INDUSTRIAL AND ENGINEERING CHEMISTRY
124
occur with this reagent.
The thiocyanogen values are the lowest
of all; on the basis of values obtained by the other methods as well as of experimental evidence not included in this paper, these
values are believed to result from incomplete reaction. As a class the iodine monochloride methods give considerably higher values than those obtained with the other reagents. This may be attributed to the substitution reaction that readily occurs with that reagent. The effect is perhaps most marked in the data obtained for polyisobutylene sample 2 with 0.1 N Wijs reagent; the upper value (0.4) is far greater than can be explained on the basis of the known molecular weight of this polymer (6) and the corresponding terminal double bond contribution. Furthermore, since this polymer sample was fractionated in such a way as to remove all species of viscosity-average molecular weight less than about 50,000, the high value cannot be ascribed t o the presence of dimera, trimers, or other small molecules formed during polymerization. In view of the data and the above considerations, i t is believed that the unsaturation values based on ozone degradation are correct, within the limits of experimental error, and that this reagent makes possible a relatively good estimation of the number of double bonds in polymers such as have been described. A modified procedure more suitable for rapid evaluations is the object of a current investigation. ACKNOWLEDGMENT
The writer is indebted ts Joseph Holowchak for developing the semimicro-Kjeldahl procedure used in many of the analyses, to Mrs. M. Robbins for securing much of the experimental data,
Vol. 36, No. 2
and to P. J. Flory for cooperation in deriving the molecular weight relations. LITERATURE CITED
(1) Bamberger, Ber., 35, 1606 (1902). (2) Biieseken and Gelber, Rec. trav. chim., 46, 158 (1927); 48, 377 (1929). (3) Bruni and Geiger, Atti. accad. Lincei, 151 11, 823 (1927); Rubber Chem. Tech., 1, 177 (1928). (4) Faragher, Gruse, and Garner, IND.ENG.CHEM.,13, 1044 (1921). (5) Flory, J. A m . Chern. SOC.,65, 372 (1943). ( 6 ) Gilman, “Organic Chemistry”, Vol. 1, p. 548, New York, John Wiley Sons, 1938. (7) Gorgas, Kautschuk, 4 , 253 (1928). (8) Kaufmann and Gartner, Ber., 57, 928 (1924). (9) Xemp, IND.ENQ.CHEM.,19, 531 (1927). (10) Kemp and Mueller, IND. ENG.CHEM.,ANAL.ED., 6, 52 (1934). (11) Kolthoff and Stenger, “Volumetric Analysis”, Vol. 1 , p. 230, New York. Interscience Pub.. 1942. (12) Pummerer and Gundel, Be?., 61, 1591 (1928); Rubber Chem. Tech., 2, 373 (1929). (13) Pummerer and Mann, Ibid., 62, 2636 (1929). (14) Pummerer and Stark, Ibid., 64,825 (1931). (15) Rehner, IND.ENG.CHEM.,36, 46 (1944). (16) Sbderback, Ann., 419, 217 (1919). (17) Thomas, Lightbown, Sparks, Frolich, and Murphree, IND. ENG.CKEM.,32, 1283 (1940). (18) Thomas and Sparks, iiustralian Patent 112,875 (1941). (19) Thomas, Sparks, Frolich, Otto, and Mueller-Cunradi, J . Am. Chem. Soe., 62, 276 (1940). (20) Weygand, “Organisch-Chemische Experimentierkunst”, p. 125, Leipzig, Barth, 1938. PRESENTED before the fall meeting of the DiviBion of Rubber Chemistry AarBRIcaN CHEMICALSOCIETY, in New York, x, Y . , 1943.
EFFECT OF BANBU Y MIXING I. DROGIN, H. W. GROTE,
AND
F. W. DlLLlNGHAM
United Carbon Company, Inc., Charleston,
W.
