Compounding Technology

7/29/2019 Compounding Technology

1/35

COMPOUNDING TECHNOLOGY

Basically a compound can be formulated with the below main general

mode which is as follows:

1. Polymer2. Activator3. Accelerator4. Filler5. Processing aid & if necessary6. Special agents

i. Antioxidantii. Antiozonantiii. Flame retardenceiv. Antifoggingv. Antistaticvi. Antidetergent

7. Vulcanizing agentsIn order to develop a rubber compound, the various ingredients to

be used are complied into a recipe, every recipe contains a number of

components, each having a specific function either in the processing,

vulcanization or end use of the product, all the ingredients used as

normally given in amounts based on a total of 100 parts of the rubber.

7/29/2019 Compounding Technology

2/35

ACTIVATORS

Activators are chemical which increase rate of vulcanization are used to

activate the accelerator and improve its effectiveness. Typically metal oxides

(zinc oxide) and fatty acids (stearic acid) are used as activators. These make

better able to react with sulphur to form cross links.

ZINC OXIDE

Zinc oxide is an universal activator used in all rubber compounds.

Usually dose is 3 to 5% of the weight of the rubber. In higher quantities it

exerts a reinforcing effect and improve thermal conductivity, heat resistance,

tear resistance of abrasion. There is increase of hardness without affecting

rebound resilience.

Zinc oxide particles are fine, about 15 mu it does not dissolve in rubber

but with stearic acid the oxide particles are covered with zinc stearate which

dissolve in rubber and then making it possible to be used as an activator.

STEARIC ACID

This is also an activator for accelerator which functions by forming zinc

soap, which in turn activates the accelerators. Other fatty acids such as soya

fatty, hydorxy stearic acid, oleic acid, palmitic acid etc also function in a

similar manner. But stearic acid is considered to be the best and is used upto 1

to 5%.

7/29/2019 Compounding Technology

3/35

ACCELERATORS

Accelerators are used to reduce the vulcanization time or cure time by

increasing the speed of vulcanization. Most accelerators are organic in nature

containing nitrogen and sulfur. Inorganic types are litharge, lime and magnesia.

Even though an organic accelerator is used in small proportion, an accelerator

has a proformal influence on the nature of the cross linking which determines

the physical properties like tensile, tear, flexing, abrasion, compression set etc.

Mainly accelerators are classified as two types namely.

Primary accelerators

It is a single accelerator system capable of producing sufficient activity

to produce satisfactory cures within specified times.

Secondary accelerators or the boosters

In this vulcanization system two or more accelerators are present, the

primary accelerator is present as the largest amount and the secondary or the

booster in 10-20% of the total.

Primary accelerators are generally the thiazole and sulfonamide while

the secondary are thiurams, dithiocarbamates, guanidines.

The important type of accelerators used in compounding of EPDM

rubber are as follows.

7/29/2019 Compounding Technology

4/35

1.MBT

Chemical Name : 2 mercaptobenzothiazole

Chemical Structure :

Molecular Weight : 167

Appearance : Cream coloured oil treated powder

Specific gravity : 1.51

Melting point : 176 C

Ash content % by mass : 0.4

Solubility : Soluble in acetone, chloroform and dil-

alkali Insoluble in water and gasoline

Classification : Semi ultrafast accelerator

Color code : Brown colored strip

2. CBS

Chemical Name : N-Cyclohexyl-2-benzothiazole sulphenamide

Chemical Structure :

Molecular Weight : 264

Appearance : Light tan to buff pellets

Specific gravity : 1.30

Melting point : 100OC

Ash content, % by mass : 0.25

7/29/2019 Compounding Technology

5/35

Solubility : Soluble in benzene, naphtha, CCl4, ethyl

acetate and acetone. Insoluble in H2O

Classification : Fast delayed action accelerator

Color code : Blue colored strip

3.TMTD

Chemical Name : Tetramethyl thiuram di sulphide

Chemical Structure :

Molecular Weight : 240

Appearance : Half white oil treated powder

Specific gravity : 1.42

Melting point : 145 C

Ash content, % by mass : 0.5

Solubility : Soluble in methyl chloride, benzene

insoluble in H2O

Classification : Ultra fast accelerator

Color code : orange colored strip

1.MBTS

Chemical Name : Dibenzothiazole disulphide (MBTS)

