Aliphatic Chain Modified Melamine Foam And Study On Its Phase Change Energy Storage Materials

As an ultra-light porous foam material,melamine foam,which has the pr operties of ultra-low density,high specific surface area,thermal insulation,fla me retardant,sound absorption and noise reduction,plays an important role i n the field of construction,transportation and cleaning industries.Although th e melamine foam itself has very excellent properties,by functionally modifyin g,it can play a more important role in more fields.As a carrier for storing ther mal energy,phase change materials can play an important role in the fields of solar energy utilization,microelectronic chip cooling,building energy conserv ation,and power system peak-to-valley balance.However,although a single s olid-liquid organic phase change medium has high energy density,it has poor t hermal conductivity and is prone to leakage during phase transformation.It ne eds to be combined with the support material to prepare a shape-stable phase c hange material with good thermal conductivity.In our work,ultra-light melam ine foam is used as the support material,and tetradecylamine is the phase trans ition medium.The thermal conductivity of the melamine foam matrix was imp roved by the addition of muli-walled carbon nanotubes(MWCNTs)and the int eraction between the tetradecylamine and melamine foam was enhanced by fu nctional modification of the surface of the melamine foam skeleton,by which a novel shape-stable phase change material with good thermal conductivity was prepared.The main research results are as follows:(1)Preparation of carbon nanotube modified melamine foam-based pre-e mbedded functional skeleton and its effect on phase transition behavior of tetr adecylamine.Firstly,polyacrylic acid was synthesized and azide-modified to p repare azide polyacrylic acid.Under high temperature conditions,the azide gr oup of the azidated polyacrylic acid was decomposed and the resulting nitrone structure was added in the surface of MWCNTs by covalently grafting and si multaneously introducing a carboxyl group on the surface of the MWCNTs,w hich reacted with the amine groups on the surface of the melamine to obtain m elamine-modified MWCNTs,of which the surface structure is characterized b y infrared spectroscopy,EDS spectra and Raman analysis.Then,during the p(?)eparation of the melamine foam,melamine-modified MWCNTs were added a nd take part in the polymerization process of monomer in the form of in-situ p olymerization,which can make the MWCNTs better dispersed in the melamin e foam matrix.The dispersibility of MWCNTs in the foam matrix was analyze d by scanning electron microscopy.The influence of the amount of carbon na(?)otubes on the thermal conductivity of melamine foam was analyzed by therma 1 conductivity meter.Finally,melamine-modified MWCNTs modified melami ne foam was used as the pre-embedded functional skeleton,and its effect on th e phase transition behavior of tetradecylamine was studied.The effect of pre-e mbedded functional skeleton on the thermal conductivity of the tetradecylamin e phase transition was studied by thermocouple.The effect of pre-embeddedunctional skeleton on the transition behavior of tetradecylamine phase was stu died by DSC.The results show that the modification of melamine enables the carbon nanotubes to be better dispersed in the melamine foam matrix,and the thermal conductivity of the melamine foam is better improved.The thermal cc nductivity is increased by 48.37%when the amount of melamine-modified M WCNTs is 8%.As the amount of melamine-modified MWCNTs increases,the thermal conductivity of the tetradecylamine containing pre-embedded functic nal skeleton is better,and the degree of supercooling is smaller.(2)Preparation of surface modified pre-embedded functional skeleton a(?)d shape-stable phase change material.First,polyacrylic acid chlorides of differ ent molecular weights are synthesized,and then the acid chloride groups reac ed with the amine groups on the surface of the foam skeleton,grafted onto the surface of the pre-embedded skeleton,with which the tetradecylamine reacted and grafted onto the surface of the skeleton to obtain a tetra-ammonium-modii ied pre-embedded functional skeleton.Finally,the molten tetramethylamine wa s infiltrated therein to prepare shape-stable phase change materials.The molec ular weight of polyacryloyl chloride was analyzed by gel permeation chromate graphy.The surface of the melamine foam was characterized by infrared spect rum,EDS spectrum,scanning electron microscopy and thermogravimetric ana lysis.The properities of shape-stable phase change material were analyzed usi ng digital cameras,thermocouples,DSC,and scanning electron microscopy.T he results showed that tetradecylamine was successfully introduced into the su rface of pre-embedded framework by means of covalently grafting.The grafti ng amount of tetradecylamine increased with the increase of molecular weight of polyacryloyl chloride.Under the premise of no leakage,the melting and ent halpy of the composite phase change material can reach up to 183.7J/g and 201.58J/g,respectively.At the same time,the prepared shape-stable phase chang e materials exhibit good cycle stability.As the molecular weight of polyacrylo yl chloride on the surface of the pre-embedded functional matrix increases,the thermal conductivity of the composite phase change material decreases gradu ally and the degree of supercooling gradually increases.