ASTM D15-72. Methods of Compound and Sample Preparation for Physical Testing of Rubber Products

~ ~l~ Designation: D 15 - 12 American National Standard J 1.1
American National Standards Institute

Standard Methods of

COMPOUND AND SAMPLE PREPARATION FOR
PHYSICAL TESTING OF RUBBER PRODUCTS1

This Standard is issued under the fixed designation D 15; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year
of last reapproval.

These methods have been approved by the Department of Defense to replace methods 101 I and I iII of Federal Test Method
Standard No. 601 and for listing in the DoD Index Specifications and Standards. Future proposed revisions should be co-
ordinated with the Federal Government through the Army Materials and Mechanics Research Center, Watertown, Mass.
02172.

1. Scope Sections

1.1 These methods specify standard ma- Preparation of Standard Vulcanized Sheets 7 to 10
terials, describe equipment, and prescribe from Mixed Batches of Rubber Com-
processing methods for evaluating compound- pounds II to 15
ing materials in various types of polymers,
carbon blacks in natural rubber, and for eval- Preparation of Pieces from Rub- 16 to 24
uating butadiene (BR) and styrene - butadi- ber Vulcanizates Other than Standard
ene (SBR) polymers. Test Sheet 17
18 and 19
1.2 The methods are divided into three Part B Evaluation of Standard and Non-
parts and appear in the following sequence: standard Materials and of Commercially 20
Available Rubbers 21
Part A-- Preparation of Rubber Compound Sections 22

Standard Materials, Equipment, and Proc- Natural Rubber 23
essmg 2 to 15 Styrene Butadiene Rubbers
2 to 6 Neoprene Rubber 24
Butyl Rubber 25 to 30
Nitrile Rubber
Solution Polybutadiene Rubber

Polyisoprene Rubber
Part C Evaluation of Carbon Blacks in Na-

tural Rubber

PART A-PREPARATIO:--; OF RcBBER Co:vtPoc:--;o

Standard Materials, Equipment, composition given in subsequent parts of the
and Processing methods are as follows, and may be materials
that are known to have properties identical
2. Scope with those of NBS standards, as supplied by
the National Bureau of Standards. However,
2.1 These methods provide a listing of the in case of dispute, actual standard material
reference compounding materials required to from the Bureau of Standards shall be used.
formulate the compositions given in subse-
quent parts of this method, give the proce- Material NBS Standard
dures covering the weighing of the materials, Sample No.
describe a standard two-roll mill and certain Natural rubber
of the operations concerned with mixing, and Styrene butadiene rubber, Type 1500 385
describe an internal mixer and methods of op- Butyl rubber 386
eration. These procedures may be used to Styrene-butadiene rubber (Type 1503) 388
evaluate nonstandard materials where appli- Nitrile-butadiene rubber 389
cable; the evaluation of nonstandard SBR (33 percent acrylonitrile approx.) 391

polymers and carbon blacks are referred to in
Parts B and C, respectively. Zinc oxide 370

3. Standard Materials 1 These methods are under the jurisdiction of ASTM
Committee D-11 on Rubber and Rubber-Like Materials.
3.1 The standard materials required for the This standard is the direct responsibility" of Subcommittee
D-11.20 on Compounding Materials and Procedures.

Current edition approved April 10, 1972. Published
May 1972. Originally published as D 15 - 15. Last previous
edition D 15 - 71.

1

D 15

NBS Standard measured. The lead strips shall be inserted,

Material Sample No. one at each end of the rolls approximately

Sulfur 371 2.5 em (I in.) from the guide, while a piece of
Stearic acid
Benzothiazyl disulfide 372 compounded rubber, with Mooney viscosity in
Tetramethyl thiuram disulfide 373
Channel black (EPC type) 374 excess of 50 M L I +4, 100 C (212 F), approxi-
Magnesium oxide 375
Phenyl beta naphthylamine 376 mately 75 by 75 by 6 mm (3 by 3 by 0.25 in.)
·Oil furnace black (HAF type) 377
Conducting black (CF type) 378 in dimension, is passing through the center
Calcium carbonate (precipitated) 379

Calcium silicate 380 porton of the rolls. The rolls shall be at the
Gas furnace black (SRF type) 381
Mercaptobenzothiazole 382 temperature specified for mixing. After pas-
383
N-rert-butyl-2-benzothiazole-sulfenamide sing through the rolls, the thickness of the
384
lead strip shall be measured with an accurate

micrometer or thickness gage. Tolerances

on openings between the mill rolls shall be

4. Compounding Procedures ±0.15 mm (±0.006 in.) for openings 0.6

4.1 The standard laboratory mill batch size mm (0.025 in.) or more, and ±0.05 mm
in grams shall be based on four times the rec-
ipe weight for all compounds unless other- (±0.002 in.) for smaller openings.
wise specified. For the internal mixer, the
batch size in grams shall be equal to the 5.3 The compounds shall be mixed with
nominal mixer capacity in cubic centimeters
multiplied by the spt:cific gravity of the com- the rubber banded on the slow roll, unless
pound.
otherwise specified, and the temperature at
4.2 All materials shall be weighed accu-
rately to witl:tin I percent of the weight speci- the middle of the surfaces of the rolls shall be
fied.
measured during the mixing procedure suf-
4.3 The carbon black shall be conditioned
before weighing and mixing by heating in a ficiently frequently to maintain the desired
Type I B oven, as described in ASTM Speci-

fication E 145, for Gravity-Convection and temperature (Note 1). Whenever % cuts
rum:d- Ventilation Laboratory Ovens2 for 1 h
at 125 ± 3 C. The black shall be placed in an are specified, the batch shall be cut three
open vessel of suitable dimensions so that the
depth of black is no more than I em (0.4 in.) fourths of the distance across the roll and held
during condftioning. The black conditioned
as above shall be stored in a closed moisture- until the bank just disappears (Note 2). When
proof container until ready for mixing.
cuts each way are specified, successive 3
5. Mill Mixing ; 4

5.1 Mixing shall be accomplished on a lab- cuts shall be made from alternate directions
oratory mill having rolls between 150 and 155
mm (5.9 and 6.1 in.) in outside diameter, allowing 20 s between each cut, unless other~
with a working distance between the guide at
the nip of 25 to 28 em (10 to II in.). The speed wise specified.
.of the slow roll shall be 24 ± 0.5 rpm, and the
gear ratio shall be I to 1.4. The mill shall have NoTE 1-The batch may be removed momen-
facilities for maintaining the rolls at the speci- tarily from the mill to measure the surface temper-
fied temperature within the tolerances given. ature on the front roll.

5.2 The clearance between mill rolls shall NoTE 2_-Donot cut any batch while free pig-
be determined by means of two lead strips 10 ment ts evtdent tn the bank or on the milling sur-
± 3 mm (0.4 ± 0.1 in.) in width, at least 50 face.
mm (2 in.) long and 0.25 to 0.50 mm (0.01 to
0.02 in.) thicker than the roll clearance to be 5.4 The weight of the mixed batch shall not
differ from the total weight of all the mate-
rial by more than ± 1.0 percent.

5.5 The mixed batch shall be cooled to

room temperature on a flat clean metal sur-
face.

6. Internal Mixer Mixing

6.1 Internal mixing shall be accomplished
in a laboratory internal mixer3 having a nom-

; 1974 Annual Book of ASTM Standards, Part 41.
An internal mixer, Type B Banbury, manufactured by

the Farrell Corp., Ansonia, Conn., has been found satis-
factory for this purpose.

2

ina! capacity of 1170 ± 40 cm3 with a slow D 15
rotor speed of 77 rpm and a gear ratio of I to
1.125. mm (0.085 in.) in thickness and the stock shall
be sheeted from the rolls.
6.2 The batch size should be the volume of
the internal mixer measured in cubic centi- 8.3 After mixing or remilling, the sheeted
meters (or milliliters) multiplied by the spe- stock shall be placed on a flat clean metal sur-
cific gravity. face and slabs shall be cut at least 3 mm (0.12
in.) less in width and length than the corre-
NoTE 3-lf an old or worn internal mixer is used, sponding dimensions of the mold cavity. Di-
the batch weight should be increased accordingly. rection of the grain of the rubber shall be
marked on each slab. Slabs of uncured com-
Preparation of Standard Vulcanized pounds shall be within ±3 g of the weight
Sheets from Mixed Batches of given in Table 2 when cured in the mold de-

Rubber Compounds scribed in 9.2.

