Study On The Functionalization Of Graphene And Its Composite With Polyurethane

Graphene embraces unique two-dimensional structure and excellent mechanical,thermal and chemical properties.It has become the research focus of materials science,chemistry,physics and other fields of research due to its important application value and broad application prospect in many high-tech fields.However,graphene is chemically inert and insoluble in some common solvents,which limits its wide range of applications.In term of these,the surface of graphene oxide(GO)was modified by phenyl isocyanate to improve its dispersibility and interface bonding strength with polyurethane(PU)matrix in the research.On the basis of this,the successful combination of polyurethane(PU)and functionalized graphene(iGO)was realized via in situ polymerization and solution blending,while neat PU was seperately synthesized under the same conditions for comparison,and the effect of iGO on the mechanical and thermal properties of iGO/PU nanocomposites was investigated(1)Graphene oxide(GO)was prepared via improved Hummers method,followed phenyl isocyanate was grafted onto the surface of GO by the chemical reaction between hydroxyl groups(-OH)and carboxyl groups(-COOH)on the surface of GO with isocyanate groups(-NCO)in phenyl isocyanates.Subsequently,the modified product of iGO was characterized by FT-IR and XPS,and its dspersibility was also investigated.The results showed that carbamate group(-NH-COO-)and amide group(-CO-NH-)exist on the surface of GO,which indicated that the phenyl isocyanate is successfully grafted onto the surface of GO.Comparing the dispersibility of iGO and GO in different organic solvents,it was found that the dispersibility of modified iGO in organic solvent was better than GO.(2)The iGO/PU nanocomposites with different iGO contents(0.2,0.5,1,1.5 wt%)were prepared via in-situ polymerization method,and then the effect of iGO on the mechanical and thermal properties of PU nanocomposites were investigated.The results showed that iGO was uniformly dispersed in the PU matrix when the content of iGO was less than 1 wt%,and the aggregation of iGO was occurred in the PU matrix when the content of iGO exceeds 1 wt%.The tensile strength and elongation at break of nanocomposites appeared the variation tendency of dropped after increasing with the increase of iGO content.It is found that the most significant improvement of the tensile strength(4.3 MP)and elongation at break(500%)is obtained with iGO at 1 wt%content,compared with neat PU increased by 127.1%and 27.3%,respectively.The thermal stability of PU nanocomposites are also similar to that of mechanical properties.When the content of iGO is 1 wt%,the weight loss temperature respectively reach 320 ℃(weight loss rate is 5%)and 350.2 ℃(weight loss rate is 15%),Compared to pure PU,increased by 23 ℃ and 18 ℃,respectively.(3)The iGO/PU nanocomposites with different iGO contents(0,0.25,0.5,0.75,1 wt%)were prepared via solution mixing method,and then the effect of iGO on the mechanical and thermal properties of iGO/PU nanocomposites were investigated.The results showed that iGO was uniformly dispersed in the PU matrix.The tensile strength and elongation at break of nanocomposites appeared the variation tendency of increasing with the increase of iGO content.It is found that the most significant improvement of the tensile strength(46.8 MPa)and elongation at break(521.3%)are obtained with iGO at 1 wt%content,compared with neat PU increased by 72.4%and 18.9%,respectively.The thermal stability of PU nanocomposites are also similar to that of mechanical properties.When the content of iGO is 1 wt%,the weight loss temperature respectively reach 324.8 ℃(weight loss rate is 5%)and 355.8 ℃(weight loss rate is 15%),Compared to pure PU,increased by 20 ℃ and 16 ℃,respectively.