Use of coagents for adhesive and dynamic property improvements in peroxide-cured IR.The rubber industry has utilized sulfur and organic accelerators for over 70 years as the primary method of curing elastomers. Other methods of crosslinking, such as peroxides and amines amines (  mēnz´),n.pl organic compounds that contain nitrogen. , have filled various niches in specialty polymers and high performance applications. Until recently, peroxides and the commonly used coagents (acrylates, methacrylates, allyl allyl /al·lyl/ (al´il) a univalent radical, —CH2dbondCHCH2. al·lyl n. The univalent, unsaturated organic radical C3H5. cyanurates, low molecular weight polybutadienes and phenylene phen·yl·ene n. A bivalent organic radical, C6H4, derived from benzene by removal of two hydrogen atoms. phenylene The radical C6H4 dimaleimides), have generally produced fairly crystalline Like a crystal. It implies a uniform structure of molecules in all dimensions. For example, phase change technology, widely used for rewritable optical discs, uses crystalline spots (bits) to reflect the laser beam. Amorphous, non-crystalline bits do not reflect light. vulcanizates with application-limiting original physical properties such as high modulus See modulo. and hardness, combined with low 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 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. . Of course, their heat aging properties were superior to sulfur cure systems, making them very attractive in rigid specification compounds. This article introduces peroxide-initiated metallic coagents to cure synthetic polyisoprene elastomers. The resulting physical properties are similar to the classic sulfur-accelerator cure systems. In addition, the flex properties obtained by using this system greatly surpass those of the sulfur system, while still maintaining the superior aging characteristics of a 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. alone or peroxide-coagent system. Adhesion adhesion /ad·he·sion/ (ad-he´zhun) 1. the property of remaining in close proximity. 2. the stable joining of parts to one another, which may occur abnormally. 3. to various types of fiber and metal substrates can also be obtained by the use of this system. This unique combination of properties opens up a wide range of applications previously unavailable to peroxide-coagent curing of elastomers. The purpose of this article is to: * Highlight the optimization optimization Field of applied mathematics whose principles and methods are used to solve quantitative problems in disciplines including physics, biology, engineering, and economics. of a polyisoprene compound based on the use of a metallic methacrylate methacrylate /meth·ac·ry·late/ (meth-ak´ri-lat) an ester of methacrylic acid, or the resin derived from polymerization of the ester. See also acrylic resins, under resin. ; * provide performance property examples of both metallic acrylates and metallic methacrylates to educate the reader as to which coagent would be the best choice for use in a specific application: * highlight adhesion data for both metallic acryates and methacrylates; and * show how different peroxide types/cure temperatures can be used to overcome deficient de·fi·cient adj. 1. Lacking an essential quality or element. 2. Inadequate in amount or degree; insufficient. deficient a state of being in deficit. scorch/cure times versus sulfur. Peroxide-coagent cure mechanisms Crosslinking with peroxide alone results in the formation of a covalent bond covalent bond (kō'vā`lənt): see chemical bond. covalent bond Force holding atoms in a molecule together as a specific, separate entity (as opposed to, e.g., colloidal aggregates; see bonding). , as shown in figure 1. This carbon-carbon bond A carbon-carbon bond is a covalent bond between two carbon atoms. The most common form is the single bond – a bond composed of two electrons, one from each of the two atoms. is quite rigid and stable (343.2 kJ bond energy), compared to the carbon-sulfur and sulfur-sulfur bonds in sulfur cured systems (C S, 276.2 kJ bond energy: S-S S-S Surface-to-Surface S-S Space to Space , 205.1 kJ bond energy). The excellent heat stability of this carbon carbon covalent bond explains the superior heat aging characteristics of peroxide cured systems. [FIGURE 1 OMITTED] In contrast, although