Non-lead ECO elastomer compounds.

Polyepichlorohydrin elastomers (ECO) of ECH (homopolymer) and ECH/EO (copolymer) are fully saturated and as such the more traditional rubber cure systems are not used with them. Since the introduction of these elastomers in the 1960s, the most commonly used cure system has been ethylene thiourea (ETU) activated with lead, usually, but not exclusively, [Pb.sub.3][O.sub.4] (red lead oxide). Although this system has often been considered the industry norm for these elastomers, for many years there have been practical concerns with its use; not least, the known toxicity of lead and the reported carcinogenaity and teratogenaity of ETU, but also the formation of a lead bloom on steam cured parts and excessive fouling in molding operations. The latter is thought to be due principally to both lead complexes and ethylene urea depositing onto the mold surface during the vulcanization process.

Lead and lead containing materials have recently become more of an environmental issue. Existing EPA lead leachate limits in the U.S. have added urgency to the removal of lead based materials from rubber compounds, and the classification of materials with leachable lead as being hazardous waste has placed an additional burden on fabricators using the lead-ETU cure system. The imposition of a 5mg/l lead leachate limit means that not enough lead can be used in an ECO compound to be an effective and viable cure system. In Europe, car producers have already established dates for parts supplied to them to be lead-free. Recent European legislation (ref. 1) (Article 4.2(a)) has been introduced prohibiting the use of lead, cadmium, mercury and hexavalent chromium (VI) for all new cars and trucks from July 1, 2003. Some exceptions and exemptions currently exist, but elimination where avoidable will become mandatory by the above date. U.S. and European car producers are also acting to prohibit or limit the use of lead through existing governmental or self-imposed regulation.

These issues have led us to investigate non-lead activated cure systems for ECO elastomers, amongst them, the Zisnet F-PT curative (TCY) has been used in the development of recipes satisfying the requirements of a number of automotive and other specifications. This surface treated chemical, known variously as 2,4,6-trimercapto-1,3,5 triazine, trithiocyanuric acid (TCY) and trimercapto-sym-triazine, was introduced in 1978. A typical TCY cured compound will utilize calcium carbonate and magnesium oxide as activators (acid acceptors) in place of lead materials. Compounds can be accelerated with diphenylguanidine (DPG) and 3-methyl-thazolidene-2-thione and retarded with a sulfonamide derivative or N-cyclo-hexylthiophthalimide.

In addition to the TCY system, other cure systems are available (and many have been evaluated) for use with epichlorohydrin homopolymers, copolymers and terpolymers. Some of these examples are shown in table 1.

General characteristics and compounding

Physical properties of ECO compounds, such as heat resistance (air aging), fuel, oil, chemical and low-temperature properties are determined mainly by component monomer composition, rather than by cure chemistry. Cure chemistry certainly plays a role in the property performance, including the heat resistance of ECO compounds, but in addition, the requirements of individual automotive specifications and the processing considerations for differing products often require other specific compounding techniques be used. The challenge for ECO compounds, which utilize non-lead cure systems, is to provide equivalent or better performance than their lead based counterparts, while also competing with other potential elastomers that may offer lower cost with higher performance. The switch to non-lead systems must therefore be accomplished at similar or lower cost, as higher cost is unlikely to be accepted unless better overall performance can be demonstrated.

Due to the common use of lead in ECO compounds over many years, there has long been the acceptance by fabricators that its use is essential in order to maximize both heat and water resistance.

Heat resistance, particularly, is considered the key property to match when replacing lead with non-lead activators. ECO elastomers are known for their good balance of heat resistance, cold flexibility, ozone and oil and fuel resistance, hence their use in the automotive industry. They are rated by the ASTM D2000 classification system as CH (125[degrees]C) capable. However, performance at higher temperatures (up to 150[degrees]C) is often required for short periods. Typically, air aged test periods specified by automotive companies range from 70 to 168 hours @ 150[degrees]C and up to 1,000 hours @ 125[degrees]C to 135[degrees]C for ECO compounds.

Studies within Zeon laboratories (refs. 2-4) and at end-users have shown little adverse aging performance and, more importantly, that equivalent and, in some cases, better heat resistance can be obtained with the use of non-lead acid acceptors and curatives other than ETU. In previous testing, the TCY system has given some of the best overall balance of properties when replacing lead/ETU cure systems. This was an important reason why TCY was selected as the non-lead cure system of choice in this and many other developments in Zeon laboratories.

