Copolyesters from 1,4-butanediol, dimethyl terephthalate and either 2,3:4,5-di-O-methylene-galactitol or dimethyl 2,3:4,5-di-O-methylene-galactarate with compositions of 10, 20, 30, 40 and 50% of either galactitol or galactarate units were prepared by melt-polycondensation. The copolyesters had Mw in the 32,000–41,000 g mol−1 range and had a random microstructure. They displayed Tg from 20 to 70 °C with values steadily decreasing with the content in galactarate units but increasing with the content in galactitol units. All the copolyesters were semicrystalline with Tm between 115 and 210 °C and they adopted the crystal structure of PBT. Copolyesters containing up to 20% of galactitol units as well as all galactarate copolyesters were able to crystallize from the melt, at a crystallization rate that decreased with the content in carbohydrate-based units. Stress-strain essays revealed an increment in the tensile strength and elastic modulus with increasing contents in galactitol units whereas these parameters decreased when galactarate units were the replacing ones.

Peer Reviewed