Poly thermooxidation

A typical synthetic route to the incorporation of pendent carboranyl units into a polymer chain is shown in scheme 3. Poly(o-carboranyl-organo-siloxane)s have been successfully prepared through hydrolysis of dimethyldichlorosilane in the presence of carboranedichloromethylsilane. The polymer has some of the elastomeric characteristics of the parent poly(siloxane) however, the thermal-oxidative cleavage of the o-carboranyl pendent group is reported to occurat lower temperatures than that for the thermooxidative cleavage of Si—O and Si—C bonds.10 Thermal studies have... 

It has been determined from X-ray diffraction measurements that polycarbonate containing Bisphenol AF moiety are all amorphous.6 The (Tg) of poly(carbonate)s increases with an increase in hexafluoroisopropylidene unit from 149°C for Bisphenol A poly(carbonate) (3) to 169°C for Bisphenol AF poly(carbonate) (2) (Table 9.3).6 Thermooxidative stability is also improved by the introduction of fluorine atoms into the isopropylidene units. The 10% weight-loss temperature (DT10) increases from 429 to 460°C and the residual weight (RW) at 500°C goes from 37 to 57% by perfluorination of the isopropylidene units. 

The thermooxidative stability is improved by increasing the hexafluoroiso-propylidene unit content.12 The DTi0 in air is raised from 363°C for Bisphenol A poly(formal) (6) to 398°C for Bisphenol AF poly(formal) (7), and the RW at 500°C is increased from 48 to 73%.12... 

Thermooxidative stability of the fluorine-containing poly(ether ketone) (11) and poly(sulfide ketone) (13) from 15 is very high. The 5% weight-loss temperatures (DT5) are 391 and 436°C for poly(ether ketone) and poly(sulfide ketone) analogues having no fluorine atoms, whereas those of poly(ether ketone) (11) and poly(sulfide ketone) (13) are higher than 500°C. 

None of the poly(azomethine)s show glass transition, and they are amorphous irrespective of the presence or absence of fluorine atoms20 All the poly(azomethine)s are thermooxidatively stable at temperatures as high as 400°C. Hexafluoroisopropylidene-unit-containing poly(azomethine)s are more stable to thermooxidation than those having no fluorine atom (Table 9.9). This is expected because the methyl group is more susceptible to oxidation than aromatic rings. 

Aromatic poly(benzothiazole)s are thermally and thermooxidatively stable and have outstanding chemical resistance and third-order nonlinear optical susceptibility. Aromatic poly(benzothiazole)s can be spun into highly-oriented ultrahigh strength and ultrahigh modulus fibers. However, this type of polymer is insoluble in most organic solvents. Therefore, hexafluoroisopropylidene units are introduced in the polymer backbone to obtain soluble or processable aromatic poly(benzothiazole)s. 

Schuster, M., Kreuer, K. D., Anderson, H. T. and Maier, J. 2007. Sulfonated poly(phenylene sulfone) polymers as hydrolytically and thermooxidatively stable proton conductors. Macromolecules 40 598-607. 

Because of its extended polyconjugated framework, polymer (210) exhibits semiconducting properties both by itself and in the presence of additives. Perhaps a more remarkable property, however, is that polymer (210) does not burn when exposed to a flame. Thus, by employing this thermooxidative reaction, woven or knitted poly(acrylonitrile) fibers can be transformed into fire-proof materials. Polymer (210) can be pyrolyzed still further at temperatures generally in excess of 1000 °C to expel all heteroatoms and generate carbonized or graphitized fibers. These fibers find application where an inert, extremely high temperature, e.g. up to 3000 °C, material is required. 

Flexible and oxidatively stable thermosets were prepared by thermally curing linear poly(silarylene-siloxane-acetylene) elastomers at up to 450°C. Thermooxidative weight loss of 3.69% to 7.69% was observed for these crosslinked inorganic-organic hybrid polymers when isothermed at 350°C under air flow. 

The cured or fully imidized polyimide, unlike the poly(amic acid), is insoluble and infusible with high thermooxidative stability and good electrical-insulation properties. Thermoplastic polyimides that can be melt processed at high temperatures or cast in solution are now also available. Through an appropriate choice of the aromatic diamine, phenyl or alkyl pendant groups or main-chain aromatic polyether linkages can be introduced into the polymer. The resulting polyimides are soluble in relatively nonpolar solvents. 

Beside inhibiting thermooxidative ageing, phosphorus containing additives increase radiation resistance of polyimides and poly(alkyl terephthalates) the rate of evolution of the aromatic ring radiation degradation product - CH4 reduces two-fold. 

TPA amide is formed by thermo-oxidation in melt and at low-temperature solid-phase oxidation. Light yellow crystals of TPA amide and TPA mixture occur and accumulate on the surface of mould samples during accelerated heat ageing at temperatures of 150-200 °C. TPA is a typical product of hydrolysis by macrochain ends. From our point of view, TPA amide product is of greater interest. Recall that analogous products (relative to polymer structure) were already observed in investigation of thermo-oxidative transformations of other APH. For example, pyromellite diimide, was identified in thermooxidation of PAI [7, 21] and classical polyimide Capton , and 2,2 -(l,4-phenylene)-bis-(phenylpyrazine), is formed by poly(phenylquinoxaline) ageing [7]. 

Kozlov, G. V. Shustov, G. B. Zaikov, G. E. Burmistr, M. V. Korenyako V. A. The influence of polymer melt structure on chemical mechanisms of poly ary lateary lene-sulfonoxide melt thermooxidative degradation. Problems of Chemistry and Chemical Technology, 2002(3), 67-72. 

The thermooxidative degradation and SiOx film formation of poly(vinyl imidazole-co-vinyl trimethoxysilane) on copper was investigated. Thermal degradation of the copolymer was catalysed by copper in the film and at the substrate surface. Copper in the copolymer film contributed to the formation of a copper-containing SiOx film during thermal degradation. Copper oxides in the film interacted with the SiOx film to form a copper-rich phase near the film defects and cracks (142). 

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