Evaluation of Thermo-Mechanical Properties of Thermoplastic Starch Blend Obtained by Reactive Melt Processing in Presence of Organic Acids

Starch-based materials are a diverse and rapidly growing class of bio-based, biodegradable, and renewable materials derived primarily from plant starch such as corn, potato, tapioca, wheat, rice, etc. They can offer a sustainable alternative to conventional petroleum-based plastic. Starch-based polymer bio-blends were prepared with different glycerol levels (32%, 28%, and 26%) in the presence of two carboxylic acids to compare the potential of malic acid to citric acid and to increase the bio-based content in the thermoplastic material. The viscosity of the starch suspension remains unaffected by the presence of acid but residual acidity significantly influenced the properties and the processing. The presence of acid enabled a high bio-based content and created a link between the plasticizer and starch. The thermoplastic starch exhibited a 288% improvement in mechanical properties with 0.167% (w/w) acid. Reducing the acid content resulted in materials with enhanced thermal and mechanical properties. Malic acid demonstrated promising results and behaved similarly to citric acid, suggesting it could serve as an alternative coupling agent to citric acid.