Silicones lubricating action

Since the PEGs have excellent solubility in water, they can be introduced to the reaction mixture as a concentrated solution in the quantity of water required, preferably before the reaction [98]. The lubricating action of the PEG obviates the need for special lubrication of the metering pump. PEGs are compatible with the conventional activator mixture, but the silicone commonly added must be pumped and metered separately. 

Silicone fluid is available in a wide range of viscosities. The lower the viscosity, the more fluid the additive is, and the quicker it will migrate to the surface and provide lubrication. This is particularly important in wear applications that require numerous start and stop actions. However, if the additive s viscosity is too low, the silicone can vaporize during processing, or migrate too quickly from the molded part. 

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