Compatibility of sealing materials with biodiesel, bioethanolgasoline and biodiesel-heating oil blends

摘要

Biofuels including ethanol and biodiesel (fatty acid methyl ester) represent an important renewable fuel alternative to petroleum-derived transport fuels. Materials compatibility is a major concern whenever the fuel composition is changed in a fuel system. The aim of this work is to study the interaction between sealing materials such as FKM (fluorocarbon rubber), EPDM (ethylene-propylene-diene rubber), CR (chloroprene rubber), CSM (chlorosulfonated polyethylene), NBR (acrylonitrile-butadiene rubber), IIR (butyl rubber), VMQ (methyl-vinyl-silicone rubber) and FVMQ (methylfluoro- silicone rubber) and biofuels such as biodiesel, E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel) at 70°C for 84 days. Experiments were conducted with tests specimens of these elastomers to document the changes in the mass and tensile properties of these sealing materials according to ISO 1817. The exposure tests of the elastomers in E85 showed that the weight gain caused by swelling of the test specimens was in the range of 3% to 12%. However, the weight gain of the fluorinated elastomers was at the lower end of this range. Tensile strength and breaking elongation decreased by 22% to 61% or 13% to 77%. The lowest decrease was determined for FKM, VMQ und IIR. These sealing materials were evaluated as resistant to E85 up to a temperature of 70°C. Biodiesel absorbed water more quickly and aged faster than conventional diesel fuel. The weight gain of the elastomers varied between 9% (FKM) and 138% (CR) in biodiesel. FKM was evaluated as resistant with a 16% reduction in tensile strength, a 2% reduction in breaking elongation and low weight loss. NBR, EPDM, CR, IIR, CSM and VMQ were evaluated as not resistant. CR even lost 100% of its original tensile strength and breaking elongation. The highest weight gain as a result of swelling was measured for CR with 240%, IIR with 190%, CSM with 86%, EPDM with 84% and VMQ with 54% in B10, while the fluorine-containing elastomers FKM (1%) and FVMQ (3%) absorbed much less B10 and swelled less. FKM lost 23% in tensile strength and 17% in breaking elongation, and FMVQ lost 29% in tensile strength and 36% in breaking elongation. FMVQ was, therefore, only limited in its resistance to B10. The elastomers NBR, EPDM, CR, CSM, IIR and VMQ were not resistant to B10 at all as the decrease in the tensile properties was significantly over 50%. NBR lost about 93% and CR and CSM about 100% of their breaking elongation. The conclusion of the investigations at 70°C is that FKM is the most resistant sealing material in biodiesel, E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel).