Preparation and properties of plasticized starch modified with poly(ε-caprolactone) based waterborne polyurethane

Biodegradable blends were prepared successfully from plasticized starch (PS) and poly(ε-caprolactone)-based waterborne polyurethane (WPU) by casting and evaporation. The morphology, thermal behaviour, and mechanical properties of the films were investigated by means of wide-angle X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and tests of mechanical properties and water absorption. The results indicated that the blends had a good miscibility while the WPU content was lower than 20 wt% due to the hydrogen bonding interactions between the carboxyl, carbonyl, urethane groups of WPU and hydroxyl groups of starch, whereas the phase separation occurred with an increase of WPU content. Compared with pure PS, the tensile strength of the blend containing 10 wt% of WPU increased from 2.93 to 3.89 MPa. Moreover, the elongation at break of the blends significantly increased from 35% to 886% with WPU content increased from 0 to 50 wt%. It is worth noting that the water uptake of the PS/WPU blends also decreased because the presence of WPU in the PS matrix. Therefore, the WPU played an important role in improving the mechanical properties, and water resistance of the starch-based material.