polysulfide pol·y·sul·fide n. A sulfide compound containing at least two sulfur atoms per molecule. crosslinks formed in sulfur cures are thermally weaker and can slip/break along the hydrocarbon hydrocarbon (hī'drōkär`bən), any organic compound composed solely of the elements hydrogen and carbon. The hydrocarbons differ both in the total number of carbon and hydrogen atoms in their molecules and in the proportion of hydrogen chain, they have the ability to reform. This mobility and breaking explains their superior tensile strength and tear properties. The metallic coagent-peroxide crosslink bond is ionic i·on·ic adj. Of, containing, or involving an ion or ions. ionic pertaining to an ion or ions. ionic medication iontophoresis. as shown in figure 2. The technology and characteristics of this ionic bond ionic bond: see chemical bond. ionic bond Electrostatic attraction between oppositely charged ions in a chemical compound. Such a bond forms when one or more electrons are transferred from one neutral atom (typically a metal, which becomes a cation) have been detailed in the literature on commercial ionomers. These ionic bonds exhibit both excellent heat-aged stability and the ability to slip, break, and reform along the hydrocarbon chain. Thus, this unique system embodies the best characteristics of both the peroxide and sulfur cure systems: high tensile strength, high tear strength, high modulus and outstanding flex and heat aged properties. [FIGURE 2 OMITTED] Experimental Materials A masterbatch containing 100 phr Natsyn 2200, 50 phr N660 carbon black, five phr zinc oxide zinc oxide, chemical compound, ZnO, that is nearly insoluble in water but soluble in acids or alkalies. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. , one phr stearic acid stearic acid /ste·a·ric ac·id/ (ste-ar´ik) a saturated 18-carbon fatty acid occurring in most fats and oils, particularly of tropical plants and land animals; used pharmaceutically as a tablet and capsule lubricant and as an emulsifying and one phr Agerite resin D was used in all experiments related to polyisoprene (synthetic natural rubber). Natsyn 2200 was obtained from Goodyear Chemical. Luperox F, Luperox DC and Luperox 231 peroxides were obtained from Atofina Chemical. Sartomer supplied the metallic coagents used in this experiment. Difficulties in mixing were initially encountered when the solid metallic coagent was used in its traditional powder form. The product is now being offered as a pelletized 75% active dispersion dispersion, in chemistry dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. in ethylene ethylene (ĕth`əlēn') or ethene (ĕth`ēn), H2C=CH2, a gaseous unsaturated hydrocarbon. It is the simplest alkene. propylene propylene /pro·pyl·ene/ (pro´pi-len) a gaseous hydrocarbon, CH3CHdbondCH2. propylene glycol a colorless viscous liquid used as a humectant and solvent in pharmaceutical preparations. copolymer copolymer: see polymer. (EPM EPM equine protozoal myeloencephalitis. ). These materials are marketed under the trade names Saret 75 EPM 2A (acrylate Noun 1. acrylate - a salt or ester of propenoic acid propenoate salt - a compound formed by replacing hydrogen in an acid by a metal (or a radical that acts like a metal) ) and Saret 75 EPM 2M (methacrylate). Alternate copolymer binders are in development. This form provides the improved mixing benefits of faster incorporation, more uniform dispersion and lower heat build up. This form is also dust-free, leading to a safer and healthier work place. Formulations Rubber compounds represented in table 1 were mixed in a prep 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. . Rubber compounds represented in tables 2-11 were mixed in a lab-scale mixer or two-roll mill. All samples (unless noted) 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. 21-23 minutes at 320[degrees]F, except for the sulfur samples, which were cured for 10 minutes. For DeMattia flex testing, cure times were 32 minutes for peroxide samples and 20 minutes for sulfur samples. Measurement Cure characteristics, which include scorch time, cure rate and torque values, were measured over a 30 minute period at 160[degrees]C and 3[degrees] arc using an oscillating-disk rheometer rhe·om·e·ter n. An instrument for measuring the flow of viscous liquids, such as blood. 