Preparation And Performance Of Composite Phase Change Materials

With the development of the society and economy, the demands for the energy are higher and higher.At the same time, the non-renewable resources are being exhausted gradually. Therefore, the utilization ofnew energy and waste energy is receiving increasing attention in the research community worldwide, thepreparation and performance of composite phase change materials has become a lot spot in the region onthermal storage materials.The composite PCMs can effectively solved the leakage of PCMs when happened phase changing. Butcomposite PCMs can lead to the lower ability of heat and after many thermal ctcles is not stable.Choosinggood performance substrate materials can effectively solved and improved these defects.In this study, halloysite nanotubes (HNTs) were firstly introduced which is rich in china as supportmaterials for preparing form-stable composite PCMs. More importantly, the active sites on outer surfaceand inner surface of HNTs can strongly adsorb polarity compounds, such as fatty acid, ethyl amide anddimethyl sulfoxide.The composite PCMs prepared by different methods. first of all, we were firstly introduced HNTswhich is rich in china as support materials for preparing form-stable composite PCMs, stearicacid/halloysite nanoyubes intercalated phase change compounds were prepared by replacing method ofdimethyl sulphoxide (DMSO). secondly, this research took three organic phase change materials whichwere polyethylene glycol, CA-SA eutectic mixtures, modified kieselguhr and halloysite nanotubes assupporting materials, ethanol as solvention, three kinds of composite PCMs, polyethylene glycol/halloysitenanotubes composite PCMs, CA-SA/HNTs composite PCMs, PEG/HNTs composite PCMs were preparedby solution intercalated reaction. Phase change temperature and latent heat of the composite PCMs and thethermal stability of the composite PCMs were characterized by synthesized thermal analyzed (TG-DSC),the composite PCMs were characterized by scanning electron microscope (SEM), Fourier transformationinfrared spectroscope (FTIR) and synthesized thermal analyzer, respectively.The results of the research as follows:(1) The basal spacing of halloysite nanotubes increase from0.74nm to3.92nm, and the apparent intercalation of product is95.4%. Hydrogen bonds are formed between the carbonyl group in stearic acidand the hydroxyl group in inner surface of halloysite, hydrogen bonds can also be formed between thehydroxyl group in stearic acid and the oxygen atom of silicon and the oxygen layer in halloysite, phasechange temperature of composite PCMs is50.3oC, phase change latent heat is103.9J/g, the compositePCMs show favourable compatibility, thermal stability and chemical stability after500thermal cycles.（2）Polyethylene glycol/halloysite nanotubes composite phase PCMs for thermal storage made ofpolyethylene glycol impregnated in halloysite nanotubes was prepared by anhydrous alcohol carryingmethod. Morphology features, adsorption effects, composite mechanism and thermal properties of thecomposite PCMs were studied by scanning electron microscope (SEM), Fourier transformation infaredspectroscope (FT-IR) and synthesized thermal analyzer. The results show that the optimum content ofpolyethylene glycol in composite PCMs is65%with58.7oC as the phase change temperature and105.6J/gas latent heat. The composite PCMs show favourable compatibility, thermal stability and chemical stabilityafter500thermal cycles.(3) The novel form-stable composite PCMs were prepared by impregnation of CA-SA eutecticmixtures into the HNTs. CA-SA eutectic mixtures can be strongly absorbed on the active surface of HNTsbecause hydrogen bodings are formed between the hydroxyl groups in CA-SA eutectic mixtures andoxygen atom of silicon and the oxygen layer in HNTs. Besides, with the effect of capillary force andactivity of inner surface of HNTs, CA-SA eutectic mixtures are anchored in the tube of HNTs and hydrogenbodings are formed between the carbonyl groups in CA-SA eutectic mixtures and the hydroxyl groups ininner surface of HNTs.60wt%CA-SA eutectic mixtures are the best mass percentage in the HNTs, whichshows high thermal reliability and good chemical stability even after500thermal cycling with the phasechange temperature as27.9oC and with the latent heat of92.6J/g. The prepared form-stable compositePCMs are promising heat storage materials in wider application for their good energy properties, easypreparation and unnecessary encapsulation so as to reduce the cost of energy storage system.(4) The novel form-stable composite PCMs were prepared by impregnation of PEG within the HNTsand characterized by using FT-IR, SEM and TG-DSC analysis techniques. Because of the excellentcharacteristics of HNTs such as large surface area, large pore volume and adequate hydroxyl groups, PEGcan be immobilized in mass fraction of65%in HNTs without any liquid phase package from composite PCMs. DSC results showed that the phase change temperature and latent heat of composite PCMs were27.8oC and85.25J/g, respectively, they are suitable for low temperature thermal energy storage application.TG results showed that the weight loss between300oC to450oC can be attributed to thermaldecomposition of the PEG adsorbed in HNTs, which is in good agreement with the ratio of65%. There isno chemical reaction between PEG and HNTs but physic and chemical interaction through FT-IR analysis.Farther more, the TG-DSC and FT-IR analysis confirmed that the composite PCMs had good thermalreliability and chemical stability after500thermal cycling.In this study, halloysite nanotubes (HNTs) were firstly introduced which is rich in china as supportmaterials for preparing form-stable composite PCMs, stearic acid/halloysite nanotubes intercalated phasechange compounds were prepared by replacing method of dimethyl sulphoxide (DMSO), the compositePCMs show favourable compatibility, thermal stability and chemical stability after500thermal cycles. Thispaper deals with the preparation, characterization and determination of thermal energy storage properties ofpolyethylene glycol/halloysite nanotubes, CA-SA/HNTs, PEG/HNTs as a novel form-stabled compositephase change materials. Composite PCMs with different mass ratios were prepared by adsorbing liquidPCMs into the HNTs. The composite PCMs show favorable compatibility, thermal reliability and chemicalstability even after500thermal cycles.