Long-Term Prediction of Creep and Stress-Relaxation Behaviour in Synthetic Fabrics Using the Time-Temperature Superposition Principle

In this work, time and temperature-dependent viscoelastic properties, i.e., creep and stress relaxation of synthetic fabrics have been studied using the dynamic mechanical analyser. Three different fabric materials viz. polyester (PET), polypropylene (PP) and Nylon 6,6 (PA) were used and tests were carried out at a wide range of temperatures from 35 to 110 degrees C with an interval of 15 degrees C after each test. Thereafter, the master curve for each fabric is generated at 35 degrees C using the time-temperature superposition (TTS) principle which extrapolates short time experimental data to a longer time scale by shifting experimental curves of different temperatures toward the reference temperature (35 degrees C) and superimposes them to obtain a smooth master curve. From the creep study, it is observed that PET fabric is expected to give greater creep resistance with minimal deformation in creep strain of about 39% followed by 53% in PA and 128% in PP even after 10 years. Besides, in the stress relaxation study, relaxation modulus for all fabrics tends to decrease with increasing temperature. It is found that PA fabric showed a slow reduction of relaxation modulus even after 10 years, which gives about 55% reduction followed by PET (68%) and PP (75%) from its initial value. In addition, true stress versus time curves showed that a higher true stress value in PA followed by PP and PET is referring to its higher relaxation modulus. It was found that initial modulus, glass transition temperature (T-g) and crystallinity of fibre plays an important role in determining creep and stress relaxation behaviour of the fabrics. On the other side, the correlation between experimental data and theoretical data ascertains the use of viscoelastic Burger's model and Weibull distribution equation model for creep and stress relaxation.