The compound used for calendering should have good rolling property, fluidity, resistance to burning and low shrinkage. When designing the formula, a corresponding balance should be achieved between the rolling property and the fluidity and shrinkage.
(1)The influence of raw rubber natural rubber molecular chain flexibility is good, plastic state fluidity is good, shrinkage is small, and roll covering is good, is a better rolling rubber. Butadiene rubber is followed by neoprene rubber, although the rolling property is good, but the thermal sensitivity is large, easy to produce sticky rolls. The molecular chain flexibility of styrene butadiene rubber and nitrile rubber is poor, the fluidity is poor, the shrinkage is large, and the compression ductility is not good enough.
(2) The effect of the filler: A certain amount of filler should be added to the general calendering glue. The effect of adding filler is to reduce the elastic deformation of rubber molecular chain and make it conducive to calendering operation. General fillers, such as carbon black (characterized by high structure carbon black), white carbon black, calcium carbonate, etc., are very suitable. Clay is best not used because of its tendency to make the glue stick to the roller. In addition, the addition of refined recycled rubber also has the effect of increasing fluidity and reducing rolling shrinkage.
(3) The influence of the softener the calendering compound must have a large enough plasticity (low enough viscosity). The addition of softener can reduce the viscosity of the compound, increase the fluidity and reduce the shrinkage, and good results can be obtained by adding the commonly used softener, but the softener should be selected according to the different requirements of the calendering compound.
(4) The effect of the vulcanization system The calendering operation is usually carried out at a higher temperature (90 ~ 110℃), and the selection of the vulcanization system should first consider that it is not easy to produce coke. Generally, the Mooney burning time of calendering compound should be controlled above 20 ~ 25min.
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