An analytical model to predict the creep behaviour of linear low-density polyethylene (LLDPE) and polypropylene (PP) used in rotational moulding

Abstract

Rotational Moulding (RM) is a versatile plastic processing method for the production of hollow products. Since the life expectancy of RM products are over several decades, prediction of mechanical properties like creep will be useful during the design phase of a product. In this research, an analytical model based on time hardening model was developed to predict and compare the creep behaviour of linear low-density polyethylene (LLDPE) and PP at 40 °C. The model uses some constants obtained from the experimental findings of a typical accelerated creep test using stepped isothermal method- time-temperature superposition (SIM-TTS). Based on the creep performance, the comparison of the two materials (LLDPE and PP) has been carried out and inferences have been made about their long term performance under constant stress.