Compounding Pure Gum GR-S Stocks - Industrial & Engineering

January 1948

INDUSTRIAL A N D ENGINEERING CHEMISTRY CONCLUSIONS

Oxygen and water have a b g e synergistic effect in accelerating the degradation of tire-cord rayon at high temperatures. The conditions occurring in a tire are of considerable interest, since the rate of degradation of cord depends on the oxygen and water content during both the curing period and service life. ACKNOWLEDGMENT

The authors wish to acknowledge the valuable assistance of

B. E. Spain and H. R. Steigleder in obtaining the experimental data for this paper. LITERATURE CITED

(1) Charch, W.H., and Maney, D. B., U.S. Patent 2,128,229(1938). and Houston, M., Textile Research, 11, 4 (1940). (2) Fletcher, H., (3, Hatch, R. S., IND. ENQ.CHEY.,ANAL.ED., 16,104 (1944).

143

(4) Houtz, C.G.,and MoLean, D. A., J.Phys. Chem., 45,111(1941) (5) Ingersoll, H. G., J . Applied Phys., 17,924 (1946). (6) Knecht, E.,J. SOC.Dyers Colourists, 36,195 (1920). (7) Martin, A. R., Smith, L., Whistler, R. L., and Harris, M., J . Research Natl. Bur. Standards, 27,449 (1941). (8) Meyer, K, H., and Badenhuizen, N. P., Nature, 104,281 (1937). (9) Neale, S. M., and Stringfellow, W. A., Trans. Faraday SOC..33, 881 (1937). (10) Waller, R. C., and Roseveare, W. E., J . Applied Phys., 17, 487 (1946). (11) Weigerink, J. G.,Textile Reuearch, 10,357 (1940). (12) Zbid., 10,493 (1940). (13) Whitney, H.L.,and Jacobson, J. A., Exhibit 906, pp. 890037, Hearings before a Special Committee Investigating the National Defense Programs, U. S. Senate, 78th Congress, Part 21,Rayon 2lb. Cotton Cord for Tires, Government Printing Office, Washington, 1944. RECEIVEDDecember 24, 1946.

Compounding Pure Gum GR-S Stocks EFFECT OF INORGANIC OXEDES AND OXIDIZING AGENTS HARRY L. FISHER U . S . Industrial Chemicals, Inc., Stamford, Conn.

ARNOLD R. DAVIS .Imerican Cyanamid Company, Stamford, Conn.

pure gum GR-S stocks with only sulfur and inorganic oxides showed fairly good cures with magnesia, litharge, and lime with tensile strengths of 400-500 pounds per *quare inch and practically no cure with zinc oxide. However, in all cases the addition of inorganic oxidizing agents, red lead, lead dioxide, lead chromate, and ferric oxide acvelerated the cure and generally increased the tensile dtrengths. Also, the €urther addition of certain softening agents, especially Turgum, increased the tensile strengths considerably. Aging of these stocks, particularly those containing magnesia, generally showed a n additional incsrease in tensile strength without an undue lowering of the elongation.

P

URE gum types of compounds of synthetic rubbers are generally poor in their physical properties with the exceptioq of neoprene (polychloroprene), which gives excellent pure gum compounds. All the other vulcanizable synthetic rubbers must be compounded with carbon black to bring out t,heir full possibilities and make usable compounds. In the early part of the government’s synthetic rubber program screening tests indicated that pure gum compounding of GR-S gave vulcanizates with tensile strengths chiefly between only 200 and 300 pounds per square inch, and elongatiom to looo% and higher.

700

0’

c

COMP.

- (a) @) 500 -

600

NO.--

Although a few simple Donorganic-accelerated compounds with magnesia and litharge were better,’a rather complete study by the Research Compounding Branch, based on the use of zinc oxide. added stearic acid, eleven different accelerators, and varying proportions of sulfur (0.54.0parts) at different temperatures, brought out some compounds that had tensile strengths up to 700 pounds but in general confirmed the early results. The report concluded, ‘*None of the accelerator-sulfur levels developed compounds of any outstanding merit. Tensile strengths over 500 pounds are rare, and most of the results average 200 pounds per square inch.” Later a plan was started which was baaed on the idea that an oxidizing agent might give snappier cures of pure gum GR-S

1, 8, 15,28

2. 9.18.23

3.10,l7.24

4.11,18,25

POROUS SHEET NO CURE

W

Iw

100 -

200

2s 2s 2s IO ZnO 5 MqO 275 PbO EQUIMOLAR PARTS PER 100 PARTS OF GR-S

Figure 1.

2s 9 Ca (OH),

Effect of Oxides and a Hydroxide, and the Same Plus Oxidizing Agents, in GR-S Cured 60 Minutes at 292’ F.

Vol. 40, No. 1

INDUSTRIAL AND ENGINEERING CHEMISTRY

144

CONTAINING 100 PARTS GR-S, 2 PARTS SULFUR, AND TABLE I. ACTIONOF OXIDIZINGAGENTSIN FORMULA 10 PARTS ZINC OXIDE Compound No,

Oxidizing Agent, Parts

Cure, Min. a t

292' F.

