A comparison of CM and CSM with other materials for automotive fuel hose covers.Typical materials currently used for fuel hose covers are chlorinated chlorinated /chlo·ri·nat·ed/ (klor´i-nat?ed) treated or charged with chlorine. chlorinated charged with chlorine. chlorinated acids some, e.g. polyethylene polyethylene (pŏl'ēĕth`əlēn), widely used plastic. It is a polymer of ethylene, CH2=CH2, having the formula (-CH2-CH2-)n (CM), chlorosulfonated polyethylene (CSM CSM - ["CSM - A Distributed Programming Language", S. Zhongxiu et al, IEEE Trans Soft Eng SE-13(4):497-500 (Apr 1987)]. ), acrylonitrile-butadiene rubber/polyvinylchloride blends (NBR/PVC) and epichlorohydrin ep·i·chlo·ro·hy·drin n. A colorless liquid, C3H5OCl, used as a solvent in making resins. terpolymer ter·pol·y·mer n. A polymer that consists of three distinct monomers. [Latin ter, thrice; see trei- in Indo-European roots + polymer.] (GECO GECO Groupe d'Étude en Chirurgie Osseuse GECO Gustave Genschow Co. (German cartridge headstamp) ). The choice of material has become even more important with the increasing demands being placed by smaller, hotter engine compartments In developmental biology, compartments are fields of cells of distinct cell lineage, cell affinity, and genetic identity. In a developing organ, all cells within a compartment possess similar affinities, and so intermingle with each other. and more stringent environmental regulations relating to relating to relate prep → concernant relating to relate prep → bezüglich +gen, mit Bezug auf +acc 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 fuel systems. In general, CSM provides ease of processing, extendability, flexibility in choice of cure systems, and a good balance of heat, oil and abrasion abrasion /abra·sion/ (ah-bra´zhun) 1. a rubbing or scraping off through unusual or abnormal action; see also planing. 2. a rubbed or scraped area on skin or mucous membrane. resistance. CM offers similar performance attributes to the CSM at a lower cost, but is limited in the area of cure system choice. NBR/PVC offers low cost, ease of processing and good fuel resistance, but inadequate heat resistance. GECO offers a good balance of heat, oil and fuel resistance, but comes at a higher cost. This article will compare each of these materials as used in fuel hose cover compounds. It is intended to serve as a relative comparison of the performance characteristics offered by each polymer. For this reason, the compounds tested were not optimized for the application. Instead, within practical limits, every attempt was made to produce comparable original physical properties by using similar loading levels and cure systems. However, inherent differences in polymer characteristics prevented identical use of plasticizer plas·ti·ciz·er n. Any of various substances added to plastics or other materials to make or keep them soft or pliable. plasticizer or -ciser Noun type and level, as well as cure system type and level. Experimental Raw materials Four chemically different polymers were investigated for suitability as fuel hose covers: Chlorosulfonated polyethylene, chlorinated polyethylene, acrylonitrile-butadiene rubber/polyvinyl chloride chloride (klōr`īd, klôr`–), chemical compound containing chlorine. Most chlorides are salts that are formed either by direct union of chlorine with a metal or by reaction of hydrochloric acid (a water solution of hydrogen chloride) blend and epichlorohydrin terpolymer. The trade name and manufacturer of the polymers and the other compound ingredients used are available upon request. Formulations Both 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 systems and sulfur-based cure systems were investigated. The specific formulations used are listed in tables 1 and 2. Typical formulations for hose covers were chosen and all attempts were made to keep formulations approximately equivalent on a parts per hundred basis. Similar loading levels were used in all compounds where possible. Plasticizers plasticizers mostly triaryl phosphates, such as tricresyl, triphenyl phosphates, which are poisonous. See also triorthocresyl phosphate. were chosen based on chemical compatibility with the base polymers, and the most effective antioxidants Antioxidants Substances that reduce the damage of the highly reactive free radicals that are the byproducts of the cells. Mentioned in: Aging, Nutritional Supplements antioxidants, n. for each base polymer