ANSI - American National Standards Institute
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Transparent Plastic: Turning Architectural Fantasy into Reality

New York, Apr 23, 2007

An Olympic competition swimming arena made of bubbles. A stadium of trellised steel woven into the form of a bird's nest. Sound like an architectural castle in the sky?

These are two of the latest architectural wonders—slotted for completion later this year as the site for the 2008 Beijing Summer Olympics—made possible by the unusually versatile plastic known as ETFE, or ethylene tetrafluoroethylene. A fluorocarbon-based polymer, ETFE is finding its way into some of the most innovative examples of design. Standards from the U.S. voluntary standards community lend a helping hand.

A standard from American National Standards Institute member ASTM International offers a specification used by ETFE manufacturers. ASTM D3159-06, Standard Specification for Modified ETFE-Fluoropolymer Molding and Extrusion Materials, covers melt-processible molding and extrusion materials of modified ETFE-fluoropolymer.

The material’s unique properties make it a pliable canvas for an architect’s artistic expression. ETFE can be spun into a thin yet durable film, to be used in structured sheets or inflated into “pillows.” The Beijing National Aquatics Center—also affectionately known as the Water Cube, or [H20]3—is the largest ETFE project to date. When complete, its walls and roof will be clad in more than 100,000 square meters of blue ETFE pillows just eight one-thousandths of an inch thick. The ETFE pillowing will allow greater light and heat penetration than traditional glass, resulting in a thirty percent reduction in energy costs.

Just one percent the weight of glass, ETFE can cost up to seventy percent less to install. It also boasts extraordinary resilience, including the ability to carry 400 times its weight. The material is available in different finishes, colors and prints, and can be lit from within using LED lights or decorated with projections. For example, at the start of the 2008 Olympic Games, the Water Cube’s exterior walls will turn into a kind of movie screen, showing projections of the swimming competitions inside.

A transparent plastic cousin of Teflon, ETFE is self-cleaning: dirt, snow, sleet, and rain slide off its nonstick, nonporous surface. If exposed to fire, ETFE shrinks from the heat, providing a natural vent for smoke to escape a building. The flammability of ETFE can be tested according to Underwriters LaboratoriesUL 94-2006, Tests for Flammability of Plastic Materials for Parts in Devices and Appliances, which determines the burning behavior of plastic materials.

ETFE can be stretched to up to three times its length without losing its elasticity. Where a large glass panel might measure ten feet by five feet with extensive internal framing, ETFE can span thirty feet or more without any trussing. Architects and engineers reference ASTM D638-03, Standard Test Method for Tensile Properties of Plastics, to determine the tensile properties of plastics when tested under defined conditions of pretreatment, temperature, humidity, and testing machine speed.

Far from being a new material, ETFE first came on the scene in 1970s when DuPont invented ethylene tetrafluoroethylene as an insulation material for the aeronautics market. To this day, ETFE is frequently used as wire insulation in the aerospace industry due to its excellent temperature and chemical resistance. SAE (the Society of Automotive Engineers) has written a number of ETFE standards (both in its natural state and cross-linked for improved physical properties) for use in this purpose. Several of these aerospace standards have also been adopted by the U.S. Department of Defense.

From architecture to aerospace, ETFE’s possibilities are nearly limitless.

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