In Situ Precipitation for Preparation of NR Silica Composites

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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

  1. 1. IN SITU PRECIPITATION FOR PREPARATION OF NR-SILICA COMPOSITES Syed Mohammed Sajl Semester 7 B Tech – Polymer Science & Engineering
  2. 2. INDRODUCTION 1. Silica 2. Production of Silica 3. Natural Rubber (NR) 4. Precipitated Silica Filled NR Composite 5. In Situ Precipitation of Silica Filled Composite from Centrifuged Latex 6. Determination of Silica Content in Sample 7. Properties 8. Conclusion 10/6/2013 Elective Seminar 2
  3. 3. 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. 10/6/2013 Elective Seminar 3
  4. 4. 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. 10/6/2013 Elective Seminar 4
  5. 5. • 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) 10/6/2013 Elective Seminar 5
  6. 6. • 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. 10/6/2013 Elective Seminar 6
  7. 7. 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 10/6/2013 Elective Seminar 7
  8. 8. SEM Photographs of the Tear Fractured Surfaces of Rubber Compounds 10/6/2013 Elective Seminar 8
  9. 9. 10/6/2013 Elective Seminar 9 Rubber Rubber Rubber Rubber OSi O OSi O OSi O OSi O OSi O OSi O OSi O O O OSi O Figure: Natural Rubber – Silica Composite
  10. 10. • 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. 10/6/2013 Elective Seminar 10
  11. 11. 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 10/6/2013 Elective Seminar 11
  12. 12. In Situ Precipitation – Schematic Representation 10/6/2013 Elective Seminar 12 Filter Centrifuged Latex keeping the Mixture 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 addition of saturated solution of Ammonium Chloride.
  13. 13. 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. 10/6/2013 Elective Seminar 13
  14. 14. Silica Content during the Precipitation in Concentrated Latex 10/6/2013 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%
  15. 15. 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. 10/6/2013 Elective Seminar 15
  16. 16. Variation of Tensile Strength with Concentration of Silica 10/6/2013 Elective Seminar 16 10 15 20 25 30 35 0 10 20 30 40 TensileStrength(MPa) Concentration of Silica (phr)
  17. 17. Variation of Elongation at Break with Concentration of Silica 10/6/2013 Elective Seminar 17 0 400 800 1200 0 10 20 30 40 50 ElongationatBreak(%) Concentration of Silica (phr)
  18. 18. Variation of Tear Strength with Concentration of Silica 10/6/2013 Elective Seminar 18 0 20 40 60 80 0 10 20 30 40 50 TearStrength(N/mm) Concentration of Silica (phr)
  19. 19. Variation of Reduced Stress with Concentration of Silica 10/6/2013 Elective Seminar 19 0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0 10 20 30 40 50 ReducedStress Silica Content (phr)
  20. 20. 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 modulus10/6/2013 Elective Seminar 20
  21. 21. • 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 10/6/2013 Elective Seminar 21
  22. 22. 10/6/2013 Elective Seminar 22 Download this Slideshow: At SlideShare
  23. 23. 10/6/2013 Elective Seminar 23

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