Studies on Crystal Morphology and Crystallization Kinetics of Polyamide 66 Filled with CaCO₃ of Different Sizes and Size Distribution

Abstract

In this study, two different sizes of calcium carbonates (CaCO₃) were blended and filled into polyamide66 (PA66). The effect of CaCO₃ on the crystallization behavior of PA66 is investigated by differential scanning calorimeter (DSC). The melting measurement results indicated PA66/CaCO₃ composites have secondary crystallization phenomena, which means that the crystallization process is more complicated. The crystallization temperature of the efficient size distribution samples is lower than that of the single size distribution samples. The isothermal crystallization kinetics experimental results showed that PA66/CaCO₃ has the heterogeneous nucleation process, while the pure PA66 has homogeneous nucleation process. Compared with the composites filled with single-size CaCO₃, both the crystallization rate constant (K) and their Avrami exponents (n) of isothermal crystallization kinetics increase. The rheological measurement result shows that the shear viscosity of the efficient size distribution composites is lower than that of the single size distribution samples. The result can be used to explain that the experimental results of crystal morphology and crystallization. The lower viscosity of the system is, the harder nucleation, the easier crystal formation.

Keywords:

• CaCO₃
• Crystallization kinetics
• Different size and size distribution
• Polyeamide66
• Shear viscosity

ACKNOWLEDGMENT

The authors would like to thank the China National Science Foundation (Grant No. 20874047) and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China for the financial support of this research (Grant No. 08KJB150010).