Va.
tempera obtained with mixing chamber from the bottom for approximately ”8 inch and read from a direct-reading potentiometer. Dumped stock temperatures were taken with a Cambridge needle pyrometer. The following Banbury conditions prevailed in the general study of the blacks in the various rubbers: The batch weight was 1200 grams for smoked sheet, GR-S, Buna N, and Butyl stocks with a corresponding specific gravity of 1.12, 1.14, 1.19, and 1.19, respectively; 1530 grams for Neoprene GN stock (1.41 specific gravity); and 1660 grams for the Thiolcol FA stock (1.52 specific gravity). The rotor speeds were 115 r.p.m. for the front rotor and 102 r.p.m. for the back rotor, or a ratio of 1.127. The pressure of the circulating water was 15 pounds per square inch and the temperature, 85’ F. The mixing cycle was 15 minutes. The black loading was 50 parts by weight on 100 of rubber. Table I describes the thirteen blacks investigated. They include four channel process blacks, seven furnace blacks made by combustion, and two furnace blacks made by thermal decomposition. Among the combustion-type blacks are included
The behavior of thirteen types of blacks during Banbury mixing is investigated in smoked sheet and in five synthetic rubbers: GR-S, Buna N (GN), Butyl (GR-I), Neoprene GN (GR-M), and Thiokol FA (GR-P). The distinction among the different blacks in physical and chemical characteristics, processing, and reinforcement is also evidenced in the power Consumption and temperature rise in a Banbury during mixing in the rubbers. The relation varies with the type of rubber] the widest range appears for Neoprene GN and the smallest for Butyl. The difference between blacks is more pronounced in GR-S than in smoked sheet. A m o n g the measurable characteristics of a black, that of surface area shows the closest relation to the power consumed and the temperature developed.
HE equipment used in this study was a laboratory size Banbury B, with a capacity of 1359 grams at 1.25 specific gravity with a/,k-inch radial peripheral clearance between the working tips of the rotors and the adjacent bore of the mixing chamber sides. The ram was operated with an air pressure of 100 pounds per square inch. The Banbury mixer v a s driven with a 7.5-horsepower direct-current motor. The rotors could be varied in speed by controlling the voltage through the motor. The power consumption was obtained from a General Electric dial-type, two-wire, d.c. watt-hour meter with 10-watt graduations having a capacity of 15 amperes a t 230-240 volts, The
T
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
February, 1944
125
T O T A L POWER-WATTS --18 IO
u)
75
-
I998
!i
7
K
w
z . n
45 I8 11
15
SRF BLACK IN OR-S
P
%e SI
---SOFTENER
A T 4 MIN.
Figure
5
MINUTES Figure 1.
IO
2.
Effect of Black Loading
15
Effect of Time of Adding Softener in
GR-S Stocks acetylene black, lampblack, and Philblack. The latter is made from oil and natural gas. BANBURY CONDITIONS
CHARACTERISTICS OF BLACKS TABLEI. PHYSICAL Color& Area (Nigrom- Sq. M:/ eter) 0. Channel Process Blacks 281 68 CC Conducting (Voltex) HPC Hard-processing (Kosmobile-5, 105 83 Dixiedensed-S) MPC Medium-processing (Kosmobile, 94 Dixiedensed) 87 EPC Easy-processin (Kosmobile 77. so 90 Dixiedensed $7)
%
D.P.G. Adporptlon
Volatile Matter, %
pH
49.0
5.01
5.9
14.3
5.02
4.2
11.4
4.30
4.5
10.8
5.70
4.5
Furnaoe Process Blacks 95
75 84 45 39
10.6 5.4 1.7 1.3
1.30 1.30 0.50 0.80
9.5 6.2 9.3 8.6
Semireinforcing Kosmos 20, Dixie 20) 103 Semire/nforcjng iKosmos 25, Dixie 25) 106 100 Semireinforcing (Lampblack)
29 25 23
3.0 1.0 2.1
0.70 1.30 4.80
9.1 9.4 5.7
105 Fine thermal (P-33) Medium thermal (Thermax) 116 The lower the figure, the darker the black.
23 19
0.4 0.2
0.50 0.20
7.9 6.8
8RF SRF SRF FT MT a
SPEEDON BEHAVIOR OF BLACKS IN GR-S TABLE 11. EFFECTOF BANBURY Semireinforcing Furnace Black Channel Black 70 85 100 115 130 70 85 100 115 130 2446 1155 1290 1526 1770 2150 1285 1470 1670 2080 327 228 237 255 267 290 262 278 291 311 331 227 230 247 256 280 230 251 273 295 27.5 20.1 24.1 25.4 25.9 26.9 14.6 17.6 21.9 26.3 7.73 4.33 4.68 5.14 6.25 7.03 3.06 3.70 4.66 6.77 -. Easy-Processing
Rotorspeed,r.p.m. Power, watts Max. temp., O F. Dump temp., O F. Tuber,grams/min. Dillon, inch/sec.
