Effect of Carbon Blacks in Synthetic Tire r Jompounds -F
sr
4
B. S. Garvey, Jr., and J. A. Freac, Jr. The 8. F. Goodrich Company, Akron, Ohio
*
en types of carbon black, represented by Ttwenty-four commercial and experimental products, are compared in the standardized American butadiene-styrene rubber. Each black is evalupted in six loadings varying from 90 to 75 P. H. k. (parts per hundred park rubber). Each compound is evaluated for processing characteristics, stressstrain, set, flexing, hot tear, heat brittleness, hysteresis, rebound, and hardness.
i COMPOUNDING synthetic rubber for tires, the carbon blacks play snoutstanding role,more important even than 1 III natural rubber. Important al%o is the choica of the propertypa and amannt of bkck. An a guide in making this cboica, a aeries of twenty-four black8 WBS investigated, Which fdin6 ten tgpes (Table I). They covw the range from fine color blacks thmugh c o m a thermal blaoks. Some of the sbaraderistice of the different typea are shown in Table I. Experimental Proeedun
For this work a Banbq-mixed blend of selected rubber was usad in the following baee recipe: P8nav.
1m.m 6.00 10.00 1.00
Bhk
Vdble
%!%%embk
* !P = p. esntoow
2.00
1.76
A msstar batch con&ting of the first five itema was mixed in a No. 11 Banburg mixer. The individual batches were mixed on a %inch mill with weoial care to~ureullifomlity. Eacilbatchaas &dated to give the mme volume of stock. selected materials wore used tbmugbout, and the mixing speoification wea ea follows:
a Use A. C. 9. Remrd m
Run3epu egst
lo. of at
@"A
Table 1.
Rop&iu of Black
Putids 6i.a
do m
w w faat enough to permit it to dmp thmugb onto and forth once eaah
. I
5.
perature build-up at end of 4€23(meth T used was a needts pymmster).
data giam tbe average Values for the +ma cum. In most wea the KBI~ not signi6osqt, but with the alowest curing bbdu tbe d n e for the 1Wminute cun m s lower tban the average. C O ~ ~ S B ISm O Nwa8 determined by the A. 8. T. M. procedure (I) at a wnstsnt dehction of 40 per cent on pellets inch in diameter and inch thick,cured 55 and 105 minutea at 280' F. The set after the 1Wminute cure
I
!% back
qr
batebing out. mteh weight and muin time for each bakh. niriute mniU+ld 14%) after aging pariod
Physical Propcltir S ~ ~ W S T Bmeesurementsweremade AXN by the A. 8.T.M. procedure (8) at a temperature of 82' F. and a humidity of 45 per cent. The c u m were 15, 30, 46, 75, and 160 minute at 280' F. Data mselected from the optimum cure for each black. DWOUFPEBH A R D ~ weB a meaeured S with a typ A sbore durometer on a 3 X 3 X inch sheet c u d 86 h t e s at 280" F. Rssowm WBS df&mmed ' by the Schapper d d (8) with a % arclon o a 3 X 3 X '/s inch Bpecimen cured 55 minute at 280' F. H w r m ~ m swea determined on the aoodrich Fkuometm (a) on peUets'/~o inch in diameter,cut from b l o b 1 X 2 x a inches, and cured 75 and 105 minutes at 280" F. The stroke was 17.5 per cent and the laad 143 paunda per square inoh. Testa were run at room tempwature (coId) and at 212O F.
~
4.
.".
t oolw.
11. Remrd minute
Placsmbhsrrmrsterbatohoooold mill (ice water on tull mth a) mill o d i c & at t i - inC L and ' b) mill & ture &-&all 1200 P.. 2. MdELlutea; aut *and forth twice aaoh way. a. Add half ?f black at faatcstrate sable t with O O O L Z 1.
.-
millto'/"inoh.
Ziamdemtor. 12R
1278
******
***
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
Vol. 34. No. 11
.-I I
I'C
33D5aM75 COLMI BACKS
W b E O AR€A SHOm UlNlMJU TENSILE VAWE OBTUND UNSHbCfDPR IbfKATES MAXIWM LNSlL VAWE OBTAINED
LINE THROUGH UNSHADED W GIVES THE AVERAGE W E
Lp
i'
CWNYEL BLACKS
3 75
EbSICWOCESSING CHANNELS
Figure 1. Cdrbon
Black Lodding vs. Tensile
-I -lW
W
20 . .. .. .. CCUUSE T H W A L BLACKS
203340506075 FNE T M W L BLACK
br:ARGE-PARTICLE lmORClN0 BACKS
Strength
i-
E
x
Figure 9. Carbon Black Loading vs. Per Cent Elongation WBB d d e r a b l y lower than that for the &minute cure. The dah selected are the average values for each group of blsclrs at both c u m .
