| Summary: | Degradation of poly-para phenylene terephthalamide (PPTA) fibres during the manufacture of carded and hydroentangled fabric is investigated. During PPTA fibre processing operations such as fibre opening and carding, the material is subjected to applied mechanical forces resulting from interactions with machine surfaces and inter-fibre friction. Additionally, post-industrial and post-consumer sources of PPTA fibre are exposed to UV irradiation, which also has potential to influence fibre properties. The degree to which such agencies of degradation are encountered during fabric manufacture can influence fibre morphology and ultimate nonwoven fabric properties is not fully understood. This question is relevant both to the processing of virgin PPTA fibre and to PPTA fibre recyclates. Substantial morphological changes in PPTA fibres resulting from carding included kink banding, skin peeling and microfibrillation, the magnitude of which depended upon card feed rate and the number of passes through the system. Additionally, it was found that PPTA fibre degradation as a result of both UV irradiation and mechanical processing could initially increase rather than decrease fabric burst strength partly as a result of extensive fibril entanglement. A modified burst testing system that obviated fibre• bridging effects was developed to assist in the evaluation of PPTA hydroentangled fabrics. The magnitude of UV degradation in PPTA fibre webs was characterised using the b• colour coordinate (yellowness) in CIElab. There is an interaction between the irradiation of PPTA fibres and subsequent mechanical processes (carding and hydroentangling) wherein the fibres respond differently to non-irradiated fibres.
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