6.RUBBER COMPOUNDING TECHNOLOGY-FINAL.ppt

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RUBBER COMPOUNDING

TECHNOLOGY

SUDHA.P SUDHA.P DEPUTY DIRECTOR(RIDT) DEPUTY DIRECTOR(RIDT)

RUBBER TRAINING INSTITUTE

DEPARTMENT OF TRAINING DEPARTMENT OF TRAINING RUBBER BOARD RUBBER BOARD KOTTAYAM-686 009 KOTTAYAM-686 009 [email protected] [email protected] Mob: 94964 13731 Mob: 94964 13731

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RUBBER

RUBBER COMPOUNDINGCOMPOUNDING

COMPOUND

It is a homogenous mixture of ingredients used in a

particular product manufacture such that the properties

of most of the ingredients are unchanged in the final

product whereby providing a defined set of

mechanical properties.

COMPOUNDING

It is the science of selecting and combining elastomers

and additives to obtain physical and chemical

properties for a finished product.

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RUBBER COMPOUNDING

OBJECTIVE

1.

1. To secure To secure certain properties in the finished product to certain properties in the finished product to satisfy the service requirements.

satisfy the service requirements.

2.

2. To attain processing characteristics necessary for efficient To attain processing characteristics necessary for efficient

utilization of available equipment.

3.

3. To achieve desirable properties and processability at the To achieve desirable properties and processability at the

lowest cost.

The most important factor in compounding is to secure an

acceptable balance among demands arising from the above

three criteria.

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MAJOR OBJECTIVES OF COMPOUND

DEVELOPMENT

PROCESS REQUIREMENT

 Proper mixing (Incorporation, dispersion, distribution and Proper mixing (Incorporation, dispersion, distribution and

plasticization) plasticization)

 Viscosity/process safety (ML1+4, MS)Viscosity/process safety (ML1+4, MS)  Stickiness and tackinessStickiness and tackiness

 Shaping (Calendering, Extrusion, Assembling and Moulding)Shaping (Calendering, Extrusion, Assembling and Moulding)

COMPOUND PROPERTY REQUIREMENT

 Hardness Hardness

 Stress-Strain properties (TS, EB, M-100, M-300, tear)Stress-Strain properties (TS, EB, M-100, M-300, tear)  Abrasion resistanceAbrasion resistance

 Hysteresis & set propertiesHysteresis & set properties

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MAJOR OBJECTIVES OF COMPOUND

DEVELOPMENT

RESISTANCE TO DEGRADATIONRESISTANCE TO DEGRADATION  Heat, Oxygen, OzoneHeat, Oxygen, Ozone

 FlameFlame  LiquidsLiquids  LightLight

MISCELLANEOUS PROPERTY REQUIREMENTSMISCELLANEOUS PROPERTY REQUIREMENTS  Low temperature flexibilityLow temperature flexibility

 Electrical propertiesElectrical properties  PermeabilityPermeability

 Contact with food stuff and drugsContact with food stuff and drugs  Bonding to metal & textilesBonding to metal & textiles

 SwellingSwelling

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CLASSIFICATION OF COMPOUNDING

INGREDIENTS

1. 1. ElastomersElastomers 2.

2. Vulcanizing Agents (curatives)Vulcanizing Agents (curatives) 3.

3. AcceleratorsAccelerators 4.

4. Activators and RetardersActivators and Retarders 5.

5. Antidegradants (Anti-oxidants, Antiozonants, Protective Antidegradants (Anti-oxidants, Antiozonants, Protective

waxes )

6.

6. Processing aids (Peptisers, Lubricants, Release Agents)Processing aids (Peptisers, Lubricants, Release Agents) 7.

7. Fillers (carbon black, non-black materials)Fillers (carbon black, non-black materials) 8.

8. Plasticizers, Softeners and TackifiersPlasticizers, Softeners and Tackifiers 9.

9. Colour pigmentsColour pigments 10.

10. Special Purpose Materials (Blowing Agents, Deodorants, Special Purpose Materials (Blowing Agents, Deodorants,

etc.)

