Advances in CM technology for thermoset applications.

There are several elastomer choices for oil resistant applications. The most commonly used oil resistant elastomers are acrylonitrile butadiene rubber (NBR), polychloroprene rubber (CR) and acrylonitrile butadiene-polyvinylchloride blends (NBR/PVC). Other elastomers, such as hydrogenated acrylonitrile butadiene (HNBR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), various acrylic elastomers, silicones, fluorosilicones and fluorinated elastomers, are used where higher service temperature performance is required. The relative heat and oil resistance of various elastomers is graphically represented in the commonly used ASTM D2000/SAE J200 chart (figure 1).

Chlorinated polyethylene (CM) has been used in many heat and oil resistant hose, molded goods, and wire and cable applications. Its unique combination of heat and oil resistance makes it an ideal choice for many under the hood applications. It is also gaining increasing use in many industrial hoses, replacing some well-established materials such as CR due to concerns over high cost and availability. Since CM provides superior heat aging and excellent ozone resistance, it is increasingly used to replace some traditional materials to upgrade the end product performance. The utility of CM in hose applications was discussed in a paper presented by Guffey, et al (ref. 1) at the recent hose conference organized by the Rubber Manufacturers Association. Dow Chemical has developed new grades of Tyrin chlorinated polyethylene, and improved cure technology that makes them even more attractive versus conventional oil resistant elastomers. These advances in CM polymer and cure technology were presented by Laakso, et al (ref. 2) at the Fall 2006 ACS Rubber Division meeting.

[FIGURE 1 OMITTED]

At the Fall 2000 ACS Rubber Division Meeting, Hooker and Vara compared the performance of CM, CSM, NBR/ PVC and epichlorohydrin terpolymer (ECO) in typical fuel hose cover compounds (ref. 3). They concluded that, "CSM and CM provide the best balance of performance attributes and cost for fuel hose cover materials, exhibiting the desirable combination of excellent heat, ozone and abrasion resistance, good sealing performance and retention of oil-aged physical properties." Their studies were conducted with standard grades of CM using conventional thiadiazole (TD) and peroxide curing systems.

This study compares formulations using Tyrin CM (based on new cure and polymer technology) with CSM, CR, NBR and NBR/PVC.

Chlorinated polyethylene (CM)

Chlorinated polyethylene, ASTM designation CM or commonly referred to as CPE, has a saturated methylene backbone with chlorine atoms distributed along the polymer chain. The saturated methylene backbone provides the thermal oxidative stability and weather resistance, while the polar chlorine atoms provide the oil resistance. Although the chemical structure of CM is very straightforward, a range of products with varying properties can be produced by subtle changes in the way the building blocks are put together. The structure of the finished polymer is largely defined by the base high density polyethylene (HDPE) and the way in which the chlorine atoms are placed along the polymer chain. The key variables in a CM polymer are:

* Mooney viscosity, a measure of the molecular weight;

* chlorine content;

[FIGURE 2 OMITTED]

* residual crystallinity; and

* partitioning agent.

Effects of polymer variables

HDPE backbone

The fully saturated polymer backbone provides CM the outstanding thermal oxidative stability and resistance to ozone, UV and other weathering phenomena. With proper compounding, service temperatures of approximately 150[degrees]C can be easily achieved with CM formulations.

Molecular weight

As with all elastomers, high molecular weight yields high physical properties, high crosslinking efficiency, low compression set, ability to extend formulations with fillers and plasticizers, and the ability to maintain good green strength. There can be negative impact on processing, but these can be overcome with proper compounding and/or polymer design.

Chlorine content

The addition of chlorine to HDPE provides polarity to the polymer, resulting in resistance to a range of non-polar fluids, such as mineral oils and fuels. The resistance to these fluids increases with the chlorine content. The presence of chlorine also provides inherent flame retardant character to CM compounds. Increasing the chlorine content negatively impacts low temperature performance. It is therefore important to select the proper grade to balance the low temperature performance with the fluid resistance.

Crystallinity

Most grades of CM for elastomer use are essentially amorphous in nature, due to the destruction of crystallinity during the chlorination process.

Crosslinking of CM

CM can be crosslinked using conventional peroxide systems, thiadiazole (TD) or radiation. The most commonly used cure systems for CM are TD or peroxide. Both have advantages and limitations. The choice of the curative system is dependent on many considerations - economics, curing method and end use applications.

Peroxide curing

Peroxide curing of CM is similar to the crosslinking of many common elastomers with peroxide. Peroxide curing provides the best heat aging resistance with CM. The same principles of selection of peroxides, co-agents, stabilizers and compounding ingredients apply to CM, as with other elastomers. The primary limitations of peroxide curing are total cost of compounding due to limitations with choice of compounding ingredients and sensitivity in open air/steam curing.

Thiadiazole (TD) curing

Thiadiazole curing of halogenated elastomers has been used commercially since the early 1980s (ref. 4). The TD curing system consists of three components:

* A thiadiazole derivative as the cross linking agent;

* an organic amine or a quaternary ammonium salt; and

* magnesium oxide or magnesium hydroxide as a base.

The TD curing system offers greater flexibility in compounding and curing over peroxide curing systems. Lower cost mineral fillers and aromatic oils can be used with TD. It also offers the flexibility of curing over a range of temperatures and different curing methods and generates fewer volatile byproducts during curing.

