Jamak Develops Fiber Reinforced Elastomer for Oil and Gas use

Fiber Reinforced Silicone Elastomers for Oil & Gas Uses Carl McAfee â McAfee Consulting LLC & Mike Dulisse â Jamak Fabrication Paper presented to the Energy Rubber Group at the Winter Meeting - 19 Jan 2012 â Houston, TX Abstract Silicone elastomers have been known to have a broad temperature range and reasonable chemical resistance. Their strength properties have been considerably less when compared to other elastomer types in general use in oil & gas applications like hydrogenated nitriles and fluoroelastomers. A design of experiment methodology was used to formulate a fiber reinforced silicone elastomer with significantly enhanced strength properties. The new compound was compared to typical hydrogenated nitrile and fluoroelastomer compounds in use today in the oil & gas industry. Physical properties, chemical resistance, rapid gas decompression, extrusion resistance, and dynamic properties were evaluated and are reported in this paper for consideration. After reviewing the data, fiber reinforced silicone elastomers are a realistic option for oil & gas applications and offer a good value option for high temperature/high pressure applications where temperature, chemical resistance, strength, and dynamic performance at temperature are critical requirements. Introduction Silicone elastomers have a broad temperature operating range generally ranging from -60 C to 200 C. Silicone elastomers also have considerably good chemical resistance to many substances of interest for oil & gas applications. Chemical resistance is rated excellent for natural gas, ozone, methanol, IRM #901 Oil, methyl alcohol, propyl alcohol, and sodium hydroxide. Chemical reistance is rated fair for IRM #903 Oil. Strength properties have historically been the weak link when considering silicone elastomers for oil & gas applications. Of particular concern have been low strain modulus values which are a critical design parameter in many oil & gas applications. The addition of fibers for reinforcement of the silicone matrix was considered as a possible solution to this historical problem. Materials & Methods A design of experiment method was used to formulate a novel fiber reinforced silicone elastomer compound. A two level, five factor, half fractional design was chosen. The details of the design experiment are important, but are not the main focus of this application based paper. The formulations were prepared, cured, molded, tested, and the data was entered into Design-Expert Version 7 (Stat-Ease, Inc. â Minneapolis, MN) for analysis. The significant factors were chosen, the analysis of variance was established, mathematical models were chosen for the various physical properties as responses, and an optimization using the desirability function was performed. A specific compound was chosen as the basis for all the following comparisons to the other typical elastomer formulations. The following table is given to illustrate the change in typical physical properties of a conventional silicone elastomer compound and the respective fiber reinforced silicone elastomer compound. It is this authorâ s perspective that physical properties are important, but the true performance of a compound should be evaluated in the final application. This is especially true of oil & gas industry applications. ï ® Typical Physical Properties ï ® Elastomer Conv. FRSE ï ® Hardness 58 75 ï ® Tensile 1285 1102 ï ® Tear 114 151 ï ® Elongation 421 347 ï ® 25% Modulus 132 387 ï ® 100% Modulus 1285 1102 ï ® Specific Gravity 1.25 1.19 The chosen formulation was also evaluated for fiber dispersion within the silicone elastomer matrix via a laser confocal digital microscope. Images are given below. It was determined that fiber dispersion was excellent and individual fiber separation was attained. The chosen fiber reinforced silicone elastomer (FRSE) formulation was then compared to a hydrogenated nitrile (HNBR) compound and a fluoroelastomer (FKM) compound. Again, the HNBR and FKM compounds are typical compounds in current use in the oil & gas industry. Physical properties were generated for similar compound hardnesses and are given in the results section. Chemical resistance was evaluated via immersion testing in oilfield related substances. Rapid gas decompression was evaluated at two different locations via two typical methods. Extrusion resistance was tested via an extrusion resistance test with a 0.030â gap. Dynamic properties were evaluated via ASTM D6601 on an Alpha Technologies APA2000. This test method is considered extremely valuable for use in compound evaluation for dynamic purposes at realistic operating temperatures, strain rates, and frequencies typically found in use in the oilfield industry. This test protocol cures the compound then cools the specimen to 100 C and performs a strain sweep at 1 Hz and then again at 10 Hz to evaluate torque, modulus, and tangent delta to simulate higher temperature operating conditions. The specimen is then cooled to 60 C and the strain and frequency protocol is repeated. Results & Discussion The physical properties from molding and testing of the three compounds are given for comparison. The compounds were chosen for similar hardness and typical use in high temperature/high pressure applications and historical success in oil & gas applications. It should be noted that typical physical properties as tested by most labs are at room temperature (25 C). Most applications in the oil & gas industry are far above lab temperature. Application focused testing is critical for oil & gas applications. The following table is given for review and comparison. FRSE physical properties are in the same range. HNBR has overall higher strength properties. FKM has lesser elastic properties but higher temperature resistance and better chemical resistance. FRSE & HNBR have significantly less specific gravities. All have good low strain modulus values which are of particular interest in this study. Elastomer FRSE HNBR FKM ï ® Durometer 83 79 80 ï ® Tensile 1125 3131 1010 ï ® Elongation 350 512 266 ï ® 25% modulus 453 239 303 ï ® 50% modulus 450 302 384 ï ® 100% modulus 464 444 530 ï ® 200% modulus 634 1022 855 ï ® 300% modulus 944 1815 - ï ® Tear 157 275 128 ï ® Specific gravity 1.17 1.19 1.80 All three compounds have good curing properties which make them well suited for most molding and extrusion based application processes for end product manufacturing. ï ® Elastomer Type FRSE HNBR FKM ï ® 4 minutes @ 360 F ï ® ML 2.27 1.69 1.45 ï ® MH 22.89 16.04 12.46 ï ® T2 0.32 0.73 0.69 ï ® T90 1.04 1.84 1.83 ï ® 30 minutes @ 300 F ï ® ML 2.39 1.9 2.06 ï ® MH 22.19 17.76 14.39 ï ® T2 2.07 3.58 2.52 ï ® T90 10.04 12.14 12.12 Rapid Gas Decompression is a critical test for oil & gas applications. There are various methods in place in the industry to study elastomer compounds resistance to fracture under a rapid decompression situation. The appropriate elastomer compound will allow the pressurized gas to escape from the interstitial volume with little to no visible fractures upon inspection after the decompression. Much discussion in the industry and many different gases & pressure release rates have been studied for this important industry test. Results for these three compounds are given below for consideration. The FRSE performed exceptionally well compared to the two industry standards. It is thought that the fibers dispersed throughout the silicone elastomer matrix provide pathways for the compressed gas to escape during the rapid decompression situations. This very important test was conducted at two different oilfield locations using two different gases and decompression protocols. The following pictures are the best way to visualize the results of the rapid gas decompression testing. As all applications require, the best overall solution is one that is the best balance of all the required properties, temperature capabilities, chemical resistance, and application specific requirements. Rapid Gas Decompression ï ® FRSE HNBR FKM ï ® Good Fair Bad ï ® 2 fractures 3 fractures 4 fractures Extrusion resistance of oilfield parts under pressure is another industry specific test that the successful elastomer compound must possess. The following results demonstrate the maximum sustained pressure before the molded part was pushed through a gap of 0.030 inch. Again, the FRSE performed well. Extrusion Resistance Test - 0.030â gap ï ® FRSE Max Pressure 5236 psi ï ® HNBR Max Pressure 4284 psi ï ® FKM Max Pressure 4046 psi The dynamic properties of the three compounds as measured by the ASTM D6601 test method on the APA2000 are given below. The test method gives a tremendous amount of information. Often the challenge is choosing the most appropriate information for the intended application. The authors of this paper have chosen Gâ (Modulus in kPa) at 100 C and 1Hz, tangent delta at 100 C and 1 Hz, and the modulus and tangent delta at 60 C and 1 Hz respectively, as the most significant and informative curves. The respective curves are given below for consideration and evaluation. Condition: 100 C & 1 Hz Condition: 100 C & 1 Hz Condition: 60 C & 1 Hz Condition: 60 C & 1 Hz The dynamic tests were performed in duplicate to illustrate the consistency and reproducibility of the method. It is interesting to note that tangent delta is a good measure of heat buildup. It is expected that elastomer compounds that have low tangent delta values in dynamic applications will have longer product lifetimes before the onset of stress cracking which leads to crack propagation and ultimate part failure. At both the 100 C & 60 C conditions respectively, the FRSE had very good tangent delta values. It is also interesting to note from the modulus values at higher strain rates that all the compound values began to converge. It is proposed that future work take this type of test approach to an even higher temperature condition approaching 150 C to explore the extremes of the three compounds operating range. Conclusions Fiber reinforced silicone elastomer compounds are a viable option for high temperature/high pressure applications in the oil & gas industry. The broad temperature range, good chemical resistance to a variety of oilfield substances, good strength properties, and excellent dynamic performance at temperature, make FRSE compounds a good value to performance option when compared to other elastomer choices. References The following references are given for additional reading and study. -Fiber reinforced elastomers, Dissertation by Larry Peel, BYU, 1998. Web link - users.tamak.edu/kfldp00/research/papers/dissertation.pdf -Performance Fibers â polyester fibers - www.performancefibers.com -UHMwPE fibers from DSM - www.dyneema.com -Series of early patents in 1974 & 1975 Marzocchi, US 3,793,130 Seifert, US 3,914,499 Marzocchi, US 3,864,203 -J.E. Oâ Connor, â Short Fiber Reinforced Elastomer Compositesâ , Rubber Chem Technol., 50 (1977) 945. Acknowledgements The authors would like to acknowledge several people in our industry for their valuable assistance in this work. Thanks also to Al Lewis & Piseth Lov of Oil States Industries in Arlington, Texas for their assistance with the elastomers for comparison and their help with rapid gas decompression and extrusion resistance tests. Thanks to Buc Slay of Halliburton in Carrolton, Texas for his verification of the rapid gas decompression results with the additional method. Contact Information for the Authors Carl McAfee is a chemist and a consultant to the rubber & plastics industry. He founded McAfee Consulting LLC in December 1996 and has been a resource for small to medium sized manufacturers in the rubber & plastics industry for the last 15 years. Carl has a B.S. in Chemistry from Harding University and a Ph.D. in Analytical Chemistry from Texas A&M University. His research interests and recent projects include work in nanomaterials in elastomers, rubber & plastics recycling, composite railroad ties, powdered elastomers in thermoplastics, and novel analytical instrumentation for polymer characterization. Carl can be reached via email at cmcafee@prochemist.com or his company website at www.prochemist.com . Carl is based in the Dallas/Fort Worth area and is available worldwide for consultation & specific projects. Mike Dulisse is an industrial engineer and the current V.P. of Operations at Jamak Manufacturing in Weatherford, TX. Mike studied at UC Riverside from 1976 to 1979. Mike has a background in composites where he started at Carson Industries and was plant manager by 1985. In 1989 he went to ESSEF Corporationâ s filament winding operation in Ontario, CA and later to their Statesville, NC plant for a turnaround. He came to Jamak in 1997 in Illinois to start a filament winding operation for them. In 2003 he was asked to come to Texas. He has focused his last seven years on streamlining the rubber manufacturing operation at Jamakâ s main location in Texas. Mike can be reached via email at midu@jamak.com or his company website at www.jamak.com . Mike is based in Weatherford at Jamak company headquarters and has commercial quantities of FRSE available for new applications.