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COMPOUND DESIGN

DESIGN REQUIREMENTS

 SERVICE REQUIREMENTS/VULCANISATE PROPERTIESSERVICE REQUIREMENTS/VULCANISATE PROPERTIES  PROCESSABILITYPROCESSABILITY

 ECONOMICSECONOMICS

DESIGN BASED ON

 CUSTOMER SPECIFICATION/REQUIREMENTSCUSTOMER SPECIFICATION/REQUIREMENTS  COMPETITOR'S SAMPLECOMPETITOR'S SAMPLE

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POLYMER SELECTION

CRITERIA

 CostCost

 Ease of mixingEase of mixing

 Strength requirementsStrength requirements

 Modulus or stiffness requirementModulus or stiffness requirement  Abrasion resistance requirementAbrasion resistance requirement  Elongation requirementElongation requirement

 Oil resistance requirementOil resistance requirement

 Low temperature requirementLow temperature requirement  Fatigue requirementFatigue requirement

 TackTack

 Set of stress relaxationSet of stress relaxation  Service temperatureService temperature

 Dynamic properties (hysteresis, damping resistance)Dynamic properties (hysteresis, damping resistance)  FlammabilityFlammability

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POLYMER SELECTION

 SHOULD HAVE THOROUGH KNOWLEDGE ABOUT POLYMER SHOULD HAVE THOROUGH KNOWLEDGE ABOUT POLYMER

PROPERTIES

 REFER STANDARD SELECTION CHARTS/COMPARATIVE CHARTSREFER STANDARD SELECTION CHARTS/COMPARATIVE CHARTS  BLENDS OF POLYMERSBLENDS OF POLYMERS

 PROCESSABILITY FACTOR-suitability for the processes and methods PROCESSABILITY FACTOR-suitability for the processes and methods

adopted

 COST FACTORCOST FACTOR

 AVAILABILITY OF DATA ON POLYMER GRADES, PROPERTIES, AVAILABILITY OF DATA ON POLYMER GRADES, PROPERTIES,

START UP FORMULATIONS ETC.

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VULCANIZING AGENTS

TYPE

TYPE COMMON USECOMMON USE

Sulphur or Sulphur bearing

materials

materials Natural Rubber, Isoprene, SBR, Butyl, Poly Butadiene, EPDM, Natural Rubber, Isoprene, SBR, Butyl, Poly Butadiene, EPDM, Nitrile

Nitrile

Organic Peroxides

Organic Peroxides Urethane, Silicone, Chlorinated Urethane, Silicone, Chlorinated Polyethylene, PVC/Nitrile

Polyethylene, PVC/Nitrile

Metallic Oxide

Metallic Oxide Polychloroprene, Chlorosulphonated Polychloroprene, Chlorosulphonated Polyethylene, Polysulphide

Polyethylene, Polysulphide

Organic Amines

Organic Amines Acrylic, Fluorocarbon, Acrylic, Fluorocarbon, Epichlorohydrin

Epichlorohydrin

Phenolic Resins

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CURING SYSTEM

Selection of curing system is based on:Selection of curing system is based on:

 Base polymerBase polymer

 Processing conditionsProcessing conditions  Curing conditionsCuring conditions  Service requirementService requirement

Base polymerBase polymer

 Saturated rubber – peroxide e.g. EPR with DCPSaturated rubber – peroxide e.g. EPR with DCP

 Unsaturated rubber-peroxide, sulphur/accelerator & resins, e.g. EPDM Unsaturated rubber-peroxide, sulphur/accelerator & resins, e.g. EPDM

with DCP, NR with sulphur accelerator, IIR with Resin

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ACCELERATORS

An accelerator is usually a complex organic chemical which takes part in the An accelerator is usually a complex organic chemical which takes part in the

vulcanization, thereby reducing the vulcanization time considerably- Organic

amines & its derivatives . It also improves the properties. Its action may be:

slow- eg. Guanidines

slow- eg. Guanidines, , Diphenyl guanidine (DPG)Diphenyl guanidine (DPG)

Di ortho tolyl guanidine(DOTGDi ortho tolyl guanidine(DOTG) )

medium

medium- eg. Thiazoles, - eg. Thiazoles, Mercapto benzo thiazole (MBT)Mercapto benzo thiazole (MBT) Di benzthiazyl di sulphide) (MBTS)

Di benzthiazyl di sulphide) (MBTS)

fast (

ultra)-fast ( ultra)- eg. Thiurams, eg. Thiurams,Tetramethyl thiuram monosulphide (TMTM)Tetramethyl thiuram monosulphide (TMTM)

Tetramethyl thiuram di sulphide (TMT)Tetramethyl thiuram di sulphide (TMT)

Dithiocarbamates, Dithiocarbamates, Zinc diethyl dithiocarbamate (ZDC)Zinc diethyl dithiocarbamate (ZDC)

Zinc dibutyl dithiocarbomate(ZDBC)Zinc dibutyl dithiocarbomate(ZDBC) Delayed-action fast- eg. Sulfenamides

Delayed-action fast- eg. Sulfenamides

Cyclohexyl benzthiazyl sulfenamide (CBS) Cyclohexyl benzthiazyl sulfenamide (CBS) Dicyclohexyl benzthiazyl sulfenamide (DCBS) Dicyclohexyl benzthiazyl sulfenamide (DCBS) Morpholino thio benzthiazylsulfenamide (MOR) Morpholino thio benzthiazylsulfenamide (MOR) Tertiary butyl benzthiazyl sulfenamide (TBBS) Tertiary butyl benzthiazyl sulfenamide (TBBS)

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CURING SYSTEM (Contd..)

