The Green Thumb: Extira Marks the Spot
In 2003, CMI, a Chicago-based building products company, won the Innovative Technology Award at the Anaheim Woodworking Fair, held in Anaheim, Calif., for their “Next Generation” product Extira, an exterior-grade treated wood composite panel. CMI produces Extira at their state-of-the-art plant in Towanda, Penn. Aside from Extira, CMI also produces Craftmaster Doors at their Christiansburg, Va. and Ozark, Ala., facilities as well as a line of treated exterior-grade composite trim: MiraTec. The U.S. Green Building Council’s LEED green building rating/certification program has also recognized Extira under IEQ (Indoor Environmental Quality) Credit 4.4: low-emitting materials; composite wood and agrifiber products.
What is Extira?Extira is an unprimed, square-cut composite panel product resistant to termites, rot and moisture. It can be used for any non-structural paint-grade exterior application and works well in high-moisture interior environments. Confident of its excellent exterior performance, CMI offers a five-year limited warranty. The panels are phenolically bonded and treated with zinc borate and are S2S (smooth on two sides). Panel density and MOR (Modulus of Rupture) are 48 pounds per cubic foot (lbs./CF) and 3,600 PSI respectively. Panels: 1/2 inch, 5/8 inch, 3/4 inch, 1 inch and 1 1/4 inch thick are available in three sizes: 49 inches by 97 inches, 49 inches by 194 inches and 24 inches by 194 inches.
Benefit wise, Extira provides superior density uniformity by way of the TEC manufacturing process. From an environmental perspective, Extira is eco-friendly since it uses no virgin timber. Composed of 90 percent wood, Extira panels use the mill waste of sawmills as their main source of raw material. The NAF (Non-Added Formaldehyde) phenolic resin binder gives off practically no formaldehyde.
MDFTo understand Extira’s claim to fame, we must first understand the manufacturing process of the composite panel product it is meant to compete with: Medium Density Fiberboard (MDF). In the MDF manufacturing process, unlike Extira’s, nothing is added to resist moisture, rot and/or termites. Wood fibers are blended with UF (Urea Formaldehyde) typically and then formed into a mat. UF is water-soluble and, in 2004, the IARC (International Agency for Cancer Research) upgraded Formaldehyde from a “probable” to a “known” human carcinogen. The mat is pressed between hot “platens” in an open press whereby heat from the platens is transferred to the mat. While the moisture present evaporates, air gets trapped in the mat and air and steam escape around the periphery of the mat. Because it takes a long time to transfer heat to the center of the mat, core temperatures remain higher at the center of the mat than at the edges until all moisture is removed. The end result can be inconsistent physical properties in the finished MDF panel since these properties are greatly influenced by the final core temperatures within the mat. Typically, MDF panels are warranteed for only 30 days.
TECCreated and patented in 1997, Extira and its companion product: Mira Tec Trim, both utilize the revolutionary TEC manufacturing technology. Similar to the microwave effect, a fiber mat consisting of wood fiber, phenolic resins, zinc borate and water repellent is loaded into a sealed press where steam is directly injected, thus allowing for uniform heat transfer. Unlike the open press used in MDF and Hardboard production (much slower and creates wide variations between internal and external mat temperatures), steam escapes evenly throughout the mat via controlled, forced convection. Physical properties such as density are greatly improved by using this closed or “sealed” press method. After the mat cools, a six-headed sander smooths both sides of the panel to achieve caliper thickness tolerances of plus or minus 0.005inch. Pursuant to ASTM D1037-99, standard test for “Thickness Swell” (saturation in water), MDF swells 2.5 times more than Extira.
One of the key ingredients in Extira is zinc borate, an EPA (Environmental Protection Agency) registered biocide. Zinc borate is effective at controlling the growth of both white and brown rot and effectively protects against organisms that eat/destroy wood such as the infamous FST (Formosan Subterranean Termite). Since Extira is made primarily from wood, it machines and handles very much like wood itself. It resists cracking/splitting/checking and provides 100 percent yields due to the TEC manufacturing process. This process produces no knots, voids, etc. With stable pricing and ready availability, Extira is ready to compete directly with MDF for market share.
Old Before Its TimePerformed in strict accordance with ASTM D1037-99, the Accelerated Aging Test rates the durability of a product due to seasonal changes. After a six-cycle accelerated aging test, Extira maintained 90 percent of its original strength. The test seeks to mimic humidity, temperature and moisture conditions resulting from seasonal changes. This includes freezing, thawing and heating cycles.
Since it is a wood-based composite, Extira must be primed and painted prior to exterior exposure. Though it can be laminated to itself and a variety of other surfaces, it is recommended that exterior-grade (polyurethane) adhesives, rather than water-based adhesives, be used. At the time of this writing, tests were under way for suitable adhesives to use with Extira. Aside from EMMAQUA (accelerated weathering) testing, Extira has been subjected to a plethora of tests including: Rainwall – wet and heated dry cyclical testing; Environmental Chamber – for buckling; Mechanical properties; Test fences in Pennsylvania, Mississippi and Illinois.