Pyrogallol loaded thermoplastic cassava starch based films as bio-based oxygen scavengers

Abstract

Extrusion of organic oxygen scavenging compounds with starch blend polymers possibly produced bio-based functional materials. Oxygen scavenging polymers were produced by compounding thermoplastic starch (TPS) loaded with pyrogallol (PG) at different concentrations (1–10% w/w) with linear low-density polyethylene (LLDPE) using an extrusion technique. Infrared absorption indicated that PG interacted with both TPS and LLDPE and improved compatibility. Incorporation of PG increased amorphous starch contents and linearly reduced the crystallinity of TPS/LLDPE polymers. Higher phase separation of PG and self-aggregates occurred above 3% PG, concurrent with limited polymer interaction. Microstructure, surface topography and mechanical relaxation were modified with increasing PG content. Oxygen absorption capacity was determined as scavenging rate, with residual oxygen contents at equilibrium during storage at 4, 25 and 50 °C. Oxygen absorption rates strongly depended on PG contents and temperature. Diffusion and interaction between oxygen and PG in the polymers were controlled by molecular mobility, reaction rates and microstructures of the film matrices. Compounding PG with hydrophilic and hydrophobic bio-based polymer blends effectively produced oxygen scavenging materials for functional active packaging of oxygen-sensitive products.