Accelerator Activator

 ZnO and Stearic acid for sulphur cure systemZnO and Stearic acid for sulphur cure system  TAC for peroxide cure systemTAC for peroxide cure system

Processing condition

 Type of processing equipment usedType of processing equipment used

 Temperature build up during processingTemperature build up during processing  Extent of rework usageExtent of rework usage

 Rheological property requirementRheological property requirement

Curing conditions

 Type of the productType of the product

 Method of curing employedMethod of curing employed  Temperature of curingTemperature of curing

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CURING SYSTEM (Contd..)

Service RequirementsService Requirements

 Service temperatureService temperature  Duration of exposure Duration of exposure

 Mechanical property requirement.Mechanical property requirement.  Dynamic property requirementDynamic property requirement

 Ageing behaviour and permanent set requirements.Ageing behaviour and permanent set requirements.  Special property requirement.Special property requirement.

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FILLERS

•

Fillers are materials used to extent the range of physical

properties, to reduce compound cost, modify the

processing properties and to influence the chemical

resistance of the compound.

The effect of a filler on rubber depends

on-•

structure

•

particle size

•

surface area

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FILLERS

Reinforcing Type

Reinforcing Type Carbon Black (listed in Carbon Black (listed in order of increasing order of increasing particle size) particle size) N220 (ISAF) N220 (ISAF) N330(HAF) N330(HAF) N550 (FEF) N550 (FEF) N762 (SRF-LM) N762 (SRF-LM) N990 (MT) N990 (MT) Non-black

Non-black SilicaSilica

Zinc Oxide Zinc Oxide Magnesium Carbonate Magnesium Carbonate Aluminium Silicate Aluminium Silicate Sodium Aluminosilicate Sodium Aluminosilicate Magnesium Silicate Magnesium Silicate Extending Type

Extending Type Calcium CarbonateCalcium Carbonate Barium Sulfate

Barium Sulfate

Aluminium Trihydrate

Talc and Soapstone

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• reinforcing carbon blacks reinforcing carbon blacks

• non- reinforcing carbon blacksnon- reinforcing carbon blacks • reinforcing non- blackreinforcing non- black

• semi reinforcing non- blacksemi reinforcing non- black • non- reinforcing non- blacknon- reinforcing non- black

• Reinforcing carbon blacksReinforcing carbon blacks

 Furnace black Furnace black

 SAF – Super Abrasion FurnaceSAF – Super Abrasion Furnace

 ISAF – Intermediate Super Abrasion FurnaceISAF – Intermediate Super Abrasion Furnace  CFCF - Conductive Furnace- Conductive Furnace

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 HAFHAF - - High Abrasion Furnace (Low High Abrasion Furnace (Low

structure and high structure)

 FFFF -- Fine FurnaceFine Furnace

 FEFFEF-- Fine Extrusion FurnaceFine Extrusion Furnace

 GPFGPF-- General Purpose FurnaceGeneral Purpose Furnace

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 Thermal BlackThermal Black

MT - Medium Thermal MT - Medium Thermal

• Channel black Channel black

• EPCEPC Easy Processing ChannelEasy Processing Channel • Reinforcing Non- blackReinforcing Non- black

Precipitated silica and fumed silica Precipitated silica and fumed silica

• Semi Reinforcing Non-blackSemi Reinforcing Non-black

aluminium and calcium silicates aluminium and calcium silicates

high styrene resins high styrene resins

phenolic resins phenolic resins

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Fillers

Selection is based on Selection is based on • ReinforcementReinforcement • CostCost

• Processing requirementProcessing requirement • Colour requirementColour requirement

• Service requirementService requirement

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Compound Designing – Hardness

Polymer Hardness

Polymer Hardness phr required for 1 unit phr required for 1 unit increase in increase in Hardness Hardness NR NR SBRSBR CRCR NBRNBR 37-40 37-40 39-4139-41 41-4341-43 42-4442-44 2 2 1.61.6 1.51.5 Ppt. SilicaPpt. Silica 3

3 3.33.3 2.22.2 Calcium silicateCalcium silicate 5

5 4.14.1 4.54.5 Hard clayHard clay 7.9

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Compound Designing – Hardness

Contd.Contd.

