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Back in the mid-1980s, GI Plastek, a custom RIM molder in Newburyport, Mass., was making medical and electronic cabinets, but that market was shrinking rapidly. Plastek then spotted a new opportunity in large, flat panels. “We saw the inefficiency of SMC and RTM for making big parts and post-painting them,” says president Chuck Lagasse. Plastek plunged into relatively low-volume truck, bus, and off-road equipment markets but shied away from the higher-volume automotive business, which was shifting from RIM bumper fascias to less expensive thermoplastics like TPO.
Strong creative resources and the right choice of market focus then enabled Plastek to grow at a time when many other RIM molders shrank or disappeared. Large exterior body and hood panels for heavy construction and agricultural equipment has grown over the past five years to 60-70% of Plastek’s sales.
Its first big RIM panel was a John Deere Harvester roof in 1988, which the company still makes today. When Plastek first made the 5-ft-wide, 57-lb part, it had to team up two metering systems to fill the mold simultaneously. Today, GI Plastek uses machines big enough to shoot 120-lb parts.
“What we do every day is pretty innovative,” says Lagasse. GI Plastek recently became the first molder to use a soybean-based RIM formulation for molding John Deere tractor panels (see p. 25). The company is also one of the first molders in North America to install the LFI (Long-Fiber Injection) system from Krauss-Maffei Corp., Florence, Ky. LFI chops glass fibers and mixes them with resin right in the mixhead. Compared with SRIM using glass mats, LFI is said to cut materials cost 30-40%.
“We do some basic, shoot-and-ship RIM applications,” Lagasse admits, “but primarily we do large body panels that are cosmetic and functional.” No other molder, he says, has Plastek’s capabilities in large cosmetic panels, especially when it comes to in-mold coatings. Since 1988, Plastek has continuously developed its patented ProTek IMC technology based on an aliphatic urethane with uv stabilizers. The coating is sprayed into the open mold before the part is shot. “The process yields a coating that is chemically bonded to the substrate to resist chipping and peeling,” says product development manager Rick Lonardo. “It also delivers excellent DOI (distinctness of image) and virtually eliminates the orange- peel look common with post-applied coatings. The cost advantage is dramatic, especially on large parts that do not need to be handled downstream after molding.” Program manager Ryan McNamara adds that studies have shown cost savings of 40-50% on a finished part versus post-painting.
Last spring, GI Plastek received an award from SPI’s Structural Plastics Div. for the new John Deere Harvester combine rear wall, which is one of the largest RIM parts to receive in-mold coating. The 56-lb, 6 x 8 ft panel is molded in nickel-shell tooling using Baydur polyurethane structural foam from Bayer Corp.’s Polyurethanes Div. in Pittsburgh. That part not only uses the innovative soy-based material, but the ProTek in-mold coating gives it a high-gloss Class-A finish right out of the mold.
GI Plastek has applied its in-mold coatings to other novel materials—such as SRIM composites made either with mat reinforcements or the LFI process. “We can produce rugged composites with a high-gloss, color-matched, uv-resistant finish, right out of the mold,” says R&D technology manager Charlie Beck.
ProTek Clear is a further expansion of IMC technology, whereby a layer of clear polyurethane coating is sprayed in the mold first and is followed with a colored base-coat. When the part is removed from the mold, the clear layer is on the surface of the part. This “two-stage” or “base-coat/clear-coat” IMC is used when long-term color and gloss retention is desired.