Effect of feature spacing when injection molding parts with microstructured surfaces

The effects of microfeature spacing on the replication of thermoplastic elastomer features was investigated using micropillars with two diameters (10 μm and 20 μm) and three spacing ratios (0.5:1, 1:1, and 2:1). The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry. Filling simulations provided insight into the process. Feature spacing significantly affected the replication of micropillars using a thermoplastic elastomer. This replication was competition between pressurization, relaxation, and cooling of the melt. Higher pressures generally improved feature replication, but did not always create perfect replication. Relaxation of the highly aligned polymer chains and cooling effects restricted filling, tended to reduce feature height, and increase feature diameters. POLYM. ENG. SCI., 56:1330–1338, 2016. © 2016 Society of Plastics Engineers