Modulus a t 300%

Tensile Strength,

Lb./Sq. In.

Elongation, %

Set, %

Resilience, yo

"lore

Hardness30 sec.

0.5 sec.

UNAGED 1

None

30 60 90 120 180 240

Porous sheet Porous sheet Porous sheet Porous sheet Porous sheet Porous sheet

8

Pbs01 5

30 60 90 120 180 240

10 50 60 110 105

15

22

..

30 60 90 120 180 240

PbOz 5

50 315 480 460 390 340

1725 1425 1090 790 615 555

595 485 460 425 370 370

Tensile Modulus Strength, a t 300% Lb./Sq. In.

AGED24 HR. AT 212O F. No results h-o results No results No results No results No results

259 85 47 22 12 10

49 50 51 50 50 52

35 16 13 10 8 7

50 50 50 52 52 51

35 36 41 44 47 49

27 29 33 37 43 45 36 39 41 43 45 46

..

50 70 115 145 180 50 *.. ... ...

... I . .

No cure

PbCrO4 5

Elongation, %

150 480 430 465 430 400

1625 1040 765 625 510 470

350 65 70 110 120 170

760 150 100 70 50 45

N o results

TABLE 11. ACTIONOF OXIDIZINGAGENTSIN FORMULA CONTAINING 100 PARTS GR-S, 2 PARTS SULFUR, AND 5 PARTS MAGNESIGM OXIDE Compound No.


2

None

9

PbrOi 5

Cure, Min. a t

292O F. 30 60 90 120 180 240

a

Modulus a t 300%

...

55 90 130 125 155

Tensile Strength, Lb./Sq. In.

Elongation, 7 0

195 420 440 485 475 470

1090 915 705 650 580 575

71 42 24 20 15 13

50 50 54 52 51 50

39 42 45 47 49 49

28 ' 35 40 42 45 44

1025 865 780 700 630 585

57 35 28 21 17 15

51 52 52 52 54 53

41 42 46 47 48 50

30 60 90 120 180 240

::1 165 125

340 515 570 525 590 485

60 75

Modulus a t 300%


32 36 41 41 42 46

105 170 170 180 215 210

550 635 610 655 580 605

820 645 615 565 500 515

~ ~ ~ i l iShore Hardness Set, % ence, $lo 0.5 see. 30 see. IJNAGED -.. .. ~ _

Elongation, %

16

PbOz 5

30 60 90 120 180 240

115 200 175 170 210 145

535 520 440 500 455 380

845 610 545 560 505 530

32 16 12 11 11 13

49 50 51 52 02 51

44 46 49 49 49 50

36 41 44 45 45 45

95 165 175 220 235 175

525 445 400 490 415 370

790 520 470 470 425 465

23

PbCrOl 5

30 60 90 120 180 240

10 70 115 180 170 175

165 490 545 455 540 450

1350 900 735 580 570 505

112 47 30 18 17 14

51 50 51 48 52 54

39 42 46 48 49 50

29 34 39 41 43 45

55 150 170 230 230 230

465 560 630 580 635 540

LO85 655 610 505 520 460

TABLE111. ACTIONO F OXIDIZISG AGENTSI S FORMULA COKTAINING 100 PARTS GR-S, 2 P.4RTS SULFCR, AND 27.5 PARTS LITHARGE 292' F.

Modulus a t 300%


None

30 60 90 120 180 240

50 50 60 60 90 100

410 390 450 390 375 350

1040 850 735 715 620 540

48 25 20 18 13 11

48 50 51 50 53 52

PbaOi 5

30 60 90 120 180 240

40 60 60 70 90 95

450 620 560 530 500 400

1070 900 810 740 680 600

54 28 22 19 15 13

525 555 490 540 470 525

1090 870 820 790 655 650

50 30 25 22 16 15

Compound Oxidizing No. Agent, Parts

Cure, Min. a t

Elongation, %

ResiliSet, % ence, %

Shore Hardness 30 sec.

0.5 d o . .

UNAQED 3

10

17

PbOr 5

30 60 90 120 180 240

60 85 65 100 115 125

24

PbCrO4 5

30 60 90 120 180 240

55 65 65 105 110 125

.


Elongation, %

AQED24 HR. AT 21,Z0 F. 40 44 44 46 46 46

32 36 37 37 40 38

48 51 50 50 49 51

40 42 43 43 45 47

32 34 35 35 37 41

45 51 51 51 49 51

41 44 45 44 45 49

32 35 37 37 38 40

48 52 51 48 51 51

Modulus a t 300% 70 80 70 70 90 110

530 485 445 420 445 430

830' 730 680 665 650 605

90 100 120 115 120

545 570 500 530 490 500

845 750 730 680 650 630

60 105 100 105 110 115

600 575 540 520 500 435

995 815 810 750 690 645

75 100

570 505 470 470 480 475

900 725 730 680 680 625

110

90

44 46

110 115 110

I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY

January 1948

TABLEIV. Compound No.


