Relationship between miscibility and chemical structures in reactive blending of poly(bisphenol A carbonate) and poly(ethylene terephthalate)

Commercial poly(bisphenol A carbonate) (PC) and poly(ethylene terephthalate) (PET) were directly melt mixed without adding any catalyst. The changes of miscibility and chemical structures during reactive blending were detected by high-field nuclear magnetic resonance spectroscopy and differential scanning calorimetry, respectively. It was found that transesterification significantly improved the miscibility between PC and PET. About 5% reaction extent was sufficient to change the blend system from initial immiscibility to miscibility. The single glass transition temperature of the miscible product did not change with further increasing extent of reaction. However, excessive exchange reaction caused severe decarboxylation and thus introduced a number of aromatic–aliphatic ether moieties into the products. As a result of the homogenization, both exchange and decarboxylation reactions were subsequently speeded up. The quantitative analysis provided a possibility to design the resultant chemical structures while producing miscible PC/PET alloy.