Validation of the Use of SEBS Blends as a Substitute for Liquid Silicone Rubber in Injection Processes

Abstract

Liquid silicone rubber is an interesting material at an industrial level, but there are great difficulties in the design and machining of molds, and in addition, it cannot be processed using conventional equipment. Therefore, new lines of research have focused on the search for new materials capable of providing final properties similar to liquid silicone rubber, that can also be engineered using simple, conventional processes and machinery. In this investigation, a range of compatible blends, based on two commercial grades of styrene-b-ethyleneco- butylene-b-styrene (SEBS) thermoplastic elastomer, was studied in order to obtain a range of different Shore A hardness blends for industrial applications where liquid silicone rubber (different hardness) is currently used. The two blended elastomers used had widely differing Shore A hardness values (5 and 90). Once the blended materials had been characterized, the Cross and Williams et al. [20] (Cross-WLF) mathematical model was applied in order to obtain theoretical performance curves for the viscosity of each of the blends. After this, a model was developed using the Computer Aided Engineering (CAE) software package Autodesk Moldflow 2012TM. This computer modeling validated the results obtained from the mathematical models, thus making available to process engineers the full range of hardnesses necessary for industrial products (where liquid silicone rubber is used), while still providing the advantages of thermoplastic injection molding.