A solvent is nothing more than a chemical composition or compound that can dissolve another chemical compound. For example, one of the most ubiquitous solvents available is common water. Long recognized as the “universal solvent,” water in its deionized form (all minerals and ions removed) can be an extremely aggressive solvent all by itself but is generally mixed with other compounds such as surfactants to maximize surface wetting.
Solvents can generally be divided into specific families:
Inorganic (acidic & alkaline)
Organic (hydrocarbon-based, chlorinated, fluorinated & organic acids)
Perhaps the classic example of an aqueous-based solvent is common “Windex” which is a mixture predominantly of deionized water, with isopropyl alcohol, butylcellosolve, ammonia and a blend of surfactants and emulsifiers.
Inorganic solvents are generally comprised of either an acid or an alkaline compound.
A typical example of an acidic inorganic solvent is the commercial product known as “Lime-Away,” which has gone through several formulation changes over its history. Its primary active ingredient is an acid (originally phosphoric acid and more recently a mix of glycolic acid and citric acid) which is effective at dissolving mineral deposits on glass, plastics and porcelains.
A typical example of an alkaline inorganic solvent is household ammonia which is an extremely dilute mixture of ammonia in water to which are added various surfactants, emulsifiers, and detergents to provide a degreasing capability.
Organic solvents can be as simple as rubbing alcohol (diluted isopropyl alcohol), through the common hydrocarbons like kerosene, acetone or hexane, or as complex as the fluorinated hydrocarbons—totally synthetic in their composition, like liquid Freon.
Organic solvents are generally used to dissolve other organic compounds. A mechanic will use a solvent like “Stoddard Solvent” (mineral spirits) to degrease automotive parts, or a shooting enthusiast will use a mixture of kerosene and mineral oil to clean his gun. Acetone is used to dissolve polyester and epoxy resins.
In the sixties a whole family of chlorinated hydrocarbon solvents were developed and used extensively throughout industry for degreasing. These solvents included some of the most powerful degreasers ever created such as Trichloroethylene (“TCE”), 1,1,1 trichloroethane (“TCA”), and Tetrachloroethylene (“Perc” or perchloroethylene). Perc is still used in some dry cleaning systems and even some gun cleaning solvents.
One of the more unique and now almost impossible to find solvent families is liquid Freon. Formulated to be liquid at room temperature and pressures, these solvents exhibit low toxicity and extremely high vapor pressures. Thus, they are strong degreasers that dry almost immediately.
With the advent of concerns over “holes” in ozone layers, these solvents are now no longer manufactured but still available in limited quantities from existing stock.
In the late eighties, 3M developed a unique new liquid they called Novec, HFE-7100—what they called an engineered fluid. For several years 3M sales representatives took samples of the new fluids around to members of industry looking for unique problems their new fluids could solve.
HFE is a unique liquid. It is non-toxic (sales representatives have been known to drink quantities of it to prove this) and behaves very much like water. The big difference is that it does not cause corrosion like water does. It can find uses for displacing water as in drying or as a heat transfer fluid that does not require corrosion inhibitors. Its biggest disadvantage, of course, is its cost, but this is generally outweighed by its unique benefits in the right application.