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2 2010

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Structure of gas-assisted injection moulded parts

Stachowiak T., Jaruga T.

Journal of Achievements in Materials and Manufacturing Engineering

2010

Vol. 38, nr 2

139-145

Purpose: The purpose of this research was evaluation of the structure in the cross-section of gas-assisted injection moulded parts. The parts investigated were stroller handles made from polypropylene. Design/methodology/approach: Polymer structure was observed in the cross-section using the optical microscope. The microtomed slices cut from the manufactured parts were observed in polarized light. The parts obtained with different injection moulding temperature values were tested. Findings: was found that spherulites size differs in the cross section. A big gradient of spherulites is observed in the area near the skin while the spherulites contacting the gas channel are of similar size - like those in the part centre. Research limitations/implications: The investigation is limited to semi-crystalline polymers, like polypropylene. In case of amorphous polymers spherulitic structure does not occur. Practical implications: The investigation results can contribute to the improvement of the knowledge about gas-assisted injection moulding and can also be helpful in selection of proper injection moulding parameters, in order to obtain good polymer structure in the part. Originality/value: Gas-assisted injection moulding is a non-conventional manufacturing process. Investigation in this field is not so common like in conventional injection moulding that has much longer history.

Influence of the processing conditions on the dynamic mechanical properties of gas assisted injection moulded parts

Postawa P., Stachowiak T., Jaruga T.

Archives of Materials Science and Engineering

2010

Vol. 44, nr 2

104-111

Purpose: The main purpose of this research was the estimation of the influence of processing conditions on dynamic mechanical properties moulidings made by Gas-Assisted Injection Moulding technology (GAIM). The research samples were cut from children cart holder - part made by gas-assisted injection moulding and tested using DMTA method. Design/methodology/approach: One of the modern testing methods was used - Dynamic Mechanical Thermal Analysis which is used very often to determinate dynamic mechanical properties and transformations of the structure of polymers and composites as well as parts manufactured from these materials. Findings: The impact of processing conditions used for manufacturing the parts made by gas-assisted injection moulding technology on mechanical properties of these parts were examined. The differences in storage modulus E' and loss factor tand were investigated. During the tests three of processing conditions were changed, on the base of the experimental plan generated in STATISTICA software, in Design of Experiment module. Research limitations/implications: The differences in storage modulus - E' and mechanical loss factor tgd were presented. The research carried out was limited to one material (Copolymer of polypropylene and polyethylene PP/PE included 10-14% of PE fraction) however during investigations some of processing conditions were changed. Practical implications: Received and presented results are very useful from the point of view of industrial applications and they can contribute to the quality improvement of the parts obtained using gas-assisted injection moulding technology. Gas flow in melt polymer in GAIM technology is very unpredictable and it causes many defects in produced parts. Originality/value: A new approach to the estimation of mechanical properties of moulded parts, produced using GAIM technology, gives information about the influence of the processing conditions on mechanical properties and quality of the parts.