Chemical Structure :

Molecular Weight : 332

Melting point : 170oC

7/29/2019 Compounding Technology

6/35

Ash content, % by mass : 0.5

Solubility : Soluble in chloroform. Insoluble in water

Classification : Semi ultra fast accelerator

Color code : Green colored strip

SPECIAL AGENTS

Anitoxidants

Antioxidants are the chemicals capable of reaching with the forces

(ozone, oxygen, heavy, light, weather and radiation) to prevent or slow down

the polymer breakdown, to improve the ageing qualities and to extend the

service life of the product. The antioxidant used as common proportions about

1.04.0 phr.

HS is mainly using as antioxidants. HS is a grade name, it is Quinoline

type. It is slightly staining , good for oxygen and heat, not so good for flexing

and ozone.

Antiozonant:

An antiozonant, also known as anti-ozonant, is a chemical compound that

prevents or slows down the degradation of material caused by ozone gas in the air

(ozone cracking) Antiozonants are used as additives to plastics and rubber, especially

in the tire manufacturing.

N,N -Dixylene- P-Phenylenediamine

Properties:

Appearance: Blue-brown flakes.

7/29/2019 Compounding Technology

7/35

PIGMENT:

Organic pigment powders:

Organic pigment powders are also useful in the coloring process and to

develop other specific properties in the rubber made products.

Titanium Dioxide:

These good qualities are: high refractive index, consistency in the size of the

particles, dispersibility, and high ultra violet ray resistance.

Florescent pigment:

These requirements are light stability, heat stability, resistance to bleed,

resistance to migration and required shade.

Molybdenum pigment:

Another type of pigments that is used in the rubber industry is Molybdenum

pigment. These pigmemts are light, heat stable and having bright color range from

bright red- orange to red- yellow.

Antistatic

An antistatic agent is a compound used for treatment of materials or

their surfaces in order to reduce or eliminate buildup of static electricity

generally caused by the triboelectric effect. Its role is to make the surface or the

material itself slightly conductive, either by being conductive itself, or by

absorbing moisture from the air, so some humectants can be used. The

molecules of an antistatic agent often have both hydrophilic and hydrophobic

areas, similar to those of a surfactant; the hydrophobic side interacts with the

surface of the material, while the hydrophilic side interacts with the air

moisture and binds the water molecules.

Internal antistatic agents are designed to be mixed directly into the

material, external antistatic agents are applied to the surface.

7/29/2019 Compounding Technology

8/35

Common antistatic agents are based on long-chain aliphatic amines

(optionally ethoxylated) and amides, quaternary ammonium salts (e.g.,

behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric

acid, polyethylene glycol esters, or polyols. Indium tin oxide can be used as

transparent antistatic coating of windows. It is also possible to use conductive

polymers, like PEDOT:PSS and conducting polymer nanofibers, particularly

polyaniline nanofibers.

Antistatic agents are also added to some military jet fuels, to impart

electrical conductivity to them and avoid buildup of static charge that could

lead to sparks igniting fuel vapors. Stadis 450 is the agent added to some

distillate fuels, commercial jet fuels, and to the military JP-8. Stadis 425 is a

similar compound, for use in distillate fuels. Statsafe products are used in non-

fuel applications.

Vulcanization

The term vulcanization or cross linking refers to a chemical process in

which the uncured, long chain rubber molecules are tied together into a three

dimensional elastic network by the insertion of crosslinks. Vulcanizations

usually refers to the use of sulfur cross-links, where as cross linking can

involve other chemical species i.e., peroxide etc.,

RAW RUBBER VERSUS VALCANISED RUBBER

PROPERTY RAW RUBBER VULCANIZED

RUBBER

Tensile strength 200 kg/cm2 2,000 kg/cm2

Elongation break (%) 1,200 800

7/29/2019 Compounding Technology

9/35

Rapidity of retraction Good Very good

Water absorption Large Small

Swelling in inorganic

solvents

Infinite (soluble) Large, but limited

Tackiness Marked Slight

Useful temperature

range

10 to 60 C -40 to 100 C

Chemical resistance Very poor Much better

Elasticity Very high (300 to

1,000%)

