Most of the Vertrel^® blends are azeotropes, and that's important because it lowers your costs, boosts cleaning effectivness and enhances worker safety. In the chemical world, these are all considered really good things to do.

So the next question you're going to ask is, how does an azeotrope do that? Good question. For the answer, we have to go back to Chemistry 101.

First, an azeotrope is best described as a constant boiling blend. To be an azeotrope, the material has to be a mixture or a blend of at least two different elements or compounds. For example, neat HFC-43-10mee is not an azeotrope because there's nothing else in it but molecules of HFC-43-10mee. Vertrel^® XP is a mixture of MFC-43-10mee and isopropyl alcohol. So Vertrel^® XP could be an azeotrope (and is, as we will explain in a minute).

Now let's consider the boiling point of these materials.

The boiling point of HFC-43-10mee is about 50° C/130° F. But mix HFC-43-10 with a small but precise amount of methanol and the boiling temperature suudenly drops to 48° C/118° F. This is very odd and unexpected. The two chemicals are still separate and distinct in the mixture, but they are working together in a useful manner to lower their combined boiling point. When we boil some of this mixture in a beaker the two constituents will boil off at the same rate.

Let's supposed the mixture we are testing is 97% HFC and 3% alcohol. If we measured the fumes coming off the boiling liquid, we would be pleased to notice that the mixture of fumes also was at the same 97:3 mixture. When we chill those fumes and reliquify the material, it will have the same 97:3 mixture. In fact, no matter what we do the the mixture it always stays at the 97:3 proportions. This means we have created an azeotrope.

There is a bit of magic to making azeotropes. Not all liquids form azeotropes because the density, boiling point and surface tension all has to be exactly right.

Azeotropes are cool. Azeotropic behavior allows DuPont's clever engineers to deliver the benefits of a mixture with the convenient handling and storage of a single compound. It's like getting two chemicals out of one drum.

For example, azeotropes are very easy to distill and recover. If the solvent in a vapor degreaser acts as an azeotrope then the solvent can be boiled away and distilled while the contamination -- fluxes, oils, water, belly-button lint and such -- stay "trapped" in the liquid at the bottom of the machine. In effect, using azeotropic solvents allows us to trap and concentrate the contamination by distillation instead of using filters and membranes and such.

Another important benefit of an azeotrope is the unexpected ability to mix flammable and nonflammable ingredients to produce a stable nonflammable mixture. This is an amazing chemical phonomenon. Imagine mixing flammable products -- like alcohol -- into Vertrel^® XF and yet still be retain the convenient and safe handling characteristics of a nonflammable chemical. This is a big boost for safety!

Lastly, azeotropes permit the "tweaking" of a blend to obtain unique physical properties which makes the blends useful across a broad range of applications. For example, HFC-43-10mee is a very mild cleaner. But add some other ingredients in azeotropic proportions, and DuPont can make Vertrel^® into a blend that is almost as strong as methylene chloride, or as safe as Freon^®, or almost as cheap as HCFC-141b. In other words, azeotropes allow DuPont to customize Vertrel^® to fit almost any application or budget. The possibilities are almost limitless.

Here's a quick summary of the benefits of an azeotropic solvent:

Advantages of Vertrel® Azeotropic Solvents

Safety: First and foremost, all of the Vertrel^® solvents are nonflammable. This makes cleaning processes simpler, safer and more reliable by an order of magnitude.

Easy Operation: Manufacturing personnel deal with one solvent instead of a solvating agent and rinse agent. A single azeotropic solvent eliminates the need to monitor the ratio of solvating agent and rinse agent.

Easy Monitoring: Monitoring the contamination level in Vertrel^® azeotropic solvents is much easier than determining the soil level in a solvat-ing agent. Most manufacturing companies do not have the laboratory capability to determine the soil level in the solvating agent so they prema-turely discard the solvating agent, to preserve quality production. This discarding of the solvating agent results in greater solvent consumption.

Higher Soil-Loading Capability: Azeotropic solvents have higher soil-loading capability, which allows the solvent to be used longer and thus reduces solvent purchases.

Faster Cleaning: Azeotropic solvents clean much faster. This can reduce the cleaning cycle time by as much as 75%, increase productivity, and eliminate production bottlenecks involving the cleaning operation.

Minimal Odor: Vertrel^® azeotropic solvents have minimal odor, which eliminates workplace odor, employee complaints, and residual odor left behind on the cleaned parts.

Lower Constant Temperatures: Vertrel^® azeotropic solvent cleaning systems operate at lower constant temperatures, which provides greater compatibility and reduces energy costs. In co-solvent systems, the operating temperature can fluctuate dramatically as the ratio between the solvating agent and rinse agent changes.

Less Expensive: Both solvent and energy costs are lower with Vertrel^® azeotropic solvent systems. Azeotropic solvents are normally less expensive than the combined costs of two sol-vents used in a co-solvent process. Less azeotropic solvent is consumed because it has higher soil loading capability and is reclaimable by distillation. Significant solvent loss occurs in a co-solvent process when the agent is added to an operating system because of the two vastly different boiling points.

Versatile Equipment Use: Single-sump vapor degreasers can be used with Vertrel^® azeotropic solvents; boil-sump immersion is optional.

One Supplier: Vertrel^® azeotropic solvents are available in Canada, the U.S. and Mexico from one supplier: Micro Care Marketing Services.

Sadly, not all azeotropes are created equal. To a finicky chemist, a perfect "true" azeotrope only exists at a single temperature and specific pressure where the azeotropic behavior is observed. But DuPont has discovered over the past twenty years that "close" can be good enough. Many products are successfully marketed today which are not "perfect azeotropes" but near-azeotropes. These cleaners are so close to being azeotropes that they exhibit stable azeotropic behavior. For example, many near-azeotropes can be repeatedly evaporated, condensed, and recycled without changing the blend's composition or other properties. Even though it is technically just a mixture of different chemicals and does not meet the exact technical description of an azeotrope, a near-azeotropic solvent behaves as if it were a single pure component solvent rather than a solvent mixture.

Examples of near-azeotropes are some of the "Vertrel^® C" series ternary azeotropes from DuPont. The C-series of solvents are not perfect azeotropes in the strictest definition of the word, but offer azeotrope-like stability and can deliver the performance, safety and time-saving convenience of single-solvent operations under almost all conditions. These products have been thoroughly tested, again and again, by DuPont. They are so close to being true azeotropes they can be used without problems in any application requiring azeotropic behavior, such as vapor degreasing.

Three special notes: A few of the Vertrel^® products, such as Vertrel^® XSi, are simple blends, not azeotropes nor even near-azeotropes. This products have special handling requirements as listed on their product specifications. There's another twist to the handling issue, and it comes from the requirement of an azeotrope to operate at a specific pressure. Some companies today are using low-emission vacuum systems to minimize their consumption of solvents. Vacuum systems obviously lower the pressure in the system to an extreme degree, which can destabilize an near-azeotrope. For maximum safety, users of these vacuum systems must stick with only the pure, true azeotropes.

Lastly, sometimes there is no single solvent or azeotrope which is sufficiently strong to get the job done. In this case, some customers switch to using a co-solvent system. A co-solvent system uses two solvents -- one aggressive cleaning solvent, and one milder rinsing solvent -- to remove the most difficult soils.

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