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Characterization of polymer mixtures presents a challenging problem and various techniques have been used for this purpose. One of the simpler methods is pyrolysis in an inert atmosphere followed by direct gas chromatographic analysis of the products. Precise control of the various experimental parameters makes it possible to obtain both qualitative and quantitative data on the polymeric constituents.
The gas chromatographic requirement for an instantaneous injection dictates that the size of the sample be small, the temperature rise should be fast, and the pyrolysis time be short. The Curie-point pyrolysis method comes close to meeting most of these requirements.
Characteristic gaseous products suitable for quantitation were obtained from polyisoprene, styrene-butadiene rubber, polybutadiene, ethylene-propylene-terpolymer rubber, and chlorobutyl rubber. The gas chromatographic conditions were designed to analyze the products which had a very wide range of volatilities. The flame ionization detection offered ample sensitivity for the detection of very small amounts of materials.
The use of absolute peak areas per unit weight of the sample resulted in simpler nonlogarithmic relationships which are suitable for automatic computer calculations.
Certain copolymers of unknown monomer ratio cannot be quantitated in the presence of other polymers containing the same monomeric unit. Monomer ratios in copolymers can be determined in other cases. When mixtures of known types of polymers are used their composition can be determined with a standard deviation of 1.5 percent.
This technique is recommended as a routine analytical method.
elastomers, gas chromatography, pyrolysis, analyzing, test equipment, thermal decomposition
Senior research chemist, The Goodyear Tire & Rubber Company, Akron, Ohio