Crystallization, morphology, optical properties, tear properties and antibacterial properties of nano zinc oxide composites

Nanometer Zinc oxide (nano ZnO) composites are widely used in the packaging industry due to their excellent antibacterial properties. In this study, low-doped (0.2%) and high-antibacterial (99.9%, R = 6.9) nano ZnO composites with different matrices were prepared using a masterbatch blending method. To investigate the effect of different matrices on antibacterial properties, we decreased the solid content of nano ZnO to 0.05% and prepared antibacterial films by melt-blending with ethylene vinyl acetate copolymer (EVA), polyolefin elastomer (POE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and amorphous polymer polycarbonate (PC). The results showed that low melt strength and high crystallinity would decrease the antibacterial activity of the composite. At room temperature, the PC with a frozen molecular chain can hinder the migration of small molecules, thereby reducing antibacterial activity. Polar ZnO is more compatible with polar vinyl acetate (VA), leading to the hindered surface migration of ZnO and reduced antibacterial activity. Most importantly, low crystallinity does not necessarily lead to a reduction in barrier properties. The dense and rich layered arrangement of polyolefin elastomer (POE) increases its ability to impede the migration of nano ZnO, thereby significantly reducing its antibacterial effectiveness. A concentration of 0.05% ZnO/linear low-density polyethylene (LLDPE) exhibited an antibacterial rate of up to 99.3%. Additionally, adding a small amount of nano ZnO improves the tear resistance of antibacterial composite materials. This study provides a theoretical basis for the preparation of low doping, high antibacterial and excellent comprehensive performance.