It's what we had to do to save the business," says John Morrison, president of Fosta-Tek (Leominster, MA), a custom molder of optical products. What the company did was design and build a Class 100 cleanroom and, inside it, a new line for applying an abrasion resistant coating to thermoplastic lenses. The business in question, a polycarbonate face piece lens for the Self Contained Breathing Apparatus (SCBA) worn by firefighters, had to meet a more rigorous standard.

The National Fire Protection Assn. (NFPA) writes the standards. It recently tightened the requirements for SCBA components, including the ability to withstand 10 seconds of direct contact with open flame and temperatures between 1500 and 2100F. The thermally cured hard coating Fosta-Tek had been using on its polycarbonate lenses crinkled under that assault, impairing visibility. Morrison says other coatings did likewise.

Fosta-Tek turned to its coating supplier, GE Silicones (Waterford, NY), for assistance. GE had a possible candidate in development but commercial introduction wasn't expected for 18 months. But with the new NFPA standard taking effect in less than a year, GE intensified efforts and got the developmental hard coat into production in record time: five months.

Extensive testing showed that the hard coat would meet the new standard for heat! flame resistance as well as abrasion resistance... and do so with a very thin layer (.00004 to .00005 inch).

Acrylic and urethane coatings require a much greater thickness, and don't have as good chemical and abrasion resistance. The new hard coat, called UVHC 8550D1, aggressively adheres to many substrates, including ABS, acrylic, CR39, thermoplastic polyesters, and PVC without a primer (unlike the previous thermally cured coatings), and cures in seconds under UV light.

Morrison: "Fosta-Tek's need for a fast solution to our coating dilemma was the catalyst that led to this new product line. GE made the development of the hard coat a top priority. They provided R&D expertise, manufactured a pilot lot of the coating, and helped our people learn about radiation curing, which we had not done before." In return, Fosta-Tek provided GE with valuable production scale evaluation of the hard coat's performance.

Fosta-Tek's biggest investment between $350,000 and $400,000 was a new cleanroom for applying and curing the silicone hard coat. It measures about 400 sq ft. The lenses are dip coated and

UV cured on both sides simultaneously on a conveyorized line. Morrison says parts up to 12 inches square can be treated in large volumes. Coating the SCBA lenses is a oneshift operation. Morrison is investigating other applications. Possibilities include reusable bottles, laser optics, sporting goods, labels, and clear sheet.

An intriguing possibility is the lenses protecting warning lights on aircraft wing tips. Prototype treatment with the new hard coat from GE Silicones has produced five to 10 times improvement in life over conventional hard coats. For further information on the silicone hard coat