7. Scope 9. Apparatus

7.1 This method applies to the preparation 9.1 Press- The press shall be capable of
of standard vulcanized sheets from mixed exerting a pressure of not less than 3450 kPa
batches of rubber compounds. The mixed (500 psi) on the cavity areas of the mold dur-
stocks may be prepared in a laboratory by the ing the entire period of vulcanization, and
procedures outlined in Sections 2 to 6 of these shall have heated platens of sufficient size so
methods, or they may be factory-mixed that no portion of the rubber will be nearer
stocks, or they may come from any stage in than 75 mm (3 in.) from the edge of the plat-
processing before vulcanization. This method ens during vulcanization. The platen shall
describes the standard press, mold, prepara- preferably be made of rolled steel bored for
tion of stock, and procedure for curing sheets. steam heating. Either a self-bleeding trap or
a small vent shall be placed in the exit steam
8. Preparation of Stock line to allow steam to flow continuously
through the platens. If chamber-type platens
8.1 Compounds described in Parts B and are used, the steam outlet shall be placed
C shall be conditioned at a temperature of slightly below the steam chamber so that good
drainage is assured. The conduction of heat
23 ± 5 C (73.4 ± 9 F), preferably in a closed from the hot platens to the press crosshead
shall be reduced as much as practicable by
container to prevent absorption of moisture means of a steel grid between them, or by
from· the air. The period of conditioning shall other means. The pressing surfaces of the
be as specified in Table I. Where remilling of platen shall be plane parallel to within 0.24
the stocks is required, this shall be done by mmjm (0.003 in./ft) when the platens are at
passing the stock without banding and with 150 C (302 F) and closed under full pressure,
rolling and passing it endwise ten times through with a grid of soft solder or lead wire between
the rolls of the mill described in 5.1 at the them.
same temperature used for mixing and with

a clearance between the rolls of 0.20 mm 9.2 Mold- The mold shall have cavity sec-
(0.008 in.). Then, after adjusting the clearance tions similar in dimensions to that shown in
between rolls to 1.4 mm (0.055 in.), the stock Fig. I, which gives sheets approximately 150
by 150 by 2 mm (6 by 6 by 0.08 in.). The cav-
shall be banded on the slow roll, three "1. ities to within 6 mm (0.25 in.) of the edges
shall be between 1.9 and 2.0 mm (0.075 and
cuts shall be made each way, and the stock 0.078 in.) deep. The corners of the cavities
shall be sheeted from the mill to give a sheet may be rounded with a radius not greater
after cooling approximately 2.2 mm (0.085 in.) than 6 mm (0.25 in.). An alternative type of
in thickness. test slab mold made by the cutoff bar method
with a lower plate thickness of 19 mm (0.75
8.2 Compounds mixed in the factory shall in.) is shown in Fig. 2. The molding surfaces
shall be clean, highly polished, and hard chro-
be conditioned at 23 ± 5 C (73.4 ± 9 F) for mium plated. The cover of the mold shall be

a minimum of I h. The stock shall then be
remilled for 5 ± 2 min on the mill described in
5.1 at a temperature appropriate for the par-
ticular compound. The mill shall be adjusted
to give a sheet after cooling approximately 2.2

3

0 15

a flat plate at least I em (0.4 in.) in thickness pared in accordance with Part 8 at a tempera-
and preferably hinged to the cavity section to ture of 23 ± 5 C (73.4 ± 9 F) and for the times
minimize scratching of the mold ·surfaces. In- shown in Table I. Test vulcanizates of com-
stead of a separate mold and cover, the cav- pounds mixed in the factory between 24 h and
ities may be cut directly into the platen of the 60 days after vulcanization.

press. Unless required, a mold lubricant shall
not be used on the mold surfaces. When a Preparation of Pieces from Rubber
mold lubricant is required, only a residual- Vulcanizates Other than Standard
type lubricant which does not affect the cured
slab should be used, and the excess lubricant Test Sheets
should be removed by curing and discarding
at least one set of sheets. A silicone-type lubri- 11. Scope
cant ~r a mild soap solution have been found
satisfactory. 11.1 This method applies to the preparation
of a piece from a rubber sample that is not a
NoTE 4-A film of suitable material, such as a standard vulcanized sheet. These procedures
nonlubricated aluminum foil, 0.1 mm (0.004 in.) should be used in conjunction with procedures
thick, may be placed above and below the sheets in ASTM Method D 412, Tension Testing of
in the mold to prevent contamination with materi- Vulcanized Rubber,< or other standard meth-
als remaining in the mold from previous cures. If ods of test, or in specifications for a particular
foil is used, compensation in weights of unvulcan- article.
ized sheets should be made.
12. Samples
10. Procedure
12.1 Samples shall be obtained, if possible,
10.1 Bring the mold to the curing tempera- from the product to be tested, and in such
ture within ±0.5 C (±0.9 F) in the closed case shall be selected in accordance with the
press, and hold at this temperature for at least requirements of the specification covering the
20 min before the unvulcanized sheets are in- particular material. In case it is not practicable
serted. Verify the temperature of the mold by to obtain suitable specimens from the finished
means of a thermocouple or other suitable article, the manufacturer shall, upon request,
temperature-measuring device inserted in one furnish samples approximately 150 by 150 by
of the overflow grooves and in intimate con- 2 mm (6 by 6 by 0.08 in.) which he certifies to
tact with the mold. Open the press, insert the be of the same material and equivalent cure
unvulcanized sheets into the mold, and close used in the finished article.

the press in the minimum time possible.
12.2 In case the finished article is obtained
NoTE 5-When the mold is removed from the by injection molding, the manufacturer shall,
press to insert uncured sheets, precautions should on request, furnish injection molded samples
be taken to prevent excessive cooling of the mold that he certifies to be the same material and
by contact with cool metal surfaces or by exposure equivalent in cure to that used in the finished
to air drafts. article. The size of the injection molded sam-
ples shall be agreed to by both the manufac-
10.2 The time of vulcanization shall be con- turer and the purchaser.
sidered to be the period between the instant
the pressure is applied fully and the instant 13. Age of Samples
the pressure is released. Hold the mold under
a minimum pressure of 3450 kPa (500 psi) 13.1 All tests shall be made using material
on the ·cavity areas of the mold during vul- that has been aged at least 24 h and not more
canization. As soon as the press is opened, than 60 days .after vulcanization, except that,
remove the vulcanized slieets from the mold when the date of vulcanization is not known,
and cool in water (room temperature or lower) tests shall be made within 60 days after de-
or on a metal surface (for items to be used for livery by the manufacturer of the article rep-
electrical measurements) for 10 to 15 min. resented by the sample.
Then wipe dry the sheets cooled in water and
reserve for test. In both of the preceding op- 13.2 Samples that have been buffed shall
erations take care to prevent undue stretching be allowed to rest at ieast 30 min before speci-
or deformation.
• /974 Annual Book of ASTM Standards, Part 37.
10.3 Store vulcanizates of compounds pre-

4

mens are cut for testing. 0 15

14. Separation of Rubber with further examination or tests, and the re-
moval of fabric backings from articles.
\4. l In certain tests it is necessary to re-
move the rubber from the fabrics or other \5.2 Apparatus-The buffing apparatus
materials before conducting the test. The sep- shall consist of a grinder with motor-drive
aration shall be performed without the use of abrasive wheel of approximately 30 grit, \25
a solvent, if practicable, and without excessive mm (S in.) in diameter, and revolving at a
stretching of the rubber. The separation shall speed of 2500 to 3500 rpm. Larger wheels may
be made a little at a time while the rubber is be used, provided the speed is adjusted to give
gripped near the point of separation. If it is a surface speed equivalent to a \25-mm (S-in.)
necessary to use a solvent in the separating wheel operating at 2500 to 3500 rpm. The
operation, commercial isooctane shall be grinder shall also be equipped with a slow
used. If isooctane is used, the rubber shall be feed, in order that very little of the material
placed so as to permit free evaporation of the will be removed at one cut. The face of the
solvent from all parts of its surface, and shall wheel shall be kept sharp during operation.
be allowed to rest at least \ h before being
tested. I 5.3 Procedure-The speed of the abrasive
wheel shall be 1200 ±200m (4000 ±700ft)/
15. Buffing and Preparation of Material min. Finish the final buffed surface uniformly
and smoothly. Remove very little material by
l S.l Samples of rubber shall be buffed any one cut so as to avoid damage to the rub-
when necessary to remove unevenness of sur- ber by overheating. Do not carry the buffing
face such as fabric impressions or corrugations beyond the point at which the unevenness of
caused by contact with fabric components or gage just disappears, except in the case of
cloth wraps used for curing that would inter- thick materials. Where it is necessary to re-
fere with measurements of thickness or other duce the thickness of a sample for prepara-
tests. Buffing is also applicable to reducing the tion of test specimens, it may be desirable to
thickness of materials where it is necessary to slice the material to approximately the desired
do so before testing, the removal of glaze or thickness before buffing. Samples of material
skin coats from rubber where it may interfere for preparation of specimens for tension test

shall be buffed in strip form before cutting
out the specimen.

