Tuesday, October 26, 2010
Tech Tip Tuesday
This week's Tech Tip Tuesday is devoted to an often misunderstood and often abused subject - solvents.
Solvents can be very helpful in removing cured epoxy resin and for preparing surfaces for a new layer of epoxy. They should, however, be used carefully. I say misunderstood and abused as people often do not read and understand the MSDS documents for the solvents that they are using, and use solvents when something else would suffice.
Before you start, read the manufacturer's instructions for the epoxy/coating that you'll be using. Find out what solvents the manufacturer recommends and read the MSDS documents for both the solvent and the epoxy/coating that you'll be dealing with.
When working with solvents, you should be using the proper protective materials. This includes gloves, eye protection, a respirator with the appropriate cartridges (usually "organic vapor" cartridges), a powered respirator which brings in fresh air from a slightly distant source. The manufacturer will more than likely list what is appropriate. Be aware that the protection offered by these cartridge respirators is limited and they may become "saturated" with the vapors.
These solvents can damage your internal organs, particularly your brain and liver. You should be working in a well-ventilated area without a source of ignition. (sparks, heaters, open flame, etc.) Your protective equipment must be made from the materials that are indicated in the MSDS as some materials may be dissolved by the solvent that you are using. Remember that what may be the "right " protective material for one solvent may be the "wrong" on for a different solvent."
Never use solvents to clean up bare skin that has epoxy on it. This is a very bad practice as it can actually act as a delivery system to help the chemicals in the epoxy pass through your skin. For un-cured epoxy, vinegar is very useful in preventing the epoxy from curing. Once the cure has been inhibited with the vinegar, you can clean up using soap and water. Some people find waterless hand cleaners to be very good for this purpose.
Use the least volatile solvent that you can. While we could use acetone, instead we use denatured alcohol to prepare surfaces for subsequent coats of epoxy because of where and how we work. If we were working in different circumstances, a soap and water wash or a rinse with ammonia would do the same job to help remove any amine blush that might prevent layers of epoxy from bonding to one-another.
People often underestimate the flammability of solvents until they have a flash fire. Solvents may have vapors that "pool" and create the conditions for spark to ignite the vapors leading back to the can or cloths used with the solvent. We recently had an incident at work where we received some shipping containers that had an open can of Xylol that had spilled. As the vendor who shipped these contianers sheepishly pointed out, it was good that nobody at our facility was a smoker!
Last but not least, be very careful about how you dispose of the materials that are saturated with solvents. Depending on what you're doing, if you have cloths with solvent and products that contain linseed oil, when the solvent evaporates, you can wind up with a situation where the remaining linseed oil can spontaneously combust! This is an altogether too common occurrence.
Please, read and understand how to handle the solvents that you'll be using for your own safety as well as that of those around you.