Printer Friendly

Cure system effect on low temperature dynamic shear modulus of natural rubber.

Natural rubber (NR) is used in many dynamic applications. Its ability to strain crystallize imparts high physical properties. These properties can develop at light levels of loading, which along with polymer structure, can result in low levels of damping, ideal for rubber isolators.

Cure systems are known to affect low temperature properties. In natural rubber, modulus increases with progressive levels of crystallization. The degree of crosslinking is known to affect the amount of crystallization (ref. 1).

Service temperature of natural rubber is limited at the high end to approximately 80[degrees]C, depending on cure system. At the lower end, natural rubber has a glass transition temperature of -72[degrees]C, but it becomes effectively non-compliant much before this.

A designer desires constant spring rates for critical applications. Unfortunately, rubber properties, including modulus, are affected by time, temperature, strain history, frequency, etc. The rapid increase in modulus at lower temperatures may be avoided, to a degree, in formulation development by using polymers with very low Tgs such as polybutadiene (BR) or silicone (MVQ). However, these polymers do not possess the strength and fatigue resistance properties of NR. Lower temperature properties of NR can be improved by polymer blending, use of plasticizing oils, or by varying the cure system.

The methodology for measuring lower temperature shear modulus was explored on a servohydraulic dynamic tester. Also, a variety of cure systems was studied in lightly filled natural lubber. The shear modulus changes can be applied in engineering applications where time and temperature dependent changes in modulus are important. A 48 hour soak (exposure at temperature) is the primary evaluation period, simulating a weekend of exposure at temperature without use.

Large crosslinks, sulfur or various longer crosslinks, show a marked delay in modulus increase as compared to short crosslinks formed with lightly crosslinked peroxide and EV sulfur cure systems. High crosslink density cure systems are still best at minimizing the crystallization induced modulus increase at low temperatures (ref. 2).

Several alternate cure systems and variations on traditional sulfur cure systems exist today. These systems ale used for a variety of intended purposes, including heat resistance, fatigue and reversion resistance. An evaluation of the low temperature vs. room temperature modulus change was made for these crosslink systems. Some of these introduce large molecules into the crosslink. These large molecules could interfere with some crystallization and thereby minimize modulus increase. Most of the studied systems are shown in table 1.

* Sulfur cured systems at various sulfur levels;

* peroxide cure system (DCP);

* peroxide cure system with coagent TMPTMA;

* low sulfur systems with Na-HMT;

* low sulfur systems with CIMB;

* low sulfur systems with BDBzTH; and

* low sulfur systems with NPDI or urethane.

The cure system components CIMB, Na-HMT, BDBZTH and in some cases urethane are primarily intended to reduce reversion during cure in high sulfur systems. They become part of the crosslink system. Since the molecules are so bulky, it was decided to examine their influence on lower sulfur cure systems, and their influence on crystallization.

The urethane cure system introduces a very large molecule into the crosslink. Similarly, during peroxide vulcanization, the coagent TMPTMA can become part of the crosslink system.

Experimental

Simple base formulations were used for the evaluation and are shown in table 2. Formulations were mixed in two passes on a laboratory internal mixer.

Modulus measurements were made using dual lap shear samples on a servohydraulic dynamic test machine (ref. 3). Samples were cured and bonded 30 minutes at 160[degrees]C. The rubber cross-sectional dimensions were 50.8 mm x 6.35 mm x 12.7 mm for each shear rubber portion.

A 15 minute 100[degrees]C soak and a 15 minute 23[degrees]C cool down was used prior to indicated soak conditions to remove residual crystallization. The samples were then immediately subjected to the soak temperature, with no ramping or stepping of temperature.

Samples strained to [+ or -] 10% displacement at 20 Hz were noted to have little detected change in dynamic modulus. This contradicted quasi static test results from load displacement tests.

