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The consequences of rapid processing techniques on the physical properties of plastics components.

Dawson, A; McCalla, B*; Brown, C S; Mulligan, D R; Crocker, L E (2003) The consequences of rapid processing techniques on the physical properties of plastics components. NPL Report. MATC(A)150

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During the injection moulding process, it is important to cool the moulded part as rapidly as possible to reduce cycle times and to maximise equipment utilisation. The rate at which a polymer is cooled during injection moulding will directly affect the morphology of the polymer and therefore the physical properties of the moulded part. This report gives a description of several measurement techniques used by NPL Materials Centre to measure the physical properties of amorphous, filled and unfilled semi-crystalline polymers after rapid processing. The techniques used were pressure/volume/temperature (PVT), differential scanning calorimetry (DSC), thermal conductivity (TC), tensile testing, polarised light microscopy and sink mark characterisation. In addition some mathematical modelling work has been carried out. The results presented for rapidly cooled polymers include mechanical properties, a comparison of the properties of a polymer/clay nano-composite with the virgin polymer plus crystallisation and latent heat effects. Thermal conductivity data is also reported. Polymers were cooled at rates approaching those of the injection moulding process using methods developed at the NPL Materials Centre or by injection moulding at the Wolfson Centre for Materials Processing, Brunel University. The injection moulding process used either direct cooling or pulse cooling - a recently developed cooling method designed to further reduce injection moulding cycle times. A comparison of tests on the physical properties of polymer samples moulded using the direct and pulse cooling methods is given. Also included is a study of the effect of adding thermally conducting fillers to semi-crystalline polymers to reduce injection moulding cycle times. This work provides a wide range of physical property data for polymers that have been cooled at very fast cooling rates and is more representative of commercial injection moulding than data gathered hitherto under equilibrium conditions. Pulse cooling brought about a 20% reduction in cycle time over direct cooling for the moulded polypropylene parts with no significant degradation in physical properties. Addition of nano-clay particles to nylon 6 increased the processability window of the nylon 6. Addition of undiluted aluminium filler in polypropylene achieved a 60% reduction in cycle time compared to unfilled polypropylene.

Item Type: Report/Guide (NPL Report)
NPL Report No.: MATC(A)150
Subjects: Advanced Materials
Advanced Materials > Polymers
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/2852

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