.
Modulus at 2007 Tensile Ib./sq. i l . Elongalion, % Hardness, Shore Tear resistance, lb./sq. in. Rebound % Heat buiid-up, O F.
-Cured 60 Min. at 280° 995 1010 1010 1020 2425 2480 2490 2440 365 370 365 345 64 64 63 63 467 39 217
454 38 216
442 38 214
391 39 212
F . 7 -Cured 45 Min. at 280" 1165 860 910 875 900 2560 1900 2050 1970 2050 330 330 355 340 345 58 57 57 56 56 382 39 209
205 54 174
210 55 175
208 54 173
216 54 175
F.910 2030 335 56 212 54 181
WATERTEMPERATURE IN A BANBURY TABLE111. EFFECTOF CIRCULATING ON BEHAVIOR OF BLACKS IN GR-S Water temp., F. Power, watts Max. temp., T. Dump temp., F. Tuber, grams/min. Dillon, inch/sec. Modulusat 200% Tensile, lb./s Elon ation gin* Hardrness hhore Tear resihnce, lb./sq. in. Rebound % Heat build-up, F.
Easy-Processing Channel Bl& 60 80 100 120 1995 1960 I900 1930 310 294 307 314 298 283 274 300 25.1 23.4 26.3 26.7 5.77 5.09 5.95 6.27 -Cured 1025 2620 350 63 412 39 216
60 Min. at 280' F.1000 1010 1125 2575 2500 2525 345 325 330 63 63 63 333 37 215
308 37 215
304 39 213
Semireinforcing Furnace Black 60 80 100 120 1973 1700 1655 1645 242 252 266 270 230 236 242 256 26.1 25.3 24.8 24.8 7.33 7.10 7.44 7.44 -Cured 825 1550 315 54 127 47 185
45 Min. at 2809 F.800 775 770 1600 1700 1630 325 350 345 54 54 53 127 47 185
131 46 185
138 47 185
SPEED. The study first centered on the effect of Banbury speed. Fifty parts, respectively, of an easy-processing channel black and a semireinforcing furnace black on 100 parts of rubber were studied in GR-S with the Banbury rotor speeds varied from 70 to 130 r.p.m. a t a constant mixing cycle of 15 minutes. The results are shown in Table 11. Increased rotor speed leads to greater power consumption, higher stock temperatures, and faster extrusion. There is practically no effect on the physical characteristics of the stocks. TEMPERATURE OF CIRCULATING WATER. The same blacks were studied in GR-S a t circulating water temperatures varying from 60" to 120" F. and a t constant rotor speeds with a 15-minute cycle. The results are shown in Table 111. Increasing the temperature of the circulating water decreases the power consumption. This is particularly noticeable in case of the semireinforcing furnace black. The physical characteristics of the stocks are unaffected. SOFTENER ADDITION TIME. The effect of adding the softener before or after the incorporation of the pigments was also investigated with an easy-processing channel black in GR-S a t 50 parts loading. Less power is consumed, and the temperature remains lower when the softener is added before the pigments. Thus, the power consumption is 1810 watts and the maximum temperature 265" F. when the softener is added before the pigments (Figure 1); whereas the power consumption is 1998 watts and the maximum temperature 284' F. when the softener is added after t h e pigments. The physical characteristics of the stocks are practically unaffected. BLACKLOADING.The effect of increased black loadings was studied with an easy-processing channel black and a semireinforcing furnace black in smoked sheet and GR-S. The mixes were maintained a t constant volume. According to Table 1V and Figure 2, approximately 15% more power is required to incorporate 50 parts of easy-processing channel black into GR-S
126
INDUSTRIAL AND ENGINEERING CHEMISTRY SRF HMF IT
EPC
MPC
Vol. 36, No. 2
LL:
HPC
EASY-PROCE SSING CHANNEL BLACK
"E
5 iILi
e IO(
a W 2 w
m
t-
I-
€n I-
30C
!i
5
31 I
I80( [L
SS
GN
w
SEMI-REINFORCING FURNACE BLACK
2 50
$
a
GR-P GR-M GR-S GR-I
w
c
0
a
P I -0 -.
