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Silica Production of Silica Natural Rubber (NR) Precipitated Silica Filled NR Composite In Situ Precipitation of Silica Filled Composite from Centrifuged Latex Determination of Silica Content in Sample Properties Conclusion
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IN SITU PRECIPITATION FOR
PREPARATION OF NR-SILICA COMPOSITES
Syed Mohammed SajlSemester 7
B Tech – Polymer Science & Engineering
INDRODUCTION
1. Silica2. Production of Silica3. Natural Rubber (NR)4. Precipitated Silica Filled NR Composite5. In Situ Precipitation of Silica Filled
Composite from Centrifuged Latex 6. Determination of Silica Content in Sample7. Properties8. Conclusion
04/11/2023 Elective Seminar 2
1. SILICA
• Silica is a crystalline compound.• There are two types of silica i.e.,
Natural Silica and Synthetic Silica.• Natural Silica is non-reinforcing and
has been used as a filler.• The synthetic ones are reinforcing and
their particle sizes as small as the carbon black besides an extremely reactive surface.
04/11/2023 Elective Seminar 3
2. PRODUCTION OF SILICA
• Acidification of alkali silicate solutions under controlled conditions Produces precipitated silica. Na2SiO3 + HCl 2NaCl + H20 + Si02
• Precipitated silica is silicon dioxide containing about 10-14% water.
• Particle size is in the range 1-40 nm.
04/11/2023 Elective Seminar 4
• Natural rubber (NR) is cis 1,4polyisoprene.
• Rubber is separated from the latex by coagulation usually by acidification.• The coagulum is then processed into different marketable forms.
3. NATURAL RUBBER (NR)
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• The molecular weight of polymer ranges from 200,000 to 600,000.
• Latex contains more than 90% of the Hydrocarbon, cis-I,4- polyisoprene, naturally occurring resins, proteins, sugars etc.
• Natural rubber is a versatile and adaptable material.
• An ammonia solution can be used to prevent the coagulation of raw latex while it is being transported from its collection site.
04/11/2023 Elective Seminar 6
4. PRECIPITATED SILICA FILLED NATURAL RUBBER
COMPOSITES• Precipitated Silica, is one of the most promising
alternatives to carbon black.• Silica reduces the rolling resistance and hence
fuel consumption, in case of tyres.• The silica enables the production of high-
performance tyres with low rolling resistance.• The main characteristic - particle size-surface
area• Silica has hydroxyl groups - filler agglomeration • Commercial nano silica is good but difficult to
incorporate
04/11/2023 Elective Seminar 7
SEM Photographs of the Tear Fractured Surfaces of Rubber
Compounds
04/11/2023 Elective Seminar 8
04/11/2023 Elective Seminar 9
Rubber
Rubber
Rubber
RubberOSi
O
OSi
O
OSi
O
OSi
O
OSi
O
OSi
O
OSi
O
OO
OSi
O
Figure: Natural Rubber – Silica
Composite
• The problem in silica is the difficulty in incorporation, as Silica is hydrophilic and rubber is hydrophobic in nature.
• The rubber-silica interaction can be improved by using silane coupling agents.
• The most widely used compound is silica is Bis (3-triethoxy silyl propyl) tetra sulphide (TESPT) or Si 69.
• The production of precipitated silica starts with the reaction of an alkaline silicate solution with a mineral acid.
• Sulfuric acid and sodium silicate solutions are added simultaneously with agitation to water. Precipitation is carried out under alkaline conditions.
04/11/2023 Elective Seminar 10
5. IN SITU PRECIPITATION OF SILICA FILLED COMPOSITES FROM
CENTRIFUGED LATEX• Latex filtered and Stabilized.• Mixed with 60% Sodium Silicate • Ammonium Chloride Solution added.• 2% Acetic Acid added to Coagulate the latex.• The coagulum is washed with water • It is then Dried at 70 C for 48hrs
Na2SiO3 + 2 NH4Cl 2 NaCl + 2 NH3 + H2SiO3
H2SiO3 H2O + SiO2
• Ammonia evolved is analyzed -- confirms the occurrence of the reaction
04/11/2023 Elective Seminar 11
In Situ Precipitation – Schematic Representation
04/11/2023 Elective Seminar 12
Filter Centrifuged Latex
keeping theMixture for 24
hours
Stabilized with Non-ionic Stabilizer
Add Sodium Silicate and stirred for one
hour.
