Starch/Poly(butylene succinate) Compatibilizers: Effect of Different Reaction-Approaches on the Properties of Thermoplastic Starch-Based Compostable Films

The property profile of thin thermoplastic starch (TPS)/poly(butylene succinate) (PBS) films was investigated and the potential improvement, which can be achieved due to the utilization of hydrophilic/hydrophobic compatibilizer systems, was assessed. The evaluation in terms of morphology exhibited a very good TPS dispersion (under optimized processing conditions) within the polyester matrix, while an average particle size of 1.5 µm was obtained. Two different raw material approaches were applied for the preparation of the compatibilizers: (a) native corn starch and (b) destructurized TPS. In the course of the compounding process 0.5 and 1.0 wt% of the two compatibilizer systems (a) and (b) were added. In comparison, the addition of the TPS-based compatibilizer resulted in improved incorporation of TPS within the polyester matrix, which was accompanied by higher tensile strength and tear resistance. Explanations for this observation could be that pre-plasticized starch provides a larger reaction surface and enables better homogenization during the course of compounding. In contrast, for native starch the reaction only can take place at the granule surface and thus, the compatibilization was less efficient. The outcome of this investigation is a compostable film material with high bio-based content, which exhibits great potential for single-use, light-weight packaging applications.