This article presents examples of compound development to two important automotive specifications where the non-lead TCY cure system in combination with other materials and compounding techniques has been used to meet heat aging and other specified requirements. Figures 1-4 illustrate the heat resistance capabilities of the TCY system compared to similar lead cured compounds under long term aging conditions at 125[degrees]C and 130[degrees]C. These data indicate that both aged property retention and actual values as a function of cure system are unremarkable, that is, there seems to be no indication of deleterious aging performance when the alternative TCY cure system is used.

[FIGURES 1-4 OMITTED]

With regard to water resistance, the use of a fumed silica filler with the TCY cure system results in volume changes in aqueous condensates which are comparable to a lead containing compound (table 2).

The two studies presented demonstrate practical examples of the development of compounds using the TCY cure system meeting two important automotive specifications. Both recipes have also been evaluated industrially. Other TCY cured compounds are already in use industrially in the U.S., Europe and Japan.

The specifications concerned here are: Ford: WSD M96D9-A2 issued March 2000 on fuel tubes; and VW: TL 524.24 issued October 2000 for the development of the cover stock of high pressure fuel hose with an FKM/ECO/ECO construction. The status of work conducted to other automotive specifications can be seen in table 3.

Experimental

The ECO elastomers used in this work were manufactured by Zeon Chemicals L.P.; the TCY is available from Zeon companies in the USA, Europe and Japan, while all other ingredients are available from standard raw material suppliers. The final evaluation recipes, together with their lead counterparts, are detailed in tables 4 and 5.

All compounds mixed in this study were prepared in a laboratory BR internal mixer with a chamber capacity of 1,135 cc. All were mixed in a single pass, upside-down procedure with a maximum discharge temperature of 120[degrees]C. Each curative system was added on a two-roll laboratory mill. No sticking was observed in either the internal mixer or on the two-roll mill. Test specimens were molded in a laboratory press under the conditions defined below. Testing was conducted in accordance with international standards and specific methods noted in each appropriate automotive specification. As has been noted, both recommended recipes have been evaluated industrially, and in addition, laboratory extrusion evaluations have been run on a cold feed extruder with a high intensity mixing screw to assess extrusion performance. All compounds extruded well, having a smooth appearance.

Curing conditions were selected with industrial practice in mind. For the Ford development, a press cure of 10' @ 180[degrees]C with a one hour post cure at 150[degrees]C was used, while for the VW development, a cure time of 35' @ 160[degrees]C without a post cure was selected to simulate steam autoclave curing conditions.

Results and discussion

For both developments, comparison of the test results from the lead/ETU cured compounds and the TCY cured compounds reveals that their cure rates are not dissimilar, but if anything, the TCY cured compounds are somewhat faster curing (tables 6 and 7). The cure states are also similar and generally correlate well with the original physical properties. Mooney viscosity measurement shows that values are generally higher for the TCY compounds, and this is particularly the case where the fumed silica has been used to improve aqueous condensate resistance. The use of lower viscosity base elastomers in this study (table 6) shows an improvement in this aspect.

Original property data tot all compounds can be seen in tables 8 and 9. The modulus values are generally similar, hut in the case of the VW development, none of the compounds, including the lead, actually meet the specification requirements. Each compound is similarly close to the Ford specified limit for this property. It is believed that this can be improved through further compound optimization, but it is possible that the issue may not be so critical that it could not be negotiated with the responsible automotive engineers. It may be relevant to note here that engineers have revised certain ECO targeted specifications to accommodate the use of non-lead systems. However, it is generally accepted that such revisions are not normally possible without data from functional testing.

Elongation values for the TCY cure system are higher than the lead compound in the Ford development (table 8) and similar to the lead compound (table 9) for the Volkswagen work. This is particularly important with respect to the VW development where high original elongation was necessary in order to meet the short-term aged requirement @ 150[degrees]C of greater than 200%. This was also the reason a high-structure HAF carbon black was selected in these compounds. The use of a blend with FEF black was evaluated to further optimize extrusion characteristics, while still meeting the specification requirements.