Despite these advantages, the large-scale use and acceptance of TD curing for CM has been somewhat hampered by certain limitations. The primary limitation is the inconsistency of the rate and state of the vulcanization. This has been shown to be caused by zinc contamination and moisture, which is made worse under higher ambient storage temperatures of the finished compound. Special precautions are necessary during compounding and storage of mixed compounds. Even with special precautions, some end users have not been able to overcome the problems of inconsistency and have abandoned this curing option.

Dow Chemical has introduced two new curing additives to improve the curing inconsistency experienced by many end users. The details of these additives and their effectiveness in curing CM were presented by Laakso, et al (ref. 2). These additives vastly reduce the curing inconsistency experienced with conventional TD cure.

Zinc is a very common material that is present in most rubber compounding facilities. Even with exceptional housekeeping and extraordinary precautions, the presence of trace amounts of zinc can pose a potential problem for curing CM with TD. The cure consistency agent (CCA) is a chelating agent that can intercept contaminants, such as zinc, that interfere with the thiadiazole curing mechanism (ref. 5). The effectiveness of the chelating agent was discussed in detail by Laakso, et al (ref. 2). The impact of zinc contamination on the cure characteristics of a CM compound is illustrated with curemeter results (figure 2). The use of a chelating agent significantly reduces or eliminates the detrimental effects of zinc contamination on cure response.

[FIGURE 4 OMITTED]

Another area for potential issues with TD cure is the sensitivity of compounds to moisture and heat. In the presence of moisture and above ambient temperatures, TD based compounds can start to prematurely crosslink. This premature crosslinking leads to poor bin stability. The tendency to prematurely crosslink is dependent on the amount of accelerator. The amount of traditional accelerator used in CM compounds can be considerably reduced by the use of a novel hydrated salt referred to as the cure rate accelerator (CRA) (ref. 2). The use of lower levels of accelerator in turn reduces the tendency of the compound to prematurely crosslink or scorch, thereby increasing the scorch time and bin stability. This is achieved without sacrificing the rate or state of the cure or the physical properties of the final vulcanizates.

Innovative polymer design

Several grades of chlorinated polyethylene elastomer have been available from Dow Chemical for many years. Along with the introduction of the improved thiadiazole cure technology, Dow has also started to introduce a unique family of innovative new polymers to meet some demanding needs of end users. Tyrin EXT 1000 was introduced recently as the first of this family of new CM polymers (ref. 6). EXT 1000 is designed to accept very high loadings of fillers and plasticizers, and yet maintain the desirable high strength properties and low compression set. High extension of CM formulations provides a means of lowering compound cost and makes the compounds cost competitive versus many traditional oil resistant elastomers.

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

CM versus other oil resistant elastomers

The relative position of the heat and oil resistance of CM versus many of the commonly used elastomers is well represented graphically in the ASTM D2000 or the SAE J200 chart (figure 1). Hooker and Vara compared CM with CSM, NBR/PVC and ECO as cover materials for oil resistant hoses in their paper.

In this study, two grades of CM were compared with CSM, CR and NBR/PVC compounds using both peroxide and non-peroxide cure systems. One of the CM grades is a newly developed, highly extendable product designed to accept higher loadings of filler and oil. This investigation compares the various polymers in non-optimized compounds using common ingredients to the extent possible. Cure components were varied depending upon the polymer type.

[FIGURE 7 OMITTED]

Experimental

Ingredients

The ingredients were used as received from the suppliers, as listed in table 1.

Mixing of the compounds

Chlorinated polyethylene and chlorosulfonated polyethylene Compounds were mixed in a BR style internal mixer using an upside-down mixing procedure and 0.75 load factor. In the upside-down procedure, the dry ingredients were charged to the mixer first, followed by the liquid ingredients, and finally the polymer. A slow mixing speed was used. The chute was "swept down" after fluxing and the mixture was dumped from the mixer at approximately 105[degrees]C.

Polychloroprene

Compounds were mixed in a BR style internal mixer using a right-side up mix procedure (add polymer first) and a single stage mix. The compound was dumped from the mixer at 110[degrees]C.

NBR/PVC (sulfur cure)

Compounds were mixed in a BR style internal mixer using the following two-pass mix procedure:

[FIGURE 9 OMITTED]

[FIGURE 10 OMITTED]

* First pass (no TBBS and no TMTM)--A right-side up mix procedure was used. Time did not exceed 2.5-3 minutes, and the temperature of the stock did not exceed 140[degrees]C.

* Second pass--Strips from the first pass were fed to the mixer at slow mixer speed. About half of the strips were added, then the TBBS and TMTM were added, followed by the remaining strips. The mixing temperature was kept below 105[degrees]C.

NBR/PVC (peroxide cure)

The mixing procedure for the peroxide cured NBR/PVC compound was essentially the same as that shown for the sulfur cured procedure. The peroxide and coagent were withheld from the first pass and added during the second pass.

Milling

All of the discharged compounds were cooled via working on a two-roll mill. Dispersion was ensured via mixing with a "cigar-rolling" technique in which the blanket was rolled into a cigar shape as it came off the mill and then reinserted through the rolls in a lengthwise direction (repeated 5-6 times).

Sample preparation and testing

Compression molded plaques approximately 2 mm thick were cured using rheometer t90+20% cure times at the specified test temperature. Compression set buttons were cured for 1.5 times the plaque cure time.

Recipes and testing The recipes used for compound preparation are included (tables 2 and 3). Testing was conducted as per the procedures listed in table 4.

