InImpact: The Journal of Innovation Impact

Publisher Future Technology Press
Vol. 7 No. 2 KES Transactions on SDM I - Sustainable Design and Manufacturing 2014
Volume Editors KES International
Journal ISSN 2051-6002
 
Article TitleStudying Microstructure and Crystallinity of Polypropylene in an Injection Moulded Medical Bin Lid
Primary AuthorShahid Mehmood, Advanced Sustainable Manufacturing Technologies (ASTUTE)
Other Author(s) 1Cris Arnold; David Bould; Nick Lavery; Johann Sienz; John Pittman
Pages 172 - 183
Article ID sdm14-073
Publication Date 01-May-16
Abstract Properties of injection moulded parts such as crystallinity and size of spherulite are strongly influenced by processing parameters. A polypropylene (PP) sharps bin lid manufactured via injection moulding shows a variable distribution of temperature along the surface on ejecting at the end of the moulding cycle. This discrepancy subsequently necessitates the characterization of crystallinity and spherulite size for the bin lid at its face and corners. DSC, polarized optical microscopy and scanning electron microscopy were used for this analysis. Results of DSC analysis reveal that crystallinity does not change throughout the bin lid and its average value for corner and face is approximately 30 %. Use of the etchant to reveal spherulites in PP and low voltage SEM analysis has proven to be an efficient method for microstructural analysis in polymers and does not require gold coat to be applied on the polymer. POM images of slow cooled PP thin films (2 ?C/mins approximately) reveal comparatively larger spherulites (order of 50 Ám) compared to fast cooled (3 ?C/sec approximately) thin films (a few microns). This shows that microstructure can be tailored by changing the cooling rate in injection moulding to achieve an optimum set of properties. In corner samples, the relative fraction of larger spherulites is higher than in face samples, which is attributed to the relatively slow cooling in this region. Spherulites are bigger (1.5-3 Ám) at the top surface and there is a slight inclination towards a decrease in size of spherulites through the sections.

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