Surface Structural Regulation And Color Construction Of Meta-aramid Fiber

Owing to the superior thermal stability and mechanical properties,meta-aramid(MPIA)fiber and its structural composites have considered a good replacement to metal materials in the development of lightweight field.Therefore,MPIA fiber is widely used in military and national economic fields,which has become an irreplaceable key material for national construction.However,there are also some drawbacks of MPIA fiber,such as poor dyeability,poor UV resistance,and low interface interactions,which significantly restrict the development and application of MPIA fiber.Therefore,the key to solve the‘short board'problem is to control the macromolecular structure of MPIA fiber without affecting the excellent performance.On this basis,the dyeing of MPIA fiber can be realized.Then it can further expand its application in national defense,civil and other fields.Herein,this thesis will mainly focus on the above‘short board'problem to explore the following investigations:(1)N,N-Dimethylacetamide(DMAC)with mature recovery technology was selected as the regulator of intermolecular hydrogen bond of MPIA.The feasibility of controlling intermolecular hydrogen bond of MPIA fiber was discussed in detail.Based on the effects of DMAC on the dyeing of MPIA fibers with different charge molecules and the agglomeration behavior of dyes,the theory of accelerating dyeing with DMAc?Dye~+system was proposed.The results showed that the synergistic effect of DMAC and NaCl could significantly improve the dye penetration of cationic dyes into fibers.Additionally,the dyed MPIA fiber exhibited the good washing and wet rubbing fastnesses,which has demonstrated that the theory of accelerating dyeing with DMAc?Dye~+was correct.(2)According to the previous theory,the hydrogen bond interactions between the aramid macromolecules could be regulated in the presence of DMAc.Therefore,based on the theory that disperse dyes could easily be sublimated at high temperature.In this chapter,the relatively dye concentrations around the MPIA fiber was improved by limiting the flow space of the vaporized disperse dyes and DMAc molecules.Moreover,the dyeing mechanisms of disperse dyes onto the MPIA fiber in a hot-pressed environment was established by analyzing the aggregation behaviors of disperse dyes in DMAc solutions.The results showed that DMAC could significantly reduce the aggregation of disperse dyes in dye solution,and most importantly,DMAC also provides convenient conditions for the sublimation of disperse dyes by breaking the intermolecular hydrogen bonds of MPIA.The apparent color depth and dye penetration of MPIA fibers were effectively improved with the addition of high concentration of DMAC.Moreover,the thermal stability of MPIA fiber was improved to some extent.This further proves that the particle flow dyeing technology formed by DMAC combined with hot pressing process is efficient and feasible in improving the dyeing performance of MPIA.(3)In this chapter,the surface structure of MPIA fiber was further regulated and the concept of micro-dissolution was proposed.By using the force of directed airflow,the inorganic pigment particles adsorbed on the fiber surface were embedded onto the fiber surface in situ to form an inorganic pigment particle composite material based on MPIA.Inorganic pigment particles,such as P.R.101,P.Y.42,P.B.27 were selected for in-situ compounding of the MPIA fiber in a directional airflow field.The dyed samples showed high apparent color depth,ironing sublimation fastness,and sunlight fastness,which reveals that the amount of colored inorganic particles embedded in the fiber surface was relatively higher,and the combination of colored inorganic particles and MPIA was better.The in-situ composite technology of directional airflow field showed little effects on the thermal stability and mechanical properties of MPIA,which further indicates that the combination of micro-dissolution and directional airflow field is suitable for the color construction of MPIA fiber.(4)In order to improve the interface fastness of inorganic pigment particles and MPIA composite,taking advantage of the rapid gasification characteristics of DMAc in a high temperature(175?)environment,combined with the conclusion that MPIA fiber can rapidly form micro-dissolution layer on the surface under the action of temperature and DMAc/LiCl,the inorganic pigment particles were embedded in the MPIA in the DMAc transient gasification environment to achieve the efficient construction of MPIA color.By examining the effects of LiCl concentration in the inorganic pigment particle solution and treatment time in oil bath on the color and strength of MPIA,the optimal process for controlling the micro-dissolution layer of MPIA fiber in DMAc transient gasification environment was determined.And the interface fastness of pigment particles and MPIA was examined through the test of washing and rubbing fastness.The proposed dyeing technology suggests that the disperse dyes and organic pigment P.R.254 could be well applied for the color construction of MPIA fiber,which further verifies that it has wide applicability and strong operability in the controllable color construction of MPIA.In summary,this thesis investigates the regulation of hydrogen bonds in MPIA fiber,which plays an essential role in promoting the affinity between dyes and fiber.Additionally,the coloration technology of combining micro-dissolution layer with pressure to form inorganic particles-MPIA composites on the fiber surface was proposed,which significantly improved the interface fastness of the composite and simplified the modification process simultaneously.Therefore,this research may serve as a mechanistic guide for the efficiency dyeing of high-performance fibers.