Thermal characterization of reactive blending of 70PC/30PET mixtures prepared in the presence/ absence of samarium acetylacetonate as a transesterification catalyst

Abstract

Poly(ethylene terephthalate) (PET)/polycarbonate (PC) blends were prepared in the presence and absence of samarium (III) acetylacetonate hydrate [Sm(acac)3] used as an ester-ester exchange reaction catalyst. Differential scanning calorimetry (DSC) and thermogravimetric analysis/differential thermogravimetry (TGA/DTG) were used to study the variations in the thermal properties of blends before and after reactive blending. Solubility measurements in methylene chloride (CH2Cl2) and infrared spectroscopy were also employed to highlight the structural changes that occurred during mixing in the presence of Sm(acac)3. The DSC results showed two distinct transition temperatures (Tg) for all the compositions. Also, the Tg values of components were shifted compared to the parent polymers in both the blends prepared with and without catalyst. Further, the Tg of the PET-rich phase was displaced to higher temperatures and that of the PCrich phase showed a tendency to diminish as the catalyst’s concentration increased. At the same time, the melting temperature (Tm) of the PET-rich phase was shifted to lower temperatures. The evaluation of the compositions of the PC- and PET-rich phases using Wood’s equation showed a strong dependence on the catalyst concentration. Furthermore, the thermogravimetric thermograms showed that the thermal stability of the blends was between those of the homopolymers, and evidenced a net improvement relatively to the neat PET. The obtained results confirmed the aptitude of Sm(acac)3 to promote exchange reactions between PC and PET, and to achieve their compatibilization through an interfacial copolymer synthesis process.