1500 19 2 9 45 80 94 105 SURFACE AREA,SQUARE METERS PER GRAM
4. Comparison
of the Behavior of Two Blacks in Six Rubbers
Figure
Figure 3. Relation of Power Consumption and Temperature to Surface A r e a of Blacks
loadings. The stock temperatures rise as the black loading is increased. Easy-processing channel black produces higher temperatures in GR-S than in smoked sheet, whereas semireinforcing furnace black appears to work somewhat cooler in GR-S than in smoked sheet. In the case of smoked sheet, increased loadings of easy-processing channel black and semireinforcing furnace black stiffen the stock and reduce the tubing rate; OF INCREASED BLACKLOADING IN SMOKED SHEETA N D GR-S TABLE IV. EFFECT in the case of GR-S, increased loadings of Semireinforcing Furnace Black, Easy-Processing Channel Black, these blacks improve the tubing rate. Parts Part6 30 35 40 45 50 30 40 50 60 70 R E L I ~ B I L I T Y O F RESULTS. To establish Rubber the closeness with which the Banbury rePow=r, watts SS 1847 1880 1870 1840 1858 1695 1705 1685 1700 1710 GR-s 1915 2028 2060 2105 2115 1740 1760 1750 1765 1740 sults could be checked in GR-S, four conMax. temp., ' F. SS 247 258 260 266 273 242 254 256 265 276 secutive mixes of easy-processing channel GR-S 256 270 278 282 290 232 242 245 256 266 3 8 . 3 38.2 36.4 3 6 . 0 3 2 . 6 4 0 . 8 4 0 . 3 3 9 . 8 39.2 3 8 . 8 black at 50 parts loading were tested. The Tubrr,gramu/min. SS GR-S 1 6 . 8 1 8 . 1 2 0 . 2 2 2 . 1 2 3 . 0 2 1 . 7 2 3 . 5 2 7 . 0 29.2 32.2 ss 5 . 2 3 4.66 4 . 3 7 4 . 3 3 3.94 5.60 5 . 4 5 5 . 0 8 5.04 5.00 power consumption values were 2010, 1990, Dillon, inch/sec. GR-S 3 . 3 7 3 . 5 0 3 . 6 3 3 . 8 7 4.08 4 . 9 6 5 . 3 5 5 . 5 3 6.20 6 . 8 0 2040, and 2060 watts, respectively. The -O , pm it um Cure at 280' F. maximum temperatures ranged from 208" to 1 1250 1465 1610 1840 800 1200 1475 1825 2200 309" F. than into smoked sheet, on the other hand, only 4% mom power is needed to incorporate 50 parts of semireinforcing furnace black into GR-S. There appears to be little difference in the power consumption between t,he different
uI.-u
Tear resistance, lb./sq. in. Rebound, % Heatbuild-up,
SS
GR-S
ss F.
GR-S SS GR-S
1032 279 56 46 135 210
1250 314 55 46 140 215
910 4480 2550 600 525 64 50
1100 1250 4350 4325 2670 2850 540 550 510 445 69 71 52 56
1389 334 52 44 144 220
1490 492
TABLE V.
Power, watts Max. temp., F. D u m p temp., F. Tuber, grams/min. Dillon. inch/sec.
