Silica precipitated silica

The thickening mechanism of precipitated silicas is similar to that of the fumed silicas. Precipitated silicas have more silanol groups than fumed silicas, but they have a lower concentration of silica (precipitated silicas generally contain some sodium sulphate). 

Filler Carbon black Natural amorphous silica, precipitated silica, nonblack nanofiller Solvent Organic solvent Aqua-based solvent... 

In contrast to the behaviour of pyrogenic silica precipitated silica can only be flocculated with PEG by lowering the pH value below pH = 3.5 or by addition of an electrolyte. 

The pH value and the electrolyte concentration show decisive influences on the flocculation and the sedimentation behaviour of precipitated silica. Precipitated silica could not be flocculated at high pH values without the addition of an electrolyte. At pH> 3.5 no change in the state of the suspension was observed, e.g. the sedimentogramms of the suspensions with polymer addition up to saturation (0 1) have the same shapes as that of the sedi-mentogram of the polymer free suspension. At pH 2.3 and even at a very low polymer concentration (c(40,000/PEG) > 3 10-5 mg/ml,... 

Amorphous Silica The term amorphous silica refers to aggregate of smaU particles with high specific surface area. They lack crystal structure and do not form a sharp x-ray diffraction pattern. They are known in several forms such as colloidal silica, precipitated silica, silica gels, and fumed sdica. The surface of such amorphous silica may contain silanol (SiOH) groups or can be anhydrous. 

The diversity of silica forms and their properties leads to a broad range of applications. Reviews on usage include those on crystalline and vitreous silicas (94), on silica sols (95), on silica gels and precipitated silicas (96), and on pyrogenic silicas, precipitated silicas, and silica gels (97). 

Precipitated Silicas. Figure 3 shows a typical manufacturing process for precipitated silicas. Precipitated silicas are formed by the acidification of sodium silicate solution under conditions that form primary particles that coagulate into clusters. In contrast to the conditions in a gel, the entire liquid phase is not enclosed by the solid silica phase. 

CAS 112926-00-8 EINECS/ELINCS 231-545-4 Synonyms Amorphous silica gel Polyethylenimine-silica Precipitated silica Silica, amorphous precipitated Silica, amorphous, precipitated and gel Silica gel dessiccant Classification Mineral... 

Property Diatomite, DE Fumed silica Precipitated silica... 

Colloidal silica Precipitated silica P5Togenic silica Silica gels... 

Synthetic silica types are used in coatings less as filler than as thixotropic, antisettling and matting additives. The different types include pyrogenic silica, precipitated silica and silica aerogels and hydrogels. They consist of coagulated amorphous spherical particles of very fine... 

The inorganic thickening agents are of two types [59]. The first t3rpe is produced from clay minerals such as hectorite, montmorillonite, saponite, attapulgjte, and sepiolite, and the second type includes the synthetic pyrogenic (fumed) silicas, precipitated silicas, synthetic clays (hectorite), and synthetic alumina. 

Name(s) silica gel, micronized amorphous silica, precipitated silica, hydrophilic fume silica... 

Fumed silica, precipitated silica, and silica gel are manufactured to contain amorphous silica, and because of this amorphous structure, they differ from natural silicas discussed in the previous sections. 

Low-valued silica sand and quartzite may be converted into specialty silica by various processes. The resulting specialty sihcas are generally classified based on their properties and methods of production and include fumed silica, precipitated silica, silica gels and sols and microsilica. The value of global industrial production of specialty silica is close to 2 billion per anmun, and the capacity of silica production is aroimd 1 million tons per annum, out of which the capacity of precipitated sihca (which is discussed here) is about 85%. These quantities clearly illustrate the importance of the industries and processes dealing with precipitated silica. 

Name(s) silica gel, micronized amorphous silica, precipitated silica, hydrophilic fimie silica CAS 63231-67-4 (silica gel) 112926-00-8 (gel precipitated) 112945-86-9 (fume silica)... 

Synthetic silicon dioxide (siUea) can be produced either by precipitation or by a pyrogenic (thermal) proeess. According to the method of production, synthetic silicon dioxide ean be classified into two groups precipitated and pyrogenic (fumed) silica. " Precipitated silicas have been used extensively in many mbber applications, much more than fumed silica. " In the mbber industry, the use of fumed silicas is limited due to expense, mainly being used as reinforcing fillers for silicon mbbers. Non-black fillers such as silica are chosen over CB for one or more of the following reasons ... 

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