Long term fuel and heat aging of low temperature types of fluoroelastomers.Automotive industry The automotive industry is the industry involved in the design, development, manufacture, marketing, and sale of motor vehicles. In 2006, more than 69 million motor vehicles, including cars and commercial vehicles were produced worldwide. demands on rubber sealing components have been escalating, especially recently. In 2004, these demands jumped once again when new environmental regulations from California's Air Resource Board and the Environmental Protection Agency Environmental Protection Agency (EPA), independent agency of the U.S. government, with headquarters in Washington, D.C. It was established in 1970 to reduce and control air and water pollution, noise pollution, and radiation and to ensure the safe handling and went into effect. These new regulations, called LEV II and Tier II, respectively, require lower evaporative evaporative pertaining to evaporation. evaporative loss loss of body water by evaporation of water from the body to the air; a heat control mechanism and a factor in water balance studies. emissions on all automotive vehicles, while increasing the longevity longevity (lŏnjĕv`ĭtē), term denoting the length or duration of the life of an animal or plant, often used to indicate an unusually long life. of the systems on the car to 15 years or 240,000 kilometers (150,000 miles) of use (ref. 1). Specialty elastomers, such as low temperature fluoroelastomers, are needed to meet this combination of low emissions with long part life. The objective of this article is to investigate both the long-term fuel and heat resistance of low temperature fluoroelastomers. Polymers such as FKM-GLT and FKM-GFLT are well known in the industry for their combination of good fuel, heat and compression set resistance coupled with improved low temperature flexibility for a fluoroelastomer. GLT GLT Gestion Logistique et Transport (French) GLT Global Leadership Team GLT Golden Lion Tamarin GLT Großladungsträger (German) GLT Guided Light Transit GLT Grundlagentraining and GFLT, made by conventional technology, have been upgraded by advanced polymer architecture (APA (All Points Addressable) Refers to an array (bitmapped screen, matrix, etc.) in which all bits or cells can be individually manipulated. APA - Application Portability Architecture ) technology to GLT-S and GFLT-S. This has been documented in previous papers (refs. 2-4). In addition, a new type of low temperature FKM FKM Fluoroelastomer FKM Fogarty Klein Monroe (Houston, Texas) FKM Field Kitchen, Modular called GBLT-S has been introduced (ref. 5). In this article both the conventional and the advanced polymer architecture technology types were tested side-by-side to compare resuits following this rigorous test protocol. Experimental Materials tested Five low temperature fluoroelastomers were selected for evaluation in this aging study. The FKM types tested were: * GET--64% fluorine fluorine (fl  `ərēn, –rĭn), gaseous chemical element; symbol F; at. no. 9; at. wt. 18.998403; m.p. −219.6°C;; b.p. −188.14°C;; density 1. copolymer copolymer: see polymer. of V[F.sub.2]-PMVE-TFE with a
conventional peroxide peroxide (pərŏk`sīd), chemical compound containing two oxygen atoms, each of which is bonded to the other and to a radical or some element other than oxygen; e.g. cure site included. This is the original low
temperature FKM polymer used to meet specifications such as AMS-R-83485.* GLT-600S--64% fluorine copolymer of V[F.sub.2]-PMVE-TFE made with APA technology. Improved peroxide cure site included. Referred to as GLT-S in the text. * GBLT-600S--66% high fluorine copolymer of V[F.sub.2]-PMVE-TFE made with APA technology. Improved peroxide cure site included. Referred to as GBLT-S in the text. * GFLT--67% high fluorine copolymer of V[F.sub.2]-PMVE-TFE with a conventional peroxide cure site monomer monomer (mŏn`əmər): see polymer. monomer Molecule of any of a class of mostly organic compounds that can react with other molecules of the same or other compounds to form very large molecules (polymers). . Used to meet specifications such as GM6269M, Ford M2D M2D Made to Deceive (camouflage) M2D Modular Mini Display 401-A3 and Daimler-Chrysler MSBZ-832-Grade F. * GFLT-600S--67% high fluorine copolymer of VF2-PMVE-TFE made with APA technology. Improved peroxide cure site included. Referred to as GFLT-S in the text. Testying matrix and details' Each of the five fluoroelastomers was mixed in a laboratory internal mixer mixer, either of two electronic devices in which two or more signals are combined. In the type of mixer used in radio receivers, radar receivers, and similar systems, a signal is translated upward or downward in frequency. into a standard 30 MT black recipe, as shown in table 1. Slabs were cured five minutes at 177[degrees]C in a compression mold. The conventional technology polymers, GLT and GFLT, were then postcured in an air circulating cir·cu·late v. cir·cu·lat·ed, cir·cu·lat·ing, cir·cu·lates v.intr. 1. To move in or flow through a circle or circuit: blood circulating through the body. 2. oven for 16 hours at 232[degrees]C, whereas the advanced polymer architecture products were postcured for only four hours at 232[degrees]C. Tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. samples were then cut and either immersed im·merse tr.v. im·mersed, im·mers·ing, im·mers·es 1. To cover completely in a liquid; submerge. 2. To baptize by submerging in water. 3. in fuel as specified or aged in a hot air oven as noted. Testing was done at several time intervals so trends could be noted. Test fuels used were CM-15A and sour fuel (PN 180). CM15A is a blend of 85% fuel C with 15% methanol methanol, methyl alcohol, or wood alcohol, CH3OH, a colorless, flammable liquid that is miscible with water in all proportions. Methanol is a monohydric alcohol. It melts at −97. . The methanol was contaminated contaminated, v 1. made radioactive by the addition of small quantities of radioactive material. 2. made contaminated by adding infective or radiographic materials. 3. an infective surface or object. with "aggressive" water, which has trace amounts of salts such as sodium chloride sodium chloride, NaCl, common salt. Properties Sodium chloride is readily soluble in water and insoluble or only slightly soluble in most other liquids. It forms small, transparent, colorless to white cubic crystals. , sodium sulfate sodium sulfate, chemical compound, Na2SO4. It is a white, orthorhombic crystalline compound at ordinary temperatures; above 100°C; it assumes a monoclinic structure, and above about 250°C; it assumes a hexagonal structure. and formic acid formic acid or methanoic acid (mĕth'ənō`ĭk), HCO2H, a colorless, corrosive liquid with a sharp odor; it boils at 100.7°C; and solidifies at 8.4°C;. . Five ml of aggressive water was added to one liter of methanol, which was then blended with the fuel C when the fuels were prepared for testing. During the 5,000 hour aging with CM-15A, the fuel was changed weekly. Aging was done in a Parr pressure vessel Pressure vessel A cylindrical or spherical metal container capable of withstanding pressures exerted by the material enclosed. Pressure vessels are important because many liquids and gases must be stored under high pressure. placed in a friction air oven at 60[degrees]C. Tensile testing was done after time intervals of 168, 672, 2,000, 3,000, 4,000 and 5,000 hours. The sour fuel was made by using an 80% fuel C/15% methanol/5% tbutyl alcohol blend with copper ion and t-butyl hydroperoxide added to increase the peroxide number to 180. Sour fuel aging was also done in a Parr pressure vessel placed in a friction air oven at 60[degrees]C. More details on the preparation of the test fuels and conditions can be seen in various Ford documents (ref. 6). Results and discussion After the slabs of the five FKM test compounds were cured and postcured, they were tested for original physical properties. The results of that testing can be seen in table 2. The results show that the FKM compounds are all nominally 70 durometer. The tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its of the conventional