Short Description related to the rubber filler properties and Rubber filler types ( Reinforcing fillers, Semi- reinforcing fillers and Non-reinforcing fillers). e.g.:- Carbon Black, Silica, Calcium Carbonate, Clay and Miscellaneous Fillers

1. Created By : D.W.W.Sewwandi
Sp. Material Science and Technology
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2.  Characteristics of a filler that determine the
properties a filler will impart to a rubber
compound are,
1. Particle size
2. Surface are
3. Structure
4. Surface Activity
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3. 1. Particle Size
 Size of the filler particle should not exceeds
the polymer interchange distance. If so it can
contribute to elastomer chain rupture on
flexing or stretching.
 According to the particle size , there are
generally three types.
Diluents, Semi-reinforcing , Reinforcing filler
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4. 1. Particle Size
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Particle Size (nm) Description
1000 – 10 000 Used primarily as diluents, no significant
effect on rubber propertes
100 - 1000 Semi reinforcing fillers ,Improve strength
and modulus properties
10 - 100 Reinforcing fillers , significantly improve
rubber properties

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Figure 01:- Classification of fillers

6. 2. Surface Area
 Particle size is generally the inverse of surface
area.
 For reinforcement, filler must make intimate
contact with elastomer chains
 Fillers with high surface are have more
contact are available , and thus have a higher
potential to reinforce the rubber chain.
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7. 3. Structure
 Fillers effective shape is more importance
than the shape of an individual particle
 Reinforcing fillers such as Carbon black and
Precipitated Silica have generally round
primary particle but function as anisometric
acicular aregates.
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8. 3. Structure
 The more aggregate deviate from a solid
spherical shape and the lager its size, the
higher its structure.
 The higher its structure, the greater its
reinforcing potential
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9. 4. Surface Activity
 The specific activity of the filler surface per
cm2 of filler- elastomer interface is
determined by the physical and chemical
nature of the filler surface in relation to that
of the elastomer
 Non polar fillers are suitable to nonpolar
elastomer and polar filler are suitable with
polar elastomer.
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10. • Carbon Black
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Figure 02:- Carbon black particles
available in different sized

11. Carbon Black
 This is a material of major significance to the
rubber industry.
 Carbon black is essentially elemental carbon
in the form of fine amorphous particles.
 Individual round carbon black particles form
aggregated, which may be clumps or chains of
various sizes and configurations.
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12. Carbon Black
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Table 01:- Classification of Carbon black according to ASTM standards

13. Carbon Black
 When Carbon Black is compounded with
rubbers, tensile strength, tear strength,
modulus and abrasion resistance are
increased
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14. Clays
 manufactured from naturally occurring hydrated
aluminium silicates.
 The particles of clays are hexagonal shaped platelets.
 The type of clays used by the rubber industry are
known to the clay industry as kaolin deposits of a
hydrous aluminium silicate, known as kaolinite.
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15. Clays
 Four types
1. Soft clays
2. Hard clays
3. Calcined clays
4. Treated Clays
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16. Clays
 Four types
1. Soft clays - semi-reinforcing, have lower
modulus, tensile strength and abrasion
resistance than hard clays
2. Hard clays - gives an expected higher level
of reinforcement than that found for the
soft clays
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17. Clays
3. Calcined clays - have been heat treated to
remove the combined water, improve the
electrical resistance of rubber compounds.
4. Treated Clays - Treatment of water-
washed hard china clays with silanes with
pendant amino or mercapto groups
enables them to give improved
reinforcement to rubber compounds.
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18. Silica
 Three specific types
1. Ground mineral silica
2. Precipitated silica
3. Fumed or pyrogenic silica
18Figure 03:- Precipitated silica

19. Silica
1. ground mineral silica
◦ generally available below 300 mesh in size (5 m2/g)
◦ used as a cheap heat resistant filler for a variety of
compounds.
◦ There is no effect on the rate or state of cure
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20. 2. precipitated silica
◦ Produced by the controlled neutralization of
dilute sodium silicate by either concentrate
sulfuric, hydrochloric, or carbonic acid.
◦ particle sizes in the range of 10-40 nm.
• The surface of silica is strongly polar in
nature
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21. 2. precipitated silica
◦ has a chemically bound water content of 25% with
an additional level of 4-6% of adsorbed water.
◦ The use of additives to make the surface of
precipitated silica less hydrophilic and more
“rubberphilic” facilitates incorporation, dispersion,
and more intimate filler-elastomer contact during
compounding additives.
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22. 2. Precipitated silica
◦ has a chemically bound water content of 25% with
an additional level of 4-6% of adsorbed water.
◦ The use of additives to make the surface of
precipitated silica less hydrophilic and more
“rubberphilic” facilitates incorporation, dispersion,
and more intimate filler-elastomer contact during
compounding additives.
◦ Addives uded -silanes, titanates and zirconates
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23. 3. Fumed Silica
◦ prepared by burning volatile silicon compounds
such as silicon tetrachloride.
◦ contains less than 2% combined water and
generally no free water.
◦ not generally used in conventional rubber
compounding but find application with silicone
rubber.
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24. Calcium Carbonate
Several types available.
◦ Prepared Ground Limestone - particle size less than 100 mesh,
used as an inertdiluent and cheapening filler for rubber
compounds
• Ground Chalk, Whiting - white powder produced inparticle sizes
down to 30 nm, used as a diluent filler giving moderate hardness
and a reasonably high resilience at high loadings.
• Precipitated Whiting - particle sizes is available, from 20 μm to
50 nm, semi-reinforcing resulting in compounds with better
physical properties than with use of ground whiting
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25. Miscellaneous Fillers
◦ Magnesium Silicate (Talc)- prepared by grinding of naturally
occurring deposits, Very finely ground materials are used as
reinforcing fillers, Larger particle size products are used in
antistick applications.
• Mica Powder- Washed and ground, natural mica of 200-300
mesh acts as a laminar filler, giving good heat resistance and
low gas permeability.
• Titanium Dioxide- because of its cost, titanium dioxide is
usually only used as a whitening agent for rubber compounds.
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26. Miscellaneous Fillers
◦ Barium Sulphate - can be supplied ground directly from the
mineral, or from the precipitation of barium salts. ground
natural barium sulfate, is used in acid resistant compounds
because of its inertness, and as a high gravity filler where
weight is desired.
◦ Calcium Sulphate - Produced by grinding from gypsum, or
hydrated plaster of Paris
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27. 1. Simpson, R.B., (ed.) Rubber Basics. Shropshire:Rapra
Technology Limited, 2002.
2. Ciullo, P.A., Hewitt, N; The rubber formulary. New
York: Noyes publications, 1999.
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