How to Achieve a Highly Toughened 70/30 PLA/PCL Blend by Using Nucleating Agents and Tailoring Processing Conditions

In this work, the toughening of a 70/30 polylactide (PLA)/poly(ε-caprolactone) (PCL) blend was achieved by the addition of nucleating agents (NAs) and by tailoring the processing conditions. To this end, different NAs (TMC200, TMC300, TMC306, and TMC328) were used to promote the crystallization of PLA. For comparison reasons, the effect of NAs on the PCL phase was also analyzed. From polarized light optical microscope (PLOM) observations and crystallization kinetics studies (performed by differential scanning calorimetry), it was concluded that TMC200 and TMC328 were the most efficient NAs for PLA, whereas TMC300 and TMC306 were the best in the case of PCL. Nucleation efficiency calculations showed, for the first time, a supernucleation effect of TMC200 and TMC328 NAs on PLA. However, the NAs did not produce any significant change in the mechanical properties of the blends when the samples were injection-molded into a cold mold. By contrast, PLA70/PCL30/NA blends with high impact strength values were achieved using a high mold temperature and a longer molding time. From PLOM and transmission electron microscope observations, it was concluded that the PLA/PCL blends must have a high PLA nucleation density and submicrometer spherulitic sizes along with a homogeneous PCL particle size distribution to achieve a PLA-based blend with high impact strength.