Rubber Product

Base polymers

Fillers system

Processing aid system

Stabilizer system

Curing system

Miscellaneous additives

Curing System Cross linking/ Vulcanizing agent Accelerator for cross linking Accelerator activators Accelerator modifiers

Stabilizer System• Antioxidants• Antiozonants

Composition of Rubber ProductsSl. No. General Class Actual Components

1. Base polymer NR, BR, SBR, IIR, CR, EPDM etc.

2. Filler Carbon block, Clays, whiting silica fillers etc.

3. Processing aids Petroleum oils, waxes etc.

4. Curatives Cross linking agents, organic accelerators, organic & inorganic activators, promoters and retarders

5. Antiageing compounds

Organic compounds as antioxidants and antiozonants

6. Miscellaneous additives

Coloring agents, abrasives, antistatic compounds, deodorants etc.

Compounding

Compounding means the incorporation of several ingredients uniformly to the base polymer to yield a semi homogenous mass known as mix or RUBBER COMPOUND.

Major factors in compounding: PriceProcessingProperties

Selection of ingredients, their appropriate dosage and then compounding requires serious and careful consideration by the rubber compounder.

Natural Rubber

Cis-1,4 polyisoprene

Properties of Natural Rubber

Molecular Weight –

Molecular Weight Distribution – Broad

High tack & green/gum strength

Good processing

Crystallizing rubber

8n

6w

10 x 5 - 3 M

10 x 1.5 - 1 M

Vulcanizate properties of Natural Rubber

Tensile strength (gum): 17 to 24 MPa Tensile strength(filled with C-black): 24 to 32 MPa Abrasion and Wear: Below 350C better than SBR

Above 350C SBR is better Skid resistance: Moderate, improved with OENR Dynamic properties: High resilience (>90%)

At high strain fatigue life superior to that of SBR

Compression set and creep: Poorer than SRs Aging: Poor but improved antioxidants or antiozonants

Synthetic Rubbers

1. Homo and copolymers of olefins and other bifunctional monomers

2. Made by polyadditions or polycondensation reactions.

Why synthetic Rubber?

As a substitute of natural rubber

To meet the demands for some special properties where natural rubber fails

For examples: ProcessabilityOil and solvent resistanceLow temperature flexibilityHeat resistant propertiesBetter dynamic propertiesAbrasion resistanceEnvironmental stability

Synthetic Rubbers

General purpose and non-oil resistant rubbers

Styrene-butadiene rubber (SBR)Polyisoprene rubber(IR)Polybutadiene rubber (BR)Isobutylene-isoprene(butyl) rubber (IIR)Ethylene propylene rubbers (EPDM)Thermoplastic rubbers

Synthetic Rubbers

Styrene – Butadiene Rubber

Emulsion SBR: Hot process (50oC), Cold process (5-10oC)

Solution SBR: Better grades with controlled microstructure

CH2 CH CH CH2 CH2 CH

Special purpose rubbers

Chloroprene rubber (CR) Chlorosulphonated polyethylene (Hypalon) Acrylonitrile butadiene rubber (Nitrile) Polyacrylic rubbers Fluorocarbon rubbers Silicone rubbers Polyurethane rubbers Ethylene-acrylic rubber Ethylene-vinyl acetate Polysulfide rubber (Thiokol)

Synthetic Rubbers

Arrangement of monomers Randomcis–1,4 Butadiene (% wt.) 9trans-1,4 Butadiene (%wt.) 761,2–butadient (vinyl) (%wt.) 15Intrinsic viscosity (dl/g) 2.0Gel content NegligibleMooney viscosity [ML(1+4)100oC] 50Specific gravity 0.94

Properties of cold SBR:

Styrene – Butadiene Rubber

SBR 1000: Hot polymerized rubbers1500: Cold polymerized rubbers1600: Cold-black masterbatch with 14 or less phr oil

1700: Cold-oil-masterbatch1800: Cold-oil-black masterbatch with > 14 phr oil1900: Miscellaneous dry polymer masterbatches2000: Hot latices2100: Cold latices

Grades:

Styrene – Butadiene Rubber

Tires, footwear, mechanical goods, sponge & foamed products, water proofing, hose, belting, adhesives ad carpet back coatings.

Applications:

Styrene – Butadiene Rubber

IngredientsFillers: Reinforcing:

Carbon Black: SRF, GPF, FEF, FF, HAF, EPC, ISAF,SAF etc.

