Blow molding HDPE fuel tank

In South Africa, owing to the diversity and small production volume of specific motor car models, it is not economically feasible to blow-mold HDPE fuel tanks. The only cost-effective plastic tank manufacturing process used in South Africa is rotational molding, using LLDPE with a density of 0.939 g/cm3. Some selected properties of LLDPE before and after petrol exposure are compared to HDPE in Table 16.2. It is clear that owing to weaker mechanical properties, LLDPE is far less suitable than HDPE for petrol containment, mainly because of its lower crystallinity. 

Plastic-based fuel tanks were first used in Volkswagen Passat in 1972, and since then the interest in using these tanks in vehicles has been on the rise [10]. When high-density polyethylene (HDPE) fuel tanks were initially used, fluorination was observed to reduce fuel permeation permeation resistance was then increased over the years by the invention of a coextrusion blow-molding process [109]. HDPE... 

Plastic Automotive Fuel Tanks. The North American auto industry is converting to plastic automotive fuel tanks from blow-molded HDPE. The advantages of HDPE tanks over the usual steel tanks are no corrosion, lighter than steel, easily shaped to fit in the car, and more puncture resistant than steel. However, the HDPE tanks suffer from high permeability to liquid gasoline. 

Blow molding uses compressed air to blow and expand a hot plastic tube ( rubbery melt ) in a female mold cavity, until the plastic conforms to the walls of the mold. This has developed into a major way to produce plastic bottles, and also more specialized hollow shapes such as fuel tanks, seat backs, tricycles, surfboards, and so on. The leading material is HDPE for milk, water, and household chemicals. Second largest is PET for carbonated beverages. A number of other thermoplastics are blow molded in smaller amounts for more specialized uses. 

Major markets for LDPE are in packaging and sheeting, whereas HDPE is used mainly in blow-molded products (milk bottles, household and cosmetic bottles, fuel tanks), and in pipe, wire, and cable applications. Ultra-high-molecular-weight polyethylene materials (see later), which are the toughest of plastics, are doing an unusual job in the textile machinery field. 

A major use for HDPE is in blow molding applications. Large containers or drums (for example, of 180 litres/45 gallons capacity) toys and car components (fuel tanks and spoilers) are typical applications. HDPE is used in such applications because of its high impact strength and, because it can retain its properties at low temperatures, for example, -18° C (-0.4° F). To obtain the required properties in the finished product (for example, strength and creep resistance), it is... 

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