Low depending on

degree of vulcanization

Sulphur vulcanization

To improve the properties of rubber, it is compounded with some

chemicals like sulphur, benzoyl chloride, hydrogen sulphide etc., Most

important is addition of sulphur. The process consists in heating the raw rubber

wit sulphur to 100 to 140C the added sulphur combines chemically at the

double bonds of differ rubber springs. Vulcanization thus serves to stiffen the

material by a sort of anchoring and consequently, preventing intermolecular

movement a rubber springs. The extent of stiffness of vulcanized rubber

depends on the amount of sulphur added.

For e.g. tyre rubber may contain 3-50% sulphur, but a battery case

rubber may contains as much as 30% sulphur

7/29/2019 Compounding Technology

10/35

Vulcanization of raw rubber with sulphur as vulcanizing agents

7/29/2019 Compounding Technology

11/35

PEPTISERS

Incorporation of compounding ingredients is almost impossible unless

the raw material rubber is converted into a plastic stage. This is accomplished

by the action of mechanical shear forces which brings down nerve, molecular

weight of rubber thus making it more easily deformable which is essential for

proper blending of polymer and other ingredients. This process is known as

Mastication.

During this mastication, the rubber chains are ruptured ends of the chain

thus originated would remain active to recombine if not stabilized by some

means. This stabilization of the radicals during mastication is actuated with the

help of certain chemicals known as Peptiser. Since peptisers stablise the free

radical generated, the molecular break down is a permanent one molecular

weight comes down considerably and the incorporation of the other ingredients

is easier.

FILLERS:

CLASSIFICATION OF FILLERS:

The fillers are primarily classified as carbon blacks and light

colored filters. Among the light colored filters chemical composition is

primarily the basis for classification. For example one can list colloidal

silica, Calcium and aluminium silicate, alumina gel, Kaoline, Silica,

7/29/2019 Compounding Technology

12/35

talcum, chalk (calcium carbonate), metal oxide, like zinc oxide and

metal carbonates.

With each class of fillers, different degrees of activity are present.

Basically, most carbon blacks, colloidal silica, and most small particle

size silicates belong to the high-and medium activity fillers, while chalk

belongs to the inactive fillers.

CARBON BLACKS:

GENERAL CONSIDERATIONS AND CLASSIFICATION

The application of carbon black in rubber compounds is over a

hundred years old. Before 1872 only lamp black was utilized as a black

pigment. It was manufactured in China by the deposition of oil flames

onto china plates. After the discovery of the channel black in 1872 the

lamp black, which was only used as an extender, was successively

replaced by channel black. Even though the rubber reinforcement by

channel black was already discovered in 1911, it took until 1940 before

extensive scientific investigations of the mechanism of reinforcement

were undertaken. Because of these development efforts the principles of

the modern gas and oil furnace black manufacture were found , even

though SRF black had been developed already in 1922. Since

approximately 1950 the triumphal progression of the oil furnace black

began and since approximately 1965 the variety of furnace blacks was

extended to new special application areas and special properties. Since

7/29/2019 Compounding Technology

13/35

that time the manufacture of carbon black has been in hectic change.

From the numerous has not stabilized yet.

Aside from the flame, channel, gas and furnace blacks which are

produced by incomplete combustion of oil, coat tar products and natural

gas, the thermal, acetylene and arc blacks play a minor role. The latter

blacks are produced by thermal cracking of natural and coke gas,

acetylene or low molecular weight hydrocarbon gasses. Lately, it was

also attempted to produce carbon blacks from coal, graphite, and other

raw materials.

Carbon blacks are large scale technical products. World

production is roughly 2.5 million metric tons per year. It obtained this

position thanks to its rubber reinforcing properties which is the basis of

todays tire and rubber industry. With respect to reinforcing it has not

been possible to completely replace carbon blacks with other materials.

According to the production process, the U.S war Production

Board in 1943 classified carbon blacks as follows:

F- Furnace Blacks

C-Channel Blacks

T- Thermal Blacks

7/29/2019 Compounding Technology

14/35

Furnace black is today the most important of them. Channel

blacks have practically disappeared from the rubber industry. Thermal

blacks have in recent years been replaced by suitable furnace blacks

because of economic and ecological factors, often with suitable changes

in recipes. Reasons were increase in price of natural gas and costly air

pollution control installations.

