The fabrication of flexible multilayer graphene oxide (GO) membrane and carbon nanotubes (CNTs) using a rare form of high-purity natural graphite, vein graphite, is reported for the first time. Graphite oxide is synthesized using vein graphite following Hummer's method. By facilitating functionalized graphene sheets in graphite oxide to selfassemble, a multilayer GO membrane is fabricated. Electric arc discharge is used to synthesis CNTs from vein graphite. Both multilayer GO membrane and CNTs are investigated using microscopy and spectroscopy experiments, i.e., scanning electron microscopy (SEM), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), core level photoelectron spectroscopy, and C K-edge X-ray absorption spectroscopy (NEXAFS), to characterize their structural and topographical properties. Characterization of vein graphite using different techniques reveals that it has a large number of crystallites, hence the large number of graphene sheets per crystallite, preferentially oriented along the (002) plane. NEXAFS and core level spectra confirm that vein graphite is highly crystalline and pure. Fourier transform infrared (FT-IR) and C 1s core level spectra show that oxygen functionalities (−C−OH, −CO,−C− O−C−) are introduced into the basal plane of graphite following chemical oxidation. Carbon nanotubes are produced from vein graphite through arc discharge without the use of any catalyst. HRTEM confirm that multiwalled carbon nanotube (MWNTs) are produced with the presence of some structure in the central pipe. A small percentage of single-walled nanotubes (SWNTs) are also produced simultaneously with MWNTs. Spectroscopic and microscopic data are further discussed here with a view to using vein graphite as the source material for the synthesis of carbon nanomaterials.

The influence of low molecular weight additives containing polar groups and modified polyolefin-based compatibilizers on polypropylene (PP)-clay nanocomposites (PPCN) has been studied, in terms of intercalation and degree of exfoliation achievable by melt-state mixing processes. PPCN were prepared by melt mixing two PP homopolymers with organically-modified montmorillonite type clay, in the presence of maleic anhydride-grafted polypropylene (PP-MA) compatibilizer. XRD analysis shows that interlayer spacing of clay has been increased dramatically, while TEM results show a significant improvement of clay dispersion in the PP matrix, when nanocomposites are prepared with commercial PP containing short-chain organic additives with polar end groups. Subsequent studies based upon customized PP formulations, with amide-type slip additive, confirm the intercalation of this additive into the clay galleries and its positive and significant impact on clay dispersion. Contact angle measurements suggest that these additives diffuse into the clay gallery space rather than migrating away from the bulk of the PPCN matrix. The interaction between polar group (NH 2 ) of this additive and the polar sites on the filler surface appears to be the driving force for the intercalation. POLYM. ENG. SCI., 46:1008 -1015, 2006.

The effect of short-chain amide (AM) molecules on the intercalation of montmorillonite clay has been investigated by the melt blending of polypropylene (PP) with clay in the presence of AM molecules such as 13-cisdocosenamide (erucamide). Polypropylene-clay nanocomposites (PPCNs) were prepared by the co-intercalation of maleic anhydride grafted polypropylene (PP-MA) and an AM compound. The resulting nanocomposite structures were characterized with X-ray diffraction (XRD) and transmission electron microscopy, whereas the thermal characterization of the PPCNs was conducted by thermogravimetric analysis. XRD results showed that the AM molecules intercalated into clay galleries and increased the interlayer spacing, a result confirmed by surface energy (contact angle) and melt flow index measurements. This additive allowed the formation of an intercalated nanocomposite structure, but an exfoliated PPCN structure was also formed with the use of AM with a PP-MA-based compatibilizer. A new preparation method for PPCNs was, therefore, developed by the co-intercalation of AM and PP-MA; this resulted in a significantly improved degree of intercalation and dispersion. The enhanced thermal stability of PPCN, relative to pure PP, further demonstrated the improved clay dispersion in the nanocomposite structures prepared by this method. A possible mechanism for the cointercalation of AM and PP-MA into the clay galleries is proposed, based on hydrogen bonding between these additives and the silicate layers. Consideration is also given to possible chemical reactions and physical interactions in this rather complex system.

