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

Abstract

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 levels of POM. Although POM does not accelerate the crystallization of PLA as fast as some of the inorganic nucleating agents such as talc, it imparts PLA the nucleating effect without sacrificing transparency.