Since the flame retardant fabric is contracted by mechanical shrinkage, it is necessary to predetermine and control its shrinkage rate. The main processes are as follows:
(1) Cut two full-size post-treated flame retardant fabrics as samples, wash and iron them according to the regulations, and then obtain the shrinkage in both directions of length and width.
(2) According to the shrinkage ratio of the length and width of the flame retardant fabric sample, the mechanical pre-shrinking machine is adjusted to obtain the required pre-shrinkage rate.
(3) After the processed flame retardant fabric passes through the pre-shrinking machine, a sample is cut at the falling cloth, and the shrinking rate is obtained by washing and ironing in the same manner as the first sample which is not pre-shrinked. It is thus possible to determine whether the flame retardant fabric treated by the pre-shrinking machine achieves the required shrinkage ratio.
In order to make the flame retardant fabric not shrink due to washing during consumption, it should maintain the original size or achieve the specified shrinkage during use. When the machine is pre-shrinked, it is necessary to apply moisture and steam to the flame retardant fabric. Steaming, sometimes requires excessive wet treatment or excessive steam treatment. In actual production, the operation should be determined according to the actual situation and the finishing of the flame retardant fabric. However, no matter which kind of wet conditions are used, it should be ensured that each yarn (line) is completely wetted by water, so that each yarn (line) can be shrunk.