CC S'oltex 2220 290 269
22.1
3.46
00
42 148 224
1530 532 48 41 151
242
585 3970 1200 670 470 54 42
900 3925 .1700 595 465 59 48
746 1108 130 175 62 67 52 52 118 126 159 167
1460 1910 3400 3410 3200 1900 2060 2060 510 500 450 320 295 365 68 72 64 56 61 65 960 838 910 188 214 225 55 59 57 51 48 46 150 131 141 176 180 172
RESULTS FOR THIRTEEN TYPESOF
HPC 3IPC EPC Kosmo- Iiosmo- Kosmobile 77 bile S bile 2115 2170 2140 290 302 295 268 275 270 22.8 21.8 22.4 4.44 3.92 4.40
CF Kosmos 97 1955 273 269 24.9 5.44
c
Modulus a t 300% Tensile, !b./sq. in. Elongation, 70 Hardness, Shore Tear resistance, lb./sq. i n . Rebound, R Heat build-up, F. Electrical reaistsnoe, megohmcm.
1825 3125 415 69 480 36 212 0.0008
BLACK IN
B E H A V I O R OF BLACKS IN RUBBERS
GR-S. The results on thirteen types of black in GR-S are shown in Table V. The power consumptiondiffersfortheseblacks. Assigning
an arbitrary rating of 100 t o hard-processing
GR-S STOCKS"
HMF HMF HMF AcetyKosmos Phillene 40 black 1975 1765 1780 307 261 271 297 245 270 37.6 25.3 33.4 9.83 9.15 5.56 Optimum Cure a t 280' F.
1500 3000 455 63 527 39 224
1575 3000 450 63 487 38 214
1600 2800 435 62 477 42 210
1800 2700 400 61 243 47 184
2150 2420 335 67 358 45 201
1050 2470 350 59 206 49 175
1475 2600 325 64 209 49 177
..
..
426
0.0355
0,0002
782
..
SRF SRF SRF Kosmos Kosmos Lamp25 black 20 1750 1680 1755 238 258 247 235 253 240 24.3 23.0 28.5 5.73 5.31 6.87 830 1985
370 58 179 51 170
11.40
FT P-33 1775 235 235 20.0 4.49
60
40
175
183
500 800 475 49 129 47 175
..
..
..
725 1780 390 56 185
Recipe: GR-S 100, Bsrdol 2.5, Cireo oil 2.5, cinc oxide 5, Santooure 1.25, sulfur 2, carbon black 50; press cure, 280D F.
1075 1580
465 GO
212
>IT l'hrrmax 1835 219 210 19.7 5.10
-
270 000 535 40
..
IGO
48 106
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1944
SHEETSTOCKS~ TABLE VI. RESULTSFOR NINE TYPESOF BLACKIN SMOKED
Power, watts Max. temp., F. D u m p temp., O F. Tuber, grams/min. Dillon. inch/sec.
lb./sq. in. Rebound % Heat buiit-up,
O
F.
HPC EPC HMF Kosmo- Kosmo- Acetybile d bile77 lene 1935 1840 1870 347 265 270 344 260 267 30.8 29.5 31.7 5.81 3.58 2.79
HMF Philblack 1800 304 300 35.2 4.01
HMF SRF SRF Kosmos Lamp- Kosmos 40 black 20 1685 1755 1830 250 266 277 271 250 265 38.1 36.1 39.2 4.76 3.98 5.02
FT MT P-33 Thermax 1605 1700 260 220 249 220 43.3 42 0 5.67 3.96
65
2250 3500 440 69
Optimum Cure a t 280' F.1440 2200 1175 1675 3500 3620 3050 3800 545 530 455 570 62 66 61 62
570 3600 660 55
400 3110 710 48
1530 47 152
I148 52 156
1065 58 138
955 62 129
565 65 120
529 67 135
1600 4475 600 61
1570 4325
1540 46 160
m ..n .
1243 60 136
570 60 140
a Recipe: smoked sheet 100, atearic acid 4, zinc oxide 5, antioxidant 1, Captax 0.75, sulfur 2.85, carbon black 50; press e w e , 280' F.
TTPESOF BLACKIN BUTYLAND BUNAN STOCKS TABLE VII. RESULTSOF SEVERAL
Power, watts Max. temp., F. Dump temp., F. Tuber, grams/min. Dillon, inch/aec. Modulus a t 300% Tensile, lb./sq. in. Elengation, % Hardneas, Shore Tear resistance, lb./sq. in. Rebound, % Heat build-up, F.