were used. Mixing All mixing was carried out in a OOC OOC Out of Character (online role-playing) OOC Out-Of-Character (gaming) OOC Out Of Control OOC Optical (WDM) Overhead Channel OOC Out-Of-Conference OOC Out of Context 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. in a single pass, upside-down mix with accelerators and curatives added at the sweep. The mixer indicated dump temperatures were approximately 100 [degrees] C, corresponding to 120 [degrees] C-130 [degrees] C as measured with a probe inserted in the compound after dumping. The stocks were cooled on a sheet-off mill. Curing Cure characterizations were performed on a moving die rheometer rhe·om·e·ter n. An instrument for measuring the flow of viscous liquids, such as blood. at 160 [degrees] C with a 0.5 [degrees] arc and 30 minute test time. Test slabs were compression molded mold 1 n. 1. A hollow form or matrix for shaping a fluid or plastic substance. 2. A frame or model around or on which something is formed or shaped. 3. Something that is made in or shaped on a mold. at 160 [degrees] C for T95 + 3 minutes as measured by the rheometer. Compression set buttons were cured at 160 [degrees] C for T95+15 minutes as measured by the rheometer. Testing Testing was performed according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. the applicable ASTM ASTM abbr. American Society for Testing and Materials test procedures. Table 3 lists all tests performed, as well as the various aging conditions and test methods employed. Rheological rhe·ol·o·gy n. The study of the deformation and flow of matter. rhe  o·log properties,
heat-aged and oil-aged physical properties, oil swell, subambient
characteristics, sealing properties and resistance to compression set,
abrasion, fuel permeation per·me·a·tionn. The process of spreading through or penetrating, as in the extension of a malignant neoplasm by continuous proliferation of the cells along the blood or lymph vessels. and ozone surface cracking cracking - cracker were all measured. Results and discussion Peroxide cured samples Original physical properties All attempts were made to obtain similar modulus See modulo. , hardness and 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. ; however, inherent differences in polymer characteristics made exact duplication duplication /du·pli·ca·tion/ (doo-pli-ka´shun) 1. the act or process of doubling, or the state of being doubled. 2. impractical im·prac·ti·cal adj. 1. Unwise to implement or maintain in practice: Refloating the sunken ship proved impractical because of the great expense. 2. . Original physical properties for peroxide cured compounds are shown in table 4. Heat resistance A comparison of the heat resistance of the peroxide-cured compounds is shown for various conditions in figures 1-5. After hot air aging for 70 hours at 100 [degrees] C, all compounds exhibited similar modulus retention. However, CM, CSM and GECO exhibit significantly smaller changes in elongation-at-break than the NBR/PVC compounds. [FIGURES 1-5 OMITTED] Clearer separation of performance characteristics of each compound is shown at higher temperatures. After one week at 125 [degrees], the CM exhibited superior heat resistance when compared to the other cover materials, as shown by the comparatively small changes in both modulus and elongation. CSM and GECO followed closely behind, respectively. Both NBR/PVC compounds were extremely stiff after this exposure, as shown by the large loss of elongation and increase in modulus. Such high increases in the modulus of a hose cover compound may lead to early flex crack failure. After 70 hours of exposure to hot air at 150 [degrees] C, the CM again displayed superior heat resistance followed by GECO and CSM, respectively. The NBR/PVC compounds became embrittled at this condition, as shown by the complete loss of elongation. This behavior was anticipated due to unsaturation un·sat·u·rat·ed adj. 1. Of or relating to an organic compound, especially a fatty acid, containing one or more double or triple bonds between the carbon atoms. 