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है”ह”ह

IS 3660-8 (1999): Methods of Test for Natural Rubber, Part8: Mixing and Vulcanizing of Rubber in Standard Compound[PCD 13: Rubber and Rubber Products]

“ ..--===-J pcw

IS 3660( Part 8 ) :1999

WR7fR7 911*

Iqm-1n

cbw3ti@hmJTm.

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Indian Standard

METHODS OF TEST FOR NATURAL RUBBERPART 8 MIXING AND VULCANIZING OF RUBBER IN STANDARD COMPOUND

[NR:9]

(Second Revision )

ICS 83, 060; 19.020

@ BIS 1999

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

July 1999 Price Group 5

Rubber Sectional Committee. PCD 14

FOREWORD

This Indian Standard ( Part 8 ) ( Second Revision) was adopted by the Bureau of Indian Standards, after thedraft finalized by the Rubber Sectional Committee had been approved by the Petroleum, Coal and RelatedProducts Division Council.

Methods of test for natural rubber had been originally covered in the following four parts:

IS 3660( Part I ) :1972 Determination of dirt, volatile matter, ash total copper, manganese, rubber hydrocarbon,viscosity ( shearing disk viscometer ), and mixing and vulcanizing of rubber in a standard compound[ subsequently designated as IS 3660 ( Part 51 ) :1972 ],

IS 3660( Part II ) :1968 Determination of solvent extract and nitrogen content [subsequently designatedas IS3660(Part32) : 1968].

IS 3660( Part III): 1971 Plasticity and plasticity retention index [ subsequently withdrawn with the publicationof Part 11 and 12 of 1S 3660 in 1989 ],

IS 3660( Part IV ) :1979 Determination of colour, accelerated storage-hardening test and vulcanizationcharacteristics ( MOD test) [ subsequently designated as IS 3660 ( Part 54 ) :1979 ].

While reviewing various testmethodsfornaturrd rubber, the Committee decided to aligmthem with the correspondinginternational standards. Unification of test methods for natural and synthetic rubber has not been considerednecessary. However, in.revising test methods for natural rubber. the committee had decided to revise and splitthe standards into further parts and publish test methods for individual characteristics under natural rubber( NR ) series. For proper referencing of the original test methods and the new methods revisedhnder revision,a table showrng correspondence of the various methods of test covered in the previous 4 parts of IS 3660,namely ( Part I, II, 111and IV) with the presently split parts hiive been given in Annex A. In order to facilitatecross reference, it has been decided to retain the original discrete NR series numbers assigned to various testmethods in original IS 3660 ( Part I, 11,111and IV ) in the revised part of IS 3660.

The test method given in this revised standard will supersede the test metiod as given under NR: 9 of IS 3660(Part 51 ) :1972. This standard ( Part 51) shall be withdrawn upon its complete revision. .

In the preparation of this standard, assistance has been derived from 1S0 2393: 1994(E) ‘Rubberlest mixes— Preparation, mixing and vulcanization — Equipment and procedures’, published by the InternationalOrganization for Standardization ( 1S0 ).

In this Rvision equipment, procedure and prepwation of sample have been incorporated. In addition, modificationsnecessary to align it with latest 1S0 standard, namely, 1S0 2393:1994 (E) have also been made.

In reporting the result of a test or analysis made in accordance with this standard, if the final value, observedor calculated, is to be rounded off, it shall be done in accordance with IS 2: 1960 ‘Rules for rounding offnumerical values (revised )‘.

METHODS OF

IS 3660( Part 8 ) :1999

Indian Standard

TEST FOR NATURAL RUBBERPART 8 MIXING AND VULCANIZING OF RUBBER IN STANDARD COMPOUND

[NR:9]

(Second

1 SCOPE

This standard (Part 8) prescribes the equipment andprocedures for the preparation, mixing andvulcanization of test mixes, in a standard compound.