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. ASTM ASTM abbr. American Society for Testing and Materials method D-2084-95. Mooney scorch data were obtained using a Mooney viscometer viscometer Instrument for measuring the viscosity (resistance to internal flow) of a fluid. In one type, the time taken for a given volume of fluid to flow through an opening is recorded. with a large rotor rotor: see generator; motor, electric. . All testing conformed to ASTM standard D-1646-94. Compression set was determined by compressing com·press tr.v. com·pressed, com·press·ing, com·press·es 1. To press together: compressed her lips. 2. To make more compact by or as if by pressing. 3. samples at 25% deflection deflection /de·flec·tion/ (de-flek´shun) deviation or movement from a straight line or given course, such as from the baseline in electrocardiography. de·flec·tion n. 1. for 70 hours at 100[degrees]C. Each sample was then removed and the permanent set measured as a percentage of original height according to ASTM standard D-395B. Durometer A hardness tests were determined for samples after molding using a hand-held durometer. Original physical properties were measured using die D dumbbells tested at 20 in./min. All samples were tested according to ASTM standard D-412-97, method A; 2240-97. Tear strength data were performed at 150[degrees]C. A die C specimen was used and testing conformed to ASTM standard D624-91. Heat age testing was performed after 70 hours at 100[degrees]C. All testing conformed to ASTM standard D-573-88 (94). Flexibility testing was measured according to DeMattia flexibility ASTM D-813-95. In this test, each specimen was pierced pierced adj. 1. Cut through with a sharp instrument; perforated. 2. Of or relating to a body part that has been perforated for the purpose of attaching a piece of jewelry. 3. 0.08 or 0.10 inches and tested at 300 cycles per minute. Unless otherwise noted, cycles to failure were reported when the piercing grew to 0.5 inches. Tan delta and complex modulus ratio (E* 120[degrees]C/E C/E Chief Engineer C/E Concurrent Engineering C/E Components/Equipment C/E Calculation Experiment C/E Calculated-to-Experimental (value or ratio) * 25[degrees]C) were measured through dynamic mechanical analysis (DMA (1) (Digital Media Adapter) See digital media hub. (2) (Document Management Alliance) A specification that provides a common interface for accessing and searching document databases. ). DMA testing followed ASTM standard D-2231-94. Two types of adhesion testing were performed. Lap shear shear: see strength of materials. Shear A straining action wherein applied forces produce a sliding or skewing type of deformation. adhesion was determined by testing a rubber specimen cured between two cold rolled steel coupons. This 0.030 inch specimen was cured at 160[degrees]C for 40 minutes (unless noted) between 1 x 3 x 0.030 inch coupons over-lapped one inch. A pressure of 30,000 psi PSI - Portable Scheme Interpreter was applied during curing. This test followed ASTM standard D-816. T-peel adhesion testing was performed by curing a 1 x 3 rubber specimen between the appropriate substrate The base layer of a structure such as a chip, multichip module (MCM), printed circuit board or disk platter. Silicon is the most widely used substrate for chips. Fiberglass (FR4) is mostly used for printed circuit boards, and ceramic is used for MCMs. and measuring the average peel strength over 2-3 inches of rubber tear. This test followed ASTM standard D-413 B, with a crosshead cross·head n. A beam that connects the piston rod to the connecting rod of a reciprocating engine. Noun 1. crosshead - a heading of a subsection printed within the body of the text crossheading speed of two inches/min. Results and discussion The initial study conducted in polyisoprene (IR) was a comparison of three cure systems: sulfur, peroxide and a peroxide-solid coagent (S-75 EPM 2M). Table 1 highlights the results. The high tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. data and the five-fold increase in flex life resulted in a much more extensive study of the new cure system in order to arrive at an optimum formulation. Polyisoprene was selected in this expanded study for two reasons: * It is more 'pure' than natural rubber, i.e., less likely to interfere with the free radical mechanism (more consistent cures); and * the