Study On Preparation And Thermal-Moisture Properties Of Form-Stable Phase Change Energy Storage Materials Based Sepiolite

As people pay more and more attention to thermal and humidity environment of buildings,the preparation of temperature-control and moisture-control materials has gradually been a hot issue in the research and application of composite building functional materials.In this paper,it prepared a double functional material of temperature-control and moisture-control based on sepiolite for high temperature and humidity areas.The eutectic systems of lauric acid-myristic acid and hexadecylic acid-tetradecanol were first prepared.Then,The sepiolite was modified by CTAB,sepiolite based composite phase transition materials with different mass fraction of lauric acid-myristic acid eutectic system were prepared by liquid phase intercalation.The thermal and moisture properties of lauric acid-myristic acid acid/sepiolite composite phase change materials were tested by cooling-step curve and "dryer-climate box" method respectively.The lauric acid-myristic acid composite phase change material was put in gypsum powder to make the phase-change energy storage gypsum board.It tested the thermal storage and the hygroscopic performance of gypsum test board.The following conclusions are obtained:(1)There was no undercooling in the lauric acid-myristic acid eutectic system,while there was slight supercooling in the hexadecylic acid-tetradecanol eutectic system.The mass ratio of the eutectic point of lauric acid – myristic acid composite phase change material is 63:37(lauric acid: myristic acid),its phase transition temperature is 32.71?,the phase change latent heat of 158.2J/g.The mass ratio of the eutectic point of hexadecylic acid-tetradecanol composite phase change materials is 18:82(hexadecylic acid: tetradecanol),its phase transition temperature is 32.35 ?,the phase change latent heat of 122.6 J/g.The FT-IR showed that no chemical reaction occurred in the eutectic materials of the two groups.At the same time,their thermal properties did not change significantly after 400 accelerated thermal cycles,and it has good thermal stability.(2)There is a "reciprocal" relationship between temperature control performance and humidity control performance of lauric aicd-myristic acid /sepiolite composite phase change material,with the increase of the proportion of lauric acid-myristic acid eutectic phase change material,the more significant the temperature control performance of the shape-stabilized phase change material,the more its moisture absorption capacity will also weaken.By normalization method of comprehensive evaluation on the performance of thermal and humidity,it found that when lauric acid-myristic acid eutectic phase change materials mixed with 30%,has the best thermal wet comprehensive performance,and its phase transition temperature is 32.63?,the phase change latent heat of 61.89J/g.Thermal cycling stability experiment and thermogravimetric experiments showed that sepiolite composite phase change material has a good thermal stability and will not have obvious leakage phenomenon,under 200 ? has good thermal stability.(3)With the addition of lauric-tetracylic acid/sepiolite composite phase change material,the storage and exothermic properties of the phase-change energy storage gypsum block can be improved,and the temperature response rate of the internal and external surfaces will also change.The ability of the gypsum test board to block heat transfer is related to the incoming heat on the surface.In addition,when shape-stabilized phase change materials are mixed into gypsum,their hygroscopic properties are superior to those of pure gypsum and shape-stabilized phase change materials based sepiolite.The reason is that there are more gaps between sepiolite and gypsum powder,which can be used as water molecules in air adsorption.Meanwhile,on the same relative humidity environment,the moisture excluding performance of the phasechange stored energy gypsum test is slightly less than the moisture absorption quantity,which verifies the reason that the hygroscopic capacity of sepiolite based composite phase-change material decreases and then becomes stable after multiple dehumidification cycles.