2 NORMA’TIVEREFERENCES

The following Indian Standards contain provisionswhich through reference in this text, constituteprovisions of this standard. At the time of publicationthe editions indicated were valid, All standards aresubject to revision, and parties to agreements”basedon this standard are encouraged to investigate thepossibility of applying the most recent editions of thestandards indicated below:

IS No. Title

3400 Methods of test for vulcanized(Part 1 ) :1987 rubber : Part 1 Tensile stress and

strain properties ( second revision)

3660 Methods of test for natural rubber:( Part 7 ) :1988 Part 7 Determination of Moony

viscosity ( NR: 8 ) (second revision)

7503 Glossary of terms used in rubberindustry

( Part 1): 1988 Definitions of basic terms ( jirstrevision )

( Part 2 ) :1988 Definitions of additives ( jirstrevision)

( Part 3 ) :1988 Definitions relating to propertiesand testing (first revision )

( Part 4 ) :1988 Definitions relating to processing(jWst-revision)

13867:1993 Rubber standard temperatures,humidities and times for condition-ing and time interval betweenvulcanization and test pieces

3 DEFIXWTIONS

-For the purposes of this standard, the definitions

Revision )

given in various parts of IS 7503 shall apply.

4 COMPOUNDING INGREDIENTS

The compounding ingredients required for the standardtest formulations shall be in accordance with standardsas specified in the appropriate rubber evaluationprocedure.

5 PREPARATION OF MATERLAM

5.1 Batch Mass

5.1.1 The.standard%atch mass for the laboratory mill,in grams, shall be four times the formulation batchmass unless otherwise stated in the appropriate rubberevaluation procedure.

5.1.2 The batch mass for the internal mixer, in grams,shall be equal to the nominal mixer capacity, in ml,multiplied by the compound density.

5.1.3 The batch mass for the miniature internal mixer,in grams, Sharibeequalto the nominal mixer capacity,in ml, multiplied by the compound density.

5.2 Weighing Tolerances

5.2.1 Rubber and carbon black shall be weighed tothe nearest 1 g, oil to the nearest 1 g or ●1 percentwhichever is more accurate, vulcanizing agents andaccelerators tothe nearest 0.02 g and zinc oxide andstearic acid to the nearest 0.1 g. All other ingredientsshall be weighed to an accuracy of *1 percent.

5.2.2 For miniature internal mixer mixes, the rubberand carbon black shall be weighed to the nearest0.1 g, oil to the nearest 0.1 g or +1 percent whicheveris more accurate, sulphur and accelerators to thenearest 0.002 g and zinc oxide and stearic acid to thenearest 0,01 g. All other ingredients shall be weighedto an accuracy of ●1 percent.

5.3 Carbon Black Conditioning

5.3.1 Unless otherwise specified, carbon black shallbe conditioned, before weighing, by heating in anoven at a temperature of 105 ● 5°C for 2 h. The black

1

IS 3660( Part 8 ): 1999

shall be placed in an open vessel of suitable dimensions 6.2 Internal Mixerso that t-hedepth of the black is no more than 10 mmduring conditioning. Theblack, conditioned as above,

6.2.1 Internal mixers maybe divided into two basic

shall be stored in a closed moisture-proof containertypes; those with tangential rotors and those with

until it is required for mixing.interlocking rotors. In the tangential type, the highshear strain and shear stress regions occur between

Alternatively, carbon black may be conditioned by the rotor tips and the chamber wall. The rotors alsoheating in an oven at 125+ 3°C for 1 h. Carbon black run at different speeds which aids the pumping andconditioned in this manner may not give the same distributive action of the mixer. In the interlockingresults as that conditioned at 105 + 5°C. type, the rotors run at the same speed, but the design

The conditioning temperature used shall be recorded o~the rotor-nogs and the interlocking action producefriction between the rotors. The high shear strain andin the test report.shear stress region occurs between the rotors.

