Effect of Silver Nanoparticles on the Microstructure, Non-Isothermal Crystallization Behavior and Antibacterial Activity of Polyoxymethylene

Abstract

Silver (Ag) nanoparticles were synthesized by a facile route in the presence of oleic acid and n-propylamine. It was shown that the average primary size of the as-synthesized Ag nanoparticles was approximately 10 nm and the surface of as-synthesized Ag nanoparticles was capped with monolayer surfactants with the content of 19.6%. Based on as-synthesized Ag nanoparticles, polyoxymethylene (POM)/Ag nanocomposites were prepared. The influence of Ag nanoparticles on non-isothermal crystallization behavior of POM was investigated by differential scanning calorimetry (DSC). The Jeziorny, Jeziorny-modified Avrami, Ozawa, Liu and Mo, Ziabicki and Kissinger models were applied to analyze the non-isothermal melt crystallization data of POM/Ag nanocomposites. Results of half time (t1/2), crystallization rate parameter (CRP), crystallization rate function (K(T)), kinetic parameter (F(T)), the kinetic crystallizability at unit cooling rate (GZ) and the crystallization activation energy (∆E) were determined. Small amounts of Ag nanoparticles dispersed into POM matrix were shown to act as heterogeneous nuclei, which could enhance the crystallization rate of POM, increase the number of POM spherulites and reduce POM spherulites size. However, the higher loading of Ag nanoparticles were easily aggregated, which restrained POM crystallization to some degree. Furthermore, the POM/Ag nanocomposites showed robust antibacterial activity against Escherichia coli and Staphylococcus aureus.

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

“…Crystals 2020, 10, x FOR PEER REVIEW 5 of 17 content of Ag nanoparticles reached 2 wt%, they would be easily aggregated together due to monolayer surfactants of Ag nanoparticles with weak effect, which resulted in poor dispersion of Ag nanoparticles in POM. This result was consistent with the analysis result of SEM images of POM/Ag nanocomposites in the previous paper [37].…”

“…However, when the content of Ag nanoparticles increased to 2 wt%, the Ag nanoparticles easily aggregated together, which had a certain inhibitory effect on crystallization process of POM. The effect of Ag nanoparticles on isothermal crystallization of POM/Ag nanocomposites was in good accordance with that of Ag nanoparticles on non-isothermal crystallization of POM/Ag nanocomposites [37]. 2:…”

“…Therefore, the as-synthesized Ag nanoparticles were coated with a monolayer of surfactants consisting of oleic acid and the n-propylamine. In addition, the detailed preparation process and characterization of the Ag nanoparticles can be found in a previously published paper [37].…”

“…On the other hand, it was found the enthalpy of second melting endotherms (∆H m ) and the degree of crystallinity (X C ) of POM/Ag nanocomposites first increased, then decreased as the content of Ag nanoparticles increased (Figure 3b,c). This could be attributed to the fact that the efficient heterogeneous nucleation of Ag nanoparticles could accelerate the crystallization rate of POM, which increased the degree of crystallinity of POM to a higher level, when the amount of Ag nanoparticles of POM/Ag nanocomposites was low (≤1 wt%) [37]. However, when the amount of Ag nanoparticles increased to 2 wt%, the Ag nanoparticles easily aggregated together to form a lot of large clusters in the POM matrix, which could affect the heterogeneous nucleation of Ag nanoparticles and restrained crystallization of POM to some degree [37].…”

“…In our previous work, we successfully synthesized Ag nanoparticles with a monolayer of surfactants composed of oleic acid and n-propylamine, and the average size of Ag nanoparticles was approximately 10 nm, with a narrow size distribution. Meanwhile, the Ag nanoparticles gave rise to a better compatibility with POM and could be well dispersed in the POM matrix [37].…”