NR

NR SBRSBR IIRIIR CRCR PBR PBR NBRNBR EPDMEPDM BlackBlack ASTM ASTM

Dsgn Dsgn DBPDBP 1.5 1.5 1.81.8 1.31.3 1.21.2 2.22.2 1.71.7 2.42.4 SAFSAF N110N110 113113 1.7 1.7 2.02.0 1.51.5 1.31.3 2.52.5 1.91.9 2.72.7 ISAFISAF N220N220 114114 1.9 1.9 2.32.3 1.71.7 1.51.5 2.82.8 2.12.1 3.03.0 HAFHAF N330N330 102102 2.3 2.3 2.82.8 2.12.1 1.81.8 3.43.4 2.62.6 3.73.7 FEFFEF N550N550 119119 2.5 2.5 3.13.1 2.32.3 2.02.0 3.83.8 2.92.9 4.14.1 GPFGPF N660N660 9090 2.8 2.8 3.43.4 2.52.5 2.22.2 4.24.2 3.23.2 4.54.5 SRFSRF N774N774 7070 2.1 2.1 2.62.6 1.91.9 1.71.7 3.23.2 2.42.4 3.43.4 HAF- HAF-LS LS N326N326 7272

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SOFTENERS



Processing aids

A softener is an ingredient that :

1.

1. speeds up the rate of polymer breakdown

speeds up the rate of polymer breakdown

2.

2. helps to disperse the other compounding

helps to disperse the other compounding

ingredients

3.

3. helps to reduce nerve within the compound

helps to reduce nerve within the compound

4

4 can impart building tack

can impart building tack

5.

5. improves the processing properties and

improves the processing properties and

modify the final

compound properties

6.

6. adjusts the compound cost and reduce power

adjusts the compound cost and reduce power

consumption during processing

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 Mineral petroleum oilsMineral petroleum oils

 They are available from petroleum industry.They are available from petroleum industry.

paraffinic paraffinic naphthenic naphthenic aromatic aromatic  Plasticizers Plasticizers

They are of the synthetic type , used where mineral oils are not They are of the synthetic type , used where mineral oils are not

compatible with the rubber compatible with the rubber

dibutyl phthalate -DBP dibutyl phthalate -DBP

di isobutyl phthalate-DIB di isobutyl phthalate-DIB di octyl phthalate - DOP di octyl phthalate - DOP *

*FacticesFactices

They are vulcanized vegetable oils used as plasticizers to get They are vulcanized vegetable oils used as plasticizers to get smooth compound in extrusion (brown) & to reduce abrasion smooth compound in extrusion (brown) & to reduce abrasion

resistance in products like erasers (white) resistance in products like erasers (white)

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PROCESSING AIDS

COMPOSITION

COMPOSITION EXAMPLEEXAMPLE FUNCTIONFUNCTION

Activated

Dithio-bisbenzaldihide

bisbenzaldihide Pepton 44Pepton 44 Peptizer for NRPeptizer for NR

Xylyl Mercaptans

Xylyl Mercaptans RPA-3RPA-3 Peptizer for NR,IR,SBR and Peptizer for NR,IR,SBR and NBR.

NBR.

Low-molecular-weight

polyethylene

polyethylene A-C Polyethylene 617AA-C Polyethylene 617A Release agent, LubricantRelease agent, Lubricant Calcium Oxide

Calcium Oxide Desical PDesical P DesiccantDesiccant

Aliphatic-naphthenic-aromatic resins

aromatic resins Strucktol 60NSStrucktol 60NS Homogenizing agent for all elastomers.Homogenizing agent for all elastomers. Paraffin wax

Paraffin wax Release agent, lubricantRelease agent, lubricant Polyethylene glycol

Polyethylene glycol Carbowax Carbowax PEG3350

PEG3350 Activator for silica, lubricantActivator for silica, lubricant

Petroleum hydrocarbon

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PROCESSING AIDS

Selection is based onSelection is based on

 Nature of polymerNature of polymer  Solubility parameterSolubility parameter  Viscosity requirementViscosity requirement  Filler dispersionFiller dispersion

