Effect of gate dimensions on the physical properties of micro injection molded poly(L-lactic) acid

One of the major parameters of interest in the micro injection molding of plastics is the gate dimension.; The study investigated the processing conditions, differences in mechanical properties and melt flow rate of PLLA and PP molded through two gates 0.76mm (0.030 inch) and 0.076mm (0.003 inch) depth.; The optimum processing conditions found for PP were compared those suggested by a mold flow analysis. The mold flow analysis was not possible for PLLA.; The mechanical properties of PLLA produced through the 0.076mm (0.003 inch) inch gate exhibited greater stiffness while the 0.76mm (0.030 inch) gate resulted in a tougher product.; Only minor changes in mechanical properties were noticed in PP.; PLLA exhibited a significant molecular weight loss in molding. This was true for both gates. No molecular weight changes were noted in injection molding PP.