Development of strain induced crystallisation modelling using the SCORIM process

H. Zuidema, G.W.M. Peters, H.E.H. Meijer

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Abstract

Crystallisation of polymers is strongly influenced by the deformation and thermal history. Dependent on the amount of local strain present during processing, different crystalline structures will occur, like a spherulitical structure in regions of low strain and shish-kebab structures in the highly strained regions at the cavity walls. The resulting morphology of the product is, together with the molecular composition, the determining factor of the dimensional and mechanical properties. While standard experiments are not suited to create extreme situations concerning flow-induced crystallisation comparable with the situation during injection moulding of semi-crystalline polymers, the SCORIM process (Shear Controlled Orientation Injection Moulding) will be used to create these extremes. In this process a flow is maintained in the mould after it has been filled, during solidification/crystallisation of the polymer. As crystallisation is enhanced by the deformation of the melt, a flow in the cavity will increase the degree of crystallinity. Analysing the flow and crystallisation kinetics in this process will lead to a more detailed understanding of the flow-induced crystallisation kinetics. In literature, different models are used for the calculation of flow-induced crystallisation. However, on the one hand Nakamura-like models nor models based on statistical irriversable thermodynamics do provide information concerning the final structure, while on the other hand models with a strain/stress dependent number of nuclei result in a fluctuating number of nuclei for the SCORIM process. This would mean that after reversal of the flow, all nuclei will disappear! So far, only a phenomenological set of differential equations include the different aspects of the resulting spherulitical/shish-kebab structure. This leads to the conclusion that another type of modelling should be used, for instance, the number of nuclei dependent on the invariants of the strain.
Original languageEnglish
Title of host publicationPolymer Processing Society : annual meeting, 15th, 's-Hertogenbosch, The Netherlands, May 31 - June 4, 1999 : proceedings
EditorsP.D. Anderson, P.G.M. Kruijt
PublisherPolymer Processing Society
Publication statusPublished - 1999
Event15th Annual Meeting of the Polymer Processing Society (PPS-15) - 's-Hertogenbosch, Netherlands
Duration: 31 May 19994 Jun 1999
Conference number: 15

Conference

Conference15th Annual Meeting of the Polymer Processing Society (PPS-15)
Abbreviated titlePPS
CountryNetherlands
City's-Hertogenbosch
Period31/05/994/06/99

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