technology GLT and GFLT was higher than that of the APA technology GLT-S, GBLT-S and GFLT-S. The elongation elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the planet as measured from the earth. of the APA technology compounds was higher and the 100% modulus See modulo. was lower. These trends in physical properties have been observed before when comparing conventional and APA technology peroxide cured FKM (ref. 3) and were not unexpected. Compression set resistance was tested on plied plied 1 v. Past tense and past participle of ply1. discs cut from the same slabs, and can be seen in table 2 as well. In this test, the APA technology GLT-S, GBT-S and GFLT-S showed superior performance with lower compression set values than the conventional low temperature FKM GLT and GFLT types. Long term fuel immersion immersion /im·mer·sion/ (i-mer´zhun) 1. the plunging of a body into a liquid. 2. the use of the microscope with the object and object glass both covered with a liquid. The five low temperature FKM compounds were immersed for 360 hours at 60[degrees]C in sour fuel (PN180), then tested. The results are shown in figure 1. The lower fluorine GET and GET-S tended to have the biggest tensile and elongation changes and higher volume swell
Roughly speaking, the sound of a guitar note is characterised by an initial 'attack' where the pick or nail produces higher pitched , whereas the higher fluorine GBLT-S, GFLT and GFLT-S had slightly lower property changes and lower volume swell. [FIGURE 1 OMITTED] The performance of conventional technology GLT and GFLT was quite similar to that of APA technology GLT-S, GBLT-S and GFLT-S. The volume swell coupons were examined after the sour fuel testing and no sign of cracks, a common failure mode with many fuel resistant elastomers, was seen in any of the samples. Next, the performance of the five low temperature peroxide cured FKMs was evaluated in CM15A. As previously mentioned, CM-15A is a blend of 85% fuel C with 15% methanol which has some trace salt water contaminates. Figure 2 graphically shows on a bar chart the volume swell of GLT, GLT-S, GBLT-S, GFLT and GFLT-S, respectively, after 168, 672, 2,000, 3,000, 4,000 and 5,000 hours of immersion in the CM15A fuel. The data indicate that GLT and GLT-S swelled 38% to 42% throughout the test, with GLT-S showing a bit higher swell. The 66% fluorine GBLT-S shows a lower swell of ~25% swell, and 67% fluorine GFLT and GFLT-S show the lowest swell of ~22% for both types. The data indicate that the swell properties of conventional and APA technology polymers are quite similar throughout the entire 5,000 hour test period. [FIGURE 2 OMITTED] Hardness or durometer change is another physical phenomona that occurs when elastomers swell in fuel. Figure 3 shows the hardness change of the five FKMs after 168, 672, 2,000, 3,000, 4,000 and 5,000 hours of immersion in the CM15A fuel. In this case, it is interesting to note that the APA technology polymers GLT-S and GFLT-S tend to have less hardness loss than their conventional technology counterparts. [FIGURE 3 OMITTED] The tensile and elongation percentage changes of the five FKM polymers are shown in a series of line graphs In graph theory, the line graph L(G) of an undirected graph G is a graph such that
[FIGURE 4 OMITTED] The elongation results in figure 5 show that both GLT and GLT-S lose about 45% of their elongation in hot CM15A fuel early in the test, then stabilize and remain fairly constant throughout the remainder of the 5,000 hour immersion. When the fuel aged samples were placed in an oven and dried for four hours at 100[degrees]C, the elongation recovered to near the original value for samples of both types. The volume swell coupons for both compounds were visually examined and flexed after the 5,000 hour immersion, and no degradation of any kind was noted. [FIGURE 5 OMITTED] The CM15A fuel immersion tensile and elongation results for the higher fluorine GBLT-S, GFLT and GFLT-S are shown in figures 6 and 7. All three higher fluorine, low temperature polymers show a ~60% loss in tensile strength early in