Compounding Technique

Rubber compounding

What is rubber compounding?

Why we are doing?

How can we do it successfully?

Definition of Rubber Compounding

• is the art and science of selecting and comb

ining elastomers and additives to obtain an i

ntimate mixing that will develop the necess

ary physical and chemical properties for a fi

nished product.

Objective of Rubber Compounding

1. To secure certain properties in the finished prod

uct to satisfy service requirements.

2. To attain processing characteristics necessary f

or efficient utilization of available equipment.

3. To achieve the desirable properties and process

ability at lowest possible cost.

To be Sucessful in Compounding

• Must understand the properties and function

of hundreds of elastomers and rubber chemic

als

• Must also have intimate knowledge of the eq

uipment used for mixing, extrusion, calender

ing, molding and vulcanization.

Procedure for Compound Development

• 1. Set specific objectives (properties, price, etc.).

• 2. Select base elastomer(s).

• 3. Study test data of existing compounds.

• 4. Survey compound formulations and properties data presented by material suppliers in their literature .

• 5. Choose a starting formulation.

To be continued

• 6. Develop compounds in laboratory to meet objectives.

• 7. Estimate cost of compound selected for further evaluation.

• 8. Evaluate processability of compound in factory.

• 9. Use compound to make a product sample

• 10. Test product sample against performance specification.

Classification of Compounding Ingredients

• 1. Elastomers

• 2. Vulcanizing Agents (Curatives)

• 3. Accelerators

• 4. Activators and Retarders

• 5. Antidegradants(Antioxidants, Antiozonants, Protective Waxes)

• 6. Processing Aids(Peptizers, Lubricants, Release Agents)

To be continued

• 7. Fillers (Carbon Blacks, Non-black Mater

ials)

• 8. Plasticizers, Softeners, and Tackifiers

• 9. Color Pigments

• 10. Special Purpose Materials(Blowing Age

nts, Reodorants, etc,)

Requirements of Rubber Compound for Good Processing

• 1. Uniform plasticity and recovery.

• 2. Uniform scorch rate.

• 3. Uniform rate of cure.

Vulcanizing Agents

• To cause chemical reaction resulting in cros

slinking of elastomer molecules.

• Sulfur is by far the most widely used.

VULCANIZING AGENTS

• TYPE COMMON USE

• Sulfur or Sulfur- Natural Rubber, bearing Materials Isoprene, SBR, Buty1,

Butadiene, EPDM, Nitrile,Norsorex

• Organic Peroxides Urethane, Silicone,

Chlorinated Polyethylene, Crosslinked Polyethylene, Vamac, Vynathene, PVC/Nitrile

To be continued

• TYPE COMMON USE• Metallic Oxides Neoprene,

Hypalon,Thiokol• Organic Amines Acrylic,

Fluorocarbon, Epichlorohydrin, Vamac

• Phenolic Resins Butyl

ACCELERATORS

• Use to reduce vulcanization time, or cure time by increasing the speed of vulcanization

• Most are organic substance containing both nitrogen and sulfur(Today)

• Inorganic accelerator was widelyused years ago (litharge, lime, and magnesia)

ORGANIC ACCELERATORS

• TYPE EXAMPLE TYPICAL USE

• Aldehyde-amine Reaction product of Fast curing

butyral dehyde and accelerator for

aniline reclaim,hard

rubber and self-

curing cements

• Amines Hexamethylene Delayed action

tetramine

slow accelerator

for natural rubber

To be continued

• TYPE EXAMPLE TYPICAL USE

• Guanidines Diphenyl guanidine Secondary accelerator

(DPG) to activate thiazole

type accelerator

• Thioureas Ethylene thiourea Fast curing accelerator

(ETU) for Neoprene,Hypalon

and Epichlorohydrin

To be continued

• TYPE EXAMPLE TYPICAL USE• Thiazoles Benzothiazyldisulfide Safe-processing

(MBTS) moderately fast curing accelerator for natural rubber,

Isoprene,SBR,

Nitrile,Butyl and EPDM

• Thiurams Tetramethylthiuram Fast curing sulfur- disulfide (TMTD) bearing accelerator

for SBR, Nitrile, Butyl and EPDM

To be continued

• TYPE EXAMPLE TYPICAL USE• - - - - 2Sulfenamides N cyclohexyl Safe processing,

bbbbbbbbbbbb- bbbbbbb bbbbbb bbbbbbbbbbb

bbbbbbbbbbb bbb () natural rubber, SBR and Nitrile

• bbbbbbbbbbbbbbbb bbbb bbbbbbbb bbbb bbbbbb bbbbbbbbbbb

• bbbbbbbbb Dibutylxanthogen Fast curing, low bbbbbbbbb bbbbbbbbbbb

bbbbbbbbbbb bbb natural rubber and SBR

Activators and Retarders• Activators

- used to activate the accelerator and improve its effectiveness (ZnO, stearic acid, litharge, magnesia, and amine) - attain good crosslink efficiency

