Acta Chimica 43. (1965)
2. szám - Hardy Gyula–Nyitray K.–Kovács G.–Fedorova N.: Investigations in the field of radiation-induced solid state polymerization, I.
INVESTIGATIONS IN THE FIELD OF RADIATION-INDUCED SOLID STATE POLYMERIZATION, I. CETYL METHACRYLATE Gy. Hardy, K. Nyitray, G. Kovács and N. Fedorova (Research Institute for the Plastics Industry, Budapest) Received March 9, 1963 A lot of experimental work is to be done in the field of radiation-initiated solid state polymerization until a general theory is established. Some generalizations published in literature [1 — 5] can be considered as reviews rather than theories of general validity. T he effect of crystal structure on polymerization kinetics and on polymer structure is surely one of the most interesting problems in radiation-induced solid state polymerization. As shown by Chapiro [6], no polymerization can be observed in pure methyl methacrylate when irradiated in the solid state. If, however, paraffin oil is added, the monomer does polymerize fairly well. Cetyl methacrylate (m. p. 15°) having a long paraffin chain, can be considered in some respects as a 1 : 1 mixture of methyl methacrylate and paraffin oil within a single molecule. This is why cetyl methacrylate was chosen as a model substance for the present investigations. Experimental Cetyl methacrylate (product of Nitrokémia Factory, Fűzfő, Hungary) was distilled three times. The fraction boiling at 178°C at 2 Torr and having the refractive index nf> = = 1.4498 was used as the monomer. Polymerization was carried out in glass ampoules containing 2 g material. Prior to sealing, the samples were frozen; the ampoules were evacuated and filled with oxygen-free nitrogen. Then the monomer was allowed to melt. This operation was repeated three times. The samples in the sealed ampoules were irradiated, using a panoramically built-up 500 curie radiation source of e0Co. After the polymerization had been completed, the ampoules were opened immediately, and their contents dissolved in gasoline. The polymer was precipitated by adding the polymer dropwise into acetone, using a vibratory stirrer. After filtering, the polymer was dried under reduced pressure at 25° to constant weight. The molecular weight determinations were carried out in n-heptane solutions of a concentration of 0.1 to 0.6 g/100 ml at 25°, using the formula fa] = 3.51 • 10-1 • M°'5e [7] Differential thermoanalytical measurements were made with the aid of copper-constantan thermocouples. The thermocouples were placed in two ampoules, switched against each other, and the temperature difference between them was recorded by a galvanometer (Fig. 1). One of the ampoules contained the sample of cetyl methacrylate to be tested while the other, under otherwise identical conditions, cetyl alcohol as a reference substance. Acta Chim. Hung. Tomus 43. 1965