&T BlUlTl5Nn88 w88 measured on epeoimma made by curing a Bandwich of the
tested (I/* inch) between two pliea of standa r d rubber t r e a d stock (*/IS inch each) 110 minutes at 280' P, This 1 X 6 X '12 inch spacimen w= cut i n t h e middle of one end to a depth of 1 inch and p u t in an oven at 212' F. for 3 hours. It WBB then removed and
immediately pulled in a Gooey machine at a rate of 1 inch per minute. Heat brittleness ia reportad BB the average porn& pull to separate the rhock for the first 1% inches.
Table II. Avuage V a l u a IOI &tsh Running Tempemtam on Remill and Tubing Index AT. Temp. on Remill. F. Av.TublngIndex
stock to be
Pvte b l d / l W p u t a r u b b m 1.
colo.bl,ok.
2. Aaetulene 3. channels 4. E ~ 6. l u g e - utlele IelnlOlOLn.
6.
ep.&fp...~r.i~m~
7. B O m i r e i n f O r ~
i: ~ ~ 10. Coueethamak
$
* Ternpaatwe not hksn.
20 30 HI 132 143 147 120 iao 130 136 137 143 120 n o ~la6 It0 1:s 1Z : *
~12.2 .
.
a
i$z
60
160 140 145 135 130 s It5 ' . P i t 4 12:
~
BO
75
170 146 140 1M) 159 146 160 ~ l t 7 It0 180
a
'13.0 .
a
B
12.8
20
80
40
ii-
12
12
8:
14
€4
is+ io
1113 io i i + ~ 12 1111 8 10 8 14 13 16 10 11.S 12.6 13 10.6 ii 1a.s 14 lo 11+ 8.6 10 10.5 8 8-
60 13 16 13+
ia+
I4 1s 14.6 1s 11+ 12
'
78
16 10 18
14 15
~
16
I4
;13.6 :+
N,-
1942
** *
******
INDUSTRIAL AND BNGINB'~RING CHEMISTRY
m-
" I
im
I yy\Du)B9R-
w w Mwuws -
LlyMED 8*R-M4xIw
FCR GRaJP L I N THu)LW UNSWC€D IUR-
\Iw
% i v%ub-
:
I=
I RlNFORClNG
Figure
3. Carbon Black Loading vs. 300 Per Cent Modulus
L wuaDe*R-wvu)
!I !
U N TWRUGU
1
IL Y
LOAOINO %HR.
T H E W BLACK
EW+WCESWG C " L S
Figure
4. Carbon Black Loading vs. Durometer Hardness
The data &ow the average values obtained for each type of black on an unaged specimen and on a specimen aged 14 dam in the Geer oven. HOT TZARwas determined on a grooved 5ex sheet I/, inch thick cured 60 minutes at 280- F. It was cut for */,inch in the groove and heated in an oven for 3 hours at 212O F. It wm them removed and immediately torn on a Cooey maohina. The tear resistance is the average pounds pull for the first inch. The data reported are the maximum, minimum, and average vdues for ench group. F u x RESISTANCE waa determined at 60" C. by a modification of the A. 8. T. M.grooved strip methcd (3). The Beaing machime used was a modified De Mattia type.
Processing Characteristics This Property is described elmhere (4). Essentially it is a direct evaluation of the extrudability of the rubber stock through a smaU die. M c m . The Goodrich plasticity (£ weight at 85" C. on the mixed batch) of the final mix is an indication of g w d extrusion properties. However, other properties of the mixed batch must also be considered dong with plasticity before msking predictions (4). MILLINQTIMTI. This is an indication of the m e of ine d mill corporation of the blaok into the stock. When k capacity is bslsnced against volume production, easy processing of the black become% an importgnt fator in selecting the one best black for a given urn (Figure10). ~ I N INDEX. Q
1280
******
I N D U S T R I A L A N D K N G I N E E R I N G CHEMISTRY
1LAUPBLACKS
1
***
Vol. 34, No, 11
1
i
k Figure 5.
