Effects of Polyoxymethylene as a Polymeric Nucleating Agent on the Isothermal Crystallization and Visible Transmittance of Poly(lactic acid)

In this work, use of polyoxymethylene (POM) as a polymeric nucleating agent for poly(lactic acid) (PLA) was studied. The compounding was performed using a twin-screw extruder. Effects of POM on isothermal crystallization of PLA at temperatures ranging from 106 °C to 111 °C and visible transmittance of PLA were examined in detail with various techniques, including polarized optical microscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and ultraviolet–visible (UV-vis) spectroscopy. Banded spherulites were noted when the POM content exceeded 5 wt %. The presence of POM generally resulted in effective reductions in the half time of crystallization and the spherulite size of PLA. However, 1% POM was a threshold for the nucleating effect: at ≤1% POM, no nucleating effect was observed. Fourier transform infrared (FTIR) spectroscopy revealed the strong interaction between the two polymers. The Avrami modeling suggested a three-dimensional crystal growth at all temperatures and loading leve...