"nPB" is a chemical abbreviation for one member of the family of brominated solvents, also known as normal-Propyl Bromide or n-Propyl Bromide. These solvents are manufactured by many companies around the world and are an intriguing choice for many customers.

First, there's no doubt about it: nPB is a powerful degreaser with very familiar handling, similar to 1,1,1-trichloroethane that was so popular thirty years ago. Solvents based on nPB will boil at about 71° C/160° F so it can be used to remove waxy residues that other solvents cannot touch. It is very aggressive so cleaning is fast and easy. Perhaps most attractively, nPB is very inexpensive -- typically $1,500 per drum in the U.S. This makes it very competitive in the market. MicroCare markets a family of nPB-based cleaners called "Bromothane™" so nobody knows better than MicroCare the good points and the less attractive features of this product.

First, while it is strong and inexpensive nPB is not perfect. It took four years for the U.S. E.P.A. to approve nPB as a solvent, primarily based on concerns about the environmental and safety. This contrasts sharply with the HFC-365 used in Vertrel^®, which was approved in 90 days.

Another environmental factor is that nPB is a volatile organic compound (VOC). This means it has the potential to contribute to low-level smog and will be unsuitable for use in localities which have strict VOC rules, such as southern California. Interestingly, some people also have claimed nPB is an ozone-depleting solvent. Recent analyses suggest this is not true. The nPB molecule has an atmospheric life of only 11 to 17 days. With such a short atmospheric life, the molecule does not have enough time to migrate to the stratosphere to cause a problem.

Toxicity is another issue for many people looking at nPB. While some nPB producers are claiming a 100 ppm threshold limit value is proper for nPB, ACGIH issued on Jan. 30, 2005 a final report which set the TLV at 10 ppm. Because of this relatively low value, brominated solvents only will be safe to use in tightly-engineered cleaning machines which limit worker exposure to the solvent fumes, such as vapor degreaser systems designed under the NESHAP regulations. MicroCare strongly recommends against using any nPB-based solvent in dipping, wiping or aerosol applications. As an additional safety precaution, MicroCare further recommends annual testing in the workplacefor exposures to fumes.

Another problem is the aggressive nature of the cleaner -- the very attribute that makes it such a good cleaner! -- can require complicated work-arounds when working with softer plastics and elastomers. This cleaner is definitely not plastic-safe.

But the big problem is that in a poorly-monitored system nPB can turn acidic.

In the old days, the old chlorinated solvents had a tendency to turn acid in the presence of water. The brominated solvents do exactly the same thing. In fact, in demo machines which have been running nPB-based cleaners, MicroCare has observed significant rust and corrosion inside the system after just a few weeks of use when the systems were not maintained properly.

Chemically speaking, the solvent can hydrolyze with water to form acidic compounds. Sometimes the water comes from a drying process, but most often the water comes as a by-product of condensation on the cooling coils. In a busy machine, this can be a real problem. So users of nPB will have to monitor every machine on a weekly or even daily basis with an "acid acceptance test" to confirm that the solvent is still safe and effective. None of these issues are insurmountable; they just take time and add slightly to the operating costs.

If all of this is not enough, nPB has a distinct and pungent odor which many users find annoying. The aroma is very pervasive but desensitizing. In a poorly maintained degreaser, the smell often is noticeable even far from the vapor degreaser. So here's a good rule of thumb: if you can smell the solvent in the factory, you are not using the solvent properly and you will probably fail the 10 ppm air monitoring requirement. In this case, immediate remedial action is required. Call MicroCare right away for further information and guidance.

Contrast these complexities with the ease of using Vertrel^®. Vertrel^® is SNAP-approved without restrictions. It is very safe for users, so the regulations allow Vertrel^® to be used in traditional non-NESHAP vapor degreasers and even in aerosol products. Vertrel^® has almost no aroma and boils at low, energy-conserving temperatures. All of these factors combine to make Vertrel^® the right choice for almost every precision cleaning application.

(By the way, everybody asks about the Montreal Protocol, VOCs and global warming. The Montreal Protocol is all about ozone-depleting substances and does not address either VOCs or global warming. For more details about the ozone depletion issue, global warming and VOCs, you can visit the United Nations web site, the Earthwatch web site, the GreenPeace web site, and a new location in the UK called OzoneDepletion.co.uk that has very good info without the polemics found on GreenPeace.)

 

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