6 MIXING EQUIPMENT6.2.2 This standard describes three types of laboratory

6.1 Mixing Mill internal- mixer, Type A 1 and Type A2 are of the

The characteristics of a standard laboratory mill aretangential type and Type B is of the interlocking type.Internal mixers other than those specifkd maybe used.

as follows:As a rule, different types of internal mixer do not give

Roll diameter ( OD ), mm 150to 155 the same properties in the final mix. Modification of

Roll length (between guides ), mm 250 to 280

Speed of front ( slow ) roll, rpm 24*1

Roll-speed ratio ( preferably) 1 :1.4

Clearance between rolls (adjustable ), mm 0.2 to 8.0

Temperature-control tolerance, “C *5(unlessotherwisespecified )

WARNING — THE MILL SHOULD BEEQUIPPEDWITH SUITABLE SAFE’IY DEVICES TO PROTECTAGAINST ACCIDENTS, IN ACCORDANCE WITHNATIONAL SAFETY REGULATIONS.

NOTES

-1 If mills of other dimensions are used, adjustmentsto batch masses and mixing cycles may be required toobtain comparable results.

2 If the roll-speed ratio is other than 1 : 1.4,modifications may be necessary to the mixing procedureto obtain comparable results.

The roll clearance shall be determined by means of twolead strips 10 * 3 mm in width, at least 50 mm long and0.25 to 0.50 mm thicker than the roll clearance to be

mixing technique may lead to comparable results. Forreferee ptnposes in particular, these adjustments shallbe defined and agreed on by the interested parties.

.WARNING — INTERNAL MIXERS SHOULD BEEQUIPPED WITHA SIJITABLEEXHAUST SYSTEMAND SUITABLE SAFETY DEVICES TO PREVENTACCIDENTS, IN ACCORDANCE WITHNATIONALSAFETY REGULA~ONS.

6.2.3 The dimensions of the three types of laboratoryinternal mixer are shown in Table 1.

6.2.4 All internal mixers shall befitted with a systemto measure and indicate andkr record the temperatureof the mix during the mixing operation to within 1“C.

NOTE — The actual mix temperature usually exceedsthe indicated temperatures by an amount dependenton the mixing conditions Used and the location of the

measuring probe.

6.2.5 All internal mixers shall befitted with a timer toindicate the mixing time to +5s.

6.2.6 All internal mixers shall be fitted with a systemto indicate or record electrical power demand ortorque.

measured. The lead strips shall be inserted, one at each 6.2.7 All internal mixers shall befitted with an eff’cientend of the rolls, approximately 25 mm from the guides,while a piece of compounded rubber with a Mooney heating and cooling system to control the surface

viscosity, determined in accordance with IS 3660 temperature of-the rotors and the mixing-chamber( Part 7-), greater than 50 ml ( 1 + 4 ) at 100”C and walls.measuring approximately 75 mm x 75 mm x 6 mm ispassing through the centre portion of the nip. The rollsshall be at the temperature specified for mixing. Afterpassing between the rolls, the thickness of the lead stripsshall be measured at three separate positions with amicrometer to an accuracy of *0.O 1mm. The toleranceon roll clsarance shall be *10 percent or 0.05 mm,wh]chever is the larger.

The mill rolls shall have provision for circulation of

heating or cooling media.

6.2.8 All internal mixers shall be closed during themixing cyclewith a ram to contain the mix in the mixingchamber.

6.2.9 When clearances exceed the values given inTable 1, an overhauls deemed necessary since mixingquality may be adversely affected. This increase inrotor clearance may be equated to an approximately10 percent increase in nominal mixer capacity.

.L

IS 3660( Part 8 ): 1999

Table 1 Types of Laboratory Internal lWxer

( Clauses 6.2.3 and6.2.9 )

S1

No.

(1)

. i)

ii)

iii)

iv)

v)

vi)

Mixer Characteristics

(2)

Nominal mixing capacity, ml

Rotor speed (fast rotor) (rpm)

Rotor friction ratio

“Rotor clearance (mm) :

new

worn

Power (kW/rpm)

Ram pressure on the compound ( MPa )

Type Al Type A2

(Tangential, that ia, Non-interlocking Rotors)

‘(3) (4 j

1 170 * 40 2000

77* 10 40 * 10

11O*1O

1.125:1 1.2:1

2,38 * 0.13 4.0 * 1.0

3,70

0.13 (fast rotor)

0.5 to 0.8 0.5 to 0.8

Type B

(lnterlocldng Rotors)

(5)

1’000

55

1:1

2.45 to 2.50

5,0

0.227

0.3+————— (or as specified in the appropriate standard) ~

NOTE — Type Al is commonly used.