PART R-EVALUATION OF STANDARD AND NONSTANDARD MATERIALS
AND OF COMMERCIALLY AVAILABLE RUBBERS

16. Scope 4A Calcium carbonate compound
SA Electrically conducting compound
16.1 These methods are intended for the 6A Resilient compound, 40 durometer hardness
evaluation of standard materials described in 7A Resilient compound, 50 durometer hardness
Part A, Section 3, and of nonstandard mate- 8A Resilient compound, 60 durometer hardness
rials in a variety of rubbers. Standard recipes
and procedures are given for use in produc- 17.2 Method of Mixing-For mixing natu-
tion control of commercially available rubbers. ral rubber compounds, proceed as follows,
using the time cycles given in Table 4, and
17. Standard Formulas and Procedures- maintaining roll temperature at 70 ± S C
Natural Rubber (158 ± 9 F):

17.1 Standard formulas and time cycles for 17.2.1 Pass rubber through the rolls twice,
mixing for the following natural rubber com- without banding, at a mill roll opening of 0.20
mm (0.008 in.).
pounds are given in Tables 3 and 4, respec-
17 .2.2 Band with mill opening at 1.4 mm
tively: (0.055 in.) and break down, opening the mill
to 1.9 mm (0.075 in.) as the band becomes
Number Purpose or Description smooth.

IA Compound for classification of natural rubber 17.2.3 Add main pigment evenly across the
2A Gum compound rolls at a constant rate, and open the mill at

3A Channel black compound

5

0 15

intervals to maintain an approximately con- hundred rubber) basis. Table 6 is therefore in-
stant bank. When about half the pigment is
incorporated and all dry pigment in the bank cluded mainly for information purposes.

3 18.3 Table 7 contains Type B standard

has disappeared, make one /4 cut from each formulations. These are consistent with cur·
side. Then continue with the balance of the
pigment. Be certain to add the pigment that rent compounding practice in regard to sulfur
drops through to the mill pan (Note 2).
and accelerator content. The report should
17.2.4 Add stearic acid.
17 .2.5 Add other materials. clearly state whether Type A or Type B stand-
17.2.6 Make three 3/4 cuts from each side.
17.2.7 Cut the batch from the mill. Set the ard formulations are used.
opening at 0.8 mm (0.033 in.) and pass the
rolled stock endwise through the mill six 18.4 Preparation of Compo!)ite Samples
times.
17.2.8 For compounds 3A to 8A, sheet the for Physical Testing-This procedure de-
batch to a minimum thickness of 6 mm (0.25
in.) and weigh. For compounds lA and 2A, scribes the method of making a composite
sheet to 2.2 mm (0.085 in.).
17.3 Preparation of Compounds: sample of a specific lot of SBR for specifica-
17.3.1 Condition compounds lA and 2A

for I to 6 h after mixing, prepare slabs as , tion testing. It is not necessary for in-plant
shown in 8.3, and cure as shown in 17 .4. Do
not remill. quality or control testing.
17.3.2 Condition compounds 3A to 8A for
I to 24 h, rem ill in accordance with 8.1, con- 18.4.1 Take samples for physical testing
dition 1 to 6 h, prepare slabs as shown in 8.3,
and cure as shown in 17.4. from the lot according to the procedure de-
17.4 Recommended Standard Cures-10,
20, 40, and 80 min at 140 C (284 F). scribed in ASTM Method D 1485, Sample

18. Standard Formulas and Procedures-Sty- Preparation of Solid Raw Rubbers!
rene-Butadiene Rubbers, Nonpigmented
Types 18.4.2 Blend a minimum of 1000 g of the

18.1 Standard formulas for mixing the unpremasticated bale samples by passing five
styrene-butadiene rubber compounds are
given in Tables 5, 6 and 7. Time cycles are times through a roll mill set at 3 mm (0.120
listed in Table 8.
in.). Roll up the rubber between passes and
· 18.1.1 Table 5 contains Type A formula-
tions. These are written on the basis of 100 pass endwise through the mill.
parts of oil-extended masterbatch when such
a masterbatch is evaluated. This method of 18.5 Method of Mixing-The mill mix
recipe formulation is used for simplicity of op-
eration in everyday quality control testing. batch size shall be determined by the batch

18.2 Table 6 contains the equivalent recipes factor shown in Tables 5 or 7. The batch size
of Table 5 when the various OE-SBR's are
used in formulation 9B. These formulations is calculated by multiplying the formulation
are expressed on a 100 part rubber basis.

Rubber refers to the commercial nonoil ex- total weight by the batch factor. For mixing
tended material with a few percent of nonrub-
ber content. The formulations are expressed in nonpigmented styrene-butadiene rubber com-
this way so the content of each material is
clearly indicated on the PHR (parts per pounds, use the following procedure with the

mill roll temperature maintained at 50 ± 5 C

(122 ± 9 F) and the time cycle specified in

Table 8.

18.5.1 Band with mill opening at I mm

(0.045 in.) and make /4 cuts every /2 min3 1

from alternate sides. (All mill openings shown

are approximate and should be adjusted to

maintain a good working bank at the nip of

the rolls.)

18.5.2 Add sulfur slowly and evenly across

the rubber.

3

18.5.3 Add stearic acid. Make one /4 cut

from each side after stearic acid is added.

18.5.4 Add carbon black evenly across the

mill at a uniform rate. When about half the

pigment is incorporated, open the mill to 1.25

mm (0.050 in.) and make one 3 cut from each
/4

side. Then add the remainder of the pigment.

When all the pigment has been incorporated,

open the mill to 1.4 mm (0.055 in.) and make

3

a /4 cut from each side. Be certain to add

the pigment that drops through to the mill

pan.

6

D 15

18.5.5 Add other materials at a 1.4-mm compounds are given in Tables 9 and 10, re-
spectively:
(0.055-in.) setting.

18.5.6 Make three 3 cuts from each side.
/,

18.5.7 Cut the batch from the mill. Set the Number Purpose or Description
5C
opening at 0.8 mm (0.032 in.) and pass the For evaluation of both styrene-butadiene rubber-
carbon black and oil-carbon black master-
rolled stock endwise through the mill six batch compounds

times.

18.5.8 Open the mill to give a minimum

stock thickness of 6 mm (0.25 in.) and pass 19.2 Method of Mixing-For mixing pig-

the stock through four times, folding it back mented styrene-butadiene rubber compounds,

on itself each time. Weigh the batch and record proceed as follows, using the time cycle as

the weight. If outside ± 1.0 percent reject given in Table 10, and maintaining roll tem-

the batch. From the stock, cut enough sample perature at 50 ± 5 C (122 ± 9 F):

to allow for testing of compounded viscosity 19.2.1 Band the unmassed masterbacth on

as described in ASTM Method D 1646, Test the front roll with the mill set at 1.4 mm

for Viscosity and Curing Characteristics of (0.055 in.) and break down without cutting.

Rubber by the Shearing Disk Viscometer.' 19.2.2 Add sulfur and zinc oxide slowly and

18.5.9 Sheet off at 2.2 mm (0.085 in.) evenly across the rubber.

finished thickness, cool on a flat metal surface. 19.2.3 Add stearic acid and make one %

ll\.6 Preparation ofCompounds in 18.7.1- cut each side after the stearic acid is added.

