Purging Pointers from Novachem

Purging with "Scrubbing" Ingredients
Many mechanical purging compounds increase effectiveness by incorporating fillers or abrasive resins. These ingredients cover a range from quite gentle "polishing" agents to quite aggressive scouring materials. Because the residence time of the purge in the machine is brief, there's no reason to shy away from a filled purging material unless (1) there are narrow flow paths in the system that increase the risk of filler agglomeration and consequent blockage; or (2) highly polished production equipment surfaces (for exceptional end-product surface finishes) are susceptible to scratching or marring by an aggressive filler; or (3) the next production resin is of such low viscosity that it would have trouble displacing a stiffer purging material. Therefore, go ahead and use a purging material that contains a "scrubbing" ingredient unless there is a significant concern about one of the areas noted above.