Application of Silicate Minerals in Coatings

The silicon-oxygen tetrahedron [SiO4]4- composed of Si and O in the basic structural unit of silicate can be surrounded by other cations in isolation, or can be connected with each other in a corner-sharing manner to form various forms of silicon-oxygen The backbone binds to other cations
.
The silicon-oxygen skeleton is mainly layered, frame-like and needle-like
.

Common Silicate Fillers in Coatings

In the layered silicon-oxygen framework, the silicon-oxygen tetrahedra are distributed in the same plane, and are connected with each other by three corners to form a two-dimensional extended planar layered coating online coatingol.
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Mica powder exists in nature in the form of multi-layer crystalline flakes.
The horizontal arrangement in the coating can prevent ultraviolet radiation and protect the coating film, and can also prevent moisture from penetrating
.
In architectural coatings, the introduction of mica powder can improve the crack resistance of the coating film and improve the scrub resistance
.
A small amount of mica is used as a special component of the steel structure primer, which can improve salt spray resistance and durability
.

The chemical composition of kaolin is hydrated aluminum silicate, also known as clay.
According to the production process, it can be divided into washed kaolin and calcined kaolin

In the frame-shaped silicon-oxygen skeleton, when the silicon-oxygen tetrahedra share four corner vertices with each other, a skeleton-like shape that develops into a three-dimensional space is formed
.
However, this framework structure is not completely composed of silicon-oxygen tetrahedron, but is partially replaced by aluminum-oxygen tetrahedron, so excess negative charges appear to form framework complex anions
.

Feldspar powder is a typical framework-like mineral filler
.

Nepheline feldspar is composed of albite, potassium feldspar, and nepheline
.
Nepheline is nominally sodium aluminum silicate, but potassium replaces part of the sodium
.
Nepheline feldspar is based on a six-membered ring composed of silicon-oxygen tetrahedral rings connected at the corners
.
Half of the Si4+ in the tetrahedron is replaced by Al3+, and the resulting charge imbalance is compensated by Na+ and K+
.
Unlike feldspar powder, Na+ can exchange with H+, which reduces the acid stability of nepheline
.

When the silicon-oxygen tetrahedra share two corner vertices with each other, a unidirectionally extending needle-like or fibrous silicon-oxygen skeleton, such as wollastonite, is formed, the morphology of which is shown in Figure 3
.