Abstract
It is difficult to spread the repellent agent uniformly on the surface of the substrate using the dilute solution which contains the least amount of repellent agent required theoretically, and the defects in the layer will result in insufficient repellency. Therefore, the excess amount of repellent agent is used for practical treatments.
The effects of dilution of the repellent solution and the application of surfactants on waterproofing were investigated, and the following results were obtained;
(1) The contact angle between a water drop and cellophane, and its resistance against washing and wearing does not deteriorate untill the concentration of repellent agent decreases to about a tenth of usually applied concentration. Below this range, the fluorochemical agent exhibits more rapid decrease of the contact angle than the silicone.
(2) The repellent effects are improved by repeated treatments with the solution of unsufficient concentration.
(3) The pretreatment with the solution of surfactant followed by drying over 100°C, recovers the deterioration due to the dilution of repellent agent and this recovery showed maximum between 0.001% and 0.01% of surfactant concentration. At the higher concentration, the levelling effect of surfactant fixed on the surface of substrate might be outweighed by the hydrophilic effect of the surplus surfactant.