Results and discussion

Refer to tables 5 and 6 for test results. Note that a peroxide cured CR compound was not included in these studies.

Peroxide cured compounds

Processing

The recipes used for this study were not optimized for each polymer. A low viscosity NBR/PVC base polymer translated to a much lower compound viscosity relative to any of the CM or CSM compounds (figure 3). The compounds based on Tyrin EXT were more comparable to the CSM compound.

A range of compound viscosities is possible with any polymer. For example, designed experimental studies with Tyrin EXT 1000 have been conducted, which show that the polymer can be compounded to yield ML(1+4)@100[degrees]C viscosity values over a wide range (R2 = 0.99, RMSE = 3.602, P<0.0001).

The Mooney Scorch times at 125[degrees]C indicate that the CSM compound was the fastest to scorch (4.4 minutes vs. scorch times of greater than 25 minutes for the NBR/PVC compound). The CM compounds had [t.sub.3] scorch values between 16 and 22 minutes (table 5).

Cure characteristics

The cure times of all the peroxide-cured compounds were similar at 180[degrees]C. The times ranged from 4.5-7 minutes. The CSM compound was the fastest cure at 4.5 minutes and the NBR/PVC was the slowest cure at 6.7 minutes. The [t.sub.90] cure times for the CM compounds were between the CSM and the NBR/PVC compounds.

Original physical properties

The physical properties of these peroxide cured compounds illustrate the excellent performance of the CM compounds (table 5). At approximately equal hardness, the compounds based on Tyrin EXT provided similar or greater moduli, tensile and elongation values compared to CR and CSM.

Heat aging resistance

Combinations of heat aging conditions were measured in this study (table 5). At less severe conditions, such as 70 hours at 100[degrees]C, all of the compounds displayed similar performance of tensile and elongation after aging. However, when the temperature was increased to 150[degrees]C for 70 hours, the NBR/ PVC compound became embrittled (-100% change in elongation). Even at 125[degrees]C for 168 hours, the NBR/PVC compound exhibited an undesirable 75% loss in elongation. The unsaturated nature of the NBR backbone contributes to this performance. Conversely, the saturated backbone of CM and CSM contributes to their superior performance in these aging tests.

To test the long-term aging performance of these compounds, specimens were subjected to conditions defined in SAE J2236 to determine the continuous upper temperature limit (CUTL). The CUTL is defined as the temperature at which the material retains 50% minimum of both the original elongation and the tensile at break after 1,008 hours in an air-circulating oven. In both the 100[degrees]C and 125[degrees]C test conditions for 1,008 hours, both the CSM and CM compounds passed, and the NBR/PVC compound did not (figures 4 and 5).

IRM 903 immersion 

Oil immersion resistance was tested at 100[degrees]C and 125[degrees]C for these compounds. To illustrate the general performance of the compounds, the 125[degrees]C data for elongation change and volume swell are plotted (figure 6).

The NBR/PVC compound exhibited the lowest volume swell for this type compound under the given test conditions. The NBR/PVC also exhibited the largest change in elongation. This change is most likely due again to the unsaturated nature of the NBR/PVC and the effects of heat aging at 125[degrees]C.

Compression set

The compression set values were measured after 70 hours at 100[degrees]C, 125[degrees]C and 150[degrees]C (figure 7). The compounds based on Tyrin EXT had the lowest compression set values overall. For example, at 150[degrees]C, these compounds had values of 40-47% versus 100% for NBR/PVC and 75% for CSM.

Abrasion

Many elastomeric parts require good abrasion resistance in their end-use application. The abrasion test results of these compounds indicated similar performance for all (table 5). More abrasion resistant compounds are possible with the less highly filled Tyrin EXT. For example, compounds of Tyrin EXT with the same loading as the NBR/PVC or the CSM compound yielded less volume loss.

Low-temperature performance

A Rheometrics Dynamic Spectroscopy (RDS-II) unit was used to test the low temperature performance of the cured plaques (figure 8). The glass transition temperature ([T.sub.g]) of the compound was measured at the maximum height of the tan delta peak. At the same filler loading, the CM and CSM grades had the same, [T.sub.g] of-28[degrees]C. The NBR/PVC compound suffered in its low temperature performance with a [T.sub.g] of-16[degrees]C. The more highly filled compound based on Tyrin EXT exhibited the best [T.sub.g] of -36[degrees]C.

Tear strength

The tear strength of cured plaques was measured using the Type C die. The compounds based on CM produced the highest tear strengths (39-82 N/mm) compared to 32 N/mm for CSM and 29 N/mm for the NBR/PVC compound (table 5).

Sulfur-type cured compounds

Table 6 contains the tabulated data for the sulfur type compounds. A discussion about some of the key properties is included in this section.

Heat aging resistance

Sulfur cured compounds typically do not possess the same degree of heat resistance as peroxide cured compounds. This trend was found to be true in this study. For example, none of the compounds passed the CUTL of 1,008 hours at 125[degrees]C for the sulfur based cures. The CR and NBR/PVC compounds experienced a -100% change in elongation during this test. However, reformulation of some of the compounds could result in improved heat aging performance. For example, the compound of Tyrin EXT with 35% increased filler loading nearly passed the test with a -51.8% change in elongation (specification is -50%).

