Experimental investigation of the washing relaxation of knitted fabrics from polyester yarn with stainless steel fibres

In order to mathematically describe the washing relaxation of knitted fabrics from manmade fibres, we performed different experiments with 50 - 100 washing cycles. While washing with detergent was shown to lead to a logarithmic increase in the fabric width, washing without detergent leads to an approximately linear increase in the fabric width, which can be transferred into logarithmic behaviour after a number of washing cycles by then adding washing detergent. Moreover, the qualitative and quantitative dimensional change was proven to depend strongly on the original dimensions of the fabric – while a knitted fabric with only a few courses shows logarithmic behaviour and significant dimensional change, an approximately square fabric broadens more linearly and less strongly. In all cases, no end value for the fabric width is reached, i.e. no fully relaxed state.