Preparation And Propetries Of Modificated Titanium Dioxide/PA6Conductive Fiber

The white conductive fibers have been intensively produced by several large foreigncompanies, the production of them in our country is almost zero to the best of our knowledge.In order to change the import dependence of white conductive fibers for our country, a whiteconductive fiber was designed and prepared in this thesis.First, the conductive titanium dioxide was prepared by chemical coprecipitation method;then the conductive titanium dioxide was modified by solution of sodium hexametaphosphatefor promoting the dispersion of conductive titanium dioxide in polymer matrix; finally theconductive fiber was prepared through melt spinning. The mechanism of surface modification,effect of modification on crystal structure of conductive titanium dioxide and dispersion ofconductive titanium oxide in PA matrix were studied in detail. The conductive fibercontaining different content of titanium dioxide were prepared by melt spinning. The effect oftitanium dioxide content on the thermal properties and conductive mechanism were discussed.Finally, the ideal content of titanium dioxide and optimum industrial production conditionswere determined.The conductive titanium dioxide can aggregate easily in PA matrix, which reduces thecrystallinity of PA significantly. For this reason, the surface modification of conductivetitanium dioxide is required for preparing high performance conductive fiber. The resultsshow that the crystal structure of titanium dioxide was not destroyed by the surfacemodification, and the modified conductive titanium dioxide (MCTD) show goodcompatibility with PA matrix, which can promote the dispersion of conductive titaniumdioxide in PA matrix effectively. The good dispersion of conductive titanium dioxide in PAmatrix make each the conductive titanium dioxide form a crystal nucleus in PA blends, whichis beneficial to improving the crystalline of PA. In addition, the rod-shaped conductivetitanium dioxide can form three-dimensional network structure in PA matrix if it welldisperses in the PA matrix, which in conducive to forming conductive path in PA matrix, sothe PA/MCTD blends show good conductivity.XRD results show that the crystal structure of MCTD is not change after hightemperature mets spinning, which provises a theoretical feasibility of production ofconductive fiber by melt spinning. The melting temperature (Tm) of PA/MCTD conductivefiber is lower than that of pure PA polymer when the content of MCTD is less than7wt%,while the Tm of PA/MCTD conductive fiber is higher than that of pure PA polymer when thecontent of MCTD is larger than10wt%. The possible reason is that the amount of crystalnucleus is smaller than that of pure PA polymer, which rusting in lower crystallinity ofPA/MCTD conductive fiber, so the Tm is lower than that of pure PApolymer; however, whenthe content of MCTD is larger than10wt%there are more crystal nucleus in PA/MCTD conductive fiber, therefore the crystallinity of PA/MCTD conductive fiber is higher than thatof pure PApolymers. The conductive mechanism studies show that the conductive mechanismis tunnel conductivity when the content of MCTD is smaller than7wt%and the ohmicconductivity is the main mechanism when the content of MCTD is larger than13wt%. Whenthe content of MCTD is between10wt%and13wt%both tunnel conductivity and ohmicconductivity exist in PA/MCTD conductive fiber. The conductivity of PA/MCTD fiberincreases with the increasing of content of MCTD, however the conductivity increases slowlywhen the content of MCTD is larger than16wt%. Therefore, the content of MCTD inPA/MCTD conductive fiber is16wt%based on the economic benefits and processingconditions.The prepared PA/MCTD white conductive fiber can overcome dark problems oftraditional carbon-based conductive fibers, which expands the application of conductive fibersin industry. PA/MCTD white conductive fiber was successfully prepared in this thesis, whenthe content of MCTD is16wt%, the volume resistivity of PA/MCTD conductive fiber is up to105Ω cm.