Physical and Degradation Properties of Polylactic Acid and Thermoplastic Starch Blends – Effect of Citric Acid Treatment on Starch Structures

The physical and degradation properties of polylactic (PLA)/thermoplastic starch (TPS) blends after TPS modification with citric acid (CA) were investigated. The interfacial adhesion between the PLA and TPS was expected to improve, thus enhancing the physical properties of the PLA/TPS blends. The tensile strength and Young’s modulus for PLA/TPS blends at (60/40) and (40/60) blends ratio were found to increase after modification with CA. On the other hand, the elongation at break of the (60/40) blend decreased, while elongation at break of the (40/60) blend increased. Meanwhile, an additional peak at 1721 cm-1 was detected by the FTIR spectroscopic analysis, which indicated that the TPS had chemically interacted with the CA. The biodegradability properties of PLA/TPS blends were also improved after treatment with CA. The deterioration of PLA/TPS blends was attributed to the incorporation of CA; O2 from the soil was attracted to the PLA/TPS blends, thus speeding up the degradation process of the blends.