 Processing requirementProcessing requirement

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ANTI-DEGRADANTS

-

They are agents added to rubber to improve They are agents added to rubber to improve ageing properties, resistance to oxygen, ozone, alkali, acid, chemicals etc

ageing properties, resistance to oxygen, ozone, alkali, acid, chemicals etc

TYPE

TYPE EXAMPLEEXAMPLE STAININGSTAINING Hindered Phenol

Hindered Phenol 2,6 Di-t butyl p-cresol2,6 Di-t butyl p-cresol None to slightNone to slight Hindered Bis-phenols

Hindered Bis-phenols Anti-oxidant 2246Anti-oxidant 2246 None to slightNone to slight Hindered Thiobisphenols

Hindered Thiobisphenols Santowhite CrystalsSantowhite Crystals SlightSlight Hydroquinones

Hydroquinones 2,5 di(tert-amyl) hydroquinone2,5 di(tert-amyl) hydroquinone None to slightNone to slight Phosphites

Phosphites Tri(mixed mono and di-nonyl-Tri(mixed mono and di-nonyl-phenyl) phosphite

phenyl) phosphite None to slightNone to slight

Diphenylamines

Diphenylamines Octylated diphenylamineOctylated diphenylamine Slight to moderateSlight to moderate Naphthylamines

Naphthylamines Phenyl-alpha-naphthylaminePhenyl-alpha-naphthylamine ModerateModerate Quinolines

Quinolines Polymerized 2,2,4, tri-methyl Polymerized 2,2,4, tri-methyl 1,2-dihydroquinoline

1,2-dihydroquinoline Slight to moderateSlight to moderate

Carbonyl-amines

condensation product

condensation product Reaction product of diphenylamine and acetoneReaction product of diphenylamine and acetone ConsiderableConsiderable Para-phenylene diamines

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ANTI-DEGRADANTS

Selection is based on

 Type of protection desiredType of protection desired

 Environment in which the product is exposed.Environment in which the product is exposed.  Chemical activityChemical activity

 Persistence (volatility and extractability)Persistence (volatility and extractability)  Nature of end useNature of end use

 Discolouration and stainingDiscolouration and staining  ToxicologyToxicology

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OTHER MATERIALS

 PeptizersPeptizers : They speed up the rate of polymer break down and also : They speed up the rate of polymer break down and also

control the speed of breakdown, decreasing nerve within the control the speed of breakdown, decreasing nerve within the compound and shrinkage during subsequent processing.

compound and shrinkage during subsequent processing. penta chloro thiophenol

penta chloro thiophenol Renacit VIIRenacit VII

 RetardersRetarders : They help to increase the scorch time (premature : They help to increase the scorch time (premature

vulcanization) but do not interfere with the vulcanization vulcanization) but do not interfere with the vulcanization

 cyclohexyl thiophthalimide (CTP)cyclohexyl thiophthalimide (CTP)Santogard PVISantogard PVI

 StiffenersStiffeners : Stiffeners are used to improve the plasticity of the : Stiffeners are used to improve the plasticity of the

compound in very small quantities. compound in very small quantities.

dihydrazine sulfate

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 Flame retardantsFlame retardants

Chemicals which can improve the flame retardency of

the compound

highly chlorinated paraffins and waxes, antimony oxide,

aluminium oxide and selenium

aluminium oxide and selenium  Colors and pigmentsColors and pigments

 They provide esthetic look and appearance for the product They provide esthetic look and appearance for the product

[organic and inorganic]

[organic and inorganic]  Tackifying agentsTackifying agents

They are useful in providing tackiness to the compound.

wood rosin, coumarone resins, pine tar.

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Blowing agents



They are materials which provide either open or

closed cell structure by producing CO2 or nitrous

gases during vulcanization



dinitroso pentamethylene tetramene (DNPT)



azocarbonamide (ADC)

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 Bonding agentsBonding agents

 They facilitate adhesion between rubbers, fibers, fabrics, They facilitate adhesion between rubbers, fibers, fabrics,

metals

 chemlok, resorcinol – formaldehyde- latex for dipping of chemlok, resorcinol – formaldehyde- latex for dipping of

nylon cords in tyre manufacture

nylon cords in tyre manufacture  ReordantsReordants

 They are basically perfumes added to mask odors of rubber They are basically perfumes added to mask odors of rubber

during processing and service life of rubber.

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STEPS OF COMPOUND DEVELOPMENT

Modification of existing compound with respect to

 Cost/priceCost/price  ProcessingProcessing  PerformancePerformance

New compound development

 Set specific objectives (properties, processing, price etc)Set specific objectives (properties, processing, price etc)  Select best polymerSelect best polymer

 Study test data of existing compoundsStudy test data of existing compounds  Survey compound formulations.Survey compound formulations.

