Synthesis,structure and properties of CET/CBT ring-opening copolymerized polyesters
Ring-opening copolymerization of cyclic ethylene terephthalate(CET)oligomer with cyclic butylene terephthalate(CBT)oligomer can reduce polymerization temperatures and produce polyesters with adjustable properties.Copolyesters were synthesized by ring-opening copolymerization using self-prepared CET and commercial CBT,and effects of CET/CBT mass ratios in feed monomer on molecular weights,compositions and sequence structure,crystallization,melting,and dynamic viscoelastic behavior of copolyesters were investigated.Copolyesters with high molecular weights can be prepared through ring-opening copolymerization of CET and CBT for 10 min at 300℃,especially for copolymerization system with CET mass fraction from 50%to 60%.When the ratio of w(CET)to w(CBT)is greater than or equal to 1:1,the molecular chain has a high degree of randomness.The copolyester with 50%mass fraction of CET has the lowest crystal melting temperature(181.1℃),while the copolyester with 70%mass fraction of CET has the lowest crystallization rate.The storage modulus and glass transition temperatures of copolyesters are increased as CET composition in copolyester increased.
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