Even at 100[degrees]C for 1,008 hours, the CR and NBR/PVC compounds did not pass the CUTL requirements. The polymers with saturated backbones, CM and CSM, easily met the specification (figure 9). Test results for 70 hours at 150[degrees]C indicate the same trend: The polymers with saturated backbones performed better in these tests (table 6).

IRM 903 immersion

For the compounds with sulfur containing cure systems, the oil resistance of the CM compounds, as measured by volume swell, was in the range of performance of the CR and NBR/PVC compounds (figure 10).

Compression set

At the same filler loading, the compound with Tyrin EXT had the lowest compression set values for the three conditions. At 100[degrees]C, its compression set was 19% versus 74%, 51% and 29% for NBR/PVC, CSM and CR, respectively. A similar trend was observed for the 150[degrees]C test results.

Tear strength

At similar filler loadings, the compound based on Tyrin EXT had the highest tear strength (table 6). With an increased filler loading, the tear strength was comparable to CSM and CR.

Abrasion resistance

The compounds based on Tyrin EXT were similar (150-162 [mm.sup.3] loss) to CR (152 [mm.sup.3] loss) in their abrasion resistance (table 6). NBR/PVC and CM 0136 had the highest loss (202 [mm.sup.3] and 209 [mm.sup.3], respectively). The CSM compound had the best abrasion resistance with 140 [mm.sup.3] volume loss.

Low-temperature performance

The more highly filled compound with Tyrin EXT 1000 had the best low-temperature performance with a [T.sub.g] of -42[degrees]C. The [T.sub.g] of the CR compound was -34[degrees]C, and the CSM compound was -25[degrees]C. Similar to the peroxide cured NBR/PVC compounds, the sulfur cured NBR/PVC had the worst lowtemperature performance (-16[degrees]C).

Summary and conclusions

Chlorinated polyethylene is a heat, weathering and oil resistant elastomer that has been used in many automotive and industrial rubber parts for many years. CM can be crosslinked using thiol-based curatives or using conventional peroxide systems. The thiol-based systems provide greater flexibility in compounding and processing to provide low cost compounds. The peroxide crosslinked systems yield exceptionally good thermal oxidative stability at elevated temperature. This makes CM an ideal elastomeric material in many automotive under-the-hood applications and many industrial rubber parts.

Recent advances in unique polymer design and alternative cure technology by Dow Chemical make it even more attractive to design lower cost CM formulations. The potential to design low cost, high temperature and oil resistant formulations using Tyrin EXT 1000 makes it possible to compete with some of the traditional oil resistant elastomers, such as CR, NBR/PVC and CSM. In addition, this new grade of Tyrin CM is a robust base polymer, allowing the development of highly extended or high strength formulations over a wide range of compound viscosities.

As demonstrated in this article, more highly filled compounds based on Tyrin EXT 1000 offer an opportunity to generate similar or better performance with potential improved compound economics due to higher filler loading capabilities. Compound optimization is required to balance processability / performance criteria. In this current study, Tyrin EXT 1000 with higher filler loadings demonstrated outstanding performance in the following areas:

Peroxide-cured compounds

* Heat aging resistance 1,008 hours at 100[degrees]C and 125[degrees]C--Tyrin EXT 1000 ~ CSM >> NBR/PVC.

* IRM 903 (70 h./125[degrees]C) change in elongation--Tyrin EXT 1000 ~ CSM < NBR/PVC.

* IRM 903 (70 h./125[degrees]C) volume swell--NBR/PVC < Tyrin EXT 1000 ~ CSM.

* Compression set--Tyrin EXT 1000 << CSM < NBR/ PVC.

* Low-temperature ([T.sub.g])--Tyrin EXT 1000 < CSM << NBR/PVC.

* Tear strength (Type C)--Tyrin EXT 1000 > NBR/PVC CSM.

Sulfur type cured compounds

* Heat aging resistance 1,008 hours at 100[degrees]C and 70 hours at 150[degrees]C--Tyrin EXT 1000 ~ CSM >> NBR/PVC ~ CR.

* IRM 903 (70 h./125 [degrees]C) volume swell--Tyrin EXT 1000 ~ CSM ~ NBR/PVC < CR.

* Compression set--CR < Tyrin EXT 1000 < NBR/PVC CSM.

* Low-temperature ([T.sub.g])--Tyrin EXT 1000 < CR < CSM << NBR/PVC.

* Tear strength (Type C)--Tyrin EXT 1000 > NBR/PVC CSM.

This article is based on a paper presented at a meeting of the Rubber Division, ACS (www.rubber.org).

References

(1.) V. Guffey, R. Laakso and R. Vara, "Chlorinated polyethylene elastomers for heat and oil resistant applications," Hose Manufacturers' Conference, June 2007, Cleveland, OH.

(2.) R.L. Laakso, G.R. Marchand, V. Guffey and R. Vara, "Recent advances in chlorinated polyethylene technology for thermoset elastomer applications," ACS Rubber Division, October 10-12, 2006, Cincinnati, OH.

(3.) C. Hooker and R. Vara, "A comparison of chlorinated and chlorosulfonated polyethylene elastomers with other materials for automotive fuel hose covers," ACS Rubber Division, October 17-20, 2000, Cincinnati, OH.

(4.) J.H. Flynn and W.H. Davis, Jr., "Tyrin brand CPE thiadiazole cure system studies--chemistry and dispersion, "ACS Rubber Division, April 23-26, 1985

(5.) PCT International Application, WO 2006069191, R.L. Laakso, G.R. Marchand and B.L. Watson.

