応力緩和測定による加硫ゴムの耐オゾン性評価

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This paper described the stress relaxation measurements as a quantitative method to evaluate the ozone deterioration of SBR vulcanizates containing several commercial antiozonants under static condition.The effects of thickness and width of specimen, strain and ozone concentration on the stress relaxation of rubber due to ozone attack were studied. It was found that the rate of the stress relaxation of rubber band 1mm×10mm×60mm in ozone exposuring is linearly related to time t in the extent of 10%-100% elongation and shown by the following equation.R=-Kt+b.Where; R is the retention of stress, K is the rate constant of stress decay (the slope of the straight line) in ozone deterioration and b is a constant.They depend on strain, ozone concentration and amounts of antiozonants.It is thus possible to represent the ozone resistance of SBR vulcanizates by three parameters K, b and RH, which is time to 50% retention of stress. It seems that b means the existence of the induction period of first cracking, when the value of b is more than 100.A new method of visual assessment of the deterioration of rubber due to ozone attack was also proposed and the good corelation between the stress relaxation assessment and the visual one was obtained. The stress relaxation method, however, provides no information on the cracking pattern and should be used in co-junction with visual evaluation.The equipments used in this experiment are Toyorika OMS-2 ozone weather-meter for ozone chamber, Toyosei_??_i Relaxometer for measuring of the stress of rubber specimenout of the ozone chamber and specimen holdersespecially deviced to keep specimen definite elongation and measure their stress with the relaxometer.In the analysis of the ozone concentra ion, the coulombmetry was used. The outdoor exposure test was briefly discussed with this stress elaxation method.
日本ゴム協会の論文

応力緩和測定による加硫ゴムの耐オゾン性評価

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