Could you give me an idea of how to develop a polymer possessing very high rather long-term (weeks) heat stability ? - at least above 450C with short-term excursions above 700C.
It should be a melt-processable but could be an organic-inorganic hybrid polymer
Dear Leonid,...
that's a very good question....
At first a very quick answer,...you need a polymer structure which has a distinct interaction between its polymer chains as well as in combination with steric blockades by voluminous side groups.
I am very interested in following the next answers. The endless diversity proclaimed by Staudinger in 1922 never has been followed to find a polymer with highest melting point and thermal stability.
Time to initiate thinking about that.
With best regards
Michael
Dear all,
polyimides constitutes a classical family of high temperature melting polymers; If filled with a high heat capacity inorganic filler or reinforcement this behavior may be positively ameliorated. This attached file shed some light on this polymers and others. As it is clarified by Prof. M.. Heine, main chain stiffness is the most deciding element. Regards
Maybe organic-inorganic hybrids or ceramic precursor polymers can be used. But they will not be too flexible.
Dear Gyorgy,...
you are right... the endless diversity of polymers includes also the combination of organic and inorganic macromolecules with the option of highest temperature resistance. There are a few research groups working in that field... see also https://www.researchgate.net/profile/Guenter_Motz
With best regards
Michael
Dear Michael - I met him (Dr Motz) a few years ago at a conference in Hungary, their work is exciting. I am also in contact with a Hungarian firm, Polinvent Ltd. producing an interesting set of hybrid resins based on isocyanates and water glass that can also be combined with epoxies, vinyl esters etc. These resins provide a wide diversity of formulations. Some of these resins, if heated slowly produce a carbonized shell which is heat resistant to several hundreds of degrees, but they become relatively brittle. A few years ago I even tried to submit an EU project to develop further these resins but unfortunately we have not got money.
Dear all,
I just add a few parameters which should be taken into account:
High melting point means low creep and good geometric stability or a high enough modulus at high temperature. This is achived principally by strong polymer-polymer interactions, either physically (polar or ionic groups) or chemically (crosslinking - but this prevents melting). Adding inorganic filler helps - as already stated - by improving stiffness / modulus.
High temperature stability in terms of chemical stability (no decomposition, very slow or no oxidation) needs appropriate CHEMICAL STRUCTURES as is the case in typical high temperature polymers (PEI, PPSU, PEEK, etc): e.g. aromatic structure in the main polymer chain, a low hydrogen/carbon ratio, containing fluorine or silicone ...
So an approach could be the modifiaction of classical high temperature thermoplastics with a thermally reversible chemical or physical (ionic) crosslinking.
Dear Leonid,
Development of this materials is based on simply principle Tg=dH/dS. It is possible to increase temperature of glass transition when cohesion energy between macromolecular chain will be high together with low entropy (rigid chain). Polybenzimidazoles are most suitable for your request and they are commercially available but these are thermosets. I don't know thermoplastic polymer with short term resistance about 700°C, this would mean processing temperature about 800°C.
Dear Leonid,
Development of this materials is based on simply principle Tg=dH/dS. It is possible to increase temperature of glass transition when cohesion energy between macromolecular chain will be high together with low entropy (rigid chain). Polybenzimidazoles are most suitable for your request and they are commercially available but these are thermosets. I don't know thermoplastic polymer with short term resistance about 700°C, this would mean processing temperature about 800°C.
Of course: any Thermrearctive Aromatic Polyimide - has T-stability over 400-450.;
but it is not enough now
Leonid
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