Silica was precipitated by
drop wise addition
Latex was coagulated as crumbs by the addition of 2%
Acetic Acid.
Crumbs were washed with water
till the washings were neutral
It is dried in an air oven at 70C for 48
hours
Precipitation was repeated with varying amounts of Sodium Silicate
to prepare Natural Rubber Silica Composites
drop wise additionof saturated solution
of Ammonium Chloride.
6. DETERMINATION OF SILICA CONTENT IN THE SAMPLE
• The silica content of the dried coagulum samples is determined by igniting a known weight of the sample in a previously weighed silica crucible in a muffle furnace.
• The temperature of the furnace is kept at 550°C for five hours time.
• It is then cooled.• From the weight of the ash the loading of
silica and the loss of the silica was calculated.
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Silica Content during the Precipitation in Concentrated
Latex
04/11/2023 Elective Seminar 14
SAMPLE SILICA CONTENT EXPECTED (phr)
SILICA CONTENT DETERMINED (phr)
M-1 1.002 1.002
M-2 2.004 2.001
M-3 3.007 3.002
M-4 4.009 4.000
M-5 5.012 5.003
M-10 10.024 10.015
M-20 20.048 19.942
M-30 30.072 28.017
M-40 40.096 36.524
M-50 50.120 42.258
• The percentage moisture content of all samples was found to be less than 0.01%
7. PROPERTIES OF COMPOSITES PREPARED FROM THE SILICA MIXES OF
DIFFERENT COMPOSITIONS • Tensile strength of the composites increases
with the rise of in situ precipitated silica content.
• Tear strength increases proportionally with increase in silica up to 20 phr,above 20 phr it shows very small change.
• The reduced stress values increased with increase in concentration of silica.
• Hardness increases as the silica content increases.
• Resilience decline with increase in silica content.
• Abrasion resistance improves with the in situ silica content.
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Variation of Tensile Strength with Concentration of Silica
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0 5 10 15 20 25 30 35 40 4510
15
20
25
30
35
Concentration of Silica (phr)
Tensi
le S
trength
(M
Pa)
Variation of Elongation at Break with Concentration of Silica
04/11/2023 Elective Seminar 17
0 5 10 15 20 25 30 35 40 450
400
800
1200
Concentration of Silica (phr)
Elo
ngati
on a
t B
reak (
%)
Variation of Tear Strength with Concentration of Silica
04/11/2023 Elective Seminar 18
0 5 10 15 20 25 30 35 40 450
20
40
60
80
Concentration of Silica (phr)
Tear
Str
ength
( N
/mm
)
Variation of Reduced Stress with Concentration of Silica
04/11/2023 Elective Seminar 19
0 5 10 15 20 25 30 35 40 450.0000
0.0100
0.0200
0.0300
0.0400
0.0500
Silica Content (phr)
Reduce
d S
tress
8. CONCLUSION
• Silica can be incorporated in NR Latex by In-situ precipitation procedure to prepare rubber composites.
• The vulcanizates prepared by this novel technique show superior mechanical properties compared to those prepared from conventional silica.
• The latex precipitated silica is found to have better rubber- filler interaction compared to commercial silica
• Enhanced rubber- filler interaction• Improved tensile and tear strength• Improved tensile modulus04/11/2023 Elective Seminar 20
• Silica of any desired concentration can be incorporated in to the dry rubber directly or indirectly.
• Ageing resistance and permeability showed improved values.
• This method is simple and cost reducing.• Improved filler distribution
04/11/2023 Elective Seminar 21
04/11/2023 Elective Seminar 22
Download this Slideshow:At SlideShare
04/11/2023 Elective Seminar 23