Low permeation, lightweight solution meets upcoming evaporative emission regulations for fuel tanks

In the mid-1970s metal fuel tanks were converted to plastic, with the predominate material being high-density polyethylene (HDPE), to reduce weight and costs. However, this material allows for permeation. Over its lifetime, a standard walk-behind mower made from HDPE emits 12 pounds of evaporative emissions, which contributes to smog and ozone during warmer temperatures.

Not only is there an environmental impact, there is also a health impact. Gasoline is considered a toxic chemical made up of more than 100 chemicals, including benzene, toluene, ethylbenzene and xylene (BTEX compounds). Breathing small amounts of gasoline vapors can lead to nose and throat irritation, headaches, dizziness, nausea and vomiting, confusion and breathing difficulties.  

Limiting evaporative emissions

In the 1980s CARB conducted research to find out what contributes to greenhouse gases and smog in California. It found that OPE was a significant contributor, and CARB developed an evaporative emissions limit. Currently the limit is 1.5 g/m²/day. In 2000 the EPA studied greenhouse gases and smog and decided to make the CARB regulation cover the entire U.S. Recently the EPA has been tightening the regulations, and in the future CARB plans to further reduce allowable evaporative emissions to approximately .5g/m²/day—a 65% reduction from today. Also, China is looking to adopt a regulation similar to EPA’s in 2021.

Many OPE manufacturers are relying on the fluorination of polyethylene tanks to meet the current evaporative emissions requirements. This technology relies on hydrofluoric acid (HF), a toxic chemical, some of which invariably is released into the environment. Furthermore, this technology is adding complexity to the supply chain and is unable to meet upcoming regulatory limits that are more stringent than current regulations.

Standard HDPE emits 25 to 30 grams of hydrocarbons per square meter per day, more than 15 times the allowable limit. Fluorinating HDPE fuel tanks creates a thin surface treatment of ~0.2 microns thickness in a batch process, yielding an average barrier performance two times below the specification, however, variation in performance can be three times specification. Over time, this thin barrier on the tanks can erode during normal use of the equipment, such as surface abrasion or wear, thus becoming less effective, ultimately making it a risky choice for staying within compliance over the useful life of the tank.

Because OPE manufacturers are under pressure to meet EPA’s 2022 regulations, limiting evaporative emissions from fuel tanks has become an area of focus. CARB already amended its small off-road engine rules to increase stringency of procedures used to test evaporative emissions, and both CARB and EPA are testing and auditing products they purchase from retail stores. They are finding some products to be non-compliant.

Leading OPE manufacturers have begun to understand that the chemicals necessary for HDPE fluorinated tank production are harmful to the environment and people. Just as the consumer electronics industry has moved away from the use of bromine in their products, more and more players in the OPE market are looking for ways to reduce their exposure to fluorine in theirs.

It is an excellent barrier to evaporative emissions and guaranteed to last for the lifetime of the product. Akulon Fuel Lock is EPA and CARB compliant, and seamlessly drops into existing HDPE manufacturing process while eliminating the use and risk of hydrofluoric acid use.

Manufacturers that are early adopters of this solution have already reduced their carbon footprint, avoided hydrofluoric acid hazards, lowered inventory costs by eliminating costly shipping steps, and bolstered their credibility for sound environmental stewardship while eliminating regulatory non-compliance risk associated with the fluorinated HDPE tanks.

The process of making fuel tanks from Akulon Fuel Lock can be certified once, ensuring the quality and low permeation rates across all tanks produced from the material since the barrier performance is inherent to the material, rather than a thin surface treatment. With a permeation rate that is less than 20% of the EPA limit, Akulon Fuel Lock has been designed to eliminate current and future concerns regarding non-compliance, EPA fines and the risk of costly equipment recalls.

Akulon Fuel Lock is a robust and reliable solution for the conditions of use for outdoor power equipment. It has purpose-fit mechanical properties, including high strength, stiffness and impact resistance, even at low temperatures. Fuel Lock has been specially formulated to provide excellent low temperature toughness, and it has a higher melt point than HDPE, allowing its use in closer proximity to engine heat, and a flexural modulus that is 60% higher than HDPE.

To learn more, visit dsm.com/fuellock or plasticsfinder.com for related products and application data sheets. Contact us for product inquiries or sample requests.