James Vallette | March 27, 2012
This blog post, originally shared in the Pharos Signal, includes information about parts of Pharos that are no longer available. Please use it for historical reference and for the other useful information it contains.
Pharos has evaluated a wide range of flooring products, from wood to vinyl, rubber, and cork. Now we add another layer of analysis to help architects and designers choose flooring systems that maximize renewable material content and minimize environmental and human heath impacts: Flooring Finishes.
Flooring finishes form a film on or in the surface of floors. There are many types of finishes, and their composition and application vary widely. Some flooring comes into the marketplace with the finishes already in place. Other floors’ warranties require on-site installation of particular finishes.
These finishes can have a considerable impact, as they typically cover the entire surface area of uncarpeted square footage in buildings. As a National Institute of Building Science report notes, “Hard floor finishing is often a process that results in off-gassing for weeks.”
Types of flooring finishes include sealers, surface finishes, and wood hardeners. Within these broad categories are a number of subcategories. The initial products evaluated in Pharos represent two of the more popular types of commercial flooring finishes used with wood flooring: natural oil-based penetrating sealers and waterborne finishes. We will add additional finish types over time, including finishes that contain nanoparticles, and expand the scope to other substrates.
Our evaluations of natural oil-based and waterborne finishes highlight different benefits and challenges. Natural oil finishes can have high levels of renewable content -- some can exceed 90 percent bio-based materials. But natural oil-based finishes can also contain high proportions of solvents. Waterborne varieties usually have no renewable content, but many emit lower amounts of Volatile Organic Compounds (VOCs) than the natural oils.
Both types commonly include chemicals of concern. For natural oil-based finishes, petroleum distillate solvents and drying agents made from heavy metals are particularly troublesome. And waterborne finish formulations can include isocyanates, n-methylpryolidone, phthalates, and perfluorocarbons. Finish manufacturers may not report these chemicals in Material Safety Data Sheets, instead routinely labeling key ingredients as “confidential business information” or “trade secrets.”
Among our findings:
Our initial evaluations found VOC emissions ranging from 50 to 250 grams per liter. Few finishes’ emissions have been independently certified.
Due to the lack of transparency in product ingredients, the Pharos data team has developed common ingredients records to identify chemicals of concern that may be found in these formulations. Waterborne and natural oil finishes have quite different toxicological profiles.
Water-based finishes are systems comprised of acrylic, polyurethane, and/or isocyanates, along with a variety of additives. Isocyanates, which are building blocks for polyurethane/acrylic copolymer systems, are respiratory toxicants and face increasing scrutiny from US health and environmental agencies.
Our examination of upstream co-polymer suppliers’ literature clued us into the use of PFCs in waterborne finish formulations. Short-chain PFCs are used as flow aids in some recipes. Living Building Challenge and Perkins+Will have placed PFCs on lists of substances to reduce or avoid in building projects.
Phthalates – particularly dibutyl phthalate and butyl benzyl phthalate -- may also be used as plasticizers in waterborne finishing systems. Phthalates are reproductive and developmental toxicants.
Another common and problematic ingredient of waterborne finishes is the co-solvent, n-methylpryolidone (NMP). NMP is the primary solvent used in aqueous polyurethane dispersions. A paper from Bayer MaterialScience notes that “NMP is a suspected fetotoxin” and that governments from the European Union to the State of California are regulating it more heavily.
The Pharos data team also examined the issue of agents that speed the drying times for natural oil finishes. Heavy metal-based drying agents have posed historical concerns. A century ago, the most common drying agent ingredient was lead. Other carcinogenic metals – including arsenic, beryllium, and cadmium -- have been used as linseed oil drying agents.
The use of carcinogenic heavy metals as natural oil drying agents is in steep decline. North American and European governments restrict the most problematic driers. Natural oil finishes now manufactured in these continents more likely contain cobalt, calcium, and manganese-based drying agents than lead or cadmium.
Diligence is particularly important for natural oil finishes sourced from Asia, where heavy metal paint driers remain in commerce. Manufacturers in India and Thailand advertize lead octoate and cadmium octoate drying agents. “In outside paints and floor finishes… Lead Octoate is used with Manganese drier to produce a tough and hard film,” reads one site.
For further information, visit the new Flooring Finishes category in Pharos and take a look at our common ingredients records for waterborne and natural oil-based finishes. Click on the “Pharos Team Notes” tab in these records for more details about these recipes.