engleski

Dynamic mechanical analysis of poly(vinyl- alcohol)/chitosan blends with ZnO nanoparticles

Nanocomposites encompass a large variety of materials made of distinctly dissimilar components and mixed on a nanometer scale. Their properties depend not only on the properties of their constituents, but also on their morphology and interfacial characteristics. This research focuses on relating structure and mechanical properties of nanocomposites with antimicrobial activity. Organic nanoparticles of chitosan (CS) and inorganic nanoparticles of ZnO, both with cumulative antimicrobial activity, are added in a non-toxic matrix of poly(vinyl-alcohol) (PVA). CS in the mixture reduces the crystallinity of PVA inducing degradation of mechanical properties. However, the properties of the polymer matrix can be improved by chemical crosslinking with glutaraldehyde (GA) and by adding ZnO nanoparticles. Polymer solutions with NPs are casted and then dried in oven in order to prepare flexible films. A solution of highly deacetylated low molecular CS in dilute acetic acid is mixed with 99 % hydrolyzed PVA dissolved in water. The blend is cross-linked by means of the glutaraldehyde. ZnO NPs are prepared by precipitation method from ZnSO4·7H2O. Molecular dynamics of these mono-, bi- and ternary systems with different compositions is examined by means of dynamic mechanical analysis (DMA). In the tan δ vs temperature graph the  relaxation peak that is attributed to the glass-rubber transition increases both when CS is added to the PVA and when PVA is chemically crosslinked with GA indicating an increase in free volume amount. However, a slight drop and shift to higher temperatures is observed when GA is added into the PVA/CS mixture. CS reduces the crystallinity degree leading to the higher amount of the amorphous phase contributing to  relaxation, but the mobility of the amorphous phase can be restricted with crosslinking. When ZnO NPs are added, a new phase on the interface of the PVA/CS blend with ZnO is expected to form.

Polymer nanocomposites, ZnO nanoparticles, dynamic mechanical analysis

nije evidentirano