Nano-modified epoxy: the effect of GO-based complex structures on mechanical performance

The application of nanofillers (NFs) in multicomponent polymer systems is accompanied by important structure-directing effects that are more marked in partially miscible systems, such as polymer-modified epoxy. This study deals with rubber-modified epoxy using different combinations of GO and amine-terminated butadiene-acrylonitrile copolymer (ATBN), including in situ and pre-made grafting. Moreover, GO grafted via planar epoxy groups or solely edge-localized carboxyls was used. It is shown that the grafted ATBN chains promote the assembly of GO-g-ATBN into nacre-mimicking lamellar structures instead of usual exfoliation in thermoplastics. This complex structure of elastically embedded GO leads to the best mechanical performance. It is obvious that a small concentration of the grafted polymer exceeds the contribution of a higher concentration of separately added ATBN. The results highlight the important effect of the degree of grafted chains and geometry of the internal structure of the self-assembled arrays and their effect on the mechanical performance.

ATBN-grafted GO forms nacre-mimicking lamellar structures in epoxy; the effect of grafting geometry on the structure/property relationship is highlighted.

Multi-layer graphene oxide synergistically modified by two coupling agents and its application in reinforced natural rubber composites

Multi-layer graphene oxide (MGO) was co-modified with bis-(P,P-bis-ethylhexyldiphosphato)-ethanediolato titanate triethanolamino chelate solution (NDZ-311w) and bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si-69). Then the co-modified MGO was incorporated into natural rubber (NR) by conventional two-roll mill mixing to prepare MGO/NR composites. The large macromolecule of NDZ-311w is able to efficiently intercalate the layers and increase the interlamellar space of MGO, subsequently resulting in the exfoliation of MGO into thinner sheets with better dispersity. Moreover, the oxygen-containing polar groups of MGO can be largely consumed by Si-69, which enhances the interfacial interaction between MGO and the NR matrix and improves the mechanical properties of the MGO/NR composites. Compared to pure natural rubber, the tensile strength, the stress at 300% strain, and tear resistance of co-modified MGO/NR composites are increased by 26%, 98% and 15%, respectively.

Dichlorobenzene: an effective solvent for epoxy/graphene nanocomposites preparation

It is generally recognized that dimethylformamide (DMF) and ethanol are good media to uniformly disperse graphene, and therefore have been used widely in the preparation of epoxy/graphene nanocomposites. However, as a solvent to disperse graphene, dichlorobenzene (DCB) has not been fully realized by the polymer community. Owing to high values of the dispersion component (δ_d) of the Hildebrand solubility parameter, DCB is considered as a suitable solvent for homogeneous graphene dispersion. Therefore, epoxy/graphene nanocomposites have been prepared for the first time with DCB as a dispersant; DMF and ethanol have been chosen as the reference. The colloidal stability, mechanical properties, thermogravimetric analysis, dynamic mechanical analysis and scanning electron microscopic images of nanocomposites have been obtained. The results show that with the use of DCB, the tensile strength of graphene has been improved from 64.46 to 69.32 MPa, and its flexural strength has been increased from 97.17 to 104.77 MPa. DCB is found to be more effective than DMF and ethanol for making stable and homogeneous graphene dispersion and composites.