Effect of gate design and cavity thickness on filling, morphology and mechanical properties of microinjection moldings

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Title: Effect of gate design and cavity thickness on filling, morphology and mechanical properties of microinjection moldings
Authors: Zhang, Nan
Su, Quanliang
Choi, Seong Ying
Gilchrist, M. D.
Permanent link: http://hdl.handle.net/10197/7984
Date: 15-Oct-2015
Abstract: Miniaturized parts weighing up to tens of milligrams represent a large category of microinjection moulded products. Both miniaturization and extreme processing under microinjection moulding cause material to experience high shear rates and high cooling rates, and to have different morphology and final properties from conventional injection moulding. It also makes mould design quite challenging. This study investigates micro gate design (opening and thickness) and cavity thickness (100–500 μm) on filling, morphology and mechanical properties of Poly(ether-block-amide) miniaturized dumbbell parts. It is found that a reduction of gate size has two conflicting effects: increased shear heating increases flow length; increased cooling rate reduces flow length. Filling increases significantly with an increase of cavity thickness. In addition, skin ratio reduces from ∼70% to ∼10%, when part thickness increases from 100 μm to 500 μm. Such oriented skin layer determines molecular orientation and broadly influences Young’s modulus, elongation and yield stress. Natural aging at room temperature induces an increase of modulus and yield stress, and a decrease of strain at break. Mechanical properties of microinjection mouldings are significantly different from conventional injection mouldings and measurement at the microscale is required for successful miniaturized product design.
Funding Details: Enterprise Ireland
European Commission - European Regional Development Fund
Type of material: Journal Article
Publisher: Elsevier
Copyright (published version): 2015 Elsevier
Keywords: Micro gate design;Size-induced crystallization;Process-induce crystallization;Long-term mechanical properties;Morphology of micro scale features
DOI: 10.1016/j.matdes.2015.06.012
Language: en
Status of Item: Peer reviewed
Appears in Collections:Mechanical & Materials Engineering Research Collection

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