Size effect of carnauba wax nanoparticles on water vapor and oxygen barrier properties of starch-based film

Barrier properties against water vapor and oxygen were critical for starch-based nanocomposite film. In this study, size regulation of carnauba wax nanoparticle was utilized to adjust multi-scale structure of starch-based film, which intended to improve barrier properties. CW70 with 73.8 nm nanoparticle showed less disrupted starch hydrogen bonding, more ordered double helices, higher starch crystallinity and larger size of micro-ordered region compared with other nanocomposites. These changes of multi-scale structure of CW70 led to the lowest relative water vapor permeability (WVP, 0.86) and oxygen permeability (OP, 0.49) among all nanocomposites. Notably, water vapor could form new hydrogen bonding with starch, and the ratio of amorphous region was significantly negative correlated with WVP. Cohesive energy density was the determining factor for OP, and significant negative correlation was found between the size of micro-ordered region and OP. New knowledge from this study will advance the understanding of starch-based nanocomposite film barrier properties.