| Recent years,the total energy consumption of buildings in our country is increasing rapidly due to the rapid increase in energy consumption for heating,ventilation and air conditioning.However,due to the poor thermal insulation performance of the building envelope construction,which has caused a serious waste of resources.Therefore,how to realize the recycling of energy under the condition of limited resources,while meeting the comfort of the living environment,achieve energy conservation and environmental protection has become a hot research topic in the field of building insulation.Phase change energy storage materials is also called phase change materials(PCMs).Because it can achieve the balance of energy supply and demand and solve the problem of energy supply and demand mismatch in time,place,and intensity,it is getting more and more attention.In order to solve the shortcomings of the phase change temperature of a single phase change energy storage materials,this paper is based on the Schroder formula,with capric acid(CA),lauric acid(LA),myristic acid(MA),palmitic acid(PA),and stearic acid(SA)as fatty acid raw materials,with tetradecyl alcohol(T A),cetyl alcohol(H),and stearyl alcohol(OA)as fatty alcohol raw materials,with 25#phase change wax(PCW25#)as the raw material of phase change wax.Through the melt blending method to prepare phase change eutectic material,with it as the phase change core material,with melamine modified phenolic resin(MPF),melamine urea formaldehyde resin(MPU),and silica as the wall material,respectively,to prepare composite phase change microcapsules.In order to better play the role of phase change materials in the field of building insulation,the phase change materials and building gypsum were combined effectively,it can not only realize the value of phase change materials in the field of building insulation,but also achieve the purpose of saving energy and protecting the environment.Based on the selection and preparation of phase change eutectic materials and microcapsules,with building gypsum as substrates,hydrogen peroxide as foaming agent,Calcium acid as foam stabilizer,manganese dioxide as catalyst,foamed gypsum is prepared by chemical foaming,and combined it with phase change material to prepare phase change energy storage foamed gypsum by direct addition and dipping,and conduct corresponding research on its various physical properties.The main research results of the thesis are as follows:(1)The addition sequence experiment of lauric acid-myristic acid-palmitic acid-stearic acid(LA-MA-PA-SA)quaternary phase change eutectic material verified that the addition sequence has no effect on the final phase change temperature and the melting latent heat.Basis on this,a series of phase change eutectic materials which meet the requirements of the building insulation field have been prepared and selected,such as capric acid-hexadecanol(CA-H),capric acid-Palmitic acid-stearic acid(LA-PA-SA),lauric acid-tetradecyl alcohol-cetyl alcohol-stearyl alcohol(LA-TA-H-OA),25#phase change wax-tetradecyl alcohol(PCW25#-TA),25#phase change wax-hexadecanol(PCW25#-H),25#phase change wax-octadecyl alcohol(PCW25#-OA),25#phase change wax-palmitic acid(PCW25#-PA).(2)Capric ac id-hexadecanol/phenolic resin(CA-H/MPF)and 25#phase change wax-tetradecanol/urea-formaldehyde resin(PCW25#-TA/MPU)microcapsule were prepared by in-situ polymerization,and their phase change temperature are 22.43℃ and 21.34℃;respectively,melting latent heat are 74.00 J/g and 63.12 J/g,respectively,both can meet the temperature requirements of the building insulation field,and the melting latent heat is relatively high,having good heat storage capacity.In addition,the core material and the wall material are only simple physical interlocking,which has no chemical reaction occur,Capric acid-cetyl alcohol/silica(CA-H/SiO2)microcapsules prepared by the sol-gel method is not suitable for using in the field of building insulation due to the inconsistent and heterogeneity of the phase change temperature.(3)The phase change energy storage foamed gypsum was prepared by the direct addition method,the results showed that the phase change energy storage foamed gypsum with compressive strength of 0.34～1.01MPa,apparent density of 362.89～487.37 kg/m3,thermal conductivity of 0.1047～0.1628 W/(m·k),softening coefficient of 0.23～0.97,water absorption of 0.57～1.47,phase change temperature of 22～31.36℃,and melting latent heat of 1.46～12.28 J/g,which can meet the building insulation requirements.The addition of phase change energy storage materials can change the structure of foamed gypsum,causing obvious pore collapse,uneven pores,and pore-to-pore connections,which lead to greater water absorption;There is only a simple physical interlocking between the phase change energy storage materials and the foamed gypsum,and no chemical reaction occurs,and it has good thermal stability.(4)When the phase change eutectic material and microcapsules are added into foamed gypsum in the same laboratory mix ratio,it is found that the structure of the foamed gypsum with microcapsules is very loose,and the gypsum crystals are mainly short columnar,some of that even become cube-shaped,and there are very few overlapping points between the crystals,resulting in a very low strength of the phase change energy storage foamed gypsum.When the water-binder ratio and cement content are reduced,the strength is significantly improved.(5)The phase change energy storage foamed gypsum was prepared by the dipping method.The results showed that the phase change energy storage foamed gypsum reached a saturated state when immersed in the phase change eutectic material for 90 min.At this time,its phase change temperature and melting latent heat are 23.12～30.93℃ and 24.49～60.06 J/g,respectively,which can meet the requirements of the building insulation field,and the melting latent heat is higher.The pores are filled by the phase change eutectic material,but its stability is very poor,which not only causes a serious waste of resources,but also pollutes other building materials to a certain extent,thereby affecting the service life of the building. |
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