Processing PVC and Acetal

This question just came
in from a medical molder…



We are extruding
flexible PVC and started injection molding Acetal in the same facility. On the
PVC die heads and downstream auxiliary equipment there is a white layer of
powdery build up on the metal. What is the cause of this?


My Response

The white layer of
buildup on the machines is most likely a result of a chemical reaction between
the formaldehyde gas and hydrochloric gas byproducts of your two processes. The
hydrocholoric gases that result from PVC processing will also attacking any
non-treated steal. When processing these two materials in the same facility
proper safety measures must be put in place to separate the two materials. To
help prevent the white buildup a larger ventilation system with separate exhausts
for each process could be put in place.


Additional Thoughts

It is dangerous to
process PVC and Acetal in the same facility and extreme care should be taken to
separate the two materials at all times. A high concentration of formaldehyde
and hydrochloric gas may be enough to cause an explosion in the facility. If
the PVC or Acetal were accidentally mislabeled, mishandled, and processed
together, it would cause an explosion!  



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