Rubber nanocomposites carbon nanotubes

FIGURE 28.20 Curves of tan S vs temperature for rubber and carbon nanotubes (CNTs)/rubber nanocomposite. (From Lopez-Manebado, M.A. et al., J. Appl. Polym. Sci., 92, 3394, 2004.)... 

This is another important and widely used polymer. Nanocomposites have been prepared based on this rubber mostly for flame-retardancy behavior. Blends with acrylic functional polymer and maleic anhydride-grafted ethylene vinyl acetate (EVA) have also been used both with nanoclays and carbon nanotubes to prepare nanocomposites [65-69]. 

The unique two-phase structures of polyurethane that offers the elasticity of rubber combined with the toughness and durability of metal make them one of the most extensively studied and frequently used materials in carbon nanotube related nanocomposites. The main difficulty in developing CNT based polyurethane nanocomposites was how to achieve uniform and homogeneous CNT dispersion. Further investigations on the interactions between carbon nanotubes and two-phase structures are critical for the wider applications of carbon nanotube/polyurethane composites. 

In the last decade, considerable progress was observed in the field of PO/compatibil-izer (predominantly on the base of PO-g-MA)/organo-surface-modified clay nanocomposites. Polyethylene (PE), polypropylene (PP), and ethylene-propylene (EP) rubber are one of the most widely used POs as matrix polymers in the preparation of nanocomposites [3,4,6,30-52]. The PO silicate/silica (other clay minerals, metal oxides, carbon nanotubes, or other nanoparticles) nanocomposite and nanohybrid materials, prepared using intercalation/exfoliation of functionalized polymers in situ processing and reactive extrusion systems, have attracted the interest of many academic and industrial researchers because they frequently exhibit unexpected hybrid properties synergisti-cally derived from the two components [9,12,38-43]. One of most promising composite systems are nanocomposites based on organic polymers (thermoplastics and thermosets). 

NR composites and nanocomposites can be fabricated by three main techniques, namely latex compounding, solution mixing and melt blending. A variety of nanofillers, such as carbon black, silica, carbon nanotubes, graphene, calcium carbonate, organomodified clay, reclaimed rubber powder, recycled poly(ethylene terephthalate) powder, cellulose whiskers, starch nanocrystals, etc. have been used to reinforce NR composites and nanocomposites over the past two decades. In this chapter, we discuss the preparation and properties of NR composites and nanocomposites from the viewpoint of nanofillers. We divide nanofillers into four different types conventional fillers, natural fillers, metal or compound fillers and hybrid fillers, and the following discussion is based on this classification. 

When 1 wt% of CNTs were added to the rubber the stress level for the nanocomposite material increased from 0.2839 to 0.56413 MPa. At 10 wt% of CNTs the stress value obtained reached 2.55 MPa which is nine times that of pure NR." Nanocomposites of NR reinforced with SiC nanoparticles and single-walled carbon nanotubes were synthesized and processed using toluene as the solvent." Both types of nanocomposite showed an increase in initial modulus with increasing filler content, with a maximum initial modulus at 1.5% filler content. The tangent modulus at 200% strain further confirms the enhancement of reinforcement by the nanofillers at 1.5% content. 

Sanchez studied the functionalization of oxidized SWCNTs and MWCNTs dispersed in thermoplastic elastomers based on poly(butylene terephthalate) (PBT)/ poly(tetramethylene oxide) (PTMO). These nanocomposites showed good dispersion and enhancement in thermo-oxidative stability [27]. 1 % of pristine multi-walled carbon nanotube (MWCNTs) were dispersed in silicon rubber. The SR nanocomposites showed 28 % better thermal stability and 100 % improvement in the ultimate tensile strength is achieved as compared with the pristine polymer matrix counterpart [28]. Also ionic liquids have been tested to improve the dispersion and thermal stability of MWCNTs in polychloroprene rubber (CR) showing improvement in these properties [29]. On the other hand the effect of carbon nanofiber on nitrile rubber was studied. It has been found that the nanofiber increase the thermal stability and decrease the flammability [4]. 

The addition of nanoparticles to synthetic rubber resulting in enhancement in thermal, stiffness and resistance to fracture is one of the most important phenomena in material science technology. The commonly used white filler in mbber industry are clay and silica. The polymer/clay nanocomposites offer enhanced thermo mechanical properties. Bourbigot et al. observed that the thermal stability of polystyrene (PS) is significandy increased in presence of nanoclay [75]. Thermal and mechanical properties of clays multiwalled carbon nanotubes reinforced ethylene vinyl acetate (EVA) prepared through melt blending showed synergistic effect in properties [76]. 