(6.) U.S. Patent 6, 720,383, Curable composition of chlorinated polyolefin elastomers, J.R. Barclay, et al, issued April 13, 2004 to DuPont Dow Elastomers, LLC 

by Ray Laakso, Virginia Guffey and Rajan Vara, Dow Chemical (www.plastics.dow.com/plastics/na/prod/specialty/tyrin.htm)

Table 1--ingredients

Ingredient                              Supplier

Tyrin EXT 1000 chlorinated              Dow Chemical
  polyethylene
Tyrin CM 0136 chlorinated               Dow Chemical
  polyethylene (CM 0136)
Neoprene W (CR)                         DuPont Performance Elastomers
Hypalon 4085 (CSM)                      DuPont Performance Elastomers
Sivic Z730M60 (NBK/PVC)                 Zeon Chemicals
Synthetic rubber (SBR)                  Dow Chemical
  Buna SB 1500--Schkopau
N-550 Carbon black                      Sid Richardson Carbon
N-762 carbon black                      Sid Richardson Carbon
Magnesium oxide                         HallStar
Mastermix Echo A MB 4842-               Excel Polymers
  75% (2-mercapto-1,3,4-thiadiazole-
  5-thiobenzoate 75% active)
3,5-diethyl-1,2-dihydro-1-phenyl-2-     R.T. Vanderbilt
  propylpyridine (DDPP) (Vanax 808HP)
Mastermix MB-4988-50%                   Excel Polymers
  active (TBAB MB50)
TOTM                                    HallStar
AgeRite Resin D                         R.T. Vanderbilt
Carbowax 3350                           Dow Chemical
MBTS                                    Akrochem
Vanox NBC                               R.T. Vanderbilt
Tetrone A                               DuPont Performance Elastomers
Stearic acid                            HallStar
Polyethylene wax                        Honeywell Specialty Chemicals
Octamine                                Chemtura
Sundex 790TN                            Sunoco
Sulfur                                  Rhein Chemie
Vanax DOTG                              R.T Vanderbilt
Zinc oxide                              Horsehead Corp.
TMTM                                    Akrochem
Paraffin wax                            The International Group, Inc.
Microcrystalline wax                    Strahl & Pitsch, Inc.
DOP                                     HallStar
Hyprene L2000                           Ergon
TBBS-75                                 Polymerics
Redimix 9924                            Excel Polymers
Mastermix curative 5910                 Excel Polymers
VulCup 40KE                             GEO Specially Chemicals
Saret SR 517                            Sartomer

Tyrin and Cardowax are registered trademarks of Dow Chemical.

Hypalon and Tetrone A are registered trademarks of DuPont
Performance Elastomers.

Mastermix and Redmix are registered trademarks of Excel Polymers,
Vanox, Vanax, Agerite are registered trademarks of R.T. Vanderbilt.

Octamine is a registered trademark of Chemtura.

Sundex is a registered trademark of Sunoco.

Hyprene is a registered trademark of Ergon.

VulCup is a registered trademark of GEO Specialty Chemicals.

Saret is a registered trademark of Sartomer, Inc.

Table 2--recipes used for peroxide cured compounds

                      0436P59-01
                           Tyrin    0436P59-02    0436P59-03
                         CM 0136           CSM       NBR/PVC

Tyrin EXT 1000
Tyrin CM 0136                100
VulCup 40KE                    6             6             3
Saret SR 517                   5             5             5
Magnesium oxide                5             5
N-550 carbon black            30            30            30
N-762 carbon black            50            50            50
TOTM                          30            30
AgeRite Resin D             0.25          0.25           0.5
Hypalon 4085                               100
Carbowax 3350                                3
Sivic Z730M60                                            100
SBR rubber                                                30
Zinc oxide                                                 5
Stearic acid                                               1
DOP                                                       25
Hyprene L2000                                              5
Total phr:                226.25        229.25         254.5
Density (g/cc)              1.32         1.339         1.207

                      0436P59-04       0436P89-07
                           Tyrin       Tyrin EXT+
                        EXT 1000     35% increase

Tyrin EXT 1000               100              100
Tyrin CM 0136
VulCup 40KE                    6                6
Saret SR 517                   5                5
Magnesium oxide                5                5
N-550 carbon black            30               55
N-762 carbon black            50               75
TOTM                          30               65
AgeRite Resin D             0.25             0.25
Hypalon 4085
Carbowax 3350
Sivic Z730M60
SBR rubber
Zinc oxide
Stearic acid
DOP
Hyprene L2000
Total phr:                226.25           311.25
Density (g/cc)             1.320            1.327

Table 3--recipes used for sulfur-based compounds

                            0436P49-01
                                 Tyrin    0436P49-02     0436P49-03
                               CM 0136           CSM             CR

Tyrin EXT 1000
Tyrin CM 0136                      100
Mastermix 4842-75%                   3
Vanax 808 HP                      0.25
Magnesium oxide                      5             5              5
N-550 carbon black                  30            30             30
N-762 carbon black                  50            50             50
TOTM                                30            30
AgeRite Resin D                   0.25
Hypalon 4085                                     100
Carbowax 3350                                      3
MBTS                                             0.5
Vanox NBC                                          1
Tetrone A                                          2
Neoprene W                                                      100
Stearic acid                                                      1
Polyethylene wax                                                  3
Octamine                                                          2
Sundex 790TN                                                     30
Sulfur                                                         0.75
Vanax DOTG                                                      0.3
Zinc oxide                                                        4
TMTM                                                            0.5
Paraffin wax                                                      2
Micro Wax SP 60                                                   2
Sivic Z730M60
SBR Rubber
DOP
Hyprene L2000
TBBS-75
Redimix 9924
Master mix curative 5910
Total phr:                       218.5         221.5         230.55
Density [g/cc]                   1.323         1.344          1.353

