Research On The Preparation And Properties Of PEG Composite Phase Change Materials

The domestic potential value in energy-saving and temperature regulation of the application of phase change material energy storage materials drove researchers’attention in-depth, phase transition theory and technology of the preparation of phase change materials has made considerable progress. Phase change materials were developed only in recent years, though there are many issues need to be studied. To conduct further research and application, we must prepare a number of appropriate materials which can be used to study.For the phase change materials there are two most important works, the first is select proper materials to meet our needs, and the second is how to fix them so that the materials can keep stability. Scientists have selected a series of phase change materials can be used in practical application.Our purpose is to study the fixing of working substance, after the preparation of phase change materials, many methods were used to characterize them, obtain data what we need. Although there is a long way to go from the practical application, they can provide some of ideas and basis.Sol-gel method was adopted to prepare the samples, polyethylene glycol was used as the working substance,Inorganic oxide networks were prepared by the hydrolysis of different kinds of metal alkoxides, these networks can manacle the molecular chains of PEG, We can achieve the purposes of prepare macroscopic solid-solid phase change materials. To prepare SiO2gel by the hydrolysis of TEOS, polyethylene glycol form gel in silica solution, the addition of thermal particles can increase the thermal conductivity of materials, normally, metal powder or graphite could be added, flake graphite was choose as the heat conduct inorganic particles in this experiment.The general sol-gel reaction need a still process to form gel, inorganic particles will sedimentation from the sol during this time, coagulation gel process could be promote in alkaline condition, in this experiment, ammonia was used to provide the alkaline condition to accelerate coagulation gel process, and the addition amount was explored, obtain good result,IR, SEM, DSC, TG, XRD were used in samples’characterization and selection. The final selected samples have the following mass ratio, PEG:silicon dioxide:graphite=7:3:1, experimental results show that the material obtained good surface morphology, good compatibility. Phase transition temperature of phase change composite material was lower than that of pure polyethylene glycol, the phase transition enthalpy has a range of smaller, and larger molecular weight by greater the impact, but are within the acceptable range. Thermal stability of phase change materials with graphite were better good, when temperature is340℃, weight loss reached5%. The materials can meet the requirements of application.By hydrolysis reaction of tetrabutyl titanate, titanium dioxide/polyethylene glycol gel was formed with different molecular weight polyethylene glycol in solution, titanium dioxide/poly (ethylene glycol) composite phase change material was prepared after the gel was dried. Infrared spectroscopy was adopt to characteristic the structure of the sample prepared, the results showed that the PEG did not reacted, polyethylene glycol and titanium dioxide were combined by Van Der Waals Forces. SEM was used to observe the surface of the composite phase change materials, the photos showed that the samples have good surface morphology and good compatibility which can be reflected from the photos. DSC was adopted to measure the transition temperature and latent heat of the materials, the results show that the expected goal had been achieved. TG was adopt to measure the thermal stability of the materials, the results show that the samples could hold in a stable state below200℃, it would meet the need of practical application. XRD was used to characterize the crystallization properties of the materials, there has large differences between pure PEG and the samples prepared, crystalline integrity was declined, as we know, it’s hard to avoid, in order to keep the stability of the phase change materials, part of latent heat must be wasted.