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Can Coatings: Technology Or Process?

April 1, 2013 | APPEARED IN VOLUME 91, ISSUE 13

The article about bisphenol A and its use in can coatings and adding it to California Proposition 65 has me wondering (C&EN, Feb. 11, page 24). Are there data showing the extractable levels of bisphenol A from the epoxy coating that measure above acceptable levels to cause a concern when extracted by the can contents and digested? No one wants to be exposed to harmful chemicals that are going to cause a problem in the human body over time.

Because bisphenol A is reacted with epichlorohydrin to produce the epoxy coating used in inner can coatings, is the reaction not going to completion under the proper curing conditions? Are the two components used to produce the epoxy resin not being measured out to the optimum levels to fully complete the cure mechanism and not leave residual bisphenol A available for extraction and digestion?

The chemical industry is constantly bombarded regarding “bad chemicals,” but is the real issue here the technology or how it is being processed in the field that is truly the one of concern?

Cosmo V. Sabatino
Pepperell, Mass.



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Em Bloom (April 11, 2013 5:07 PM)
As a chemist, I worked a few years in trace contamination studies. Most people do not realize there is always trace unreacted chemical ranging from parts per quadrillion to parts per thousand, regardless how complete the reaction is. Example: teflon leaches fluoride, HDPE leaches metals, PP leaches anions, etc. It usually depends more on how long the part is cleaned after production. Couple that with leaching from liquid not at pH 7 and you'll have more or less leachate. I do not know how much without testing, but it will always remain.

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