The hot compaction of 2-dimensional woven melt spun high modulus polyethylene fibres

Abstract

In this paper we describe the production, properties and morphology of hot compacted 2-dimensional woven high modulus polyethylene fibres. The aims of the work were to establish the optimum conditions for production of the compacted woven PE sheets using a combination of mechanical measurements at Leeds and morphological investigations at Reading. This joint approach had proved very successful in a previous study on the compaction of unidirectional arranged PE fibres, where the optimum compaction temperature was established as 138°C, where ∼10% of the original fibres were melted. Morphological studies clearly showed that the melted material had recrystallised, epitaxially, onto the original fibre backbones, forming a coherent network to bind fibres into a continuous structure. The current studies, using the woven PE material, showed that a higher temperature was needed to fill all the space between the woven polyethylene fibres, and so produce a coherent material. Peel tests, where two layers of cloth are compacted together and then pulled apart, were carried out over a range of compaction temperatures to measure the interlayer bond strength; this increased with increasing compaction temperature. Significantly, reasonable bond strengths were established at the optimum temperature established for the unidirectional samples (138°C measured on the mould or 136°C in the centre of the fibre assembly) which produces ∼10% melted and recrystallised material, although a higher interlayer strength was measured at higher temperatures where more of the melted phase was produced. Morphological investigations of woven samples with ∼10% melted material, showed that while the individual fibre bundles were well bonded, not all of the complicated junctions between the fibre bundles in the woven network were completely filled with melted and recrystallised material, and that a temperature 2°C higher than for 1D compactions was probably optimum. The optimum temperature was found to fall very close to the temperature at which complete melting of the fibre occurred.