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Biofuels including ethanol and biodiesel (fatty acid methyl ester) represent an important renewable fuel alternative to petroleum-derived transport fuels. Increasing biofuel use would bring some benefits, such as a reduction in oil demands and greenhouse 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 question arises of whether sealing materials are resistant to fuels with bioethanol and biodiesel (rapeseed oil fatty acid methyl ester).
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), FVMQ (methyl-fluoro-silicone rubber) and PA (polyamide) and biofuels such as biodiesel (FAME, non-aged and 2 years aged), E85 (fuel with 85% ethanol) and B10 (heating oil with 10% biodiesel, non-aged and one year aged) compared with premium-grade fuel at 20°C, 40°C and 70°C for 84 days. Exposure experiments were conducted with specimens of these elastomers to document the changes in the mass and tensile properties of these sealing materials. Visual examination of some test specimens clearly showed a great volume increase until breakage or partial dissolution.
The sealing materials FVMQ, VMQ and PA were evaluated as resistant in E85 at 20°C and 40°C with a reduction of tensile properties limited to 15%. None of the examined materials was evaluated as resistant at 70°C with even fluorocarbon rubber losing 20% of its tensile strength in E85.
When exposed to biodiesel, elastomers were affected in two ways: firstly, by absorption of liquid by the elastomers and, secondly, by dissolution of soluble components from the elastomers into the liquid medium. Swelling was the result of the high absorption by the elastomers CR, CSM, EPDM, IIR and NBR in comparison to their dis-solution in non-aged and two years aged biodiesel. FKM, VMQ and PA were evaluated as resistant sealing materials in non-aged biodiesel at 40°C. FKM was still resistant in aged biodiesel at 40°C but only to a limited degree at 70°C.
The sealing materials CR, CSM, EPDM, IIR, NBR and VMQ were damaged to a high extent in non-aged and one year aged B10 as a result of swelling up to 70°C. FVMQ and PA can be evaluated as resistant in non-aged and one year aged B10 at 20°C and 40°C. However, FKM was evaluated as resistant up to 70°C.
The exposure tests showed that all the elastomers tested were resistant in the premium-grade fuel Super at 20°C. On increasing the temperature to 40°C, only FKM, VMQ and PA were resistant to Super. At 70°C FKM showed the best resistance.
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).