Condition all compounds as prescribed in Ta- 19.2.4 Add the accelerator.

ble I, rem ill factory mixes in accordance with 19.2.5 Make three 3 cuts each way (20-s
/,

8.1, and prepare slabs in accordance with 8.3 interval between each cut).

and cure as shown in 18.7.1. 19.2.6 Cut the batch from the mill. Set the
18.7 Recommended Standard Cures:
opening at 0.8 mm (0.032 in.) and pass the

18.7.I Stress-Strain Properties-Vulcanize rolled batch endwise through the mill six

the sheets in accordance with Section 8 and 10 times.

for 25, 35, and 50 min at 145 C (293 F) and 19.2.7 Open the mill to give a minimum

measure tensile strength, ultimate elongation, stock thickness of 6 mm (0.25 in.) and pass

and stress at 300 percent elongation in accord- the stock through the mill four times, folding

ance with Method D 412. it back on itself each time. Weigh the batch.

18.7.2 Viscometer Cure-An alternative to 19.2.8 Cut from the batch enough sample

measuring the stress-strain properties of vul- to allow testing for compound viscosity and

canizates cured for 25 and 35 min is the meas- viscometer cure in accordance with Method

urement of the time of incipient cure and cure D 1646, or for cure meter characteristics in

index at 150 C (302 F) in accordance with accordance with Method D 2084, or both.

Method D 1646. 19.2.9 Band the remaining stock on the

18.7.3 Cure Meter-A second alternative to mill and sheet off at 2.2 mm (0.085 in.) fin-

measuring the stress-strain properties of vul- ished thickness and cool on a flat dry metal

canizates is the measurement of vulcanization surface for use in preparing vulcanized stress-

parameters at 160 C (320 F) in accordance strain sheets. Prepare sheets in accordance

with ASTM Method D 2084, for Measure- with 8.3.

ment of Curing Characteristics with the Os- 19.3 Condition and Cure of Compounds-

cillating Disk Cure Meter.' Values of ts2, tc Condition all compounds as prescribed m

(50), tc (90), M H and M L shall be determined. Table I. Cure in accordance with 19.4.

19. Standard Formula and Procedure- 19.4 Recommended Standard Cures:
Styrene-Butadiene Rubbers, Pigmented
Types 19.4.1 Stress-Strain Properties-Vulcanize

19.1 Standard formula and time cycle for the sheets in accordance with Sections 8 and
mixing pigmented styrene-butadiene rubber
10 for 25, 35, and 50 min at 145 C (293 F) or

20, 25, and 40 min at 150 C (302 F) (Note 6)

and measure the tensile strength, ultimate

7

D 15

elongation, and stress at 300 percent elongation 20.2.7 Add 2-mercaptoimidazoline.
in accordance with Method D 412.
3
NOTE 6-The series of cures at 150 C (302 F)
does not necessarily give results equal to those at 20.2.8 Make three /4 cuts from each side.
145 C (293 F). 20.2.9 Cut the batch from the mill. Set the
opening at 0.8 mm (0.032 in.) and pass the
19 .4.2 Viscometer Cure-An alternative rolled stock endwise through the mill six
to measuring the stress-strain properties of times.
vulcanizates is the measurement of the time 20.2.1 0 Sheet off at 2.2-mm (0.085-in.) fin-
of incipient cure and cure index at 150 C (302 ished gage, cool on a fiat metal surface, and

F) in accordance with Method D 1646. prepare samples for cure in accordance with
8.3.
19.4.3 Cure Meter-A second alternative 20.3 Preparation of Compounds-Condi-
to measuring stress-strain properties of vul- tion the compounds for I to 6 h after mixing,
canizates is the measurement of vulcanization prepare slabs as shown in 8.3, and cure as
parameters at 160 C (320 F) in accordance shown in 20.4. Do not remill.·
with ASTM Method D 2084, Measurement of 20.4 Recommended Standard Cures-15,
Curing Characteristics with Oscillating Disk 30, and 60 min at 150 C (302 F).
Cure Meter•. The frequency of rotary oscil-
lation of the cure meter disk shall be constant 21. Standard Formulas and Procedures-Butyl
at 1.7 Hz (100 cpm). Values of 15 (2), lc (50), lc Rubber
(90), M H. and M L shall be determined.
21.1 Standard formulas and time cycles for
20. Standard Formulas and Procedures-Neo- mixing for the following butyl rubber com-
prene Rubber pounds are given in Tables 13 and 14, respec-
tively:
20.1 Standard formulas and time cycles for
mixing for the following neoprene rubber Number Purpose or Description
compounds are given in Tables II and 12, re-
spectively: IE Gum compound
2E Channel black compound
3E Oil furnace black compound

Number Purpose or Description 21.2 Method of Mixing-For mixing butyl
compounds, proceed as follows, using the time
I D Gum compound
2D Semi-reinforced furnace carbon black com- cycles given in Table 14, maintaining roll tem-
perature at 40 ± 5 C (104 ± 9 F): ·
pound

20.2 Method of Mixing-For mixing neo- 21.2.1 Band rubber with mill opening of
prene compounds, proceed as follows, using 0.65 mm (0.025 in.).
the time cycles given in Table 12, and main-
taining roll temperature at 50 ± 5 C (122 ± 21.2.2 Mix carbon black and stearic acid
and add evenly across the rolls at a constant
9 F):
20.2.1 Band neoprene with mill opening at rate. Open the mill at intervals to maintain

1.5 mm (0.060 in.). an approximately constant bank. When all
20.2.2 Add magnesium oxide.
20.2.3 Add antioxidant (phenyl beta naph- the pigment has been added, make a 3 cut
/4

thylamine). from each side. Be certain to add all the pig-
20.2.4 Add stearic acid. ment that drops through to the pan (Note 2).
20.2.5 Add carbon black evenly across the
21.2.3 Add other materials.
rolls at a constant rate, and open the mill at
intervals to maintain an approximately con- 21.2.4 Make three 3 cuts from each side.
stant bank. When about half the black is in- /4
corporated and all dry black in the bank has
21.2.5 Cut the batch from the mill. Set the
3
opening at 0.8 mm (0.032 in.) and pass the
disappeared, make one /4 cut from each
side. Then continue with the balance of the rolled stock endwise through the mill six
black, being certain to add all the black that times.
drops through to the mill pan (Note 2).
21.2.6 Sheet off at 2.2-mm (0.085-in.) fin-

ished gage, cool on a fiat metal surface, and

prepare samples for cure in accordance with

20.2.6 Add zinc oxide. 8.3.
21.3 Preparation of Compounds-Condi-

8

D 15

tion the compounds for I to 6 h after mixing, tion the compound for I to 6 h after miXIng,
prepare slabs as shown in 8.3, and cure as prepare slabs as shown in 8.3, and cure as
shown in 21.4. shown in 22.4.

21.4 Recommended Standard Cures- The 22.4 Recommended Standard Cures-10,
recommended cures for the recipes shown in 20, 40, and 80 min at 150 C (302 F).
Table 13 are, respectively:

Recipe Minutes at 150 C (302 F) 23. Standard Formulas and Procedures-Solu-
tion Polybutadiene Rubber
IE 25, 50, and 100
2E 25, 50, and 100 23.1 A standard formula and mixing pro-
3E 20, 40, and 80 cedure for the following solution polybuta-
diene compound is given in Tables 17 and 18,
22. Standard Formulas and Procedures-Nitrile respectively:
Rubber

22.1 A standard formula and mixing pro- Number Purpose or Description
cedure for the following nitrile rubber com- I H

pound is given in Tables 15 and 16, respec- For evaluation of solution polybutadiene rub-
tively: bers

Number Purpose or Description For mixing by Internal Mixer (Method A and
Gas furnace compound B) use recipe weight outlined in 6.1 and 6.2.
IF' For mixing by laboratory mill, use a batch
size four times the recipe weight-Method C.
22.2 Method of Mixing-For mixing nitrile
rubber compound IF, proceed as follows, 23.2 Method of Mixing- The mill handling
using .the cycle as given in Table 16, and main- characteristics of the polybutadienes is some-
what more difficult than for other polymers.
taining roll temperature at 50 ± 5 C (122 ± Mixing is more easily accomplished in an in-
9 F): ternal mixer. Results from mill mixing in
some instances may not correlate with results
22.2.1 Pass rubber through the rolls twice, obtained from Banbury mixing. The following
without banding, at a mill roll opening of 0.20 three mixing procedures are offered:
mm (0.008 in.).
Method A -Internal Mixer for initial and final mix.
22.2.2 Band with mill opening at 1.4 mm Method B Initial Internal Mixer with final mill mix.
(0.055 in.) and break down. Method C -Mill mix.