ACTIONOF OXIDIZING AGENTSIN FORMULA CONTAINING 100 PARTS GR-S, 2 PARTS SULFUR,AND 9 PARTS CALCIUM HYDROXIDE Cure, Min. a t 292' F.

Modulub a t 300%


Elongation, 5%

Set, %

Res& ence, %

shore Hard% 0.5

880.

30 seo.

UNAQED 4

y

None

11

PbaOI 5

18

PbOa 5

25

PbCrOd 5

TABLEV. Compound No. 5

ri

30 60 90 120 240 30 60 90 120 180 240 30 60 90 120 180 240 30 60 90 120 180 240

50 70 85 90 95 135 40 75 105 110 120 130 105 125 12.5

135 145 130 25 55 60 95 110 125

345 490 445 475 380 400 270 535 560 515 520 430 555 620 570 605 620 560 90 345 440 470 470 505

1175 820 695 650 570 540 1075 925 810 705 660 580 875 790 720 745 750 730 1275 1125 970 740 640 620

68 30 19 16 12 10 70 39 29 22 18 15 36 29 25 25 25 22 115 68 46 26

18 15

51 50

51

53 53 53 49 51 52 51 51 50 51 51 52 50 51 50 45 48 49 51 53 52

41 45 45 47 48 49 40 43 45 46 48 50 44 45 45 46 46 47 36 40 45 45 48 50

30 37 40 42 45 45 32 34 39 41 43 44 37 38 41 40 41 42

*

29 32 37 40 43 44

Tensi1e Modulus Strength, Elongaa t 300% Lb./Sq. In. tion, % AQED24 HR.AT 212O F. 60 480 915 115 515 665 125 380 535 140 465 530 120 465 520 160 430 490 70 535 930 140 605 695 140 475 585 170 580 585 170 575 580 165 590 570 115 575 760 120 575 670 120 510 635 145 540 640 170 525 635 115 485 650 60 100 115 150 175 175

235 505 450 465 545 520

1140 845 680 575 555 530

+

COMPARISON OF THE EFFECT OF SOFTENERS WITH MgO Pb30cIN FORMULA CONTAINING 100 PARTS GR-S, 2 PARTS SULFUR,AND 10 PARTS MgO

Added Ingredients, Parts

Cure, Min. a t 292' F.

Pb304 0, softener 0

30 60 90 120 180 240 30 60 90 120 180 240 30 60 90 120 30 60 90 120 30 60 90 120 30

12

P b b 5, softener 0

64

PbaOi 5, Bartol 10

65

PbaOi 5, Paraflux 10

66

Pb304 5, pine tar 10

67

Pb304 5, Turgum 10

68

145

Pb304 5, Cumar M H 21/2 10

60

90 120 30 60 90 120

Modulus a t 300% 60


115 130 160 205 115 220 215 235 245 225 40 .. 50 110 125 55 100 120 125 35 70 95 115 25 60 95 120

435 495 545 500 485 590 600 815 745 785 750 750 440 _.. 480 420 440 600 530 545 585 410 730 605 640 190 610 835 900

105 115 135

710 670 755

90

Elongation, % ' Set, % UNAGED 905 49 725 31 670 24 620 21 555 19 570 17 895 45 28 675 625 22 600 19 565 18 18 580 995 41 20 730 605 16 585 14 1050 40 735 23 675 20 650 16 1350 70 975 33 790 24 740 20 1400 113 1250 72 1080 55 990 45 780 715 670

stocks with possibly higher tensile strengths than those ordinarily obtained, somewhat as i t does with natural rubber when the latter is cured with certain organic nonsulfur vulcanizing agents ( 2 ) . The oxidizing agents used were all inorganic, such as red lead, lead dioxide, lead chromate, zinc chromate, ferric oxide, and selenium. They were used in conjunction with inorganic bases, chiefly magnesia, zinc oxide, litharge, and calcium hydroxide, without an organic accelerator. The results showed that the original idea was not entirely correct, although i t was found that oxidizing agents sometimes give snhppier cures and always act as accelerators of vulcanization. Furthermore, it was found that the addition of certain softening agents, especially in the presence of magnesia, increased the tensile strengths considerably, and that aging of the stocks containing magnesia generally increased the tensile strength without lowering the elongation unduly.

30 25 22

~ ~ ~ i l iShoire Hardness ence, % 0.5 sec. 30 seo. 49 52 52 52 51 52 52 50 51 53 54 54 50 52 54 53 50 51 52 52 48 50 51 53 46 50 49 50

43 46 48 49 49 50 45 49 50 51 53 53 37 42 45 45 37 43 46 46 37 43 45 46 40 45 49 50

34 40 42 44 46 46 38 44 45 47 49 49 32 39 41 43 32 39 41 41 31 38 41 43 30 38 41 43

49 49 50

44 46 48

39 41 43

-

Tensi1e Strength, ElongaLb./Sq. In. tion, % AQED24 HR. AT 212O F. inn 4413 660 -._ 150 640 600 195 515 535 180 495 525 195 545 520 230 545 500 150 615 540 270 770 555 275 730 535 270 785 540 700 500 290 260 665 495 560 770 95 175 595 590 200 575 535 230 540 500 115 530 715 170 510 575 205 660 530 215 560 530 90 660 940 155 720 715 185 725 640 195 660 605 95 535 1240 160 935 915 180 I090 890 190 1105 840