The old classification of carbon blacks was based on their historic

names. The High Abrasion Furnace black (HAF) does not provide

high abrasive resistance according todays requirements and is hardly

ever used any longer for tire treads. The High Modulus Furnace black

(HMF) must be categorized today more likely as low modulus black. A

new scheme introduced a few years ago by ASTM tries to account for

todays situation less ambiguously. The type notations consist of a letter

indicating rate of vulcanization (N for normal, S for slow) and three

numbers, the first of which is an index of primary particle size. The use-

directed choice of carbon black types and amounts can be found in the

various chapters on Compounding of the various types of rubbe r: it

does not have to be discussed here in great detail.

FURNACE BLACK:

PREPARATION:

The furnace process the first continuous process for carbon black

production was introduced in 1922. It continued for 20 years with natural gas

7/29/2019 Compounding Technology

15/35

as feedstock and with SRF as the only product. Later, HMF and FF were

added. In 1943 the Oil-furnace process superseded the natural gas based

process. Today all Furnace Blacks are produced from liquid aromatic feedstock

that originates from petroleum fractionation, coal tar distillates or ethylene

crackers. Basically, the feedstock is pre0heated and burned in a reaction zone

with insufficient air supply. The temperature and other conditions are regulated

by burning in the reaction zone auxiliary gas or other secondary feed stocks.

The reaction is quenched b a water spray gas and the black is separated from

the steam/gas mixture in Zyclones or table filters and finally pelleted.

STRUCTURE:

The classification of carbon blacks proceeds according to their iodine

absorption (an index as to the size and activity of the surface) and their

structure that measure the extent of agglomeration and aggregation of primary

particles to form chain-and grape like structures similar aggregates represent

the smallest technically active units even after being mixed into the rubber, in

spite of a certain amount of degradation. The primary particles could be

regarded more as a hypothetic idea. The carbon The Carbon black structure

survives to some extent even in the vulcanizate and is characterized as the so

called F-value. Low structure blacks have been available for at least 25 years.

It has been possible to produce high- structure blacks since the middle 1960s.

Differences in surface and structure show up clearly in the technological

properties of the rubber. Higher iodine adsorption always goes with higher

7/29/2019 Compounding Technology

16/35

reinforcing action (higher activity). High black structure causes good

dispersion in the mixture, higher compound viscosity, and low die-swell with

smooth extrudate surface and with higher modulus, higher hardness and better

wear resistance of the vulcanizate. Low structure blacks give low dynamic heat

build-up, high tensile and tear strength, good crack growth resistance on

flexing and low stress vulcanizate (F-value) and the abrasion resistance when

one keeps rubber-active surface(A-value) constant. Improvement in abrasion

resistance are possible as long as the F-value can be increased.

Classification of Carbon Blacks according to ASTM-D 1765, Typical

Properties

Target Values

7/29/2019 Compounding Technology

17/35

ASTM

Designation

Iodine

Adsorption

No., D 1510

g /kg

DBP No.,

D2414

Cm3/100g

DBP No.,

Compressed

Sample,

D 3493

Cm3/100g

CTAB

D 3765

M2/g

Nitrogen

Adsorption

D 3037

M2/g

Tint

Strength

D 3265

IMPROVED CARBON BLACKS:

Since 1970 improve or new technology carbon blacks have been

developed by international modification of production variables. These blacks

present almost as good processing and vulcanization properties as conventional

types of higher activity and price category, they have therefore gained a large

portion of the market. N-375, N-339,and N-234 are the successful numbers of

these new types of carbon blacks in the USA as well as in Europe. It does not

seem impossible that conventional large-use products like N-220(ISAF) and N-

110 (SAF) will be completely replaced in a few years by new technology-

blacks. Many in-between types like N-242 (ISAF-HS), N-219(ISAF-LS) or N-

440 (FF) are already today commercially unobtainable. There is a trend if not

demand to rationalize among carbon blacks that are shipped in silo-can and

containers to large-scale users. A choice of furnace blacks can be seen in table-

2, resp. in ASTM-D 1765.

