Differential Solubility of Acrylic Fibres as a Function of Stabilisation Process Variables

Acrylic tow, partially relaxed during the first stage of a conventional manufacturing process, was fully relaxed, or stabilised, in steaming equipment under different conditions of time and temperature based on a central rotatable design of experiments. The shrinkage of the samples thus obtained was measured and differential solubility curves in a mixture of dimethy/formamide and water were obtained. From these results simple functional relationships between shrinkage and solubility on the one hand, and the process variables, temperature and time, have been obtained. Response surfaces showing an excellent fit have also been obtained. A very good negative linear correlation between the logarithm of shrinkage undergone during steaming and the logarithm of differential solubility, and also between the logarithms of overall shrinkage and differential solubility have been found. The differential solubility test has a very high sensitivity to relaxation process variables and, as shown by the correlations obtained, it is highly recommendable as a relaxation control measure in production plant.