Quick Note on Safety with PVC & Acetal

For some reason we are encountering a large number of companies who’s employees are not familiar with extremely important safety concerns of running both PVC and Acetal (POM) in the same plant.


Heated PVC gives off hydrochloric acid while heated, this acid will erode most metal surfaces that are not stainless or plated with protective coatings like chrome. Acetal gives off formaldehyde which is also corrosive. While both PVC and Acetal can be dangerous by themselves, if these two gasses combine they cause a violent chain reaction which typically results in an explosion as well as a cloud of deadly hydrochloric acid. PVC, or polyvinyl chlorides, can never be processed in the same machine that has processed Acetal, also known as POM or Polyoxymethylene. Likewise, a machine that was used for molding Acetal cannot be used for molding PVC. Any combination of these two materials produces a deadly gas which can also cause an explosion. In fact, just a little bit of one exposed to the other can cause a chain reaction which can blow the hopper or end-cap off of the molding machine. Be aware that no purging compound or procedure exists that will allow you to safely process these two materials in the same molding machine.

Moving Forward:

Every company which molds both PVC and Acetal (POM) must have fool-proof procedures in place to ensure these two materials are never processed in the same molding machine, delivered in the same supply tubes, mixed in the same mixers, blended in the same blenders, ground in the same grinders, or dried in the same driers. It is also critical to ensure these materials are not processed in proximity of each other as the mixing of the gasses these two materials produce creates a very dangerous, corrosive, and potentially deadly hydrochloric gas.

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