Thermoplastic injection molders gravitate toward long-fiber-reinforced composites when seeking materials cheaper and lighter than metal, and stronger and tougher than choppedstrand. Long-fiber material is ``a way to make some of these small or large parts faster, better and stronger, and it's catching on,'' said Benjamin Rasmussen, a composites industry consultant and principal of BMR Associates in Watchung, N.J.
The market is ``busier than ever. It's chopped material, but goes beyond it,'' Rasmussen said.
``This highly engineered product is on time for automotive needs and in line with what Detroit wants,'' according to Rasmussen.
In a recent technical paper, Malcolm Rosenow said, ``Long-fiber-reinforced-thermoplastic materials offer unprecedented metal replacement opportunities'' and combine the performance of continuous reinforcement with the economies of injection molding.
Three compounders, each with major corporate marketing muscle, supply about 90 percent of the material and see bright futures for long fiber. Consider these examples:
In Roseau, Minn., Polaris Industries Inc. assembles the Xplorer 4x4 all-terrain vehicle, which contains 31.6 pounds of Celstran long-fiber material from Polymer Composites Inc., known as PCI. KenTech Plastics Inc. of Hopkinsville, Ky., molds front and rear racks, floorboards that can support the vehicle, and a one-piece bumper that replaces pipe and steel and meets 5-mph-impact requirements.
A Korean manufacturer of cooling tower fans reduced blade weight by 56 percent, cut costs about 30 percent and improved fan balance and rigidity using LNP Engineering Plastics Inc.'s long-fiber composite instead of fiberglass layup. Shin Jin Co. of Seoul, South Korea, injection molds Verton PF structural nylon 6 to make the hub and blades for fans with diameters of 8 or 10 feet.
EBW Inc. of Muskegon, Mich., specified a 4.2-pound access cover of DSM Engineering Plastics Inc.'s long-fiber thermoplastic to replace a 17-pound, cast-iron version on spill containment units at gasoline service stations. The Fiberstran reinforced nylon 6 withstands a heavy-vehicle static load of 20,000 pounds and resists corrosive chemicals and inclement weather.
PCI, LNP and DSM buy the fibers in a continuous form and then coat and chop them into pellets for sale to thermoplastic injection molders.
Long fiber has impact strength, high glass content and flexural strength and modulus at elevated temperatures but demands special molding skills to produce structural metal replacements.
Growth has been dramatic. Industrywide, North American long-fiber sales in 1995 could exceed $25 million, a 39 percent increase from 1994 sales of $18 million, according to John Sage, LNP's Verton product manager.
``And LNP is growing at a higher percentage'' than the industry, he said.
Sage said the European long-fiber market totals about $20 million and is ``growing, but notas fast'' as the North American market.
Russell Bockstedt, PCI's Celstran product manager, estimated the North American market consumes 15 million to 20 mil-lion pounds of long-fiber material annually with an average selling price of $2 a pound, for a total market of $30 million to $40 million.
``We doubled our business last year,'' said Patrick Johnson, PCI vice president of sales, ``and all we do is long fiber.''
DSM sales of long-fiber ther-moplastic will increase 40 percent this year, forecasts Fred Boss, product line manager.
``Beginning in 1992, we re-established ourselves using the pultrusion process,'' Boss said.
In 1994, after many years of decline, DSM grew 15 percent using the new technology, he said.
Boss estimated the 1995 North American long-fiber market at $25 million, but he had no estimate for Europe, a market that DSM is evaluating for expansion.
Automotive is the key long-term market. LNP has a field market specialist in Detroit working now to get applications on 1998 models and beyond, Sage said.
``This product fills a cost performance window'' for automobile makers, he said.
For two years, LNP has supplied Verton structural nylon composites for use in molding the 8-pound seat back and pan on the Dodge Viper. And in the past year, Verton structural polypropylene composites reduced by 10-20 percent the cost of making the battery tray for the Malaysia-produced Proton automobile, Sage said.
For the moment, LNP relies for volume on consumer and industrial pump, marine, building and hardware applications.
The Verton ``product line is one we see as our top performer for the future,'' Sage said.
PCI's Celstran nylon 6/6 with 50 percent long-glass reinforcement is used for a clutch part that replaces cast-aluminum on manual-transmission Ford Ranger and Explorer trucks. In another use, a thin-wall auto battery tray of Celstran PP consolidates parts and reduces weight.
On the recreational front, GT Bicycles of Santa Ana, Calif., markets a molded bicycle wheel of long-carbon-fiber-reinforced Celstran nylon. Innovations in Composites Inc. of Oceanside, Calif., designed the one-piece hollow wheel. An internal mandrel of a low-melting-point metal alloy is overmolded with the thermoplastic, and then the mandrel, or core, is melted out.
Glass supply is a major issue.
Long fiber is ``a growing business: The market's there, the customers are there,'' Sage said. ``Now, glass suppliers are recognizing the material's value and growth and are committing resources to support our growth plans for 1996 and beyond.''
No material availability problems exist at PCI.
``We are not hindered by glass supply,'' Bockstedt said. ``We have some strategic partnerships with glass suppliers.''
Bockstedt noted that continuous fibers are ``a little more expensive than the cut glass,'' the quarter-inch, chopped-strand pellets that molders use for most applications. Glass suppliers sell substantially more chopped strand than long fiber.
Rexford Bradt invented the concept of long fiber for compounded thermoplastics in 1952 and formed Fiberfil Corp. The technology had limitations, however, and the market favored the easier process of making chopped strand.
In the early 1980s, both PCI and an ICI plc unit, now LNP, made technological breakthroughs that improved polymer fiber impregnation. LNP holds multiple patents covering the Verton process, material composition and shaped articles. PCI's patented technology focuses on a proprietary manufacturing process to achieve complete fiber-to-resin contact that DSM innovated in the early 1990s. Slowly, the plastics industry began accepting long fiber as a viable structural engineering material.
A technical paper at the 1995 Society for the Advancement of Material and Process Engineering symposium, held May 8-11 in Anaheim, Calif., discussed PCI's approach to injection molding of long-carbon-fiber-reinforced thermoplastics.
A melt-impregnation pultrusion process thoroughly encapsulates each uniformly oriented fiber in thermoplastic resin, said Rosenow, PCI's advanced materials manager. The resulting pellets combine the fibers' high tensile properties and the resins' high-impact values.
Rosenow compared material costs. Continuous carbon-fiber-reinforced composites of thermoplastics such as polyether-etherketone cost more than $200 per kilogram as used for low-volume aerospace part fabrication. Injection-moldable long-fiber-carbon-reinforced thermoplastics cost $30-$40 per kilogram.