Micro‐injection molding of thermoplastic polymers: Proposal of a constitutive law as function of the aspect ratios

ABSTRACT Based on experimental measurements of the in situ conditions within polymer flow during micro‐injection molding, a new geometrical parameter is defined to predict realistic dimensions of micro‐parts (μparts). To this aim, thin‐walled parts of various aspect ratios “length/thickness” (L/h) were first molded, with two different polymers: (i) a polystyrene and (ii) a cyclo‐olefin copolymer. It is shown that pressure drops (ΔPi), measured between the injection pressure and the various sensors present in the mold, are directly related to the square of the ratio of L/h. This approach has finally been successfully applied to the results of the literature, confirming its relevance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45719.