7/29/2019 Compounding Technology

18/35

PRODUCERS:

The main carbon black producers are: Ashland, Cabot, Columbian

Carbon, Continental Degussa, Huber and Philips. Cabot is the biggest of them,

followed by Degussa and Columbian Carbon.

Table: 2 (Continued) Classification of Carbon Blacks according to ASTM-D

1765, Typical Properties

ASTM

Designation

Target Values

Iodine

Adsorption

No.,D1510

g/kg

DBP No.,

D 2414

Cm3/100g

DBP.No.,

Compressed

Sample,

D 3493 ,

Cm3/100g

CTAB,

D 3765,

M2/g

Nitrogen

Adsorption

D 3037

M2/g

Tint Strength

D 3265

7/29/2019 Compounding Technology

19/35

THERMAL BLACKS:

N539

N550

N630

N642

N650

N660

N683

N754

N762

N765

N774

N787

N907

N908

N990

N991

43

43

36

36

36

36

35

24

27

31

29

30

111

121

78

64

122

90

133

58

65

115

72

80

34

34

43

35

84

88

62

62

87

75

57

57

86

62

74

40

38

41

42

38

37

38

35

39

29

29

33

29

32

9

8

41

42

38

37

38

35

37

28

31

29

30

11

9

7

7/29/2019 Compounding Technology

20/35

Thermal blacks are generally produced from natural gas in preheated

chambers without air. They are inactive, improve the tensile strength of the

vulcanizates very little, but give only moderate hardness at high loading, and

good processing and dynamic properties . Thermal blacks have in recent years

been in short supply and expensive, but recently Cancarb has increased its

capacity enormously . Their use has been limited to applications (highly loaded

CR-parts: X-LPE, etc.).

CHANNEL BLACKS:

Till the end of world War II the channel blacks were the most important

reinforcement blacks. They have been completely replaced by the

abovementioned furnace blacks that had been developed during the last years

of the war. The furnace blacks in SBR give much better abrasion resistance

than the comparable channel blacks. The channel blacks are more acidic (pH-

value of about 5 compared to furnace black 6.5-10) than the other blacks. They

therefore cause a more or less strong vulcanization retardation.

The Channel blacks are prepared by partial combustion of gaseous

hydrocarbons, mostly gas, through thousands of single burners, are deposited

on cooled steel rings and scraped off and collected.

OTHER CARBON BLACKS:

Aside from the main classes of carbon blacks, one can mention also:

ACETYLENE BLACKS:

7/29/2019 Compounding Technology

21/35

Acetylene Blacks, that are prepared by thermal decomposition of

acetylene, are outstanding because of their high electric conductivity. They are

advantages for many applications where high conductivity is necessary,

respectively where electrostatic charge must be avoided, for example rolls,

tanker hoses, containers for powdered materials. They are frequently today

replaced by conductive furnace blacks.

FLAME BLACKS:

Flame Blacks, prepared from combustion of liquid fuels give at high

loadings good processing properties with attractive dynamic properties. They

are today increasingly exchanged for furnace blacks, especially those with high

structure.

ELECTRIC ARE CARBON BLACKS:

Electric are Carbon Blacks were byproducts from the acetylene

production in the electric are. They are not being produced any longer.

Properties of fillers

TEST

PARAMETERS

ISAF HAF FEF GPF SRF

Moisture

content%

0.5 0.6 0.4 0.5 0.8

Ash content % 0.2 0.2 0.2 0.2 0.2

Iodine 120.6 82.6 43 36 30.7

7/29/2019 Compounding Technology

22/35

adsorption

(g/kg)

DBP absorption

(cc/100g )

115 102.9 121.5 90 72.2

Sieve residue

(325 mesh)

0.036 .008 .032 .040 .036

Bulk density

(g/ml)

- .35 .35 .411 -

Pour density

(g/lit)

340 360 350 420 502

Fitness

content%

2.2 7.0 2.0 2.0 4.1

pH value 7.2 7.9 7.0 7.2 -

NON-BLACK FILLERS:

ACTIVE NON-BLACK FILLERS:

PREPARATION:

The highly active, light colored fillers are, chemically, Silicas (Silicic

acids). They can be manufactured by two methods: Solution Process or

Pyrogenic Process (fumed Silica).