It has been found in many studies with TCY, that this cure system will generally give lower tensile strength than a similar lead/ETU compound. The cause of the tensile reduction with the TCY system is not fully understood, but is believed to be related to the significantly different crosslink structure. The lead/ETU system results in the formation of mono and disulfidic crosslinks, while the TCY system produces crosslinks with substantial molecular mass between the linked polymer chains. This same tensile reduction has been observed for other crosslink systems producing similar, long crosslinks. This characteristically lower tensile strength is observed in the VW development compounds (table 9). However, it does not detract from the ability of both evaluated recipes to comfortably meet the specified requirements. Attempts to increase tensile in the TCY system have met with limited success, but improvement has been achieved by adjusting the type and/or the amount of filler and plasticizer utilized in compounds. It can be observed that the addition of fumed silica in the Ford development compounds (table 8) does in Pact result in a substantially higher tensile strength value for both compounds, while also generating exceptionally high elongation.

Lead/ETU cured compounds generally provide excellent compression set values. In developments with the TCY cure system, higher compression set values are sometimes, but nut always, found. The optimization of the acid acceptor system, particularly the amount of magnesium oxide used (refs. 5 and 6), can improve upon this important property. In addition, optimization of the levels of both the TCY and accelerators can be effective, as can the use of a post cure, typically one to two hours @ 150[degrees]C.

As can be seen in tables 8 and 9, compression set values for the TCY cured compounds are in fact higher than for either lead compound. Nevertheless, all are able to satisfy the requirements for these fuel hose and tube specifications.

Aging in air and fluids

As noted previously, heat resistance, particularly, is considered as the key property to match when replacing lead with non-lead cure systems. Heat aging data seen in figures 1 to 4 and tables 10 and 11 demonstrate that in practical, optimized TCY based compounds, it is possible to both satisfy the requirements of existing automotive specifications while also matching closely the aging performance of similar lead based compounds. Figures 1 and 3 show that actual property values remain similar for both lead and TCY after long term (1,000 hours) aging at both 125[degrees]C and 130[degrees]C, even though for the Ford development (figure 4) the change in properties is larger for the TCY compounds. However, this situation is the contrary in the case of the Volkswagen compounds (figure 2), where better retention of properties is observed for both TCY compounds. The same trend is seen in figures 5 through 8 and tables 10 and 11 for the short-term heat aging performance at the higher temperature of 150[degrees]C. Again, of real significance is the fact that actual property values for the TCY compounds in comparison to the lead based compounds are very similar and in all cases meet the specified requirements.

[FIGURES 5-8 OMITTED]

At this time it may be useful to reiterate an earlier point. The heat aging data referred to above demonstrate that, in addition to the influence of a particular cure system, selection of the ECO polymer type and compound design through the use of other raw materials will also impact on the heat aging performance of ECO compounds. In the particular case of the TCY non-lead cure system, such selection can result in successfully meeting a specific set of requirements while not only matching, but also exceeding the performance of more traditional lead/ETU compounds.

The importance of compound design can be further explained in detail in relation to the two case studies presented here.

With respect to the Ford development, the requirements of fuel, aqueous acid condensate and aging resistance at 130[degrees]C and 150[degrees]C determined that a blend of homopolymer and copolymer would be needed. It was known that the TCY cure system was prone to high water swelling due to the nature of the typical acid acceptors (calcium carbonate, magnesium oxide) used with it forming water soluble chlorides during vulcanization. Data from other internal laboratory studies had shown that the addition of fumed silica would enhance resistance to aqueous solutions (in this case, an aqueous acidic condensate), and therefore this filler was utilized in combination with carbon black for additional reinforcement. Other raw materials such as antioxidant and plasticizer were selected to further balance low temperature and aging performance.

Results with respect to heat aging have been discussed. while tables 12 and 13 provide data on the performance in the IRM 903 test oil (7b and fuels specified (7a). Here, essentially equivalent performance for both cure systems is observed, although retention of elongation at break in both fuels is superior for the TCY cured compounds, while the opposite is true for the lead compound in the test oil. The data support the fact that oil and fuel resistance properties of ECO compounds are determined mainly by component monomer composition, rather than by cure chemistry. In addition, specific requirements such as acceptable aqueous resistance with the TCY system can be compounded for, through the use of other materials, in this case, filmed silica.

