Preparation And Properties Of Microencapsulated Phase Change Polyurethane Matrix Sandwich Composites

To saving energy and reduce consumption,new materials are developed towards lightweight,high performance and environmental protection.Sandwich composites are widely used in the fields of aviation,construction and civil foundation because of many advantages,such as high specific strength,stiffness,energy absorption,vibration reduction,sound insulation and heat insulation.In this study,the sandwich composites were composed by glass fiber reinforced polyurethane as the skin layer and polyurethane rigid foam(PUR)as the core layer.And ribs structure was used to connect different layers for enhancing the mechanical properties of PU sandwich composite.Based on this,silicon dioxide coated octadecane microcapsule phase change materials(MEPCMs)were further introduced to PUR and improve the temperature control performance of sandwich structure composites.Finally,the sandwich composites with the temperature control performance and high performance were successfully obtained.The main contents are as follows:1.The prepolymer method was used to prepare the polyurethane(GF/PU)composites,the GF/PU composites exhibit the highest performance comprehensive performance when the polymerization temperature of the polyurethane pre-polymer is 50?and the mass fraction of glass fibers is 55 wt%.The tensile strength,flexural strength,and impact toughness of GF/PU composites are 794 MPa,846 MPa and 228 kJ/m~2,respectively.The peak value of dynamic mechanical properties loss factor(tan?)is 0.59.Polyurethane rigid foam(PUR)was prepared by physical foaming agent n-pentane.When the dosage of foaming agent was 6 wt%,the performance was the best and the compression strength to weight ratio was 15.1.2.The PU sandwich composite were fabricated by integrated forming method,when the optimum technology of GF/PU composite and PUR acted as core layer,and the ribs was used to assist the connection to enhance the mechanical properties of PU sandwich composites.The sandwich composites exhibit the highest comprehensive performance when ribs structure was designed the circumference,transverse and longitudinal direction.The bending and shear resistance of the sandwich composites have been improved nearly three times than the ribless sandwich composites.This innovation structure of sandwich composites just take 6 mm deflection under the limit load of 5.9 kN.3.The MEPCMs were prepared by chemical precipitation method,based on octadecane core and silica shell.The effects of the ratio of octadecane to silicon and the amount of emulsifier on the enthalpy of phase transformation were studied,indicated that the products achieved the best performance with the mass ratio of core/shell and emulsifier were 1:2.5and 15 wt%,respectively.The MEPCMs presented the best properties with high melting enthalpy(105.4 J/g)and crystallization enthalpy(106.8 J/g),as well as appropriate melting point(31.9?)and crystallization point(23.1?).The initial decomposition temperature of the thermal stability of MEPCMs was increased by 30?than pure octadecane,and the total weight loss was achieved at 300?.4.Adding MEPCMs to the rigid polyurethane foams effectively increased the enthalpy of phase transition,but excessive addition sharply increased the viscosity of the foam prepolymer liquid.The samples presented a good comprehensive performance with high melting enthalpy(56.3 J/g)and crystallization enthalpy(53.1 J/g)when the MEPCMs mass ratio was 15 wt%.5.There are slight affects of sandwich composite on the mechanical properties when the MEPCMs of mass ratio was 50 wt%,and the ribs structure was designed the circumference,transverse and longitudinal direction.Sandwich composites have better temperature control efficiency in the process of temperature rise and drop,which can maintain the atmosphere temperature near 28?more than 1100 s and 1470 s,the thermal retardation capability of MEPCMs/sandwich composites increase three times than pure sandwich composites.It is successful to simulate the ability of temperature regulation of MEPCMs/sandwich for application.There are many excellent performance about this new type of PU sandwich composites,such as high strength to low weight ratio and thermal regulatory capability.