With strict regulation of gasoline vapor emissions already in place, and even stricter rules for some applications set to take effect in 2011, polyamide supplier Rhodia bets new grades, part of its Technyl polyamide 6 (PA6) range, could be the answer to some processors’ concerns. Not only will the materials, as monolayer fuel cans or small gas tanks for offroad vehicles and the like, satisfy stricter emissions limits, but they also can be readily processed on standard extrusion blowmolding machinery, with optimum results returned if a polyamide-specific screw is used in the plasticizing unit.
Processors of small fuel tanks such as this one can benefit from the new materials.
Alan Dubin, business development manager in the supplier’s Cranberry, NJ offices, says the as-yet unnamed materials also can be run on multilayer blowmolding machinery, and on existing molds. “The good news is that no new machinery is necessary,” he said in a telephone interview with MPW. Rhodia has offered similar materials outside North America for some time. The two new materials now being introduced to the North American market have been improved upon, especially in terms of their cold impact strength, which he said has been tested down to at least -20°C “and can probably go lower.” Scrap from blowmolding can be ground and reintroduced into the process with no loss of barrier performance, he added. Experience in production applications and in industrial trials has shown no cycle-time loss versus high-density polyethylene.â¨
Most jerry cans and small fuel tanks for motorcycles, lawn mowers, snowmobiles, and other vehicles are made on multilayer extrusion blowmolding machinery with between three and six layers used. Barrier layers of ethylene vinyl alcohol may be embedded between polyethylene layers, for instance, or fluorination can be used to provide a vapor barrier.
According to Rhodia, the two grades offer gasoline permeation performance on fuels like E10 that exceeds that of existing blowmolding materials like HDPE and PBT, and equals or exceeds multilayer material solutions. Rhodia is now in the final stages of product optimization and product prototype testing on a number of new applications. Dubin says the supplier is still in the process of characterizing the new grades’ processing windows, but that results so far point to significantly wider processing windows than standard PA6 grades.
Testing by an external North American lab and on customer parts has proven the ability of these materials to meet or even exceed permeation regulations from CARB (California Air Resources Board) and the U.S. EPA, meaning processors can satisfy permeation performance requirements without investing the $3-6 million a multilayer blowmolding machine might cost. Processors also need not send parts out for fluorination, another means of improving a part’s permeation performance.
The materials may also be injection molded and can be hot plate- and vibration welded. —Matt Defosse