large amount of historical flex data that is available for comparison with this polymer. Goals were set in this study to minimize the tan delta and to have the ratio of the complex modulus (E* 120[degrees]C/E*25[degrees]C) approach 1.0 as closely as possible. The following fine-tuned study shows the effect on the above, plus original physicals, aged physical properties and flex data versus a sulfur-organic accelerator cured compound. In table 2, the effects of varying peroxide levels while keeping coagent levels constant were studied. Once again, a conventional sulfur cure control was included. As shown in table 2, an increase in the level of peroxide has the expected effect of increasing hardness and modulus, while overall tensile strength remains relatively constant. In table 3, the coagent level was varied with constant peroxide levels. Once again, a sulfur system was included. Surprisingly, there is little or no effect on the physical properties by increasing the coagent levels. In the past, trends have shown that by increasing the levels of standard acrylic acrylic, artificial fiber made from a special group of vinyl compounds, primarily acrylonitrile. Acrylic fibers are thermoplastic (i.e., soften when heated, reharden upon cooling), have low moisture regain, are low in density, and can be made into bulky fabrics. coagents (TMPTMA, EGDMA EGDMA Ethylene Glycol Dimethacrylate , etc.), properties such as cured hardness and modulus increase dramatically. Table 4 summarizes the dynamic mechanical and flex data for the compounds in tables 2 and 3. The E* ratio and tan delta data for the peroxide-coagent systems are comparable to the data for a sulfur-accelerator system. The DeMattia flex results are outstanding for a peroxide-cured compound, with results 3-6 times greater than the sulfur cured compound. Another recent DeMattia flex study focused on the use of a more conventional sulfur-based cure system instead of the semi-efficient sulfur control (1.6 phr sulfur, 1.6 phr TBBS TBBS The Bread Board System TBBS The Big Blue Sky (website) ) evaluated previously. This conventional sulfur system used 2.25 phr sulfur and 0.70 phr TBBS. The DeMattia flex (under the same conditions as the samples in table 4) failed at 40,000 cycles. Optimization of peroxide/coagent levels Having studied a grid of peroxide levels from 2-4 phr and coagent levels from 5-9 phr, it seemed necessary to try to optimize the new coagent system (keeping in mind the relative cost of the cure system versus the sulfur cure system). Tables 2 and 3 suggested that lower peroxide and median coagent levels would be optimum. Table 5 is the result of that optimization. From that table, it is concluded that compounds 7 and 8 exhibit the optimum cure levels, although each application will require its own optimization. S-75 EPM 2A Although the S-75 EPM 2M was chosen for the above study, the S-75 EPM 2A also deserves special attention. Table 6 provides a general summary of the performance differences between the S-75 EPM 2A and 2M. Both the S-75 EPM 2A and 2M are evaluated in the remaining topics below. Low temperature DeMattia flex response In many critical applications, there is a need for a high flex response under low temperature conditions. Table 7 summarizes DeMattia test data taken at -40[degrees]C (after each sample was conditioned 10 minutes at -40[degrees]C). This portion of the study included the S-75 EPM 2A acrylate, as well as three examples of sulfur controls (conventional, semi-EV and EV). The peroxide-coagent systems still provide excellent flexibility even at low temperatures, whereas all three sulfur-accelerator combinations are 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. at the temperatures and ultimately cracked during testing. The use of metallic coagents also shows an improved low temperature flex response versus peroxide alone. Adhesion In recent years, a great deal of research has been put into evaluating metallic coagents in robber compounds for increased adhesion to steel, brass, zinc, aluminum, polyester polyester, synthetic fiber, produced by the polymerization of the product formed when an alcohol and organic acid react. The outstanding characteristic of polyesters is their ability to resist wrinkling and to spring back into shape when creased. , rayon and other substrates. A large percentage of