Mechanical Properties and Biodegradability of Polypropylene/Starch Reinforced Nanoclay Blends

Polypropylene/starch nanocomposites compatibilized with PP-g-MA or EVA, with values 0, 3 and 5 wt% of modified clay (Cloisite 30B) were prepared by melt intercalation technique and the mechanical properties, morphology and degradation of nanocomposites were investigated. Tensile test results showed that in the presence of 5 wt% nanoclay, values of tensile strength, elastic modulus and elongation-at-break are 15.5 MPa, 10.2 MPa and 4.2% for PP-g-MA compatibilized blends and 10.0 MPa, 7.0 MPa and 19.4% for EVA compatibilized blends, respectively. Also, the presence of 5 wt% nanoclay increased 9.1 % of tensile strength; 70 % of elastic modulus and decreased 49% of elongation-at-break for PP-g-MA compatibilized blends and increased 40.8% of tensile strength; 27.3% of elastic modulus and 49% of elongation-at-break for EVA compatibilized blends. The reason for these properties improvement could be proper dispersion and physical network consisting of silicate layers in the polymer matrix. SAXS patterns and TEM images confirmed that the prepared nanocomposites were exfoliated. SEM microscopic images show droplet morphology that is indicative of incompatibility of two polymers. Oxidative degradation of samples exposed to UV light was studied using FTIR spectroscopy. The weight loss percentage of MA-5, EVA-3 and EVA-5 specimens after 120 days of exposure in activated sludge resulted in 20.7, 28.4 and 37.9%, respectively. These results indicate that biodegradation of EVA compatibilized blends is much higher with increasing nanoclay which has improved the biodegradablility of the blends.