Thermomechanical Behaviour and Interface of Overmoulded Soft Thermoplastic Vulcanizate Elastomers

Abstract

The influence of melt injection temperature on the thermomechanical behaviour of soft–soft overmoulded vulcanized thermoplastic elastomers (TPV) with different elastic properties was studied. Samples with two different overmoulding temperatures were tested under uniaxial loading conditions. The full deformation and temperature fields in each TPV were determined using digital image correlation technique and infrared thermography, respectively. The maximum interface strength was found to be equal to 70N for a maximum injection temperature of 260∘C, which is consistent with the fact that high temperatures promote interdiffusion between the molten TPV and the TPV insert. The two TPV have different stiffness, leading to a significant change of the interface position along the specimens during stretching and to a significant necking in the softer material. The zone of influence of the interface in terms of stretch gradient is very different in size from one TPV to the other. In addition, thermal investigations have shown that the elasticity of the two TPV is due to both entropic and non-entropic effects, the former being the most significant at large strains.

Development of an original overmoulding device to analyse heat transfer at polymer/polymer interface during overmoulding

“…at atmospheric pressure, thus allowing to neglect its effect on the kinetic. The shear happens at the beginning of the process (during the filling step of injection), in the order of the second, the effect of shear can therefore be neglected since the relaxation times are short compared to the time at which crystallization occurs [38]. In the present study, the effect of pressure and shear on crystallization is then neglected.…”