Controlled-release of ferulic acid from active packaging based on LDPE/EVA blend: Experimental and modeling

In this study, low-density polyethylene (LDPE) and ethylene vinyl acetate copolymer (EVA), as non-polar and polar polymers, were blended with ferulic acid (FA) as natural antioxidant at various compositions to make active packaging films with a controlled release of FA characteristic. The phase behavior of the blends studied by scanning electron microscopy revealed matrix-droplet morphology in blend containing 10 and 30 wt.% EVA, while the morphology was seen to be co-continuous in the 50/50 composition. Based on the differential scanning calorimetry results a reduction in the crystallinity of LDPE with narrow crystallite size distribution was observed on increasing the EVA content of the blends. The release rate of FA from the LDPE/EVA films was measured by means of UV-vis spectrophotometry and the results were compared with the release behavior of the neat LDPE and EVA as reference materials. It was found that by applying the second Fick's law the diffusion coefficient of EVA film against FA is 635 times greater than that of LDPE. The blends exhibited a better release behavior as compared to the neat polymers. The best and sustainable release behavior was obtained for the films with 30 wt. % of EVA content in which the FA was released in the environment with a controlled rate. Finally, the series, parallel, Maxwell and Equivalent Box Models (EBM) were applied to investigate the diffusivity coefficient of the blends. The EBM model showed the best agreement with the experimental data.