The crystallization behaviors of poly(butylene terephthalate) blended with co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters

Poly(butylene terephthalate) (PBT) was blended with three different kinds of co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters, designated B28, B46, and B64, with the copolyester level varying from 2 to 15 wt.%. All samples were prepared by solution blending in a 60/40 by weight phenol/tetrachloroethane solvent at 50°C. The crystallization behavior of samples was then studied by DSC. The results indicate that these three copolyesters accelerate the crystallization rate of PBT in a manner similar to that of a nucleating agent. The acceleration of PBT crystallization rate was most pronounced in the PBT/B28 blends with a maximum level at 10 wt.% of B28. The melting endotherm onset temperatures and the melting peak widths for the blends are comparable with those of pure PBT. These results imply that the stability of PBT crystallites in the blends is not significantly influenced by blending. The observed changes in crystallization behavior are explained by the effect of the composition and the amount of copolyester in the blends.