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Maximizing Crystallinity of Slowly Crystallizing

Polymer in Injection Molded Parts


Summary -- The lack of crystallinity is the main cause of poor mechanical properties observed in slowly crystallizing biodegradable polymers such as poly (L-lactide). The objective of the research is to develop new technology in injection molding applications for maximizing crystallinity.  This objective is accomplished by rapidly heating the mold surface so that the melt can readily crystallize while the melt is under shear stress and yet be processed within the normal injection molding cycle time.  This in-mold crystallization requires much less time for the crystallization to occur since the activation energy is much lower when polymer molecules are orientated under shear stress. Parts produced in this manner will provide the basis for better modeling of shear induced crystallization kinetics in injection molding process. These parts will enable the measurement of the crystallization levels in the gap and flow directions that will provide excellent data to validate theoretical predictions.  Further, to maximizing the amount of crystallization in the molded part, the inverse design optimization technique will be employed to obtain an optimally prescribed temporal profile of the mold surface temperature. Development of the technology to mold parts with maximum crystallinity will greatly enhance applications of slowly crystallizing biodegradable polymers.