Effect of phase inversion on the physical and mechanical properties of low density polyethylene/thermoplastic starch

Blends of low density polyethylene (LDPE) and thermoplastic starch (TPS) containing low density polyethylene-grafted-maleic anhydride (LDPE-g-MA) as compatibilizer were prepared with various TPS contents. The effects of phase inversion on the morphological, static and dynamic mechanical and permeability properties of the blends were investigated. It was found that the morphology of the blend is matrix-droplet until the TPS content exceeds 75 wt%, when phase inversion occurs. The mechanical properties and glass transition temperature of the starch-rich phase decrease with increase of TPS content, and these reductions are more significant near the phase inversion point. The long term water absorption data of the blends were used to obtain the diffusion, solubility and permeability coefficients. The permeability properties of the blends change gradually at low TPS concentration, and the rate of these variations accelerates around the phase inversion point. Various models were used to predict these properties at different TPS contents.