ENG. SCI., 47:1912–1919, 2007. © 2007 Society of Plastics Engineers |
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