Modulus a t 300%

___

175 205 225

770 705 790

630 580 580

DISCUSSION OF RESULTS

The effect of zinc oxide, magnesia, litharge, and calcium hydroxide, and of these same bases with the addition of inorganic oxidizing agents, is shown in Figure 1 and Tables I t o IV. By using 10 parts of magnesia the tensile strength rose to 495 pounds per square inch, and, with the addition of 5 parts of red lead, it became 715 pounds. (The actual figure for the 60-minute cure was 815 pounds, but for the 30-minute cure i t was 600 and the 90-minute cure, 745. Furthermore, the figures for the same stock but with 3 parts of sulfur were 675,665, and 645. Since 815 is obviously out of line, 715 is used for the comparison.) Ten parts of Turgum slowed the cure somewhat but in 90 minutes raised the tensile strength to 835 pounds per square inch. These data, the action of other softeners, litharge, and ferric oxide, and the effect of aging are shown in Figures 2,3,4, and 5, and Tables V t o VIII.


146

TABLEVI.

EFFECT OF TURQUM WITH MAGNESIA IN FORMULA CONTAINING 100 PARTS GR-S



Modulus a t 300%

102

hlgO 20, Turgum 0

30 60 90 120

165 185 220 260

720 790 845 965

103

MgO 20, Turgum 10

30 60 90 120

190 225 245 265

1190 1305 1416 1400

COMPARISON

O F THE

Conipound NO.

TABLEVII.


ElongaResilition, % Set, % ence. %


Modulus a t 300%


104

MgO 20, PbO 0. Turgum 10

105

MgO 10, P b O 5 , Turgum 10

30 60 90 120 30 60 90 120

270 345 365 430 105 205 265 300

1230 1155 1200 1510 680 1255 1110 1130

Parts

970 870 850 820

48 50 51 52

50 53 53 53

41 45 46 48

285 295 320 320

47 39 40 35

Elongation, %

ResiliSet, % enoe, %

UNAGED 735 595 580 570 1225 830 680 630

48 52 54 55 33 45

MgO 20, PbO 15, Turgum 10

30 60 90 120

165 255 305 330

870 1300 1510 1570

1090 845 755 730

64 44 40 37

49 51 53 55

1220 1285 1395 1625

TURGUM I N FORMULA

Modulus at 300%

Tensile Strength Lb./Sq. 1;.

Elongation,

51

54 56 58

46 52 55 56

610 750 880 880

1285 1130 1060 1145

450 375 335 350

45 51 54 55

39 46 50 51

325 440 495 510

1770 1880 1285 1520

800 640 535 550

49

-

735 710 695 730

AQED 48 HR. AT 212O F. 395 1730 620 515 1700 520 520 1315 460 600 1395 445 220 1345 835 355 1550 610 420 1400 530 435 1305 500

50

107

Figure 2.

30 see.

53 55 57 59 42 50 52 55

54 56 59 56

Three parts of sulfur gave approximately the same effects as 2 parts, and in most cases even 4 parts hardly showed an apprecisble increase in properties. Only a small amount of work was done with organic accelerators. They shortened the time of cure and increased the modulus and hardness, but showed no other appreciable effects on the physical properties.

Shore Hardness

49 54 55 55 50 53 53 53

26 22 17 17

PLUS

0 . 5 8ec.

35 30 26 29 64 30 21 18

600 490 420 430

lie)

Elonga tion, o/,

AGED 48 HR. AT 212O F. 245 715 580 265 725 550 310 695 515 300 860 570

1080 1165 1105 1265

Na-


38 43 44 46

350 480 595 600

3

Modulus

a t 300%

45 50 50 50

30 60 90 120

GOMR

2 PARTS SULFUR

53 53 54 53

MgO 20, P60 15, Turgum 0

2 SULFUR 10 Mg 0 5 Pb,O,

AND

UNAGED 280 43 705 30 675 28 670 25

106

"

Shore Hardness 0.5 sec. 30 see.

EFFECT O F LITHARGE WITH MAGNESIA AND MAGNESIA CONTAINING 100 PARTS GR-S A N D 4 PARTS SULFUR

Added Ingredients,

Compound NO.