2. Capable of dissolving more of a solute at a given temperature. present in the NBR NBR Number NBR Nightly Business Report (PBS show) NBR National Business Review (New Zealand weekly business newspaper) NBR National Bureau of Asian Research NBR National Board of Review backbone. Two long term aging conditions were explored to determine the continuous upper temperature limit (CUTL) of these elastomers as defined by SAE sae abbr (BRIT) (= stamped addressed envelope) → sobre con las propias señas de uno y con sello J2236, Standard Method for Determining Continuous Upper Temperature Resistance of Elastomers. The CUTL is defined as the temperature at which the material retains 50% minimum of both the original elongation and the tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. at break after 1,008 hours in an air-circulating oven. All compounds were exposed to 100 [degrees] C and 125 [degrees] hot air for 1,008 hours. At 100 [degrees] C the CM, CSM and GECO all exceeded the 50% retention requirements. The NBR/PVC compounds, however, once again exhibited elongation loss beyond the acceptable range. At 125 [degrees] C, the CM compound was the only one to exceed the 50% retention of tensile at break and elongation. CSM came very close with a 43% retained elongation and 88% retained tensile at break. Neither the NBR/PVC compounds nor the GECO compound came close to meeting the standard for CUTL of 125 [degrees] C. Oil resistance Oil resistance was tested by immersing all compounds in IRM (1) (Information Resource Management) See Information Systems and information management. (2) (Inherited Rights Mask) In NetWare 3.x and 4. 903 test oil for 70 hours at both 125 [degrees] C and 150 [degrees] C. Figures 6-9 show the effect of this exposure on physical properties and volume change. Because of their more polar nature, GECO and NBR/PVC exhibited smaller volume changes than CM and CSM. However, the CM and CSM maintained superior physical property retention after exposure to oil. As with the heat aging, the CM compound exhibited the smallest change in modulus and elongation at break, followed closely by the CSM and GECO, respectively. NBR/PVC was again subject to 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 , as shown by the significant increase in modulus and decrease in elongation. [FIGURES 6 & 8 OMITTED] Abrasion resistance A hose cover must have adequate abrasion resistance in order to effectively protect the inner tube and its contents. The results of DIN abrasion testing are shown in figure 10. CM and CSM are clearly the most abrasion resistant, followed by NBR/PVC and GECO, respectively. Fuel permeation resistance Fuel permeation resistance was tested with Fuel C at 23 [degrees] C for one week using the cup method. Peak and average permeation rates are shown in figure 11. GECO and NBR/PVC exhibited superior fuel permeation resistance, followed by CM and CSM. NBR/PVC is clearly advantaged in its fuel resistance but only in the unaged state. Upon heat aging, embrittlement and premature failure may result. [FIGURE 11 OMITTED] Note that typical fuel hose constructions include an inner barrier layer, often a fluoroelastomer veneer veneer (vənēr`), thin leaf of wood applied with glue to a panel or frame of solid wood. The art of veneer developed with early civilization. , for the explicit purpose of fuel containment. For this reason, fuel resistance is not a critical factor in the performance of a fuel hose cover. Ozone resistance Ozone resistance is another important property for fuel hose covers. Attack by ozone may result in surface cracking of the cover, subsequent damage to the inner tube, and finally increased fuel emissions or even leaks. All materials investigated in this study displayed superior resistance to surface cracking after exposure to 200 pphm ozone at 40 [degrees] C, 20% strain for 168 hours. Subambient properties A hose cover must retain its flexibility at sufficiently low temperatures in order to maintain good seals and minimize strain on the couplings. Subambient properties as measured by 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. are shown in figure 12. ECO E·co , Umberto Born 1932. Italian writer best known for his novels, including The Name of the Rose (1981). He has also written extensively on semiotics and British and American popular culture. was slightly advantaged with a lower glass transition temperature The glass transition temperature is the temperature below which the physical properties of amorphous materials vary in a manner similar to those of a solid phase (glassy state), and above which amorphous materials behave like liquids (rubbery state). than the other materials tested. Changes in formulation formulation /for·mu·la·tion/ (for?mu-la´shun) the act or product of formulating. American Law Institute Formulation will greatly influence these results. Sealing properties Sufficient sealing properties are essential in hose covers for coupling retention and prevention of leaks. Compression set resistance and sealing force retention as measured by Shawbury-Wallace compression stress relaxation Stress relaxation describes how polymers relieve stress under constant strain. Because they are viscoelastic, polymers behave in a nonlinear, non-Hookean fashion.