Effect of MgO activity value on neoprene cable compound

In the standard formula of general chloroprene rubber (ldj-120, equivalent to gn-a in the United States), active magnesium oxide (iodine adsorption value is more than 80 mg I2 / g) is specified to be used, and the special light special grade magnesium oxide (iodine adsorption value is about 40) specified in the previous standard is modified. In the pure rubber formula, the effect is greater without accelerator NA-22, but in the non sulfur regulated neoprene rubber (ldj-230 type, equivalent to U.S. W type), the effect of activity (iodine value) is smaller, especially for the rubber containing carbon black.

1. The iodine value of MgO has an effect on the Mooney scorch of 120 chloroprene rubber. When there is no accelerator NA-22 in the formula, the effect is relatively small.

2. In addition to carbon black, accelerator NA-22 is often used to adjust the curing speed and degree of 120 polychloroprene rubber used in the wire and cable industry. According to the properties of all aspects, it is appropriate to select medium active special magnesium oxide for rubber (the iodine adsorption value measured by mechanical vibration method is more than 40, and the iodine adsorption value measured by hand vibration method is about 30). At the same time, the influence of magnesium oxide content, burning loss and other factors on the properties of chloroprene rubber should be considered. Magnesium oxide with very low iodine adsorption value is not suitable for the formula.

3. In the formulation of pure non sulfur modified polychloroprene rubber, the difference between high activity and medium activity, medium activity and low activity is not significant, but only between high activity and low activity.

4. In the formulation of non sulfur carbon black chloroprene rubber, the activity of MgO has little effect on Mooney scorch.

5. The longer the high activity magnesium oxide is exposed in the air, the larger the decrease of iodine adsorption value is. It is difficult to ensure that the iodine value of the high activity magnesium oxide does not decrease in the actual production. Moreover, carbon black and accelerator NA-22 are often used in the production formula. In this case, it is not significant to use high active MgO, but if we choose low active MgO, the scorch time will be shortened obviously. Finally, it is concluded that the medium active magnesium oxide for rubber should be selected.