Vol 5 No 2

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Other articles in this issue:
Film Thickness: Gauge Coating Density
Quality Paint
Seams and Adhesives
Interior Primers
Old Paint, New Strippers
Contractor Profile: Certified Coatings
Product Profiles
Product News
Painting Tips

 

 
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paint strippers
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paint strippers

 

 

Paint Strippers

In recent years, newly developed solvents have become less hazardous to the environment and humans. Nonflammable and noncombustible, they work on a blend of such chemicals as n-methylpyrrolidone and dibasic esters.
by Joan C. Stanus

Ten years ago, about the only alternative to blasting old layers of peeling paint from a surface was to use highly toxic, flammable or caustic chemicals.

It wasn’t all that uncommon for contractors to suffer skin irritations and burns when they were tackling particularly resistant jobs. In some cases, the hazardous fumes caused serious long-term health effects. Disposal of the material was a whole other headache.

“Even though many of these traditional chemicals are very inexpensive to purchase, all the removed paint becomes hazardous waste, regardless of whether the removed coating contains lead,” notes David Hunter, industrial sales manager for Napier Environmental Technologies Inc. Now, “regulations are starting to eliminate their use. The need for worker protection alone is significant.”

Gene Freeman of the Tennessee-based BIX Manufacturing Co. Inc. echoes those sentiments.

“Those old chemical paint and coating strippers can only be described as harmful to both the environment and to workers’ general health,” the company official contends. “For these and other reasons, they’re about to be legislated out of the marketplace … and replaced with biodegradable non-toxic … means.”

A legacy of stripping
Historically, four generations of generic chemical strippers have been produced and introduced in the United States. These include chemicals that are methylene chloride based (introduced in 1940s), caustic Based (introduced in 1970s), n-methyl-2 pyrrolidone based (introduced in 1980s) and water-based, patented Selective Adhesion Release Agents (SARA) technology (introduced in the 1990s).

Until a decade ago, methylene chloride blends were the principal ingredient in more than 90 percent of all paint strippers.

Few disagree there are effective strippers. Even today, methylene chloride strippers are the most widely used strippers in aviation industry, for example. They are also inexpensive to purchase and effective at removing two-component epoxy/polyurethanes coating systems that make up the majority of the coatings on aircraft fuselages.

The toxicity to humans and harsh environmental hazards, of course, is a paramount concern, because methylene chloride is a known cancer-causing agent. Additionally, methylene chloride based strippers are typically mixed with toluene or methyl ethyl ketone, which gives them a low flash point, making them a fire or explosion hazard.

Health and environmental hazards are not the only limitations for these types of strippers. Because of their high volatility and evaporation rate, they have a tendancy to dry out. Often the hardened residue is more difficult to remove than the original coating.

Due to this high volatility, methylene chloride-based strippers tend not to penetrate deeply into paint films, requiring several applications to remove thick films and lifting only a few coats at a time. Disposal is another problem, because all the removed coatings are contaminated, so they must be disposed of as hazardous waste.

Originally developed for paint dipping, caustic strippers are generally considered to be less versatile than other solvent-based strippers. Caustics are very effective on multilayered latexes or alkyd paint systems, but not on chemical resistant materials like two component epoxies and urethanes. Caustics are the prime stripper used in architectural restorations.

The advantages are that they are effective and relatively inexpensive to purchase.

“These type of products work great for architectural applications,” notes Hunter. “The problem is they have to be troweled on at 1⁄8-1⁄4" thick, so the square feet per gallon is small. They must be covered and then scraped off. They’re very labor intensive, even more so if the steps have to be repeated due to incomplete removal.”

A key to using caustics is the addition of a neutralization step. Because architectural coatings are not chemically resistant, they typically can only handle being applied over surfaces with a pH range of 4-11. Caustic strippers leave the surface with a high pH — typically of 13 or above. Therefore, the surface must be neutralized with an acid in order to get the surface pH in a range to accept a new coating. This adds a labor step, so although the materials are inexpensive, the total cost of a project is typically higher than those of more expensive, environmentally friendly strippers.

In recent years, newly developed solvents have become less hazardous to the environment and humans. Nonflammable and noncombustible, they work on a blend of such chemicals as n-methylpyrrolidone and dibasic esters.

“We have taken the anxiety, fear and liability out of stripping,” boosts Janice Nachbaer, national sales manager for Back to Nature Products Co., which exclusively sells the NMP based chemicals. “It’s a new day.”

“These products will work well in architectural restorations,” points out Hunter. “They strip by the same mechanism as methylene chloride. The formulations stay wet longer than their hazardous formulated cousins and these type of strippers can easily remove multiple layers of alkyds, latexes and lacquers, sometimes as many as 10 layers in 24 hours.

The drawbacks to NMP based strippers are that they are virtually ineffective in tackling more chemical-resistant materials such as epoxies and polyurethane coatings. Additionally, all environmentally friendly strippers are slower than their hazardous cousins. Although not considered to be hazardous in the United States, MP-based strippers have already been regulated in other countries.

“It’s just a matter of time before they are here,”notes Hunter.

Developed in the mid 1990’s, SARA strippers are the most recent developments in environmentally friendly strippers. Patented by Napier Environmental Technologies Inc, SARA strippers were developed for the aviation industry for stripping two component epoxies and polyurethanes from aircraft.

According to many in the industry, they strip paint well for a “surprising number” of surfaces, especially when it comes to removing multiple layers of such one-component paints as latexes, epoxy esters, alkyds and urethanes. They’re effective on everything from concrete and wood to steel and fiberglass.
Many in the industry believe they are the “wave of the future.” The U.S. Army Corp of Engineers recently issued a highly favorable report on their use, when compared to NMP- and caustic-stripping alternatives.

Manufactured either odorless or with a slight, “pleasant” scent, these products are touted as working quickly and producing little waste. What waste there is can be disposed of easily.

“The nice thing about SARA technology is waste minimization,” notes Hunter. “The strippers are 96 percent volatile, but they are not flammable. When they evaporate, they leave only the paint chips behind.”

There are, however, drawbacks to SARAs. Similar to NMP-based strippers, it takes longer to remove the coatings of paint when using them than with more traditionally hazardous based chemicals. For contractors who are poor time managers, this time lapse can be a profit buster. Traditionally, SARA technology typically does not brush and roll well on vertical surfaces — however a new brush-and-roll version is now available.

“There is always room for improvement,” admits Hunter. “But there are only a handful of things they can’t strip, like novalac epoxies (tank linings), but recently we have launched a brush-and-roll version.

“Anymore, it’s not a matter of finding the right stripper to fit the right surface. It’s finding a stripper that doesn’t hurt the contractor, the environment or the surface.”

Manufacturers admit that, no matter what kind of stripper is used, it can be a profitable enterprise for contractors — if tackled properly.

“These products are very user friendly,” adds Nachbaer, “but it can take time to get the job done. In most cases, the biggest cost in stripping paint is the labor. If you’re a good time manager, you can caulk and do something else, rather than stand around waiting for coat after coat to work. We try to make it very profitable for the contractor.”

Hunter agrees, pointing out that in a recent partnership with the PBS-television show, “This Old House,” in which Napier supplied products for use, the stripping job cost $14,000, most of which went for labor.

“Stripping jobs can be very profitable,” he notes. “It can be like watching paint dry. But if you spray and then go home, when you come back in the morning you just knock off the excess and are ready to go. Getting to a level where the contractor knows how to use the product and makes money is the key.”

But for small businessmen like Carl Robert, who has worked as a painting contractor in Roanoke, Virgina, for more than four decades, change comes slow. He is, however, willing to try alternatives.


 
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