Compatibilization Mechanisms of Telechelic Polyethylene Reactive Additives in Polyethylene Terephthalate/Polyethylene Blends

Imperfect sorting of mixed plastic waste in mechanical recycling processes often results in phase-separated polymer blends that are brittle and no longer suitable for the applications served by the virgin materials. Through compatibilization, phase-separated blends can exhibit properties in between their constituent homopolymers, making them more attractive and valuable. In this work, we develop a deeper understanding of reactive blend compatibilization using hydroxy telechelic polyethylene additives in blends of glycol-modified polyethylene terephthalate and polyethylene. A series of staged mixing experiments (i.e., premixing in either phase vs. single batch mixing) at temperatures ranging from 210°C to 270°C suggests that preformation of copolymer is key for successful compatibilization of this system at lower temperatures, as determined by tensile testing and imaging of the macro-phase separated structure. Copolymer formation as a function of mixing time and temperature was estimated using differential scanning calorimetry, yielding an estimated activation energy of around 89 kJ/mol, similar to previously reported values for transesterification reactions. In total, this work provides an understanding of both the mechanism and limitations of reactive telechelic PE additives as compatibilizers in polymer blend systems.