Material Compatibility. February 11, 2015 Dr. Jens Ortner

Transcription

1 February 11, 2015 Dr. Jens Ortner

2 Interaction of Fuels with Materials ethanol Nature of interaction Chemical reaction Physical interaction Composition of the fuel Fuel with polar compounds Fuel without aromates Fuel with aromates Type of material Ceramic materials Metals and alloys Synthetic materials / polymers ester n-alkane iso-alkane aromate cycloalkane 2

3 Selection of Synthetic Material Type of synthetic material Thermosetting polymers 3D network, weak interaction and swelling Thermoplastics stronger interaction and swelling; stress corrosion cracking might be a problem especially for amorphous thermoplastic materials thermoplastics are not common in fuel systems Elastomers swelling shows the most significant effect on material properties Investigation of elastomers, which are typical used for O-rings in aviation industry Nitrile-Butadiene-Rubber (NBR) Fluorosilicone Rubber Fluorocarbon Rubber 3

4 Characterisation of Elastomers Most effects can be explained by elastomer composition Nitrile-Butadiene-Rubber (NBR): 44 % polymer (72 % butadiene, 28 % acryl nitrile), 40 % carbon black, 13 % additives, 3% non combustible residue Fluorosilicone Rubber (FVMQ): Consists of short-chained oligomers, no additives (<1 %) or carbon black Fluorocarbon Rubber (FKM): 65 % polymer, 27 % carbon black, no additives (<1 %), non combustible residue 8 % 4

5 Experimental Procedures Compatibility tests with Jet A-1 with vol% aromatics CH kerosene 19.7 vol% aromatics Alternative fuels without aromatics: HVO/HEFA, CTL, ATJ-SPK HVO/HEFA, CTL, ATJ-SPK enriched with 2, 4, 6 and 8 vol% aromatics Subsequent storage in 21.6 vol% Jet A-1 and aromatic-free HVO/HEFA Influence on physical properties Mass } most important properties Volume Hardness Elongation at break Tensile strength 5

6 mass volume Nitrile-Butadiene-Rubber (NBR) Significant mass and volume Correlation with aromatic content Extraction and analysis of incorporated compounds show n- alkanes and iso-alkanes as well Negative mass after storage in aromatic-free fuels indicates extraction of additives (e.g. plasticizer, antioxidants) Aromatic compounds compensate this effect 6

7 hardness Nitrile-Butadiene-Rubber (NBR) Hardness, elongation at break and tensile strength are reduced after storage in fuels containing aromatic compounds elongation at break tensile strength 7

8 mass volume Fluorosilicone Rubber (FVMQ) Moderate mass and volume for all fuels No negative mass no extractable additives No significant influence of aromatic content on mass and volume 8

9 hardness elongation at break Fluorosilicone Rubber Decrease in hardness for all fuels; less prominent for aromatic-free fuels Elongation at break: Limited repeatability (40 units) probably due to defects Tensile strength slightly reduced Break parameters do not correlate with aromatic content tensile strength 9

10 mass Fluorocarbon Rubber (FKM) No mass and volume for all fuels According to standard, all values are rounded to integers volume 10

11 hardness Fluorocarbon Rubber Hardness: No significant s Elongation at break: Small increase Tensile strength: Slight decrease Break parameters do not correlate with aromatic content elongation at break tensile strength 11

12 mass NBR Stored in Model Fuels volume HVO/HEFA, CTL, ATJ- SPK enriched with 2, 4, 6 and 8 vol% aromatics Mass and volume almost linearly depend on aromatic content 12

13 hardness Stored in Model Fuels ATJ-SPK: Hardness correlates with aromatic content CTL: Break parameters are slightly reduced by aromatics elongation at break tensile strength 13

14 Fluorosilicone Rubber Stored in Model Fuels Variations of aromatic content is not reflected in mass and volume, hardness or break parameters volume Fluorocarbon Rubber Stored in Model Fuels No mass and volume No variation of hardness and break parameters with aromatic content hardness 14

15 Subsequent Storage in Fossil and Synthetic Fuel Refuelling with an aromatic-free synthetic fuel (HVO/HEFA) after using a Jet A-1 with high aromatic content (21.6 vol%) Properties of all elastomers do not significantly differ after this twofold storage from those after a single storage in aromatic-free Storage of NBR in fossil fuel leads to an increase and subsequent storage in HVO in a decrease in volume and mass Possible impact on tightness of seals 15

16 Nitrile-Butadiene-Rubber: Summary Mass and volume correlates with aromatic content In aromatic-free fuels, extraction of additives is not compensated by intercalation of fuel molecules additional investigations necessary Hardness and break parameters are hardly affected by aromatic-free fuels Hardness and break parameters significantly decrease in presence of aromatics; no correlation with are aromatic content Fluorosilicone Rubber: Minor increase in mass and volume for all fuels Hardness decreases; more pronounced, if fuels contain aromatics Break parameters in all fuels slightly reduced Fluorocarbon rubber: Widely inert, no significant s 16

17 Summary Nitrile-Butadiene-Rubber stored in model fuels: Mass and volume correlates with aromatic content Hardness and break parameters only hardly affected Fluorosilicone and fluorocarbon rubber stored in model fuels No variation of all parameters Subsequent Storage in Fossil and Synthetic Fuel: All elastomers show the same results as after storage in neat fuels Future Work: Further investigations on the behaviour of NBR Detailed analysis of NBR composition (TGA-IR analysis) GCxGC/MS analysis of incalated and extracted compounds 17