Precipitated silica

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

Methods for synthesizing precipitated silica and use thereof

Abstract: The synthesis of precipitated silica having improved chemical and physical properties of use as a reinforcing filler in polymeric matrices is described. Improvements in the properties result from the synthesis of the silica al a reduced ionic strength. In particular, the use of silicia acid during synthesis, provides a solution of reduced ionic strength, which favors the formation of improved colloidal structure via increased aggregation and reduced agglomeration. In addition, the surface of the silica precipitate formed may be modified by the addition of surface modifying agents, during synthesis to further enhance the desired reinforcing properties of the precipitated silica. The invention also embodies polymeric compositions of improved tensile and elongation strengths, with the compositions including precipitated silica, synthesized at reduced ionic strengths and having modified surfaces, in combination with a polymeric compound.

Precipitated silicic acid, its preparation and vulcanizable elastic rubber mixture containing this and vulcanized rubber

Abstract: A precipitate of silica having the following physicochemical parameters: BET surface area: from 35 to 350 m /g Ratio of BET/CTAB surface area: from 0.8 to 1.1 Pore volume PV: from 1.6 to 3.4 ml/g Silanol group density (V2 = consumption of NaOH): from 6 to 20 ml Mean aggregate size: from 250 to 1500 nm CTAB surface area: from 30 to 350 m /g DBP number: from 150 to 300 ml/100 g V2/V1 according to Hg porosimetry: from 0.19 to 0.46 DBP/CTAB: from 1.2 to 2.4 is prepared by reacting alkali metal silicate with mineral acids at temperatures of from 60 to 95 DEG C while maintaining a pH of from 7.5 to 10.5 with continuous stirring, continuing the reaction to a solids concentration in the precipitate suspension of from 80 to 120 g/l, adjusting the pH to a value equal to or less than 5, filtering off, washing, drying and, if desired, milling or granulating the precipitated silica. The precipitated silica is used as filler in vulcanisable rubber mixtures and vulcanisates.

The role of phosphopeptides in the mineralisation of silica

Abstract: We investigated the silicification activity of hyperphosphorylated peptides in combination with long-chain polyamines (LCPA). The bioinspired in vitro silicification experiments with peptides containing different amounts of phosphorylated serines showed structure–activity dependence by altering the amount and morphology of the silica precipitate. Our study provides an explanation for the considerable metabolic role of diatoms in the synthesis of hyperphosphorylated poly-cationic peptides such as natSil-1A1. The efficient late-stage phosphorylation of peptides yielded a synthetic heptaphosphopeptide whose silicification properties resemble those of natSil-1A1. As opposed to this, unphosphorylated poly-cationic peptides or LCPA require concentrations above 1 mM for silicification. Hyperphosphorylated peptides showed a linear dependence between the amount of dissolved peptides and the amount of precipitated silica in the concentration range below 1 mM. Under mildly acidic conditions and short precipitation times, the concentration of the added LCPA determined the size of the silica spheres.

Measurement of attractive forces between single aerogel powder particles and the correlation with powder flow

Abstract: An atomic force microscope (AFM), which allows the measurement of forces as low as one tenth of a nano-Newton, was used to determine the attractive forces between single silica aerogel powder particles ( 100 μ m diameter) under two different atmospheric conditions. Forces on the order of 10 nN were found to depend mainly on the contact geometry and thus on the surface structure of the powder particles. In a second series of experiments, the surface structure of the silica aerogel powder particles was characterized using the AFM. Smooth surface areas, several micrometers in size, are separated by cliffs and cracks. For comparison, the same measurements were made with precipitated silica powder. Here larger forces and a different surface structure were found. The structure of precipitated silica particles is spheroidal with bumps on it, which are some hundred nanometers in size. In addition to the AFM measurements, powder flow rate from a hopper was measured. The flow of powders depends on the surface structure but also on the atmospheric conditions (e.g. moist atmosphere or vacuum). In contrast to precipitated silica powder, silica aerogel powder showed a significantly higher flow rate under vacuum than in moist air.