Carbon Black Loading VI
"-
I '
I-
CCLMI SLACKS
Figure 6.
Schopper Rebound
I
Carbon Black Loading vr. Hysteresis at Room Temperature and a t
PIP' F.
~.
BATCH RUNNINQTEMEBR~TUEE ON REMIL& High milling temperatures can be very detrimental to extruding cbarwteristics of the mixed stock. From this standpoint blacks exhibiting low heat build-up are definitely desirable (Table 11). Discussion of Resulb
~T~~us-STBMN. Figure l sbows the maximum, and average values for tensile strength of the M e black for Merent loadings. Correspondingdata are elongation in Figure 2 and for modulus at 300 elongationin Figure 3. The ink blacks, acetylene h e 1 blacks are best for tensile strength. processing channel blacks are practically equiden standard The large-hticle reinforcing blacks
the special-proem reinforcing black do not impart quite gwd tensile strength. The semireinforcing b l a h sgain give somewhat lower values. The h e thermal black and lampblacks are next in line, and the thermsl blacks have very little reinforcing action. Figure 4, the dufrom theinkblacks lampblacks, howks than to the h e 88
Rebound increases with increasing gure 5). ALSO, the drop in rebound with is leas with the coarser blacks. Acetylene gber rebound thsn ita position in the series BOUND.
6
I
1
I
==
I---
e
l
Figure 7.
Carbon Black Loading vs. Compression Set
Figure 8.
Carbon Black Lodding vr. Heat Brittleness
E-SIS. Figure 6 shown that hsgteresis incfrom the came- to the hepertide black. There w~llltittle Werence in AT between the 7s and lO.%minutecum. COMEWMIM8mr. The avmage comprpsaion set values ara shown in Figure 7. The set is considerably lower at the tighter m. Acetylene black and the special-procwss blsck give nomewbat Lower valuea than the 0 t h . In general, the ditierencesarenotgreat. k T .-B F5gure 8 &ea the aver- values before and after && The stocks were more brittda after aging. In thin respect the ink blseks are best, fouowedby s t w h d chsnnel blaok, easr-pmcessing channel black, and large-patticle reinfoping black. The other blseks all gjve more brittb stocks. Em hae. In thia respect the color blecks are be&, ea
shown in Figure 9. The stgndsrd ohsnnel b l a h are better than the easy-pmcesSing ohanael bhdn, which are about the eameeathelarge-~clereinforcingblscks. Thelampblsolrs are good in the bigherloadings. The 0 t h give poor tear. ~ N Q With . regard to &a We, all of the compounds were poor and there wns not much m e m m between them. PRoQeSm0. The€achackm& ' 'CawerejudgedbymiUing time (Figure IO), pbstioity (Figure ll), he& build-up on ramill (Table II), and tubing clmwtem ' ties (Table 11). For hk 8 d dVSllb@ St W h step from ink blacL to standard channel black, to e-ssy-cbannebbkclqtoLsrge-psrtiolereinforcjngblack. Themfter blacLBarealleesierproceaSmg. A&ylmblackisoutstanding with regard to tubing properties, givbg a smooth, shiny surface, sharp cornera. and no @@.
e
Figure 9.
Carbon Black Loading vs. Hot Tear
1 50 6 0 75 ?C€ESS BLACK
I
x
JEM-E
I
Figure IO. Cdrbon Black Loddinivs. Milling Time
Combinations of
"be utility of any compound d e p d 8 on a combination of properties rather than on any single property. Table III d ~ o mtbe ohsracteristiee of compounds in group based on
the tensile strengtbn of the compound8. !lhm Proem. For maximum tensile strength and minimw heat brittleness only the ink and channel blacks can be considered. At somewhat lower tensile strengqh re&ementa, other blacb may be conaidered, although the channel blaoks still Iwk beat. The easy-proceesing channel blacks may have a slight advantage over the standard grades 88 indicated by the inclusion of both the 30 and 40 P. II. R. compound8 in Table IIIA. .
