On the injection molding of thick-walled thermoplastic vulcanizates: linking static and dynamic mechanical properties with morphology

Elastomers are widely used in the automotive industry in anti-vibration components. Commonly, elastomeric anti-vibration components are made of thermoset rubbers. However, new drivers related to the requirements of the new sustainable mobility industry are pushing towards the substitution of thermoset rubbers by thermoplastic elastomers. Among thermoplastic elastomers, thermoplastic vulcanizates (TPVs) represent an interesting material choice for anti-vibration products due to their light weight, recyclability, ease of processing by means of injection molding and design flexibility. In this work, the correlation between static and dynamic mechanical properties and the morphology of injection molded thick-walled TPVs is investigated. Interestingly, when comparing TPVs of different hardnesses, the softest TPV demonstrated an improvement in elastic ability to recover of up to 50% in transverse to flow direction as well as a highly anisotropic viscoelastic behavior. These phenomena are interpreted in terms of the orientation of ethylene-propylene-diene particles together with polypropylene crystals and chain alignment observed in microstructural characterization tests. This study opens new opportunities to develop TPV-based anti-vibration components with superior elasticity and customizable static and dynamic mechanical properties by considering the anisotropic character of soft TPV materials in product design and development strategies.