Miscellaneous Compounding Ingredients

This section gives a brief description of other common compounding ingredients such as stearic acid and derivatives, resins, processing aids, and blowing agents. 

Stearic acid at levels of 0.5-1.0 pphr is recommended in CR compounds to improve processing and to reduce null sticking. Zinc stearate acts as an accelerator  

Resins such as coumarone resins are able to act as dispersants and tackifiers. Sometimes, reactive reinforcing phenolic resins are also used, in which case if the crosslinking component (e.g., hexamethylene tetramine or other formaldehyde donors) is used, it must be added in the second stage together with the accelerators. 

For some appUcations CR compounds must be adhered to textiles or metals. Bonding resins of the resorcinol type are normally used as internal bonding agents. Because of the scorching effect of resorcinol, modified grades, such as resorcinol diacetate, are recommended to preserve processing safety. 

There are no objections to the use of certain processing aids, of which there are many on the market. For appUcations and handling, the suppliers recommendations must be followed. In addition to stearic acid and commercial process aids, low-molecular weight polyethylene, waxes, and wax-like materials, and blends with other elastomers (e.g., BR) are commonly employed. 

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