(161an) Chain Extension of Carboxylic Acid Capped Polyesters Via Methylene Malonate Chemistry

During the mechanical recycling process, post-consumer recycled (PCR) plastics undergo degradation, resulting in poor mechanical properties compared to virgin polymers. To create products with acceptable properties, PCR polymers are combined with virgin, petrochemical polymers, making it difficult to enable a circular economy. Reactive chain extension increases mechanical properties by linking together the ends of polymer chains and increasing molecular weight in situ. Commercial chain extenders, such as pyromellitic dianhydride (PMDA), have limited success in poly(ethylene terephthalate) (PET) because PMDA reacts with hydroxyl end groups, which are abundant in virgin polyesters. In PCR polymers, however, degradation increases the ratio of carboxylic acid chain ends, decreasing the efficiency of PMDA as a chain extender. In this work, we hypothesize that methylene malonates, which initiate from carboxylate salts, can be used to chain extend polyesters with carboxylic acid end groups via reactive processing. We demonstrate the conditions by which this process occurs on a model polyester with known carboxylic acid end groups. This preliminary work suggests that reactive chain extension with multifunctional methylene malonate molecules can increase the molecular weight of PCR, thus potentially enabling better mechanical properties for materials made from recycled polymers.