22.2.3 Add stearic acid. For mixing in an internal mixer refer to 6.1
22.2.4 Add zinc oxide, sulfur, and benzo- for equipment description. For mixing on a
thiazyl disulfide. mill refer to 5.1. See Table 18 for time cycles
22.2.5 Make one 3/4 cut from each side.
22.2.6 Add black evenly across the rolls at involving each step of the mixing procedure.
a constant rate, and open the mill at intervals 23.3 Internal Mixer for Initial and Final
to maintain an approximately even bank.
When about half the black is incorporated Mix-Method A:
and all the dry pigment in the bank has dis- 23.3.1 Initial Mix Procedure-Stage 1:

23.3.1.1 Adjust the Banbury temperature
3
to achieve the discharge conditions outlined
appeared, make one /4 cut from each side. in 23.3.1.4. Close the discharge gate, start the
Be certain to add all the pigment that drops rotor, raise the ram, and charge the ingredi-
through to the mill pan. Then continue with ents as described.
the balance of the black (Note 2).
23.3.1.2 Charge one half the polymer, zinc
3 oxide, carbon black, oil, stearic acid, and the
balance of the polymer. Lower the ram.
22.2.7 Make three /4 cuts from each side.
22.2.8 Cut the batch from the mill. Set the 23.3.1.3 Raise the ram and clean the mixer
opening at 0.8 mm (0.032 in.) and pass the throat and the top of the ram. Lower the ram.
rolled stock endwise through the mill six
23.3.1.4 Discharge the batch at 165 ± 5 C
times.
22.2.9 Sheet off at 2.2-mm (0.085-in.) fin- (330 ± 9 F) or 6 min, whichever occurs first.
23.3.1.5 Pass the batch immediately
ished gage, cool on a flat metal surface and
prepare samples for cure in accordance with through a laboratory mill three times as de-
scribed in 5.1 set at 5.0 mm (0.20 in.) and 50
8.3.
22.3 Preparation of Compound-Condi-

9

0 15

± 5 C (122 ± 9 F). Check the weight of the 23.4.3 Preparation of Compounds-Condi~

batch as described in 5.4. tion the compounds for I to 6 h after mixing,

23.3.1.6 Rest the stock for 1 h minimum. prepare slabs as shown in 8.1, and cure as
/2

23.3.2 Final Mix Procedure-Stage 2: shown in 23.3.4.

23.3.2.1 Cool the Banbury with full cool- 23.5 Mill Mix Procedure-Method C:

ing water on the rotor to 40 ± 5 C ( 104 ± 23.5.1 With mill roll temperature set at

9 F), start the rotor, raise the ram, and charge 50± 5 C (122 ± 9'F) and 1.3 mm (0.05 in.),

the materials as described. add ingredients as described.

23.3.2.2 Leaving the cooling water on and 23.5.2 Band polymer on front roll.

the steam off, charge one half the master- 23.5.3 Add zinc oxide and stearic acid

batch, with all the sulfur and accelerator evenly across the rolls. Make two 3 cuts
/4

rolled into this portion of the masterbatch from each side.

before feeding to the mixer. Add the remain- 23.5.4 Add the carbon black evenly across

ing portion of the masterbatch. Lower the 1

the rolls until /2 the carbon black has been

ram. added. Open the rolls to 1.8 mm (0.07 in.) and

23.3.2.3 Discharge the batch at 110 ± 5 C continue the carbon black addition, being cer-

1 tain that all the black that drops through to

(230 ± 9 F) or 2 /2 min, whichever occurs

first. the mill pan is added. Make two 3 cuts
/4

23.3.2.4 Pass the batch immediately from each side, allowing 30 s between each

through a laboratory mill described in 5.1 set cut.

at 0.8 mm (0.032 in.) and 50 ± 5 C (122 ± 23.5.5 Add the oil slowly.

9 F). 23.5.6 Add the sulfur and accelerator.

23.3.2.5 Reroll the batch and pass the 23.5.7 Make six successive 3 cuts from
/ •

batch endwise through the mill ten times each side.

without banding. 23.5.8 Cut the batch from the mill. Set the

23.3.2.6 Sheet the stock to a minimum mill roll opening at 0.8 mm (0.032 in.) and

thickness of 6 mm (0.25-in.). pass the rolled stock endwise through the

23.3.3 Preparation of Compounds-Condi- mill six times and check the weight.

tion the compounds for I to 6 h after mixing, 23.5.9 Sheet the stock to a minimum thick-

prepare the slabs as shown in 8.I, and cure ness of 6 mm (0.25 in.).

as shown in 23.3.4. 23.5.10 Preparation of Compounds-Con-

23.3.4 Recommended Standard Cures- dition the compounds for 1 to 6 h after mix-

25, 35, and 50 min at 145 C (293 F). ing, prepare slabs as directed in 8.1, and cure

23.4 Initial Internal Mixer with Final Mill as directed in 23.3.4.

Mix-Method 8:

23.4.1 Initial Mix Procedure-Stage I: 24. Standard Formulas and Procedures-Poly-
isoprene Rubber
23.4.1.1 Follow the procedure outlined in
24.1 A standard formula and mixing pro-
23.3.1. cedure for the following polyisopr.::ne rubber
compound is given in Tables 19 and 20 re-
23.4.2 Final Mill Mix-Stage 2: spectively:

23.4.2.1 With the mill roll set at 50 ± 5 C

(122 ± 9 F) and 1.5 mm (0.06 in.) add the

materials as described. Adjust the batch

weight to four times the recipe weight. Number Purpose or Description

23.4.2.2 Add the sulfur and accelerator 1-1 Oil furnace black (HAF type) compound

slowly to the batch. 24.2 Method of Mixing-For mixing poly-
23.4.2.3 Make six 3/4 alternate cuts. isoprene rubber compound 1-1, proceed as
follows, using the cycle as given in Table 20,
23.4.2.4 Cut the batch from the mill and and maintaining roll temperature at 70 ± 5 C
(158 ± 9 F):
set the mill roll opening at 0.8 mm (0.032 in.).
24.2.1 Pass the rubber through the rolls
Pass the stock through the rolls endwise five twice without banding, at a mill roll opening
of 0.5 mm (0.020 in.).
times.

23.4.2.5 Sheet the stock to a minimum

thickness of 6 mm (0.25 in.).

10

D 15

24.2.2 Band the rubber on the front roll 24.2. 7 Roll the stock from the mill, weigh
and record the percent gain or loss from the
with the mill opening at 1.4 mm (0.055 in.). recipe batch weight. If it is outside ± 1.0 per-
Make two 314 cuts from each side. cent, reject the batch.

NoTE 7 -Some types of polyisoprene go to the 24.2.8 Set the mill opening at 0.8 mm
back roll. in which case the stearic acid should be (0.032 in.). Roll and pass the stock endwise

added and after incorporation can usually be trans- through the mill six times.
ferred to the front roll. Also tougher types may re-
quire slightly longer breakdown before addition of 24.2.9 Sheet off at 2.2 mm (0.085 in.) fin-
other pigments. ished thickness, cool on a flat metal surface,
and prepare the samples for cure in accord-
24.2.3 Set the mill opening at I. 7 mm ance with 8.3 and cure as shown in 24.3.1.

