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Biofuels including ethanol and biodiesel (fatty acid methyl ester) represent an impor-tant renewable fuel alternative to petroleum-derived transport fuels. Increasing bio-fuel use would bring some benefits, such as a reduction in oil demands and green-house gas emissions, and an improvement in air quality.
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 (chloro-prene rubber), CSM (chlorosulfonated polyethylene), NBR (acrylonitrile-butadiene rubber), IIR (butyl rubber), VMQ (methyl-vinyl-silicone rubber) and FVMQ (methyl-fluoro-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 con-ducted with tests specimens of theses 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 at 70°C 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 in the tensile properties was determined for FKM, EPDM 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 loss of the elastomers varied between 9% (FKM) and 126% (CSM) 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, CSM and VMQ were evaluated as not resistant. CSM even lost 84% of its original tensile strength and 78% of its breaking elongation.
The highest weight gain as a result of swelling was measured for CSM with 86%, for EPDM with 84% and for VMQ with 54% in B10, while the fluorine-containing elasto-mers FKM (1%) and FVMQ (3%) absorbed much less B10 and swelled less. FKM lost 23% in tensile strength and 17% in breaking elongation; FMVQ lost 29% in ten-sile strength and 36% in breaking elongation. FMVQ was, therefore, only limited in its resistance to B10.
The elastomers NBR, EPDM, CSM 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 CSM about 100% of its 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).
Materials compatibility is a major concern whenever the fuel composition is changed in a fuel system. Therefore frequently used sealing materials such as FKM (fluorocarbon rubber), FVMQ (methyl-fluoro-silicone rubber), VMQ (methyl-vinyl-silicone rubber), EPDM (ethylene-propylene-diene rubber), CR (chloroprene rubber), CSM (chlorosulfonated polyethylene), IIR (butyl rubber), PA (polyamides), N8R (acrylonitrile-butadiene rubber) and PUR (polyester urethane rubber) were exposed to E1 0, diese I fuel with 5% biodiesel, non-aged and 2 year aged 810 (heating oil with 10% biodiesel), and for comparison to pure diese! fuel, standard heating oil and Super plus without bioethanol at 20 °C, 40 oc and 70 oc for 84 days. Mass, tensile strength and breaking elongation of the test specimens were determined before and after the exposure. The visual examination of some elastomer test specimens clearly showed the great volume increase until break or partial dissolution. Shore hardness A and D (for PA) were determined before and after exposure of the test specimens to the biofuels for 42 days.
There is not determined a threshold for the reduction in tensile properties and Shore hardness in the international standards. Therefore a threshold of 15% was determined for the evaluation of the compatibility.
The sealing materials FKM, EPDM, N8R, FMVQ, CSM and PA were evaluated on the basis of this threshold as resistant in E1 0 at 20 oc and 40 °C. FKM, FVMQ and PA were resistant at 40 oc , and none of the materials were resistant at 70 °C. FKM and FVMQ absorbed much less 810 and swelled less. CR, CSM, EPDM, IIR, N8R and VMQ were not resistant to 810 at all at 20 oc, 40 oc and 70 oc as the decrease in the tensile properties was significantly over 50%. FVMQ and PA could be evaluated as resistant in non-aged and two year aged 810 at 20 oc and 40 oc, whereas FKM was resistant up to 70 °C. FKM, PA and PUR were evaluated as resistant in standard heating oil and pure diese! fuel at temperatures up to 40°C, only FKM was resistant up to 70°C. FVMQ, FKM, N8R, VMQ, CR and IIR can be evaluated as resistant in premium grade fuel Super plus without ethanol at 20 oc. FKM, FVMQ, VMQ and IIR were still resistant at 40 °C. FKM and FVMQ were evaluated as resistant with restrictions at 70 °C.
ln summary, it can be therefore stated that the chemical resistance of the fluoropolymers FKM and FVMQ in fuels and biofuels is the best one.
Biofuels represent an important renewable fuel alternative to petroleum-derived transport fuels. Materials compatibility is a major concern whenever the fuel composition is changed. The aim of this work is to study the interaction of the elastomers: FKM, EPDM, CR, CSM, NBR, IIR, VMQ and FVMQ and biofuels such as biodiesel (FAME), E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel). Exposure tests were performed with test specimens at 40°C (104°F) and 70°C (158°F) for 84 days to document the changes in mass, volume and tensile properties according to ISO 1817. The exposure tests in E85 showed that the weight gain caused by swelling was in the range up to 12%. The lowest decrease in the tensile properties was determined for FKM, VMQ and IIR. The weight gain of the elastomers in biodiesel varied between 10% (FKM) and 126% (CSM) and the loss of tensile strength between 16% (FKM) and 100% (CSM) at 70°C (158°F). FKM and FVMQ absorbed much less B10 and swelled less. 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%. Among all of the elastomers FKM showed high compatibility with these biofuels up to 70°C (158°F).