In contrast to the compound design for the single layer Ford fuel tube, the Volkswagen end product is a high-pressure fuel hose of construction FKM/ECO tie layer/ECO cover In this case, development concentrated on the cover, whine only contact with oil is specified. No direct fuel contact is expected and the requirement for resistance to oil is believed to reflect the possibility that the hose may suffer from occasional surface oil contact in service. Although not directly required, the study involved the evaluation of all compounds in a standard test fuel--ASTM Fuel B.

Review of the specification revealed that the most severe requirement was heat aging performance and, specifically, the need to retain more than 200% elongation at break following short term air aging at 150[degrees]C. Long term (1,000 hours) heat aging at 125[degrees]C was not expected to cause difficulty, particularly as other internal studies had by then identified that the accelerator, 3-methyl-thazolidene-thione-2, also contributed to improved long term heat aging performance with the TCY system. As fuel resistance was not directly specified, the selection of a single copolymer was made in combination with a high structure HAF carbon black to maximize original, un-aged elongation at break. It was believed that as high an original elongation as possible would assist in meeting the 150[degrees]C heat aged requirement. Original and aging data in tables 10 and 11 confirm this to be the case.

Table 14 indicates a more than satisfactory performance of the TCY cured compounds in both the fully synthetic 0W30 engine oil and in the standard ASTM test Fuel B (7b). This once again indicates that the resistance of ECO compounds to oil and fuels is less influenced by cure system than polymer composition.

Summary/conclusions

Lead is a known toxic substance and there is now a finite time before its use in automotive and other products becomes unacceptable. In Europe, the use of lead in automotive products will cease in the middle of 2003, and already its use by automotive companies around the world is prohibited or limited by existing or self-imposed regulation.

Many investigators in the U.S., Europe and Japan have evaluated the TCY cure system in the past with variable results. As more experience has been gained, so the suitability of TCY as a viable non-lead alternative has increased. Laboratory and industrial evaluations have shown it to be viable, and its use in industrial ECO compounds has and is increasing as the need to replace lead now becomes essential. Automotive companies in Japan have benefited from its use for many years.

The use of the TCY cure system in the two practical examples presented in this article provides evidence of this suitability as a non-toxic alternative to lead in ECO elastomer compounds. TCY has substantial cure rate latitude from retardation to acceleration and causes no adverse differences in the heat, fuel or oil resistance characteristics typically required in automotive products over their service lifetime. As well as being suited to extrusion applications, the TCY system has a lower tendency to foul molds than the lead/ETU cure system.

Through consideration of individual specification and product requirements, coupled with the use of other materials and compounding techniques, the key requirement of acceptable heat aging performance can be met with TCY. Importantly, this cure system has also been found to be cost competitive in comparison to lead and other systems. An area for caution with the TCY system concerns compound shelf life. Typically, this is no more than one to three weeks and can be considerably shorter in conditions of high humidity. This continues to be an ongoing area of study and it is hoped that improvements can be made and details published in the future.

A number of other alternatives, as detailed in table 1, is also available and automotive specifications are being met with these alternatives. Most of these systems have been investigated in other studies and, as with most materials, have both advantages and disadvantages. Most recent studies have been with the thiadiazole (Echo MPS) and thiadiazole derivative (Vanax 829) from Hercules and Vanderbilt, respectively.

Table 1 - non-lead curative systems for
polyepichlorohydrin

Thiadiazole                 Echo MPS
Thiadiazole derivative      Vanax 829
Bisphenol                   Dynamar
Phosphonium salt            Zeonet PB
Sulfur and peroxide         Ter polymers only
ETU only                    Calcium oxide
ETU only                    Magnesium oxide
6-methyl-quinoxaline-2,3-   Daisonet
dithiocarbamate

Table 2 - synthetic aqueous acid condensate resistance - use of
fumed silica

Synthetic aqueous acid       Spec   Lead   TCY     TCY
  engine condensate                              lower
  168 hrs. @ 90[degrees]C                        Mooney

Tensile strength,
  Mpa                      7.5 min.  10.5  12.4    11.8
Change in tensile
  strength, %                          -5    -8     -12
Elongation @ break, %      140 min.   250   370     360
Change in elongation
  @ break %                           -17   -20     -27
Hardness (plied sheet)       55 min    67    68      70
Change in hardness                     -3    -4      -3
Volume change, %                +12   7.5   7.1     2.3

Table 3 - ECO automotive specifications

The following specifications have been worked on and
lead-free solutions are available.

