Chemical Modification Of Graphene Oxide And Its Application In Polymer Blends

Graphene is a two-dimensional film consists of one layer of carbon atoms. It is the thinnest material by far. Graphene oxide(GO), the precursor of graphene, is a monolayer material after oxidation and exfoliation of graphite, and can become graphene after reduction. Both graphene and graphene oxide have large specific surface area and excellent performance, but graphene oxide contains a range of reactive oxygen functional groups, which is different from graphene, and these groups are beneficial to its interaction with other polymers, as well as its chemical modification. So graphene oxide is an ideal raw material in a variety of applications. Many studies have proved that there are epoxy and hydroxyl groups on the graphene oxide dominant surfaces and carboxyl groups on its edges, and there are also hydrophobic network structure consisting of unoxidized benzene rings on its plane, so graphene oxide is an amphipathic substance. According to these structural characteristics of graphene oxide, we focus our studies on the modification of it, aiming at improving its interaction with other polymers, and applying it to polymer blends as a kind of compatibilizer. The main contents are as follows:(1) We used the improved Hummers method, namely the intercalation and oxidation of graphite and further exfoliation of it to monolayer by using the ultrasound, and then we prepared the graphene oxide successfully. All the test results show that, using this method can prepare high-quality graphene oxide and compared with the traditional Hummers method, this method costs lower, safer and more environment-friendly.(2) We covalently functionalized the graphene oxide by using the epoxy groups on its surface to improve its interaction with polymers, and this is beneficial for the graphene oxide to become polymer blends compatibilizer. Details are as follows: a. mixed the ethylenediamine and graphene oxide and prepared the amine-terminated graphene oxide(NH2-t-GO) by the nucleophilic substitution reaction between amino groups and epoxy groups on graphene oxide. b. mixed the NH2-t-GO and polypropylene-graft-maleic anhydride and prepared the PP-grafted graphene oxide(PP-g-GO) by the reaction between acid anhydride groups and the amino groups on NH2-t-GO. Both FTIR and XRD analysis have detected the presence of PP chains; TGA analysis results show that the grafting rate of MAPP can reach to 65.73 %; Raman spectroscopy shows that the oxidation and functionalization can introduce a large number of defects and reduce the crystal size greatly.(3) We used the PP-grafted graphene oxide(PP-g-GO) in the immiscible polymers PP and ABS blends as the compatibilizer. Details are as follows: a. melting blended PP and ABS in different proportions and studied their mechanical property differences of the uncompatibilized and compatibilized blends. Results show that the mechanical strength is enhanced at all proportions while the toughness shows a downward trend. b. Fixed the blend ratio at PP/ABS=30/70 and added different amount of PP-g-GO, then studied their property differences of the uncompatibilized and compatibilized blends. SEM images show that the compatibility is improved significantly after adding PP-g-GO; TGA, DMA, DSC, the tensile and impact tests and the rheological tests show that their thermal stability, ability to resist deformation, viscosity, degree of crystallinity and tensile and impact strength are also improved. But too much PP-g-GO may destroy the properties due to agglomerate and the compatible effect is not obvious at molten state.