Lesson 9. Synthetic (Polymer) Binders

We have completed the analysis of the first, fundamental group — mineral binders. We studied in detail how lime, gypsum, cement, and silicates use their stone‑like nature to achieve strength, durability, and vapor permeability. At the same time, we identified their common and main limitation: low elasticity.

In this lesson, we move on to the second, vast and dominant group of binders — synthetic binders. These are materials created by the chemical industry to eliminate the shortcomings of natural components. You will learn what they are and how they differ fundamentally.

For a decorator, it is important to understand the differences between synthetic binders, because the market offers a huge variety of products based on them. This allows you to choose materials consciously, relying on their behavior and capabilities, rather than price or marketing promises.

For convenience, we divide synthetic binders into two main functional groups, which determine their behavior and application: film‑forming aqueous dispersions and reaction‑curing systems.

Group 1: Film‑Forming Aqueous Dispersions (Acrylic Base and Variations)

This is the most important and widespread group of binders, forming the basis of about 95% of all modern paints and decorative plasters.

The principle is simple: microscopic polymer particles (in other words, plastic) are evenly distributed in water and do not stick together. When the material is applied to a surface, the water gradually evaporates, and the plastic particles bond with each other, forming a strong film. This film becomes the coating we see in the end. Its strength, elasticity, water resistance, and durability depend directly on the type of plastic used for the particles.
If the polymer material contains filler (such as sand or marble chips), one of the film’s tasks is to glue these particles together and hold them firmly on the surface. If there is little or no filler, the material is a varnish: it creates a transparent protective film.

The aqueous dispersion itself is the liquid base in which the plastic particles “float.”

Regardless of the type of plastic, the material is called water‑dispersion, with specification of its type. For example: water‑dispersion acrylic paint, water‑dispersion styrene‑acrylic plaster, water‑dispersion copolymer varnish, and so on.

Group 2: Reaction‑Curing Systems (“Liquid Armor”)

These binders harden not through simple evaporation of water or solvent, but through an irreversible chemical reaction. Typically, they are two‑component (2K) systems consisting of a resin base and a hardener. After mixing, a process begins that transforms the liquid components into an extremely strong polymer network. They are used where maximum strength and resistance are required.

Two key representatives belong to this group:

• Polyurethane resins — leaders in combining wear resistance and elasticity.
• Epoxy resins — champions in hardness, chemical resistance, and adhesion.

Conclusion

You have now been introduced to the two main groups of synthetic binders:

• Film‑forming aqueous dispersions, which harden through water evaporation and are ideal for mass use.
• Reaction‑curing systems, which harden through chemical reaction, providing maximum strength.

Understanding the differences between these systems and their forms is critical for decorators: it allows you to choose the right material for a specific task, predict coating behavior, and avoid mistakes in practice.

Now we can move from general theory to studying specific types within each group. In the next lesson, we will begin with the representative of the first and most widespread group — acrylic binder.