GB/T 17037.5-2020 Plastics—Injection moulding of test specimens of thermoplastic materials—Part 5:Preparation of standard specimens for investigating anisotropy

Scope

This part of GB/T 17037 specifies the molds (F-type GB/ISO molds) used for injection molding rectangular plate-shaped specimens to obtain single-point and multi-point data. The minimum specimen size is ≥90 mm × 80 mm, with the preferred size being 120 mm × 80 mm and the preferred thickness being 2 mm. It has been found that specimens of this size can provide the maximum anisotropic properties and are only slightly sensitive to injection rates. The use of two-cavity molds is preferred. For the design of plastic parts, this will provide an upper and lower limit for tensile properties. Since the mold filling rate and the geometry of the parts affect anisotropy, it is not appropriate to match the thickness of the injection molding specimens with the thickness of a given part.
The study of material anisotropy is a method used to guide mold design rather than for quality control.
In the injection molding process of thermoplastic plastics, the flow of molten polymers can affect the orientation of fillers such as glass fibers or the orientation of polymer chains, which will lead to material anisotropy.
In this part, the flow direction is defined as from the gate to the far end of the mold cavity, and the transverse direction refers to the direction perpendicular to the flow direction.
The F-type GB/ISO molds are not intended to replace the D-type molds used for determining the shrinkage rate of thermoplastic molded specimens.
This part is applicable to the injection molding of reproducible rectangular plate-shaped specimens made of thermoplastic materials.

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