Nepheline syenite is a silica-deficient functional filler and additive used globally in a variety of coating, adhesive and ink applications. It is composed of three minerals: soda and potash feldspar, and the mineral nepheline. Although it is deficient in crystalline silica, nepheline syenite otherwise provides physical performance properties that duplicate ground silica fillers. Also known in the coatings industry as MINEX® functional fillers and extenders, micronized nepheline syenite is valued for its color purity, ability to control gloss, ease of dispersion and durability. Since nepheline syenite functional fillers are naturally derived, and deficient in free-silica and heavy or transition metals, they are typically less burdened by regulatory requirements such as REACH, RoHS and TSCA.
Figure 1 shows the typical particle shapes, while Table 1 lists the typical properties of nepheline syenite. Nepheline syenite is considered a moderate gloss reducer based on its low oil absorption and combination of angular, rectangular and nodular shapes. Mohs hardness on the 1 to 10 scale is about 6. The particles themselves are moderately hard or rigid and possess high compressive strength, providing scratch and abrasion resistance in the polymer matrix. The low oil absorption contributes to the ease of dispersion and low viscosity build.