Butyl StocksQ EPC H M F H M F SRF Kosmo- PhilKosKoabile 77 black mos 40 moa20 1605 1613 1635 1695 248 234 285 250 247 240 253 290 19.6 20.4 13.5 25.0 1.67 1.63 1.01 2.01 -0Dtimum 510 1000 3000 2050 760 575 54 58 570 10 242
397 12 200
FT
P-33 1553 225 232 16.0 1.85
MT
.------Buns N StocksbE P C H M F SRF
Thermax 1534 217 217 17.1 2.42
Kosmobile 77 2498 304 295 25 3 1.77
262 12 184
171 13 186
MT Therrnax 2125 278 269 18 2 2.33
-Optimum Cure a t 280. F.2450 2675 2200 725 3340 3015 2825 1200 365 325 360 440 67 65 63 52
Cure a t 312O F.------700 560 275 100 2240 2040 2200 2480 660 680 725 820 52 47 35 56 365 12 194
Kos- Kosmos moa 40 29 2309 2284 307 301 297 295 24.4 22.9 1.28 1.60
84 17 218
334 36 211
297 44 200
250 47 193
113 49 174
a Recipe: Butyl 100, stearic acid 3, zinc oxide 5, Tuads 1, Captax 0.50, sulfur 2, carbon black 50; pre88 cure, 312' F. b Recipe: Perbunan 100, Bardol 2.5, Circo oil 2.5, zinc oxide 5, Santocure 1.25, sulfur 2, carbon black 50; press cure, 280' F.
TABLEVIII.
RESULTS FOR SEVERAL TYPES OF BLACK IN KEOPRENE GN THIOKOL F A STOCKS
Neo rene G N Stocks" MT 'HPC E P C %MF H M F SRF Koa- Kosmor TherKoamo- Kosmo- Phil20 bile43 bile 77 black mor! 40 max 2150 2060 1790 1760 1525 Pswer, watts 2270 290 249 236 227 803 296 Max. temp., ",F. 285 245 232 225 298 290 D u m p temp., F. 49.0 51.9 45.8 30.1 Tuber, prams/min. 11.1 31.7 5.72 0.77 4.46 6.05 5.62 Dillon, inoh/sec. 0.37 Modulus a t 300% Temile, lb./sq. in. Elongation % Hardness, Ahore. Tear resistance, Ib./sq. in. Rebound % H e a t buiid-up, F.
Cure a t 287' F -. 2450 30i5 2800 290 330 73 70
-Optimum 3230 2915 2950 3712 a50 410 78 76
2985 250 77
548 39 189
396 45 183
554 39 190
412 47 176
450 50 167
600 2450 890 52 492 55 192
'
AND
--Thiokol F A StooksbEPC H M F SRF MT Kosmo- Kos- Kosmos Therbile 77 mos 40 20 max 2310 2205 2065 1730 322 303 280 224 311 308 290 224 32.6 47.3 48.4 49.8 0.67 4.08 4.64 6.11 -Optimum Cure at 298O F.1000 1500 1000 400 1200 1500 1320 500 370 300 450 365 67 76 70 52 393 386 546 119 27 39 40 45 Compression set too high for testing
Recipe: Neoprene G N 100, sqearia.acid 0.50, aocelerator 552, 0.10. carbon black 50, Neoaone A 2, light-calcined magnesia 4 Circo oil 5 , zina oxide 5. press cure 287' F. b Recipe: Thiokol FA '100, stearic acid 1, zinc &de 10, Alt& 0.35, diphenyl guanidine 0.10, carbon black 50; press cure, 298' F. (1
channel black, some of the other types of black rate as follows: easy-processing channel, 97.5; high-modulus furnace, 87.6; semireinforcing furnace, 83.0; and medium thermal decomposition, 81.2. The range between the extreme types is 20 points, equivalent to a difference of 380 watts. The maximum temperatures for these blacks range from 302" for the hard-processing to 219" F. for the medium thermal decomposition black. SMOKED SHEET. The results of nine types of black in smoked sheet are shown in Table VI. Assigning an arbitrary rating of 100 to the power consumption of hard-processing channel black, some of the other blacks rate as follows: easy-processing channel, 98.4; high-modulus furnace, 94.0; semireinforcing
TABLE
Ix.