The high damping at low temperature results in immediate internal heat generation, and therefore an almost immediate decrease in modulus. This rate of change will be a function of energy input into the system. Figure 1 shows how quickly the modulus changes with each sinusoidal cycle. When the sample is forced to a specified 10% amplitude in displacement control, the percent modulus change is rapid. Instead, if measurements are taken for forces of [+ or -] 222 N, the rate of change is minimal, especially during the first 20 cycles. In order to reflect a real world application, all further testing was revised. Instead of a displacement based amplitude, a force based amplitude was chosen. Samples were strained to [+ or -] 222 N at 20 Hz. Dynamic modulus measurements with the servohydraulic system were made through a sine regression calculation over the first eight cycles. Measurements were taken at described temperatures and compared with room temperature (23[degrees]C) results.

[FIGURE 1 OMITTED]

Discussion

The focus of this article is the effect of the crosslink system on dynamic modulus change with decreasing temperature. It is known that there is an inverse relationship between state of cure and degree of crystallization (ref. 1). Highly crosslinked systems result in a delayed increase in modulus. This has been attributed to steric interference with crystallite formation.

Indeed, measurements of dynamic modulus in the base formulation with varying sulfur levels show a marked difference in modulus at lower temperatures (figure 2). The decreasing state of cure with less sulfur shows more dramatic increases in modulus, especially at the lowest 0.5 phr level.

[FIGURE 2 OMITTED]

Low sulfur and urethane systems

Figure 2 showed that the most pronounced changes in modulus occurred with the lowest sulfur formulation. It was decided to modify this 0.5 phr sulfur level cure system with the cure components Na-HMT, CIMB, BDBzTH and NPDI, and to test a no sulfur NPDI cure system. Figure 3 and table 3 show the resulting changes in modulus.

[FIGURE 3 OMITTED]

All of the modified cure systems show a much smaller change in modulus with decreasing temperature. The system with a high level of BDBzTH was influenced by temperature the least. Table 3 shows these data. The 100% and 300% modulus and G * can be an indicator of cure state changes. The indication is that for most the cure state changes little, but the modulus change is greatly affected.

Figure 3 shows that BDBzTH at 3 phr performs the best. However, table 3 clearly shows that at the high 3 phr level, BDBzTH has an increased state of cure. The 1 phr BDBzTH, 3 phr CIMB and 1 phr Na-HMT all show improvements at low temperature with similar cure states. Na-HMT at higher levels (3 phr) does not perform as well as when used at the lower 1 phr level.

1.0 phr sulfur level

A similar improvement in change with temperature is noted at the higher 1.0 sulfur level (figure 4). The CIMB and BDBzTH perform slightly better than the Na-HMT. Material properties from table 4 indicate cure state is similar for most, but begins to increase at the higher level of BDBzTH. Again, the high 3 phr level Na-HMT does not perform as well as the other modified crosslinks.

[FIGURE 4 OMITTED]

Peroxide cure system

An experimental design and results are shown in table 5, examining the effect of dicumyl peroxide level and TMPTMA coagent level on modulus. Figure 5 illustrates the effect on room temperature modulus. Regression coefficients are shown in table 6 with Rsq = 99.2%, and are based on the coded levels of table 5.

[FIGURE 5 OMITTED]

Figure 6 illustrates the effect on change in modulus at -30[degrees]C. Similar changes were noted at -10[degrees]C and at -40[degrees]C. Increasing peroxide or coagent significantly reduces changes in modulus at low temperatures. This is expected as the crosslink density increases in either case. Regression coefficients of table 7 show that the peroxide levels have a greater influence at low temperature. Peroxide level has a greater impact than coagent level.

[FIGURE 6 OMITTED]

If a comparison is attempted at similar states of cure, it appears that the coagent effect is limited to increasing the state of cure, and hence modulus change. Compare table 5 formulations C and E. Both have similar cure state (as measured my 100%, 300% tensile modulus and room temperature shear modulus). However, the low temperature modulus change is less pronounced for the higher peroxide level formulation E. A similar example is a comparison of formulations B and D.

Change in modulus over time

Samples were given a 48 hour soak and then held for longer periods of time to evaluate longer-term modulus change. Figure 7 shows that the very low sulfur level of recipe R1.1 (table 8) is very, stiff, while the modified recipes did not stiffen as much. The high sulfur recipes remain much softer. Data are compiled in table 8.