Vol. 40, No. 1

Additional stearic acid showed no advantage, whereas the use of acetone-extracted GR-S, with magnesia and red lead, gave poorer results, as shown in Tables IX and X. The enhanced properties obtained with magnesia, an oxidizing agent, and a softening agent are not obtained to the same extent in Stacks containing carbon black (Tables XI. XII). Diuhenvl" guanidine (DPG) was added in two cases'to counteract the acidity of the Turgum. Interpretation of the results is- Bometimes difficult. 60 AND I20 MIN. CURES at 292'F. With increase in magnesia the 0 El effect of red lead and ferric o oxide is less marked, alAGED 24 WRS. at 212' though the accelerating 0 effect of the oxidizing agent is still noticeable; where@ the effect of Turgum is even 0 8 greater than with lesser amounts of magnesia. Litharge in place of red lead sometimes gave slightly higher tensile strengths, but red lead showed greater a& celerating value as indicated by higher modulus figures (compounds 86, 87 in Figure 5 and Table VIII, and compounds 106,107 in Figure 2 SULFUR 2 SULFUR 2 SULFUR 2 SULFUR 2 SULFUR 4 and Table VII). 10 MgO IO MgO 10 Mg 0 IO MgO 10 Mg 0 5 Pb,O, 5 Pb,O, 5 Pb,O+ 5 Pb,O, 5 Pb,O, The question might be IO BARDOL IO PARAFLUX IO PINETAR IO TURGUM IO CUMAR MH 2 t raised whether the higher (64) (651 (661 (67) I681 tensile strength depends upon any reinforcing action Effect of Softeners wi&h Magnesia Plus Red Lead in GR-S


January 1948

149

OF THE EFFECT 08 REDLEADAND FERRIC OXIDEWITH MAGNESIA AND MAGNESIA PLUS TURGUM TABLEVIII. COMPARISON IN FORMULA CONTAINING 100 PARTSGR-S, &PARTSSULFUR, AND 20 PARTS MgO

Compound No.


Cure, Min. at 292O F.

Modulus at 300%


Elongation, %

ResiliSet, % ence, %

Shore &rdness 30 sea.

0.5 8ec.

ACED48 HR. AT 212' F.

UNACED 940 920 1100 1300

515 415 395 410

24 20 20 23

56 57 58 59

54 59 61 62

51 56 58 59

690 890 1030

1140 1230 1110 970

390 350 310 270

60 30 90 120

160 310 390 435

745 1380 1460 1380

1045 685 650 600

56 46 45 40

49 49 50 51

46 53 59 61

38 48 54 56

300 500 620 720

1460 1550 1350 1380

800 580 470 440

FezOa 15, Turgum 0

30 60 90 120

310 405 465 480

975 1120 1115 1005

590 500 460 430

32 27 25 20

55 56 58 58

54 58 60 61

48 53 55 56

560 700 770 775

1320 1080 770 975

450 360 330 320

FesOs 15, Turgum 10

30 60 90 120

250 330 365 390

1508 1500 1380 1350

810 670 595 560

47 41 35 35

51 52 52 52

55 58 60 61

47 52 55 55

390 500 560 570

1880 1750 1470 1420

650 540 460 460

87

PbaOc 15, Turgum 10

114

115

TABLEIX.

NO,

Stearic Acid Added, Parts

92

93

ACTIONOF ADDEDSTEARIC ACIDIN FORMULA CONTAININQ 100 PARTSGR-S, 2 PARTSSULFUR, 10 PARTS MgO, AND 5 PARTSPbaOc Cure, Min. at

Tensile Strength, ElongaLb./Sq. In. tion, %

292' F

Modulua at 300%

0

30 60 90 120

130 175 210 220

615 785 775 690

910 715 660 585

2

30 60 90 120

125 165 205 215

590 685 700 785

950 730 660 155

shore Hardness 0.5 seo.

45 25 22 17

52 55 56 55

46 48 50 50

33 41 43 45

210 265 310 310

765 870 885 840

625 560 535 520

50 28 25 22

52 53 54 55

45 49 50 50

33 40 44 45

205 260 300 310

760 850 755 780

665 590 525 520

30

see.

13 -

El

14

12

/ '82

/

2 -I 8

9 ' a

BASE OR-S 100 S 2

a

5r 6 z 5

AOED COMR NO. @102--

3 4

z

e 3 0 i 3 IO3

T

MgO 20

-Mg 0 20,

TUROUM IO

I

0

I

1

I

L

30

60 TIME IN MINUTES at 2 9 2 O F .

90

120

Figure 3. Effect of Turgum with Magnesia in GR-S

at 300%

Elongation, %

AOED48 HR. AT 212' F.

103

8 9 a

Modulua


Resilience, 'pb

Set, %

UNACED

I1

Elongation, %

370 515 660 730

PbrOc 15, Turgum 0

I Ip 10

Tensile Btrength, Lb./Sq. In.

30 60 90 120

86

Compound

Modulus at 300%

of the magnesia. A eareful study of the effect of different volume loadings of magnesia in the GR-S stocks recorded here and elsewhere (6)shows that the reinforcing action of magnesia is only slight. Selenium with magnesia accelerated the cure and therefore acted like the oxidizing agents. The addition of Turgum caused an increme in tensile strength, but the over-all tensile strengths were lower than with red lead and ferric oxide (Tables X I I I , XIV). Vulcanization w i t h p - q u i n o n e d i o x i m e (GMF) and oxidizing agents gave low results. The products show low modulus and tensile strength, although they were well cured as indicated by the lower elongation and low set (Table XV). All the stocks showed good aging a t 24 and 48 hours a t 212' F. Those containing magnesia, and magnesia and Turgum, gained practically from 100 to 580 pounds per square inch after 48 hours. These results apparently depend in part a t least on the effect of oxygen, because longer times in the press at the higher curing temperature did not show similar increases and often showed decreases. The gains were especially noticeable with the stocks containing Turgum.


