Preparation and properties of compatible starch-polycaprolactone composites: Effects of hard segments in the polyurethane compatibilizer: Preparation and properties of compatible starch-polycaprolactone composites

Cross-linked poly(ester urethane)/starch composite films with high starch content as sustainable food-packaging materials: Influence of cross-link density

This study focused on the development of cross-linked poly(ester urethane)/starch (PEUST) composites containing 50 wt% starch content for food-packaging materials. The NCO-terminated poly(caprolactone-urethane) prepolymer (PCUP) was first synthesized through bulk condensation. Then, low-moisture starch (0.21 wt%) and PCUP-based PEUST films were fabricated through an intensive extrusion process, followed by thermo-compression molding. The chemical structure of PCUP and PEUST was confirmed using Fourier transform infrared spectroscopy. Moreover, a comprehensive evaluation was conducted to assess the influence of cross-link density on the physicochemical properties of the composite films. The results showed that an increase in the cross-link density within the composites improved component compatibility and tensile strength but reduced crystallinity, water sensitivity, hydrolytic degradability, and water vapor permeability (WVP) of the films. In addition, the cytotoxicity tests were conducted to evaluate the safety of the composite films, and the high cell viability demonstrated non-toxicity for food application. The PEUST-II films with moderate cross-link density exhibited a suitable degradation rate (27.7 % weight loss at degradation for 140 d), optimal tensile properties (tensile strength at break: 12.4 MPa; elongation at break: 352 %), and low WVP (68.4 g/(m2⋅24h) at 30 % relative humidity). These characteristics make them highly promising as fresh-keeping food packaging.

Starch-based isocyanate- and non-isocyanate polyurethane hybrids: A review on synthesis, performance and biodegradation

The challenges related to the persistence of plastics in natural ecosystems fostered strong interest in developing biodegradable bioplastics. Among natural biopolymers, starch gained both academic and industrial interest owing to its impressive physicochemical properties. The use of starch in production of polyurethane (PU) composites not only yields PUs with outstanding mechanical properties but also makes the final PU products biodegradable. The hydrophilic nature of starch limits its dispersion in hydrophobic PU polymers, although it is a significant benefit in creating starch-embedded non-isocyanate polyurethane (NIPU) composites. We present a comprehensive overview to highlight important strategies that are used to improve the compatibility of starch with various PU matrices. This review also gives an overview of the recent advances in the synthesis of starch-NIPU hybrids. Moreover, we aim to deliver critical insight into strategies that boost the biodegradation characteristics of PUs along with a discussion on various methods to assess their biodegradation.