Rubber
furnace, 90.1; lampblack, 97.9; fine thermal decomposition, 90.1; and medium thermal decomposition, 85.8. The range between the extreme types is only 13 points, equivalent to a difference of 265 watts. The maximum stock temperatures for these blacks range from 304" for the high-modulus furnace (Philblack), 270" for hardprocessing channel, 250" for semireinforcing furnace, to 220" F. for medium thermal decomposition black. BUTYLAND BUNAN. The results of several types of black in Butyl and Buna N stocks are shown in Table VII. For Butyl, assigning an arbitrary rating of 100 to the power consumption of easy-processing channel black, there is a difference of only 6 points, equivalent t o 100 watts, between it and medium thermal decomposition black. The easyprocessing channel black attained a maximum stock temperature of 250' and the medium thermal decomposition black, 217" F. For Buna N, assigning a n arbitrary value of 100 to the power consumption of easy-processing channel black, the extreme type (medium thermal decomposition) shows a rating of 85.1, equivalent to a difference of 373 watts. The maximum stock temperatures for these two blacks were 304" and 278" F. NEOPRENEGN AND THIOKOLFA. The results of several types of black in Neoprene GN and Thiokol FA stocks are shown in Table VIII. For the former, assigning an arbitrary value of 100 to the power consumption of hard-processing channel black, the extreme type (medium thermal decomposition black) shows a rating of 67.0, equivalent to a difference of 745 watts. The maximum stock temperatures for these two blacks were 303' and 227" F. For Thiokol FA, assigning an arbitrary value of 100 t o the power consumption of easy-processing channel black, the extreme type (medium thermal decomposition black) is 75.0, equivalent to a difference of 580 watts. The maximum temperatures for these two blacks were 322' and 224' F., respectively.
OF
Two
OF
BLAiCK IN surRUBBERS
Easy-Processing Channel Semireinforcing Furnace Black Black Max. Tubing Max. Tubing Power, Rat- temp., rate, Power, Rat- temp., rate watts ing F. g./min. watts ing F. g./mih.
Smoked sheet
1840
Neoprene G N GR-S Butyl
2485 2310 2150 2115 1636
$;;tkZFA
127
135 125 117 115 89
265
31
1685
304 322 296 290 260
25 3 32 31.7 21 8 13 5
2066 2284 1760 1750 1605
122 136
105 104 95
250
38,
301 280 236 247 234
22.9 48,4 45.8
24.3 19.6
128
INDUSTRIAL AND ENGINEERING CHdMISTRY POWER CONSUMPTION AND TEMPERATURE
SURFACE AREA. The relation of power consumption and temperature to the surface area of black in GR-5 is shown in Figure 3. An increase in surface area is accompanied by a corresponding increase in power consumption and temperature development. CHANNELAND FURNACE BLACKS. Figure 4 and Table IX compare the behavior of easy-processing channel and semireinforcing furnace blacks in six rubbers. Assigning an arbitrary value of 100 to the power consumption of easy-processing channel black in smoked sheet, the corresponding ratings in
the synthetics will be as high as 135 for Buna N and as low as 89 for Butyl. Similarly, assigning a n arbitrary rating of 100 for the power consumption of semireinforcing furnace black in smoked sheet, corresponding ratings in the synthetics range from 136 for Buna N to 95 for Butyl. ACKNOWLEDGMENT
The authors wish to express their appreciation to the United Carbon Company’s laboratory personne1 for assistance in assembling the rubber test data and to s. W. Nourse for preparing the charts.