previous adhesion work was performed using EPDM EPDM Ethylene-Propylene-Diene-Monomer EPDM Enterprise Product Data Management EPDM Ethylene Propylene Dimonomer (industrial/commercial piping/plumbing components) EPDM Engineering Product Data Management elastomers. This work was recently expanded to include the use of poly-isoprene for adhesion to both fabric and metallic substrates. Adhesion to cold rolled steel was performed with both S-75 EPM 2M and 2A. Figure 3 highlights these results. [FIGURE 3 OMITTED] As expected, using the metallic acrylate results in a higher bond to steel. The acrylate does become rather rigid at higher loadings, so one would expect the adhesion to level off as indicated in figure 3. Although the acrylate produces considerably higher adhesion levels to steel compared to the S-75 EPM 2M, the methacrylate is also a suitable choice for potential applications where bonding is desired, along with high flex demands. These coagents also can increase bonding to fabric substrates. Figure 4 shows t-peel adhesion data for bonding to nylon fabric. In this case, a common RFL RFL Relay For Life (American Cancer Society fundraiser) RFL Rugby Football League (UK) RFL Robot Fighting League RFL Refuel RFL Resorcinol-Formaldehyde-Latex (resorcinol resorcinol /re·sor·ci·nol/ (re-zor´si-nol) a bactericidal, fungicidal, keratolytic, exfoliative, and antipruritic agent, used especially as a topical keratolytic in the treatment of acne and other dermatoses. formaldehyde formaldehyde (fôrmăl`dəhīd'), HCHO, the simplest aldehyde. It melts at −92°C;, boils at −21°C;, and is soluble in water, alcohol, and ether; at STP, it is a flammable, poisonous, colorless gas with a suffocating latex latex, emulsion of a polymer (e.g., rubber) in water (see colloid). Natural latexes are produced by a number of plants, are usually white in color, and often contain, in addition to rubber, various gums, oils, and waxes. ) treatment was applied to the fabric prior to bonding to the elastomer elastomer (ĭlăs`təmər), substance having to some extent the elastic properties of natural rubber. The term is sometimes used technically to distinguish synthetic rubbers and rubberlike plastics from natural rubber. . It should be noted that these coagents typically offer greater adhesion to both treated and untreated fabrics. [FIGURE 4 OMITTED] Techniques for optimization of cure rate One of the downfalls of this peroxide-coagent system is deficient scorch and cute cute adj. cut·er, cut·est 1. Delightfully pretty or dainty. 2. Obviously contrived to charm; precious: "[He] times versus a sulfur-accelerator system. Tables 8 and 9 summarize sum·ma·rize intr. & tr.v. sum·ma·rized, sum·ma·riz·ing, sum·ma·riz·es To make a summary or make a summary of. sum rheology data from tables 2, 3 and 5. As seen in the tables, increasing the coagent level does little to help the cure time, and has only minimal effects on improving scorch times. Increasing the peroxide level results in both a scorchier cure and minimal change in overall cure time. Cure times can be improved by the manipulation of two variables, curing temperature and peroxide type. Up until this point of the study, dicumyl peroxide was the only peroxide evaluated, and 320[degrees]F was the standard curing temperature. Table 10 highlights cure and physical property data at 320[degrees]F, 338[degrees]F and 356[degrees]F cure temperatures. These data indicate that by curing at higher temperatures, physical properties are not severely affected, even though the scorch time (Ts2) does decrease (as expected). The acrylate (S-75 EPM 2A) appears to withstand the temperature changes better than the 2M, but both coagents maintain their cured elongation at all three curing temperatures. By using higher curing temperatures and shorter cycle times, this system can now be used to compete with a sulfur-accelerator based system. Table 11 shows an example of this scenario. Varying the peroxide type can also have a significant effect on cure rate and cured properties. Studies using bis Second version. It means twice in Old Latin, or encore in French. Ter means three. For example, V.27bis and V.27ter are the second and third versions of the V.27 standard. peroxides, dicumyl peroxides and peroxyketals reveal a wide variety of curing scenarios. Figure 5 gives cure times at various temperatures. 