Preparation and properties of thermoplastic poly(caprolactone) composites containing high amount of esterified starch without plasticizer

• Stearyl chloride was effective to fabricate esterified starch.
• The torque of PCL/esterified starch (80/20, wt) was low during melt blending.
• PCL/esterified starch (80 wt%) exhibited the improved tensile properties.

Based on stearyl chloride and native starch, esterified starch were prepared and the chemical structure was characterized by 1H NMR and FTIR. It was found that stearyl chloride was an efficient agent to fabricate esterified starch with high degree of substitution (DS). During the melt blending of esterified starch (80 wt%) and poly(caprolactone) (PCL, 20 wt%), it was shown the torque of PCL/esterified starch was much lower than that of PCL/native starch without any plasticizer, and further decreased with increasing DS. Compared with PCL/native starch, the tensile properties of PCL/esterified starch composites were significantly enhanced. The tensile strength and elongation at break were increased from 2.7 MPa to 56% for PCL/native starch composites to 9.1 MPa and 626% for PCL/esterified starch ones with DS of 1.50, respectively. SEM observation revealed the esterified starch particles in matrix became smaller and more uniform. In addition, the water resistance and hydrophobic character of PCL/esterified starch composites were improved. PCL composites containing 80 wt% esterified starch with favorable mechanical properties would have great potential applications in broad areas.