Nanostructured biopolymers obtained from blends by extrusion

The extrusion of biopolymers is a promising technology for the plastic industry since enables to lead to wide range of innovative and environmentally friendly products displaying many advantages for the food packaging sector such the ability to extend food shelf life (Azevedo et al., 2017; Rathod & Annapure, 2017; Rodríguez-Núñez et al., 2017). Starch (St) is one of the most commonly available and cost effective biopolymer with high biodegradability and renewability and the chitosan (Cs) is a natural polysaccharide stemming from the deacetylation of chitin which can be considered as the largest world widespread biomaterial after cellulose in terms of utilization and distribution. On the other hand, the montmorillonite (MT) and bamboo fibers (BNFs) are used as fillers for improving the films mechanical and barrier properties. In this study, nanostructured films of cassava starch/chitosan blends (100/0; 75/25 and 50/50 g/100 g) were prepared from homo pellets and masterbatch-base nanostructured pellets until adjust a final nanocomposite concentration of 0.5 and 1.0 g of nanofillers per 100 g of blend (Fig. 1). The films were obtained by extrusion using a co-rotating twin-screw extruder (Thermo Scientific™ EuroLab 16) equipped with a plate die and was connected to calendaring system (2 Roll Haul 567-5040, Germany) leading to films with 160 mm wide and 0.3 mm thickness. The films based on starch nanostructured with 0.5 g MT/100 g exhibited a water vapor transmission (WVT) of (21.9±1.2) g/m2d, value 52 % less in relation to control film. On other hand, these films show great competitiveness with some already marketed, such as Poly(butylene-succinate) (PBS) Bionolle™ (330 g/m2d) and Poly(butylene adipate-co-terephthalate) (PBAT) Ecoflex® (272 g/m2d) (Robertson, 2013). Subsequently, the films produced from the blends starch/chitosan 75/25 nanostructured with 0.5 g BNFs/100 g exhibited an increase of 24 % in the tensile strength (0.62±0.05) MPa in relation to control films due to strong hydrogen link interaction between the bamboo fibers and polymer matrix. Thus, the processing conditions selected for the extrusion and concentrations of the components allowed a good dispersion of fillers in the biopolymeric matrix leading to improve some physical properties due to the nanoclay exfoliated structure and the intercalated composite in the case of bamboo fibers addition