Precipitated silica

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

Physicochemical properties, surface morphology and particle size distribution of precipitated silicas

Abstract: The results presented are from a study on the production of highly dispersed silicas by their precipitation from solutions of sodium metasilicate and ammonium salts. The applied ammonium salts were NH4HCO3 and (NH4)2CO3. The precipitation process was conducted in the absence or presence of 1 wt.% non-ionic surfactant (Rokanol K-7, Rokafenol N-6 or Rokafenol N-9). The highly dispersed silicas obtained were subjected to a physicochemical analysis typical for fillers. The analysis included estimation of the bulk density and the capacities to absorb water, dibutyl phthalate and paraffin oil. Particle size and morphology were evaluated using scanning electron microscopy. In addition, particle size distribution for the precipitated silicas was examined by dynamic light scattering. Silicas with the best physicochemical properties were obtained by precipitation using ammonium hydrogen carbonate. In particular, the silica precipitated in the presence of 1 wt.% Rokafenol N-9 demonstrated a magnificent capacity to absorb paraffin oil. Copyright © 2003 John Wiley & Sons, Ltd.

Method for the production of precipitated silicas

Abstract: Fallungskieselsauren, die je nach Art ihrer Vermahlung folgende physikalisch-chemischen Kenndaten aufweisen: Precipitated silicas which have the following physico-chemical characteristics, depending on the nature of their grinding: werden hergestellt, indem man eine gemas DE-AS 14 67 019 gewonnene Fallungskieselsaure-Originalsuspension verdunnt und unter Konstanthalten des pH-Wertes zwischen 7 und 9 gleichzeitig Alkalimetallsilikatlosung, Schwefelsaure und Wasser hinzugibt. be prepared by diluting an obtained according to DE-AS 14 67 019 precipitated silica original suspension and stirred at a constant pH 7-9 at the same time are added alkali metal silicate solution, sulfuric acid and water. Anschliesend werden die Fallungskieselsauren abfiltriert, gewaschen, getrocknet und mit einer Pendelmuhle oder einer Strahlmuhle vermahlen. Subsequently, the precipitated silicas are filtered, washed, dried and ground with a bowl mill or a jet mill. Aufgrund ihrer Abrasivitat konnen die Fallungskieselsauren als Polier- und Schleifmittel, im Fall der strahlvermahlenen Variante auch als Polier-, Schleif- und Verdickungsmittel in Zahnpasten eingesetzt werden. Due to their abrasiveness the precipitated silicas can be used as polishing and abrasive, in the case of variant strahlvermahlenen as polishing, grinding and thickener in toothpastes.

Bromide and Chloride Ionic Liquids Applied to Enhance the Vulcanization and Performance of Natural Rubber Biocomposites Filled with Nanosized Silica

Abstract: In this study, the possibility of using ionic liquids (ILs) as auxiliary substances improving the vulcanization and physicochemical properties of natural rubber (NR) biocomposites filled with nanosized silica was investigated. Hence, the influence of ILs with bromide and chloride anions and various cations, i.e., alkylimidazolium, alkylpyrrolidinium and alkylpiperidinium cation, on the curing characteristics and crosslink density of NR compounds was determined. Furthermore, the effect of nanosized silica and ILs on the functional properties of the obtained vulcanizates, including mechanical properties under static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging, were explored. Applying nanosized silica improved the processing safety of NR compounds but significantly increased the optimal vulcanization time compared to the unfilled rubber. ILs significantly improved the cure characteristics of NR compounds by increasing the rate of vulcanization and the crosslink density of NR biocomposites. Consequently, the tensile strength and hardness of the vulcanizates significantly increased compared to that without ILs. Moreover, the use of nanosized silica and ILs had a favorable impact on the thermal stability of the vulcanizates and their resistance to prolonged thermo-oxidation.

Adsorption of polymers at the solution–solid interface. XIII. Adsorption and steric stabilization with styrene–2‐vinylpyridine copolymers

Abstract: Random and block copolymers of styrene and 2-vinylpyridine, covering the full range of composition, have been synthesized. The adsorption of these polymers from trichloroethylene solution on to precipitated silica has been studied and their ability to impart colloidal stability to the silica dispersions also investigated. Estimates of the layer thickness of adsorbed copolymers have been made. Polystyrene is not adsorbed from trichloroethylene and does not stabilize dispersions of precipitated silica. A random copolymer having 1% 2-vinylpyridine units is adsorbed but shows very little steric stabilization. Random copolymers of 2-vinylpyridine content greater than 10% and AB block copolymers of more than 6% 2-vinylpyridine behave very similarly in respect both of the quantity adsorbed and in their ability to stabilize silica suspensions. Layer thickness does not seem to depend on copolymer composition. Random copolymers with low to intermediate 2-vinylpyridine contents are better steric stabilizers in trichloroethylene than are the corresponding copolymers of methyl methacrylate with styrene: this is attributed in part to the longer sequences of adsorbable units in the vinylpyridine copolymers.