Preparation And Properties Of Organic Reversible Thermochromic Microcapsules

Organic reversible thermochromic materials are smart materials whose colors can change reversibly with changes in the outside temperature within a certain temperature range.In recent years,they have been widely used in various fields.However,this type of material is easily affected by the environment and has poor stability.It is necessary to improve its chemical stability through microcapsule technology.In order to obtain organic reversible thermochromic microcapsules with excellent comprehensive performance,this thesis studies the preparation process of in-situ polymerization and interfacial polymerization microcapsules.In this thesis,the monostable thermochromic compound with 1-dodecanol as the solvent is used as the core material,and the urea-formaldehyde resin is used as the wall material.The multi-step method and the one-step p H adjustment process are compared and analyzed,and the in-situ polymerization is optimized.Method for preparing microcapsules.The microcapsules prepared by the multi-step p H adjustment process have an encapsulation efficiency of 72.2 %,core content of76.8 %,and a regular spherical shape.The main particle size distribution ranges from 1.5 to 3.9 ?m,and the average particle size is 2.60 ?m.The dispersibility in water is better.The process is applied to the coating of bistable thermochromic compound.The obtained microcapsules have the characteristics of bistable state.The decolorization temperature is 60 ?,and the color development temperature is0 ?.And the stability time of the light-colored state can reach more than 48 h.Using dodecanol as the core material and polyurea as the wall material,the preparation process of interfacial polymerization of dodecyl alcohol microcapsules was explored.The results show that using hexamethylene diisocyanate,1,3-propanediamine as the wall monomer,gum arabic as the emulsifier,the initial reaction temperature is 25 ?,the core wall mass ratio is 2.5:1,can be prepared dodecanol microcapsules.The average particle size of the microcapsules is 1.87 ?m,the encapsulation efficiency is 60.6 %,the core content is 79.8 %,the permeability in methanol is about 32 %,the phase transition temperature range is 21.5?24.5 ?,and the melting heat enthalpy is 142.3 J/g,can be used as phase change microcapsules in the field of heat storage and energy saving.Applying the above-mentioned interfacial polymerization process to the coating of thermochromic compound,mono-stable and bistable organic reversible thermochromic microcapsules can be obtained.The prepared microcapsules have low permeability and high dispersibility,can realize color changes in different temperature ranges,and have potential application value in military camouflage,anti-counterfeiting,and meeting the aesthetic needs of different people.