Preparation and characterization of poly (butylene terephthalate)/graphene composites by in-situ polymerization of cyclic butylene terephthalate

The ultra-low viscosity of cyclic butylene terephthalate oligomers has been exploited to perform their in-situ ring-opening polymerization in the presence of graphene, to obtain homogeneously dispersed poly(butylene terephthalate)/graphene (PBT/G) composites containing 0.5 to 1.0 %wt of graphene. The results of gel permeation chromatography show that increasing amounts of graphene causes a decrease in the average molecular weight of PBT if the time of polymerization is kept constant, and morphological investigations performed by electron microscopy and x-rays diffraction show that high levels of dispersion of the G sheets are easily obtained by this method of composites processing. Thermal properties of the composites were studied by differential scanning calorimetry and thermogravimetric analysis; results indicate that increasing amounts of G do not strongly influence the degree of crystallinity and the crystallization temperature of PBT, while its thermal stability is significantly increased by the presence of G. All the PBT/G composites demonstrated to be electrically conductive; we found that the electric field assisted thermal annealing of the PBT/G composites induces an increase in conductivity.