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Kydex Binders Weather Climate Extremes


Telephone booth directories must be able to withstand climatic extremes. For Qwest Communications Intl, that means temperatures ranging from 100+°F Arizona summers to subzero Montana winters, as well as rain, dust storms, and hail. In addition, the directories must resist vandalism and stand up to the routine wear and tear of thousands of opening-closing cycles per year.

A proprietary swing-up holder shields the directories from destruction by encasing them in binders made of thermoformed Kydex® sheet from Kleerdex Company. Denver-based Qwest -- and telecommunications giant US West, which it acquired in 2000 -- have purchased the swing-up directory holders for nearly 20 years from Benner-Nawman, Inc., headquartered in Wickenburg, AZ.

Maintains Properties at Low Temperatures

The binders encasing the books "are the very essence of the protection," notes Brad Lundstrom, director of operations for Benner-Nawman division BN Fabricators. "If the binders warp or twist or bend out of shape, the outside elements can penetrate to the book."

The company uses two grades of Kydex, both fire rated to UL Std 94 V-0/5V. Kydex T provides impact resistance of 15 ft-lb/in. (ASTM D-256), versus 18 ft-lb/in. for Kydex 100. "We''ve done tests where we chilled the binders on our directory holders to well below freezing, where other plastics tend to get brittle," Lundstrom recalls, "then we''ve thrown them on the floor and stomped on them in order to get them to break or crack, but they just won''t."

Ed Kientz, president of BN Products, a Benner-Nawman division that manufactures phone booth accessories, recalls a two-year period when Qwest switched to a supplier that fabricates binders using ABS. He and a Qwest representative observed a BN directory holder installed 10 years earlier, and nearby, a competing holder containing an ABS binder installed less than two years earlier. The binder of the older directory was intact, while "The [ABS] plastic on the cover of the competing holder was torn," Kientz recalls. "Whole pieces of it were breaking off."

Reduced Maintenance Costs

Qwest switched its directory holder business back to Benner-Nawman for reasons of durability and economics. "Qwest''s original goal was to replace the directory books no more than once a year," Kientz says. But during the two years when Qwest switched to ABS binders, the company''s installers "might be back three, four, or five times a year" to replace the books. Kientz says Qwest representatives told him "our directory paid for itself after their second trip," while the labor costs of additional repair visits actually made the competing product more costly.

From a processor''s standpoint, Lundstrom says the sheet is "easy to form, easy to print on, and comes in a wide variety of colors." To fabricate its directory holders, Benner-Nawman starts with 4 x 8 ft (122 x 244 cm) sheets of 0.093 in. (2.4mm) thick Kydex T or Kydex 100. A custom-designed press heats top and bottom edges of 11 x 17 in. (28 x 43cm) sections of material, positioned above a mold cavity, to 140-150° F (60-66° C). The overlying form then presses the heated sheet into the cavity to turn up 2 in. (5cm) long, 90° edge flaps that will enclose top and bottom edges of the directories. After about 10 seconds cooling time, the shaped binder can be screen printed with logos and other graphics.

With the Kydex sheet, "you can basically screen-print any logo a company might require," says Lundstrom, adding that printing is enhanced because "the material comes in just about any color you''d like." Kleerdex supplies custom-matched yellow sheet for the Qwest directories.

BN uses a fast-curing UV ink. According to Robert T. ("Terry") Brink, operations manager, a fine P-1 Haircell texture of the sheet (with evenly spaced pores of uniform depth) works best for screen printing.

Brink has also printed on polyethylene sheet and finds it "tricky for screen printing," he says, because it requires heat treating before printing. With Kydex sheet, "you don''t have to do anything," he adds.

Stainless steel hinges containing a torsion spring allow the binders to swing on the aluminum spine, and snap shut after use in clamshell fashion.

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