                                          0436P49-05      0436P49-08
                            0436P49-04         Tyrin      Tyrin EXT+
                                NBWPVC           EXT    35% increase

Tyrin EXT 1000                                   100             100
Tyrin CM 0136
Mastermix 4842-75%                                 3               3
Vanax 808 HP                                    0.12            0.12
Magnesium oxide                                    5               5
N-550 carbon black                  30            30              55
N-762 carbon black                  50            50              75
TOTM                                              30              65
AgeRite Resin D                      1          0.25            0.25
Hypalon 4085
Carbowax 3350
MBTS
Vanox NBC
Tetrone A
Neoprene W
Stearic acid                         1
Polyethylene wax
Octamine
Sundex 790TN
Sulfur                               2
Vanax DOTG
Zinc oxide                           5
TMTM                               0.2
Paraffin wax
Micro Wax SP 60
Sivic Z730M60                      100
SBR Rubber                          30
DOP                                 25
Hyprene L2000                        5
TBBS-75                           2.13
Redimix 9924                                       1               1
Master mix curative 5910                           2               2
Total phr:                      251.33        221.37          306.37
Density [g/cc]                    1.21          1.32           1.328

Table 4--test procedures

Test                                     Method

Physical properties (stress/strain)     ASTM D412
Hardness                                ASTM D2240
Heat aging                              ASTM D573
Immersion testing                       ASTM D471
Mooney scorch and Mooney viscosity      ASTM D1646
Moving die rheometer (MDR)              ASTM D5289
Oscillating disc rheometer (ODR)        ASTM D2084
Tear test (type C)                      ASTM D624
Compression set                         ASTM D395
Abrasion resistance                      ISO 4649

Table 5--peroxide cured data

                                          Tyrin
                                        CM 0136        CSM    NBR/PVC

Mooney scorch (MS+1 @ 125[degrees]C)
Init. viscosity (MU)                       48.0       64.6       25.0
Min. viscosity (MU)                        32.8       48.4       13.3
t3 (min.)                                 22.23        4.4        >25
t5 (min.)                                 24.01       4.69         --
Mooney viscosity
ML(144)@100[degrees]C (MU)                 86.9      111.0       39.8
Moving die rheometer (MDR)
Test temp. (C)                              180        180        180
ML (dNm)                                   2.04       3.08        0.7
MH (dNm)                                  20.01      18.85      14.25
ts2 (min.)                                 0.57       0.46       0.93
t50 (min.)                                 1.94       1.44       2.14
t90 (min.)                                 5.86       4.54       6.74
Original physical properties
25% modulus (MPa)                          1.88       2.26       1.88
1001/6 modulus (MPa)                       6.07       7.29       7.76
2001% modulus (MPa)                       13.76         --       15.9
Tensile strength (MPa)                     16.4       14.0       16.4
Elongation (%)                              290        194        205
Hardness (duro. A)                           78         77         77
Tear strength
Die C tear (N/mm)                          42.5       32.3       28.8
Compression set
70 h./100[degrees]C (%)                      25         42         28
70 h./1 25[degrees]C (%)                     41         56         39
70 h./1 50[degrees]C (%)                     47         75        104
Abrasion (ISO 4649)
Volume loss (m[m.sup.3])                  173.1      189.3      187.4
Low temperature properties
Dynamic mechanical spectroscopy
[T.sub.g] (deg. C)                          -28        -28        -16
tan [delta] @ [T.sub.g]                   0.554      0.886      0.638

ASTM D573 Heat aging
Heat aging 1,008 hours/100[degrees]C
Tensile (% change)                        -1.0%      18.7%      14.9%
Elongation (% change)                    -21.4%      -0.5%     -62.4%
Hardness change (points)                      4          3         15
Heat aging 1,008 hours/125[degrees]C
Tensile (% change)                        -7.2%      12.0%     -34.5%
Elongation (% change)                    -45.9%     -26.3%    -100.0%
Hardness change (points)                     10          9         22
Heat aging 70 hours/100[degrees]C
Tensile (% change)                         0.1%       7.2%       4.1%
Elongation (% change)                     -3.1%       1.6%      -9.3%
Hardness change (points)                      2          2          3
Heat aging 70 hours/150[degrees]C
Tensile (% change)                        -2.4%       7.6%       4.9%
Elongation (% change)                    -11.7%      -4.6%    -100.0%
Hardness change (points)                      5          6         22
Heat aging 168 hours/125[degrees]C
Tensile (% change)                         2.1%      12.6%      11.5%
Elongation (% change)                     -4.5%       1.0%     -75.1%
Hardness change (points)                      4          4         17
Oil immersion data
IRM 903/70 hours/100[degrees]C
Tensile (% change)                       -14.3%     -21.6%     -31.9%
Elongation (% change)                    -16.2%     -22.4%     -37.6%
Hardness change (points)                    -20        -13         -6
Volume swell (%)                           41.8       28.0       17.0
IRM 903!70 hours/125[degrees]C
Tensile (% change)                       -12.1%      -7.9%     -43.4%
Elongation (% change)                    -19.0%     -16.1%     -48.8%
Hardness change (points)                    -20        -15         -3
Volume swell (%)                           46.3       33.4       16.4

