K 2013: Single-layer polyacetal tank meets latest fuel permeation regulations

Beefed-up regulations governing fuel permeation from small offroad engine tanks used in such products as lawn mowers and recreational vehicles has seen a flurry of development in plastic-based solutions, sometimes involving multilayer blowmolded constructions, and other times surface treatment (fluorination) of high-density polyethylene (HDPE) single-layer constructions. Now, Celanese (6/A07/B07) has developed a polyacetal (POM) resin that can meet the latest EPA and CARB standards in a single-layer, untreated tank. The barrier properties are intrinsic to the resin.

Stefan Kutta, Global Director, Transportation, says that injection molding (S 9364 LPI) and blowmolding (S 9364 LPB) grades of the POM product are available, but most OEMs embracing the technology are opting for blow molding due to the lower associated tooling costs. "Injection molding entails molding two tank halves then ultrasonically welding them together." This tank type was on display at the Celanese booth incorporated into an actual lawn mower, while blow molded sample tanks were also on display.

Besides low fuel permeation, the new POM copolymer grades also feature improve toughness, while up to a 25% in processing time is claimed compared with other gas tank materials. The materials are said to be compatible with high-ethanol fuels, and provide strength and impact performance even at -40°C.