Those most important for the rubber industry are made by precipitation:

Alkalisilicate solutions are acidified under controlled conditions. The

7/29/2019 Compounding Technology

23/35

precipitated silicic acid(silica) is washed and dried. Depending on the condition

during preparation , the silica filler is more or less active. The products with

highest activity are pure silicic acids (silicas) with large specific surfaces. Ca-

silicates are a little less active but easier to process . Al-silicates have in this

series the lowest activity.

In the preparation products are quenched immediately after coming out

of the burner. One obtains very finely divided silica that is important as filler

for example for Q. For the normal types of rubber, pyrogenic silica is too active

and too expensive.

PURE SILICAS:

The pure silicas represent very active fillers. With Comparable specific

surface areas one obtains vulcanizates that compared to reinforcing carbon

blacks, show nearly equal tensile strength and tear resistance, while abrasion

resistance is 15-20% lower. Strain values and hardness are usually lower. On

the other hand, electrical behavior is somewhat better; Silicas with highest

activity, because of their large surface area give mixtures of high viscosity that

makes processing more difficult that can be adjusted by the use of filler

activators.

SILICATES:

Calcium Silicates, that may be called semi-active fillers, give even at

high loadings, soft and elastic vulcanizates . Because of their low activity, they

7/29/2019 Compounding Technology

24/35

process better than the silica fillers. The aluminum silicates are less active than

the calcium silicates and do not produce properties achieved with silicas or

calcium silicates.

CHALK:

Among the different types of chalk one differentiates between milled,

washed and precipitated products, It should be mentioned that it is possible

under certain suitable conditions to precipitate very fine calcium carbonate that

has very small particles and is semi-reinforcing filler.

The different types of chalk mentioned above are different in color and

also in their effect on processing, extrudability and vulcanization. These

differences are not very extensive.

PROPERTIES OF NON-BLACK FILLERS

TEST

PARAMETERS

PPT SILICA FUMED

SILICA

CAL.CARBONATE

Moisture content,

%

4.0 1.21 0.28

BET surface area

(m2/g)

170 200 12.0

Bulk density

(g/ml)

0.13 0.04 0.037

7/29/2019 Compounding Technology

25/35

PEPTISERS

Incorporation of compounding ingredients is almost impossible unless

the raw material rubber is converted into a plastic stage. This is accomplished

by the action of mechanical shear forces which brings down nerve, molecular

weight of rubber thus making it more easily deformable which is essential for

proper blending of polymer and other ingredients. This process is known as

Mastication.

During this mastication, the rubber chains are ruptured ends of the chain

thus originated would remain active to recombine if not stabilized by some

means. This stabilization of the radicals during mastication is actuated with the

help of certain chemicals known as Peptiser. Since peptisers stablise the free

radical generated, the molecular break down is a permanent one molecular

weight comes down considerably and the incorporation of the other ingredients

is easier.

PROCESSING OILS

Processing oils in rubber formulation primarily serve as processing aids.

These oils are used as extenders to reduce the cost of rubber compounding.

CLASSIFICATION

TYPE OF OIL

(PLASTICIZERS)

VISCOSITY

GRAVITY

CONSTANT (VGC)

SOLUBILITY

PARAMETER

(CAL/CM2)

7/29/2019 Compounding Technology

26/35

Paraffinic oil 0.73-0.82 9.2

Naphthenic oil 0.82-0.85 8.2

Aromatic oil 0.95-1.05 7.2

Advantage of Peptisers

Ultimate viscosity of the matrix is considerably reduced. Mixing leads to better dispersion which helps in further processing Total mixing time is sufficiently process Energy requirement in the process is less.

Paraffinic oil

They have straight or branched chains and the chain length increases,

the viscosity also increases and has higher boiling point. Widely used in butyl

and EPDM rubber.

Major features are

High stability and good color can be used in coloured rubber. Highest flash point High temperature processing Excellent low temperature flexibility

DOP oil

7/29/2019 Compounding Technology

27/35

Di-octyle phthalate (DOP) is a high performance primary plastizer. DOP

is a plasticizer that perfects the products and an ideal raw material for an

extensive range of application.