Ford      : WSD M96D9-A2 - fuel tubes
Ford      : ESE M2D241-A2 - fuel tubes
VW        : TL 524.24 - fuel hose (FKM/ECO/ECO)
VW        : TL 524.95 - fuel hose (THV/ECO/ECO)
Mercedes  : DBL 5565.20 - air ducts
Nissan    : NES 5301 Type 3 - fuel/emission tube
GM (US)   : GM 6148
Chrysler  : MS MEA 235 - fuel hose : cover

Other currently under development
Chrysler  : MS MEA 235 - fuel hose : tie layer
GM (US)   : GM 6276
Mercedes  : DBL 5565.21

Table 4 - Ford specification WSD M96D9-A2
formulations

                                    Lead     TCY     TCY
                                                   lower
                                                  Mooney

ECH/EO (C2000LL)                      65      65
ECH/EO (C2000XL)                                      65
ECH (H55)                             35      35
ECH (H45)                                             35
N330 HAF black                        20      15      15
N772 SRF black                        40      30      30
Untreated fumed silica                        15      15
Ether/ester plasticizer               10      10      10
Dibasic lead phosphite - 80%        12.5
Nickel dibutyl
  dithiocarbamate - 75%                2
Stearic acid                           1       1       1
Diphenylamine/alpha-methyl-
  styrene                                    1.5     1.5
4 & 5 - methyl mercapto
  benzimidazole                              0.5     0.5
Calcium carbonate                              5       5
Magnesium oxide                              1.5     1.5
Oleamide PA                                    1       1
Fatty acid ester PA                    2       1       1
TCY                                            1       1
Diphenyl guanidine                          0.45    0.45
Sulfonamide derivative - 80%                0.63    0.63
Ethylene Thiourea - 75%             1.38
Total                             188.88  183.58  183.58

Table 5 - Volkswagen TL 524.24 formulations

                                        Lead     TCY     TCY

ECH/EO                                   100     100     100
N339 HAF-HS                               50      50      25
N550 FEF                                                  25
Stearic acid                             1.5     1.5     1.5
Calcium carbonate                                  5       5
Magnesium oxide                                    3       3
Di-iso decyl phthalate                   7.5     7.5     7.5
Nickel dibutyl dithiocarbamate - 75%     1.5     1.5     1.5
Fatty acid ester PA                      1.5       1       1
Oleamide PA                                        1       1
Dibasic lead phosphite - 80%            12.5
TCY                                                1       1
3-methyl-thazolidene-thione-2                      1       1
Sulfonamide derivate - 80%                      0.25    0.25
Ethylene thiourea                       1.33
Total                                 175.83  172.75  172.75

Table 6 - rheological properties - Ford

                                 Lead     TCY     TCY
ODR cure properties: 30'/                       lower
185[degrees]C/3[degrees]arc                    Mooney

Min. torque ML inch lbs.            7      15      14
Max. torque MH inch lbs.           80      88      88
MH - ML inch lbs.                  73      73      74
Ts 02 minutes                     1.1    0.92    0.82
Tc50 minutes                      4.8     3.5     3.4
Tc 90 minutes                    15.5    11.7    12.0

MV2000 properties
Mooney ML 1+4 @ 100[degrees]C      45      74      63
Mooney ML 1+4 @ 120[degrees]C      40      76      61
Scorch time @ Ts5                 7.0     4.7     4.6
Scorch time @ Ts10                8.5     5.6     5.5
Scorch time @ Ts35               12.2     7.9     7.6

Table 7 - rheological properties - Volkswagen

                                 Lead   TCY:   TCY:
MDR cure properties: 15'/                HAF   HAF/
175[degrees]C/0.5[degrees] arc                  FEF

Min. torque ML inch lbs.          2.8    2.9    2.1
Max. torque MH inch lbs.           17     20     16
Ts 02 minutes                     1.1    0.9    1.0
Tc 50 minutes                     3.9    3.4    3.0
Tc 90 minutes                    10.8   10.0    9.7

