High Efficiency Nucleating Agents of Polyoxymethylene

Abstract

In this research, the effects of different kinds of nucleating agents on the crystallization and mechanical properties of polyoxymethylene (POM) were studied, including inorganic, organic, and polymer nucleating agents and their compounds. These properties showed that nanoCaCO₃, sorbitol derivative TMB-5, polyamide PA-4, and compound C-1/polyamide (PA)-4 can make spherulites of POM finer and more perfect, and effectively improve its notched impact toughness, in which the compound C-1/PA-4 displayed more remarkable nucleation effect. The study on the nonisothermal crystallization of POM showed that the crystallization temperature and crystallization growth rate of POM increased when C-1/PA-4 was added. The isothermal crystallization kinetics were also analyzed by the Avrami equation. The addition of C-1/PA-4 can increase the values of the Avrami exponent (n) and crystallization rate constant (k), and reduce the half-time of isothermal crystallization, t_1/2, and the time corresponding to the maximum rate of crystallization, t_P, indicating its remarkable nucleating effect on POM.

Keywords:

• Crystallization
• Impact toughness
• Nucleating agent
• Polyoxymethylene (POM)

ACKNOWLEDGMENTS

The authors wish to thank Yuntianhua Co., Ltd., Yunnan, China, for kindly supplying POM sample. The authors also thank the support of the project “University-Industry Cooperation Project of Yunnan Province” (2002ZABDA00A015), and “Program for Changjiang Scholars and Innovative Research Team in University” (IRT0449).