High-performance starch biocomposites with celullose from waste biomass: Film properties and retrogradation behaviour

In this work, the effects of relative humidity (RH) pre-conditioning (53% vs. 85% RH) and incorporation of cellulose fillers (from Posidonia waste biomass) on the properties and retrogradation of melt compounded starch biocomposites were investigated. Pre-conditioning at 85% RH promoted starch gelatinization during processing, leading to more amorphous materials with reduced stiffness but better barrier properties. Furthermore, these films were less stable upon storage due to greater starch retrogradation. Cellulose incorporation improved significantly the mechanical and water barrier performance, especially in the films pre-conditioned at 85% RH due to enhanced filler dispersion. Although incomplete gelatinization of the starch pre-conditioned at 53% RH led to films with bigger cellulose aggregates, their mechanical and water barrier properties were better, outperforming starch-cellulose biocomposites typically reported in the literature. Moreover, the presence of cellulose limited the degree of starch retrogradation upon storage, highlighting the potential of Posidonia biomass as a cheap source of high-performance fillers.