Natural rubber (NR) latex-clay nanocomposite (NRLCN) synthesized with montmorillonite (MMT) clay aqueous dispersion was evaluated for reinforcement and barrier properties. The physio-mechanical properties of the NRLCN were compared with the conventional NR latex composites containing CaCO 3. The NRLCN structure was characterized with X-ray diffraction and scanning electron microscope techniques. The X-ray diffraction data showed that, with a lower concentration of clay, a highly exfoliated clay structure was achieved whilst the clay aggregation gradually resulted in a higher concentration of clay. The crosslink density as computed based on the solvent absorption data of the latex nanocomposite films was increased with the increase of clay concentration. As a result of nanoscale dispersion of the montmorillonite clay and higher crosslink density of the latex nanocomposite films, the resistance to permeation of small molecules through the NRLCN was significantly enhanced in comparison to conventional NR latex-CaCO 3 composites. Solid state mechanical properties of NRLCNs showed a significant reinforcement effect of dispersed clay platelets but without significantly reducing the elastic properties. The higher mechanical properties and improved barrier resistance indicated that NR latex nanocomposites containing montmorillonite clay is a potential replacement for conventional NR latex composites containing CaCO 3 .

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Layered structures in inorganic minerals are not easily intercalated when combined with conventional non-polar polymers such as polypropylene (PP). A new co-intercalation method is reported whereby the combined influence of low molecular weight polar additives and polyolefin-based compatibilizers on PP-clay nanocomposites (PPCN) has been investigated. Our research has shown that the interlayer spacing of montmorillonite clay increases dramatically, and increased particle dispersion is achieved, when short chain, organic additives (typically amidetype, AM) are included. In this work, the migration of these additives into the clay galleries has been confirmed by surface energy data (from contact angle experiments) and by various capillary flow measurement techniques. Shear flow data have been used to interpret the mechanism of intercalation, following compound preparation using melt-state mixing processes. At relatively low concentrations, the erucamide molecules assist the intercalation process in nanocomposites; however if an excess of AM is apparent within the bulk polymer melt, unusual flow behavior is observed which can be attributed to wall slip. Modified melt elasticity is also obtained with the PPCN's leading to reduced die swell characteristics in extrusion processes. Significant differences in melt flow behavior can therefore be attributed to the presence of AM; a mechanism for co-intercalation has been proposed in terms of hydrogen bonding between the additives and the silicate layers.

Organically modified montmorillonite (OMMT) clay was intercalated with low-molecular weight polyethylene glycol (PEG) oligomer at melt stage. The intercalation behaviour of PEG into the OMMT clay galleries and its interaction with clay platelets were characterized with X-ray diffraction (XRD) and differential scanning calorimetric techniques. A natural rubber (NR)-organoclay nanocomposite (NROCN) was prepared by melt-compounding of NR with PEG-treated organoclay (P-OMMT) and other compounding chemicals using a laboratory-scale internal mixer. XRD analysis of the nanocomposites revealed the intercalation of NR molecules into the P-OMMT clay galleries and subsequent exfoliation during the melt-compounding process. Vulcanization characteristics of the NROCN, especially processing safety and optimum curing time, have been interpreted with reference to the organic modifier of the montmorillonite clay, PEG modification and the degree of exfoliation. Solid-state mechanical properties of P-OMMT clay-filled NROCN vulcanizates have shown a significant enhancement in stiffness and strength characteristics whilst without scarifying the elasticity of the nanocomposites. Results have been explained in terms of the degree of exfoliation, dispersibility of the organoclay and strain-induced crystallization of the natural rubber.

Latex crepe rubber is the purest form of natural rubber and contamination of crepe rubber with metal ions should be avoided to maintain the quality of the rubber, especially to prevent the oxidative aging during storage. The influence of iron in processing water on raw rubber properties of crepe rubber has been investigated. Our research has shown that most of the iron ions contaminated from the processing water were leached out during the production process. The remaining iron ions in the crepe rubber catalyse the thermo-oxidative degradation and thereby significantly affect the oxidative stability of the rubber. Combination effect of Fe 3+ ions and aromatic thiol, which adds into natural rubber (NR) latex to bleach the yellow pigments in fractionated bleached (FB) crepe rubber, further reduced its resistance to thermal oxidation, measured by Plasticity Retention Index (PRI). Therefore, fractionated unbleached (FUB) crepe rubber has a better oxidative stability than fractionated bleached (FB) crepe rubber. Further investigations carried out to study the effect of oxidation state of iron showed that not only Fe 3+ ions but also Fe 2+ ions catalyses the oxidative degradation process of natural rubber (NR). Based on our experimental results, new specifications for total iron concentration in the processing water and maximum allowable iron concentration in latex crepe rubber have been proposed.