I have polyethylene pellets and copper nano powder. How can I prepare polyethylene copper nanocomposite? I want to Study its thermal properties like thermal stability, thermal conductivity, coefficient of thermal expansion, specific heat, mechanical properties
Dear Muthiah, you question is very complex to answer because it is too vague. For example how long is the extruder? Is it a laboratory scale extruder? Are you asking for help on "how prepare an effectively conductive Cu-HDPE blend"?.
if you wish preparing an electrically conductive blend I suggest first of all to find an optimum copper concentration. This can be done once the particle dimensions and their aspect ratio are known. Based on a random particle distribution a theoretical percolation threshold can be found. This allows minimizing the copper content. In fact even low percentage of nano particles may give rise to large viscosity increase. However, I am quite sure that in absence of particle surface modifiers one cannot suppress completely the formation of clusters. Nonetheless, one can reach a substantial particle dispersion by means of shear force induced at the mixing stage (mixing intensity and motor speed can be roughly correlated through an instrumented mixer). For instance, fixing the temperature and motor speed one can interpret the torque-time profiles in terms of particles dispersion effectiveness.
Muthiah, I think even if you find somebody, I think this is not a productive approach. Nanoparticles are really hard to disperse in polymers, I have worked almost all my business / scientific life on this and developed a deep understanding what is possible and what is not and why.
You can look at my publications here in RG (experimental and theoretical papers).
Twin screw extruders are relatively poor dispersion machines, and nano-particles are extremely hard to disperse. I don't know how "nano" your particles are, but this is far from being such a simple question as you asked "can somebody lend me his extruder time and prepare this compound?" ... I would be extremely surprised if this succeeds this way.
Alberto, as Muthiah is talking about Cu "nano"-particles, these would be (assuming he is using a correct term) well below 1 µm in diameter, should be like 100 nm or less.
Only if the particles are well above 1 µm big (say: 5 µm and more), then these are randomly distributed (but then, these are not nanoparticles).
If around 100 nm small, these particles will not only very hard to become well dispersed (see above comment), but also they are not any more randomly distributed but will form very complex structures which allow for conductivity well below what percolation theory predicts.
Please look at the relevant papers here in RG:
https://www.researchgate.net/publication/229816762_Electrical_conductivity_in_heterogeneous_polymer_systems._V_(1)_Further_experimental_evidence_for_a_phase_transition_at_the_critical_volume_concentration?ev=prf_pub
also, I have published a non-equilibrium thermodynamical theory explaining these phenomena, if you or anyone else is interested, I will send you the RG link as well, it consists of 2 parts.
Article Electrical conductivity in heterogeneous polymer systems. V ...
Muthiah, Bernard is right. However, the theoretical threshold (that depends on the particle aspect ratio) helps you to start working with rationale amounts of particles. For instance, in a 3D framework the percolation theory predicts a percolation threshold P=0.16 for spherical particles while in a carbon nanotubes-modified epoxy the percolation threshold can be of order of magnitude of P=0.001.
Alberto, yes, but may I repeat the following: if in the nano range (like 100 nm size), the aspect ratio is relatively unimportant because the non-equilibrium structures (self-organized, so-called dissipative structures) are taking over and are much more powerful.
Percolation theory is not applicable in these cases! Why?
- because this theory implies NO INTErACTION BETWEEN THE DISTRIBUTED PARTICLES and THE MATRIX.
BUT: especially in the nano-scale, the interactions between dispersed and continuous phase are extremely powerful and important! these are creating the dissipative (self-organized) structures!
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