Dispersing A Filler In Rubber

Dissolution won't change the properties of the rubber. Synthetic rubbers are all solution polymerized, and they have already been dissolved and dried prior to your work with them. A second round of dissolving won't change their properties as long as the solvent you use does not chemically react with the rubber.

The properties of solution-dispersed vulcanizates may be different than mechanically masticated compounds'. The standard blending process requires a lot of energy and can heat up the rubber substantially. Mastication of the rubber changes its rheological properties and can cause some chain scission of the raw material. So blending the nano-particles into dissolved rubber then drying the mixture could change the properties of the rubber relative to the standard blending process. Chen et. al. (US Patent No. 7,790,798 B2) claim that solution-dispersion of silica improves the final properties of the vulcanizate when compared to standard mastication, so your approach could be very beneficial.

Thank you for your comments

The answer above is correct and incorrect at the same time:

the chemical situation regarding the possible reactivity to bind to other molecules will remain unchanged.

But the physical situation: changed surface, changed vicinity to foreign surfaces, absorption of "new" materials to the surfaces, films (Langmuir-Blodgett) on surfaces - all this may considerably change the situation.

All the physical influences may act by pure physical forces as capillarity and absorption-desorption but may also act as catalysts.

I had a big problem with a high-temperature epoxy glue.

This is usually cured between 180 and 240°C. But after dissolution and film-like deposition on the surfaces to be glued and after baking at 100°C the intended procedure of matching the surfaces and curing did not work.

The curing temperature was raised from above interval. So we had to cure near 300°C to get cured and stable and strong adhesion.

Discussion with epoxy-experts yielded that either the slight corrosion of the surface or the residuals from the solvents may be the culprits.

But there may be simply the much-thinner-than-usual thickness of the glue that changed the properties. (We tried 3 µm thickness - that is nearly bulk in simple thinking and well above the estimated molecule size of near 1 nm.)

RHABE

The higher the surface area of the nano-filler, the harder it gets to disperse. So wetting the nano filler (clay) will be a trick/technique to disperse filler into rubber. Typically you get very high reinforcement which will result in high tensile strenth, tensile modulus, increased hardness and tear strength. But you will see decreased elongation. High reinforcement is a function of your filler's (nanoclay) surface area and structure

• It is a good idea to have a solution of rubber and filler together and then use a high speed mixer - (for cast and dry types)
• Usually, the rubber is milled and filler and other ingredients are added while milling- but if the nano clay has orientation like high aspect ratio, structure may be broken during high shear mixing when you use mills and banbury type mixers
• Solvent type dispersion may have side effects like complete solvent drying and auto ignitions
• Caution: Nanoclays based on Sodium Montmirrillonites may be hydrophilic - just check