Effect of citric acid on the properties of thermoplastic bitter cassava starch plasticized with isosorbide

The rising concern of environmental issues from the non-degradable conventional polymers is triggering the development of sustainable and renewable polymers. Thermoplastic starch (TPS) has been known to have huge potential to substitute conventional synthetic polymers. A thermoplastic starch was prepared using a non-food bitter cassava starch with isosorbide as plasticizer. To improve the dispersion and interfacial affinity of thermoplastic starch and boost the compatibility between starch and isosorbide, citric acid (CA) was used as an additive. The influence of citric acid to the TPS was then investigated. The result shows that citric acid improved tensile strength from 8.68 MPa to 11.98 MPa. The addition of citric acid at a concentration of 1 – 10 wt % can increase glass transition temperature (T g ) from 48.81°C to 63.89°C and storage modulus at 25°C from 1.20 GPa to 3.47 GPa. Two degradation temperatures (T d ) were detected which are T d1 onset value was decrease from 83.32°C down to 79.78°C while T d2 onset value was decrease from 275.29°C down to 247.17°C and T d2 max from 311.12°C to 295.06°C.