Evaluation of Sewability of Nappa Leathers

This paper focuses on determining the standard threshold value of needle penetration force and sewability of garment leathers using sewability tester whose design has been modified exclusively for leathers. Two different types of apparel leathers sheep and goat nappa leathers were chosen for the study. A nominal value of threshold was initially set based on mass per unit area of samples and tests were carried out at different threshold settings. The appropriate threshold level was determined based on the actual performance of the fabric/leather with respect to needle breakage, seam performance etc. It has also been observed that there is a correlation between weight/thickness and threshold value of needle penetration force which is well explained on the basis of the fact that as the weight/thickness increases, the resistance to sewing increases and thereby sewability value increases. The sewability values of goat nappa leathers are on the higher side compared to sheep nappa leathers because of the dense and compact triple helical fibre structure.