Effect of Silver Nanoparticles on the Melting Behavior, Isothermal Crystallization Kinetics and Morphology of Polyoxymethylene

In this work, the effects of silver (Ag) nanoparticles on the melting behavior, isothermal crystallization kinetics, and morphology of polyoxymethylene (POM) were studied. It was found that the melting peak temperature (T-m) and the crystallization temperature (T-C) of POM/Ag nanocomposites shifted to higher temperature with the content of Ag nanoparticles increased. In addition, the isothermal crystallization kinetics of POM/Ag nanocomposites were determined by Avrami and Lauritzen-Hoffman models. The results of crystallization half-time (t(0.5)), reciprocal of crystallization half-time (tau(0.5)), Avrami exponent (n), and Avrami rate constant (k) showed that low loading of Ag nanoparticles (<= 1 wt%) accelerated the crystallization rate of POM. However, when the content of Ag nanoparticles reached 2 wt%, they aggregated together and restrained crystallization of POM. Meanwhile, the results of nucleation parameter (K-g) and surface free energy of folding (delta(e)) revealed that Ag nanoparticles reduced the energy need to create a new crystal surface, leading to faster crystallization. Moreover, the crystallization activation energies ( increment E) were determined using the Arrhenius model, which suggested that Ag nanoparticles induced the heterogeneous nucleation by lowing the increment E. Furthermore, polarized light microscopy results indicated Ag nanoparticles generated a great amount of nucleation sites and led to the formation of smaller spherulites.