Engineering Resins

Ryton polyphenylene sulfide was commercialized 30 years ago, but is far from mature. Its potential is considerable, says producer Chevron Phillips Chemical Co., and work is underway to expand grades and applications.

Ryton general manager Michael A. McDonnell, and product manager Robert M. Goodman, say plans include developing PPS extrusion grades, targeting applications in aggressive environments, and vying with costlier materials.

The goal is to take PPS out of its niche and into high-volume applications. Goodman believes that if Chevron Phillips and other producers do this, the global PPS market of 50,000 tonnes (110.2 million lb) will double by the end of the decade.

The extrusion grades will give PPS opportunities for growth. Most of the injection molding applications for which the material finds use are relatively small and tend to run toward metal replacement.

Goodman notes that before this can happen, grades must be developed that expand the properties of PPS in areas like flexibility and impact strength. "PPS is a stiff product," he says. So, Chevron Phillips is developing PPS/elastomer alloys suited for pipe and profile extrusion and related areas like technical blow molding.

The first grades will be available this year and be marketed in the Xtel line as XE series PPS/elastomer alloys. The Xtel line of PPS alloys has been around for five years, notes McDonnell, but this is the first time grades are being combined with elastomers. He declines to disclose the elastomers, but claims they permit pipe to bend 90 deg without rupture.

Target markets for extruded products include corrosion-resistance, chemical-handling systems, wire jacketing, and tubing in automotive fuel lines, where PPS's barrier properties are effective in containing hydrocarbon emissions. "It wouldn't take outfitting too many chemical plants with PPS-lined pipe to grow the business significantly," Goodman remarks. McDonnell says the Xtel alloys can compete with costly materials like stainless steel, glass-lined pipe, and crosslinked fluoropolymers.

Specialty markets also hold the potential for high-volume use of PPS-based grades. One cited by Goodman is blow molded 50-gal drums for aggressive chemicals or chemicals that are heated prior to use. Many are fabricated of high-density polyethylene. Goodman says PPS can handle more aggressive chemicals and can be heated, as would be the case for processing fatty acids, which are stored in solid form. Each drum would use 30 lb of PPS alloy.

The Ryton line, meanwhile, may grow to include different engineering resins. One could be polyarylsulfone, which is amorphous but in the same family of resins as PPS, which is crystalline. McDonnell says having amorphous grades in the Ryton line would complement such PPS properties as heat resistance, while providing better optics, elongation, and toughness. It would also expand Ryton markets in such areas as medical and food packaging. This is a long-range goal, with non-PPS additions expected until about 2006.

McDonnell says that Chevron Phillips is developing plans to expand PPS capacity with a new plant. The company has a 10,000-tonne (22-million-lb)/yr facility in Borger, tx, and plans to build a similar-sized plant. Sites are being evaluated in North America, Western Europe, and China, and a location will be chosen in the second quarter of the year. The Chevron Phillips board will be asked to fund the expansion in the fourth quarter.

Goodman says the plant will utilize new PPS process technologies that reduce production costs and expand resin properties via molecular-weight tailoring. He declines to provide details but says much of the development is focused on the efficient recovery and reuse of polymer from its solution.