6.7 phr S-75 EPM 2M was included in these formulations. Peroxide levels were chosen to have equal active oxygen content. [FIGURE 5 OMITTED] Even though peroxides can be used in conjunction with a coagent to change cure times, their level of efficiency varies. In figure 6, the peroxyketal shows the lowest crosslinking response (as expected), but has a fairly stable cure profile from 275-330[degrees]F. The bis peroxide also shows a fairly stable cure profile from approximately 329[degrees]F to 383[degrees]E The dicumyl peroxide, although highly effective, is most dramatically affected by curing at high temperatures. But, looking again at figure 5 and tables 10 and 11, cure times and physical properties can be optimized at around 350[degrees]F using this cure system. [FIGURE 6 OMITTED] In using these techniques, care must be taken during the compounding phase. As expected, using different peroxides will result in different time and temperature limits before scorch will begin to occur. The same concept is true when a coagent is used in conjunction with peroxide. Figure 7 provides a "mixing guideline guideline Medtalk A series of recommendations by a body of experts in a particular discipline. See Cancer screening guidelines, Cardiac profile guidelines, Gatekeeper guidelines, Harvard guidelines, Transfusion guidelines. " when using different peroxides with S-75 EPM 2M. [FIGURE 7 OMITTED] Summary Previously, sulfur-accelerator and peroxide-coagent cure systems had their own domains of applications. By using a metallic coagent-peroxide system, the two can be used interchangeably INTERCHANGEABLY. Formerly when deeds of land were made, where there Were covenants to be performed on both sides, it was usual to make two deeds exactly similar to each other, and to exchange them; in the attesting clause, the words, In witness whereof the parties have hereunto with regard to original physical properties. Although this work was completed using synthetic natural rubber (polyisoprene), many of the concepts presented have been previously tested in EPDM elastomers. This indicates that these concepts could also apply to a variety of other elastomers. In addition to the synergy The enhanced result of two or more people, groups or organizations working together. In other words, one and one equals three! It comes from the Greek "synergia," which means joint work and cooperative action. between the two systems, the peroxide-coagent system offers much improved aging characteristics, greatly enhanced flex properties, excellent compression set, and much improved adhesion to various metals and fabrics when compared to conventional, semi-efficient, and efficient sulfur-cured systems.
Table 1 - historical comparison
Peroxide Sulfur Peroxide-S
Polyisoprene 100 100 100
Carbon black 50 50 50
Zinc oxide 5 5 5
Stearic acid 1 1 1
Agerite Resin D 1 1 1
Dicumyl peroxide 4 -- 2
(40% active)
S-75 EPM 2M -- -- 4
(active phr) -- 1.6 --
TBBS -- 1.6 --
Sulfur -- 1.6 --
Tensile strength (psi) 2,825 2,840 3,165
100% modulus (psi) 385 430 465
Elongation, % 375 355 380
Dynamic mechanical
analysis (DMA)
ASTM D-2231-94
E*120[degrees]C/E*25[degrees]C 1.017 1.112 0.899
Tan delta @ 25[degrees]C 0.22 0.18 0.19
DeMattia flexibility,
ASTM D-813-95
Cycles to failure 33,000 30,000 156,000
Compression set % 16 54 36
Table 2
1 2 3 Sulfur
control
Polyisoprene MB 157 157 157 157
Dicumyl peroxide 2 3 4 --
(40% active)
S-75 EPM 2M 5 5 5 --
(active phr)
TBBS -- -- -- 1.6
Sulfur -- -- -- 1.6
Rheometer data
Max torque (in.-lbs.) 56.7 69.4 76.5 71.8
Scorch time 1.8 1.6 1.4 3.3
(Ts2, min.)
Cure Time 17.0 17.5 17.1 6.1
(Tc90, min.)
Original physicals
ASTM D-412-97,
Method A; 2240-97
Tensile strength (psi) 3,380 3,450 3,340 2,840
300% modulus (psi) 1,810 2,260 2,450 1,720
Elongation, % 520 450 430 440
Hardness durometer A 58 60 61 63
Heat aged physicals
ASTM D-573-88(94)
Tensile strength; % chg. -8.3 -2.9 -3.9 -20.4
300% modulus; % chg. -5 -1.8 -2.9 16.3
Elongation, % chg. -3.8 -6.7 -4.7 -25.0
Hardness, chg. pts. +1 +2 +1 +3
Table 3
4 5 2 Sulfur
control
Polyisoprene MB 157 157 157 157
Dicumyl peroxide 3 3 4 --
(40% active)
S-75 EPM 2M 9 7 5 --
(active phr)
TBBS -- -- -- 1.6
Sulfur -- -- -- 1.6
Rheometer Data;
ASTM D-2084-95
Max torque (in.-lbs.) 64.2 71.8 69.4 71.8
Scorch time 2.0
(Ts2, min.) 1.6 1.6 3.3
Cure time 15.4 16.1 17.5 6.1
(Tc90, min.)