• Retarders - used to reduce the scorchness (phthalic anhydride, salicylic acid and sodium acetate)

Antidegradants

• To retard the deterioration of rubber compo

unds initiated by

- oxygen, ozone

- heat, light

- metal catalyst and

- mechanical flexing

PROCESSING AIDS

• To facilitate processing operation such as

- Mixing

- Calendering

- Extrusion and

- Molding

PROCESSING AIDS

• COMPOSITION EXAMPLE(Tradenames) FUNCTION

• - 44ActivatedDithio Pept on Pept i zer f or NR

bbbbbbbbbbbbbb

• - Poly Polyac Chemical conditioner

paradinitrosobenzene for IIR

To be continued

• COMPOSITION EXAMPLE(Tradenames) FUNCTION

• Xylyl mercaptans RPA3 Peptizer for NR, IR,

SBR and NBR.

Stabilizer for cement

viscosity

• Low-molecular- A-C Polyethylene Release agent, wei

ght 617 A lubricant polyethylen

e

• Calcium oxide DesiCal P Dessiccant

To be continued

• COMPOSITION EXAMPLE(Tradenames) FUNCTION

• Aliphatic- Strucktol 60NS Homogenizing naphthenic-

agent for all aromatic resins elastomers

• Paraffin Wax Numerous Release agent, lubricant

• Polyethylene Carbowax PEG3350 Activator for glycol silica lubricant

• Petroleum Petrolatum Release agent, hydrocarbon lubricant

Fillers

• To reinforce physical properties

• To reduce cost

• Devided into two types(Reinforcing and Extending)

• Selection of reinforcing filler is the third most important task in compounding(next to elastomer and cure system)

Types of Fillers• Reinforcing Type

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

Non-Black - Silica - Zinc Oxide

- Magnesium Carbonate - Aluminum Silicate - Sodium Aluminosilicate - Magnesium Silicate

Types of Fillers (continued)

Extending Type

- Calcium Carbonate

- Barium Sulfate

- Aluminum Trihydrate

- Talc

HardnessNR has hardness itself (no filler) 35-40 IRHD

• ISAF 1.7 phr increases 1 IRHD

• HAF 1.9 phr increases 1 IRHD

• Hisil 233 2 phr increases 1 IRHD

• Hard clay 5 phr increases 1 IRHD

• Soft clay 7.7 phr increases 1 IRHD

• Whiting 6.4 phr increases 1IRHD CaCO3

• Oil 2 phr decreases 1 IRHD

Particles Size

• Play a major role in the tensile strength

small particle size highest tensile strength at optimum loading

• Fine fillers is difficult to process (need more energy for their dispersion into the elastomer)

• Effects Mooney scorch small particle size the scorch resistance

reduces

PLASTICIZERS,SOFTENERS, AND TACKIFIERS

• Objective for Using -

Aid mixing, -

Modify viscosity, -

Produce tack, -

Provide flexibility at low temperature

Selection of Plasticizers• The important criteria are:

• Compatibility

• Efficiency

• Cost

Example:

- Aromatic type oil is not compatibe with NR, Isoprene, IIR, EPDM

- Paraffinic type oil is not compatible with SBR, butadiene, NBR, CR

PLASTICIZERS,SOFTENERS, AND TACKIFIERS

• CATEGORY OF MATERIAL FUNCTION

• Petroleum Oils -Aromatic Plasticizer,Softener

- Paraffinic

- Naphthenic

• Ester Plasticizers - Dioctyl phthalate

- Dioctyl sebacate

- Tributoxyethyl phospate

Low temperature - Di (butoxyethoxyethyl) formal

plasticizers - Triglycol ester of vegetable oil

To be continued

• CATEGORY OF MATERIAL FUNCTION

• Vulcanized Vegetable Oils Extender, Plasticizer

• Asphaltic Hydrocarbon Extender, Plasticizer

• Pine Tar Plasticizer,Tackifier

• Resins -Coumarone-indene Tackifier,Plasticizer

- Petroleum

- Phenolic

• Polymeric esters Extender, Plasticizer

• Rosins - Hydrogenated rosin Tackifier

Special Purpose Materials• Not require in the majority of rubber compo

und

• Used for specific purpose Example:

- Blowing agents - Reodorants

- Adhesion promotors - Flame retardant - Fungicide - UV light absorbers