DOP is a stable colourless oily liquid with a characteristic odour. It

possess flexibility, extremely low volatility, good electrical characteristic and

stability to UV light. It is soluble in common organic solvents and mineral oil

but has a very low stability in water good resistance to hydrolysis.

In styrene-butadiene rubber (SBR) the tensile strength remains

approximately constant, while the modulus slightly increases (matching cure)

when the vulcanization time is too long leading to overcure, an important and

sudden reduction of break elongation occurs, which was not noticed in the case

of natural rubber.

Aromatics oil

Aromatics oil blending component products are mixtures of (mainly unsaturated) C9

to C15 components. They originate from the high temperature cracking of petroleum

fractions and are separated out of pyrolysis gasoline (pygas) by distillation during the

production of benzene.Aromatic Oil can be blended into bunker fuel or fluxant.

Aromatic Oil may also be used as a source for naphthalene or mixtures of naphthalene

and methylnaphthalene for concrete plasticizers, phthalic anhydride and insecticides.

Naphthenic oils

In the manufacture of grease, naphthenic base oils in most cases have great

advantages compared with paraffinic oils. This is a generally recognised fact in many

7/29/2019 Compounding Technology

28/35

parts of the world. The basis for these advantages lies in the favourable solubility

properties of naphthenic oils. Hans Bckstrm here comments on different ways of

measuring solubility properties and the way these properties are connected with the

consumption of soap during grease making, an important economic consideration.

Test results show that different solubility concepts, such as aniline point, VGC and

solubility parameters do not always correlate. One method alone perhaps does not

give all the information needed for all applications.

7/29/2019 Compounding Technology

29/35

VULCANIZATION BY ACCELERATORS

Acceleration of vulcanization is done by the accelerator activators like

ZnO and Stearic acid. Organic accelerators have gained importance in rubber

industries because of their following characters.

They increase productivity by reducing the cure cyclic because theycan increase rate of cross link reaction considerably with sulphur.

Combination of two or more accelerators can produce synergesticeffect, providing better result.

By the use of organic accelerator, sulphur can be used moreefficiently to form the need based cross link formation.

Improves the ageing property of rubber and also increases

the plateau effect.

The initial step in vulcanization is the reaction of sulphur with zinc

salt of the accelerator to give a Zinc perthio salt XSxZn SxX.

Where x is a group derived from the accelerator. This salt reacts with

the rubber, hydrocarbon RH to give a rubber bound intermediate and

a perthio accelerator group. Which with further Zinc Oxide will form

a Zinc perthiosalt of cover sulphur content.

XSxZnSx + RH

7/29/2019 Compounding Technology

30/35

In this way each module of accelerator gives rise to a series of

intermediate of varying degree of polysulphidity.

Culcanization conditions

In vulcanization processes, consideration must be made for the

difference in thickness of the objects involved, vulcanization

temperature and the thermal stability of the rubber compound.

Terms involved in Culcanization process

Scorch

Scorch is a premature vulcanization in which the stock becomes

partly vulcanized before the product is in its final form and ready for

vulcanization, it reduces the plastic properties of the compound,

during processing and the amount of time the compound is exposed

to elevated temperatures. The period of time before vulcanization

starts is generally to as SCORCH TIME.

RATE OF CURE

THE Rate of cure is the rate at which cross-linking and the

development of the modulus of the compound occur offer the scorch

point. During the curing step, cross link are introduced, which

connect the long polymer chains of the rubber together. As the more

cross links are introduced, and the modulus of the compound

increases. The rate of curve is an important vulcanization parameter,

it determines the time of compound must be cured is called the cure

time.

7/29/2019 Compounding Technology

31/35

State of cure

As the cross-linking or vulcanization proceeds, the modulus of

the compound increases to various, state of cure. The most

important state of cure is so-called Optimum.

Over cure

A cure which is longer than optimum is an Over cure due to the

over cure the modulus and tensile strength decreases an elongation

fall.

FILLERS

Fillers are thermoplastic and thermosets may be inert materials that

serve to reduce the resin cost and improve process ability or dissipate heat in

exothermic thermosetting rections and also filler in chosen for rubber

compound because of two primary reasons.