Original physicals
ASTM D-412-97,
Method A; 2240-97
Tensile strength (psi) 3,220 3,590 3,350 2,840
300% modulus (psi) 2,180 2,360 2,260 1,720
Elongation, % 440 460 450 440
Hardness, durometer A 61 62 60 63
Heat aged physicals
ASTM D-573-88(94)
Tensile strength -6.3 -8.6 -2.9 -20.4
% chg.
300% modulus -4.6 -6.4 -1.8 16.3
% chg.
Elongation, % chg. 0.0 -4.3 -6.7 -25.0
Hardness, chg. pts. +2 +1 +2 +3
Table 4
Peroxide 4 5
control
Polyisoprene MB 157 157 157
Dicumyl peroxide 2 3 3
(40% active)
S-75 EPM 2M -- 9 7
(active phr)
TBBS -- -- --
Sulfur -- -- --
Dynamic mechanical
analysis (DMA)
ASTM D-2231-94
E*120[degrees]C/E*25[degress]C 1.02 0.92 0.96
Tan delta @ 25[degrees]C 0.22 0.20 0.14
DeMattia flexibility,
ASTM D-813-95
Cycles to failure 33,000 140,000 110,000
1 2 3 Sulfur
control
Polyisoprene MB 157 157 157 157
Dicumyl peroxide 2 3 4 --
(40% active)
S-75 EPM 2M 5 5 5 --
(active phr)
TBBS -- -- -- 1.6
Sulfur -- -- -- 1.6
Dynamic mechanical
analysis (DMA)
ASTM D-2231-94
E*120[degrees]C/E*25[degress]C 0.93 0.96 0.97 1.04
Tan delta @ 25[degrees]C 0.17 0.16 0.15 0.15
DeMattia flexibility,
ASTM D-813-95
Cycles to failure 240,000 140,000 80,000 30,000
Table 5
6 7 8 Sulfur
control
Polyisoprene MB 157 157 157 157
Dicumyl peroxide 2 2 2 --
(40% active) --
S-75 EPM 2M -- 3 5
(active PHR)
TBBS -- -- -- 1.6
Sulfur -- -- -- 1.6
Rheometer data;
ASTM D-2084-95
Max torque (in.-lbs.) 39.4 47.8 51.7 75.1
Scorch time 1.8 1.8 2.0 2.8
(Ts2, min.)
Cure time 17.5 16.6 16.6 5.1
(Tc90, min.)
Original physicals
ASTM D 412-97,
Method A; 2240-97
Tensile strength (psi) 2,320 3,120 3,230 3,270
300% modulus (psi) 1,010 1,530 1,480 1,610
Elongation, % 550 530 540 530
Hardness, durometer A 49 56 57 64
Heat aged physicals
ASTM D 573-88(94)
Tensile strength (psi) 1,720 2,530 2,440 2,250
300% modulus (psi) 680 1,460 1,520 2,230
Elongation, % 540 470 440 300
Hardness, durometer A 45 54 56 66
Compression set, % 15 34 36 56
DeMattia flex 50,000 130,000 190,000 30,000
Table 6
S-75 EPM 2M S-75 EPM 2A
Slower cure Faster curing, higher initial
modulus
Greater flexibility Higher initial modulus
Less potential for scorch Higher potential for scorch
Moderate adhesion Significant adhesion
promoter promoter
Improved compression set Compression set slightly
versus sulfur improved over S-75 EPM 2M
Both coagents have excellent flex, tan delta, dynamic
modulus and heat stability
Table 7
1 2 3
System 2 phr 2 phr 2 phr
Crack growth dicumyl peroxide peroxide
(in.; avg. of 3) peroxide 5 phr 5 phr
S-75 S-75
EPM 2A EPM 2M
0 cycles 0.080 0.080 0.080