6.2.10 A mill as described in-6.1 shall be providedfor consolidating mixes.

6.3 Nliniaturelntemal Mixer

The dimensions of the pn%i miniature internal mixerare as follows:

Type Non-interlocking rotors

Nominal mixer capacity, ml 64*1

Rotor speed (rPm) 6~~ ( fast rotor)

Rotor friction ratio 1.5:1

NOTE — The miniature internal mixer can only providesufficient compound for curemeter testing and for avulcanized sheet measuring 150 mm x 75 mm x 2 mmapproximately.

6.3.1 The miniature internal mixer shall be fitted witha system to measure and indicate or record thetemperature of the mix during the mixing operation towithin l“C.

NOTE — The actual mix temperature usually exceedsthe indicated temperature by an amount dependent onthe mixing conditions used.

6.3.2 A timer shall be used to indicate the mixing timeto *5 s.

6.3.3 The miniature internal mixer shall befitted witha system to indicate or record electrical power demandor torque.

6.3.4 The miniature internal mixer shall be fitted withan eftlcient heating and cooling system to control the

temperature of the mixing-chamber walls.

6.3.5 The miniature internal mixer shall beclogeddo.ringthe mixing cycle with a ram or lever to contain the mixin the mi~ng chamber.

7 MDKINGPROCEDURES

7.1 Mill Mixing Procedure

7.1.1 Batches shall be mixed with the rubber bandedon the front roll, unless otherwise specified in theappropriate standard.

7.1.2 The temperature at the middle of the surface ofthe rolls shall be measured during the mixing procedure,either continuously on a recorder, or with-a manualdevice ( having an accuracy of+ 1°C or better )frequently enough to be sure that the desiredtemperature is being maintained. The batch mayberemoved momentarily from the mill to enable thesurface temperature of the front roll to be measured.

7.1.3 Whenever 3/4 cuts are specified, the batch shallbe cut 3/4 of the distance across the roll and the knifeheld in this position until the bank just disappears.

7.1.4 The compounding ingredients shallbt-introducedalong the whole roll length. The batch shall not becut while free powder is evident on the rolling-bankor on the milling surface. Compounding ingredientsfalling through the nip shall be carefully collected andreturned to the batch.

7.1.5 Whenever 314 cuts each way are specified,successive 3/4 cuts shall be made from alternatedirections, allowing 20 s between successive cutsunless otherwise specified in the appropriate standard.

3

IS 3660 (Part8 ): 1999

7.1.6 The mass of the mixed batch shall not differ fromthe specified mass of rubber and all other ingredientsby more than +0.5 percent or -1.5 percent.

7.1.7 The mixed batch shall be cooled to laboratorytemperature on a flat, clean, dry, metal surface. Thecooled batches shall be wrapped in aluminiurn foil orother suitable material to prevent contamination byother compounds. Alternatively, the mixed batch maybe cooled in water, but different results may beobtained.

7.1.8 A report shall be prepared for each batch mixed,indicating:

a)

b)

c)

d)

e)

the friction ratio ( roll-speed ratio) and rollspeeds;

the distance between the guides;

the maximum and minimum roll tempetitums;

the temperature used for conditioning thecarbon black; and

the method of cooling the mixed batch.

7.2 Internal-Mixer Mixing Procedure

7.2.1 The mixing techniques used shall be as statedin the appropriate standard for the rubber concerned.If no standard is available the procedure shall be asagreed between the interested parties.

7.2.2 For each batch mixed, the internal-mixerconditions shall be the same during the preparationof a series of identical mixes. At the beginning of eachseries of test mixes, a machine-conditioning batchshall be mixed using the same formulation as in themixes under test. This also acts as a machine-cleaningbatch. The machine shall be allowed to cool down toa specified temperature between theend of one testbatch and the start of the next. Temperature-controlconditions for the machine shall not be altered duringthe mixing of a series of test batches,

NOTE — For the best results, all comparative test mixes

should be mixed in the same internal mixer.

