
Nepheline syenite’s photochemical stability has been known to the paint and coatings industries for decades. Now the same performance is now being demonstrated through testing in filled plastics applications and products. HIFILL®-N additives from Covia are unique all-natural sodium-potassium silicate minerals that are suitable for replacement of calcium carbonate (CaCO3) in polymers. HIFILL N behaves basically the same as CaCO3 in performance properties such as mold shrinkage, melt index, tensile, impact HDT, flexural modulus, etc. allowing for formulation and processing cost reduction.
HIFILL N Case Study
This study looked at the photochemical stability of Nepheline syenite and Calcium carbonate in a PP resin, without and with a HALS type UV stabilizer. Test samples were made with a 5% loading of each mineral. The samples were exposed to UV radiation (ASTM D4329 – Method A) and the DE color change we measured in 500 hour intervals.
The extended durability of colored plastic products translates into higher value products and enables formulation cost savings through the optimization of light stabilizer usage levels, Nepheline syenite can potentially allow lower additives dosages given its low oil absorption.

Test results
- Nepheline syenite showed superior weatherability relative to Calcium carbonate in both stabilized and non-stabilized systems
- After 7000 hours in the QUV, Nepheline Syenite, with a UV stabilizer, had a delta E color change of only 1.69. Compared to a delta E color change of 4.6 for Calcium Carbonate, with the same UV stabilizer loading
- The data shows using Nepheline Syenite allows the user to lower the UV stabilizer package without sacrificing the UV resistance
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