Abstract
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.
