Antimicrobial and improved performance of biodegradable thermoplastic starch by using natural rosin to replace part of glycerol

To improve the mechanical and water resistance of biodegradable thermoplastic starch (TPS) and endow the material with antibacterial properties, a novel strategy was proposed to use low-cost and renewable rosin to replace some glycerol in traditional TPS with invariable glycerol content. The mechanical properties, fractured cross-section images, crystallization behavior, dynamic mechanical analysis (DMA), water wettability, moisture absorption and antimicrobial activity were systematically evaluated. The tensile and bend strength increased from 1.42 to 4.61 MPa and 0.40–8.33 MPa for pure and rosin-modified 80R-TPS, respectively, indicating an improvement of approximately 3.25 and 20 times; the loss peak at high temperature (Tα) increased from 33.34 to 55.62 °C; the surface contact angle increased from 30.8° to 68.0°; and the equilibrium moisture absorption gain after 970 h decreased from 9.253% to 6.249%. These results proved that the mechanical properties and water resistance of rosin modified TPS produced via extrusion and injection molding were obviously enhanced, accompanied by obvious antimicrobial activity, which has potential application at the commercial scale in food packaging materials and biomedical and agricultural fields.