MV2000 properties
Mooney ML 1+4 @ 120[degrees]C      61     70     65
Scorch time @ Ts5                 5.9    4.6    4.1
Scorch time @ Ts10                7.1    5.7    5.2
Scorch time @ Ts35                9.9    8.6    8.5

Table 8 - original properties - Ford

                                         Lead    TCY      TCY
                                                        lower
Physical properties               Spec                 Mooney

Hardness, durometer A            65-75     70     72       73
  (plied sheet)
Tensile strength, Mpa          10 min.     11   13.5     13.4
M @ 100%, Mpa                   3 to 6    3.2    3.4      3.1
Elongation @ break %          200 min.    300    460      490
Compression set
Small specimen 22 hours        30 max.   14.7     16       26
  @ 100[degrees]C%
Tear strength - ASTM D624
  Die C : kN/m                 25 min.     43     41       42

Low temperature flexibility
180[degrees] bend                 Pass   Pass   Pass     Pass
  @ -40[degrees]C/24 hrs.

Table 9 - original properties - Volkswagen

                               Lead   TCY:   TCY:
Physical properties                    HAF   HAF/        Spec
                                              FEF

Hardness, durometer A
  (plied sheet)                  70     72     67       63-73
Tensile strength, Mpa            18   14.7   14.6     10 min.
Elongation @ break, %           470    400    430    250 min.
Modulus @ 100% ext. Mpa         3.2    3.9    3.8      4 min.
Tear strength (N/mm)             27     32     29      5 min.

Compression set
Small specimen 24 hrs.
  @ 135[degrees]C %              37   51.7   47.9     60% max
In acc. VDA 675 218

Low temperature mandrel
  bend
180[degrees]; 24 hrs.
  @ -35[degrees]C              Pass   Pass   Pass   No cracks

Ozone resistance
200 pphm, 25[degrees]C, 60%
  humidity; 46 hrs.; 20%
  extension                    Pass   Pass   Pass   No cracks

Table 10 - heat aging properties - 150[degrees]C and
130[degrees]C - Ford

                                                    Lead  TCY      TCY
                                                                 lower
Air (Geer oven) 168 hrs. @ 150[degrees]C      Spec              Mooney

Tensile strength, Mpa                       7 min.   7.3   8.5     7.5
Change in tensile strength %                         -34   -37     -44
Elongation @ break, %                      80 min.   230   190     200
Change in elongation @ break, %                      -23   -59     -59
Hardness (plied sheet)                    50 to 90    79    80      74
Change in hardness                                     9     8       1
180 degree bend @ -40[degrees]C/24 hrs.       Pass  Pass  Pass    Pass

Air (Geer oven) 1,000 hrs.
  @ 130[degrees]C
Tensile strength, Mpa                     6.5 min.   8.1   7.7     7.5
Change in tensile strength, %                        -26   -43     -44
Elongation @ break %                       90 min.   180   190     180
Change in elongation @ break, %                      -40   -59     -63
Hardness (plied sheet)                    50 to 90    80    80      81
Change in hardness                                    10     8       8
180 degree bend @ -40[degrees]C/24 hrs.       Pass  Pass  Pass    Pass

Table 11 - heat aging properties - 150[degrees]C and
125[degrees]C - Volkswagen

                                  Lead   TCY:   TCY:      Spec
Air (Geer oven) 72 hrs.                   HAF   HAF/
  at 150[degrees]C                               FEF

Tensile strength, Mpa             15.0   13.4   11.2   10 min.
Change in tensile strength, %      -17     -9    -23
Elongation @ break, %              250    245    210  200 min.
Change in elongation Q break, %    -47    -39    -51
Hardness (durometer A -
  plied sheet)                      80     79     73
Change in hardness                  10      7      6  0 to +10

Air (Geer oven) 1,000 hrs. at
  125[degrees]C
Tensile strength, Mpa              9.5   11.2   10.7    8 min.
Change in tensile strength, %    -47.2  -23.8  -26.7
Elongation @ break, %              190    230    185  130 min.
Change in elongation Q break, %  -59.6  -42.5  -57.0
Hardness (durometer A -
  plied sheet)                      81     81     77
Change in hardness                  11      9     10  0 to +12

Table 12 - aging in synthetic aqueous acid engine condensate
and oil - Ford

Synthetic aqueous acid engine                     Lead    TCY     TCY
  condensate                               Spec                 lower
168 hrs. @ 90[degrees]C                                            ML

