Precipitated silica

About: Precipitated silica is a research topic. Over the lifetime, 1401 publications have been published within this topic receiving 20992 citations.

Effects of silica based fillers, surface treatment and curing method on mechanical properties of silica/unsaturated polyester composites

Abstract: This study examined the effects of silica based fillers, precipitated silica (PSi) and silica from fly ash (FASi), and a silane treatment on the mechanical and morphological properties of unsaturated polyester (UPE) resins cured by conventional thermal (CV) and microwave (MW) curing methods. The curing curves for unfilled UPE in both curing systems exhibited S-shaped character. The curing curves for PSi/UPE composites were different from those of the FASi/UPE composites due to differences in the number of hydroxyl groups on the silica surfaces. MW curing could reduce the curing time in a greater magnitude than CV curing, suggesting that microwaves are more suitable for curing polymers containing silica based fillers. The percentage conversion of silica/UPE composites increased with increasing filler content. The flexural modulus, hardness and impact strength increased with increasing filler content for both silica fillers. The presence of silica filler in the UPE resulted in a sudden decrease in flexural strength, even though the strength improved slightly with increasing silica content. The overall mechanical properties of the UPE composites were improved considerably using 3-glycidoxypropyl thimethoxysilane (KBM-403) on a silica surface.

Mechanism of silica reinforcement in CPE/NR blends by the use of rheological approaches

Abstract: Blends of elastomeric chlorinated polyethylene (CPE) and natural rubber (NR) at blend composition ratio of 80/20 CPE/NR with various precipitated silica loadings were prepared By the use of rheological approaches, a mechanism of silica reinforcement was proposed Results obtained reveal that the viscoelastic behavior of blends is influenced remarkably by loadings of silica A cure promotion phenomenon is found as silica is loaded due probably to the strong silica-CPE interaction and/or a reduction in curative absorption on silica surfaces A strong Payne effect is observed, which is increased by a rise in silica loading, implying a formation of pseudocrosslink via a physical interaction, which could be disrupted at high strain of deformation The proposed mechanism of silica reinforcement based on the formation of pseudocrosslink is validated by the deactivation of silanol groups on silica surfaces using silane-coupling agents The bis-(3-triethoxysilylpropyl) tetrasulfane (Si-69) is found to be more effective in suppressing the pseudocrosslink than 3-thiocyanatopropyl triethoxy silane (Si-264), which is thought to be the result of its larger amount of alkoxy groups at a given silane loading © 2007 Wiley Periodicals, Inc J Appl Polym Sci, 2008

Precipitated silica having a specific pore size distribution

Abstract: Preparation of precipitated silicic acid comprises (a) subjecting an aqueous solution of an alkali- and/or earth alkaline silicate and/or an organic or inorganic base; (b) simultaneously adding an alkali- and/or alkaline-earth silicate and an acidifying agent to increase the viscosity; (c) terminating the reaction after 35-85 minutes; (d) simultaneously adding an alkali- and/or alkaline-earth silicate and an acidifying agent to attain a solid content; (e) stirring the obtained suspension; (f) adjusting the pH by adding the acidifying agent; and (g) filtering and (h) drying. Preparation of precipitated silicic acid comprises: (a) subjecting an aqueous solution of an alkali- and/or earth alkaline silicate and/or an organic or inorganic base, where the subjected mixture exhibits the alkali number of 20-40; (b) simultaneously adding an alkali- and/or earth alkaline silicate under stirring at 55-85[deg]C and an acidification agent to increase the viscosity of the mixture; ( (c) terminating the reaction after the addition of mixture that takes place for 35-85 minutes, preferably after reacting the temperature of step (b); (d) simultaneously adding an alkali- and/or alkaline-earth silicate and an acidifying agent under agitation at 55-85[deg]C, to attain a solid content of 90-140 g/l; (e) stirring the obtained suspension for 1-120 minutes at 80-98[deg]C; (f) adjusting the pH of the solution to 2.5-5 by adding the acidifying agent; (g) filtering; and (h) drying. Independent claims are included for: (1) a precipitated silicic acid exhibiting physical-chemical parameters such as relative width (gamma ) of the pore size distribution of 4-10 (g nm)/ml, Brunauer, Emmett and Teller (BET)-surface 90-320 m 2>/g, cetylammonium bromide (CTAB) surface area of 100-200 m 2>/g, sears number (V2) of 25-40 ml/(5 g) and sears number (V2/CTAB) ratio of 0.18-0.28 ml/(5 m 2>); (2) a precipitated silicic acid, obtained by the above process; (3) a vulcanizable rubber mixtures and vulcanizate comprising the precipitated silicic acid as filler material; and (4) a tire, comprising at least a precipitated silicic acid.

Stable aqueous suspension of precipitated silica

Abstract: The invention relates to a stable and pumpable aqueous suspension of silica. This suspension is characterised in that it comprises: - a precipitated silica, - a bioresin, - a cationic surfactant chosen from the group of quaternary ammonium compounds and of sulphonium or phosphonium compounds. This suspension may be employed more particularly in papermaking.