| Meta-aramid is synthesized by m-phenylenediamine and isophthaloyl dichloride through condensation polymerization. Meta-aramid fiber has excellent heat resistance, flame resistance and textile processing performance. It is often used to manufacture products as heat protective clothings,filters and fire prevention fabrics, which have many applications in military, fire protection and so on.Coloured meta-aramid fibers are often needed in these fields. The meta-aramid is difficult to be dyed due to its close molecular structure, high crystallinity and small pigment molecules can hardly get into the fiber structure. Coloured meta-aramid fibers with good dyeing depth are produced by the dope dyeing method in this study, and the chemical properties, mechanical properties of the fibers are maintained.The properties of some kinds of pigments are analyzed in this thesis, including heat resistant,water resistant, acid resistant, alkali resistance properties, molecular structures, size distribution,dispersive properties and colour rendering properties. Then, three appropriate pigments are chosen from the red, blue and purple pigments which are suitable for the spinning conditions. Measurements show that the pigments have excellent thermal properties, the thermal decomposition temperatures of the pigments are all above 400? w hich can m eet the requirem ents of heat resistant applications. The average diameter of pigments are all below 2500nm, so pigments are easy to disperse in the fibers and can meet the requirements of transparency, colour gloss and colour fastness. The water resistance,acid resistance,alkali resistance and solvent resistance of the pigments are all up to 5 level. Further more, the pigments have the best dyeing depth when the processing temperature is 300?The die-swell behavior of dope dyed meta-aramid solution is studied in this thesis. After analysis and comparison, a appropriate spinneret which is suitable for the dope dyeing spinning of meta-aramid fiber can be selected. When the solution concentration, spinning temperature and other conditions are constant, when the L/D is small, the extrusion die-swell ratio (B) declines significantly with the length and diameter ratio (L/D) increases; When the L/D is over 7, the value of B changes small with the L/D changes. What's more, the extrusion swelling ratio (B) increases with the spinning pressure increases or the temperature decreases in the process of dope dyeing spinning of meta-aramid fiber, therefore, the influence of high temperature can be reduced by increasing the spinning pressure.The process conditions of spinning influence on the performance and structure of the colored PMIA fiber, and these conditions include spinning speed, coagulation bath, etc. The preparation process of the dope-dyed PMIA fiber is wet spinning. The coagulant, solvent and other wet spinning process conditions are very different in the process of the preparation. The spinning dope contains CaCl2 salt and the pigment molecules, so with the use of composition analysis, the determination of the diffusion coefficient has the effect of solvent and non solvent diffusion, because of the addition to the solvent and nonsolvent, these substances will also have the diffusion phenomenon. The solidification mechanism is analysed by using component analysis in this thesis. The mainly studies are the material diffusion of solvent DMAc, non solvent water, and CaCl2 in the liquid color PMIA dope. The content of each component and experimental conditions are determined by using the extraction method on diffusion properties, finally the diffusion coefficient is got, and the relationship between the coagulation bath temperature and the diffusion coefficient ratio of solvent to coagulator is analysed. With the increment of temperature, the diffusion coefficient of solvent and coagulant increases, while the diffusion coefficient of solvent and coagulant ratio (Ds/Dn) decreases. The increment of temperature affectes the diffusion in two aspects. Firstly the increasing temperature impedes the movement capacity of small molecules, this enhances the diffusion coefficient ability;secondly, the increment of temperature resultes in the increment of polymer free volume, and the small molecules have enough space for diffusion. Ds/Dn ratio increases with the increasing temperature, which is probably due to the significant influence of temperature on the solvent. The effect of the jet stretch ratio, and the temperature and concentration of coagulation bath on the ratio of diffusion coefficient of solvent to coagulator are analysed during spinning process of dope-dyed PMIA fibers. The properties and structures of coloured PMIA fibres are characterized by SEM.Finally the most optimized spinning technology of the dope-dyed PMIA fiber is obtained.For further investigation on the double diffusion dynamics process between solid sample and coagulation bath, the curve of residual weight with solidification time in different temperature of coagulation bath is studied by using static rod-shaped gel solidification experiment. The lower the coagulation bath concentration is the smaller the final residual rate would be, after 200Min the sample's residual rate in 60wt% coagulation bath is much lower than it is in the other two coagulation baths that have different concentrations, and its tend wend to flat finally; meantime, the innner structure of solidification spline changes from loose space structure to close pore structure, and solid parts come out gradually. The spline residue rate increases as the solution concentration increases; and from the inner structure after solidification, solid content increases, the number of holes decreases,diameter of hole decreases,the structure becomes relatively denser.The dope-dyed PMIA fibers with different amounts of pigment are prepared by wet spinning.The color fastness of the colored PMIA fibers is tested, and the thermal, mechanical and chemical resistance properties properties of both uncolored and colored PMIA fibers are compared. The Fourier infrared spectroscopy (FTIR) results indicate that the chemical structure of the colored fibers is similar to that of the uncolored ones. The thermogravimetry analysis (TGA) results indicate that the colored PMIA fibers maintaine good thermal and mechanical performance. Moreover, the color of the colored PMIA fibers become lighter than that of uncolored PMIA fibers after exposing to simulated sunlight for 50 h. The breaking tenacity of the colored PMIA fibers exceedes 1.7cN/dtex, and the retentivity is above 70% after the colored fibers are exposed to simulated sunlight for 50h. This also suggestes the good performance of colored PMIA fibers.Further more, the relationship between spinning conditions and mechanical properties is fitted by an equation, and mechanical property data visualization based on the Matlab programming language is carried out. Finally, the optimal spinning process conditions are researched by the fitting equation and the mechanical property data visualization. |
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