Tensile strength, Mpa                  7.5 min.   10.5   12.4    11.8
Change in tensile strength, %                       -5     -8     -12
Elongation @ break %                   140 min.    250    370     360
Change in elongation @ break, %                    -17    -20     -27
Hardness (plied sheet)                  55 min.     67     68      70
Change in hardness                                  -3     -4      -3
Volume change %                             +12    7.5    7.1     2.3

IRM 903 oil 168 hrs. @ 150[degrees]C
Tensile strength, Mpa                    6 min.    9.3   10.5    11.2
Change in tensile strength, %                      -15    -22     -16
Elongation @ break %                   100 min.    245    180     190
Change in elongation @ break, %                    -18    -61     -61
Hardness (plied sheet)                 55 to 80     67     78      79
Change in hardness                                  -3      6       6
Volume change, %                      -5 to +15    6.5    1.9     0.2

Table 13 - aging in fuel C and Fuel C/methanol blend - Ford

                                            Lead   TCY        TCY
Fuel C 70 hrs. @ 23[degrees]C        Spec                lower ML

Tensile strength, Mpa              4 min.    7.2     8        7.8
Change in tensile strength, %                -35   -41        -42
Elongation @ break %             100 min.    180   250        255
Change in elongation @ break, %              -40   -46        -48
Hardness (plied sheet)           45 to 75     54    54         54
Change in hardness                           -16   -18        -19
Volume change, %                 0 to +40     34    33         31

Fuel C+15% methanol 70 hrs.
  @23[degrees]C
Tensile strength, Mpa              3 min.    4.4   4.7        4.3
Change in tensile strength, %                -60   -65        -68
Elongation @ break, %             80 min.    115   150        150
Change in elongation @ break, %              -62   -67        -69
Hardness (plied sheet)           40 to 75     48    42         42
Change in hardness                           -22   -30        -31
Volume change, %                 0 to +75     72    72         70

Table 14 - aging in synthetic oil and fuel B -
Volkswagen

VW Saturn 1st fill oil (OW-30) -         Lead   TCY:   TCY:
  72 hrs. Q 100[degrees]C                       HAF    HAF/      Spec
                                                       FEF

Tensile strength, MPa                    12.8   13.6           7 min.
Change in tensile strength, %             -29     -7
Elongation @t break, %                    270    280          150 min.
Change in elongation @ break, %           -43    -30
Hardness (durometer A - plied sheet)       73     76
Change in hardness                          3      4             +/-5
Weight change, %                         -1.7   -1.4             +/-5
Specified test oil = Cecilia 20 5W-40

Fuel B 72 hrs. @ 40[degrees]C                                 No req.
Tensile strength, MPa                    13.6   11.5   11.2
Change in tensile strength, %             -24    -22    -23
Elongation @ break, %                     330    260    230
Change in elongation at break, %          -30    -35    -47
Hardness (durometer A - plied sheet)       56     58     56
Change in hardness                        -14    -14    -11
Volume change, %                         19.2   14.9   15.3

References

1. European Community Directive 2000/53/EC on end-of- life vehicles, 18th September 2000.

2. V.L. Kyllingstad and C.J. Cable, "Lend-ETU free curing of polyepichlorohydrin rubber compounds," Speciality & High Performance Rubber Conference, RAPRA Technology Ltd, Shawbury, England, December 1992.

3. C.J. Cable and C.T. Smith, "Epichlorohydrin in fuel hose," Rubber Division Meeting, Louisville, KY, October 1996.

4. K. Nakajima, M. Oyama and K. Hashimoto, "Direct adhesion between FKM and GECO or between FKM and NBR/PVC," Rubber Division Meeting, Chicago, IL, April 1994.

5. TCY--Special Curative for Epichlorohydrin rubber--Zeon Product publication.

6. K. Hashimoto, Masaaki Inagami, Akio Maeda and Noburu Watanabe, "Epichlorohydrin rubber vulcanized with triazine thiols," Rubber Division meeting, Altlanta, GA, October 1986.

7. ASTM D471 Rubber property--effects of liquids: a) Table 1, ASTM reference oils; b) Table 2, ASTM reference fuels.

This article is based on a paper given at the October 2001 meeting of the Rubber Division