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.
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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