[FIGURE 7 OMITTED]

Conclusion

Formulating for applications requiring high strength, high fatigue natural rubber compounds operating in temperature regions less than 0[degrees]C can require careful consideration of the cure system. Higher sulfur systems will provide comparatively smaller dynamic modulus increases at lower temperatures. However, applications that require improved heat and aging resistance can be served by semi-EV cure systems or very low sulfur systems with long chain crosslink modifiers. These longer chain crosslink modifications can serve to minimize changes in dynamic modulus with temperature and time. Similarly, higher crosslink densities in peroxide cure systems, through coagents or increased peroxide, can also minimize changes in dynamic modulus with temperature and time. For sulfur crosslink systems, modification with CIMB or BDBzTH offers the best low temperature performance. Crosslink modification is one tool that can be used for low temperature natural rubber optimization.

References

(1.) Vulcanization of Elastomers, ed. F. Alliger and I.J. Sjothun, Reinhold Publishing 1964, p. 95-121.

(2.) Natural Rubber Science and Technology; ed. A.D. Roberts. Oxford University Press 1988, Ch. 18, A. Stevenson.

(3.) "Comparison of dynamic test methods and machines for elastomers," R.J. Del Vecchio, ACS Rubber Division Meeting Oct. 1993.
Table 1

Name Chemical name
DCP Dicumyl peroxide
TMPTMA Trimethylolpropane trimethacrylate
Na-HMT Hexamethylene-1,6-bisthiosulfate
 disodium salt, dihydrate
CIMB 1,2-bis (citraconimidomethyl)benzene
BDBzTH 1,6-Bis (N,N'-dibenzylthiocarbamoyldithio)
hexane
NPDI Nitrosophenol/methylene di-isocyanate
 or urethane adduct

Table 2--formulations

 Sulfur Peroxide
 and urethane

CV-60 natural rubber 100 100
N550 carbon black 1 1
Stearic acid 2 --
Zinc oxide 3 --
PTMQ 1.5 1.5
IPPD 1.5 --
Wax 2 2
Z-MB2 -- 2
70% dicumyl peroxide -- Variable
72% TMPTMA -- Variable
CBS Variable --
Sulfur Variable --

Table 3--formulations and results for 0.5 phr sulfur experiments

Low sulfur level

ID R1.1 R1.2 R1.3

CV-60 100 100 100
N550 1 1 1
Stearic Acid 2 2 2
ZnO 3 3 3
PTMQ 1.5 1.5 1.5
IPPD 1.5 1.5 1.5
Wax 2 2 2

Second cycle ingredients
CBS 2 2 2
Sulfur 0.5 0.5 0.5
Na-HMT -- -- --
CIMB -- 1 3
BDBzTH -- -- --
NPDI -- -- --
ZDMC -- -- --
TMTM -- -- --
Total 113.5 114.5 116.5

Hardness (durometer A) 32 34 34
Tensile (MPa) 10.6 10.2 10.9
Elongation (%) 791 712 791
100% modulus (MPa) 0.59 0.63 0.61
300% modulus (MPa) 1.5 1.4 1.3

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 445 442 457
G' (kPa) 445 442 456
Tan delta 0.05 0.06 0.06

 G* % change, 48 hrs. soak at temperature

 4[degrees]C 6% 4%

 -10[degrees]C 19% 27% 22%
 -20[degrees]C 259% 98% 64%
 -30[degrees]C 481% 165% 107%
 -40[degrees]C 830% 250% 200%

ID R1.4 R1.5 R1.6

CV-60 100 100 100
N550 1 1 1
Stearic Acid 2 2 2
ZnO 3 3 3
PTMQ 1.5 1.5 1.5
IPPD 1.5 1.5 1.5
Wax 2 2 2

Second cycle ingredients
CBS 2 2 2
Sulfur 0.5 0.5 0.5
Na-HMT 1 3 --
CIMB -- -- --
BDBzTH -- -- --
NPDI -- -- 4
ZDMC -- -- --
TMTM -- -- --
Total 114.5 116.5 115.7

