Hobbs, C B; Brown, C S (1999) Pressure/Volume/Temperature (PVT) behaviour of polymers during ultrafast cooling. NPL Report. CMMT(A)163

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Abstract

A critical parameter in the injection moulding process is the volume shrinkage of the moulding and how it is affected by pressure. The PressureN olumeffemperature (PVT) relationship for a material during processing, when known, will raise the efficiency of the operation, minimise cycle times and produce a component to tighter tolerances. This report gives a description and operation of the NPL modified SWO direct measurement machine used to measure the PVT behaviour of amorphous and semi-crystalline polymers during rapid cooling. A method to obtain, for the first time, ultrafast cooling rates similar to conditions in industrial injection moulding is shown with detailed results. The repeatability and sample variability of the results under computer control are good (coefficient of variation better than 0.5%). A procedure to obtain the contribution of crystallisation to the overall shrinkage is given. The effect of sample height and diameter is investigated. A correlation of the PVT results with other techniques is given. This work is unique in demonstrating the importance of obtaining PVT data representative of commercial injection moulding as opposed to data gathered hitherto under equilibrium conditions.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	CMMT(A)163
Subjects:	Advanced Materials Advanced Materials > Polymers
Last Modified:	10 Sep 2018 12:52
URI:	http://eprintspublications.npl.co.uk/id/eprint/1055

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