Synthesis And Study Of A Novel Phase Change Material With Heat Storage-CDA-g-MPEG/PEG

Latent heat energy storage is one of the most efficient ways of storing thermal energy. Latent heat storage system based on phase change materials'(PCMs)melting and freezing is particularly suitable for solar energy heating,peak-shift of electrical demand and heat recovery.Phase change materials investigation is the first step of developing a latent heat storage system and thus is always the focus in related research.The research and development of functional fiber is to satisfy special demands.Phase change fiber with heat storage is one of the important aspects.Phase change fiber can be applied in the areas of military and living affairs.This dissertation is composed of four parts.First,synthesis of reactive intermediate compound IPDI-MPEG and TDI-MPEG that having a reactive isocyanate group(-NCO) in the end of the chain through methoxy polyethylene glycol(MPEG)and isophorone diisocyanate(IPDI)or toluene diisocyanate(TDI)and the kinetics study of IPDI and MPEG;second,synthesis of comblike grafted solid-solid phase change copolymers through the reaction of IPDI-MPEG or TDI-MPEG with cellulose diacetate(CDA);third, study on the thermal properties of three type of blended systems:blended system of different kinds of pure copolymer,blended system of polyethylene glycol(PEG)and raw copolymer without distilling derived MPEG,blended system of PEG and pure copolymer; fourth,study on the solution properties of copolymer/acetone systems and the figuration of phase change fibers.In the first part,four kinds of compound were synthesized with reactive group -NCO in the end of the chain:IPDI-MPEG2000,IPDI-MPEG5000,TDI-MPEG2000 and TDI-MPEG5000 through the reactions of IPDI and TDI with MPEG2000(the average Mw of MPEG is 2000)and MPEG5000(the average Mw of MPEG is 5000),respectively.The molecular structure was confirmed qualitatively using IR and gel permeation chromatography(GPC),the reaction kinetics of IPDI and MPEG was studied by dibutylamine back titration.Two main resultant products were obtained in the reaction of IPDI and MPEG:monourethane IPDI-MPEG(objective product)and diurethane IPDI-(MPEG)₂(assistant product).It was found that the reaction of IPDI and MPEG is a second-order reaction,in order to obtain more objective products IPDI-MPEG;the reaction condition should be:r=1.1(r is[NCO]₀:[OH]₀,the ratio of the initial concentration of the functional groups),reaction temperature=40℃,without any catalyst,reaction time=120-180min.Assistant product IPDI-(MPEG)₂ increased while changing r value, increasing reaction temperature,using dibutyltin dilaurate(DBTDL)as catalyst or increasing reaction time.In the second part,CDA-IPDI-MPEG2000,CDA-IPDI-MPEG5000, CDA-TDI-MPEG2000 and CDA-TDI-MPEG5000 were synthesized by the reaction of CDA and MPEG with reactive -NCO in the end of chain at following reaction condition: reaction temperature=56℃,reaction time=4h,using DBTDL as catalyst.The molecular structure was confirmed by IR,GPC and H¹-NMR,phase change properties were studied by differential scanning calorimetry(DSC),the phase change characteristic and surface morphology of polymer film were observed by normal optic microscope and scanning electron microscopy(SEM),crystal morphology was observed by X-ray diffraction(XRD) and polarizing optical microscopy(POM),thermal stability was studied by thermal gravimetric analysis(TGA).The results of above analysis suggested that MPEG had successfully grafted onto CDA backbone through the reaction of end group -NCO of IPDI-MPEG or TDI-MPEG and -OH of CDA chain to obtain a grafted polymer,the obtained grafted polymers exhibit phase change properties at certain range of temperature, in this chapter,a new method was investigated that using aliphatic diisocyanate IPDI as crosslinker in the reaction of MPEG grafting CDA to prepare a comblike grafted phase change polymer.In the third part,the phase change properties of blended systems were studied by DSC method,and the crystal morphology of different kinds of pure copolymer blended systems were observed by POM,it was found that,a solid-solid washable phase change materials were obtained by blending different kinds of pure copolymer,the phase change enthalpy of the blends is 7.18-27.18 J·g^-1,the phase change temperature is 18.82-52.75℃,and the value of phase change enthalpy and temperature could be adjusted by changing the blending polymer proportion,the crystal morphology in these blended system is not perfect spherulites but crystallites.A new blending method was invented to prepare solid-solid phase change materials through PEG blending pure grafted polymer CDA-g-MPEG or blending raw grafted polymer CDA-g-MPEG/MPEG,the grafted MPEG in CDA-g-MPEG or CDA-g-MPEG/MPEG affected on blended PEG;so,controlling the molecular weight and blended proportion of PEG;the novel phase change materials that blending PEG can be used in no water washing condition and occur solid to solid phase change characteristic during their phase change process,besides the blending of PEG can increase phase change enthalpy and adjust phase change temperature range of the PEG blending systems.It was found that the largest value of phase change enthalpy of solid-solid phase change material of PEG blending CDA-g-MPEG and PEG blending CDA-g-MPEG/MPEG is 90.51 J·g^-1 and 89.06 J·g^-1.In the fourth part,the acetone solution properties of various systems were researched, and the results suggested that MPEG in CDA-g-MPEG/MPEG acetone solution is easier to separate out than in CDA-IPDI-MPEG acetone solution,and MPEG5000 is easier to separate out than MPEG2000.The rheology study of CDA/acetone, CDA-IPDI-MPEG5000/acetone and CDA-IPDI-MPEG5000/MPEG5000/acetone indicated that all of them belong to non-Newton fluid and characterized by shear thinning.For the first time, the phase change fibers were prepared in laboratory through electro spinning of CDA-IPDI-MPEG5000/acetone solution and CDA-IPDI-MPEG5000/MPEG5000/acetone solution.The study of electro spinning fibers and dry spinning fibers of CDA, CDA-IPDI-MPEG5000 and CDA-IPDI-MPEG5000/MPEG5000 indicated that the electro spinning fibers of CDA-IPDI-MPEG5000/MPEG5000 have the smallest fiber diameter among the three electro spinning fibers,and its average diameter is less than 100nm,the electro spinning fibers of CDA-IPDI-MPEG5000/MPEG5000 represent lager phase change enthalpy and lower phase change temperature than its dry spinning fibers, CDA-IPDI-MPEG5000/MPEG5000 acetone solution can hardly spin into fibers by dry spinning due to its bad spinnability,the dry spinning fibers of CDA-IPDI-MPEG5000 exhibit smaller tensile strength and larger elongation at break than CDA dry spinning fibers.