Hardness (durometer A) 35 35 32
Tensile (MPa) 11.9 11.8 9.7
Elongation (%) 745 764 596
100% modulus (MPa) 0.63 0.58 0.68
300% modulus (MPa) 1.4 1.1 1.5

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 459 451 449
G' (kPa) 459 450 448
Tan delta 0.05 0.06 0.07

 G* % change, 48 hrs. soak at temperature

 4[degrees]C 4% 13%

 -10[degrees]C 21% 55% 17%
 -20[degrees]C 99% 96%
 -30[degrees]C 114% 269% 117%
 -40[degrees]C 225% 370% 242%

ID R1.7 R1.8 R1.9

CV-60 100 100 100
N550 1 1 1
Stearic Acid 2 2 2
ZnO 3 3 3
PTMQ 1.5 1.5 1.5
IPPD 1.5 1.5 1.5
Wax 2 2 2

Second cycle ingredients
CBS 2 2 --
Sulfur 0.5 0.5 --
Na-HMT -- -- --
CIMB -- -- --
BDBzTH 1 3 --
NPDI -- -- 6.7
ZDMC -- -- 2
TMTM -- -- 1
Total 114.5 116.5 120.7

Hardness (durometer A) 36 39 35
Tensile (MPa) 13.8 14.3 13.0
Elongation (%) 517 479 527
100% modulus (MPa) 0.68 0.83 0.79
300% modulus (MPa) 2.0 2.7 2.0

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 437 520 488
G' (kPa) 437 520 487
Tan delta 0.04 0.02 0.06

 G* % change, 48 hrs. soak at temperature

 4[degrees]C

 -10[degrees]C 15% 11% 23%
 -20[degrees]C 25% 21%
 -30[degrees]C 92% 42% 231%
 -40[degrees]C 195% 77% 420%

Table 4--formulations, results for 1.0 phr sulfur experiments

Sulfur level at 1 phr

ID R2.1 R2.2 R2.3

CV-60 100 100 100
N550 1 1 1
Stearic acid 2 2 2
ZnO 3 3 3
PTMQ 1.5 1.5 1.5
IPPD 1.5 1.5 1.5
Wax 2 2 2

Second cycle ingredients
CBS 1.6 1.6 1.6
Sulfur 1 1 1
CIMB -- 3 --
Na-HMT -- -- 3
BDBzTH -- -- --
Total 113.6 116.6 116.6

Hardness (durometer A) 36 36 35
Tensile (MPa) 13.7 12.3 13.7
Elongation (%) 857 835 856
100% modulus (MPa) 0.72 0.70 0.69
300% modulus (MPa) 1.74 1.59 1.54
G* (23[degrees]C) (kPa) 474 442 491
G' (23[degrees]C) (kPa) 474 491 490
Tan delta (23[degrees]C) 0.04 0.05 0.05

 G* % change, 48 hrs. soak at temperature

 4[degrees]C 3% 4% 9%

 -10[degrees]C 12% 13% 19%
 -20[degrees]C 47% 26% 39%
 -30[degrees]C 103% 39% 75%
 -40[degrees]C 141% 60% 87%

ID R2.4 R2.5

CV-60 100 100
N550 1 1
Stearic acid 2 2
ZnO 3 3
PTMQ 1.5 1.5
IPPD 1.5 1.5
Wax 2 2

Second cycle ingredients
CBS 1.6 1.6
Sulfur 1 1
CIMB -- --
Na-HMT -- --
BDBzTH 1 3
Total 114.6 116.6

Hardness (durometer A) 38 42
Tensile (MPa) 15.6 12.9
Elongation (%) 430 408
100% modulus (MPa) 0.84 1.05
300% modulus (MPa) 2.66 3.81
G* (23[degrees]C) (kPa) 499 597
G' (23[degrees]C) (kPa) 499 597
Tan delta (23[degrees]C) 0.02 0.02

 G* % change, 48 hrs. soak at temperature

 4[degrees]C

 -10[degrees]C 13% 11%
 -20[degrees]C
 -30[degrees]C 30% 33%
 -40[degrees]C 44% 43%

