Effects of zeolite loaded with silver, copper, or zinc ions on antimicrobial properties of the ethylene-vinyl acetate copolymer

The improvement of antimicrobial activity of ethylene-vinyl acetate (EVA) resin is of significant importance from the hygienic point of view. Hence, the present work aimed to improve antimicrobial performance of the polymer with the aid of a novel, effective and low-cost additive. Accordingly, the effects of incorporating Mobil twenty-two zeolite loaded with silver, copper and zinc salts to EVA on antimicrobial activity of the polymer was investigated in this study. The used zeolite was hydro thermally synthesized and doped with silver, copper, or zinc nitrates. The loaded zeolite particles were added to EVA through melt mixing. The prepared composite samples were then compression molded to obtain thin films with a thickness of about 0.1 mm. X-ray diffraction experiments and scanning electron microscopy revealed successful synthesis of Mobil-twenty-two zeolite and its metal-salt loading. Moreover, favorable distribution of the loaded zeolite in the polymer matrix was proved by scanning electron microscopy images. Also, stress-strain test unveiled that the addition of the zeolite particles enhances Young's modulus and tensile strength of the polymer while decreases its elongation at break. In addition, among the studied samples, the one containing 2 wt.% of silver-loaded zeolite showed the highest Young's modulus of 105 +/- 4.7 MPa. however, its modulus was only about 2% higher than that of the sample containing 2 wt.% of copper/zinc-doped zeolite. Moreover, the two mentioned samples showed the highest elongation at break among the samples containing 2 wt.% of the loaded zeolites. Besides, the lowest observed elongation at break was 491% +/- 16.2 belonging to the composite sample containing 2 wt.% of copper-loaded zeolite. Furthermore, the film samples containing either of the loaded zeolite particles exhibited antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans, with maximum bacterial and fungal inhibitions of about 56% and 54% in the case of the film samples containing 2 wt.% of silver and copper/zinc-doped zeolite, respectively. Overall, it was concluded that copper and/or zinc-loaded zeolites, the effects of which is comparable to that of silver loaded zeolite, have the potential for application as low cost additives to induce antimicrobial activity to EVA, while maintaining its beneficial mechanical properties.