Materials: Polyoxymethylene for Injection Molded Automotive Fuel Systems

A new polyoxymethylene (POM) grade developed by Japan’s Polyplastics Group (U.S. office in Farmington Hills, Mich.) reportedly delivers improved diesel fuel resistance for the production of injection molded automotive fuel system components. Duracon H140DR is the latest addition to the company’s Duracon POM portfolio which is already widely used for automotive fuel system components due to its superior mechanical properties, heat and fuel resistance, and excellent moldability.

Duracon H140DR is said to offer superior performance over competitive materials and is targeted for global markets. The material has a higher melt flow rate (MFR) than standard grade M90-44, resulting in good formability. It is also denser, with smaller crystal size, and thus has a high degree of crystallization compared to standard grade M90-44.

While drive systems will likely shift toward electrification, it is expected that diesel engines will remain in use for certain commercial vehicles, according to Polyplastics. Low-quality diesel fuel contains a high concentration of acid and sulfur which has a negative effect on POM.  Fuels that contain a high concentration of sulfur act on the main polymer chains and facilitate decomposition in POM.

Tests show the percentage of weight change (rate of decomposition) when POM is immersed at high temperature in diesel test fuel with a high concentration of sulfur. H140DR has been shown to have superior resistance compared to a competitor’s improved diesel fuel-resistant POM and a standard material. The material has the same level of creep-fracture properties versus competitive materials and appears to have enough long-term mechanical resistance properties as well. Environmental stress fracture testing reveals that DH140DR has high resistance to external factors such as acid rain and various acidic solvents used in cars.