BODYSTOCKS. Heat reaktanm in body stooks in relatuv to tread stocks is more important and tensile strength and brittleness are leas important. If we uwiSe the compounds in the lowest tensile group, it seems best to use either fine thermal or epecial-pmcess reinforcing black b w they give the lowest hysteresis. With a minimum of loo0 pound8 pw~quareinchtenSilestrength,s~-~reinfor~ black, and semireinforcing blacks give the lowest h y s e . The m e is true with a minimum tensile s t d of 1500 pounds per square inch. At the impound level, carbon black gives only slightly higher hyntm48, which is coUnterbalance3 by better heat b r i t t l m At the 16OO-pod level, not only does the use of channel black give better heat brittlewa, but there is a leeway in tensile
N o v e m k , 1942
***
******
INDUSTRIAL AND ENGINEERING CHEMISTRY
1283
! i
3
1
“I
-BI!
t
my140 x) 60 15 FLNE THERMAL BLACK
Figure 11. Carbon Black Loading vr. Goodrich Plasticity
Table 111. Ropntln Baed 011 Minimum Tenrile sb.asUu TYRe of B h k
T d e Put./lOO 8-h Put. Rubber Lb./Sq. 1.; A. bXhimum T 10
1 laM) w
10
l1O0 1100 7.50 760
m m
80 80
’
ao
LamRblrOlu
4 of ?SO Lb. ~
a0
20
B. Minimum T
Bb Hwt Eot AT-E, ATC. bound. Britttem~.Lb. Tar. e F. F. % U W Aged Lb.
2
80
28 26
iaso
za 19 ai
8w
a
OW
18
€
sa
68
a
61
sa
61 48
M
47 66
49
61 67
14
7
00
60
ao 24
an
ao
21 21
30
€4
26
ai
40
C. Minimum Ten& of 16W Lb.
moo 1-
80 30 40
llW
40
lMm lMm
80
moo aim
ao
40 M)
w
76
6 2
17 6
w 61
w
7
22 S
66
40
7 8
6
9
63
54
69
40
14
17
4 3
28
80
6 14
69
a0
40
21
8 4
ao
a0
9
6
3.0
0.6 2.0 0.6 0.6
1.0 1.0 1.0
0.7
17M)
a8
60
63
sa
49
sa
BO
a
74 67
34
87
26
as
68 67
60
Sa
ia
9
8
4
4 8
3.0
0.6 2.0 0.6
3.0
48 49
ea
47 48
Bo
ss
67
4%
18 11
1.0
1.0 8.0
1.0
16
7.6
47
24
10 11’
13 13
7
2lW
2600 zaw moo
48 sa 32 44
76
48 40 MI
49
ze 7
8.0
a
24 8
39
7,s 6.0 6.6 6.6 0.6
11
s7
41
66 82
a4
44
68
91
81
u
16 8
14 10
78
ea
a4 8
61
38
89
UI
60
E u m r o o c r 0hUlE.d
60
w
aa660 2660
a m
67
ea 66 sa
W
108 08
w
which will permit slightly lower loading8 than a0 P. H. R. with consequent lower hysteresis. It a p pears, thedore, that even in body stocks, chsnnel black will give 88 good or better results than q d a l or furnace black& Mixturss of blscke would also be c o n s i d e d The decision mmn to be a “compounders’ choice”. Literature Cited 8. T.M.Strndsrda OD
(1) A.
48 a3
66
19 10 8 10
0
wr &I. In.
42 84
as
sa
14
B
B
ia
1,s
2.0 6.6 6.6
6,s
10.6
1
4.6 4.6
19
10.0
za
6.6
4
Minimum Tendle of 2wO Lb. wr Sq. In.
AwtyIme
Bt.ndud OhuUleI
66
4 of lo00 Lb. ~ ( Ea. s In.
80
E.
69
w
20
m
C0l.X
1
Bq. In
( s
40
40 87 a9
28
ia
34 32
IO
17
1.0
6.6
R u b b e r Produot. D38MOT, Method B
(1941).
(a) m., ~412-41(1941).
(3) m.. D43040 (WI). (4) Garvey. B. S., WhitIwt, M. E., and Freeae, J. A,,IND.ENO.CHIY.. 34,1308 (1942). (6) Laasis. E. T.. h. EnQ. Ca~u..ha.En.. 8,
682 (19a7). (6) Mermmler.
K., “Saiencn
of Rubber”. tr. b~ Mor& and Dunbrook, New York. Reinhold
Pub. corP..’l934.
(7) Wiegaod, W . B., .nd Ladd, W. A,, But& Age (N.Y.),50, 481
(1942).
