The use of the indentation test for studying the solidification behaviour of different semicrystalline polymers during injection moulding

An in-line method for monitoring the solidification process during injection molding of semicrystalline polymers (demonstrated previously in J. Appl. Polym. Sci.2003, 89, 3713) is based on a simple device, where an additional ejector pin is pushed on the injection molded part at different times during the solidification phase. The ‘indentation depth profile’, i.e., residual deformation as a function of time, was obtained and allowed to determine the evolution of the solidification front in the mold as a function of the cooling time. The present work shows the reliability and the powerfulness of the aforementioned method for a large variety of different semicrystalline polymers (PET, PBT, polyamide-6 PA6, isotactic poly(propylene) iPP) characterized also by different molecular weight and/or nucleating agents. The results show that the indentation test may be considered as a ‘predictive’ tool to qualitatively and quantitatively compare the solidification process of different polymers and polymer grades during injection molding.