Effect of oxidized, maleate and dual chemical modification through extrusion on thermoplastic starch properties

Global growing concern on plastics disposal and their environmental impact has impulsed the development of lower impact biodegradable plastics, however their functional properties and processability are still limited. In this study, thermoplastic starch (TPS) was synthetized through reactive extrusion (REX) to obtain single oxidized thermoplastic (O-TPS) and single maleated thermoplastic (MA-TPS), as well as, dual (oxidized-maleated thermoplastic (O-MA-TPS) modified starches aiming to incorporate new functionalities, diminish the viscosity and improve TPS processability. Spectroscopic analysis showed different band intensities as a result of TPS modification. TPS presented B-type and V-type crystal structures. O-MA-TPS showed the lowest percentage of crystallinity and complex viscosity values compared to single modified TPS because the combination of modifications. The specific mechanical energy decreased with respect to chemical modifications of starch (TPS > O-TPS > MA-TPS > O-MA-TPS), which were associated with the diminishing of viscosity resulting from the modification and starch-glycerol interactions. These starches can be incorporated into mixtures with other plastic polymers, by allowing better mixing (minor viscosity difference) and the replacement of a greater amount of plastic with TPS or in applications where a TPS with lower viscosity and easier processability is required.

Automated summary

Global concern over plastic disposal and its environmental impact has led to the development of biodegradable plastics with lower impact. However, their functional properties and processability are still limited. In this study, thermoplastic starch (TPS) was synthesized through reactive extrusion (REX) to improve TPS processability and incorporate new functionalities. Different modifications of TPS resulted in varied band intensities and crystal structures. The combination of modifications in O-MA-TPS showed the lowest crystallinity and viscosity values, leading to improved performance. These starches can be mixed with other plastic polymers for better compatibility and increased use of TPS in applications where lower viscosity and easier processability are required.