It is shown that there exists a difference in the electron spin resonance spectra of commercial‐grade and laboratory‐purified samples of polymethyl methacrylate and polyethyl methacrylate. This difference arises because of the presence of monomer. The spectra of the pure polymers show only partial resolution, while the spectra of samples containing monomer have the nine‐line pattern as previously reported.

A study has been made of the effect of gamma irradiation on the production of free radicals in poly(butyl methacrylates). A mechanism of radiation attack on the polymers is proposed. Free‐radical measurements and the determination of the products of irradiation have been used in establishing this mechanism. The effects of configuration of the ester chain on radiation susceptibility are discussed.

A method has been developed for the estimation of the unsaturation of butyl rubber by ozonation in selected solvents. Under a given set of conditions the ozonation method is reproducible to within 7 per cent and conceivably could be improved by further refinement. The unsaturation of a butyl rubber can be estimated in about 10 minutes when using ozonated oxygen and in about 15 minutes when using ozonated air.

No abstract