Table 5--experimental design and results for peroxide/coagent experiment

Peroxide/coagent design Perox./ Perox./ Perox./
 coa. coa. coa.
 A B C

CV-60 100 100 100
N550 1 1 1
PTMQ 1.5 1.5 1.5
Wax 2 2 2
Z-MB2 2 2 2

Second cycle ingredients
70% dicumyl peroxide 1.43 1.43 1.43
SR 350-72% 0 5 10
Total: 107.93 112.93 117.93

Hardness (durometer A) 27 35 39
Tensile (MPa) 4.51 14.04 14.78
Elongation (%) 593 544 479
100% modulus (MPa) 0.46 0.74 0.86
300% modulus (MPa) 0.93 2.12 3.49

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 324 429 508
G' (kPa) 322 428 508
Tan delta 0.10 0.07 0.07

 G* % change, 48 hr. soak at temperature

 -10[degrees]C 584% 98% 46%
 -30[degrees]C 743% 639% 328%
 -40[degrees]C 903% 661% 407%
Coded perox. level -1 -1 -1
Coded coagent level -1 0 1

Peroxide/coagent design Perox./ Perox./ Perox./
 coa. coa. coa.
 D E F

CV-60 100 100 100
N550 1 1 1
PTMQ 1.5 1.5 1.5
Wax 2 2 2
Z-MB2 2 2 2

Second cycle ingredients
70% dicumyl peroxide 2.714 2.714 2.714
SR 350-72% 0 5 10
Total: 109.214 114.214 119.214

Hardness (durometer A) 35 39 44
Tensile (MPa) 9.51 15.23 12.20
Elongation (%) 533 452 375
100% modulus (MPa) 0.72 0.97 1.23
300% modulus (MPa) 1.73 3.37 6.32

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 399 509 646
G' (kPa) 398 508 646
Tan delta 0.06 0.05 0.05

 G* % change, 48 hr. soak at temperature

 -10[degrees]C 27% 18% 17%
 -30[degrees]C 296% 58% 46%
 -40[degrees]C 474% 116% 159%
Coded perox. level 0 0 0
Coded coagent level -1 0 1

Peroxide/coagent design Perox./ Perox./ Perox./
 coa. coa. coa.
 G H I

CV-60 100 100 100
N550 1 1 1
PTMQ 1.5 1.5 1.5
Wax 2 2 2
Z-MB2 2 2 2

Second cycle ingredients
70% dicumyl peroxide 4 4 4
SR 350-72% 0 5 10
Total: 109.5 114.5 119.5

Hardness (durometer A) 35 42 46
Tensile (MPa) 7.08 10.46 7.45
Elongation (%) 374 349 259
100% modulus (MPa) 0.79 1.13 1.50
300% modulus (MPa) 1.92 4.43

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 452 630 785
G' (kPa) 452 630 785
Tan delta 0.04 0.03 0.03

 G* % change, 48 hr. soak at temperature

 -10[degrees]C 15% 10% 11%
 -30[degrees]C 108% 31% 22%
 -40[degrees]C 132% 53% 41%
Coded perox. level 1 1 1
Coded coagent level -1 0 1

Peroxide/coagent design Perox./
 coa. Rep E
 J E2

CV-60 100 replicate
N550 1 of E
PTMQ 1.5
Wax 2
Z-MB2 2

Second cycle ingredients
70% dicumyl peroxide 2
SR 350-72% 10
Total: 117.5

Hardness (durometer A) 39
Tensile (MPa) 13.49 14.90
Elongation (%) 442 444
100% modulus (MPa) 1.01
300% modulus (MPa) 4.12

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 610 506
G' (kPa) 609 505
Tan delta 0.05 0.05

 G* % change, 48 hr. soak at temperature

 -10[degrees]C 21% 17%
 -30[degrees]C 112% 55%
 -40[degrees]C 185% 110%
Coded perox. level -0.5 0
Coded coagent level 1 0

Peroxide/coagent design
 Rep E
 E2

CV-60 replicate
N550 of E
PTMQ
Wax
Z-MB2

Second cycle ingredients
70% dicumyl peroxide
SR 350-72%
Total:

Hardness (durometer A)
Tensile (MPa) 15.30
Elongation (%) 459
100% modulus (MPa)
300% modulus (MPa)

