The basics of resins, pigments, additives and solvents

Many people think of paint as a liquid for adding color.

Paint does have a coloring role. In industrial coating, however, it is more than a colored liquid.

Paint is applied to a substrate surface, dries or cures, and becomes a coating film. That film creates the appearance, protects the substrate and provides the required functions.

When considering paint, therefore, it is important to look beyond the liquid in the can. We need to examine what kind of coating film it ultimately becomes.

To do so, first understand the components that make up paint.

Paint consists of several components

Paint generally consists of components such as the following.

• Resin
• Pigments
• Additives
• Solvent or water

Each component has a role.

Paint is more than a simple mixture of these components. The formulation is balanced to deliver the intended coating film performance.

Even paints that appear to have the same color can differ considerably in performance if their compositions differ.

Resin is the main component that forms the coating film

Resin is the central component responsible for forming a coating film.

After the paint dries or cures, the resin remains on the substrate surface and provides the film’s framework.

The resin type makes a major difference to coating film properties.

For example, film hardness, flexibility, adhesion, chemical resistance, water resistance, weather resistance and drying behavior are strongly affected by resin type and design.

Industrial coatings use many resin types, including acrylic, polyurethane, epoxy, alkyd, melamine and polyester resins.

However, we cannot simply conclude that a product is good because it is acrylic, or strong because it is epoxy.

Products can have different designs even under the same resin name. The appropriate paint varies with application, drying conditions, film thickness, workpiece and service environment.

Pigments affect function as well as color

Pigments give paint its color.

Their role, however, goes beyond color.

Pigments have roles such as the following.

• Providing color
• Hiding the underlying surface
• Affecting gloss and texture
• Contributing to rust protection
• Affecting weather resistance
• Affecting film strength and hardness

Even among black paints, for example, weather resistance and color stability may change with the pigment used. Rust-inhibiting pigments also play an important role in rust protection paints.

Pigments are therefore more than powders for adding color. They are important materials that determine coating film performance.

Additives can strongly affect paint performance even in small amounts

Additives are often present in paint only in small amounts.

That does not make them unimportant.

Additives have roles such as the following.

• Dispersing pigments uniformly
• Preventing settling in the paint
• Removing foam
• Improving the finish texture
• Preventing sagging
• Improving leveling
• Limiting deterioration caused by ultraviolet light
• Supporting preservation and resistance to mold
• Adjusting coating film surface properties

If additives do not function adequately, problems can appear during application or after drying even when the paint itself looks much the same.

Examples include dirt nibs, bubbles, sagging, unevenness, settling, poor dispersion and gloss defects.

Some appearance defects on the factory floor involve additive function or formulation balance, as well as application conditions.

Solvents and water make paint suitable for application

Solvents and water are used to put resins and pigments into a condition that is easy to apply.

Solvents do more than thin the paint. They affect flow, drying behavior, finish texture, leveling, adhesion and the development of film thickness.

Changing the thinner altered drying even though the paint was the same. The finish texture changed. Blushing appeared. Adhesion became worse.

These effects occur because solvents are involved in coating film formation.

Water-based paint is not necessarily simple just because it uses water. Water evaporation, co-solvents, drying conditions, temperature and humidity, and equipment conditions all affect coating film quality.

Although solvents and water are temporary components of paint, they therefore have an important role in determining coating film quality.

Distinguish components that form the film from components that evaporate

An important part of understanding paint is distinguishing the components that become the coating film from those that evaporate.

Some paint components remain as the coating film after drying. These include resin, pigments and some additives.

Most solvent or water, on the other hand, evaporates during drying and does not remain in the final coating film.

The amount of paint in the can is therefore different from the amount of coating film remaining after drying.

This principle directly relates to film thickness control.

Adding more thinner may make paint easier to apply. However, it reduces the proportion of film-forming components that remain after drying. The required film thickness may therefore not be achieved.

Even with the correct viscosity, an excessively high thinning ratio can result in insufficient dry film thickness.

Coating control therefore needs to consider solids content, thinning ratio, wet film thickness and dry film thickness together, as well as viscosity.

