Hi,

it is called nanoreinforcement. Briefly, the polymer adsorbed on the particle surface gets immobilized. That, in turn, confines the movement of the neighboring polymers in the so-called frustrated layer. Less mobility = less deformation -> the material is stiffer. This effect is especially strong above Tg, where polymers have high mobility, but it could also be detected below Tg.

Article Effect of Nanoparticle Organization on Molecular Mobility an...

Article Mechanical properties of glassy polymers with controlled NP ...

The interaction is rather short-ranged (

Nanoparticles can improve the polymers mechanical and physical properties, or/and they can worsen some properties or/and improve only some - depending on the type, amount, dispersion. If you could ask directly - if Nanocor XX.YY will improve Tg of PP, it could be easier to answer.

Petr Lepcio Thank you very much for your answer. But could you please explain to me more what does "the polymer adsorbed on the particle surface" mean? Thank you.

Janusz Rebis I have incorporated carbon nanofibres, silica, clay, cellulose nanocrystals and graphite into Sika-30lp epoxy adhesive. So I need to know, briefly, how incorporating these nano's affect the adhesive properties. Thank you.

Dear Mohammad Al-Zu'bi, adsorption is a physical process establishing a non-covalent interaction of some species (polymer chain) on a hard surface (particle) through physicochemical forces. If the polymer-particle interaction is favorable (they have good mutual affinity), the chains will stick on the particle surface. If the affinity is weak, the chains will be repelled from the particle surface, and there will be no nanoreinforcement while the particles will usually aggregate. Large aggregates concentrate stress and act as critical defects above a certain size. You may check the links to the papers I posted above, where we explain it in more detail.

You have a combination of hydrophilic (clay, cellulose) and hydrophobic (carbon nanofibers and graphite) fillers, so you need something which has both hydrophobic and hydrophilic functional groups providing good affinity to both types of surfaces. I don't know the exact composition of the Sika-30Ip, but bisphenol-derived epoxies are generally a good pick for this task. However, don't forget to check the curing efficiency. It often goes down in the presence of particles and can easily outweigh any potential nanoreinforcement the nanofillers might have. Moreover, the carbon fibers are not nanofillers, so add the volume replacement and stress transfer mechanism to your equation.

Dear Petr Lepcio , Thank you very much for the clarification.

Could you please, briefly, explain to me the reason of "It often goes down in the presence of particles"?

A last question if you wouldn't mind, why the carbon fibres are not nanofillers? Is that because of their cotton-like nature or something like that? Many thanks in advance!

That's a complex thing. The exact interaction depends on the curing mean (heat, chemical, light) and mechanism (free-radical, cationic). Dispersed particles with good affinity to the resin increase viscosity due to the adsorption (same as with the nanoreinforcement). That slows down all processes, including the curing progress, especially after you reach the gel point. That usually happens sooner (at lower conversion) with the nanoparticles due to the nanoreinforcement.

However, some nanoparticles can give a specific electron interaction with the reaction's active center. Light absorption is critical in photocuring. On the other hand, some particles may have the opposite effect and increase the conversion, but that depends on the specific combination of the polymer/resin.

Article Photoactivity, conversion kinetics, nanoreinforcement, post-...

The conversion is easily determined by FTIR/Raman measurement, and most material parameters scale with it, including thermomechanics, dielectric properties, heat conductivity, etc.

Carbon fibers are not a nanofiller simply because they are too big to be nano, typically several microns. If you insist on using a nanofiller, you can use carbon nanotubes instead. Their typical diameter is tens of nanometers. However, even the nanotubes are usually still long enough (several microns) to consider the stress transfer effect.