Synthesis and characterization of kraft lignin-graft-polylactide copolymers

초록

The graft polymerization of polylactic acid (PLA) onto methanol-soluble kraft lignin (MeKL) was performed successfully through acylation substitution using chlorine-terminated PLA with a number average of molecular weight (M (n)) of 5400-24,000 g/mol. As the M (n) value of the PLA used for the graft polymerization process was increased, the obtained MeKL-g-PLA copolymers decreased from 9,000,000 to 1,100,000 g/mol. The structural characteristics of the MeKL-g-PLA copolymers were analyzed using Fourier transform infrared and H-1 nuclear magnetic resonance spectroscopies. It was found that the thermal properties of the MeKL-g-PLA copolymers improved slightly, with their glass-transition temperature increasing to a level higher than that of pure PLA. The tensile strengths and elasticity modulus of the MeKL-g-PLA copolymers were independent of the M (n) value and were 3.5-3.8 MPa and 0.038-0.045 GPa, respectively.

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