Truly Realistic 'Stone Effect' Rotomolding Compounds Create New Design Resource for Replacing Stone, Wood, and Metals

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BRAMPTON, ONTARIO, CANADA, April 17, 2000: Nu-Plast, Inc., a North American compounder and distributor of specialty thermoplastics, has licensed an exclusive U.S. Patent as the basis for its new Stone Effect [trademark] linear low-density polyethylene (LLDPE) products for rotational molding. The unique technology involved yields a uniform and strikingly stone-like appearance in components of virtually any size.

Already proven in outdoor and indoor commercial applications, Nu-Plast Stone Effect compounds contain pigment systems developed by Teknor Color Company (Lodi, Ohio, U.S.A.), and are available in truckload and LTL quantities in sandstone, dark millstone, white marble, green marble, and medium gray hues.

Go Plastics Inc., a custom and proprietary rotational molding company with plants in Kitchener, Ontario, Canada, and Canton, Georgia, U.S.A., currently uses Stone Effect products to manufacture its Streetsmart [registered trademark] outdoor magazine and newspaper vending racks and proprietary Urban Images [registered trademark] line of park benches, planters, and trash receptacles. "People are always impressed, and usually rather surprised, at the very realistic appearance of our products," said Ed Gollob, Go Plastics CEO.

According to Nu-Plast President Keith Harradence, his company's Stone Effect rotational molding products are precise mixes of different colored LLDPE particles with various mesh screen sizes, and controlled amounts, of "fines," the smallest particles which can present processing and part quality problems.

"Besides providing the exact colors and ratios of different components from batch to batch, Nu-Plast bags Stone Effect products to minimize particle size separation due to settling, a phenomenon which would be magnified if the compounds were supplied in large containers like gaylords," said Harradence. "This special handling ensures the consistent granite look afforded by Stone Effect compounds."

Dennis Foy, Rotational Molding Market Manager for Teknor Color, relates that the pigment packages used in Nu-Plast Stone Effect products are formulated to optimize the appearance, processing behavior, and end-use performance of parts, including outdoor applications such as some of the products now manufactured by Go Plastics.

"Rotomolding large 'appearance' components presents several challenges to colorant suppliers," said Foy. "For starters, rotational molding subjects thermoplastics to higher temperatures and much longer 'heat histories' than other processes, requiring that pigments and additives like UV stabilizers be formulated to withstand this stress without degrading part properties. At the same time, the static charges inherent in rotomolding must be managed to prevent swirl patterns and other defects in components. Surface appearance and texture are highly dependent on both material properties and processing conditions."

Go Plastics refined its technology for processing Stone Effect compounds prior to introducing its Streetsmart vending machines and Urban Images products. "We are now working with several large companies to apply the advantages of these unique materials to other applications, which are mainly outdoor end-uses," said Gollob. His company also plans to launch an entirely new series of proprietary products this year, but for competitive reasons Gollob declined to elaborate.

One key design factor with Stone Effect products, he said, is that they work best in
components without extensive flat surfaces because these areas tend to "pool" [i.e., accumulate] fines and consequently exhibit undesirable gloss that detracts from the stone-like appearance of parts. Gollob gave the example of the seatback areas of Urban Images park benches, which are covered by advertising panels to hide minor flaws.

"Most consumer and industrial products incorporate very few flat part expanses, primarily because curved geometries are far stronger than flat sections, which minimizes the limitations presented by this pooling phenomenon," said Gollob. "As a result, we have seen widespread interest among design engineers in diverse markets looking for ways to produce large and hollow plastic parts at lower cost than plastic components produced by injection molding or other processes." Go Plastics provides integrated CAD/CAM services for customers seeking to streamline part and mold designs and cut product development time.

An unanticipated advantage of designing parts with the Stone Effect products, Gollob added, is that the cast tooling involved does not require the time and cost incurred in polishing the surfaces of most rotational molds. "In fact the rough surface texture of unfinished tooling actually enhances the stone-like appearance and feel of parts by eliminating smooth sections and minimizing gloss."

For more information on Go Plastics, visit the company's web site, www.goplastics.com or send e-mail to inquiries@goplastics.com Phone: 519-894-9498. Fax: 519-894-9966.

Nu-Plast can be reached at 800-463-6169. Fax: 905-454-2668.