Research On Dyeing Process And Mechanism Of Dyeable PP With Disperse Dyes

Polypropylene fiber, Chinese commercial name Bing Lun, is a kind of syntheticfiber from isotatic polypropylene. PP is composed of hydrocarbon chain and withoutpolar functional groups, and has high crystallinity. These features result in poor dyeaffinity, color fastness and color depth of PP. Blend-spinning with modifiedcopolyester is usually adopted to improve the dyeing properties on PP fiber withdisperse dyes. The chemical composition of PP fiber is changed, and thus the fiber haspolyester characteristic groups, lower crystallinity and higher glass transitiontemperature. Then a kind of dyeable polypropylene fiber has been developed. It is ofsignificant importance to study the dyeing properties and mechanism of such dyeablePP for development of novel PP fiber.In this thesis, the dyeable PP fiber with disperse dyes was taken as the mainresearch subject, and the polyester and PP fibers as contrast. Surface morphology,chemical structure, crystallinity, thermal and mechanical properties of dyeable PPfiber with disperse dyes were systematical characterized and analyzed to establish thetheoretical basis for dyeing process.Compared with polyester andpolypropylene fibers, SEM result showed that there were some grooves on the surfaceof dyeable PP fiber. FT-IR analysis confirmed that the dyeable PP fiber had polyestercharacteristic peaks of-OH、-C=O and C6H6. TG and DSC results showed thatthermal stability of dyeable polypropylene fiber was decreased while the crystallinitywas between other two fibers. The glass transition temperature of dyeable PP was47.54℃which was much higher than that of PP, however, the melting temperature ofdyeable PP didn’t change obviously. Physical and mechanical properties analysisshowed that the tensile strength and modulus of dyeable PP fiber was the lowest,while the rupture elongation was between other two fibers.Mono-factor, orthogonal experiments and range analysis were carried out tostudy the dyeing process of PP knitted fabrics which dyed with disperse red FB, disperse yellow E-3G and disperse blue2BLN1%（o.w.f.), and the optimum processwas determined as follows: T=130℃, t=90min, pH=4.5and liquor ratio=1:50.Under this optimum process, the dyeable PP knitted fabric could obtain high dyeutilization and color depth, and color fastness was conformed to the GB18401-2010standard. Despite the index was still lower than that of polyester, it satisfied theapplication requirement. Dyeing trend on dyeable PP with disperse dyes was similarwith polyester, however the lifting force of the disperse dyes on polyester was betterthan on the dyeing PP, and disperse blue2BLN had the highest lifting force. Thecross-section color of dyeable PP with disperse dyes under the optimum dyeingprocess was deep, yet a few white core still existed.On the basis of the optimum dyeing process, trichromatic disperse dyes(disperse red FB,disperse yellow E-3G and disperse blue2BLN) were used to studythe dyeing kinetics and thermodynamics of dyeable PP fiber and polyester fiber withdisperse dyes. The dyeing kinetics results showed that theequilibrium absorption capacity and the dyeing rate were slightly lower, thehalf-dyeing time extended, the diffusion coefficient increased on dyeable PP fibercompared with the PP fiber. The dyeing thermodynamics results showed that thedyeing affinity, dyeing heat and dyeing entropy on dyeable PP fiber were decreased,and the adsorption isotherm of disperse dye on dyeable PP fiber was the same as thaton polyester fiber, and both of them well fitted the Nernst distribution model withlarge liquor ratio.