the test that stabilizes and stays fairly constant throughout the remainder of the 5,000 hour immersion. However, when the fuel aged tensile samples were placed in an oven and dried for four hours at 100[degrees]C, the tensile strength recovered to less than a ~20% loss. The trends seen in tensile results for the three polymers are quite similar. While not included in the data here, the hardness and volume swell of the samples after they were dried four hours was measured. It was noted that there was still some volume swell of the polymers after drying (in the range of 2-3%) indicating that four hours at 100[degrees]C was not enough time to completely dry out the samples. [FIGURE 6 & 7 OMITTED] The elongation results in figure 7 show that GFLT, GFLTS and GBLT GBLT Gay, Bisexual, Lesbian, or Transgender lose about 35% elongation in hot CM15A fuel early in the test. In this case, the GFLT recovers to about a 20% loss and stabilizes, whereas the GFLT-S and the GBLTS stabilize at about a 35% loss of elongation. When the fuel aged samples were placed in an oven and dried for four hours at 100[degrees]C, the elongation recovered to near the original value for all three samples. The volume swell coupons for all three compounds were visually examined and flexed after the 5,000 hour immersion, and no degradation of any kind was noted. In summary, the data indicate that there is an initial plasticizing effect as the fuel swells these FKM polymers that lowers the tensile strength and elongation. However, this effect seems to be substantially reversible reversible, adj capable of going through a series of changes in either direction, forward or backward (e.g., reversible chemical reaction). reversible hydrocolloid, n See hydrocolloid, reversible. when the fuel aged tensile samples are then dried for four hours at 100[degrees]C; as the % loss in tensile is ~25% and elongation returns close to original values. This would suggest that the fuel immersion had limited long-term effect on any of the five low temperature FKM polymers tested. Long-term heat aging Another attribute of FKM polymers is excellent heat resistance. One of the ways of evaluating heat resistance is ISO (1) See ISO speed. (2) (International Organization for Standardization, Geneva, Switzerland, www.iso.ch) An organization that sets international standards, founded in 1946. The U.S. member body is ANSI. test method 2578, in which aging is conducted at various temperatures that challenge the polymer being tested. Results of this type of testing have already been published (ref. 7), but not for all five of the low temperature FKM products that were evaluated in the fuel aging section of this article. Figure 8 shows the % retained tensile strength of GLT, GLT-S, GBLT-S, GFLT and GFLT-S after they were aged 5,000 hours in an air circulating oven at 175[degrees]C. The log chart shows that the five FKM polymers retain 90-100% of their original tensile strength after this long-term heat aging. [FIGURE 8 OMITTED] Figure 9 shows the % retained elongation of the same five FKM polymers after they were aged 5,000 hours at 175[degrees]C. In this case, the log chart shows that the five FKM polymers tend to gain some elongation toward the end of the 5,000 hour heat aging. [FIGURE 9 OMITTED] Figure 10 shows the % retained tensile of GLT, GLT-S, GBLT-S, GFLT and GFLT-S after heat aging 5,000 hours at 200[degrees]C. The log chart shows that the five FKM polymers retain most of their tensile strength through 1,000 hours of aging then undergo a gradual decline through the 5,000 hour test period, ultimately retaining approximately 65-85% of their tensile strength after this long term heat aging. [FIGURE 10 OMITTED] Figure 11 shows the % retained elongation of the same five FKM polymers after they were aged 5,000 hours at 200[degrees]C. In this case, the log chart shows that the five FKM polymers are gaining elongation after approximately 1,000 hours of aging. In all cases except GFLT, the five FKMs gained more elongation toward the end of the 5,000 hour heat aging, with values of 1.2 to 1.8 times the