Wednesday, December 29, 2010

Purging Tip of the Week: #30

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 purging compound in the machine is brief, there’s no reason to shy away from a filled purging material unless:

  • There are narrow flow paths in the system that increase the risk of filler agglomeration and consequent blockage;
  • Highly polished production equipment surfaces (for exceptional end-product surface finishes) are susceptible to scratching or marring by an aggressive filler;
  • 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 you have a significant concern about one of the areas noted above.

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