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Analysis and Control of Variability in the Fibre Making Process

April 21st, 1991

Paper to the Polymer Processing Society Annual Meeting, Hamilton, Ontario, 21st-24th April 1991

S F Bush with C G A Clayton


Fibre-making is a multi-stage process of great complexity, which is part of an even larger, more complex process running from polymer manufacture at one end to the dyeing of woven or knitted fabric at the other. The ability of a woven fabric of say some 6000 fibres to dye uniformly is arguably the most searching test that can be applied to a fibre-making process. Since it is dependent on quite subtle features of the solid polymer structure which depends in turn on any or all of the conditions at polymerisation, drying, spinning, drawing, bulking, weaving or knitting and dyeing itself. As a material stream moves through the stages from polymerisation down to bulking, it is split between more and more material pathways, so that a fault in any one pathway at any time can infect the whole at the weaving or knitting stages where the material paths are re-integrated again.

The object of the work described was to improve and maintain the quality of bulked poly(ester terephthalate) or PET fibre, particularly as production speeds were increased. Quality here means essentially uniformity of appearance in woven or knitted fabric, and in particular the absence of stripes arising from the presence together of a few fibres which are different from their neighbours in the fabric. The crucial point is that such non-uniformity will only be apparent long after the product has left the producer’s factory. Much effort has therefore been expended by fibre-makers over the years to devise instrumental tests which can be used at the factory to predict the likely appearance in customers’ hands.