Mechanical properties test and microstructure analysis of polyoxymethylene (POM) micro injection moulded standard parts

The tensile mechanical properties and the micro structure of micro injection moulded polyoxymethylene (POM) test parts were investigated in this paper. The effects of different injection moulding processing conditions on ultimate tensile stress and strain at break were analyzed. Additionally, the effects of miniaturization on the mechanical properties were investigated by executing injection moulding with both a standard tool designed according to ISO 527-2 and a miniaturized test part obtained from the standard design by a downscaling factor 10. The experiments have been performed according to factorial plans, in which the factors of interest were mould temperature, melt temperature and dimensional range of the specimen (i.e. macro and micro parts). Micro structure analysis was performed by means of plastography techniques and revealed that high mould and melt temperatures resulted on a thin skin layer and a larger spherulitic core, low value of ultimate tensile stress and high of elongation at break.