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Posted: Mar 16, 2015

Research proves single wall carbon nanotubes capable of significantly improving elastomer properties

(Nanowerk News) The rapidly developing rubber industry is facing on increasing growth in property requirements, from increases in elasticity, strength, and resistance to aggressive environments, weatherability and many others. Many of these improvements will require a complex of new materials and technology. Some of these targets, however, can be reached by combining a rubber blend with single wall carbon nanotubes. A third party has researched the influence TUBALL-branded single wall carbon nanotubes have on elastomers. Recent results have demonstrated the positive impact single wall carbon nanotubes can make to the physical, mechanical and chemical indexes of elastomer composites.
To start with, increasing the concentration of single wall carbon nanotubes in the elastomer composite blend improves tensile strength and reduces tensile elongation. In parallel, the hardness of the blend increases, which is proved by Shore A test results. These strength improvements also indicate a good distribution of single wall carbon nanotubes in the material. Therefore, the ultimate strength of the composite is higher, and enabling it to withstand heavier mechanical loads than the control blend.
Additionally, increasing the concentration of single wall carbon nanotubes in the composite lowers residual deformation under compression. Thus, it can be presumed, that the blend with such a composition will perform better when subjected to permanent and variable deformation after adding the single wall carbon nanotube modifier. This allows for the additive to be viable for producing a number of elastomer products, including seals, compactors and other mechanical rubber goods. Another added effect is also that electrical resistance of the blend is reduced. This may be used to improve a number of elastomer products, such as electrodes, electrical current conductors, electrical and radiotechnical devices, coatings for charger units and batteries, and so on.
Higher concentrations of nanotubes also significantly shortened the start time of vulcanization and notably speeded it up. Though the blend’s viscosity increased, this change was insignificant, and it did not influence energy consumption on production. Noteworthy, higher vulcanization speed can be also a consequence of existing functional groups, meaning single wall carbon nanotubes don’t just organize their own 3D matrix but also chemically interreact with the composite matrix in process of vulcanization. Higher vulcanization pace also increases the speed of material processing, which means it requires less time to produce one product unit. However, the possibility of early vulcanization for large products should be kept in mind. This will require additional research to obtain more clarity on the matter.
While testing the abrasion of samples, the loss indicator of the testing composites decreased and resistance to abrasion went up after increasing the concentration of nanotubes in the blend. It must be noted that increasing the strength by just 10% decreased abrasion by 15%, which is a significant improvement. Products based on this composition will be more wear-resistant when exposed to frictional forces, which is one of the priority goals while producing conveyor belts, automobile tires and other goods subject to such loads.
As for glass transition temperature, research results demonstrated an increase within the limits of experimental error. Increasing elasticity modulus under all testing temperatures indicated that single wall carbon nanotubes positively influenced the mechanical properties of the material, with minor changes in the mechanical loss factor.
With higher concentrations of nanotubes, a lower tan δ at 60°C demonstrated a decrease in the rubber blend’s hysteresis loss. Except for the maximum concentration of added nanotubes, where can be noticed the leap. Therefore, at 60°C many deformations will have a bigger influence on rubber fatigue with maximum concentration than with any other. Young’s modulus changes were insignificant, except for the highest concentration of nanotubes. The latter case demonstrated a significant change: it required much more effort to deform the sample. This means that materials with the maximum practical concentration of single wall carbon nanotubes will have greater durability, within the range of testing temperatures (-10 — 60°C). One additional positive factor is the minor change of tan δ at 0 °C that defines wet road grip.
nanotube properties
(click on image to enlarge)
All property improvements mentioned above demonstrate that adding single wall carbon nanotubes to rubber blends improves strength characteristics, abrasion, hysteresis loss, elasticity, vulcanization speed and residual deformation under compression. The practical explanation for these improvements is that nanotubes of this kind organize their own dimension network embedded in the composite matrix: electrical resistance decline proves this along with physical and mechanical testing data. Regarding the best concentration option: the research results defined it to be 0.2% — this being the optimally observed amount to improve material properties
Source: OCSiAl
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