| Poly(ethylene terephalate)(PET)is a polymer with relatively low cost,thermal stability,excellent chemical resistance and spinnability,and the PET fibers have high strength and elasticity modulus.It is widely used in various fields such as packaging,engineering plastics and electronic,especially in the field of PET fibers and fabric.Until now PET fibers have become one kind of fibers which has the largest output and fastest growing.However,pure PET also has a lot of disadvantages such as high crystallinity,the symmetrical structure of PET chains,no hydrophilic groups but only ester groups with low polarity,which limited dyeing and comfort of PET fibers to a certain extent.More and more attentions have been paid on montmorillonite(MMT)in both academic and industry fields because montmorillonite has high ionic exchange ability,large surface area and strong capability of absorption.To improve structural shortcomings of PET,layered silicates,such as montmorillonite,and another monomer-isophthalic acid have been used to prepare copolyester(PET/PEI)/MMT nanocomposite,so the dispersion of montmorillonite and influence of monomers on structure of PET chains are the key which could improve performances of hybrids materials.In this study,DMT and EG were used to prepare copolyester/MMT hybrids,with montmorillonite as inorganic fillers and the third monomer-isophthalic acid and through in-situ interlayer polymerization.The main researches focused on copolyester/MMT nanocomposites were as following:(1)The intercalating agents between the galleries of montmorillonite sheets increased the d001-spacing of montmorillonite and the surface properties of MMT were changed from hydrophily to hydrophobicity.The results showed that C12PPh-MMT and CEOM-MMT can be prepared through suitable solvents,ratio of materials,reaction time and agitation velocity.Compared to Na-MMT,organic MMT,such as DK2,C12PPh-MMT and CEOM-MMT,have better compatibility with PET matrix and larger d001-spacing.MMT modified with ester quaternary phosphonium salt was well dispersed in the solvent-EG,which facilitated the dispersion of MMT in the PET matrix.(2)PET/MMT containing different kinds and different contents of MMT was prepared by in-situ interlayer polymerization.FESEM,TEM and WAXD were used to investigate the dispersion of montmorillonite modified by different kinds of intercalating agents.Organic montmorillonite had better compatibility with PET matrix than Na-MMT.It was proved that ester at the end of ester quaternary phosphonium salt could react with PET monomers(BHET)or oligmers.It was also proved that higher stabilities of PET/C12PPh-MMT and PET/CEOM-MMT were found comparing with PET/DK2.MMT can change the crystalline of PET,which had a significant impact on dyeing of PET.(3)Isophthalic acid is a common monomer for the preparation of modified PET.Through researches on crystalline of copolyester/MMT,we could find that crystallinity of copolyester/MMT decreased with increase of the contents of IPA.This facilitated our following work.(4)According to the studies above,it was determined that copolyester/MMT nanocomposite containing 0.5%DK2,7%IPA was better.And nanocomposite fibers are prepared by melt spinning.Morphology of copolyester/MMT hybrid fiber was examined by scanning the fracture of fibers through FESEM.DK2 was well dispersed in the PET matrix.Mechanical properties and dyeing properties of modified fibers were significantly improved by adding IPA and DK2. |
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