Preparation And Research Of Inorganic Nanoparticles Reinforced Polyurethane Composite

Polyurethane,as a kind of polymer material with exceptional comprehensive performance,has certain applications in different fields of life.Nevertheless,the mechanical properties and heat resistance of polyurethane are often not entirely satisfactory.And these two properties are often very limited by the type and content of soft and hard segments.Therefore,we hope to introduce some excellent fillers into the polyurethane,employing the meanings of compound modification to improve the mechanical properties and heat resistance.Compound modification can often reach simple,easy,efficient and quick enhancement of polymers.Therefore,this thesis carried out research on the preparation and analysis of montmorillonite/carbon nanotube/alumina/polyurethane composite material.In the third chapter of this article,montmorillonite is used as a filler,and several different montmorillonite/polyurethane composite materials are prepared by solution method and melt mixing method.Several montmorillonites with different modifiers were selected for experiments to explore the level of their interaction with the polyurethane matrix and the changes in the dispersion level,so as to select the type of montmorillonite that is more suitable for preparing composite materials.The montmorillonite dispersion level was characterized by X-ray diffraction(XRD)and transmission electron microscopy(TEM),and it was discovered that the composite material prepared by the solution method can be well dispersed under various mass fractions.The best enhancement effect on the mechanical properties showed when 1 wt%sodium-based montmorillonite was added in the composite material,and the tensile strength increased from 21.1 MPa to 24.3 MPa.The heat resistance is analyzed by thermal weight loss(TGA),to characterize the Initial temperature,and static thermomechanical analysis(TMA)to characterize the softening point temperature.It has found that the introduction of montmorillonite will increase the thermal decomposition starting temperature and the softening point temperature of the material to a certain extent,which shows that the addition of montmorillonite has a certain positive effect on improving the heat resistance of polyurethane composites.We also tested the flexural fatigue performance of polyurethane composites and found that when 1wt%sodium-based montmorillonite was added,the number of flexural fatigues increased by 32,000 times.It is attributed to the retardation of montmorillonite on crack propagation and the good dispersion level of composite materials prepared by solution method.Chapter 4 introduces a method to prepare carbon nanotubes/polyurethane composites by melt blending,with carbon nanotubes as fillers.An unmodified multi-walled carbon nanotube and a hydroxyl functionalized multi-walled carbon nanotube were selected for composite modification.Through the transmission electron microscope image,it is found that the carbon nanotubes will have a certain degree of aggregation at any mass fraction,and the degree of aggregation increases as the increasing of the mass fraction.But the mechanical properties have unexpectedly improved.At 0.25 wt%,the mechanical properties have been improved by 7.5 MPa.This may owe to the ultra-high modulus and ultra-large aspect ratio of carbon nanotubes.The addition of carbon nanotubes also raises the heat resistance of polyurethane partly.The flex fatigue performance has been greatly reduced,and it may give the credit to the rapid development of cracks caused by the accumulation of carbon nanotubes.In the fifth chapter of this article,alumina is used as the filler,and a framework material with a relatively complete heat conduction path is prepared by the foaming method.Initially,we expected to use the solution method to prepare polyurethane composites.The polyurethane solution infiltrated this framework material.However,due to the limited solubility of polyurethane in tetrahydrofuran,the solution always exists with a lower viscosity,which often leads to a lot of pores in the prepared composites and a relatively low level of the thermal conductivity.So,we chose liquid silica gel as the matrix,and injected the liquid silica gel into the gaps of the framework material by vacuum impregnation.Finally,when the alumina addition is 69.6 wt%,the thermal conductivity reaches 1.253 W/(m·K).