Gloss reduction

Fumed silicas (Si02). Fumed silicas are common fillers in polychloroprene [40], natural rubber and styrene-butadiene rubber base adhesives. Fumed silicas are widely used as filler in several polymeric systems to which it confers thixotropy, sag resistance, particle suspension, reinforcement, gloss reduction and flow enhancement. Fumed silica is obtained by gas reaction between metallic silicon and dry HCl to rend silica tetrachloride (SiCU). SiC is mixed with hydrogen and air in a burner (1800°C) where fumed silica is formed ... 

This is especially true in industrial and urban areas. Fig. 87 shows a paint containing Chrome Yellow, which was subjected to a test as described in Section 1.6.2.2 treatment with 1 N sulfuric acid for one hour at 70°C. The distinct color change on the circular test area is accompanied by a considerable gloss reduction. In the corresponding lead chromate-free system, it is only the binder that is affected, which reduces the gloss the color value on the other hand is retained. 

Good surface appearance No gloss reduction No silicones bleeding Chemical resistance Excellent weatherability Reduction of overspray... 

In industrial products, the use of fumed silica will confer thixotropy, sag resistance, particle suspension, emulsifiability, reinforcement, gloss reduction, flow enhancement of powders, anti-caking, anti-slip, anti-blocking, etc. Because of its effect on these important properties, fumed silica is widely used in many industries. 

If both E and are positive, the defoamer penetrates into the foam lamella and spreads across the surface. This creates interfacial tension differences that destabilize the lamellae and cause the foam to collapse. In simple terms it can be said that defoamers act because of their controlled incompatibility with the paint system. If a defoamer is too compatible its defoaming effect is not sufficient, if it is too incompatible film defects occur (e.g., gloss reduction, formation of craters). 

For waterborne paint systems (especially emulsions used for decorative purposes) defoamers based on mineral oils are often used. In addition to the mineral oil as carrier, these products contain finely dispersed hydrophobic particles (e.g., silica, metal stearates, polyureas) as defoaming components. A small amount of silicone is sometimes included to intensify the defoaming action. For high-quality waterborne coatings in industrial applications, defoamers are used that contain hydrophobic silicone oils as the principal defoaming component instead of mineral oils. They have a better defoaming effect, but are more expensive. In most cases silicone defoamers do not cause the gloss reduction that is often observed with mineral oil products. 

At the other end of the spectrum, pressure-sensitive adhesives, contact adhesives, aqueous varnishes, clear sealants and caulks, overprint varnishes for metal decorating and printing are essentially pigment free. Minor amounts of silica are used for gloss reduction in the case of varnishes. Carpet, construction and ceramic/brick adhesives may contain substantial amounts of filler, not only to reduce cost but also to provide shear strength. Gloss and semi-gloss latex enamels... 

Chem. Descrip. Unsubstituted hindered amine It. stabilizer (HALS) Uses Lt. stabilizer for two-coat metallic systems, industrial, architectural, roofing, marine, traffic, and automotive paints, overprint varnishes, plastics, UV-cured coatings, solv.-based inks stabilizes enamel against gloss reduction and cracking... 

EVA gloss reduction, impact, plasticization permanence more costly vs. liquid plasticizer... 

Rigid PVC blown film Improved printing gloss reduction Decorative sheet for paneling... 

Mineral oilbased defoamers are composed of 85 % carrier oil (aliphatic or aromatic mineral oil), 10 % hydrophobic particles, with the remainder an emulsifier and other ingredients such as metal stearate and fatty acid derivatives. They are used in flat and semigloss emulsion paints but are not suitable for higher quality aqueous industrial coatings due to possible surface defects and gloss reduction. 

If reductions in gloss are desired, crosslinked PVC resins can be blended with homopolymer resins. In order to maximize gloss reduction, the apparent viscosity of the crosslinked resin should be higher than that of the homopolymer resin it is being blended with. 

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