The Preparation And Properties Of Covalent Polyurethane/Nanoparticle Hybrid Elastomers

The combination of nano chemistry and traditional polyurethane chemistry is an important method to modify the structure and properties of polyurethane elastomers.There are some common nano-modified polyurethane elastomers materials,such as graphene,carbon nanotubes,clay and biomass nano-materials,etc.And the effect of particles modification has been achieved a better stage.However,in polyurethane modification chemistry,the difficult scientific problem in high stripping and dispersion is not well solved due to the self-agglomeration of nanoparticles,which weakens the composite modification effect of nanoparticles on polyurethane.In this paper,the functionalized inorganic nano carbon material and the biomass particles with sp~2 hybrid structure and electron delocalization effect which can directly participate in the polyurethane chemical reaction are used as the nano-reinforced modified materials.The dispersion of nanoparticles in the polyurethane elastomer matrix is improved and the high-performance polyurethane composites with heat conductivity are prepared.This thesis includes the following three parts.Firstly,the effects of preparation conditions on isocyanate modified GO and the effects of modified GO on the properties of polyurethane were studied.Diisocyanate was used to organic modify GO.The effects of reaction time between isocyanate and GO on the modified effects of GO and the modified GO effects on the properties of composites were investigated.The experimental results showed that the surface oxygen-containing functional group was replaced by-NCO and the structure defects of GO increased.So the organic modification was successful.When the experimental conditions in this paper were 12 h,the modification effect was the best.The tensile strength,T_g,the heat conductivity,and the heat capacity of the polyurethane nanocomposite with best GO content increased by 250%,3?,110%,60%respectively.Also the initial decomposition temperature of T_g increased.It has been proved that isocyanate modified GO could improve the mechanical properties and thermal stability of polyurethane composites.The existence of sp~2 hybrid structure of carbon atom was more conducive to heat conduction,which resulted the thermal conductivity of composite material increased by 100%.Secondly,the structure and properties of composite polyurethane elastomer prepared by isocyanate modified multiwall carbon nanotubes(MWCNTS)were studied.The carbon nanotubes was modified with isocyanate and reacted with polyol.The compatibility between carbon nanotubes and polyurethane matrix was improved through the entanglement between NCO@MWCNTs and molecular main chain of polyurethane elastomers.A series of different content of MWCNTs/polyurethane elastomer nanocomposite were prepared,and the microstructure of material,physical properties and thermodynamic properties were studied.And the influence of the amount of carbon nanotubes on polyurethane composites was investigated in depth.The experimental results showed that the structure of NCO@MWCNTs was still in whole,the length of NCO@MWCNTs was not shortened and the dispersion of NCO@MWCNTs was significantly improved compared with before.Moreover,MWCNTs in the matrix were combined with the matrix with good dispersion and formed better interfacial adhesion.With the increase of MWCNTs content,the modification effect showed a trend of increasing at first and then decreasing.When 0.3%wt MWCNTs was added,the modification effect was the best.The tensile properties,the glass transition temperature,and the thermal conductivity of the nanocomposites increased by 600%,5?,50%respectively.It is proved that the multi-walled carbon nanotubes modified by isocyanate could disperse well in the polyurethane elastomer.And the mechanical and thermodynamic properties of the polyurethane elastomer composites were improved due to the sp~2 hybrid structure of carbon atom in MWCNTs.Finally,the structure and properties of the melanin modified by isocyanate/polyurethane elastomer composites were investigated in detail.The melanin was modified with isocyanate,and reacted with polyols.The effect of melanin content on polyurethane elastomer nanocomposites properties were synthesised.The results showed that the dispersibility of modified melanin particles was improved,and the particles are chemically grafted into the polyurethane matrix.The best modification effect was achieved when 3%wt melanin was added,and the tensile strength increased by 60%.The thermal and oxygen aging resistance of the composite material was improved due to the delocalization structure of melanin.After 150?and 2 d aging,the physical property degradation rate of the melanin/polyurethane elastomer composites was reduced by 10%and the tensile strength increased by 6 MPa.And the high temperature tensile was significantly improved.Moreover,the initial decomposition temperature,T_g and the thermal conductivity was increased by 21?,5?.30%,respectively.The results of this thesis showed that both inorganic micro-nano carbon materials and biomass particles with sp~2 hybrid structure could improve the mechanical properties and thermal conductivity of polyurethane elastomers,which laid a foundation for the preparation of high-performance thermal conductivity polyurethane elastomers.