The same color does not necessarily mean the same performance

Color is often the first point considered when evaluating an alternative paint.

Does it match the current product’s color? Does the appearance look similar? Does the gloss match?

Color and appearance are, of course, important. However, the same apparent color does not necessarily mean the same performance.

For example, the following differences may occur.

• Different adhesion
• Different drying time
• Different film thickness development
• Different water resistance
• Different chemical resistance
• Different weather resistance
• Different hardness or flexibility
• Different suitable thinners
• Different baking conditions
• Different application workability

Even if the color matches, different resin, additive or solvent designs change ease of use on the factory floor and long-term performance.

When evaluating alternative paint, therefore, check the application, workpiece, application method, drying conditions, film thickness and required performance, as well as color.

Particular care is needed when selecting local alternatives in Vietnam

Factories in Vietnam sometimes consider switching from imported paint to local paint because of cost, lead time, inventory, customs clearance or exchange rates.

This is a very important initiative. Being able to use paint that can be sourced locally and reliably offers major cost and supply benefits.

However, local substitution requires care.

The color is close. The price is low. It is easy to obtain.

Judging on these points alone can lead to problems after mass production begins.

Checks should cover points such as the following.

• Adhesion to the workpiece
• Performance at the required film thickness
• Drying and curing conditions
• Thinner to be used
• Compatibility with the application method
• Consistency of appearance
• Water resistance
• Chemical resistance
• Weather resistance
• Customer specification requirements
• Application workability in mass production

Local substitution is more than searching for cheap paint. It is a technical activity that requires understanding the existing film performance and checking how far local materials can reproduce it.

Understanding paint is the first step in reducing problems

It is not easy to identify the cause immediately when a coating defect occurs.

Coating problems include many forms, such as poor adhesion, inadequate drying, dirt nibs, unevenness, sagging, color differences, cracking, blistering and blushing.

These defects involve the substrate, surface preparation, thinning ratio, film thickness, drying conditions, working environment and equipment condition, as well as paint.

However, causes cannot be isolated correctly without understanding the basic composition of paint.

What role does the resin play? What do pigments affect? Which defects involve additives? How do solvents and thinners contribute to film formation? How does a change in solids content affect film thickness?

Understanding these points enables a systematic view of coating problems, rather than relying on feel.

The approach CoatureVietnam values

CoatureVietnam considers paint a material for producing coating film quality, as well as a commercial product.

We look beyond paint names and colors and value perspectives such as the following.

• What substrate will be coated?
• What coating film performance is required?
• In which process will it be applied?
• What drying and curing conditions are required?
• At what film thickness must performance be achieved?
• What service environment will it face?
• Can it be used consistently in mass production?

Paint is more than a colored liquid. It is a functional material that supports coating quality.

Paint selection therefore requires checking film performance and consistency in the workplace, as well as color, price and lead time.

Coating the Future with Science and Care. The first step is to understand paint correctly.

Points to check on the factory floor

When selecting, changing or evaluating alternatives to paint, it is important to check the following points.

• What is the resin system of the current paint?
• Is coating intended for appearance, protection or adding a function?
• What is the workpiece substrate?
• What dry film thickness is required, in μm?
• Which thinner is being used?
• Has a standard thinning ratio been defined?
• Are drying and curing conditions clear?
• Has adhesion been checked?
• Are there requirements for water resistance, chemical resistance or weather resistance?
• Are there customer specifications or approval conditions?
• Is the paint easy to apply in mass production?
• Are alternatives compared and evaluated under the same conditions?

Related CoatureVietnam services

This topic relates to the following services.

Paint Voyager We support paint selection suited to the application and required performance.

Local Optimer We evaluate the potential to replace imported paint with local paint, checking coating film performance and suitability for mass production, as well as color.

Thinner Streamer We regard thinner as an important material supporting film formation, as well as a diluent, and support selection suited to application conditions.

Paint Optimizer We review how existing paint is used, thinning ratios, film thickness and drying conditions to help stabilize coating quality.