7.2.3 Material to be mixed shall be reduced in size topieces that can be fed easily and.rapidly to the internalmixer.

7.2.4 The discharged batch shall be consolidated ona standardlaboratory mill in the manner and allowedto cool one of the standard temperatures specified inIS -13867 at 27* 2°C on a flat, clean, dry, metalsurface.

7.2.5 The mass of the mixed batch shall not differfrom the total mass of the ingredients by more than~0.5 percentor –1.5 percent. Some rubbers andcompounding ingredients are known to contain small

amounts of volatiles which may be lost at thetemperatures of mixing, with the result that the abovelimit may not be met. In such cases, the differenceshall be reported. This paragraph also applies to7.2.8and7.3.4.

7.2.6 Rest the batch for at least 30. rein, or until itreaches standard temperature, before proceeding withthe final mixing stage. The maximum time betweenmixing stages shall be 24 h.

7.2.7 If-the final stage mix is to be prepared in theinternal mixer, cut the batch from stage 1 into stripsfor easier feeding and add the remaining ingredientsin accordance with the instructions in the relevantstandard. If the final stage is to be prepared on themill, add the ingredients in accordance with theinstmctions in the relevant standard. Unless othenvisestated, the batch size shall be reduced to four timesthe formulation batch mass.

7.2.8 When the internal mixer is used for the finalstage, the discharged batch shall be consolidated asspecified in the appropriate standard on a mill asspecified in 6.1. The final mass of the mixed batchshall not differ from the total mass of the ingredientsby more than+ 0.5 percent or -1.5 percent.

7.2.9 Unless otherwise stated in the appropriatestandard, after removal of a curemeter test piece and(if required) a compound viscosity test piece, passthe batch four times through the mill at a rolltemperature of 50 * 5“C. Fold the batch lengthwiseafter each pass, and pass always in the same directionto obtain a grain effect. The mill opening shall besuch as to give a sheet between 2.1 mm and. 2.5 mmthick after shrinkage, suitable for the preparation ofvulcanized sheets for dumb-bell test pieces. Ifvulcanized discs for ring test pieces are to be prepared,open the mill so that a sheet between 4.1 mm and4.5 mm thick is produced.

7.2.10 A report shall be prepared for each batch mixed,indicating:

a)

b)

c)

d)

e)

o

!3)

the starting temperature,

the mixing time,

the rotor speed,

the ram pressure,

the temperature of the mix at discharge,

the type of mixer used,

any allowable mass loss outside the limitsgiven in 7.2.5 and 7.2.8, and

h) the temperature used for conditioning thecarbon black.

4

For mixes where both initial and final stages werecarried out in the internal mixer, a report shall be issuedfor each of the two stages.

7.3 Miniature Internal Mixer Mixing Procedure

7.3.1 Maintain the mixer head temperature for at least5 miribefore mixing.

7.3.2 The rotor speed shall be ( 1.0~;“’rev/s, that is,60~; rev/rein), urdess otherwise specitled. It shall befrequently checked ifa variable-speed model is used.

7.3.3 The mixi~ technique used shall be as statedin the appropriate standard for the rubber concerned.If no standard is available, the procedure shall be asagreed between the interested parties.

7.3.4 Immediately pass the discharged mix from themixer twice through a standard mill maintained at thespecifkd temperature, p~ferably with the rolls runningat the same speed and with a roll separation of0.5 mm, then twice at a separation of 3 mm in order todissipate the heat, and weigh. The mass of the mixedbatch shall not differ from the total mass of all thematerials by more than 0.5 percent. Some rubbers andcompounding ingredients are known to contain smallamounts of volatiles which may be lost at thetemperatures of mixing, with the result that the abovelimit may not be met. In such cases, the differencesshall be reported.

8 PREPARATION OF STANDARD VULCANIZEDSHEETS FOR-DUMB-BELL TEST PIECES

8.1 Conditioning of Batches

8.1.1 Batches shall be conditioned for between 2 hand 24 h at one of the standard temperatures specifkdin IS 13867-preferably in a closed container to preventabsorption of moisture from the air or in a room inwhich the relative humidity is controlled at 65 +-5percent.