Silica: Hi – Sil (hydrated silica)Silene EF (hydrated Ca-sillicate)

Non – reinforcing (inert):

Whiting (CaCO3), TiO2, Clays and related materials like china clays, soft clays, hard clays, calcined clays etc., graphite, MgCO3, talc, French chalk and so many.

Processing Aids

Peptizers:

Pepton 22 Di(o-benzamido phenyl disulfide)

Pepton 44 Activated Di(o-benzamido phenyl disulfide)

Renacit IV Zn-salt of pentachlorothiophenol

Renacit VII Pentachlorothiophenol with activating and dispersing additives

Renacit VIII Metal complex on an organic carrier

Softeners (Physical platicizers):

Petroleum aids – paraffinic, naphthenic & aromatic

Ester plasticizers – Dioctyl sebacateDibutyl sebacateDOP, DBP, DIOP

Petroleum jellyParaffin waxGlycols Fatty acids & saltsFactice, Pine tar, Bitumen etc.

Processing Aids

Sulfur and related elements

Sulfur bearing chemicals

Non sulfur crosslinking agents

Crosslinking (Vulcanizing Agents)

Aldehyde amines : Hexa

Guanidines : DPG, TPG, DOTG

Thiazoles : MBT, Na-MBT, Zn MBT, MBTS

Sulfenamides : CBS, NOBS, TBBS

Dithiocarbamates : ZDC, ZDEC, SDC

Thiuram sulfides : TMTD, TETD, TMTM, DPTS

Xanthates : ZIX, SIX, ZBX

Thisocarbamyl sulfenamide: OTOS (Cure rite 18)

Accelerators:

Accelerator Modifiers - Activators

Metal Oxides: ZnO, hydrated lime, litharge, red lead, MgO, alkali carbonates and hydroxides

Organic acids: Fatty acidsAlkaline substances: Ammonia, diethanol &

triethanol amine, amine salts, reclaim rubber etc.

Retarders – (PVI)N-cyclohexyl thiophthalimidephthalic anhydrideN-nitrosodiphenyl amine

Antidegradants

formation radical free withscission chain ROOHR ROOH RH ROO

ROOO R ; RRH 2

frasments Harmless ROOHA ROOH AH ROO

A RH AH R

Antioxidants – Hindered phenol, amino phenol, hydroquinone, phasphite, Diphenyl amine,naphthyl amine (PBN), phenylene diamine (IPPD)

Antidegradants

Miscellaneous Additives

Coloring materials, blowing agents, flame retardants, antistatic agents (quaternery)ammonium salts, abrasives, coupling agents etc.

Antizonants – Dialkyl-phenylene diamine Nickel dibutyldithiocarbamateWaxes

Vulcanization by Methods other than Molding

BATCH CURING METHODS

Autoclave or steam pan Gas curing Oven curing Water curing Cold curing

Vulcanization by Methods other than Molding

CONTINUOUS VULCANIZING METHODS

High-Pressure Steam (Cables) Hot air tunnel Molten salt bath Fluidized bed Continuous drum cure Microwave curing

Accelerated Sulfur Vulcanization

Accelerator + Sulfur Ac – Sx - Ac

Ac – Sx – Ac + Rubber Rubber – Sx – Ac

Rubber – Sx – Ac + Rubber Rubber – Sx - Rubber

Monomeric Polysulfide

Polymeric Polysulfide

S

C

N

S NR2

MBT

S

C

N

S

S

C

N

S

S8

S

C

N

S

S

C

N

SSx

C C CH2

HNR2

MBT

S

C

N

SH[ initiator ]

[ -R2NH ]

+

(rubber)

Accelerated Sulfur Vulcanization

S

C

N

SSxHC

C

C

(Rubber)

MBT+

SxHC

C

C

CH

C

C

Crosslinked vulcanizate

Accelerated Sulfur Vulcanization

Rubber Molecules

Crosslinks

Unvulcanized network Vulcanized network

Network formation by vulcanization

Crosslink density

Hysteresis permanent set friction coefficient

Tensile strength

Hardness

High speed dynamic modulus

Tear strength fatigue life toughness

Vulc

aniz

atio

n pr

oper

ties

Static modulus

The effects of vulcanization

SX

SX

Accelerator

SSS2SX

Structure formed during accelerated vulcanization of elastomers