Styrofoam is a trademarked brand of closed-cell extruded polystyrene foam (XPS), commonly called "Blue Board", manufactured as foam continuous building insulation board used in walls, roofs, and foundations as thermal insulation and water barrier. This material is light blue in color and is owned and manufactured by The Dow Chemical Company.
Oddly enough, the word styrofoam is colloquially used worldwide to refer to another material that is usually white in color and made of expanded (not extruded) polystyrene foam (EPS). It is often used in food containers, coffee cups, and as cushioning material in packaging. The trademarked term is used generically although it is a different material from the extruded polystyrene used for Styrofoam insulation.
The Styrofoam brand polystyrene foam, which is used for craft applications, can be identified by its roughness and the "crunch" it makes when cut. Additionally, it is moderately soluble in many organic solvents, cyanoacrylate, and the propellants and solvents of spray paint.
In the 1940s, researchers in Dow's Chemical Physics Lab, led by Ray McIntire, found a way to make foamed polystyrene. They rediscovered a method first used by Swedish inventor Carl Georg Munters, and obtained an exclusive license to Munters's patent in the United States. Dow found ways to adapt Munters's method to make large quantities of extruded polystyrene as a closed cell foam that resists moisture. The patent on this adaptation was filed in 1947.
Styrofoam has a variety of uses. Dow produces Styrofoam building materials, including varieties of building insulation sheathing and pipe insulation. The claimed R-value of Styrofoam insulation is five per inch.
Styrofoam is composed of 98% air, making it lightweight and buoyant.
Dow also produces Styrofoam as structural insulated panels for use by florists and in craft products. Dow insulation Styrofoam has a distinctive blue color; Styrofoam for craft applications is available in white and green.
The EPA and International Agency for Research on Cancer reported limited evidence that styrene is carcinogenic for humans and experimental animals, meaning that there is a positive association between exposure and cancer and that causality is credible, but that other explanations cannot be confidently excluded.
- Dow Chemical Company Styrofoam page
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- US 2450436, Otis Ray McIntire, "Manufacture of cellular thermoplastic products", published 1948-10-05, issued 1948-10-05
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