8.1.2 The sheeted batch shall be placed on a flat,clean, dry, metal surface, and the blanks shall be cutto the corresponding dimensions of the mould cavity.The direction of the grain of the rubber shall be markedon each piece. The blanks shall be within+ 3 to Og ofthe mass given in Table 2 when they are vulcanizedin the mould specified in 8.2.2. Remilling shall beavoided if possible. Where remilling is necessary, theprocedure given in 7.2.9 shall be used.

8.2 Vulcanization Equipment

8.2.1 Press

8.2.1.1 The press shall be capable of exerting a pressureof not less than 3.5 MPa on the cavity areas of themould during the entire period of vulcanization, Itshall have heated platens of sufficient size that no

IS 3660( Part 8 ): 1999

Table 2 Mass of Blank

( Clause 8.1.2)

Densitymg/m3

0.94

0.96

0.98

1.00

1.02

1.04

1.06

1.08

1.10

1.12

1.14

1.16

1.18

1.20

1.22

1.24

1.26

1.28

1.30

Mass

6

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

portion of the rubber will be nearer than 30 mm to theedge of the platen during vulcanization. The platensshould preferably be made of rolled steel, machinedfor electric, steam orthermofluid heating. When steamheating is used, each platen shall be individuallysupplied. A self bleeding trap or small vent shall beplaced in the exit steam line to allow steam to flowcontinuously through the platens. If chamber typeplatens are used, the steam outlet shall be placedslightly below the steam chamber so that good drainageis ensured.

/

8.2.1.2 Conduction of heat from the hot platens tothe press cross-head shall be reduced as much aspracticable by means of a steel grid between them orby other means. Platens shall be suitably shieldedfrom draughts.

8.2.1.3 The pressing surfaces of the platens shall beplane parallel to within 0.25 mm/m when the platensare at 150”Cand closed under fidl pressure with a gridof soft solder or lead between them.

8.2.1.4 With either type of platen, the temperatureover.the mould area shall be uniform. The maximumdeviation from the temperature at the centre of theplaten shall not exceed *0.5”C. Between adjacentplatens, the temperature difference between corres-ponding points on the two platens shall not exceed

5

IS 3660( Part 8 ): 1999

l°C and the mean difference in platen temperaturesshall not exceed O.5°C.

8.2.2 h40uld

82.2.1 The mould shall have cavity sections ofsufllcient size to allow the required number of dumb-bells, as specified in IS 3400 ( Part 1 ) to be cut. Asuitable mould is shown in Fig. 1, but a preferredalternative is a mould with rectangular cavities ofapproximate dimensions 150 mm x 145 mm x 2 mm.This mould enables the milled sheet to be positionedunequivocally with respect to the direction of thegrain.

8.2.2.2 The cavities to within 6 mm of the edges shallbe between 1.9 mm and 2.0 mm deep. The comers ofthe cavities may be rounded with a radius not greaterthan 6 mm.

8.2.2.3 The moulding surfaces shall k clean and highlypolished. Moulds constructed of hardened steel arepreferred, but chromium-plated mild steel and stainlesssteel are also acceptable. The cover of the mould shallbe a flat plate at least 10 mm in thickness and preferablyhinged to the cavity section to minimize scratchingof the mould surfaces. Instead of a separate mouldand cover, the cavities may be cut directly rnto theplaten of the press.

8.2.2.4 Normally, a mould lubricant shall not be usedon the motdd surfaces. If a mould lubricant is required,

RECESS FOR lDEN’Tl-TFCATION TAG

only a type which does not affect the vulcanized slabShiillbe used. The excess lubricant shall beremrwedbyvulcanizing and discarding at least one set of sheets.A silicone-type lubricant or mild soap solution hasbeen found satisfactory, but silicone lubricant shallnot be used when moulding silicone rubbers.

8.3 Vulcanization Procedure

8.3.1 Bring the mould to within *0.5°C of thevulcanization temperature in the closed press and holdat this temperature for at least 20 min before theunvulcanized pieces are inserted. Veri&the temperatureof the mould by means of a thermocouple or othersuik~blytemperature-measuring device inserted in oneof the overflow grooves and in intimate contact withthe mould.

