Evaluation of coefficient of friction in similar conditions to ejection of molding parts

Abstract

The injection molding is the technique most used for processing polymers. Nowadays, due to economic demands the ejection of the parts occur as soon as possible to lead to a short cycle times. The ejection stage is the most critical phase during the injection molding processing. During this stage, especially in deep core molding, it is possible the development high friction forces making difficult the ejection of the moldings without marks or other defects. The aim of this work is to assess the coefficient of friction between the part and the mould walls in conditions similar that occurs during the ejection in the injection molding process. The assessment of the coefficient of friction was carried out with the help of one apparatus that possibility this type of measurement. This equipment provides that measure under controlled conditions as test temperature, replication temperature, material of the mould, and superficial roughness. The obtained results with several polymeric materials (semicrystalline and amorphous) show that the tribological conditions have great influence on the coefficient of friction in static conditions.