Plastics — Injection moulding of test specimens of thermoplastic materials — Part 5: Preparation of standard specimens for investigating anisotropy
ISO 294-5:2017 specifies a mould (designated the type F ISO mould) for the injection moulding of plates with a preferred size of 80 mm × 120 mm and a minimum size of 80 mm × ≥90 mm and with a preferred thickness of 2 mm for single-point and multi-point data acquisition. It has been found to provide the maximum anisotropic properties, with only a slight sensitivity to the rate of injection. Whenever possible, a two cavity mould is intended to be used. For the design of plastic parts, this will provide upper and lower bounds for the tensile properties. Matching the plate thickness to a given part thickness is not a suitable criterion because of the effect of mould filling rate and part geometry on anisotropy.
Investigation of the anisotropy of materials is a special procedure intended to provide guidance in the design of mouldings for end-use applications and is not intended as a quality control tool.
In the injection moulding of thermoplastic materials, the flow of molten polymer can influence the orientation of fillers such as fibreglass or the orientation of polymer chains, resulting in anisotropic behaviour.
For the purposes of ISO 294-5:2017, the flow direction is defined as the direction from the gate to the far end of the mould cavity and the cross direction as the direction perpendicular to the flow direction.
The type F mould is not intended to replace the type D mould used to determine the moulding shrinkage of thermoplastics.
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