No wonder. PTFE does not melt and has extremely low surface energy, therefore it is virtually impossible to mix it with other plastics in the molten state. It is possible to prepare PTFE powder filled plastic compounds, but even there the wetting is poor.

Dear Gyorgy,

Thank you very much for your reply. Indeed, thermodynamically the polymers are not miscible. The polymer blend can be a complicated topic as additional interactions may contribute to the final outcome. Nevertheless, the question does not aim solely at polymer blends but also at PVDF based composites, where a filler is added to the polymeric matrix. Thermodynamically, the miscibility is at least theoretically possible in this case.

The low surface energy may be an issue but...if we are looking at nancomposites then the filler generate a huge surface area and hence....we may have a solution!

Now the problem is that technically the polymeric blend can be also depicted as a nanocomposite and you may have in certain cases a huge surface area...unfortunately this aspect is not very well considered in theoretical models and simulations!

Then you should try PTFE nanopowder - there are several hits on Google. You may also try to use fluorinated surfactants and fluoro-copolymer compatibilizers. I have no personal experience in this field perhaps someone else may help more effectively.

Ultrasonic sintering may be suitable. Chemically or plazma etched PTFE powder is also promising.

Plasma etching is a potential method for activating the surface of a PTFE powder sufficiently to blend it with other polymers. It will require a very active plasma, either oxygen or fluorine, to achieve enough change in surface energy to promote compatibility. There will still be potential issues of agglomeration of the PTFE particles during mixing unless you use a method with high dispersion energy.

It is possible to make PVDF/PTFE composites by latex blending (see my publication list to find the reference).

In the latex form, PTFE particules can be as small as 100nm.

It is quite easy to blend two latexes (provided the surfactants are compatible) at any ratio, coagulate, filter, wash, and dry to obtain a powder. The powder can be melt process by extrusion, injection molding, ..

Nowadays most polymers can be dispersed in water as a latex/mini-emulsion, using surfactants, high shear and/or solvant.

@Syeda irsa Mazhar   -> Yes, sure, by use of perfluorinated surfactants (currently perflurobutylsulfonates are allowed). In the case of surface treated PTFE (with polar groups), it is possible to use usual surface active substances.

http://www.sigmaaldrich.com/catalog/product/aldrich/665800 - PTFE dispersion on sale. Please check citation #37 from yours citation - it also contain relevant info

Dear Andrei,

Your suggestion is good...however is not providing a path to melt mixing.

Gyorgy is correct, but we may play a little with surface features...or at least I do hope. 

Apparently there is a possibility... but this requires temperatures between 400 and 450 C and inert atmosphere (vacuum or nitrogen). Has anybody such capabilities?

->Mircea Chipara   Thanks for estimation of my idea as "good" :-) In contrary to Gyorgy statement, PTFE have melting point T=327OC (https://en.wikipedia.org/wiki/Polytetrafluoroethylene) , but it soften at much lower temperature (200-300OC) - PTFE is used in polymer processing as flame retardant https://books.google.ru/books?id=LAmOb4p8IwIC&lpg=PA11&dq=phosphorus%20pentafluoride%20flame%20retardant&hl=ru&pg=PA11#v=onepage&q=phosphorus%20pentafluoride%20flame%20retardant&f=false

Processing of PTFE at "400 and 450 C...(vacuum or nitrogen)." will produce  mixtures of gaseous tetrafluoroethylene, perfluoropropylene and perfluorobutenes - in various ratios, depend on pressure.

New method of surface compartibility of PTFE is developed recently based on Atomic Layer Deposition (ALD) with Me3Al. This method is relative available and suitable also for PTFE nanopowders - exactly what you need https://www.researchgate.net/publication/257010774_Induced_wetting_of_polytetrafluoroethylene_by_atomic_layer_deposition_for_application_of_aqueous-based_nanoparticle_inks

Article Induced wetting of polytetrafluoroethylene by atomic layer d...

Andrei,

Indeed the fluorine gas evolution is a huge problem. However, TGA does not show an important mass loss in PTFE below 450 C (in nitrogen). There is the problem of time, but we may imagine a short energetic melt mixing-at least in theory. Softening of PTFE may be tentatively exploited. 

Dear all,

Is it possible to add Sio2 nano particles in PTFE? if yes what is the procedure.

pls guide me.

Andrei...still about PTFE

What is the smallest size of PTFE powder that can be purchased? If possible I will appreciate also some details to contact the vendor....

I'm doing Ni-PTFE electroless plating, however, my problem is how to dispersed PTFE powder. Some fluoro surfactants can be used to dispersed PTFE powder, but the particles after dispersion are till very big, which can not deposit with Ni layer. Can anybody suggest me a way to make PTFE powder being finer? Should I use high speed mixer machine. Actually, now I'm only use stirring about 500 rpm.

You may try a high power sonication, probably in a water dispersion of PTFE. However, it is necessary to check for potential degradation (drop of the polymerization degree) by some techniques (for example by monitoring the TG).

Thank you very much for your suggestion. Yes, I will try it.