[1] were the two methods employed to gauge the sealing properties of the various cover materials. Figure 13 shows a comparison of the compression set resistance at various conditions. CM and CSM exhibited superior set resistance over NBR/PVC and GECO for all conditions. Figure 14 shows the stress relaxation results for die-cut gaskets after three days exposure to hot air at 125 [degrees] C. Important attributes in this testing are high force retention coupled with the leveling out of retained force over time. As displayed in the graph, CM and CSM are the two cover materials that exhibited this balance of attributes. GECO had the highest percent retained force initially, but it rapidly declined. NBR/PVC exhibited lower levels of percent retained force that deteriorated quickly to values very close to zero at the end of the test time. A longer test time would be desirable for all materials to check the continuation of these trends. [FIGURES 13-14 OMITTED] Sulfur-based cure samples The results for the sulfur-based cure samples are discussed in detail in the ACS (Asynchronous Communications Server) See network access server. Rubber Division paper by C. Hooker and R. Vara, paper No. 128, Oct. 2000. The sulfur-based cure samples exhibited trends very similar to those discussed for the peroxide-cured samples. Conclusions CM exhibited superior heat resistance, compression set resistance and abrasion resistance versus all other materials tested. It also displayed the highest retention of physical properties upon oil aging. CM was inferior to NBR/PVC and GECO in the areas of oil swell and fuel permeation. CSM exhibited superior abrasion resistance, as well as good heat resistance, compression set resistance, and retention of physical properties upon oil aging. CSM was inferior to NBR/PVC and GECO in the areas of oil swell and fuel permeation. GECO exhibited superior resistance to oil swell and fuel permeation, good heat resistance, compression set resistance and retention of physical properties upon oil aging. However, heat resistance was inferior to that of CM. Also, resistance to abrasion and compression stress relaxation was inferior to those of CM and CSM. NBR/PVC exhibited superior resistance to oil swell and fuel permeation. However, resistance to heat aging, compression set, compression stress relaxation and abrasion was inferior to that of CM and CSM. In general, CM and CSM provide the best balance of performance attributes and cost for fuel hose cover materials. NBR/PVC exhibited good fuel and oil resistance and is generally offered at a lower cost than the other materials investigated. However, its poor heat resistance makes NBR/PVC an undesirable choice. GECO displayed the best combination of fuel, oil and heat resistance, but its higher cost may make the choice prohibitive pro·hib·i·tive also pro·hib·i·to·ry adj. 1. Prohibiting; forbidding: took prohibitive measures. 2. . CM and CSM exhibited the desirable combination of excellent heat and abrasion resistance, good sealing properties and good retention of oil-aged physical properties. And both CM and CSM are offered at reasonable cost making them the most logical choices for automotive fuel hose covers.
Figure 7 - volume change after fluid aging in
IRM 903 oil for 70 h. @ 125 [degrees] C peroxide cure
Percent
change (%)
CM 31
CSM 33
NBR/PVC1 -8
NBR/PVC2 -7
GECO 3
Note: Table made from bar graph.
Figure 9 - volume change after fluid aging in
IRM 903 oil for 70 h. @ 150 [degrees] C peroxide cure
Percent
change (%)
CM 34
CSM 40
NBR/PVC1 -9
NBR/PVC2 -8
GECO 4
Note: Table made from bar graph.
Figure 10 - DIN abrasion of peroxide cured
samples
Average volume
loss ([mm.sup.3])
CM 174
CSM 179
NBR/PVC1 244
NBR/PVC2 211
GECO 340
Note: Table made from bar graph.
Figure 12 - glass transition temperature (Tg) as
measured by differential scanning calorimetry
(DSC); peroxide cure
Tg([degrees] C)
CM -36.3
CSM -38.0
NBR/PVC1 -32.4
NBR/PVC2 -31.0
GECO -43.6
Note: Table made from bar graph.