                                           Tyrin      Tyrin EXT+
                                        EXT 1000    35% increase

Mooney scorch (MS+1 @ 125[degrees]C)
Init. viscosity (MU)                        77.0            57.2
Min. viscosity (MU)                         58.6            42.6
t3 (min.)                                  16.84           18.66
t5 (min.)                                  18.32           19.67
Mooney viscosity
ML(144)@100[degrees]C (MU)                 123.1            99.4
Moving die rheometer (MDR)
Test temp. (C)                               180             180
ML (dNm)                                    4.18            2.71
MH (dNm)                                    25.2           16.09
ts2 (min.)                                  0.44            0.67
t50 (min.)                                  1.60            2.12
t90 (min.)                                  4.97            5.36
Original physical properties
25% modulus (MPa)                           2.16            1.86
1001/6 modulus (MPa)                        7.99            6.52
2001% modulus (MPa)                        16.79           12.40
Tensile strength (MPa)                      19.9            14.8
Elongation (%)                               255             267
Hardness (duro. A)                            81              79
Tear strength
Die C tear (N/mm)                           81.7            38.8
Compression set
70 h./100[degrees]C (%)                       18              22
70 h./1 25[degrees]C (%)                      30              38
70 h./1 50[degrees]C (%)                      37              47
Abrasion (ISO 4649)
Volume loss (m[m.sup.3])                   140.9           195.0
Low temperature properties
Dynamic mechanical spectroscopy
[T.sub.g] (deg. C)                           -28             -36
tan [delta] @ [T.sub.g]                    0.575           0.543

ASTM D573 Heat aging
Heat aging 1,008 hours/100[degrees]C
Tensile (% change)                         -6.4%           -4.6%
Elongation (% change)                     -19.6%          -16.9%
Hardness change (points)                       2               2
Heat aging 1,008 hours/125[degrees]C
Tensile (% change)                        -13.8%          -15.1%
Elongation (% change)                     -37.6%          -31.1%
Hardness change (points)                       8               8
Heat aging 70 hours/100[degrees]C
Tensile (% change)                         -0.1%            0.5%
Elongation (% change)                      -2.7%           -7.1%
Hardness change (points)                       1               1
Heat aging 70 hours/150[degrees]C
Tensile (% change)                         -3.1%          -12.2%
Elongation (% change)                     -12.9%          -10.5%
Hardness change (points)                       3               5
Heat aging 168 hours/125[degrees]C
Tensile (% change)                          3.7%            -6.1
Elongation (% change)                      -7.8%          -12.4%
Hardness change (points)                       2               3
Oil immersion data
IRM 903/70 hours/100[degrees]C
Tensile (% change)                        -11.3%           -8.9%
Elongation (% change)                     -22.0%          -16.9%
Hardness change (points)                     -20             -20
Volume swell (%)                            43.4            36.3
IRM 903!70 hours/125[degrees]C
Tensile (% change)                        -11.7%           -8.0%
Elongation (% change)                     -23.1%          -16.9%
Hardness change (points)                     -20             -21
Volume swell (%)                            46.9            35.4

Table 6--sulfur-containing cure data

                                            Tyrin
                                          CM 0136       CSM         CR

Mooney scorch (MS+1 Cad 125[degrees]C)
Init. viscosity (MU)                         56.7      60.2       21.5
Min. viscosity (MU)                          41.2      35.9       15.9
t3 (min.)                                   16.19      7.93        >25
t5 (min.)                                     >25      9.51         --
Mooney viscosity
ML(1+4) @ 100[degrees]C (MU)                105.6      96.0       19.9
Moving die rheometer (MDR)
Test temp. (C)                                160       160        160
ML (dNm)                                     2.77      2.03       1.26
MH (dNm)                                    21.83     22.35      16.94
ts2 (min.)                                   5.43      1.47       4.75
t50 (min.)                                  12.28      3.86      11.01
t90 (min.)                                  22.88      9.23      32.18
Original physical properties
25% modulus (MPa)                            3.14      1.53       1.25
100% modulus (MPa)                           8.15      8.72       4.55
200% modulus (MPa)                          12.29        --         --
Tensile strength (MPa)                       12.6      18.3       13.5
Elongation (%)                                346       179        248
Hardness (duro. A)                             86        76         70
Tear strength
Die C tear (N/mm)                            58.8      46.1       50.3
Compression set
70 h./1 00[degrees]C (%)                       18        51         29
70 hJ125[degrees]C (%)                         30        82         48
70 h./1 50-C (%)                               52        92         66
Abrasion (ISO 4649)
Volume loss ([mm.sup.3])                    209.2     140.2      152.1
Low temperature properties
Dynamic mechanical spectroscopy
[T.sub.g] (deg C)                             -28       -25        -34
tan [delta] @ [T.sub.g]                     0.491     1.026      0.950