Dynamic @ 20 Hz, [+ or -] 222 N amplitude
G* (kPa) 508
G' (kPa) 508
Tan delta 0.05

 G* % change, 48 hr. soak at temperature

 -10[degrees]C 20%
 -30[degrees]C 58%
 -40[degrees]C 111%
Coded perox. level 0
Coded coagent level 0

Table 6--regression analysis peroxide/coagent design of table 5 for
room temperature (23[degrees]) complex modulus (G*)*--levels are
coded according to table 5

Stat. Regr. coefficients; Var.: GRTCOMPL; R-sqr = .99217;
 adj.:98565
Experimental 2 factors, 1 block, 12 runs; MS residual = 225.0564
Design DV. GRTCOMPL

 Regressn.
Factor Coeff. Std. Err. t(6) p

Mean/Interc. 515.127 * 7.65 * 67.30 * .000000 *
1. PeroxLV (L) 99.005 * 6.04 * 16.39 * .000003 *
 PeroxLV ^2 (Q) 3.656 9.21 0.40 0.705108
2. CoagLV (L) 131.358 * 5.78 * 22.74 * .000000 *
 CoagLV ^2 (Q) 5.646 9.07 0.62 0.556431
 1L by 2L 34.098 * 7.34 * 4.64 * .003529 *

 -95.00% -95.00%
Factor cnf. limit cnf. limit

Mean/Interc. 496.4 * 533.9 *
1. PeroxLV (L) 84.2 * 113.8 *
 PeroxLV ^2 (Q) -18.9 26.2
2. CoagLV (L) 117.2 * 145.5 *
 CoagLV ^2 (Q) -16.5 27.8
 1L by 2L 16.1 * 52.1 *

Table 7--regression analysis peroxide/coagent design of table 5 for
-30[degrees]C percent change in complex dynamic modulus (G*)--levels
are coded according to table 5

Stat. Regr. Coefficients; Var.: C_30BIG; R-sqr. = .96915;
 adj.:.94344
Experimental 2 factors, 1 block, 12 runs; MS residual = 3464.149
Design DV: C_30BIG

 Regressn
Factor Coeff. Std. Err. t(6) p

Mean/Interc. 87.211 * 30.03 * 2.90 * .027180 *
1. PeroxLV (L) -256.630 * 23.69 * -10.83 * .000037 *
 PeroxLV ^2 (Q) 202.436 * 36.13 * 5.60 * .001377 *
2. CoagLV (L) -128.037 * 22.66 * -5.65 * .001318 *
 CoagLV ^2 (Q) 32.112 35.57 0.90 0.401476
 1L by 2L 84.243 * 28.81 * 2.92 * .026495 *

 -95.00% -95.00%
Factor Cnf. limit Cnf. limit

Mean/Interc. 13.7 * 160.7 *
1. PeroxLV (L) -314.6 * -198.7 *
 PeroxLV ^2 (Q) 114.0 * 290.8 *
2. CoagLV (L) -183.5 * -72.6 *
 CoagLV ^2 (Q) -54.9 119.2
 1L by 2L 13.7 * 154.7 *

Table 8--change in modulus with time--samples exposed -30[degrees]C for
indicated time--actual modulus (G*) and percent change shown

 ID: R1.1 SM SH SHH

CV-60 100 100 100 100
N550 1 1 1 1
Stearic acid 2 2 2 2
ZnO 3 3 3 3
PTMQ 1.5 1.5 1.5 1.5
IPPD 1.5 1.5 1.5 1.5
Wax 2 2 2 2

Second cycle ingredients
CBS 2 1.6 0.8 0.4
Sulfur 0.5 1 2 2.5
Na-HMT -- -- -- --
CIMB -- -- -- --
BDBzTH -- -- -- --
Total 113.5 113.6 113.8 113.9

G* Modulus (kPa)
 23[degrees]C 445 477 553 531
 48 hrs. at -30[degrees]C 2,586 969 716 727
312 hrs. at -30[degrees]C 2,948 2,276
336 hrs. at -30[degrees]C 727 740
288 hrs. at -30[degrees]C
432 hrs. at -30[degrees]C 3,268 2,405

