Reduction clearing of simulated disperse dyed PLA fabrics and their tensile properties

Abstract

Polylactic acid (PLA) knitted fabric has been subjected to various textile wet processes, viz. scouring, bleaching and simulated disperse dyeing. Reduction clearing (RC) has been performed at various process conditions such as concentrations of sodium dithionite and sodium carbonate, bath temperature and process time and a full factorial experiment is designed. The results show that the pretreatment processes and RC parameters have pronounced effects on tensile properties of PLA yarns. Statistical analysis of variance is performed which show significant differences at a confidence interval of 99%. Attenuated total reflectance infrared spectroscopy of the PLA fabric is carried out to investigate chemical changes on fibre surface. Scanning electron microscopy reveals that the bleaching causes the formation of slits in the fibres. Since bleached fibres are already porous, the strength of PLA yarns is further decreased during simulated disperse dyeing and reduction clearing processes.