Study On The Functionalization Of Graphene Oxide And Its Composite Systems With Aqueous Polyurethane

In this paper, techniques like surface modification of graphene, structural design, and processing innovation were combined to prepare environmental friendly aqueous PU/graphene nanocomposites with good dispersibility of graphene nanoplatelets within the PU matrix and compatibility between the interfaces organic/inorganic. Structures, properties, and applications of composites were researched and discussed The main research contents and results are shown as follows:1) In this study, the new amphiphilic copolymer, poly (SS-co-AMPS), was prepared and first used as an effective stabilizer to prepare a kind of stable aqueous dispersion of graphene nanoplatelets. Then, PU/graphene nanocomposites were prepared by mixing this functionalized graphene nanoplatelets with sulfonic acid type water polyurethane (SWPU). TEM and SEM observations confirmed that graphene nanoplatelets were well exfoliated and homogenously dispersed in the PU matrix. Results showed that the initial adhesive force of SWPU was enhanced because of the incorporation of this functionalized graphene nanoplatelets. In addition, the electrical conductivity of the naocomposite reached up to 0.39 S. m-1. In summary, this work provides a simple way to fabricate environment-friendly conductive polyurethane adhesive.2) Amine-functionalized graphene (NH2-graphene), with primary amine (-NH2) groups and polar groups grafted onto the surface of graphene nanoplatelets by covalent bond, was successfully synthesized by reacting GO with excessive TDI and then treating with hydrazine hydrate.Subsequently, these NH2-graphene nanoplatelets were used as chain-extender or cross-linker to prepare a kind of aqueous PU/graphene nanocomposite via in situ polymerization method. Results showed that micro-phase separation of PU increased due to the incorporation of NH2-graphene by this method. Meanwhile, the mechanical strength, thermal stability, and thermal conductivity of the nanocomposite were enhanced significantly compare to the pure PU material.3) A kind of PU/graphene nanocomposite was prepared by latex co-coagulation approach,which was conducted by mixing cationic aqueous polyurethane (CWPU) emulsion with GO suspension. The results of TEM, SEM, and FT-IR analysis showed that the graphene nanoplatelets were well dispersed and exfoliated in the PU matrix due to the electrostatic interactions. Electrical and thermal conductivity of the PU/graphene nanocomposite fabricated following this approach was 6.1 and 4.9×109 times higher than pure CWPUresin, respectively. In addition, the oxygen transmission rate (OTR) of the PET film coated with this nanocomposite was significantly decreased to 0.6 cm3 m-2 day-1, indicating a high gas barrier property.4) Series of CWPUdispersions were prepared and mixed with GO suspensions, which has a different pH value. Factors that influence the stability of the hybrid dispersion have been researched systematically. Results showed that CWPU/GO complex formed by the electrostatic interactions between CWPUparticles and GO platelet are affected by several forces such as gravity force,buoyant force, and electrostatic repulsion force. The study found that the hybrid dispersion of CWPUdispersion and GO suspension finally reached a settlement when the gravity force greater than buoyant force, otherwise,it has a stable performance. Stable hybrid dispersions of CWPU/GO have been successfully prepared when control the particle diameter less than 100nm and adjust the pH value of GO suspension about 9.0. The results of TEM and SEM analysis showed that the GO nanoplatelets were well dispersed and exfoliated in the CWPU/GO nanocomposite, which was obtained by drying the hybrid dispersion,due to the electrostatic interactions. Furthermore,mechanical strength, thermal stability, and gas barrier property of the CWPU/GO nanocomposite fabricated following this approach were enhanced significantly compare to the pure CWPU.