THE ROLE OF CAR ON BLACK SURFACE CflEMISYWY The presence of surface oxygen on the carbon black particle appears to increase the secondary coherence forces between Butyl polymer molecules. I n an uncured state, the result i s an increase in the bound polymer per volume of carbon pigment or a decrease in the solubility of Butyl-carbon black mixtures. In the vulcanized state, the increase i n bound Butyl, due to carbon black surface oxygen, is reflected i n superior tear resistance and minimum hysteresis losses for a given pigment size. The advantages of superior tear resistance and minimum hysteresis losses are most apparent in Butyl polymers of higher chemical unsaturation as exemplified by Butyl B-3. With polymers of lower chemical unsaturation such as Butyl B-1.5, the relatively l o w states of cure minimize the reinforcing actions of the oxidized pigment surfaces. Improving tear resistance of a Butyl 8-3 polymer by decreasing the state of cure results i n impairment of hysteresis properties. Therefore reinforcement of tear resistance i n combination with higher states of cure becomes more dependent upon pigment surfaces as the chemical unsaturation of the polymer i s increased. From the standpoint of practical compounding, the large-particle carbon with a surface pH of 4 i s slightly superior to a finer-particle carbon with n o surface oxidation in the reinforcing of tear resistance of a Butyl B-3 polymer. This slightly superior tear resistance, over the cure range, i s obtained i n conjunction with the superior over-all hysteresis properties of larger-particle pigment.
H E N pigments or fillers are incorporated in a vehicle, three properties of the pigment that may affect the overall properties of the mixture are particle size, particle shape, and chemical nature of the particle surface. For all carbon blacks i t is generally assumed that the particle shape is spherical ( I ) , so that the colloidal properties of carbon black may be reduced to two variables. The effects of carbon black properties on the reinforcement of natural rubber are well known from the recent discussions by Wiegand (9),Fielding (a),and many other investigators. Drogin (9) and Turner et al. (8) have shown how the properties of the general types of carbon blacks specifically affect Butyl rubber vulcanizates; Haworth and Baldwin (6) described the effect of Butyl rubber unsaturation on some carbon black compounds. The purpose of the present work was to isolate the role of the surface chemistry of carbon pigments on the reinforcement of Butyl polymers. The reinforcing action of a pigment surface is attributed to the increase in the secondary coherence forces between the polymer molecules. Thus, according to Houwink ( 6 ) ,
Vol. 36, No. 2
R. L. ZAPP, Esso Laborat Standard Oil Development C Elizabeth, N. tlizabeth, PI. J.
14, ?
-
t
\+&
-
active tillers as well as the action of cooli bring rubber into a physical state akin to that of vulcanization. Any conclusions about pigment reinforcement must of nccessity take into consideration the state of cure of the compJund and the effect of pigmentation upon the state of cure. In this paper the state of cure will be indicated by moduli at 300% elongation. Results are shown with a polymer of relatively low chemical unsaturation designated as Butyl B-1.5 and with a polymer of higher unsaturation designated as Butyl B-3. (Butyl B-3 was one of the products made during the development of the Butyl rubber process. Although not strictly representative of the currently manufactured Butyl known as GR-I, it is sufficientIy close to that product in physical properties to allow the observations, reported for Butyl B-3, to become applicable to GR-I.) Butyl R-3 is capable of yielding higher states of cure, presumably as a result of the ability of the increased unsaturation to give more sulfur cross linkages. I n studying the variations of physical properties with respect to the surface chemistry of carbon pigments, special attention has been given to tear resistance and hysteresis combinations and, more specifically, to the maintenance of good tear resistance over long curing times in combination with good hysteresis. These subjects are important factors in the consideration of synthetics for pneumatic tire construction. CARBON BLACK SURFACE CONSIDERATIONS
For a given carbon black, the most important surface property, the one that largely governs its adsorptive capacities, is the amount of chemically combined oxygen on the particle surfare. If a carbon particle has a high degree of combined oxygen on the surface, it possesses a high volatile content, a low or acidic pH in a water slurry and a high absorptive capacity especially for alkaline materials (IO). On the other hand, a carbon black with little or no combined oxygen on the surface has a volatile content measured in tenths per cent, a high p H in a water slurry, and a lowered adsorptive capacity. According to these adsorption concepts an oxidized surface could be considered an active carbon while the unoxidized surface could be considered inactive. Accordingly, such a range or a series of degrees of surface oxidation was studied in
