Preparation And Properties Of Polyethylene Glycol N-hexadecyl Ether Grafted Graphene Oxide Phase Change Material

Polyethylene glycol hexadecyl ether(EnC16)is commonly used as a nonionic surfactant,but our research group takes the lead in its use as a phase change material(PCM),which has some features such as high thermal storage density,isothermal operation characteristic and excellent thermal stability temperature.However,it is also a typical solid-liquid phase change material(SLPCM),which is easy to leak in the process of phase transition.Graphene oxide(GO)is a two-dimensional layered carbon material.Because of its excellent physical and chemical properties,GO has been widely studied and applied in various fields.The experiment is mainly divided into three parts.In the first part,diethylene glycol hexadecyl ether-grafted graphene oxide solid-solid phase change material(E2C16-g-GO SSPCM)was fabricated by an esterification reaction under the N,N-dicyclohexylcarbodiimide/4-dimethylaminopyridine(DCC/DMAP)catalyst system with diethylene glycol hexadecyl ether as functional material.The effects of different mass ratios(E2C16:GO=2:1-7:1 mass%)and different reaction times(3 h,6 h,9 h,12 h,15 h)on the thermal properties of the products were studied,and the optimal reaction parameters and the best product were determined.The second part is to select EnC16 with various number of repeat units(n=2,10,20)as a functional material,which were grated onto GO via an esterification reaction to fabricate polyethylene glycol hexadecyl ether-grafted graphene oxide(EnC16-g-GO).The effects of the various number of repeat units on the structure and properties of the products were investigated in detail.In the third part,E2C16/GO composite phase change materials(FPCMs)were fabricated successfully by an esterification reaction with E2C16 as a thermal storage material and GO as the supporting substance.In FPCMs,there are both E2C16-g-GO SSPCMs and E2C16 SLPCMs.Among,the E2C16-g-GO SSPCMs is not only a supporting material,but also as a working substance.The effects of different GO dosages(0%,0,5%,1%,1.5%,2%,4%,6%)on the crystallization and phase transformation properties of FPCMs were investigated,and the synergistic transformation effect between E2C16-g-GO and E2C16 was also studied.Fourier transform infrared spectra(FTIR),Raman spectroscopy(Raman),X-ray diffraction(XRD),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA)and other testing instruments and characterization methods were used to characterize their structure and properties.The results show that when the mass ratio of E2C16 and GO is 6:1,and the reaction time is 6 h,we have fabricated E2C]6-g-GO SSPCM with the best thermal performance,which has the appropriate phase transition temperature and higher phase transformation enthalpy.The melting and crystallization temperature are 43.3 ? and 29.4 ?,respectively.The enthalpy of melting and crystallization are 70 J/g and 72 J/g,respectively.In addition,E2C16-g-GO not only has good thermal stability and shape stability,but also has excellent thermal reliability and structural stability,which has a positive significance for long-term thermal storage applications.However,EnC16-g-GO phase change materials(GEn)were fabricated by covalent grafting EnC16 with various number of repeat units onto GO nanosheets,which were affected by repeating unit number(n)of EnC16.When n=2,the crystallization of the GE2 is dominated by the crystallization of alkyl side chains,showing higher phase transition enthalpy and better thermal stability;When n>10,the crystallization of the GEn is gradually dominated by the crystallization of ethylene glycol chains,and two kinds of crystalline segments are crystalline competition,so the thermal phase properties are also significantly reduced.In E2C16/GO composite phase change materials(FPCMs)fabricated by GO as support material and E2C16 as functional material,there are not only E2C16-g-GO SSPCMs prepared by esterification reaction,but also E2C16 SLPCMs adsorbed on GO surface.Among them,E2C16-g-GO SSPCMs are used as supporting material and functional material.The fabricated FPCMs had high enthalpy,and the synergistic phase transformation between E2C16-g-GO and E2C16 achieved high latent heat efficiency of FPCMs,which have higher heat storage ability than traditional shape-stabilized PCMs.In addition,FPCMs show good thermal stability and reliability.