148

Vol. 40, No. 1

TABLE X. ACTION OF MAGNESIA AXD RED LEADON VULCANIZATION IN A FORMULA CONTAINING ACETONE-EXTRACTED GR-S 100, SULFUR 2, MgO 10, AND Pb3045 NO.

PBN" Added, Parts

62

0

Compound


Modulus at 300%


Elongation, %

115 150 195 120 155 190

495 605 655 425 550 660

685 630 570 620 640 600

60 90 120 63 1.5 60 90 120 a Phenyl-@-naphthylamine.

TABLE XI. Compound NO.

0


Cure, Min. a t 292'F.

Modulus Tensile Elongaat Strength, tion, 300% Lb./Sq. In. %

30 200 60 450 90 550 120 600 70 D P G 0 . 5 , Tur30 150 gum 10 60 300 90 400 120 550 71 D P G 0, Tur30 450 gum 0 60 1000 90 1250 1400 120 72 D P G 0 . 5 , Tur30 700 gum 0 60 1150 90 1450 120 1700 Diphenylguanidine, added to neutralize acidity of

TABLE XII. Compound NO.

88

89

90

91

51 53 52 53 51 51

42 42 44 41 41 42

34 36 37 32 35 36

Tensile Modulus Strength, Elongaa t 300% Lb./Sq. In. tion, % AGED 24 H R . A T 212' F. 230 610 555 210 590 515 275 595 475 195 580 550 260 710 530 270 595 480

EFFECT OF CARBON BLACKIN FORMULA CONTAINING GR-S 100, SULFUR 2, CARBON BLACK(EPC) 50, MgO 10, AND Pb3045

DPGG 0, Turgum 10

69

Shore Hardness 0.5 sec. 30 sec.

Resilience, %

Set, % UNAGED 29 24 16 24 21 20

550 1200 1450 1650 260 900 1350 1650 1100 2100 2450 2550 1350 2300 2600 2550 Turgum.

Resilience,

Set,

%

%

Cure, Min. a t 292'F.

Sulfur 4, MgO 10 PbaOa 5,' Cumar 0 Sulfur 2, ivgo 20, PhrOa 15, Cumar 0 Sulfur 4, MgO 20, PbrOa 15, Cumar 0 Sulfur 4, MgO 20, PbjOa 15, Cumar 10

30 60 90 120 30 60 90 120 30 60 90 120 30 BO

90 120

RIodulus Tensile Elongaat Strength, tion, 300% Lb./Sq. In. 70

71 75 80 80 65 61 76 77 65

70 74

75

65 71 73 57

725 1550 2100 2476 800 1350 1625 1900 1375 2450 , .

..

1000 1850 2325 2550

1550 2500 2650 2825 1550 2200 2425 2475 2350 2650 2550 2550 2300 2825 2875 2850

Resilience,

Set,

Yo

%

PARTS

Modulus Tensile at Strength 300% Lb./Sq. 1;.

... ... ... ...

56

0 288 0 234 0 225 0 218

0.271 0,224 0.200 0.200

AND

50 P.4RTS CARBOX BLACK (EPC) K , Tor-

sional Hysteresis

Modulus Tensile Elongaat Strength, tion, 300% L b /Sq. In. % AGED48 HR. AT 212O F 2025 2675 395 .. 2725 260 .. 2500 215 .. 2660 205 1975 2425 355 2375 2450 310 .. 2525 280 2325 265 2450 245 .. .. 2250 175 2276 150 .. .. 2375 150 2525 3000 340 .. 2750 250 .. 2550 230 .. 2650 220 ~

63 71 47 76 64 71 73 75 71 78 81 82 67 74 -77 78

55 66

io

72 57 65 68

io

65 74

0'201 0.179 0.166 0:233 0.227 0.227 0.175 0.173

io

o.'ii5 0.164 0.166

73 75

I

o:iso

77

79 61

Elongation, %

AGED48 HE.A T 212' F. 850 1500 605 1150 2050 555 1250 2160 530 1300 2200 510 600 1100 740 950 1700 615 1100 2050 535 1250 2150 555 1500 2160 425 2100 2550 360 2250 1500 335 2400 2500 315 1600 2250 440 2200 2550 350 2350 2550 325 ... 2500 295

0:527 0,463 0.469

60 64 53 61 65 65 54 62 66 66

GR-S

K,

teresis

54 63 65 67 45


UNAGED .~~ 42 39 38 40 30 40 27 39 40 37 35 38 30 39 25 39 47 39 34 40 22 39 18 39 62 34 51 34 38 35 32 35

520 430 350 335 495 440 400 366 440 315 260 245 535 405 355 330

Tor;i;-al

0.5 sec. 30 sec.

UNAGED 106 30 78 30 31 71 70 31 126 31 89 30 71 30 65 31 42 38 40 39 35 39 30 40 33 38 33 39 30 41 22 41

740 685 655 650 775 790 705 670 565 615 480 455 510 485 460 400

EFFECT OF CARBON BLACKI N FORMULA CONTAINING 100


Shore Hardness

~

~

~~

~~

.

