Mica, as a wet ground pigment, is specified for use in protective coatings under its own ASTM standard. This page covers that specification and a documented finding on how mica loading level affects rigid PVC foam performance — improving some properties while working against others.
What is it?
Mica, in wet ground muscovite form, is specified under ASTM D607 in two types for use in protective coatings, with requirements covering density, moisture, grit, coarse particles, residue, ignition loss, and color.
Why should I use it?
- Its pigment-grade properties are defined by a dedicated specification — see “What is it?” above.
- Research has directly quantified its effect on PVC foam performance, including a real trade-off with loading level — see Limitations.
How it’s used
In Plastics & Polymers, Mica is used as a filler, most directly documented as a reinforcement in rigid PVC foam.
Limitations — when it isn’t the right choice
- Adding mica to PVC foam is a genuine trade-off, not a straightforward improvement — and it doesn’t help every property equally. A 2015 peer-reviewed study on rigid PVC foam filled with high-aspect-ratio phlogopite mica at loadings of 0%, 5%, 10%, 15%, and 20% by weight found that at 20% mica, dimensional stability improved by 44% (shrinkage at 82°C dropped from 3.4% to 1.9%), and storage modulus rose from 225 MPa to 480 MPa at a 15% loading. However, flexural strength did not improve at any loading level tested, and impact strength deteriorated by more than 25% at 20% loading, as particle agglomeration in the foam’s cell walls became a factor above 15%. This was documented for one specific PVC foam and mica grade; it should not be assumed that every commercial formulation responds identically at the same loading levels without its own test data.
