Preparation Of Thermochromic Liquid Crystal Microcapsule And Its Application On Textile

Cholesteric liquid crystal(CLC)is sensitive to temperature change.It is non-toxic to human body,and its range of color change is wide.It is so reasonable to be used in thermochromic fabrics preparation.CLC was therefore explored in this thesis to find their probable application.Thermochromic liquid-crystal microcapsules of cholesteric liquid crystal(CLC)as core material and melamine-formaldehyde(M-F)as shell material were prepared by in-situ polymerization.Its color change temperature was close to human body.Then the CLC microcapsules were treated on the fabric by impregnation method and coating method respectively,L*a*b* values were obtained,it confirmed the treated fabric had positive color change performance,and other properties were tested and analyzed.(1)In order to obtain the liquid crystal material with similar color change temperature range to human body,COC and CPE were mixed according to a certain proportion,and it was found that the optimum mixture ratio is 1: 1.And then,red,yellow,green,blue and violet was displayed in turn in a temperature range of 34.1? to 37.6?.(2)CLC microcapsules were prepared,and the mixture of COC and CPE in the ratio of 1:1 was used as the core material,melamine-formaldehyde was used as the wall material,XP was used as the emulsifier and NNO was used as the dispersing agent.In-situ polymerization method was used to fabricate CLC microcapsules.The experiment results showed that the optimal conditions of the preparation were as follows: emulsification speed of 6000 rpm,emulsifying time of 25 min,reaction p H of 4.0,core-wall ratio of 3:2 and reaction time of 2.5h.The dispersant NNO was added into the microcapsule solution,then it was stirred for 5 minutes and dispersed by ultrasonic wave,finally filtered and dried to obtain the microcapsule powder.(3)The prepared liquid crystal microcapsules were tested and analyzed by optical microscope,scanning electron microscope and laser particle size distribution instrument.The results showed that the CLC microcapsules were well prepared,they were spherical,the surface was smooth,the particle size distribution was uniform and the particle size was around 8~12?m.Through the test of color change property of the microcapsules,well color change property was found,and the color change temperature range was 34.4~38.0?.(4)Finally,the CLC microcapsules were treated on plain woven fabric of polyester-cotton by impregnation method and coating method respectively.The color change of the fabrics treated by two methods were compared.The fabric treated by the coating method showed color change obviously.In comparison,the fabric treated by impregnation method was not obvious.And gram per square meter of both fabrics were increased and permeability decreased.The results showed that the microencapsulation of cholesteric liquid crystal is feasible.The microcapsule showed color change obviously.It can be applied to prepare flexible materials such as thermochromic textile materials.In the future of textile consumer goods market,there will be more and more thermochromic liquid crystal products,thus enriching the public life.