100 cycles 0.118 0.110 0.090
1,000 cycles 0.140 0.113 0.090
3,000 cycles 0.160 0.123 0.103
5,000 cycles 0.160 0.127 0.103
10,000 cycles 0.160 0.133 0.107
20,000 cycles 0.160 0.133 0.107
30,000 cycles 0.160 0.143 0.110
40,000 cycles 0.160 0.150 0.115
50,000 cycles 0.160 0.150 0.115
60,000 cycles 0.160 0.150 0.115
70,000 cycles 0.160 0.150 0.115
80,000 cycles 0.203 0.150 0.115
90,000 cycles 0.203 0.150 0.115
100,000 cycles 0.203 0.150 0.115
4 5 6
System 1.6 phr 0.5 phr 2.5 phr sulfur
Crack growth sulfur sulfur 0.8 phr TBBS
(in.; avg. of 3) 1.6 phr 2.4 phr (conventional)
TBBS TBBS(EV)
(semi-EV)
0 cycles 0.080 0.080 0.080
100 cycles 0.107 0.697 samples
1,000 cycles 0.107 (failure) broke
samples
3,000 cycles 0.120 broke --
5,000 cycles 0.127 -- --
10,000 cycles 0.137 -- --
20,000 cycles 0.147 -- --
30,000 cycles 0.170 -- --
40,000 cycles 0.180 -- --
50,000 cycles 0.190 -- --
60,000 cycles 0.217 -- --
70,000 cycles 0.233 -- --
80,000 cycles samples -- --
broke --
90,000 cycles -- --
100,000 cycles -- -- --
Table 8--effects of varying coagent levels on
cure rate
S-75 EPM 2M 40% dicumyl Scorch time Cure time
(active phr) peroxide (phr) (Ts2, min.) (TC90, min.)
0 2 1.8 17.5
3 2 1.8 16.6
5 2 2.0 16.6
7 2 2.0 17.1
9 2 2.3 16.7
Sulfur control -- 3.3 6.1
Table 9--effects of varying peroxide levels on cure rate
S-75 EPM 2M 40% dicumyl Scorch time Cure time
(active phr) peroxide (phr) (Ts2, min.) (TC90, min.)
5 2 2.0 16.6
5 3 1.6 17.5
5 4 1.4 17.1
Table 10
1 2 3 4 5
System 3.0 phr 40% DCP 3.0 phr 40%
6.7 phr S-EPM
Cure temp. ([degrees]F) 320 338 356 320 338
Tc 90 (min.) 32.2 14.8 6.83 28.0 12.0
Ts 2 (min.) 2.34 1.75 1.29 2.50 1.96
Mold cycle time (min.) 40 20 10 40 20
Tensile strength (psi) 3,050 3,100 2,830 3,150 3,100
Modulus 100 (psi) 180 190 175 380 350
Total % elongation 650 650 620 470 470
6 7 8 9
System DCP 3.0 phr 40% DCP
2A 6.7 phr S-EPM 2M
Cure temp. ([degrees]F) 356 320 338 356
Tc 90 (min.) 5.41 30.2 13.5 6.49
Ts 2 (min.) 1.41 2.49 1.84 1.34
Mold cycle time (min.) 10 40 20 10
Tensile strength (psi) 3,100 3,340 3,100 3,000
Modulus 100 (psi) 350 340 280 270
Total % elongation 480 530 530 520
Table 11--cured physical properties after ten minute cure cycle
Conventional SEV sulfur
sulfur (1.6 phr 3 phr 40% DCP
System (2.25 phr sulfur, 6.7 phr
sulfur, 0.7 1.6 phr S-EPM 2A
phr TBBS) TBBS)
Cure temp. ([degrees]F) 320 320 350
Tensile strength (psi) 3,620 3,760 3,400
Modulus 100 (psi) 315 333 315
Modulus 300 (psi) 1,120 1,215 1,480
Tear strength (pli) 325 335 310
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