Preparation And Properties Of Straw Shaped Phase Change Wall Plate

Building energy consumption and environmental problems caused by dry burning of straw are the focus of social attention and research,and also the social problems to be solved urgently.Buildings energy consumption use 30 to 40 percent of the world’s energy,and the construction industry is responsible for 35 percent of global greenhouse gas emissions.Rice farming produces a large amount of rice stalks each year,with the annual global crop estimated at 7409 to 1111.14 million tons.However,only a small part of rice stalks is used effectively,and a large amount of rice stalks are discarded in fields or burned directly,which not only causes a huge waste of biomass resources,but also causes serious pollution.In this study,under the above background,using the good thermal insulation building materials characteristics of straw,the high performance straw shaped phase change board was prepared,which has good thermal insulation performance.The prepared board has excellent physical and chemical properties such as environmental protection and energy saving,good anti-corrosion performance,excellent thermal insulation performance and so on.The use of paraffin wax as phase-change material significantly improves the thermal insulation performance of straw board,which makes the straw board become a potential energy-saving building thermal insulation material.On the other hand,the successful development of high content straw board greatly improves the utilization rate of straw,solves the problem of straw utilization.Through the microscopic characterization of the material and thermodynamics and other physical and chemical properties of the test,the following results are obtained:(1)Rice straw-calcium sulphoraluminate cement composite thermal-insulation building materials were prepared by using rice straw as aggregate and calcium sulphoraluminate cement as cementation material.The effects of length of rice straw(L),mass ratio of rice straw to calcium sulphoaluminate cement(Wr/W)and forming method on the morphology,mechanical properties,thermal properties,water absorption and moisture absorption of the composite thermal insulation building materials were studied.The results show that compared with the casting molding,the material structure obtained by compression molding is more compact,has higher mechanical strength,lower water absorption and moisture absorption,and has lower thermal conductivity.With L = 1.0 cm,Wr/W = 12%,the composite prepared by compression molding has a thermal conductivity of 0.071 W/(m·K),a compressive strength of 21.0 MPa,a flexural strength of 13.5 MPa,a water absorption rate of11.0%,and a moisture absorption rate of 10.0%.(2)A form-stable phase change material(PCM)based on paraffin has been prepared using rice straw as the supporting material.Paraffin miniemulsion is first prepared by ultrasonication.Then,paraffin is loaded on rice straw by spraying the miniemulsion on rice straw followed by a vacuum impregnation process.Finally,the paraffin particles loaded on rice straw are coated by a polyvinyl alcohol(PVA)film.Scanning electron microscopy demonstrates the successful loading of paraffin on rice straw and PVA coating on paraffin particles.Differential scanning calorimetry reveals that the prepared material has a high phase change enthalpy of ～133.4 J/g.The leakage test sho Wr that the material has good cycling stability.After 100 times of consecutive melting-freezing cycles,only about 1.6% of paraffin lost.(3)In(1),(2)on the basis of preparation of high performance to finalize the design phase transition board,through the study of encapsulated paraffin amount(Wp)and the quality of rice straw and calcium sulphoaluminate cement ratio(Wr /W),to the expansion of the composite material and decay properties,mechanical properties,thermal properties,and the influence of suction hygroscopicity,paraffin wax will lower plate mechanical properties,but the sheet can significantly improve the waterproof performance,thermal performance,anti-corrosion performance.The optimal mixture ratio is Wp:Wr = 2:1、Wr/W =70%,the thermal conductivity of the composite prepared by die-casting is 0.054W(m/K),the static bending strength is6.7MPa,the water absorption rate is 7.0%,the moisture absorption rate is 5.5%,and the composite has good water absorption,expansion and decay resistance and heat insulation performance.