original elongation before the aging started. [FIGURE 11 OMITTED] Figure 12 shows the % retained tensile of GLT, GLT-S, GBLT-S, GFLT and GFLT-S after they had been aged 5,000 hours at 232[degrees]C. The log chart shows that the five FKM polymers lose ~50% of their tensile strength somewhere between 2,000-3,000 hours into this demanding 5,000 hour heat aging test. Samples tested after aging 5,000 hours have between 15-35% of their original tensile strength remaining. [FIGURE 12 OMITTED] Figure 13 shows the % retained elongation of the same five FKM polymers after they were aged 5,000 hours at 232[degrees]C. In this case, the log chart shows some real differences between polymer types. The lower fluorine GLT and GLT-S tend to lose more than 50% of their elongation between 2,000-3,000 hours, and they continue to lose elongation until less than 10% is remaining after 5,000 hours. On the other hand, the higher fluorine GBLT-S, GFLT and GFLT-S tend to gain elongation until 2,500 hours into the test, then they start to lose elongation, but still maintain at least 90% of their original elongation after aging for 5,000 hours at 232[degrees]C. [FIGURE 13 OMITTED] In summary, the APA technology GLT-S, GBLT-S and GFLT-S heat age comparably to conventional technology GLT and GFLT. All of these FKMs show a tendency to gradually lose tensile strength, especially at 200[degrees] and 232[degrees]C. All the FKM polymers gain elongation after aging for 5,000 hours at 175[degrees]C and 200[degrees]C. When aged at 232[degrees]C, most of the samples show a similar initial gain in elongation until a certain threshold is reached where embrittlement Embrittlement A general set of phenomena whereby materials suffer a marked decrease in their ability to deform (loss of ductility) or in their ability to absorb energy during fracture (loss of toughness), with little change in other mechanical properties, such takes over and the polymers lose elongation as they get brittle (jargon) brittle - Said of software that is functional but easily broken by changes in operating environment or configuration, or by any minor tweak to the software itself. Also, any system that responds inappropriately and disastrously to abnormal but expected external stimuli; e. . This mode of heat aging is quite similar to what one sees with the heat aging of bisphenol-cured terpolymers such as Viton B. The higher fluorine, low temperature types, GBLT-S, GFLT and GFLT-S, maintain their elongation longer when heat aged at 232[degrees]C as compared to lower fluorine GLT and GLT-S. Low temperature properties Much of the long-term testing reviewed here has been on low temperature FKM types, so it seems appropriate to review the low temperature properties of the five polymers tested in the long-term fuel and heat aging. Figure 14 shows the temperature retraction In the law of Defamation, a formal recanting of the libelous or slanderous material. Retraction is not a defense to defamation, but under certain circumstances, it is admissible in Mitigation of Damages. Cross-references Libel and Slander. (TR-10) and glass transition (Tg) measured by a DSC (1) (Digital Signal Controller) A microcontroller and DSP combined on the same chip. It adds the interrupt-driven capabilities normally associated with a microcontroller to a DSP, which typically functions as a continuous process. See microcontroller and DSP. for conventional technology GLT and GFLT, as well as APA technology GLTS GLTS Greater Lawrence Technical School (Andover, MA) GLTS Great Lakes Transcription Services (Bay City, Michigan) GLTS Green Light Technology Solutions, Inc (Midlothain, Texas) , GBLT-S and GFLT-S. The general trend observed is that the APA technology GLT-S and GFLT-S show a modest improvement in low temperature properties compared to GLT and GFLT. GBLT-S is well positioned between these products, with a TR-10 of -27[degrees]C and a Tg of -28[degrees]C. [FIGURE 14 OMITTED] Conclusions In conclusion, peroxide cured APA technology types of Viton fluoroelastomer are now available in both standard and low temperature grades. Extensive