OF SELEKIUM AS OXIDIZISG AGENTWITH MAGNESI.+ IN FORMULA CONTAINIKG GR-S 100, SULFUR 2, TABLEXIII. EFFECT

AND Compound No.


Cure, llin. a t 292O F.

120

Selenium 2, Turgum 0

15 30 GO 90 120 15 30 60 90 120 15 30 60 90 120 15 30 60 90 120

121


122


123


hIodulus a t 300% 130 215 230 325 300 115 165 215 275 275 150 190 255 320 305 105

165 220 270 245

Tensile Strength, Lb./Sq. In. 450 540 535 470 560 570 890 790 680 740 470 600 620 490 535 495 780 805 700

700

h f g o 10

Elongation, 70 Set, % 850 615 525 395 450 1080 880 680 560 580 835 650 540 410 430 1155 880 730 ,580

605

UNAGED 40 20 14 9 10 50 29 18 15 14 40 20 15 11

..

60 31 21 16 15

Resilience,

%

50 54 56


51 53 54 55 56 50 54 58 59

43 47 50 52 53 45 48 50 51 52 44 47 50 51

58

52

51 33 24 J7

45 48 50 52 52

60 60

56

31

40 45 47 49 32 40 45 46 49 32 40 45 48 49 32 39 45 47 4')

Tensile Nodulus Strength, a t 300% Lb./Sq. In.

Elongation, %

AGED48 HR. A T 212' F. 215 475 505 320 590 445 375 615 375 ... 5 10 280 465 505 310 215 875 710 280 825 590 340 825 505 395 710 440 385 735 455 235 545 540 305 515 430 380 575 390 475 305 435 505 300 505 210

280 34.5 400

395

88,i

760

850

595 520 475 460

800 825 805

I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY

January 1948

149

Although ferric oxide and red lead were similar in their activity, ferric oxide has two desirable qualities over red lead. It is nontoxic, and prevents stocks containing Turgum and not more than 10 parts of magnesia from sticking t o the mill. PURE GUM

e

/

PbO Is, TLJRGUM IO

l07---

3

I

0

30

60

120

SO

TIME IN MINUTES at 292.E

Figure 4. Effect of Litharge with Magnesia and Magnesia Plus Turgum i n GR-S

l5

t

?-- x/

EXPERIMENTAL CONDITIONS

-->E

MgO

The GR-S used was the standard blend No. 45 which had been prepared and set aside for general testing purposes. More recent GR-S is much improved over the early blend used, and it and other synthetic rubbers will probably give better results with the type of compounding described than those reported in this Paper. Standard compounding materials were used throughout. The magnesia was extra-light calcined. These standard materials were from bulk lots set aside for comparative work in the program of the Office of Rubber Director. Milling conditions were as follows: batch size, 300 grams GR-S; 6 X 12 inch laboratory mill; initial mill temperature, 35” C., cooling water on. Completed batches were conditioned 16 hours and remilled for 4 minutes at

20

ADED COMF! NO. Q

86-

0 07--

Pb,O,

0 114-----

FepO, 15

x 115

0

30

Pb, 0,

--

I

60

15

15, TLJRGUM IO

35O

Fe,O, 15, TUROUM IO

90

I

I20

TIME I N MINUTES ot 292OF.

Figure 5.

There may be a question as to whether some of these stocks could be considered pure gum. A pure gum mixture has been defined as consisting “essentially of rubber plds only the ingredients required t o vulcanize it and protect it against deterioration” (4). The maximum proportions of these necessary ingredients are given as 3.5 parts of sulfur, 1.5 parts of accelerator, 10 parts of metallic oxide (usually zinc oxide), 2 parts of organic acid (usually stearic acid), and 1.5 parts of antioxidant. A stock with the upper limiting amounts of these ingredients would have a volume loading of 7.6 t o 100 volumes of rubber. Ten volumes or even slightly more are usually considered as being within the. pure gum range. Of the stocks in the series, No. 12 (Table V) containing 2 of sulfur, 10 of magnesia, and 5 of red lead has a volume loading of only 4.3, and No. 102 (Table VI) with 4 of sulfur and 20 of magnesia has a volume loading of 7.6, the same as the first example. No. 115 (Table VIII) with 4 of sulfur, 20 of magnesia, 15 of ferric oxide, and 10 of Turgum has a n inorganic volume loading of 10.3 to 100 volumes of rubber, and could be included as a pure gum stock. This type of compounding should be of use in many places where pure gum stocks are required, and probably also in carcass and other stocks where carbon blacks are not needed or desired.

Effect of Red Lead and Ferric Oxide with Magnesia and Magnesia Plus Turgum in GR-S

c.

All cures were made between zinc sheets in a mold a t 292’ I?., and all testing was done a t 78’ F. and 50% relative humidity. Determined were: modulus at 300% elongation and tensile strength a t break in pounds per square inch; elongation in per cent; set in per cent; resilience a t room temperature by Bashore (1) resiliometer (falling weight) ; torsional hysteresis, K at 280’ F. ( 3 ) ; hardness at 0.5 and 30 seconds


150

TABLEXIV.

