The authors measured the energy of activation for ozone cracking of vulcanized rubber (E_c) Its values, depending on the fillers used differ, increasing with larger contents of fillers but decreasing abruptly over a filler content exceeding a certain limit. These effects of fillers were discussed.
Ozone craching occurs in the following two steps;
(1) Ozone permeates into rubber
(2) Subsequently ozonisation and scission at double bonds of molecules occurs, followed by degradation and cracking of mass.
The energy of activation for ozonization and scission (E_γ) of crude rubber is 23 Kcal/mole and E_c is above 5 Kcal/mole Therefore the value of E_c is almost equal to the energy of activation for diffusion of ozone into rubber Ed :

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The author tried to make those reagents, which react with mercaptan radical (-SH), react with organic polysulphides. Out of many reagents used for reactions for quantitative and qualitative analyses of mercaptan radicals, the author picked up doctor solution, silve nitrate, copper acetate and lead acetate, and made them react with benzyl mono-, di-, tri-and tetra-sulphides, tolyl mono-, di-, tri-and tetra-sulphides, thiodiglycolic acid, and dithioglycolic acid.
Doctor solution did not react with mono and disulphides, but reacts with di-, tri-and tetrasulphides and generated lead sulphide. When sulphur as simple substance was reacted with doctor solution under heating, production of lead sulphide was observed. Silver nitrate did not react with mono, di-sulphides, but, when heated, desulphurize tri-and tetrasulphides and produced silver sulphide and organt disulphide. The author made it sure that lead acetate and copper acetate do not react, even when heated, with mono-, di-, tri-and tetra sulphides. Further the author discussed these reactions and the reactivity of organic polysulphides.

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In order to make clear the plasticization characteristics by mastication of synthetic rubber, the authors masticated at 30°C, 80°Cand 130°C the following types of rubber :
Synthetic-GR-S 1001
GR-S 1500
GR-I 15
Hycar OR-25
Neoprene Type W
Natural-Smoked Sheet
Pale Crepe
Samples were taken 6 times during the mastication time of one hour at a 10 minutes' interval, and on each sample were determined the Goodrich plasticity, gelflaction, viscosity of the diluted solution and plastic flow. Comaparison was also made between the several types of synthetic rubber used and natural rubber from the joint of view of the behoviour when plasticised. The authors think it probable that when natural rubber is masticated, the chain of rubber molecules is cut both by the mechanical action and the reaction of oxyzen and thus mastisation goes on smoothly, while the cutting of the molecular chain does not occur easily in synthetic rubbers, and their mastication is due to disaggregation or loosening of entanglement of the molecular chain, breaking of branches and collapse of linking bridges. The broken pieces of synthetic rubber molecules are unstable in each type, and gel is formed in some types, depending upon the mastication conditions. Thus, in order to masticate synthetic rubber with good result, acceleration of disaggregation or loosening of antanglement of the molecular chain, stabilisation of broken pieces of the molecular chain and cutting of the molecular chain by chemical reaction must be taken into consideration.

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[in Japanese]

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