8.3.2 Open the press, insert the unvulcanized piecesin the mould and close the press in the minimum timepossible. When the mould is removed from the pressto insert the pieces, take any precautions necessaryto prevent excessive cooling of the mould by contactwith cool metal surfaces m by exposure to air draughts.

8.3.3 The time of vulcanization shall be consideredto be the period between the instant the pressure isapplied fully and the instant the pressure is released,Hold the mould under a minimum pressure of 3.5 MPaon the cavity areas during vulcanization. As soon asthe press is opened, remove the vulcanized sheets

t-125 12.5

/1 ~ - ! ! .29 rnin

k.i. 14.5J

All dimensions in millimetres.

FIG. 1 DESIGNFORFOUR-CAVITYMOULD

6

from the mould and cool in water ( room temperatureor lower ) or on a metal surface ( for items used forelectrical measurements ) for 10 to 15 min. Then wipedry the sheets cooled in water and reserve fortesting. In both of the preceding operations, take careto prevent undue stretching or deformation.Alternatively, the moulds can be removed from thepress and cooled in water before the vulcanized sheetsare removed.

NOTE — This alternative procedure may give differentresults,

8.3.4 Store vulcanizates at one of the standardtemperatures specified in IS 13867. Separatevulcanizates with aluminium foil or other suitablematerial to prevent contamination during storage.

8.3.5 For all test purposes, the minimum time betweenvulcanizatmn and testing shall be 16 h.

8.3.6 The maximum time between vulcanization andtestrng shall be 96 hand, for evaluations intended tobe comparable, the tests, as far as possible, shall becarried out after the same time interval.

NOTE — Longer periods between vulcanization andtesting may be used by agreement between the supplierand the purchaser.

9 PREPARATION C)F ST~ARD VULCANIZEDDISCS FOR RING TEST -PIECES

9.1 Conditioning of Batches

9.1.1 Condition batches as specified in 8.1.1.

9.1.2 Place the sheeted batch on a flat, clean, dry,metal surface. Stamp circular pieces 63 to 64 mm in

IS 3660( Part 8 ): ‘1999

diameter from the sheet so that they fit easily intothe cylindrical mould cavities of the mould shown inFig. 2.

Remilling shall be avoided impossible Where remillingis necessary, the procedure given in 7.2.9 shall %eused.

9.2 Vulcanization Equipment

9.2.1 Press

As specified in 8.2.1.

9.2.2 A40uld

9.2.2.1 The mould should have cavity sections similarin dimensions to those shown in Fig. 2, which givesdiscs 65 mm in diameter and 4 mm thick. The mouldconsists of a lid and a cavity section hinged to eachother. The hinges have oblong holes so as to holdthe pressing surfaces in a plane parallel position,thereby preventing distortion of the lid should thepress be closed when loaded with thick discs.

9.2.2.2 The cavity section contains several groupsof cylindrical cavities for the moulding of threeinterconnected discs. Close to each group of.cavitiesis a 10-mm wide recess which can be used for theidentification of individual compounds. For technicalreasons, the depth of the recess is less than that ofthe disc cavities. For identification purposes, anembossed aluminium strip is placed in the recess sothat, on moulding, an identity tag is left attached tothe group of three discs.

9.2.2.3 The number of cavities depends on the sizeof the platens of the curing press available. Hard

RECESS FORIDENTIFICATION1~

I582

. A.. — . ..-. I AC -i o

I au I 9.2

I I Iwq

—, —LLu.-: - ret-l_ w,- MJ_L

YLwJAll dimensions in millimetres.

FIG. 2 MOULDFORVULCANIZINGDISCSFORRINGTESTPIECES

7

.-

1S 3660( Part 8 ): 1999

aluminium alloys have proved to be suitable for the 0.05 mm. The corners of the cavities maybe roundedmanufacture of the mould shown in Fig. 2. Thinner with a radius not greater than 0.5 mm. The mouldingmoulds ( for example: lid 4 mm, cavity section 8 mm ) surface shall be clean and highly polished.can be made from steel, but hinges required for thinner 9.3 Vulcanization Proceduremoulds are more difilcull to make.