Table 1 - peroxide cured formulations
Materials CM CSM NBR/ NBR/ GECO
PVC1 PVC2
CM 0136 100
CSM 4085 100
NBR/PVC P70 100
NBR/PVC 3470B 100
GECO T-85 100
N650 85 85 85 85 85
DOP 30 30 5
Epoxidized soybean oil 3
Polyester adipate 10 10 5
TOTM 40 40
1,2-dihydro-2,24- 0.2 0.5
trimethylquinoline
Diphenylamine-acetone 1 1 1
reaction product
ZMTI 1 1 1
Petroleum wax 3 3
Magnesium oxide 10 10 10 10 10
Zinc oxide 5 5
Zinc stearate 3
Stearic acid 1 1
TAIC 5 5 3
Di (2-tert-butylperoxyiso- 7 7.5 2.5 2.5 3.5
propyl) benzene
Total phr 250.2 248 248.5 248.5 216.5
Table 2 - sulfur-based cure formulations
Materials CM CSM NBR/ NBR/ GECO
PVC1 PVC2
CM 0136 100
CSM 4085 100
NBR/PVC P70 100
NBR/PVC 3470B 100
GECO T-85 100
N650 85 85 85 85 85
DOP 30 30 5
Epoxidized soybean oil 3
Polyester adipate 10 10 5
TOTM 40 40
Diphenylamine-acetone 1 1
reaction product
ZMTI 1 1
Mixed diaryl-p- 1.5 1.5
phenylendiamines
Styrenated diphenyl- 1
amine
1,2-bis(3,5-di-tert-butyl- 1
4-hydroxyhydrocin-
namoyl) hydrazine
Petroleum wax 3 3
2-imidiazolidinethione 1.33
MBTS 0.5 0.7 0.7
NBC 1 1
TBAB, 50% mb tetra- 0.6
ethyl thiuram disulfide
TETD 0.7 0.7
Dipentamethylene 2
thiuram tetrasulfide
TMTD 0.7 0.7
Magnesium oxide 10 10 10 10 10
Pentaerythritol 3 3
Zinc oxide 5 5
Zinc stearate 3
Stearic acid 1 1
Dimercaptothiadiazole 2.5
derivative
Spider sulfur 0.35 0.35
Total phr lab 246.1 241.5 249.95 249.95 210.33
Table 3 - test methods and aging conditions
Test Conditions ASTM number
Mooney viscosity 100 [degrees] C, large D1646-95A
rotor, 4 min.
Mooney scorch 125 [degrees] C, small D1646-95A
rotor, 30 min.
MDR 160 [degrees] C, 0.5
[degrees] arc, 30 min.
Tensile strength Originals D412-92
Tensile strength Hot air, 70 h. @ 100 D412-92
[degrees] C
Tensile strength Hot air, 70 h. @ 150 D412-92
[degrees] C
Tensile strength Hot air, 168 h. @ 125 D412-92
[degrees] C
Tensile strength Hot air, 1,008 h. @ 100 D412-92
[degrees] C
Tensile strength Hot air, 1,008 h. @ 125 D412-92
[degrees] C
Tensile strength IRM 903 oil 70 h. @ 125 D412-92
[degrees] C
Tensile strength IRM 903 oil 70 h. @ 150 D412-92
[degrees] C
Volume swell IRM 903 oil 70 h. @ 125 D471-96
[degrees] C
Volume swell IRM 903 oil 70 h. @ 150 D471-96
[degrees] C
Tensile strength Die C, 23 [degrees] C D624-91
Compression set 70 h. @ 100 [degrees] C,
pellet, 25%
Compression set 70 h. @ 125 [degrees] C,
pellet, 25%
Compression set 70 h. @ 150 [degrees] C,
pellet, 25%
DIN abrasion 23 [degrees] C, 200 ISO 4649-1985(E)
abrasion grade
DSC, glass transition Heat-cool-heat, 10
temperature (Tg) [degrees] C/min.,
nitrogen purge
Fuel permeation, cup Fuel C (isooctane/toluene E96
method 50/50) 168 h. @ 23
[degrees] C
Ozone surface cracking 200 pphm, 20% strain, D1149-91
168 h. @ 40 [degrees] C
Table 4 - original physical properties for
peroxide cured compounds
CM CSM NBR/ NBR/ GECO
PVC1 PVC2
Durom. A hardness (pts.) 78 72 76 78 73
Modulus at 100%
Elongation (MPa) 8.3 4.9 6.5 6.3 4.8
Tensile at break (MPa) 15.7 11.6 13.3 14.2 8.2
Elongation at break (%) 193 286 269 259 226
Tear strength (kN/m) 25 28 26 27 26
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