(0.067 in.). Add stearic acid and that which 24.3 Recommended Standard Cures:
24.3.1 Stress-Strain Properties- Vulcanize
falls into mill pan. Make one 314 cut from the sheets in accordance with Sections 8 and
10 for 20, 30, 40, and 60 min at 135 C (275 F)
each side.
and measure the tensile strength, ultimate
24.2.4 Add. zinc oxide and sulfur and that elongation, and stress at 300 percent elonga-
tion in accordance with Method D 412.
which falls into the mill pan. Make one 3
24.3.2 Viscometer Cure-An alternative to
14 measuring the stress-strain properties of vul-
canizates is the measurement of the time of
cut from each side. incipient cure and cure index at 150 C (302 F)
in accordance with Method D 1646.
24.2.5 Add half of the dried carbon black
24.3.3 Cure Meter-A second alternative
evenly along the bank of rubber at a uniform to measuring the stress-strain properties of
vulcanizates is the measurement of vulcaniza-
rate. When about half the black has been tion parameters at 150 C (302 F) in accordance

added, open the mill to 1.9 mm (0.075 in.). with Method D 2084. Values of t."' lc(50),

When all the unincorporated black in the bank lc(90), M H, and M L shall be determined.

has disappeared, make one 3 cut from each

14

side and then add the other half of the black

as above. Sweep the mill pan and add the

black. When all the black has been incorpo-

rated, make one "I 4 cut from each side.

24.2.6 Add the accelerator, taking care to

avoid any loss. Sweep the mill pan and add

until all the pigment is in the batch. Make

3

three 14 cuts from each side.

PART C-EVALUATION OF CARBON BLACKS IN NATURAL RuBBER

25. Scope black has desirable properties nor that pro-
duction of blacks should be directed to match
25.1 These methods are for testing carbon its properties. The use of a reference black is
blacks when incorporated in rubber. They simply a device to cancel the inevitable vari-
may be used for checking the properties of ations in test results which are due to minor

the blacks being produced by the manufac- variations between laboratories in equipment,
turers or for testing shipments of blacks as procedures, and ambient conditions.
received by a consumer.
26. Standard Formula
25.2 These procedures involve the incor-
poration of the black to be tested in rubber 26.1 The standard formula and miXIng
along with the necessary auxiliary agents to method for testing carbon blacks are given in
permit vulcanization, followed by testing. All Tables 17, 18, and 19, respectively.
materials except the black to be tested are
reference materials of controlled and uniform 26.2 The carbon black shall be conditioned
properties as described in Part A of these in accordance with 4.3.
methods. Along with each test black or series Tables 21, 22, and 23, respectively.
of test blacks, a corresponding stock contain-
ing the reference black is included. The dif- 27. Methods of Mixing
ferences between the properties obtained on
the reference black and test black are noted. 27.1 Mill-For mixing on a mill as de-
The methods do not imply that the reference scribed in 5.1, proceed as follows, using the
time cycle specified in Table 22.

