Construction of the visco-elastic constitutive model for polyethylene terephthalate in a rubbery state

Abstract

Polyethylene terephthalate (PET) is an important commercial engineering polyester thermoplastic used in beverage bottles. PET is usually biaxial stretched above its glass transition temperature (T g ) and molded into containers by injection stretch blow molding (ISBM) under a rubbery state. This paper constructs a visco-elastic constitutive model for PET above T g . The stress-strain behaviors of PET can be explained by the Eyring activation mechanism and the Arruda-Boyce eight-chain rubber model(A-B model). In the constitutive model, the overall stress of PET is equivalent to the sum of Eyring dashpot and A-B model stresses. The uniaxial tensile test data confirms the constitutive model under three stretch rates and temperatures. The constitutive model can furtherly be applied in the numerical simulation of the PET ISBM process.