Preparation And Application Of Thermochromic Microcapsules

Thermochromic materials(TCMs)change colour within a specific temperature range,giving rise to their unique property of thermochromism.This feature has gained significant attention and admiration.The stability of TCMs is threatened by environmental stressors such as high temperatures,humidity,and organic solvents,leading to the loss of effectiveness and thermochromic sensitivity.These factors significantly constrain the potential applications and progress of TCMs.By using microencapsulation technology,however,TCMs become more stable and durable,and their potential applications expand significantly.This thesis focuses on utilizing microencapsulation technology to prepare thermochromic microcapsules by encapsulating organic reversible thermochromic materials.(1)A ternary complex was synthesized using bisphenol A(BPA),gallic acid,and boric acid as chromogens,crystal violet lactone(CVL)as a chromogenic inhibitor,and1-tetradecanol(TD)as a solvent.The color change time,the color stability time,and the color difference value(ΔE)before and after the color change of the ternary complex were analyzed by varying the type and ratio of chromogens.When bisphenol A was used as the chromogen in the ternary complex,the optimal color change performance was achieved with a color difference value of 80.The TD: BPA: CVL was found to be the optimal ratio of the ternary complex(100:4:1).The study also investigated the effects of CVL and BPA on the latent-heat performance and color-changing performance of the binary and ternary complexes.(2)Thermal responsive microcapsules were prepared by in-situ polymerization,using urea-formaldehyde resin as the shell material and a ternary complex as the core material.The optimal preparation conditions for the pre-polymer of optimal preparation conditions for the pre-polymer of urea-formaldehyde resin were determined through an orthogonal experiment at a molar ratio of urea and formaldehyde of 1:1.5,a p H range of7-9,a temperature of 70 ℃,and a time of 1 hour.Microcapsules with good encapsulation,dispersivity,and latent heat performance were obtained when the emulsifier was 5%arabic gum powder and the core-shell ratio was 1:1.The microcapsules possessed a clear core-shell structure,and no chemical reaction occurred between the core material and the shell material.The content of the core material was 72.2%,and the energy storage efficiency,melting enthalpy and crystallization enthalpy were 70%,135.68J/g,and132.96J/g,respectively.Thermal stability,corrosion resistance,and thermal cyclic durability of thermal responsive materials were significantly improved after microcapsulization.(3)Silica is utilized as the wall material.A ternary composite is employed as the core material to prepare a more environmentally friendly thermochromic microcapsule by the sol-gel method.The microcapsules prepared with an emulsifier dosage of 1.5 g and a core-to-shell ratio of 1:2 have a smaller particle size,higher encapsulation efficiency,the higher encapsulation efficiency.Characterization and analysis of the microcapsules prepared under the optimal preparation conditions indicate successful encapsulation of the core material.The microcapsules have a particle size of about 20 μm,a phase change enthalpy of 185.68 J/g and a crystallization enthalpy of 182.32 J/g,a core material content of 85%,and an energy storage efficiency of 83% is achieved.The silica microcapsules have high thermal conductivity and stability.After 200 cycles of thermal durability tests,the melt enthalpy and crystallization enthalpy are 175.12 J/g and 172.63 J/g,respectively,and the color difference value is reduced by 1,indicating good thermal durability of the microcapsules.(4)The thermochromic microcapsules are used to prepare a screen printing ink.When the microcapsule concentration in the ink is 20%,The adhesion level on copperplate paper is graded at level 4.The color difference value ΔE is 62.When the microcapsule concentration is 15%,the rubbing and washing fastness of the fabric is 4.The thermochromic microcapsule ink demonstrates good adhesion and color-changing ability.