Sequential injection molding of thermoplastic polymers: Analysis of processing parameters for optimal bonding conditions

A systematic approach was used to study the effect of the process variables that control bonding of the injected melt to the previously injected parts, in sequential injection molding of thermoplastic polymers. Three polymer pairs were sequentially injected in a mold with the same geometry, in a range of mold and injected melt temperatures, and packing pressure conditions. Standard Peel Tests were conducted on injected samples to measure the resulting bonding strength. The analysis of the experimental results allows the quantification of the relative importance of the processing parameters involved. A direct correlation is found between the calculated interface temperature and the packing pressure needed for bonding. A generalized procedure is proposed to establish the processing conditions, which allow polymer-polymer bonding to be optimized.
INTRODUCTION Sequential injection molding of thermoplastic polymers has gained considerable importance in recent years (1). There is some literature on this subject (2) for vitreous polymers, but the bonding mechanisms, [...]