Preparation Of Covalently Grafted Graphene Oxide And Its Hybridization Modification Of Polyurethane

Graphene is a new two-dimensional honeycomb-like carbon nanomaterial with sp²hybrid structure,which has excellent mechanical,electrical,thermal and light transmission properties.Graphene sheets have strong intermolecular forces,which are easily agglomerated in organic solvents and difficult to get uniform dispersion,weakening its compound modification effect on polymers.Polyurethane is a synthetic material with high elasticity,high abrasion resistance and good biocompatibility properties,and the composite modification of polyurethane material by graphene will give it new properties.In this thesis,graphene oxide is covalently modified and the modified graphene is compounded with polyurethane elastomer and aqueous polyurethane respectively,which not only improves the interfacial compatibility of graphene and polyurethane matrix but also prepares high-performance polyurethane graphene materials with electrical conductivity.This thesis includes three main parts of research as follows.Covalent functionalization of graphene oxide(GO)with 2,4-toluene diisocyanate(TDI),4,4'-diphenylmethane diisocyanate(MDI)and 1,5-naphthalene diisocyanate(NDI)was carried out to prepare-NCO capped active graphene materials TGO,MGO and NGO to study the effect of diisocyanate structure on the modification of graphene oxide materials.The results showed that the graphene oxide materials were more effective than GO.The experimental results showed that all three isocyanate-modified graphene materials were more active,and the exfoliation and thermal stability were improved to different degrees compared with GO,and the layer spacing of TGO was expanded to 1.48 nm,MGO to 2.43 nm,and NGO to 1.06 nm.stability,and the best modification effect on GO due to the special sp³hybridization structure inside the MDI molecule.Graphene-based polyurethane elastomer composites were produced by in situ polymerization using GO(NCO@GO)covalently modified with MDI as the nano-reinforced material.The results showed that:the ordered regularity of the modified graphene was not destroyed compared with that before modification,which improved the dispersion of graphene in the polyurethane matrix,but the addition of NCO@GO did not change the microphase-separated structural characteristics of the polyurethane elastomer material;NCO@GO grafted onto the molecular backbone of the polyurethane elastomer played a nano-crosslinking role,and the addition of a small amount of NCO@GO could have a strengthening effect on the polyurethane The elongation at break of the composites showed a monotonically decreasing trend with the increase of NCO@GO content;the addition of NCO@GO improved the electrical conductivity of the polyurethane elastomer,and the electrical conductivity of the polyurethane material was increased when the NCO@GO content was 0.20%.The conductivity of the polyurethane material reached 8.34×10^-5s·cm^-1at 0.20%.The graphene-hybridized waterborne polyurethane resin was prepared from highly reactive and widely spaced NCO@GO pre-blended with isophorone diisocyanate(IPDI)as a hybrid diisocyanate by a stepwise polymerization process,and the NCO@GO/WPU paint film was prepared by aqueous emulsification and electrodeposition,and the dispersion of graphene in waterborne polyurethane and the effect of graphene content on the effects of graphene dispersion in waterborne polyurethane and graphene content on the solvent resistance,electrical conductivity and hardness of waterborne polyurethane paint film were investigated.The results showed that the addition of NCO@GO did not change the microphase separation structure of aqueous polyurethane,but the dispersion uniformity of the new graphene material in the polyurethane matrix was greatly improved;the solvent resistance of the paint film showed a pattern of increasing and then decreasing with the increase of NCO@GO content,and the best solvent resistance of the paint film was achieved when the content of NCO@GO was 0.60%;the hardness and electrical conductivity of the paint film The hardness and conductivity of the paint film increased with the increase of NCO@GO addition,and the conductivity of the paint film reached3.92×10^-2s·cm^-1when the content of NCO@GO was 1.20%.When the content of NCO@GO continued to increase,graphene agglomerated in polyurethane and the stability decreased.