Hydrocarbon-like polymers, formation

To achieve effective char formation in hydrocarbon-like polymers, we are beginning to see combinations of phosphorus compounds with other molecules, and we are beginning to see phosphorus containing molecules combining structural elements that will induce char formation. Several recent examples of the blend approach which is really an extension of FR technology... 

Metal dialkyl dithiocarbamates inhibit the oxidation of hydrocarbons and polymers [25,28,30,76 79]. Like metal dithiophosphates, they are reactive toward hydroperoxides. At room temperature, the reactions of metal dialkyl dithiocarbamates with hydroperoxides occur with an induction period, during which the reaction products are formed that catalyze the breakdown of hydroperoxide [78]. At higher temperatures, the reaction is bimolecular and occurs with the rate v = k[ROOH][inhibitor]. The reaction of hydroperoxide with dialkyl dithiocarbamate is accompanied by the formation of radicals [30,76,78]. The bulk yield of radicals in the reaction of nickel diethyl dithiocarbamate with cumyl hydroperoxide is 0.2 at... 

The irradiation environment plays an important role in the evolution of polymer stability. While unsaturated hydrocarbon like acetylene [61] or divinyl benzene [62] is present in the material surrounding and provides radicals for the formation of intermolecular bridges, oxidative atmosphere, oxygen or air, promotes oxidation as the result of diffusion inside the polymer matrix. The distribution profile for carbonyl products that generated during irradiation takes a parabolic form [63]. The source of radicals may be one of the components of blends, which presents a lower stability. This case can be illustrated by various blends, EPDM/PP [64], EPDN-NR [65]. These polymer mixture show the maximum level of crosslinking at about 120-150 kGy. 

A. von Keudell Formation of polymer-like hydrocarbon films from beams of methyl radicals and atomic hydrogen. Thin Solid Films 402, 1 (2002)... 

However, the previous reaction does not explain the formation of water, although for about 90% of the molecules of CO2, a corresponding molecule of water is found in the pyrolysate (some water in the pyrolysate may come from the adsorbed water on the polymer). Also, the lack of long chain hydrocarbons in the pyrolysate and the presence of aromatic compounds and of some ketones indicate that the decarboxylation process has a different mechanism. One likely possibility is the reaction involving a cyclic mechanism for the elimination of CO2 and subsequently of H2O, as shown below ... 

Gum formation. Heating of paraffinic hydrocarbon mixtures found in jet fuels, gas oils and similar products may result in the precipitation of gum-like material. A sequence of events has been proposed by Taylor [1967, 1968]. Autoxidation forms a soluble oxidation product, with further oxidation to an insoluble polymer. The polymer may be formed on the wall or transported as particles to the wall. 

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