A new, patented line of high density polyethylene (HDPE) resins offers improved resistance to bio-diesel fuels, recommending them for automotive fuel tanks at a time when many governments are calling for greater usage of biofuels. The Lupolen line is available for blowmolding (Lupolen 4261 AG BD) and injection molding (Lupolen 4261A IM BD) processes. The manufacturer says the new resin has improved chemical resistance, which allows it to be in contact with fuels that have a higher percentages of bio-diesel. In the European Union, a directive on the use of bio-fuels or other renewable fuels for transport is expected to require bio-fuels to attain a higher percent share of the total fuel market by 2010. In the U.S., the passage of EPACT2005 calls for greater usage of biofuels, with preliminary data for 2006 from the Energy Information Administration, showing that ethanol use rose to 5.4 billion gallons, with bio-diesel production at 91 million gallons, or 0.21% of the U.S. distillate fuel oil market. Ethanol blended into gasoline is projected to occupy 4.3% of the total gasoline pool by volume in 2007, 7.5% in 2012, and 7.6% in 2030.
In testing, the manufacturer found that after 1500 hours of contact with 100% bio-diesel fuel, the grade changed its intrinsic viscosity by 1.7%, which equates to a nearly 30-fold improvement in resistance compared to standard HDPE grades that were previously used in fuel-tank applications. Lupolen 4261 AG BD and Lupolen 4261A IM BD also reportedly maintain their physical and chemical properties at the same level compared to the manufacturer’s conventional Lupolen 4261A product, including the melt viscosity during processing, so previous molds and machinery wouldn’t require modifications.
The manufacturer says the grades were examined with an enhanced test method, where fuels with high bio-diesel-content are left in an HDPE container for extended periods at elevated temperatures. This environment results in the HDPE being exposed to atmospheric oxygen and moisture, which in combination can attack the HDPE and change material properties, potentially affecting the performance of a tank. In the test, fuel tanks were subjected to temperatures of 40°C, with an exposure time of 11 years using 100% bio-diesel samples. LyondellBasell, Rotterdam, The Netherlands (http://www.lyondellbasell.com/)