Injection Molding of Microstructured Surfaces Using Thermoplastic Elastomers

Past work has shown that the hardness of thermoplastic elastomers significantly influences the replication of surface microfeatures injection molded using positive tooling (i.e., projections).  This work investigates the interactions of tooling aspect ratio and feature orientation (negative and positive tooling) and thermoplastic elastomer hardness on microfeature replication.  Electroformed nickel tooling having positive and negative features with different geometries and aspect ratios of 50, 10, 1, and 0.5 were molded from three copolyester thermoplastic elastomers with similar chemistry and different hardness values.  The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry.  Results were correlated with elastomer properties.