Branched polyester based on the polyethylene tere/iso phthalate and trimellitic anhydride as branching agent

Branched polyesters based on the polyethylene terephthalate were synthesized by incorporating isophthalic acid (IPA) and trimellitic anhydride (TMA). TMA has the branching agent role. During the esterification step, only terephthalic acid, IPA, and ethylene glycol were reacted and TMA was added at the beginning of the polycondensation step. Reaction progress was studied using water production and mixing torque increase during esterification and polycondensation steps, respectively. Polycondensation time increases with IPA and decreases with TMA. Fourier transform infrared spectroscopy spectrum shows the production of polyester. Randomness and sequence length were studied using 13CNMR. Results reveal that randomness increases with TMA. Crystallinity and morphology of samples were studied using differential scanning microscopy (DSC). DSC thermograms show that samples turn to an amorphous structure by adding IPA and TMA with decreasing glass transition temperature, Tg. X-ray diffraction spectra approve changing nature similar to DSC results. Dynamic light scattering results present that with an increase in TMA, some size-increasing particles were detected. The rheological behavior of samples was studied using RMS. By adding TMA, the elastic behavior of samples changes to viscous behaviors.