Tensile dilatometry of injection-moulded HDPE/PA6 blends
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In order to understand the mechanism of deformation of injection-moulded HDPE/PA6 (25 vol% /75 vol%) blends both with and without compatibilizer, the volume change has been monitored using tensile dilatometry. Dog-bone specimens were either directly moulded or cut from rectangular plaques. Both neat materials and their blends were tested. For the directly moulded dog-bone specimen, a pure shear yielding mechanism was observed for all materials tested, i.e. PA6, HDPE, and their blends in the same proportion as above. In the case of a deformable minor phase (HDPE), the dispersed phase appeared to bear its share of stress and the flow-induced orientation mimics the effect of interfacial modification. This was not the case of a rigid minor phase (glass beads) at the same concentration; the effect of surface treatment changed the mechanism of deformation from mixed mode cavitation shear yielding (45%) to almost pure shear yielding (85%). Machined specimens made of neat PA6 and HDPE deformed through pure shear yielding. The addition of 25 vol% HDPE to PA6 resulted in a mixed mode cavitation (55%)/shear yielding mechanism of deformation in the transverse direction, while in the longitudinal case, the mechanism which prevailed was almost pure shear yielding (80%). This can be attributed to the flow-induced orientation as above. When adding 10% (based on the weight of the dispersed phase) of an ionomer as a compatibilizer, the blend deformed via shear yielding (85%) and in the longitudinal direction both compatibilized and non-compatibilized blends display similar behaviour. Varying the specimen thickness by changing the mould cavity, led to a significant variation in the dilatational behaviour. Dilatometric behaviour is shown to be closely related to the morphology generated as a result of flow-induced orientation. The skin/core ratio, which is an indication of the proportion of the oriented dispersed phase to the non-oriented one, plays a key role in influencing the mechanism of deformation involved.
KeywordsCavitation Disperse Phase Minor Phase HDPE Dilatometry
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- 2.L. A. Utracki, “Polymer blends and alloys: thermodynamics and rheology” (Hanser, Munich, 1989).Google Scholar
- 13.R. J. M. Borggreve, R. J. Gaymans and H. M. Eichenwald, Polymer 30 (1989) 79.Google Scholar
- 18.I. T. Barrie, D. R. Moore and S. Turner, Plast. Rubb. Proc. Appl. 3 (1983) 365.Google Scholar
- 24.E. A. A. van Hartigsveldt, PhD. thesis, University of Delft Holland (1987).Google Scholar
- 25.H. Bertilson, B. Franzen and J. Kubat, Plast. Rubb. Process. Appl. (1991).Google Scholar
- 26.S. Fellahi, B. D. Favis and B. Fisa, SPE Antec Tech. Papers 39 (1993) 211.Google Scholar
- 27.Idem, Polymer, in press.Google Scholar
- 28.A. Meddad, S. Fellahi, M. Pinard and B. Fisa, SPE Antec Tech. Papers 40 (1994) 2284.Google Scholar
- 31.G. Menges, A. Troost, J. Koske, H. Ries and H. Stabrey, Kunstst. Germ. Plast. 78 (1988) 22.Google Scholar