The use of the Box–Behnken experimental design to model tensile strength of spunlaced fabrics and evaluating fabrics behaviour in acidic condition

Determining the tensile strength of nonwoven fabrics is one of the important factors considered for operational performance of the fabrics, especially for fabrics that are exposed to acidic condition. Polyacrylonitrile (PAN), polyphenylene sulfide (PPS) and polyimide (PI) fibres are used to produce fabrics that can withstand harsh chemical condition and still possess the required tensile strength; however, over a period of time the tensile strength gradually decreases. The Box–Behnken design method results showed that it can model and describe the effects of process parameters on the tensile strength of spunlaced fabrics in both cross direction and machine direction. The contour plots’ results indicate that varying the fibres polyacrylonitrile (−1), polyphenylene sulfide (0) and polyphenylene sulphide/polyimide (1) from −1 to 1 increases the fabric tensile strength in both machine direction and cross direction. For water jet pressure 60 bar (−1), 80 bar (0) and 100 bar (1), increasing the pressure from −1 to 1 increases the fabric tensile strength in cross direction but in the machine direction the fabric strength decreases. Increasing the fabric area weight of 440 g/m2 (−1), 500 g/m2 (0) and 560 g/m2 (1) from −1 to 1 decreases the tensile strength. Exposing fabrics to sulphuric acid (H2SO4) decreases the fabric tensile strength in both machine direction and cross direction due to the degradation of the fibres and the loss decreases gradually with the duration of exposure. For PAN fabrics, the tensile strength decreases by 21% and that of PPS and PPS/PI fabrics decrease by 10% and 6%, respectively.