Pyrolysis activation energy, polymer

Polymer Structure Tem- perature of pyrolysis Activation energy kJ/mole Monomer yield %... 

Table 9. Heats of Gasification, Pyrolysis Activation Energy, Char Yield, as well as Calculated and Measured Molecular Weights of Decomposition Products for Some Polymers...

Thermogravimetric analysis (TGA) has often been used to determine pyrolysis rates and activation energies (Ea). The technique is relatively fast, simple and convenient, and many experimental variables can be quickly examined. However for cellulose, as with most polymers, the kinetics of mass loss can be extremely complex (8 ) and isothermal experiments are often needed to separate and identify temperature effects (9. Also, the rate of mass loss should not be assumed to be related to the pyrolysis kinetic rate ( 6 ) since multiple competing reactions which result in different mass losses occur. Finally, kinetic rate values obtained from TGA can be dependent on the technique used to analyze the data. 

One of the best-known thermal reactions of fluorine compounds is the pyrolysis of chlorodifluoromethane to tetrafluoroethylene as used in the production of Teflon polymer. This reaction was described by Park et in 1947, and Nor-ton" in 1957 reported an activation energy of 49 kcal.mole for the decomposition over silica at 425-525 °C. More recently, Gozzo and Patrick have made a kinetic study of the process using a helium flow system at 670-750 °C with a surface conditioned platinum tubular reactor. HCl is found to retard the raction and the following mechanism has been proposed... 

The activation energy values suggest that scission of N-H bonds seems to be a predominant reaction during the pyrolysis process. This reaction, according to the scheme (1-3), leads to the formation of a highly corssllnked inorganic structure in the polymer film. 

Because of the lower activation energy of their initiation reactions, the rising concentration of double bonds inside the polymer enhances the radical concentration and favours the pyrolysis process. This radical concentration is then used to evaluate the rate of formation and disappearance of all the species in the system. Thus, the production of the alkene Oj is simply expressed as... 

Rychly and Pavlinec [38] put particular emphasis on the effect of fillers on the activation energy for polymer pyrolysis determined in air. Movement of this value... 

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