When manufacturing PVC, resin is produced in an aqueous environment, so the addition of more water through the use of emulsions is not an issue. Emulsions are stable at temperatures as low as –30°C, and can be safely stored in most commercial freezers used for the storage of industrial chemicals. Low-molecular-weight alcohol or glycol is often added as an anti-freeze in the emulsion formulation to further prevent freezing.
While there was wide acceptance and use of emulsions in PVC production throughout Europe and Asia, the practice did not take off in the United States at the same time. There are three main reasons why:
- The cost to produce emulsions is slightly higher per unit of initiator when compared with solvent-based organic peroxides.
- There were no existing regulatory requirements serving as an impetus for manufacturers to make the move.
- The number of incidents associated with the unplanned decomposition of organic peroxides across the U.S. PVC industry was limited.
In short, PVC manufacturers had no strong reasons to explore adopting the use of organic peroxide emulsions. However, the reality has changed over the last two years.
A number of recent events led many users of organic peroxides to begin reevaluating the use and storage of these energetic products necessary for producing many polymer resins. For PVC producers, the choice was simple: Organic peroxide emulsions can be safely and successfully used as alternatives to the more sensitive solvent-based organic peroxides. And although emulsions cannot be used by all polymer resin producers to lower the inherent safety risk associated with organic peroxide initiators, less concentrated, better phlegmatized solvent-based organic peroxides may be able to provide some risk mitigation in these cases, as well.
Now that U.S. PVC manufacturers are starting to realize its advantages, the market for this technology is expected to grow significantly over the coming years. The PVC market will account for most of that growth, but scientists are already exploring other resin applications, such as acrylics, where similar technologies may be possible!
Paul Iacobucci is currently Commercial Manager for Organic Peroxides at Nouryon, and has worked in the chemical industry for more than 35 years. He has been an active member of the Organic Peroxide Producers’ Safety Division (OPPSD) of the Plastics Industry Association (previously SPI) and is an industry representative on the NFPA Technical Committee of Code 400 (Hazardous Materials). He has also been previously active in the American Institute of Chemical Engineers (AIChE).
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