Scholarlink

<p>The conformity of microinjection molded components, particularly in terms of high aspect ratios, dimensional stability, tolerance accuracy, electrical integrity and mechanical performance is strongly governed by morphology distribution within the parts. This study presents a multiphysics simulation framework for predicting morphology evolution during the microinjection molding of semi-crystalline polymers. The model couples polymer viscous flow, polymer front tracking, crystallization kinetics, and viscoelastic behavior associated with molecular stretch, incorporating a nonlinear Maxwell formulation with flow-temperature-dependent relaxation time. Simulations of the mold-filling stage in stepped geometry with decreasing thickness reveal distinct morphological zones. Fibrillar structures instantly develop upon molten polymer contact with mold interfaces, while spherulites emerge in the core regions. The calculated shear rates in the thinnest section reach approximately <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:\dot{\gamma\:}\)</EquationSource> </InlineEquation>=25 000&#xa0;s⁻¹, resulting in a predicted molecular stretch ratio of Δ = 98. This intense deformation zone drives pronounced stretching and alignment of polymer chains within the skin layer, leading to the formation of oriented fibrils along the flow direction. In contrast, the core regions of the stepped parts experience much lower shear rates, corresponding to stretch ratios of Δ = 3.25 in the thickest section, Δ = 5.78 in the median section, and Δ = 6.98 in the thinnest section. Under these conditions, thermal relaxation prevails, dissipating most of the flow-induced molecular orientation and promoting the formation of spherulitic structures. Experimental observations of the skin–intermediate–core morphology exhibit strong agreement with simulation outcomes, highlighting the reliability and predictive capability of the proposed numerical framework.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Morphology prediction during microinjection molding of stepped-parts with gradually decreasing thickness

  • 期刊论文

  • 发表日期：

    2025年12月8日

查看全文
  • Anass Ben ayad,
  • Rabie El Otmani,
  • Abdelhadi El Hakimi,
  • Abdelhamid Touache,
  • M’hamed Boutaous

摘要

The conformity of microinjection molded components, particularly in terms of high aspect ratios, dimensional stability, tolerance accuracy, electrical integrity and mechanical performance is strongly governed by morphology distribution within the parts. This study presents a multiphysics simulation framework for predicting morphology evolution during the microinjection molding of semi-crystalline polymers. The model couples polymer viscous flow, polymer front tracking, crystallization kinetics, and viscoelastic behavior associated with molecular stretch, incorporating a nonlinear Maxwell formulation with flow-temperature-dependent relaxation time. Simulations of the mold-filling stage in stepped geometry with decreasing thickness reveal distinct morphological zones. Fibrillar structures instantly develop upon molten polymer contact with mold interfaces, while spherulites emerge in the core regions. The calculated shear rates in the thinnest section reach approximately \(\:\dot{\gamma\:}\) =25 000 s⁻¹, resulting in a predicted molecular stretch ratio of Δ = 98. This intense deformation zone drives pronounced stretching and alignment of polymer chains within the skin layer, leading to the formation of oriented fibrils along the flow direction. In contrast, the core regions of the stepped parts experience much lower shear rates, corresponding to stretch ratios of Δ = 3.25 in the thickest section, Δ = 5.78 in the median section, and Δ = 6.98 in the thinnest section. Under these conditions, thermal relaxation prevails, dissipating most of the flow-induced molecular orientation and promoting the formation of spherulitic structures. Experimental observations of the skin–intermediate–core morphology exhibit strong agreement with simulation outcomes, highlighting the reliability and predictive capability of the proposed numerical framework.