Acidic fillers

Formulation. Polysulftde-based sealants are formulated with appropriate ingredients to obtain the desired properties for a particular appHcation. A typical formulation contains Hquid polysulftde polymer, curing agent, cure accelerators (bases) or retarders (acids), fillers, plasticizers, thixotropes, and adhesion promoters. 

The acid-base properties of polymers, fillers and silane additives, as described by Fowkes [14] can be used to predict the effect of silanes on the dispersion of fillers in polymer, and viscosity of the mix. In general, opposites attract (give good dispersion) while like materials repel (poor dispersion) [15]. The effect of cationic silane (Z-6032) on the dispersion of silica (acidic filler) in this particular unsaturated polyester resin (acidic polymer) is shown in Table 6. Addition of Z-6032 in increments to a silica-filled polyester resin lowered the viscosity of the mixture to a minimum at about 0.4% silane based on the filler. 

Fillers. The buffering action of an alkaline filler is necessary to ensure permanence in filled paper. Retained alkalinity in the paper as it ages would resist any drop in pH that might result from absorption of either carbon dioxide or sulfur dioxide from the air. Acidic fillers, such as certain types of clay, accelerate the aging process. Calcium carbonate is an ideal filling material for permanent paper as well as for some grades not requiring permanency. In fact, the work of Barrow made the use of calcium carbonate a requirement in the manufacture of permanent book papers (1). 

Special considerations titanium dioxide accelerates UV degradation copper compounds catalyze thermal and UV degradation neutral and basic fillers are recommended because acidic fillers and pigments retard cure... 

Fillers are used in these products to improve mechanical properties or impart flammability resistance. Fillers are frequently silane-treated to further improve mechanical properties. Fillers must have a low moisture (below 0.1%), a low absorption of resin, and are expected to impart thixotropic properties. There are special cases. For example, if peroxyketals are used as initiators, basic fillers have to be used because acidic fillers interfere with cure times and the shelf-life of the composition. Shape and particle size distribution must be considered in filler selection to impart the desired rheological properties. Calcium carbonate is the most popular filler but aluminum trihydrate, anhydrous calcium sulfate, and silica are also frequently used. Barite is well suited to this application, especially if acid... 

Monheit GD, Coleman KM. Hyaluronic acid fillers. Dermatol Ther 2006 19 141-150. 

Monheit GD. Hyaluronic acid fillers hylaform and captique. Facial Blast Surg Clin North Am 2007 15 77-84. 

Skin In 22 women and 8 men (age range 45-55 years) in whom nasolabial creases were corrected by injecting the non-animal stabilized hyaluronic acid fillers Restylane and Perlane, minor adverse reactions after injection included erythema at the puncture site, needle marks, and bruising [12. ... 

Arsiwala SZ. Safety and persistence of nonanimal stabilized hyaluronic acid fillers for nasolabial folds correction in 30 Indian patients. J Cutan Aesthet Surg 2010 3(3) 156-61. 

Acidic fillers (talcum, silicates) have a negative influence on the crosslinking with peroxides of TPO due to the catalytic effect of the materials on the ionic decomposition of peroxides, and also due to the absorbtion of the crosslinking agents on their surface. These facts can be remedied by increasing the peroxide quantity and/or by the addition of coagents. 

It has been said that fillers are either basic or acidic and furthermore that acidic dispersants should be used on basic fillers and that conversely, basic dispersants should be used on acidic fillers. However, this simplistic approach is fallacious. Firstly, a large study showed that all mineral fillers are in fact amphoteric (Table 22.1). That is, they possess surfaces that are both acidic and basic. Furthermore, even a cursory glance at known dispersant— filler pairs will refute the earlier simplification. As one example, trialkoxy... 

Most of the commercially known grades of talc are processed to have average particle diameters of l-15 xm. Specific gravity ranges from 2.7 to 2.8 and the pH is alkaline (about 9). The latter suggests use in crosslinked PVC since free radical cure systems are sensitive to acid fillers. In general, the use of an alkaline filler tends to add to PVC heat stability. Talc fillers are supplied by Luzenac, Zemex, Specialty Minerals, and R.T. Vanderbilt. 

Alumina with neutral, basic and acidic (both Lewis type) surfaces was introduced into PE0ME-LiC104 electrolytes of various concentrations and examined with a variety of techniques. At higher salt concentrations when aggregation of ions occurs, fillers led not only to a decrease of the viscosity, but also to an increase in the fraction of free ions. The best results were obtained in the case of acidic fillers (Fig. 2.7). This results from interaction of acidic surface states with anions (Lewis bases) present in electrolyte as free ions, ion pairs, triplets, etc. The latter especially affect the viscosity and cation transference number. With the use of acidic filler, the fraction of free ions was increased as confirmed by Fuoss-Kraus calculations, as well as by Fourier transform infrared (FT-IR) investigations (Marcinek et al. 2005). The increase in the fraction of free ions means an increase of the number... 

Other studies showed that by adjusting the surface groups the efficiency and kinetics of lithium metal plating/stripping can be enhanced. Acidic fillers were observed to be the best choice (Egashira et al 2006). 

Whatever the model we assume, the experimental fact is that highly acidic fillers enhance stability and transport properties of the interfaces with low potential electrodes as presented in Fig. 2.8. 

Some extended works have been devoted to studies on the influence of highly acidic fillers (both soluble such as AlBrs or AlCh and ceramic ones) on the properties of gel polymer electrolytes based on PVdF. It was found that the conductivity and cation transference numbers increase on the addition of these strong Lewis acids. Also the stability of the interface with lithium metal is enhanced however, in the case of aluminium halides the reactions with organic carbonates can take place and affect the properties of such systems on prolonged storage (Stolarska et al. 2007 Walkowiak et al. 2006,2007). 

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