ABSTRACT
The growing waste of plastics in the environment coupled with concerns about future oil shortages has increased interest in biodegradable polymers such as starch. In recent years, starch has been used in blends with different synthetic polymers. Such blends have been compatibilized by the use of compatibilizing agents of the copolymer type. In this study, the morphological, mechanical and thermal properties of polypropylene (PP)/thermoplastic starch (TPS) blends obtained in the presence of the compatibilizing agent (PP-g-MA) were evaluated. The thermoplastic starch was obtained in a single screw extruder with 20% (mass/mass) of glycerol used as plasticizer. PP/TPS blends were prepared by melt mixing in a co-rotating twin-screw extruder. The concentration of the compatibilizing agent was 3, 5 and 7% (mass/mass). The morphology of the blends was evaluated by scanning electron microscopy. The results showed a significant reduction of the dispersed starch phase with the addition of the PP-g-MA. The blends obtained in the presence of PP-g-MA showed a more homogeneous distribution of the starch phase in the PP matrix. The results obtained with the tensile tests showed that the elastic modulus of PP undergoes a slight increase with the addition of the starch and the compatibilizer. The tensile strength of the PP was not significantly affected. However, there was a significant decrease of the elongation at break with the incorporation of starch. The starch incorporated in the PP matrix led to a significant increase in the impact strength of the final material. However, with the addition of PP-g-MA to the PP/TPS blend, the impact strength falls. This result can be attributed to the reduction of the starch phase in the PP matrix. The thermal stability of the PP/TPS blends was slightly increased with the incorporation of the compatibilizing agent. The materials obtained can be used instead of PP.
Keywords
Polypropylene; Thermoplastic starch; Blends; Morphology; Compatibilizing agent