11

~~~~ D 15

27 .1.1 Set mill opening at 1.4 mm (0.055 Natura\ rubber' . 100.0
in.) and adjust and maintain roll temperature Zinc oxide (NBS 370) . 5.0
at 70 ± 5 C (158 ± 9 F). Stearic acid (NBS 372) 3.0
Sulfur (NBS 37\) . . . . . . .. 2.5
27 .1.2 Add rubber and band on mill. Benzothiazy\ disulfide (NBS 373) 0.6
27 .1.3 Add stearic acid and cut once each
way. 'Available from the Firestone Tire and Rubber Co

27.1.4 Add sulfur, accelerator, and zinc Specially selected Liberian crepe with 600 percent modulu~
oxide and cut twice each way. of 700 ± \00 psi when tested in compound \A.
27 .1.5 Add black. Open the mill gradually
to maintain an approximately constant bank The masterbatch may be prepared either in
and cut three times each way after all the conformance with 27 .I using a mill mixing
black is in. Be certain to add all the pigment method or in an internal mixer as follows
that has dropped through to the mill ·pan _using the time cycle as given in Table 24: '
(Note 2).
28.1.1 Regulate the temperature on the
27 .1.6 Cut stock, roll, and weigh. If the rotors and shell to obtain a dump temperature
weight is outside the tolerance of ± 1 percent, between 110 and 125 C (230 and 257 F).
reject the batch.
28.1.2 Add rubber.
27.1.7 Pass endwise six times at 0.8-mm 28.1.3 Add benzothiazyl disulfide.
(0.032-in.) opening and sheet off to 2.2-mm 28.1.4 Add stearic acid.
(0.085-in.) finished gage. Cool on a metal
table top and prepare samples for cure as 28.1.5 Add zinc oxide.
shown in 8.3. 28.1.6 Add sulfur.
28.1.7 Dump.
27.2 Internal Mixer-For mixing in an 28.1.8 Sheet immediately from the mill set
internal mixer, as described in 6.1, proceed at a mill opening of 6 to 10 mm (0.25 to 0.4
as follows, using the time cycle as given in
Table 23: in.), and allow to cool to room temperature
before piling or stacking.
27 .2.1 Regulate the temperature on the
rotors and shell to obtain a dump tempera- 28.2 For incorporation of black into the
masterbatch using a standard mill and a
ture between 110 and 125 c (230 and 257 F).
batch size that is four times the recipe weight,
27.2.2 Add rubber. proceed as follows, using the time cycle as

27.2.3 Add benzothiazyl disulfide. given in Table 25:
27.2.4 Add stearic acid.
27.2.5 Add the zinc oxide and half the 28.2.1 Set the mill opening at 1.4 mm
black. (0.055 in.) and adjust and maintain the roll
temperature at 70 ± 5 C (158 ± 9 F).
27 .2.6 Add remainder of the black.
27.2.7 Add sulfur. 28.2.2 Add masterbatch and band on mill.
27.2.8 Dump. 28.2.3 Cut six times each way.

27.2.9 Sheet immediately from the mill set 28.2.4 Add black. Open the mill gradually
at a mill opening of 2.2 mm (0.085 in.) and a so as to maintain a constant bank. Be certain
to incorporate all the black that has dropped
roll temperature of 70 ± 5 c (158 ± 9 F).
through to the mill pan. After all the black
Band, cut, roll up, and weigh. If the weight has been worked into the batch, cut three
is outside the tolerance of ± 1 percent, re- times each way (Note 2).
ject the batch.
28.2.5 Cut stock from the mill, roll up, and
27.2.10 Pass endwise six times at a 0.8-mm weigh. If the weight is outside the tolerance
(0.030-in.) opening. of ±I percent, reject the batch.

27.2.11 Sheet off at 2.2-mm (0.085-in.) fin- 28.2.6 Pass through the mill endwise six
ished gage, cool on a flat metal surface, and times at a 0.8 mm (0.032 in.), cool on a flat
prepare specimens for cure as described m
8.3. metal surface, and prepare specimens for
cure as described in 8.3.
28.. Preparation and Use of Masterbatches ·
28.3 For incorporation of black into the
28.1 A masterbatch of the following com- masterbatch using an internal mixer, proceed
position may be used: as follows, using the time cycle as given in

Table 26:

28.3.1 Regulate the mixer to obtain a dump
temperature between 110 and 125 C (230 and

12

257 F). D 15
28.3.2 Add masterbatch.
28.3.3 Add· half of the black. tion of a mild soap or a dilute silicone-type
28.3.4 Add the remainder of the black. lubricant may be used. The mold surfaces
28.3.5 Raise the ram and sweep down. should be kept clean at all times.
28.3.6 Dump.
28.3.7 Pass through the mill twice set at 29.3 Recommended cures for tensile sheet
thickness for stocks containing furnace blacks
2.2 mm (0.085 in.) and a roll temperature of are IS and 30 min at 145 C (293 F) and 30 and
50 min at 145 C (293 F) for channel black
70 ± 5 C (158 ± 9 F). Roll up and weigh. If stocks. In both cases the stocks containing the
reference black shall be cured for the same
the weight is outside the tolerance of ±I per- times as those containing the test blacks.
cent, reject the batch.
29.4 The time interval between curing and
28.3.8 Pass endwise six times through the testing shall be a minimum of I h and a max-
mill at a 0.8-mm (0.032-in.) opening. Sheet imum of 72 h.
from the mill set at 2.2 mm (0.085 in.), pre-
pare samples for cure in accordance with 8.3, 30. Report
and cure as shown in 29.3.
30.1 The report shall include the designa-
29. Preparation and Curing tion of the carbon blacks used, and a tabula-
tion of the data obtained along with the cor-

29.1 The time between sheeting and curing responding data on the reference black
shall be I h minimum to 24 h maximum. employed. The differences between the val-
ues for the reference black and the unknown
29.2 Normally a mold lubricant is not nec- black shall also be tabulated.
essary but when it is necessary, a dilute solu-

TABLE I Time of Stock Conditioning, in Hours TABLE 2 Weight of Slabs to be Placed in Molds
Non-Factory mixes are to be remilled according to Described in 8.3
8.2 with a minimum time of I h between mixing and re-
milling. Specific Gravity Weight. g

Compound After After 0.94 52
Mixing Curing
0.96 53

0.98 54

Natural: LOO 55
lA and 2A
3A to 8A I to 6 I to 96 1.02 56
I to 24 I to 96
Styrene-butadiene: 1.04 57
98, lOBI to 6 1 to 24 I to 96
1181 to6 I to 24 I to 96 1.06 58
1Cto5C 1 to 24 I to 96
1.08 59
Neoprene: Ito 6 I to 96
ID and 20 L 10 60
I to 6 I to 96
Butl'l: I. 12 61

I.E to 3E I to 6 I to 96
I. 14 62
Nitrile: I to 24 I to 72
IF I. 16 63
I to 6 I to 96
Carbon black: I. 18 64
IG I to I to 96
I. 20 65
Poll'butadiene:
(H I. 22 66

Po/yisoprene: 1.24 67

II I. 26 68

I. 28 69

I. 30 70

13

~m~ o 15

TARLE 3 Standard Formulas for Natural Rubber Compounds
NOTE Recipe 1-1 in Table 19 is recommended for use when evaluating or testing natural rubber for intended carbon black
pigmented products.

NBS

Material Standard lA 2A 3A 4A SA 6A 7A SA

Natural rubber Sample No.
Zinc oxide
Sulfur 385 100 100 100 100 100 100 100 100
Stearic acid
Mercaptobenzothiazole 370 6 5 5 5 5 5 5 5
Benzothiazyl disulfide
Phenyl beta naphthylamine 371 3. 5 2.5 3 3 3 2.5 2. 5 2.5
Channel black
Calcium carbonate 372 0.5 2.0 3 3 3 I I I
Conducting furnace black
Gas furnace black 383 0.5
Specific gravity (calculated)
373

377

375

380

379 40

382 20 45 70

0.99 I. II 1.05 1.12 I. 18

TABLE 4 Time Cycles For Mixing Natural Rubber TABLE 5 Type A-Standard Formulations for
Compounds, in Minutes Styrene-Butadiene Rubbers

Step No. Natural Rubber Compound No. NBS 9B

lA, 2A 3A 4A SA 6A 7A SA SBR or OE-SBR 370 100.00
Zinc oxide 372 3.00
I I I I I I I I Stearic acid 371 1.00
Sulfur 378 I. 75
2 4 4 2 4 4 4 4 Furnace black' 384
TBBS 50.00
3 II 8 12 7 8 9 _l.J!Q.
Batch factor 156.75
4 2 22 2 2 2 2
3.0
5 4 4 2 4 4 4 4

6 2 2 I 2 2 2 2

7 2 22 2 2 2 2

8 I I I I I I I

Total 16 27 19 28 23 24 25 'Current Industry Reference Black (IRB) may be used
in place of NBS 378, although slightly different results
may be obtained. Weight ingredients to nearest 0.1 g for
SBR and carbon black and to the nearest 0.01 g for other
ingredients.

TABLE 6 Type A_.Standard Formulations for Styrene-Butadiene Rubber Compounds (expressed
on 100 Part Rubber Basis)

Material NBS lOBI IOB2 1083 1084 lOBS 1086

Non-OE 25-0il 37.5-0il 50-0il 62.5-0il 75-0il
Rubbers Rubbers Rubbers Rubbers Rubbers Rubbers

SBR 100.00
OE-SBR
Zinc oxide 125.00 137.50 150.00 162.50 175.00
Stearic acid
Sulfur 370 3.00 3. 75 4. 12 4.50 4.88 5. 25
Furnace blacka
TBBS 372 1.00 I .25 I. 38 1.50 I .63 I. 75

371 I. 75 2.19 2.42 2.63 2.85 3.06

378 50.00 62.50 68.75 75.00 81.25 87.50

384 ___LQQ ~ ~ ___!_2Q __L..QJ I. 75

156.75 195.94 215.55 235. 13 254.74 274.31

a Current Industry Reference Black (IRB) may be used in place of NBS 378, although slightly different results may be
obtained.

14

~m~ D 15

T-\BLE 7 Type B-Standard Formulations for Styrene-Butadiene Rubber Compounds

Material NBS II Bl II B2 II B3 IIB4 II B5 llB6