ASTM D573 heat aging
Heat aging 1,008 hours/101[degrees]C
Tensile (change)                            14.6%     11.8%     -16.6%
Elongation (change)                        -39.0%    -10.6%     -66.1%
Hardness change (points)                        0         3         18
Heat aging 1,008 hours/125[degrees]C
Tensile (change)                            16.7%     -8.3%     -81.4%
Elongation (change)                        -65.3%    -57.0%    -100.0%
Hardness change (points)                        5        13         27
Heat aging 70 hours/100[degrees]C
Tensile (change)                             2.6%      8.9%      -1.8%
Elongation (change)                         -3.2%      3.4%     -10.1%
Hardness change (points)                       -1         2          6
Heat aging 70 hours/150[degrees]C
Tensile (change)                            24.2%     -5.1%     -52.5%
Elongation (change)                        -46.1%    -22.3%     -95.6%
Hardness change (points)                        2         7         24
Heat aging 168 hours/125[degrees]C
Tensile (change)                            19.3%      6.4%     -24.0%
Elongation (change)                        -38.3%     -9.5%     -80.2%
Hardness change (points)                        1         5         22
Oil immersion data
IRM 903/70 hours/100[degrees]C
Tensile (change)                            -3.7%    -10.8%     -38.9%
Elongation (change)                        -20.2%    -15.6%     -31.5%
Hardness change (points)                      -16       -11        -17
Volume swell (%)                             34.3      25.3       47.8
IRM 903170 hours/125[degrees]C
Tensile (change)                             1.0%    -19.8%      -50.6
Elongation (change)                        -38.9%    -19.6%     -38.7%
Hardness change (points)                      -16       -16        -21
Volume swell (%)                             36.1      32.4       52.3

                                                                  Tyrin
                                             NBR/     Tyrin     EXT 35%
                                              PVC       EXT    increase

Mooney scorch (MS+1 Cad 125[degrees]C)
Init. viscosity (MU)                         24.8      89.8          68
Min. viscosity (MU)                          12.5      72.3        58.8
t3 (min.)                                     >25      2.96         >25
t5 (min.)                                      --      4.31          --
Mooney viscosity
ML(1+4) @ 100[degrees]C (MU)                 22.2     141.9       128.1
Moving die rheometer (MDR)
Test temp. (C)                                160       160         160
ML (dNm)                                     0.99      4.91        4.47
MH (dNm)                                    12.66     23.41       14.38
ts2 (min.)                                   3.40      1.09        4.38
t50 (min.)                                   3.82      12.7       14.21
t90 (min.)                                   6.18     34.85       36.87
Original physical properties
25% modulus (MPa)                            1.59      3.07        2.81
100% modulus (MPa)                           4.67      8.83        7.52
200% modulus (MPa)                          10.35     16.32       11.90
Tensile strength (MPa)                       12.2      17.5        12.0
Elongation (%)                                404       346         311
Hardness (duro. A)                             74        85          84
Tear strength
Die C tear (N/mm)                            54.4      64.5        47.3
Compression set
70 h./1 00[degrees]C (%)                       74        19          40
70 hJ125[degrees]C (%)                         84        34          59
70 h./1 50-C (%)                              106        47          69
Abrasion (ISO 4649)
Volume loss ([mm.sup.3])                    202.3     162.1       149.7
Low temperature properties
Dynamic mechanical spectroscopy
[T.sub.g] (deg C)                             -16       -27         -42
tan [delta] @ [T.sub.g]                     0.679     0.538       0.470

ASTM D573 heat aging
Heat aging 1,008 hours/101[degrees]C
Tensile (change)                            54.3%      3.1%       13.7%
Elongation (change)                        -73.3%    -23.7%      -31.8%
Hardness change (points)                       18         1           3
Heat aging 1,008 hours/125[degrees]C
Tensile (change)                           -83.5%      1.1%        3.2%
Elongation (change)                       -100.0%    -58.1%      -51.8%
Hardness change (points)                       22         5           9
Heat aging 70 hours/100[degrees]C
Tensile (change)                            22.4%      4.5%        6.7%
Elongation (change)                        -30.7%     -8.1%       -7.9%
Hardness change (points)                        6         0           1
Heat aging 70 hours/150[degrees]C
Tensile (change)                            10.8%      7.8%        6.2%
Elongation (change)                       -100.0%    -34.1%      -40.7%
Hardness change (points)                       25         3           4
Heat aging 168 hours/125[degrees]C
Tensile (change)                            56.3%      8.1%       17.0%
Elongation (change)                        -83.7%    -24.9%      -32.8%
Hardness change (points)                       20         3           4
Oil immersion data
IRM 903/70 hours/100[degrees]C
Tensile (change)                             3.3%     -5.1%      -15.4%
Elongation (change)                        -24.0%    -25.4%      -22.7%
Hardness change (points)                       -4       -17         -16
Volume swell (%)                             21.8      42.4        32.9
IRM 903170 hours/125[degrees]C
Tensile (change)                           -29.7%     -2.7%      -18.4%
Elongation (change)                        -54.0%    -33.5%      -31.9%
Hardness change (points)                      -12       -18         -17
Volume swell (%)                             31.9      46.2        34.9

Figure 3--Mooney viscosity ML (1+4) @
100[degrees]C--peroxide cure

Tyrin CM 0136               8639
CSM                          111
NBR/PVC                     3938
Tyrin EXT 1000             123.1
Tyrin EXT +35% increase     99.4

Note: Table made from bar graph.

Figure 8--Tg from Rheometrics Dynamic
Spectroscopy (RDS-II)--peroxide cure

Tyrin CM 0136              -28
CSM                        -28
NBR/PVC                    -16
Tyrin EXT 1000             -28
Tyrin EXT +35% increase    -36

Note: Table made from bar graph.