 Choose starting formulation.Choose starting formulation.

 Develop compound in the laboratory to meet objectives.Develop compound in the laboratory to meet objectives.  Estimate cost of the compound.Estimate cost of the compound.

 Evaluate processability in factoryEvaluate processability in factory

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The mix



Rubber

100



Vulcanizing agent

0.3 - 3.5



Accelerator/s

0.5 – 1.5



Activator

2.5 – 5.0



Antidegradents

1 - 2



Fillers

_{As required}_{As required}



Softner

5 - 10

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STAGES OF PRODUCT DEVELOPMENT

:

Compound Design,

_{Lab Evaluation,}

_{Shop floor processing trials} (mixing, moulding,extrusion,

calendaring, fabrication of product, curing, etc ),

_{Analysis of feedback ,}

_{Compound Modification (if reqd.),}

_{Testing of processing properties} and of finished product,

_{Field trials,}

Validation of manufacturing process.

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MIXING

 Compound properties & batch to batch consistency depends Compound properties & batch to batch consistency depends on :

on :



 Compounding formulation design,Compounding formulation design,



 Raw materials Quality, Raw materials Quality, 

 Effects of Further Processing,Effects of Further Processing,

 Rework blending (Rework Quality & Quantity)Rework blending (Rework Quality & Quantity)

 Rubber processing equipments available & their Rubber processing equipments available & their

condition.condition.

 The knowledge of Raw Materials used & their behavior during The knowledge of Raw Materials used & their behavior during

mixing and further processing is essential

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MIXING

 Mixing Process is the base of Rubber Product Manufacturing Mixing Process is the base of Rubber Product Manufacturing

Technology.

 The success of subsequent processing & finished product The success of subsequent processing & finished product quality depends entirely on the quality & batch-to-batch

quality depends entirely on the quality & batch-to-batch

consistency of the mixed compounds.

 ‘‘Mixing’Mixing’ deals in deciding: deals in deciding:

 What equipment to use (speeds, pressures, temperature, time What equipment to use (speeds, pressures, temperature, time cycles, procedures, etc. to blend the selected compounding

cycles, procedures, etc. to blend the selected compounding

ingredients into a properly mixed compound.

 How to achieve High Degree of Dispersion and batch to How to achieve High Degree of Dispersion and batch to

batch consistency.

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MIXING

• Mixing process can be sub-divided into three stages :

1) Feeding ingredients to mixer (correct quantities at

correct times at correct temperature.),

2) Actual Mixing of the ingredients,

3) Discharge of mixed compound and its shaping,

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MIXING Five main steps involved in the Mixing Operations :

1.

1. Sub DivisionSub Division

Of larger lumps & aggregates,Of larger lumps & aggregates,

2. 2. IncorporationIncorporation Of powders or liquids Of powders or liquids 3. 3. DispersionDispersion

Involves reduction of the size of agglomerates,

4.

4. Simple MixingSimple Mixing

Involves moving particles from one point to another.

5.

5. Viscosity ReductionViscosity Reduction By breakdown of the polymer and transforming it to By breakdown of the polymer and transforming it to

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• A good Dispersion rating requires :

 High Shear Stress (i.e. High mix viscosity),

 High Filler Loading,

 Polymers of not too low viscosity,

 Low Mixing temperatures,

 Charging oils at the end of mixing cycle.

MIXING

• During Dispersive mixing, the carbon black agglomerates are broken down to less than 1 micron size.

• Dispersion largely depends on shear stress ( a critical value of shear stress is necessary to breakdown the agglomerates

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• To avoid scorching of compound; a two stage mixing procedure is used.

• Stage 1 - carbon black and other non vulcanizing additives are combined with the raw rubber and Higher mixing temperatures up to 160°C are used. [The term Master Batch is used for first stage mixture]

• Stage 2 - After stage 1 mixing has been completed, and time for cooling has been allowed; stage 2 mixing is carried out in which vulcanizing agents are added. Lower mixing temperatures 90-100 °C are used.

Two-Stage Mixing in Internal Mixers

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NR Mastication & Blending NR+SR

• Mastication of NR to Optimum Degree and proper blending of Synthetic Rubbers with NR is Very Important .

• Ingredients which are difficult to disperse (e.g. hard carbon blacks, Ppt. silica, ZnO, etc) require Higher stock viscosity to disperse well.

 Stock Viscosity Control is achieved through:

 Compounding formulation design,

 Close temperature control during mixing operations,

 Use of specific sequence for addition of ingredients ,

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• Raw NR is dry & tough (Mooney Viscosity at 100°C > 80) and has to be masticated to a Workable Level of Mooney Viscosity of 50 to 60.

