| Graphene composites have shown great application prospect in the electrical, thermal management, catalytic fields etc. Based on graphene excellent performance, it has been widely used in polymer composites. But because the intrinsic π-π stacking interaction and Van der Waals force between graphene layers easily results in poor dispersion and compatibility in solvent and matrices. So modifying graphene to improve the dispersibility and compatibility in solvent and matrices is very important. There are two modification methods: covalent modification and non-covalent modification. The covalent modification not only can solve the problems of the dispersibility and compatibility, but also can make graphene own better performance due to the introduction of new functional groups. Therefore, it extends the applications of graphene. Hence, researchers have focused their efforts on the creation of solution-processable graphene oxide(GO), because it includes many oxygenic functional groups, which provide the modification reaction site. At present, in order to expand graphene application in high performance biological material preparation, polyethylene glycol modified graphene oxide has been reported by a lot of literatures to improve the biocompatibility of graphene. However, few reports of polyethylene glycol modified graphene oxide used in polymer materials have been reported. This paper studied the preparation of polyethylene glycol(PEG) modified graphene oxide, and the effect of PEG chain length or modified GO content on the thermal properties, combustion properties etc. of polymer matrice, including polypropylene(PP) and polyamide(PA). Main work content is as follows:1. A modified Hummer’s method was used to get GO and its reduction product graphene(r GO), then different molecular weight of double amino-terminated polyethylene glycol(NH2-PEG-NH2) was used to covalent modify GO and then reduced to obtain the products(maked as GP); specific molecular weigh NH2-PEG-NH2 was used to modified GO to get GO-PEG. The structure and morphology of the GO, r GO, GP and GO-PEG were confirmed though FTIR, XRD, Raman, XPS, TEM, AFM analysises. These products are prepared for the follow-up researches about the application of the PEG modified GO in polymer matrices.2. When graphene contents are the same, r GO and three kinds of molecular weight GP were compounded with polyamide 6(PA6) through solution mixing to get products(marked as GA composites) with graphene content of 5.0 wt%. Emphasis was on the relationship between thermal performance of GA and molecular weight(or chain length) of NH2-PEG-NH2. The thermal conductivity of GA composites including through-plane(λz) and in-plane(λx) directions both changed with PEG chain length change. Results showed that λz was enhanced with the chain length of NH2-PEG-NH2 increased, but λx reached a maximum value at a certain chain length of NH2-PEG-NH2. The maximum λz and λx of GA are 0.406 W?m-1?K-1 and 9.710 W?m-1?K-1, respectively. The enhancement of λx is about 3.4.3. When molecular weights of NH2-PEG-NH2 are the same, a certain molecular weight NH2-PEG-NH2 was used to get GO-PEG, and then was compounded with maleic anhydride grafted polypropylene(MAPP) using solution blending and reactive compatibilization at the same time to get the composites PP-g-GO/MAPP, in which the PP-g-GO is the reacted products of GO-PEG and MAPP. Characterizations analyze the compatibility between modified GO and the matrix MAPP, andthe effect of GO content on the flame properties, thermal stability and crystallization properties of composites. Results of thermogravimetric and microscale combustion calorimetry analyses revealed an increase in Tmax by 51 °C and reductions in the total heat release and peak heat release rate by 44.4% and 38.9%, respectively, upon the addition of 2.0 wt% GO relative to pure MAPP. In addition, the mechanical properties of PP-g-GO/MAPP/PP blends are also reported. The PP-g-GO/MAPP serve as functional masterbatch in PP-g-GO/MAPP/PP blends. |
PDF Full Text Request