Blends of poly(epsilon-caprolactone-b-lactic acid) and poly(lactic acid) for hot-melt applications

摘要

The condensation reaction product of poly(lactic acid) (PLA) and a hydroxyl-terminated four-armed poly(epsilon-caprolactone) (PCL) was studied by size-exclusion chromatography, DSC, and NMR. The use of both L-lactic acid (LLA) and rac-lactic acid (rac-LA) was studied and the use of two different catalysts, stannous 2-ethylhexanoate [Sn(OCt)(2)] and ferrous acetate [Fe(OAc)(2)], was also investigated. The thermal stability and adhesive properties were also measured for the different formulations. The characterization results suggested the formation of a blend of PLA and a block-copolyester of PLA and PCL. The results further indicated partial miscibility in the amorphous phase of the blend showing only one glass-transition temperature in most cases, although no randomized structures could be detected in the block-copolymers. The polymerization in the Fe(OAc)(2)-catalyzed experiments proceeded slower than in the Sn(Oct)(2)-catalyzed experiments. The discoloring of the polymer was minor when Fe(OAc)(2) was used as catalyst, but significant when Sn(Oct)(2) was used. The ferrous catalyst also caused a slower thermal degradation. Differences in the morphology and in the adhesive properties could be related to the stereochemistry of the poly(lactic acid). (C) 2003 Wiley Periodicals, Inc. [References: 62]