February 2005

A blowing agent update

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Learn why the change to pentane was made and what it means for polyiso

by Lorraine Ross
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With a predicted production of more than 5 billion board feet during 2005, polyisocyanurate roof insulation continues to be the dominant thermal insulation material used in the commercial roofing market. Currently, polyisocyanurate has improved environmental characteristics and is an important component in sustainable construction. Yet the past 20 years have presented a series of challenges largely driven by environmental regulations. The story of polyisocyanurate's survival is unusual given the typical demise of products whose raw materials have been targeted by environmental groups. Incredibly, the resultant product changes have led to an improved product and a closer cooperation between polyisocyanurate producers and roofing contractors, especially in improving the polyisocyanurate standard, ASTM C1289, "Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board." This article will provide an update about polyisocyanurate and a few observations of the product's future direction.

The environment

Polyisocyanurate insulation has three major components: MDI, polyol and a blowing agent. When these three components are mixed, along with small amounts of catalysts and surfactants, a heat-generating chemical reaction causes the liquid blowing agent to boil. The resultant blowing agent vapor expands the foam, creating gas-filled cells that provide polyisocyanurate's high thermal-resistance value. Currently, the polyisocyanurate industry uses a hydrocarbon blowing agent, pentane, which has zero ozone-depletion potential and negligible global-warming potential. However, the eventual use of pentane as a blowing agent was spurred by a series of environmental events that began in earnest in 1987 causing the polyisocyanurate industry to reformulate the product twice during a nine-year period.

From its introduction during the late 1970s, the polyisocyanurate industry was using CFC-11 as a blowing agent. Although the history of the connection between CFCs (chlorofluorocarbons) and ozone layer depletion is well-documented, a brief timeline of the issue and its implications for the...

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