Pay attention to flash points, and you won't get burned

Published: April 01, 1996, By Bentley, David J.

The flash point of a flammable liquid is the lowest temperature at which vapors above that liquid will burn when exposed to a source of ignition. There is an easier way to visualize flash point. It is the temperature below which one can use or store a product in open containers without concern for forming an explosive mixture of vapor and air.

Along with other properties such as fire point, flammability limits, specific gravity, etc., flash point is an important consideration in the safe management of liquids to avoid a catastrophic fire or explosion. A product with a low flash point is more hazardous and requires more precaution than one with a high flash point. A Material Safety Data Sheet always provides the flash point for a material, if it has a flash point.

Flash point influences container, shipping, storage, and use. The flammability of a product may require it to have a certain type of container or to meet specific packaging regulations. Some carriers will not transport materials below a certain flash point or have restrictions directly related to the flash point. Compliance with the rules imposed by insurers and local governing bodies often limits storage of products below a certain flash point. These stipulations may concern the location and quantity of storage. During the application of a flammable material, most people know how to avoid the many hazards that can cause fires.

Most converters or others handling materials having a flash point simply use the value reported on the Material Safety Data Sheet. That is often appropriate.

A rarely considered exception arises in those instances when someone adds an ingredient to a purchased adhesive or coating. Diluting with a solvent or further formulating with a plasticizer, resin, or other ingredient may alter the original flash point of the material. Depending on the particular nature of the material added, the flash point could increase or decrease. For solvents, the addition of a chlorinated product could increase the flash point. Diluting with a low-flash-point liquid like heptane or acetone might decrease the flash point.

To ensure utmost safety, it is therefore imperative to know the flash point of an altered product. There are various scenarios. If the modification has raised the flash point, one may be wasting effort and money using unnecessarily stringent conditions.

At the other extreme is the possibility that the flash point is lower. This scenario could endanger an operation and the employees and may be violating local government regulations or insurance requirements. Since there are different tests to measure flash point, learn before having the product tested which test is applicable according to the insurer or regulator.

Handling aqueous materials also requires care in this regard. It is common to add an alcohol - a flammable material with a flash point - to aqueous products to decrease foaming tendency or to improve wetting characteristics on a substrate. Has the alcohol addition changed the flash point to a value where it is now subject to certain restrictions? If a converter dilutes an adhesive or coating with alcohol during the coating operation and keeps any unused portion, can he still store it as a truly aqueous product? The only way to answer these questions is to measure the flash point of the liquid. Note especially that the aqueous product as purchased may already contain enough of an ingredient that the slight alteration made by the converter is the critical change that can alter the flash point.

Avoid burning yourself, either literally or figuratively, by paying special attention to flash points of adhesives, coatings, and any liquid. In the literal sense, you can burn yourself by failing to observe the necessary precautions with a material having a flash point and thereby causing a fire. In the figurative sense, you can burn yourself with a fine or other penalty by violating requirements for a new material you created when changing a purchased product.

It is imperative that you know the flash point not only of products you purchase but also of anything you make through modification or addition of ingredients.

David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service.