1. To improve vulcanization properties2. To reduce the cost of a compound

REINFORCING FILLERS

Reinforcing fillers are used to improve some mechanic property such as

modulus, tensile strength, abrasion resistance and fatigue strength. For

example, particular fillers such as carbon black or silica are widely used to

improve the strength and abrasion of commercial elastomers.

Carbon black

7/29/2019 Compounding Technology

32/35

Carbon blacks are essentially elemental carbon and composed of

aggregated particles. The particles are graphite in structure and are of colloidal

dimensions.

The carbon atoms in the particle are in layer planes which, by parallel

alignment and overlapping, give the particles their semi graphite in nature. The

outer layers are more graphite than those in the centre. The particles range in

size from 100 nm to 400 nm in diameter smaller ones being less graphitic.

MANUFACTURE

Carbon blacks are produced by converting either liquid or gaseous

hydrocarbons to elemental carbon and hydrogen by partial combustion or

thermal decomposition

Application

Carbon black is universal reinforcing filler used in rubber compounds.

Higher reinforcing gives better physical properties like tensile, flexing, tear

resistance and abrasion resistance. Normally three properties of carbon black

are considered in choosing the type of carbon and these are

1. Particle size2. Structure3. Surface areaThe degree of reinforcement increases with decrease in a particle size

i.e., smaller particles give better reinforcement. Higher Mooney but less

7/29/2019 Compounding Technology

33/35

scorches safety having a higher surface area. Carbon black structure has

more effect on the modulus, harness and extrusion die swell.

High structure and higher loading gives higher mooney, higher

modulus and also affect the hardness. For lower structure it is reverse.

NON CARBON BLACK OR WHITE FILLERS

Non black fillers which are used to reduce the cost, to improve

processing by reducing nerve and to reinforce the polymer by

increasing hardness, tensile strength and tear resistance. Abrasion

resistance and other properties in the production of white or coloured

compounds.

They are usually classified as

Fillers used mainly used to reduce cost. Semi reinforcing fillers. Reinforcing fillers used to achieve high

performance in non-black products.

1. PRECIPITATED CALCIUM CARBONATEPrecipitated whitening may be products of water softening processing

are produced from solution of calcium salt, with particle sizes from about 20

um to 50 nm. As semi-reinforcing fillers, high loadings can be used in

mechanical goods and proofing to give low cost products of goods appearance

with moderate hardness and better physical properties than the ground

materials.

7/29/2019 Compounding Technology

34/35

2. ALUMINIUM SILICATEThis fine filler is produced by precipitation. The average particle

size 150 nm specific surface area 50-270m pH of aqueous

suspension9-11 density 2000-2450kgm-3 (depending on the content of

) Moisture content about 6% and the content of bound water 11-

15%.

These are the characteristic properties of hydrated aluminium

silicate which often contains large amounts of Na2O. it is added mainly

to compounds for the production of soles and light coloured consumer

goods. It may be added in large amounts especially to natural rubber

where it improves the extraction properties and calendaring without

reduce the final properties of the rubber. It also increases the resistance

of the rubber to steam and it is used in compounds for electro insulation

purpose. At very high loading it affect vulcanization by its alkalinity and

at normal loading levels it affects the vulcanization only slightly.

FUMED SILICA

Furned or pyrogenic silica is silicon dioxide, containing less than 2%

combined water, usually prepared by burning volatile silica compounds. These

silica are highly reinforeing fillers of very small particles size, giving high

tensile strength, tear resistance, and abrasion resistance, particularly to silicon

rubbers. The retarding effect on cure in organic rubbers requires increased

amounts of accelerators.

7/29/2019 Compounding Technology

35/35

CHEMICAL PLASTICIZERS OF PEPTIZING AGENTS

Certain peptizers added to reduce the viscosity of rubber and to permit

easy processing. Peptizers are giving popularity due to the following reasons.

Energy saving Easier mixing Controlled and consistent viscosity Improved production Reduce rear and tear machinery Improved green tack of unvulcanized components

There are two types of peptizers

a. PCTP (penta chloro thio phenol)b.

DBDS (Dibenzoyl amide diphenyl disulphide)