New Developments for Plastic Fuel Tanks
Plastic fuel tanks have gained widespread use in applications that include automotive, marine, construction, agriculture, power equipment, and all-terrain vehicles. Plastic fuel tanks are desirable because they can be formed in complicated shapes, are corrosion resistant, are light weight, have high puncture resistance, and are relatively low cost. Fluoro-Seal has developed two new technologies that can make plastic fuel tanks even better. One technology increases the fire resistance of plastic tanks, which enhances safety. The other technology increases the barrier properties of plastic tanks, which reduces the permeation of fuel through tank walls and enables plastic tanks to comply with current and pending environmental regulations.

Increased Fire Resistance
When a current version plastic fuel tank is exposed to fire, the plastic either melts or decomposes and allows the contents to flow out and add fuel to the fire. To buy time in case of a fire, plastic fuel tanks used in marine applications are molded in crosslinked resin. Crosslinked plastic does not melt when heated. But as the temperature of the plastic increases, the plastic begins to decompose and burn. When exposed to a fire, a non-crosslinked plastic tank may fail in approximately 11/2 minutes and a crosslinked plastic tank of the same size and shape may fail in 21/2 - 3 minutes.

Fluoro-Seal has developed a method for modifying plastic tanks such that they have an intumescent coating on the outside surface. When these tanks are exposed to fire, the intumescent coating is converted into a thick, insulating layer of noncombustible foam. This char layer is extremely effective in insulating the plastic such that it barely gets warm when exposed to fire. Using the Coast Guard test protocol, it was demonstrated that plastic fuel tanks made in noncrosslinked resin and coated with the intumescent coating can survive the test longer than is mandated by the requirements.

Barrier to Permeation Loss
One characteristic of plastic fuel tanks is that they allow small amounts of fuel to permeate through the tank walls. The amount of fuel lost this way is quite small and is not usually missed by the owner. However, if one adds up the small amounts of hydrocarbon losses from the hundreds of millions of plastic fuel tanks in use in the U.S., this represents a substantial amount of air pollution. Therefore, various Federal and State agencies continue to enact legislation to increasingly reduce this source of pollution. In fact, new legislation is scheduled for enactment in the next few years that will affect millions of plastic fuel tanks made each year for various non-automotive applications. Existing technologies for increasing the fuel-barrier properties appear to not be sufficiently effective for all of these tanks. Fluoro-Seal has developed two different types of technologies for significantly increasing the barrier properties of plastic fuel tanks. The company is working with tank manufacturers and plastic resin suppliers to optimize these technologies. With the combination of these two different approaches, the company is confident that all types of plastic fuel tanks, independent of the molding process used to make them, can be made compliant with new evaporative loss regulations.