Starch/Poly(ε-caprolactone) Graft Copolymers Synthetized by γ-Radiation and Their Application as Compatibilizer in Polymer Blends

Synthesis of starch-graft-poly(-caprolactone) copolymers (St-g-PCL) was achieved under vacuum by employing low doses of ⁶⁰Co γ-radiation. Irradiation synthesis was carried out by using glass vials containing gelatinized starch suspension and e-caprolactone (-CL) monomer. Two starch:-CL mass ratios were employed 1:0.1 and 1:10. Irradiated samples were exhaustively treated with chloroform in order to remove homopolymer traces. Fourier transform infrared spectra of extracted samples showed a characteristic band associated to stretching vibration of carbonyl group, an indicative that PCL was grafted onto starch backbone. A grafting degree between 9 and 12% was achieved according to thermogravimetric analysis. Thermoplastic starch/PCL blends (TPS/PCL) with different amounts of St-g-PCL copolymers were prepared in order to test their thermal and mechanical properties. The addition of the synthesized copolymer did not show substantial changes over thermal properties, meanwhile significantly increased their maximum tensile strength and Young’s modulus since St-g-PCL enhances the interfacial adhesion between starch and PCL chains.