The effect of organic nucleating agents on crystallization behavior of polylactic acid

P. Gao, J. Krantz, S. Alanazi, D. Masato
University of Massachusetts-Lowell,
United States

Keywords: PLA, crystallization, nucleating agent

Summary:

Polylactic acid (PLA) is one of the most common biodegradable polymers. Its bio-based nature makes it an ideal substitution of petroleum-based resins. However, its wider application is limited by the low crystallization rate and a low crystallinity under quiescent and processing conditions. One of the most effective ways to enhance the crystallization ability of PLA is to add nucleating agents. In this research, a commercial grade PLA is premixed with orotic acid and ethylene bis-stearamide (EBS) at concentrations of 0.3%, 1.0% and 2.0%, respectively. The samples were prepared in a quiescent condition with no additional pressure or shear stresses. The degree of crystallinity and crystallization kinetics of the PLA-nucleating agent compound were obtained from isothermal differential scanning calorimetry. The experimental results showed that with the addition of 0.3% of nucleating agent increased the crystallization rate by more than two orders of magnitude. The incubation time was decreased by > 30% and the total time required to reach the maximum degree of crystallinity by >150% as compared to neat PLA. 1% nucleating agent showed higher crystallization rate as compared to 0.3% and 2.0% concentration for both orotic acid and EBS. Optical microscope and scanning electron microscopy were utilized to obtain the morphological properties of the crystal structures obtained by different concentrations of nucleating agents.