Will PE100 fly north of the Rio Grande?

Things may be changing in the North American pressure pipe market with the introduction of new polyethylene (PE) grades.

At least that is what polymer maker Dow Chemical (Midland, MI) hopes with the commercialization of its bimodal Continuum grades, which are said to equal or better existing PE100 materials available until now only in Europe and Asia (December 1995 MP, p. 71; MPI, p. 73).

Dow Chemical has been a user of these grades since October 2005 when it bought back plastics pressure pipes processed for use at eight Dow installations in West Virginia, Louisiana, Texas, and its Canadian Fort Saskatchewan brine pipeline operation in either solid wall pipe or as a liner for steel pipes, says Heather Lau, North American market manager pipe, fittings, and geomembranes.

The material, produced using a Unipol II dual-reactor, gas-phase process (see drawing), is claimed to be the only such high-density family produced in North America, with one grade, DGDC2490, going beyond existing PE100 properties, essentially a PE100+. Lau says presently U.S. PE pipes are 90% medium density (MDPE). PE100 pipes allow gas and water distributors to use up to 30% thinner pipe walls that meet existing pipe pressure ratings, or the same wall thickness to be applied toward higher pressures. Slow and rapid crack propagation is claimed to be enhanced, a 100-year service life results, and pipes can withstand higher pressures at elevated temperatures.

So why has it taken more than 10 years to introduce a material that is widely available in Europe and Asia? Lau says a lack of standards from the ASTM organization to parallel ISO standards that govern PE100 grades hampered introduction and acceptance into the U.S. Existing ASTM designation PE2406 and PE3408 do not align with ISO norms for PE100.

Stephen Boros, technical director of the Plastics Pipe Institute (Washington DC), concurs with Lau and says that although PE100 is not new in North America—since it has been brought over from Europe for processing in the U.S. in the past—it never was widely adopted due to standards recognition.

“Under the [existing] ASTM standards methodology for stress rating PE materials, the PE100 type qualified for the same long-term strength as currently available [MDPE] materials,” Boros says. “It was not possible to take advantage of the improved performance benefits such as slow crack growth resistance. ASTM standards also did not have a rapid crack propagation requirement, so again PE100 or PE100+ properties were not fully utilized.” Pipe manufacturers complained about the inability of utilities to agree on a common specification.

Timothy Lauder, technical support team leader at Public Service Electric & Gas (PSE&G), headquartered in Newark, NJ and a customer of Dow’s Continuum, says gas distributors like his company found it surprising that bimodal PE materials were not being offered in North America, despite the fact that the suppliers were large resin producers with global markets.

He also says pipe processors that controlled the market were only offering pipes extruded from conventional unimodal resin and had no incentive to foster material development or keep pace with Europe. That’s where PSE&G and a number of other New York and New Jersey utilities decided to form the Gas Materials & Systems Committee to discuss the possibility of establishing a common PE material specification.

“As engineers on the Gas Materials & Systems Committee became more educated about the dynamics of the plastics pipe market, they woke up to the possibility of a new reality,” Lauder writes in the May issue of American Gas Magazine. “They realized that the utilities themselves could be a market for new PE materials and that they could work directly with resin producers to play a direct role in PE material performance improvements.”

Following this initiative, the ASTM has started to reevaluate its standards with the introduction of a material designation PE4710, which it claims results in performance attributes of PE actually surpassing those of straight PE100, says Plastics Pipe Institute’s Boros. “I am sure that the PE4710 materials will be very well accepted in the North American markets, especially gas distribution,” he says.

Apparently PSE&G is convinced, since it decided on a 100% conversion from unimodal PE2406 grades to bimodal PE100 materials in December 2004. Since that time more than 3 million ft (900,000m) of pipe have been installed.

The U.S.’s largest pipe processor, J-M Manufacturing (Livingstone, NJ), says it is excited about the prospects for PE100/ASTM4710 in North America. “Our colleagues at Formosa Plastics in Taiwan have been producing this material for some time with good success,” says Daniel O’Connor, assistant VP, polyethylene division at J-M Manufacturing. “We expect exponential growth in the U.S. for this resin and believe it could become the standard for most applications.”

Dow’s Lau sees more resistance to the new material from water distributors, again due to a lack of standards that recognize the increased properties that PE100 brings. She, however, believes change is inevitable because according to the America Water Works Assn. (AWWA; Denver, CO) every day in the U.S. more than 2.45 billion gal (more 9 billion liters) of treated drinking water are lost due to pipeline leaks. It estimates that during the next 20 years more than $662 billion will be needed to replace aging water mains.

Robert Colvin | [email protected]