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How silica works in matting agent?
Sep 13, 2018

                

                                                             How silica works in matting agent?

                            

Mechanism of Matting

As a paint film dries, the evenly dispersed silica matting agent particles within the applied film create a micro-roughening of the surface.

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The incident light is diffusely reflected from this micro-rough surface conveying the impression of a low gloss or matt appearance (Fig. 2).

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Factors Influencing the Matting Efficiency


Three important silica features determine the matting efficiency of the various silica products:

.pore volume (porosity)

.particle size

.surface treatment

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Pore Volume

Our silica particles can be visualized as tiny sponges.The porosity of this highly porous material is expressed by the pore volume, which indicates the amount of internal voids in the silica particle.The higher the pore volume of the silica, the more efficient is our silica grade (see Fig. 5).This is due to the particles of high porosity being lighter,thus providing a higher number of particles per unit weight.

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Particle Size

The matting agents are available in a wide range ofprecisely defined average particle sizes, with a very accurately controlled particle size distribution.The larger the average particle size, the higher the matting efficiency (see Fig. 6). This is due to the larger particles creating the highest degree of surface micro-roughening.However, a particle may result in unacceptable surface

appearance or feel, if it is too coarse.Optimum matting efficiency with acceptable paint film

properties can only be achieved by selecting the SYLOID ®matting agent with an appropriate particle size in relation to the dry thickness of the coatings film.

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Surface Treatment (Fig. 7)

Some our silica products are surface treated with carefully selected organic compounds (e.g. waxes). The wax treatment prevents settling, in particular the formation of hard sediments, especially in low viscous, clear lacquers.Wax treated  products can also contribute positively to

improving other surface properties, such as mar and scratch resistance. Wax treated  products can exhibit a lower matting efficiency than untreated  products with similar particle size.Besides the silica matting agent, other formulation and application properties influence the final gloss.

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Dry Film Thickness (Fig. 8)

The higher the film weight at a given addition level of a selected matting agent product, the lower the matting effect. To matt thick films effectively, the selection of the largest acceptable particle size product is recommended.

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Other Factors (Fig. 9)

As the required addition level of matting agents to achieve a defined gloss depends on the amount and the dynamics of film shrinkage that occurs during drying, the matting efficiency of matting agents can also be influenced by:

.the resin system (different curing mechanisms)

. the solids content (or the amount of volatile compounds such as solvents)

.the type of solvent (differing vapour pressure)

.the drying method (fast or slow drying)

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