Preparation And Characterization Of Form-stable Phase Change Materials Of LA/LDPE

Form-stable phase change is a solid-solid phase change material, which is made of a polymer material as a support, using the melting point difference between PCM and polymer to make of a composite material. Recently, a lot of works had been carried on paraffin-based PCM by many researchers, but the phase change paraffin has many drawbacks, such as:non-renewable, poor thermal conductivity, non-environmentally friendly, and poorer low temperature performance characteristics paraffin. Therefore, finding a renewable and better thermal performance PCM is very necessary.Lauric acid is a renewable phase change material, have wide range of sources. Not only can lauric acid be artificially synthesized by chemical methods, it is also available in the coconut palm, palm and other plants. In addition, lauric acid has good compatibility, moderate phase transition temperature, relatively good thermal characteristics. Expanded graphite is an inorganic material with excellent thermal conductivity, whose axial thermal conductivity is 100 times than paraffin. Furthermore, expanded graphite has high porosity. Surface area and good absorption for liquid material.To solve the renewable and thermal problem of stable phase change materials, this paper prepared lauric acid/low-density polyethylene (LA/LDPE) form-stable phase change material by high temperature melt blending, and then introduced the third component to develop the thermal properties of the materials. Through a systematic study of this thesis preparation, modification and characterization of form phase change materials, following conclusions were obtained:(1) The best raw material ratio of LA and LDPE is 1:1. If LA and LDPE ratio are greater than 1:1, the weight-loss ratio of phase change material are more than 10% after a high and low temperature cycle. On the contrary, if LA:LDPE is lower than 1:1, the capability of energy storage will reduce, and making a waste of LDPE;(2) Through the SEM observation, we can see that LA was wrapped tightly in the three-dimensional network structure of LDPE, forming a complete continuous phase. Therefore, even after the phase change, the liquid LA cannot escape form the network structure of LDPE, without happening of materials leakage.(3) When LA:LDPE is 1:1, the shape of the latent heat of phase change materials is 82.21 J/g, its initial phase transition temperature is 41.84℃. The LA/LDPE phase change latent heat of modified phase change materials has no obvious change, but the phase transition temperature has a slight decline;(4) The LA/LDPE form-stable phase change material were produced through adding the expanded graphite. Owing to the excellent thermal conductivity of expanded graphite, introduction of a small amount of expanded graphite can greatly improve the thermal conductivity of the material;(5) The SEM observation of modified LA/LDPE shows that the expanded graphite are distributed evenly in the continuous phase of phase change materials, forming the heat exchange network, which can not only help finalize the design phase change materials and improve the thermal conductivity, but also can equalize the temperature, preventing materials from local overheating problem...