Prediction of Compressive Creep and Relaxation of HDPE

Abstract

The aim of this study is to predict the viscoelastic behaviour of high density polyethylene (HDPE) used in bottles and containers for liquid manufacturing, under compressive static long-term of creep and stress relaxation. A new mathematical model, based on the gradient method and the experimental compressive creep or relaxation results, is proposed. In this model, the response is assumed to be second order and is given as a linear combination of two exponential terms with different time constants. For the creep response, the deformation ε(t) given by the mathematical model is assumed to be time dependent. The model predictions at low stresses and strains are in good agreement with the experimental data. The maximal storage time of filled tanks is predicted to avoid the critical value of deformation of filled tanks (εc) respecting the relation (ε(t) >εc). In addition, the theoretical models, used in the prediction of the viscoelastic behaviour, determine the compressive stress relaxation through the compressive creep compliance, and vice versa.