A Consideration of the Critical Add-On and the Uniformity of Crosslinking

Abstract

In a low add on, easy-care finishing system, the critical add-on value (CAV) is defined as that amount of finishing liquor which must be applied to a given fabric in order to avoid a nonuniform distribution of crosslinking after drying and curing. , At least two different types of nonuniformity have to be recognized. Type-one nonuniformity occurs when the amount of liquor applied is significantly higher than the CAV, so that migration of chemicals to the fabric surface occurs. Type- two nonuniformity is produced when the amount applied is low er than the CAV, so that more-or less isolated small spots of untreated fabric occur. It has been found that the CAV depends upon the fabric construction and the pretreatment. Mercerizing enforces higher CAV, but liquid ammonia treatment usually allows a reduction. The concentration of crosslinking agents in the formulation also exerts an influence. A short (5 s) steaming step between impregnation and drying allows a significant reduction in CAV and apparently eliminates the influence of the pretreatment.