Supercritical CO2 Assisted Polyethylene Terephthalate/Polybutylene Terephthalate Beads Foaming
Polybutylene terephthalate(PBT)is widely used in PET/PBT alloying due to its similar chemical structure,similar melting temperature and complementary properties such as crystallization rate and melt strength.PET/PBT foamed beads were prepared by supercritical CO2 foaming by using chain extender ethylene-methyl acrylate copolymer grafted glycyl methacrylate(EMA-g-GMA)and carbon nanotubes(CNTs)to modify PET/PBT.The results show that the addition of EMA-g-GMA(EG)can expand the chain and increase the cross-linking degree and viscoelasticity of the systems.The addition of CNTs effectively improves the stability and viscosity of the systems,and delays the degradation of PET/PBT matrix.At the same time,the addition of CNTs can induce crystallization and accelerate the crystallization rate.The addition of EG and CNTs can increase the cell density,make cell distribution more uniform,improve the cell structure,and reduce the foamable temperature from 260 ℃ to 200 ℃.Compared with PET/PBT,the tensile strength of PET/PBT/EG,PET/PBT/CNTs and PET/PBT/EG/CNTs is increased by 97％,67.6％and 79.3％,respectively,and the elongation at break is increased by 93.4％,57.4％and 80.3％,respectively.
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