Preparation And Characterization Of Three-dimensional Attapulgite And Its Composite Phase Change Materials

The inorganic porous matrix shaped-stabilized composite phase change materials can effectively solve the problem that the single phase change material is prone to leakage during usage,and this type of composite phase change materials has the advantages of good stability and simple preparation process,So it has been widely concerned.However,The effect of modified three-dimensional carrier on the thermal properties of composite phase change materials and the influence of the size of the carrier on the thermal properties of composite phase change materials are rarely reported.Therefore,in this paper,attapulgite with large specific surface area and rich pore structure is used as carrier,stearic acid is used as phase change material.Toluene diisocyanate and diphenylmethane-4,4 ?-diisocyanate were used to modify the attapulgite by using the active reaction of –NCO and Si-OH of attapulgite.A series of three-dimensional attapulgite with different pore size structures were acquired by introducing a series of polyamines or diols with different lengths of the segments into the system,and using the reaction of isocyanate groups grafted onto the surface of the attapulgite with amino groups or alcohol hydroxyl groups.The stearic acid/three-dimensional attapulgite-based composite phase change material was prepared by vacuum impregnation method.The structure of the three-dimensional attapulgite carrier and the structure and thermal properties of the stearic acid/three-dimensional attapulgite-based composite phase change materiasl were characterized and analyzed,and the effect of the pore size of the carrier on the thermal properties of the composite phase change material was discussed.Toluene diisocyanate containing a bis-NCO functional group was introuduced to modify attapulgite,and six series of diols having different segment lengths: hexanediol,polyethylene glycol 300,polyethylene glycol 600,Polyethylene glycol 2000,polyethylene glycol 4000,polyethylene glycol 6000 were added to react with attapulgite containing-NCO,which realized cross-linking of rods and rods in attapulgite structure.And six kinds of three-dimensional attapulgite carriers with different pore sizes were prepared and it was used to prepare a series of stearic acid/three-dimensional attapulgite-based composite phase change material.The three-dimensional attapulgite carrier has a higher adsorption capacity for stearic acid than the original attapulgite,and has good chemical structure stability and thermal stability.The phase change peak temperature and phase change enthalpy of the six composite phase change materials in the melting process also show a relationship with the pore size of the carrier,which increases with the increase of the average pore size.Their phase change temperature and phase change enthalpy were linearly fitted to the reciprocal of the pore size,and showed their relationship was correlated to the Gibbs-Thomson equation and the correlation coefficients were 0.96 and 0.98.The surface of the attapulgite was graft-modified with toluene diisocyanate containing-NCO functional group,and a series of polyamine having different segment lengths: Ethylenediamine,Hexamethylenediamine,N-N bis(3-aminopropyl)ethylenediamine,1,10-diaminodecane,tris(4-amino)phenylamine were introduced to reaction system.By controlling the reaction conditions,the construction of the three-dimensional attapulgite structure and the organic modification of the surface of the attapulgite are realized.The series of stearic acid/three-dimensional attapulgite-based composite phase change materials were significantly improved compared with the heat storage properties of stearic acid/ attapulgite-based composite phase change materials.Moreover,the stearic acid/three-dimensional attapulgite-based composite phase change materials has good structural stability and heat storage stability,and when stearic acid was limited to support materials with different pore sizes,the relationship between melting point and melting enthalpy with pore diameter was in accordance with Gibbs-Thomson equation.The grafting of ATP surface was carried out by using diphenylmethane-4,4 ?-diisocyanate,and introducing a series of diols having different segment lengths into the reaction system.The active reaction of-OH at both ends of the alcohol with-NCO grafted ATP was employed to realize the construction of the rod and the rod in the attapulgite support structure,and six kinds of three-dimensional attapulgite with different pore structure were acquired,and the attapulgite was completely realized the conversion from hydrophilic to partial lipophilicity.Six kinds of carriers were used to prepare stearic acid/three-dimensional attapulgite-based composite phase change materials and the modified three-dimensional attapulgite carrier adsorbed stearic acid significantly higher than the original attapulgite.In addition,the phase change temperature and latent heat value of the melting process increase with the increase of the pore size of the carrier,which is in accordance with the Gibbs-Thomson equation,and the correlation coefficients are 0.93 and 0.98,respectively.