Structure/properties relationship within injection molding samples obtained by fast modulation of the cavity temperature

Abstract

The tailoring of the properties developed in the plastic objects only by the process is mandatory in order to improve the sustainability of the plastic objects. The possibility to tailor the properties developed within the molded object is essentially related to the understanding of the relationship between the properties and the process. One of the main process parameters that allows tailoring properties of molded objects is the mold temperature. In this work, a thin electrical heater was developed and located below the cavity surface in order to obtain rapid heating/cooling cycles during the process. An isotactic polypropylene was adopted. The modulation of the cavity temperature was found to control the distribution of the properties along the sample thickness. In particular, elastic modulus and lamellar thickness distributions were strongly influenced by the temperature field experienced by the polymer chains. Both distributions show the highest level in the shear layer and the intermediate values in the sample core. The correlations between these two properties is due to the structuring phenomenon occurring during the process.