Songmin et al. reported the preparation of chitosan hydrochloric acid salt and the effect in improving the dispersion of carbon nanotubes in different solvents and silicone rubber. It was also found that treated carbon nanotubes could be dispersed in the silicone rubber homogeneously based on SEM and XRD analysis. The incorporation of carbon nanotubes enhanced the thermal stability of the silicone rubber. They also significantly improved the mechanical properties of the silicone rubber matrix. From the FTIR spectra, it was befieved that chitosan hydrochloric acid salt adsorbed on the surface of the carbon nanotube and then interacted with silicone rubber matrix, resulting in the enhancement of dispersion of carbon nanotubes, improving thermal and mechanical properties in the resulting nanocomposites [124]. 

At the same time, Peddini et al. described the preparation of nanocomposites from styrene-butadiene mbber (SBR) and multiwall carbon nanotubes (MWCNT). MWCNT are important nanostructures due to the exceptionally high modulus and aspect ratios there has been much interest in using them as reinforcing agents for polymer composites. Styrene-butadiene rubber (SBR), commonly used as a tread stock for tires, is employed here as the matrix for creation of a masterbatch with oxidized MWCNT (12.3-15 wt%). These materials do not show a high level of electrical conductivity as might be expected from a percolation concept, signifying excellent tube dispersion and formation of a bound rubber layer on the discrete MWCNT [126]. 

Peddini, S.K., Bosnyak, C.P., Henderson, N.M., Ellison, C.J., Paul, D.R. Nanocomposites from styrene-butadiene rubber (SBR) and multiwall carbon nanotubes (MWCNT) part 1 morphology and rheology. Polymer 55, 258-270 (2014)... 

Laoui, T. Mechanical and thermal properties of styrene butadiene rubber-functionalized carbon nanombes nanocomposites. Fuller. Nanotub. Carb. NanostrucL 21, 89-101 (2013)... 

X. Zhou, Y. Zhu, J. Liang, S. Yu, New fabrication and mechanical properties of styrene-butadiene rubber/carbon nanotubes nanocomposite, Journal of Materials Science Technology, ISSN 1005-0302 26 (12) (December 2010) 1127-1132. http //dx.doi. org/10.1016/S 1005-0302(11)60012-1. 

A. Mohamed, A.K. Anas, S.A. Bakar, T. Ardyani, W.M.W. Zin, S. Ibrahim, M. Sagi-saka, P. Brown, J. Eastoe, Enhanced dispersion of multiwall carbon nanotubes in natural rubber latex nanocomposites by surfactants bearing phenyl groups. Journal of Colloid and Interface Science, ISSN 0021-9797 455 (October 1, 2015) 179-187. http //dx.doi. org/10.1016/j.jcis.2015.05.054. 

J. Ok Jo, P. Saha, N.G. Kim, C.H. Choi, J.K. Kim, Development of nanocomposite with epoxidized natural rubber and functionalized multiwalled carbon nanotubes for enhanced thermal conductivity and gas barrier property. Materials Design, ISSN 0264-1275 83 (October 15, 2015) 777-785. http //dx.doi.Org/10.1016/j.matdes.2015.06.045. 

Jiang, M.-J. Dang, Z.-M. Xu, H.-P., Enhanced Electrical Conductivity in Chemically Modified Carbon Nanotube/Methylvinyl Silicone Rubber Nanocomposite. Ear. Polym. J. 2007, 43, 4924-4930. 

Das et al. incorporated MWNTs into solution-styrene-butadiene rubber (S-SBR) /butadiene rubber (BR) a 50 50 blend, using a roll milling technique [64]. In the process, MWNTs were first dispersed in ethanol, and the nanotube-alcohol suspension was then mixed with the rubber blend in a roll mill at high temperatures, denoting as the wet-mixed composites. For comparison, MWNTs were also mixed directly into the rubber compound, forming the so-called dry-mixed composites. Figure 6.25 shows the variation in DC conductivity with carbon nanotube content for MWNT/S-SBR-BR nanocomposites prepared by wet-... 

Kueseng K, Jacob KI (2006) Natural rubber nanocomposites with SiC nanoparticles and carbon nanotubes. Eur Polym J 42 220-227... 

Rubber nanocomposites have attracted great interest for the past few years due to their unique physical and chemical properties [17]. The properties of rubber nanocomposites can be modified with various nanoparticles. There are a lot of types and shapes of the nanofillers like silica, Ti02, POSS, nanocrystals, other oxides (three-dimensional) carbon nanotubes, metallic fibers (two-dimensional) and clays, modified clays or graphene (one-dimensional). 

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