EFFECTOF SELENIUM AS OXIDIZINGAGENTWITH MAGNESIA I N FORMULA CONTAINING GR-S 100, SULFUR4, AND TURGUhl


Cure, Min. a t

292O F.

Modulus a t 300%

I24

Selenium 2, MgO 10

121,

Selenium 1. Mg 10

15 30 60 90 120 15 30 60 90 120 15 30 60 90 120 15 30 60 90 120

115 205 325 410 435 120 170 265 345 395 175 270 375 460 485 115 240 360 395 440

Compound

No.


Elongation, yo Set,

10 Resili-.

Shore

yo ence, 70 0.5 sec. 30 see.

126

Selenium 2, h l g 0 20

I27

Selenium 1, MgO 20

Compound

No.

Added Ingredients. Par@

96

GMF-2,

87

GMF 3

PbCrO4 20

ZnOt’5, 98

G M F 3, MgOn 5

99

VULCANIZATION O F

GMF2 PbaO; 20

Cure, Min. at

540 1020 745 710 538 190 810 830 670 795 880 1370 1190 990 875 825 1300 1300 1015 1010

Modulus

at 300%

Tensile Strength, Lb./Bq. In.

Elongation, %

AGED48 HR.AT 212O F.

USAGED

TABLE XV.

Vol. 40, No. 1

1025 800 490 415 360 1005 810 590 475 450 95: 760 545 450 410 1010 795 590 500 480

46 28 14 12 10 45 27 16 13 14 47 36 25 21

..

49 35 26 21 20

49 52 58 60 60 48 52 56 58 59 47 54 57 55 56 49 53 55 66 56

46 50 56 60 61

47 50 55 57 60 50 54 60 61 64 50 54 57 61 62

35 41 53 56 56 35 41 50 53 55 38 49 55 56 59 37 47 52 55 56

310 435 720

565 825 750 750 715 840 760 830 760 865 1365 1220 1015 1005 915 1295 1410 1105 1135 1085

.. 280 370 520 650 800 365 530 815 1000

..

355 490 705 780 845

495 460 300 265 255 610 480 400 330 330 625 475 340 305 290 640 520 390 370 340

GR-S WITH NONSULFUR VULCANIZINGAGENT, p-QUINONEDIOXIME (GMF), P L U S OXIDIZ1h.G AGENTSI N 100 PARTS GR-S

292’ F.

Modulus a t 300%

30 60 90 120 30 60 90 120 30 60 90 120 30 60 90 120

105 120 130 130 160 180 18p 170 75 90 105 105 150 155 155 155

Tensile Strength, * Lb./Sq. In.

UXAGED 255 235 200 215 260 230 250 245 200 240 265 230 255 230 240 240

Elongation, %

575 495 440 450 460 380 390 395 860 780 715 650 455 420 425 415

by Shore durometer type -4.Tensile strips were aged in air in a n oven at 212’ F. chiefly for 48 hours; some were aged for 2.1 hoiirs. ACKNOWLEDGMENT

The authors are grateful to Ralph A. Naylor of American Cyanamid Company for supervising the mising and curing of the stocks. This investigation was carried out under the sponsorship of the Office of Rubber Director in connection with the Government, Synthetic Rubber Program.

Set, %

10 6 5 5 6 4 4 4 35 24 14 9 7 9 7

Resilience, %

46 47 47 46 53 55 54 64 52 53 51 53 54 52 52 54

Shore 0.5 sec. 30 eec.

40 44 45 45 46 48 45 47 38 40 40 4% 45 45 45 45

33 35 35 35 40 42 40 40 27 30 35 35 38 38 38 37

Modulus a t 300%


AQED48 165 165 165 170 250 260 250 260 110 130 145 160 155 155 160 160

Elongation, %

HR.AT 212’ F. 200 210 200 190 285 240 250 260 215 220 230 225 205 185 210 215

325 360 340 335 340 29(! 300 310 670 555 500 450 385 375 395 370

LITERATURE CITED

(1) Bashore, H., H. India Rubber World, 95, No. 6, 37-8, 51 (1937). (2) Fisher, H. L., IND. ENG.CHEN.,31, 1381-9 (1939). (3) Mooney, M. and Gerke, R. H., India Rubber W o r l d , 103,No. 4. 29-32 (1941) : Rubber Chem. Tech., 14, 35-44 (1941). (41 Russell, W. F., in Davis and Blake’s “Chemistry and Technology of Rubber,” p. 752, New York, Reinhold Pub. Corp., 1937. ( 5 ) Vanderbilt -50.. R . T., New York, lab. rept., BookIet 8, p. 1% (Jan. 1.5, 1945). RECEIVED September 30, 1946. Presented before the Division of Rubber Chemistry at the llOth Meeting of +,he A~~~~~~~ cHEMICAL s ~ Chicago, Ill.

~

Compounding Pure Gum GR-S Stocks - Industrial & Engineering

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