Epoxy resins thermo-oxidation

The use of ACECs as modifiers for CECs makes it possible to preserve the desirable processing characteristics of epoxy resins and to improve the mechanical strength, elongation under load and heat resistance. The thermal stability of the crosslinked materials does not depend on the type of modifier. This statement concerns both the thermo oxidative aging in the isothermal and the dynamic conditions. 

It is well known that the epoxy-amine polymers have decreased thermal stability in comparison with the epoxy-anhydride polymers [3-5]. The investigation of the effects of the salts of manganese, nickel, chromium, and cerium on the thermal (in nitrogen) and thermo-oxidative (in air) degradation of the bisphenol A-based epoxy resins cured with triethylene tetramine indicated that the compounds of manganese, chromium, and cerium do not affect the thermal degradation of the polymers, but diminish their thermo-oxidative stability and lessen the breakdown temperature by 80-100 C. The nickel salts affect neither the thermal nor thermo-oxidative degradation of these epoxy polymers [252]. 

The flcune retardcuicy of all epoxy systems was enhcuiced by the incorporcition of POSS nano reinforcements (Table 3.8). This might possibly be due to the formation of oxidatively stable, nonpermeable surface char and a multilayered carbonaceous sflicate structure that acted as an insulator. Besides this, the better exfohation of POSS within the polymer matrices may also have accomited for an enhanced flame retardancy to epoxy resins. The effect of POSS towards flame retardmcy wcis more in the case of phosphorous- and siloxane-modified tetrafunctional epoxy systems them the sulphone and need epoxies, thereby supporting the results obtained from mechanical, thermo-mechanical and thermal studies as discussed earher. 

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