Study On Improving Thermosetting Resin With Nano Silica

Polymer/inorganic nanocomposites have attracted extensive interests due to their unique properties.It has overcome parts of the pure materials and traditional composite materials drawbacks,and combined the advantages of polymers(elasticity,flexibility,dielectric)and inorganic materials(rigidity,high thermal stability)together.Finally,they have brought some special properties.Nano silica particle is one of the most useful inorganic fillers in polymer/inorganic nanocomposites.With several favorable advantages such as nontoxic,inexpensive,and high thermal resistant,it has been considered to be a very useful reinforcement of polymer matrix to form hybrid networks.However,difficulties in the use of SiO2 into polymer matrix have been found,primarily due to the formation of aggregates and the incompatibility between the SiO2 surface and polymer chains.Therefore,it is necessary to modify the surface of SiO2.Thermosetting resin is one kind of very useful materials,which exhibits superior mechanical properties,excellent dielectric properties,low moisture absorption,good thermal stability,superior flame resistance,high tensile strength and modulus,low cost and low volume shrinkage,ect.The typical thermosetting resins,such as cyanate resin,epoxy resin,have been widely used in many fields such as machinery manufacturing industry,structural aerospace,electronic insulation,corrosion resistance,microwave-transparent composites.However,some drawbacks of thermosetting resin restrict its structural applications,such as high stress and brittleness.So,it is very necessary to find ways to improve the mechanical properties of thermosetting resin.Based on the background above,firstly,SiO2 was activated in piranha solution to remove the residual impurities and introduce hydroxyl groups on the SiO2 surface.Then double isocyanato chemical reagents,such as IPDI,were used to react with the hydroxyl groups on the SiO2 surface.So isocyanate groups were attached onto the surface of SiO2.Finally,HTPB was introduced onto the SiO2 surface through through chemical bonding between the isocyanate groups and the hydroxyl groups of HTPB.In order to investigate the covalent bonding,grafting efficiency and dispersion of SiO2,FT-IR,TGA and TEM were employed.The characterization results showed that the polymer chains had been grafted onto the surface of SiO2 successfully via coupling agents.The grafting amount of this route was much higher and the massive agglomerations of pristine SiO2 disappeared.Then the CE/F-SiO2 nanocomposite was prepared by mixing the F-SiO2 and CE resin,and the effect of the addition of the F-SiO2 on CE resin was investigated.Universal testing machine and TGA were used to study the mechanical and thermal properties of the nanocomposites.The results showed that when the F-SiO2 content was 4 wt%,the the flexural,impact strength and Kic were increased by 31%,35%and 35%(118.31 MPa,11.49 kJ/m2 and 1.16 MPa·m1/2)compared with the neat CE resin.In addition,the TGA curves of CE/F-SiO2 system were shifted toward higher temperature,and the 10 wt%weight loss temperature was increased by about 10?for the 6 wt%system.The addition of F-SiO2 improved the thermal stability of the systems;TEM and SEM were used to investigate the dispersion of SiO2 and the fracture surface of the nanocomposites.Compared with pristine SiO2,the dispersion of F-SiO2 was better in CE resin.And with the addition of silica nanoparticles into the resin,the fracture surface morphology changed greatly where a much rougher surface with more ductile sunken areas appeared,which indicated that crazing was increasing with the addition of F-SiO2;DSC was employed to study the effect of F-SiO2 on the extent of the CE cure.When the F-SiO2 content was 6 wt%,the cure peak temperature was from 289? to 227?,which indicated that the addition of F-SiO2 can significantly catalyze cure of the CE.Then,the double isocyanato chemical reagents and the grafting polymer chain were changed,and the effect of surface active agent on the preparation of F-SiO2 was investigated.The results indicated that,the addition of TEAB can improve the dispersion of SiO2 in xylene solution,so the grafting amount of polymer chain was increased.Then,the EP/F-SiO2 nanocomposites were prepared,and the effects of the addition of the F-SiO2 on EP resin were investigated The characterization results showed that the addition of F-SiO2 can have the similar effect on EP resin.The strength and toughness of the system were enhanced,and the thermal stability of the systems was improved,too.The traditional modification methods,such as adding rubber,exist some drawbacks of higher loading of fillers,damaging the toughness and the thermal stability of systems.However,in our modification method,the strength and toughness of the system were enhanced by adding only tiny amounts of SiO2.In addition,the sysytem exhibited better thermal stability.So,it is an efficient way to modify the thermosetting resin.