Study On Paraffin/LDPE Phase Change Materials

With the growing shortage of energy,the reasonable development and utilization of energy has been more and more attention. By the thermal storage medium,phase change materials can regulate the temperature of environment. When the temperature is higher for ideal value,the medium will change state to drop temperature. And when its too low ,the medium also can recover it to the ideal value. Because phase change materials can ensure the stability of ambient temperature,also can save energy and protect environment,so it will be widely used.In this paper,pareffin was phase change material,low-density polyethylene(LDPE)was substrutesubstrete. They were melt blended to prepare phase change materials. The phase change temperature,latent heat,mechanical properties and thermal properties of phase change materials which had different pareffin content were studied. At the same time,we investigated the effects of the thermoplastic elastome(rSBS), dicumyl peroxide(DCP),inorganic filler and expanded graphite that on the permance of phase change materialThe DSC test indicated that the latent heat of pure paraffin used in this experement is 88.64J/g,the phase change temperature is around 62℃. The latent heat of material was higher as the paraffin content increased,and when the content was 70%,the latent heat was 56.59 J/g. But its mechanical properties dropped seriously. As the content of paraffin changed from 40% to 70%,its tensile strength dropped from 9.2 MPa to 5.6 MPa. The vicat softening point and hardness also dropped seriously. After several cycles of hot and cold,once the content was more than 60%,the weight loss of paraffin became more serious.Comprehensive consideration of the thermal properties and mechanical properties,the most apropriate paraffin content is 50%. Added in SBS,mechanical properties of phase change materials improved,and mechanical properties were the best when the content of SBS reached to 30%,then its tensile strength was 7.8 MPa,impact strength was 12.5 KJ/m~2,vicat softening point wsa 51.2℃. As SBS content changed,temperature became higher and hardness became worse.When added in inorganic filler such as diatomite and silica,its mechanical properties were slightly improved,and inorganic filler had a greater impact than silica. The phase change temperature became higher and the latent heat became lower. The hardness of the material rarely changed. Inorganic filler enhanced the adsorption capacity of paraffin,tthat was good for the stability.DCP was used to crosslink LDPE. The formation of network structure contributed to the paraffin coated and mechanical properties. Its tensile strength was 11.4 MPa and impact strength was 9.46 KJ/m~2 when the DCP content was 3%. Phase change temperature increased sightly,latent heat increased with the increasing of DCP content.After 10 cycles of hot and cold,it had the smallest wegiht loss content when the DCP content wsa 3%。It was found that appropriate expanded graphite substantially improved the thermal conductivity of phase change material. The mechanical properties slightly dropped as the addition of expanded grahite. When its content was 1.67%, tensile strength was 7.5 MPa, impact strength was 1.9 KJ/m~2 and hardness was 60HD. The phase change temperature became lower and the latent heat changed slightly. The change of vicat softening point was about 1℃,the expanded graphite had little ipmact on it.