Elastomers that crosslink with clay nanocomposite reinforcement

The best-performing composite was prepared with H30 at 8 wt. % montmorillonite. The ratio 1.83 indicated the largest enhancement of modulus relative to the pure polyurethane for the 8 wt.% containing composites. The percent elongation to failure increased from 236 15% for the pure polymer to 374 32% for the 8% loaded polyurethane-montmorillonite composite. These hyperbranched polyols provide a significant enhancement of mechanical properties for the polyurethane cure chemistry evaluated with Cloisite 30B as the dispersed-phase reinforcement. Additional work needs to be done with Cloisite 30B present during the cure to ascertain if further benefits to mechanical properties are derived from the reaction of the isocyanate with the primary hydroxyls on the quat exchanged onto the montmorillonite. 

Elastomers that crosslink with clay nanocomposite reinforcement 

Mechanical evaluations of rubber-montmorillonite composites provide a common theme. Full exfoliation of montmorillonite in rubber is difficult. Enhancement of mechanical properties is greater than with thermoplastic polymers, because the difference in the modulus of the continuous rubber phase in relation to the montmorillonite dispersed phase is greater. Percent elongation to failure increases, modulus increases, and tensile strength increases as the concentration of montmorillonite increases in the rubber. 

An excellent example of this is found in the patent application by Powell [59]. A Ferro Fab Banbury mixer was utilized to prepare a nitrile rubber (Nipol 150 41% nitrile content) montmorillonite composite. The mixing temperature was maintained under 120 °C the fill factor was 60%. Cloisite 10A was added to the mixing rubber in three increments over a 15 min period. Zinc stearate was added phr after all of the organomontmorillonite was added. The combination of zinc oxide and stearic acid was not used, so as to eliminate the addition of a larger sized dispersed phase (zinc oxide) that could compromise mechanical performance. The zinc stearate-montmorillonite-nitrile rubber dispersion was removed from the mixer and passed through a two-roll mill six times to finish the dispersion. The dispersion was returned to the Banbury. Sulfur 

Characterization of the montmorillonite-rubber composites was carried out using WAXS, TEM, and SEM. The TEM and SEM results were not reported in the patent application. The montmorillonite was intercalated and highly aligned in the direction of applied stress. The WAXS peaks were narrow and indicated a (001), (002), and (003)d-diffraction pattern. 

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