Preparation And Characterization Of Hexadecane/high Density Polyethylene Phase Change Composites Thermal Enhanced By Graphene

Phase change energy storage materials,which use the latent heat in the process of phase transformation to store or release energy,are often used as heat storage materials in the latent heat storage system,which has the advantages of large latent heat of phase change and constant temperature in the reaction process.However,most phase change materials have low thermal conductivity,low heat transfer efficiency,and are prone to leakage in the process of phase transition,so the development of a stable and high thermal conductivity phase change material has become a hot spot.In this paper,hexadecane was used as an organic phase change heat storage material.Cetane / HDPE composites with cetane mass fraction of 60 wt%,70 wt% and 80 wt% were prepared by melt blending,and graphene with high thermal conductivity was introduced to improve the thermal conductivity of cetane / HDPE composites.Graphene / hexadecane / high density polyethylene organic phase change energy storage materials with different graphene mass fraction were prepared by simple melt blending.The results show that:(1)The actual latent heat of 60 wt%,70wt% and 80wt% cetane / HDPE composites is 134.8J/g,160.7J/g and 165.2J / g,respectively.The actual latent heat obtained is smaller than the theoretical calculated value,because during the preparation process,part of the hexadecane will remain on the sample surface,and the actual latent heat of 80wt% cetane/ HDPE composites is 11% lower than the theoretical latent heat.The results show that the coating ability of high density polyethylene to hexadecane is limited,and the thermogravimetric results show that the mass loss of all cetane / high density polyethylene composites is less than 3% when the temperature is less than 100 °C.the results show that the prepared cetane / high density polyethylene has good stability in the working temperature range.(2)The addition of graphene has no effect on the melting and solidification temperature of phase change materials.However,the enthalpy of phase transition decreases with the increase of graphene content.When 0.5wt% is added,the latent heat of phase change is 147.5 J / g,and the enthalpy of phase transition is reduced by 5.6%.With the increase of graphene content,the latent heat of the composite is further reduced.When the amount of graphene is 1.0wt% and 1.5wt%,the melting enthalpy of phase change materials is reduced by 6.9% and 7.1% respectively compared with that without graphene.Therefore,graphene with high thermal conductivity is not added as much as possible.while improving composite energy storage materials,energy density should also be taken into account.(4)The results of the leakage rate show that when the graphene content is 0wt%,0.5wt%,1wt% and 1.5wt%,the final leakage rate is 2.21%,1.83%,1.72% and 1.46%,respectively,and the final leakage rate of all samples is less than 2.5%.The heat storage performance of hexadecane phase change materials encapsulated with high density polyethylene is stable in practical use.It can still exert excellent heat storage performance after repeated heating and solidification.(5)when the graphene content increases to 1.5%,the maximum thermal conductivity of graphene / hexadecane / HDPE composite is 0.67 W / m ·K,which is 314% of the original thermal conductivity compared with 0.214 W /m K of the composite phase change material without graphene,which speeds up the endothermic and exothermic rate of hexadecane composite phase change material.