Synergistic Effect of Talc and Titanium Dioxide on Poly(lactic acid) Crystallization: An Investigation on the Injection Molding Cycle Time Reduction

Abstract

Injection molding cycle time is one of very important parameters relating to the plastic production rate. In neat poly(lactic acid) (PLA), it requires more than 25 min to obtain its half crystallinity (t 1/2 ). This indicates that the injection molding of neat PLA with high degree of crystallinity (X c ) and high production rate is impossible. This research aims to increase the crystallization rate of PLA by combining two inorganic fillers namely; titanium dioxide (TiO 2 ) and talc. Differential scanning calorimetry (DSC) study indicated that the t 1/2 of PLA decreased from 27 min to < 81 s, while the X c increased by around 16% with the adition of TiO 2 . Modifying PLA with talc was found to reduce t 1/2 down to 36 s and the X c increased from 0.92 to 20% only at a heating rate of 1 °C/min. The combination of talc and TiO 2 was significantly increased the X c for all cooling rates applied. Synergistic crystallization behavior was clearly observed when TiO 2 was added to PLA/talc for all TiO 2 concentrations. Minimum t 1/2 of 18 s was observed together with the increased X c by around 26% when TiO 2 was added to PLA/talc at 3 wt%. This reduced the injection cycle time from around 28 min, in neat PLA, down to 68 s at this TiO 2 content. With the presence of talc and TiO 2 , the flexural modulus of the composites was improved significantly. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.