• Most Synthetic Rubbers are produced to a tailored Mooney viscosity (range 50 – 60) and hence ‘Mastication’ is not

necessary.

• Keep Lower Mastication Temperatures when a Two-Roll mill is used (say, 60-70°C).

• Viscosity of Masticated NR should be closer to the Synthetic Rubber to be blended with it.

• NR-BR blends require higher shear rates for proper

blending and hence Banbury / Intermix are more suitable than a mixing mill.

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EFFECT OF MASTICATION TEMPERATURE ON MOONEY VISCOSITY OF NR

MILLING

TIME, MIN

TIME, MIN MOONEY VISCOSITY (ML1+4 @ 100°C, UNITS)MOONEY VISCOSITY (ML1+4 @ 100°C, UNITS)

WITHOUT PEPTIZER

WITHOUT PEPTIZER WITH PEPTIZER (DBD=0.5 PHR)WITH PEPTIZER (DBD=0.5 PHR) @ 70°C @ 70°C @ 100°C@ 100°C @ 70°C@ 70°C @ 100°C@ 100°C 0 0 9595 9595 9595 9595 3 3 7676 8585 5858 5656 6 6 5757 8383 4040 4040 9 9 4747 6868 3333 2828 12 12 4545 6565 3030 2424 START TEMPERATURE,

START TEMPERATURE, MOONEY VISCOSITY (ML1+4 AT 100°C), UNITSMOONEY VISCOSITY (ML1+4 AT 100°C), UNITS OPEN MILL

OPEN MILL (TIME = 8 MIN)(TIME = 8 MIN)

70 70 °C°C 100 100 °C°C PEPTIZER = 0 PEPTIZER = 0 55 55 75 75 PEPTIZER = 0.25 PEPTIZER = 0.25 42 42 42 42 PEPTIZER = 0.5 PEPTIZER = 0.5 36 36 37 37 INTERNAL MIXER

INTERNAL MIXER (TIME 4 (TIME 4

MIN) MIN) 150 150 °C°C 9090 88 88 54 54 48 48 42 42 36 36

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Mixing Mixing Time, Time, Min Min Mixer Speed 25 rpm

Mixer Speed 25 rpm Mixer Speed 50 rpmMixer Speed 50 rpm No Peptizer

No Peptizer 0.1 Phr PCTP0.1 Phr PCTP No PeptizerNo Peptizer 0.1 Phr PCTP0.1 Phr PCTP ML1+4@100°C ML1+4@100°C ML1+4@100°CML1+4@100°C ML1+4@100°CML1+4@100°C ML1+4@100°CML1+4@100°C 0 0 9090 9090 9090 9090 2 2 7474 6969 6969 5252 4 4 68.568.5 6060 5050 3737 6 6 6767 5656 4242 2929 8 8 6565 5353 3434 - -10 10 6161 5050 -- -

-Note the rapid reduction of Mooney viscosity at higher rotor speeds in the presence of chemical Peptizer at a very small dosage.

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Effects of “Under Mastication” of NR

• Lower Mixing Cycles,

• High heat build up during mixing and subsequent steps,

• Poor extrudability / calendaring properties of the stock,

• Excessive shrinkage & dimensional control problems with extrudates / calendared stocks.

• Scorchy compounds.

• Excessive porosity in extrudates,

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Effects of “Over Mastication” of NR

 _{Lower shrinkage of extrudates / calendared sheets,}

• Lower die swell & loss of dimensional control,

• Increased curing defects in finished products due to excessive flow and air entrapment,

• Compounded sheets stick to each other during storage and sagging of sheets,

• Excessive surface tack due to poor green compound strength,

• Loss of dynamic, tensile & tear strength properties of the vulcanizate,

• Changes in the viscosity of solvent based solutions & loss of surface tack.

