Abstract
In injection-moulded parts, the degree of orientation (anisotropy) varies over the cross-section. Normally, such parts exhibit a layered structure, with a biaxially oriented surface layer (stretching of the flow front during mould filling), a highly oriented shear zone, and a core region with a relatively low orientation. This paper describes a novel method to show the different morphological zones by studying the occurrence and structure of fibres formed during injection moulding of certain incompatible blends, in the present case a mixture of high-density polyethylene and a technical lignosulphonate grade (Wanin S). The polyethylene fibres formed during processing of this composite were ribbon-shaped in the surface layer (biaxial orientation), while they had a normal appearance in the shear zone. Only relatively few fibres were found in the core region. A qualitative agreement was found when the fibre character in the various layers was compared with orientation data from thermal shrinkage measurements, as obtained with pure polyethylene samples (test bars).
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Kubát, J., Månson, J.A. & Strömvall, H.E. Fibre formation in injection-moulded polyethylene-sodium lignosulphonate blends and its relationship to the morphological zones. J Mater Sci 17, 915–921 (1982). https://doi.org/10.1007/BF00540392
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DOI: https://doi.org/10.1007/BF00540392