25-0il 37.5-0il 50-0il 62.5-0il 75-0il Base

Rubbers Rubbers Rubbers Rubbers Rubbers

Masterbdtch 125.00 137.50 150.00 162.50 175.00 100' j
Furnace black" 68.75 75.00 81.25 87.50
Zinc oxide 378 62.50 50(100 + y)O.Ol
Stearic acid 3.00 3.00 3.00 3.00
Sulfur 370 3.00 1.00 1.00 1.00 1.00 3.00
TBBS 1.75 1.75 1.75 1.75
372 1.00 1.38 1.50 1.63 1.75 1.00

371 1.75 1.75

384 1.25 I (100 + y)O.Ol

194.50 213.50 232.25 251.13 270.00

Batch f::."t0r 2.5 1.5

"Current Industry Reference Black (IRB) may be used in place of NBS 378, although slightly different results may be
obtained. For formula IIB6-Y ~parts oil PHR calculate all parts to nearest 0.01 parts. Weigh ingredients to nearest 0.1 g

for SBR and carbon black and to nearest 0.01 g for all other ingredients.

TABLE 8 Time Cycles for Mixing Styrene-Butadiene TABLE 10 Time Cycles ·for Mixing Pigmented Styrene-
Rubber Compounds in Minutes Butadiene Rubber Compounds, in Minutes

Mixing step of 18.5 Duration. min Styrene-Butadiene Rubber

l 7 Compound No. 5C
2 2

3 2 Step l 2
4 10
5 3 2 3
6 2
7 2 3 2
8 l
Total 4 2
29
5 2

6 2

7 l

Total 14

TABLE 9 Standard Formulas for Styrene-Butadiene TABLE II Standard Formulas for Neoprene Rubber
Rubber-Carbon Black and Oil-Carbon Black Masterbatch Compounds"

Compounds NBS
NOTE-Use a formula multiplier of 1.5 to 3.0 in incre-
ments of 0.5 to give the longest total batch mass that will Material St1ndard lD 2D
not exceed 525.0 g.

NBS Sample No.
Standard
Sample SC, Oil-Carbon Neoprene W 100 100
Black 4 4
No. Magnesium oxide 376 0.5 l
Material 29

Stearic acid 372 5 5
0.35 0.5
SRF carbon black 382 2 2

Masterbatch 100 +X"+ Y' Zinc oxide 370 1.29 l. 39
3
Zinc oxide 370 l. 75 2-Mercaptoimidazoline
1.50
Sulfur 371 l. 25 Phenyl beta 377

Stearic acid 372 naphthylamine

TBBS 384 Specific gravity

(calculated)

"X~ parts carbon black per 100 parts base polymer. "For mill mixing use 3 X recipe weight.
' Y ~ parts oil per 100 parts base polymer.
'TBBS is N-lert-butyl-2-benzothiazolsulfenamide.

15

D 15

'fABLE 12 Time Cycles for Mixing Neoprene TABLE IS Standard Formula for Nitrile Rubber
Rubber Compounds, in Minutes Coni pound

Neoprene Rubber NBS
Compound No.
Material Standard IF

Step No. Sample No.

I ID 2D Nitrile rubber 391 100
2 5
3 I Zinc oxide 370 1.5
4 2 I
5 I Sulfur 371 I
6
7 I Stearic acid 372 40
8 5 I. 18
9 2 Benzothiazyl disulfide 373
10 I
I Gas furnace black 382
I
I Specific gravity (calculated)

Total II 16 TABLE 16 Time Cycle for Mixing Nitrile Rubber
Compound, in Minutes

TABLE 13 Standard Formulas for Butyl Rubber Step No. Nitrile Rubber Compound
Compounds' No.
I
Material NBS 2 IF
Standard IE 2E 3E 3
4 I
Sample No. 5 2
6 2
Butyl rubber 388 100 100 100 7 2
8 I

Zinc oxide 370 5 5 3 9 10
2
Sulfur 371 2 2 I. 75 Total 2
I
Stearic acid 372 3 I
23
Benzothiazyl disulfide 373 0.5

Tetramethyl 374 I

thiuramdisulfide

Channel black 375 50

Oil furnace black 378' 50

(HAF type)

Specific gravity 0.97 I. 12 I .13 TABLE 17 Standard Formula for Polybutadiene Rubber
Compound
(calculated)

' For mill mixing use 2 X recipe weight. NBS
• IRB or Industry Reference Black may be used as a
suitable alternative but the same results may not be ob- Material Standard IH
tained.
Sample No.

Poly butadiene 100
3

TABLE 14 Time Cycles for Mixing Butyl Rubber Zinc oxide 370 1.5
Compounds, in Minutes 2
Sulfur 371 0.9

Stearic acid 372 60

Butyl Rubber N-tert-butyl-2- 384 15
Compound No.
benzothiazolesulfenamide I. 14

Step No. Oil furnace black (HAF 378

IE 2E and 3E type)

ASTM Type 103 petroleum

I I oil'

2 10 Specific gravity (calculated)

3 3 ' Defined by ASTM Method D 2226, Recommended
Practice for Description of Types of Petroleum Extender
4 2 Oils.' A lot of oil conforming to the basic description in

5 2 D 2226 and more specifically to the values listed below
can be obtained from Sun Oil Co., Industrial Products
6 I Dept., 1608 Walnut St., Philadelphia, Pa. 19103 (available
in I and 5-gal quantities):
Total 9 19

Viscosity, Saybolt Universal seconds, 85 ±

99 C (210 F)), ASTM Method D 88'

Viscosity-gravity constant' 0.889 ± 0.002

'1973 Annual Book of ASTM Standards, Part 17.

'ASTM Method D 2501, Calculation of Viscosity-
Gravity Constant (VGC) of Petroleum Oils, 1973 Annual
Book of ASTM Standards, Part 18.

16

0 15

TABLE 18 Time Cycle for Adding Ingredients for TABLE 19 Standard Formula for Polyisoprene
Solution Butadiene Rubber Compound

Step No. Time, min NoTE !-Current Industry Reference Black (IRB) may
be used in place of NBS 378, however, slightly different re-
Method A-Internal Mixer (Two-Stage Mix) sults may be obtained.

Stage I (23.3.1) 0.5 NoTE 2-Recipe lA (pure gum) in Table 3 is recom-
I 3.0 mended for use when evaluating or testing natural rubber
2 2.5 intended for use in non-carbon black or unpigmented com-
3
4 6.0 (maximum) pounds.
Total
Material NBS 1-1

Standard Parts
Sample No.

Stage II (23.3.2) Polyisoprene 100.00
I Zinc oxide
2 0.5 Sulfur 370 5.00
3 2.0 Stearic acid
Total 2--:-5 (maximum) N-tert-butyl-2 benzothiazole- 371 2.25

sulfenamide 372 2.00
Oil furnace black (HAF type)"
Method B-Initial Internal Mixer (Stage I) with Final Total 384 0.70
Mill Mix (Stage II) Specific gravity (calculated)

Stage I (23.3.1) 378 35.00
I
2 144.95
3
4 0.5 ·1.09
3.0
Total 2.5 'The carbon black shall be conditioned in accordance
with 4.3
6.0 (maximum)

Stage II (23.4.2) 1.0 TABLE 20 Time Cycle for Mixing Polyisoprene
I 1.5 Rubber Compound, in min
2 1.5
3 I Polyisoprene Rubber Compound
4
5 (maximum) No .. 1-1

5
Total Step I 2

Method C-Entire Mill Mix 2 2

from to 3 2

4 3

I 5 13
2
3 1.0 1.0 6 2
4 2.0 2.0
5 10.0 15.0 to 18.0 7 I
6 4.0 8.0 to 10.0
7 2.0 2.0 8 3
8 2.0 2.0
9 2.0 2.0 9 I
Total 1.0 1.0
24 (maximum) 33.0to38.0 Total 29

TABLE 21 Standard Formula for Testing Carbon Black

NBS

Material Standard IG

Sample

No.

Natural rubber" 100.00
Stearic acid
Zinc oxide 372 3.00
Benzothiazyl disulfide
Sulfur 370 5.00
Carbon black
Specific gravity (calculated) 373 0.60

371 2.50

50.00'

1.13

'Available from the Firestone Tire and Rubber Co.
Specially selected Liberian crepe with 600 per cent modulus
of700 ± 100 psi when tested in compound I A.

' For all carbon blacks except FT and MT. For those
blacks where 75 parts are used, the calculated specific
gravity is 1.19.

17

D 1.5

TABLE 22 Time Cycle for Mixing Natural Rubber - TABLE 25 Time Cycle for Adding Carbon Black to
Carbon Black Compounds Using Roll Mill Natural Rubber Masterbatch Using Roll Mill

Step Number Time, min Step No. Time, min

I I 1.0
2 2.0
2 2.0 3 7.0
4 0.5
3 2.5 5 2.5
6
4 2.0 13.0
Total
5 7.5

6 1.0

7 2.5

Total 17.5

TABLE 23 Time Cycle for Mixing Natural Rubber-Carbon TABLE 26 Time Cycle for Adding Carbon Black Into
Black Compounds Using Internal Mixer Natural Rubber Masterbatch Using Internal Mixer

Step No. Time, min

Step No. Time, min

I I Lower ram after each operation

2 0. 5 Lower ram after each operation 2 I . 0 Lower ram after each operation

3 0, 5 Lower ram after each operation 3 I .0 Lower ram after each operation

4 I .0 Lower ram after each operation 4 I . 5 Lower ram after each operation

5 I . 5 Lower ram after each operation 5 0. 5 Lower ram after each operation

6 I . 5 Lower ram after each operation 6 1.5

7 I .0 Lower ram after each operation 7 1.5

8 1.0 8 2.5

9 2.0 Total 9.5

10 2.0

II 2.0

Total 13.0

TABLE 24 Time Cycle for Mixing Rubber Masterbatch
for Evaluating Carbon Black in Natural Rubber Using !n-
ternal Mixer

Step No. Time, min

I 0. 5 Lower ram after each operation
0. 5 Lower ram after each operation
2 I .0 Lower ram after each operation
3 I .0 Lower ram after each operation
4 I .0 Lower ram after each operation

5 1.0
6 1.0
7
8 6.0

Total

18

~~l~ D 15

Mi II f our corners 3.2 mm (I~8")
for prying mold aport

t ~ f--125 mm (5")--+-

I t ) 12.5 mtm (1/2" l
Mill 0.5mm (0.020")
( deep below depth
of cavity
29mm

(IVa')

150mm
(6")

'--
( 15") 38Omm 01 g J[

~150mm ( 6 " ) -

6.4 mm ~ 6.4 mm (lf4"l-) k-

cw·i- .._ 4.8mm (3/ls''l- f-- Cavities to be
1.9 mm (0.075")
4.8mm
(3/16") deep

( ( )

I I I~ ~I

380mm (15")

14.5mm (0.575"lT1EE~"="="====L~~3.=:2=:m=:m=:(l=:/a=:"l=:R=:.=::=:::::-::4:~

Cover plate to be 12.5mm (0.50") thick.

FIG. I Design for Four-Ca>ity Mold.

19

D 15

150mm Mill 0.5mm (0.020") deep
(6") below depth of cavity

E
E

0
IX)
150mm (6")--~
1'1

6.4mm
( 1/4.) !....-.JI.l'/1*1

Cavities to be
1.9mm (0.075")

deep

~----------380 mm ( 1 5 " ) - - - - - - - - - - + l

_i_ . ,r3.2mm (1/a")R.

~5:~~~~----------~?--------------~

FIG. 2 Cutoff Bar Type of Test of Slab Mold.

20