As specified under 8.3.

9.2.2.4 The cavities shall be uniform in depth to within

ANNEX A

( Foreword)

TABLESHOWING CORRESPONDENCE OF THEVARIOUSMETHODS OF TEST COVEREDIN THE ORIGINAL IS 3660 (PART 1 ) :1972 (NOW DESIGNATED AS PART 51 ),

IS 3660( PART 2 ) :1968 ( NOW DESIGNATED AS PART 52 ), IS 3660 ( PART 3 ) :1971( SINCE WITHDRAWN ON ITS COMPLETE REVISION) ,AND IS 3660 (PART 4 ) :1979

(NOW DESIGNATED AS PA12T54) WITH THE NEW REVISED STANDARDS

Test Method

(1)

NR Series

Determination of dirt

Determination of volatilematter

Determination of ash

Determination of totalcopper

Determination of manga-nese

Determination of iron

IS No.

(2)

3660:1972

3660:1972

3660:1972

3660:1972

3660:1972

3660:1972

OriginalPart (Series)

(3)

Partl(NR:l)

Partl(NR:2)

Partl(NR:3)

Partl(NR:4)

Partl(NR:5)

Partl(NR:6)

Determination of rubber 3660:1972 Part 1 ( NR: 7 )hydrocarbon

Determination of 3660:1972 Partl(NR:8)viscosity by shearingdisk viscometer

Mixing and vulcanizing 3660:1972 Part 1 ( NR: 9 )

Determination of solvent 3660:1968 Part 2 ( NR: 10)extract

IS No. New Parts Remarks/

(4)

3660 (Part 1): 1999

3660( Part2) :1985

3660( Part3 ):1988

3660 (Part4) :1988

3660 ( Part5 ): 1989

Deleted since thistest is no longerbeing done

3660 ( Part6 ) :1988

3660( Part7) :1988

3660 ( Part 8 ) :1999

3660( Part9): 1989

Determination of nitrogen 3660:1%8 PaIt2(NR:ll) 3660( Part10)

Series Rea@rmed

(5) (6)

(NR:l) –

( NR: 2 ) December 1995

(NR: 3 ) January 1995

(NR: 4) JanuaIy1995

(NR: 5 ) January 1995

(NR:7) January 1995

(NR: 8) January1995

(NR:9) –

(NR: 10) January 1995

( NR: 11) Covered by theDoe : PCD 14( 1600)

8

IS 3660 (Part 8 ): 1999

Test Method IS No. Original IS No. New Parts Remarks/Parl (Series) Series Rea@rmed

(1) (2) (3) (4) (5) (6)

Determination of 3660:1971 Part3 (NR: 12) 3660( .Partll): 1989 (NR: 12) January 1995plasticity

Determination of 3660:1972 Part3 (NR: 13) 3660( Part 12) :1989 (NR: 13) January 1995plasticity retention index(PRI)

Determination of colour 3660:1979 Part 4 ( NR: 14) 3660( Part 13 ): 1997 ( NR: 14) —

Determination of storage 3660:1979 Part 4 ( NR: 15) 3660( Part 14 ) ( NR: 15) Revision still tohardening test be published

Determination of vnlcani- 3660:1979 Part 4 ( NR: 16) 3660( Part 15 ) (NR: 16) dozation characteristics(MOD test)

Method of preparation 3660:1972 Part l(Clause3) 5599:1999of test samples

NOTES

1 Original IS 3660 ( Part I ) :1972 now re-designated as IS 3660 ( Part 51 ) :1972.

2 Original IS 3660 ( Part 11) :1968 now re-designated as IS 3660 ( Part 52 ) :1968.

3 Subsequent to its complete revision, IS 3660 ( Part 111) : 1971 has since been withdrawn.

4 Original IS 3660 ( Part IV ) :1979 now re-designated as IS 3660 ( Part 54 ) :1979,

\

9

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Amend No. Date of Issue Text Affected

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