Percent change
 48 hrs. at -30[degrees]C 481 103 30 37
312 hrs. at -30[degrees]C 562 378
336 hrs. at -30[degrees]C 32
288 hrs. at -30[degrees]C
432 hrs. at -30[degrees]C 634

 ID: R1.2 R1.3 RI.4 R1.5

CV-60 100 100 100 100
N550 1 1 1 1
Stearic acid 2 2 2 2
ZnO 3 3 3 3
PTMQ 1.5 1.5 1.5 1.5
IPPD 1.5 1.5 1.5 1.5
Wax 2 2 2 2

Second cycle ingredients
CBS 2 2 2 2
Sulfur 0.5 0.5 0.5 0.5
Na-HMT -- -- 1 3
CIMB 1 3 -- --
BDBzTH -- -- -- --
Total 114.5 116.5 114.5 116.5

G* Modulus (kPa)
 23[degrees]C 442 457 459 451
 48 hrs. at -30[degrees]C 1,173 944 983 1,663
312 hrs. at -30[degrees]C
336 hrs. at -30[degrees]C
288 hrs. at -30[degrees]C 1,724 3,378
432 hrs. at -30[degrees]C 2,850 2,501

Percent change
 48 hrs. at -30[degrees]C 165 107 114 269
312 hrs. at -30[degrees]C
336 hrs. at -30[degrees]C
288 hrs. at -30[degrees]C 276 649
432 hrs. at -30[degrees]C 545 448

 ID: R1.7 R1.8

CV-60 100 100
N550 1 1
Stearic acid 2 2
ZnO 3 3
PTMQ 1.5 1.5
IPPD 1.5 1.5
Wax 2 2

Second cycle ingredients
CBS 2 2
Sulfur 0.5 0.5
Na-HMT -- --
CIMB -- --
BDBzTH 1 3
Total 114.5 116.5

G* Modulus (kPa)
 23[degrees]C 437 520
 48 hrs. at -30[degrees]C 839 739
312 hrs. at -30[degrees]C
336 hrs. at -30[degrees]C
288 hrs. at -30[degrees]C
432 hrs. at -30[degrees]C 2,454 1,268

Percent change
 48 hrs. at -30[degrees]C 92 42
312 hrs. at -30[degrees]C
336 hrs. at -30[degrees]C
288 hrs. at -30[degrees]C
432 hrs. at -30[degrees]C 462 144

Figure 5--particle size distribution NDR 47085--Lot
RC0426SDDD

Sieve size (mm)

%

% of total distribution Running total

 3.35 9.7
 2.35 18.2
 1.68 28.6
 1.19 41
 0.84 52.1
 0.59 64.6
 0.42 76.2
 0.30 85
 0.21 90.9
 0.15 94.8
 0.11 99.7
 0.08 99.4
 0.05 100

Note: Table made from bar graph.
COPYRIGHT 2003 Lippincott & Peto, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2003, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

 Reader Opinion

Title:

Comment:



 

Article Details
Printer friendly Cite/link Email Feedback
Author:Spanos, Pete
Publication:Rubber World
Date:Nov 1, 2003
Words:4190
Previous Article:Third generation metallocene EPDMs.
Next Article:High efficiency NR processing with good dynamic properties using a zinc free additive.


Related Articles
Fatigue endurance and viscoelastic hysteresis of short fiber/rubber composites.
New processing agent in tire compounds.
Vibration isolation characteristics, fatigue properties of chemically modified solution polymerized rubber blended with NR.
Understanding strain sensitivity effects in vibration isolators.
Compounding for maximum heat resistance and load bearing capacity in HNBR belts.
Predictive molding of elastomer aging effects on dynamic and static shear modulus.
Effect of a MFA on the processing and mechanical properties of a CB-filled NR compound.
High temperature curing and high heat resistance compounding.
The effects of DV on the morphology and rheology of TPVs and their nanocomposites.
Multifunctional acrylates as anti-reversion agents in sulfur cured systems.

Terms of use | Copyright © 2014 Farlex, Inc. | Feedback | For webmasters