Characterisation of the quasi-static material behaviour of thermoplastic elastomers (TPE) under consideration of temperature and stress state

Abstract

This article deals with the determination of the mechanical material behaviour of injection-moulded thermoplastic elastomers (TPE). For this purpose, the mechanical behaviour of TPE is investigated on basis of different materials (type and hardness) and process parameters with regard to the process-induced anisotropy. Based on these investigations, an almost isotropic material was selected for the investigations about the influence of temperature, stress state and load level. The results confirm that the hardness of the material and type of the processed material have an impact on the mechanical properties longitudinal and transversal to the flow direction. Furthermore, TPE behave quite similar to pure elastomers, as they showed a non-linear material behaviour, a stress softening after initial loading and a residual deformation after unloading. All these effects also depend on the temperature, stress state and load level, which results in a complex material behaviour. At the end of the article, two calibration approaches of a hyperelastic material model were shown (one set of parameters for all stress states vs. one set of parameters for each stress state). The second approach (one set of parameters for each stress state) shows a much higher accuracy in approximation of the test results.

Influence of moisture and CO2 on the material behavior of thermoplastic elastomers for beer bottle closures

“…The process conditions lead to different states of distribution, stretching and dispersion of the elastomeric phases during processing. As a result the mechanical behavior of injection molded TPE components also exhibit an anisotropic character [5]. In this study the significant differences in results between the studied elastomers in pellet form and molded shape clearly gives an indication of the need for injection molding process optimization for each liner material.…”

“…Block copolymers contain both the hard (thermoplastic) and soft (elastomeric) segments that chemically form a macromolecule. Representatives of this group are thermoplastic styrene elastomers (TPS) and thermoplastic polyamide elastomers (TPA) [5]. The elastomeric segments can be formed from unsaturated (poly(styrene-b-isoprene-b-styrene) (SIS); poly(styrene-bbutadiene-b-styrene) (SBS)) or saturated (poly(styrene-b-(ethy lene-co-propylene)-b-styrene) (SEPS), poly(styrene-b-(ethylene-co-buty lene)-b-styrene) (SEBS)) blocks [6].…”

“…In the case of polymer blends, the thermoplastic and the elastomer are physically mixed in a two-phase system. In polymer blends the elastomeric phase can either be present in so-called TPE-based olefins without cross-linking (TPO) or dynamically cross-linked thermoplastics (thermoplastic vulcanize (TPV)) [5].…”

“…Existing researches have only focused on the thermomechanical properties of materials [5,[7][8][9][10]. Glass transition temperature (T g ) values determined with DMA, DSC methods are typically used to judge the expected behavior of the actual components.…”

Effects of the injection molding processing settings on the phase morphology and mechanical anisotropy of thermoplastic vulcanizates

“…10 Additionally, the high cooling rates in these areas lead to a fixation of the distorted particles, affecting the TPV's local microscopic configuration and resulting in a preferential direction. 10 The shear rates are negligible in the center of the flow cross-section. Hence, the elastomer particles remain in their undistorted state.…”