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MIXING

49

PROBLEMS & REASONS

PROBLEMS

PROBLEMS REASONSREASONS

Poor

Dispersion

Batch size not optimized, mixing time is

lower, filler addition time not proper,

insufficient ram pressure, poor temp.

control, poor / inconsistent raw material

quality, excessive moisture content in

polymer and fillers, under / over

mastication of NR. mastication of NR. Batch to Batch Batch to Batch Variations Variations

Variation of start temp., variation in dump

time and / or temp. , poor dispersion,

variation in ram pressure, variation in

polymer / filler/ oil quality / rework quality,

under / over mastication of NR

Poor

Processability

Compound viscosity not within controlled

limits, under / over mastication of NR,

Processing temp. not under control, poor

dispersion, higher loading of plasticizer /

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Manufacturing process



Unvulcanized rubber, whether natural or synthetic

behaves as a viscoelastic fluid during mixing. It is the

operation required to obtain a thorough and uniform

dispersion of all ingredients called for by the formulae in

the rubber



Machinery

2-roll mixing mill

kneader

internal mixers

Continuous, automatic high speed mixing

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Capacities: Banbury Mixers

Banbury Banbury Mixer Mixer Mixer Mixer Chamber Chamber Net Volume, Net Volume, ltr ltr Approx. Approx. Batch Wt * Batch Wt * kg kg Mixing Mixing Speed Speed Range, Range, RPM RPM Torque rating Torque rating kW / RPM kW / RPM Approx. Approx. Machine Machine Weight, MT Weight, MT Compact Compact Drive

Drive DriveDriveUniUni F 50 F 50 5050 5050 40 - 12040 - 120 2.22.2 4.64.6 13.213.2 F 80 F 80 8080 6060 30 - 10530 - 105 3.73.7 6.36.3 16.116.1 F 120 F 120 120120 9090 30 - 9030 - 90 5.65.6 9.09.0 19.519.5 F 160 F 160 160160 120120 20 - 8020 - 80 7.57.5 12.012.0 30.230.2 F 200 F 200 200200 165165 20 - 6020 - 60 8.98.9 12.712.7 30.530.5 F 270 F 270 270270 202202 20 - 6020 - 60 13.113.1 24.624.6 43.043.0 F 370 F 370 414414 310310 20 - 6020 - 60 -- 37.337.3 54.054.0 F 440 F 440 438438 330330 20 - 6020 - 60 -- -- - -F 620 F 620 672672 500500 20 - 5020 - 50 -- 52.252.2 110.5110.5 ( * Fill factor = 75% , S.G. = 1.0 )

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Capacities: Intermix Capacities: Intermix Intermix Intermix Mixer Mixer Chamber Chamber Net Volume, Net Volume, ltr ltr Approx. Approx. Batch Wt Batch Wt kg kg Mixing Speed, RPM

Mixing Speed, RPM _{Motor HP}_{Motor HP}

1-Speed , 2-Speed 1-Speed , 2-Speed

Machine Machine Weight, Weight, MT MT Single Speed

Single Speed Two SpeedTwo Speed K 0

K 0 1.81.8 1.261.26 7676 75 / 15075 / 150 5, 5 / 105, 5 / 10 5.6_5.6

K 1

K 1 5.55.5 3.93.9 40 / 14540 / 145 Variable driveVariable drive 5050 20₂₀

K 2 K 2 2020 1414 3030 22 / 4422 / 44 50. 50 / 10050. 50 / 100 50₅₀ K 2A K 2A 4949 3434 3333 22 / 4422 / 44 150 , 75 / 150150 , 75 / 150 60₆₀ K 4 K 4 9191 6464 3333 22 / 4422 / 44 220, 50 / 300220, 50 / 300 ₉₈₉₈ K 5 K 5 143143 100100 3333 22 / 44322 / 443 300, 200 / 400300, 200 / 400 ₁₄₀₁₄₀ K 6 K 6 206206 144144 3333 22 / 4422 / 44 475, 320 / 640475, 320 / 640 ₂₃₅₂₃₅ K 6A K 6A 257257 180180 3333 22 / 4422 / 44 500, 350 / 700500, 350 / 700 ₂₈₀₂₈₀ K 7 K 7 310310 217217 3333 22 / 4422 / 44 750, 500/1000750, 500/1000 ₃₁₀₃₁₀ K 8 K 8 498498 349349 3333 22 / 4422 / 44 -- _- -( * Fill factor = 70% , S.G. = 1.0 )

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Dry rubber based products

Mix and Compound Design

For manufacture of dry rubber products, the

following minimum process steps are essential



compounding



shaping

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MIXING PROCEDURE

Weighing compounding ingrediants as per

formulation Mastication

Compounding And Homogenisation

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Prewarming

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DRY RUBBER PRODUCTS MANUFACTURE RUBBER COMPOUNDIN G CHEMICALS MATURATION PRE-WARMING TESTING& QC

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MOULDED GOODS _{EXTRUDED GOODS} CALENDARED GOODS BLANK PREPARATION MOULDING (HYDRAULIC PRESS)

PACKING AND DESPATCH

AUTO CLAVE OR

OVEN

FINISIHING OPERATION AND QUALITY CONTROL VULCANISATION