long-term testing has been conducted and the results show: * APA technology GLT-S, GBLT-S and GFLT-S show similar volume swell and physical property retention as conventional technology GLT and GFLT when aged in: --sour gasoline gasoline or petrol, light, volatile mixture of hydrocarbons for use in the internal-combustion engine and as an organic solvent, obtained primarily by fractional distillation and "cracking" of petroleum, but also obtained from natural gas, by (PN180) at 60[degrees]C for 360 hours; --CM15A fuel at 60[degrees]C for 5,000 hours; and --dry out properties after CM 15A fuel immersion. * APA technology GLT-S, GBLT-S and GFLT-S show similar heat resistance properties as conventional technology GLT and GFLT when aged for: --5,000 hours at 175[degrees]C in dry heat; --5,000 hours at 200[degrees]C in dry heat; and --5,000 hours at 232[degrees]C in dry heat. * Higher fluorine GBLT-S, GFLT and GFLT-S show better long-term retention of elongation when heat aged 5,000 hours at 232[degrees]C than do lower fluorine GLT and GLT-S * Compared to their conventional technology counterparts APA technology low temperature polymers GLT-S, GBLT-S and GFLT-S show: --better compression set resistance at 200[degrees]C; --better retention of hardness after fuel immersion; and --slightly better low temperature TR-10 and Tg. Results presented here may not be indicative of the performance of other low temperature fluoroelastomers that were not tested in this program. References (1.) T. Cackette, California Air Resources Board California Air Resources Board (CARB) is the "clean air agency" of the state of California in the United States. Established originally in 1967, it is a part of the California Environmental Protection Agency, an organization which reports directly to the California , "On the road to clean air--zero and near zero evaporative emissions," SAE/ DuPont Fuel Systems Luncheon, March 5, 2002. (2.) R.D. Stevens and D.L. Lyons, "New, improved processing HFP-peroxide cured types of Viton," Rubber Division, ACS (Asynchronous Communications Server) See network access server. , October 2001. (3.) R.D. Stevens and D.L. Lyons, "New improved processing PMVE-peroxide cured types of Viton, "Rubber Division, ACS, October 2001. (4.) Dr. Stephen Bowers Bowers is a surname, and may refer to
adj. Capable of being cured or healed. specialty fluoroelastomers with significant improvements in processability and physical properties," The Brazilian Rubber Congress, November, 2001, Sao Paulo, Brazil. (5.) R.D. Stevens, SAE sae abbr (BRIT) (= stamped addressed envelope) → sobre con las propias señas de uno y con sello paper 2002-01-0632, "New fluoroelastomer for fuel system seals," March 2002. (6.) Ford document "Hose/tube constructions and materials qualifie for LEVII and future fuel applications," document includes Ford test methods AZ 105-02 and BZ 105-03. (7) R.D. Stevens, "Long-term heat aging of various fluoroelastomers, "Rubber Division, ACS, October. 2002. Ronald D. Stevens, DuPont Performance Elastomers
Table 1--recipes for low temperature FKM
compounds in 5,000 hour test matrix
GLT GLT-S GBLT-S GFLT GFLT-S
DD1992 control control
compound # A44-01 A44-02 A44-03 A44-04 A44-05
GLT 100 -- -- -- --
GLT-600S -- 100 -- -- --
GBLT-600S -- -- 100 -- --
GFLT -- -- -- 100 --
GFLT-600S -- -- -- -- 100
Zinc oxide 3 3 3 3 3
MT black (N990) 30 30 30 30 30
Diak 7 (TAIC) 3 3 3 3 3
Varox[R] DBPH-50 3 2 2 3 2
Total phr 139 138 138 139 138
Table 2--original physical properties of
LT polymers
GLT GLT-S GBLT-S GFLT GFLT-S
DD1992 control control
compound # A44-01 A44-02 A44-03 A44-04 A44-05
Postcure time: 16 hr. 4 hr. 4 hr. 16 hr. 4 hr.
Physical properties @ R.T.--original
(cure 5' @ 177[degrees] C--postcure @ 232[degrees] C as noted)
M-25, MPa 1.2 1.3 1.3 1.4 1.3
M-100, MPa 6.1 3.7 4.6 8.8 5.5
Tensile, MPa 21.7 17.5 17.1 20.3 17.7
(Tb, psi) 3,139 2,539 2,475 2,945 2,565
Elongation, % 205 290 245 166 223
Hardness, A, pts. 69 68 71 71 71
Compression set, method B, plied
70 hrs. @ 200[degrees]C 31 23 20 39 19
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