Polyester Resin is the primary film-forming material used in most modern powder coatings. It is a synthetic polymer created through the reaction of polyols and dicarboxylic acids, forming long molecular chains capable of melting, flowing, and later crosslinking with Curing Agents. Because of its strong outdoor durability, mechanical strength, and wide formulation flexibility, polyester resin has become the dominant resin system for architectural, industrial, automotive, and general-purpose powder coatings.

Polyester resins are designed with specific functional groups—most commonly carboxyl groups—that determine how the resin reacts with curing agents such as TGIC or HAA. The balance of molecular weight, acid value, and glass transition temperature (Tg) strongly influences gloss, flow, leveling, resistance properties, and storage stability. At PCOTEC, polyester resin is a key product category, engineered for stable curing behavior and high-performance outdoor durability.

What Polyester Resin Is Made Of

Polyester resin is synthesized through controlled polycondensation, combining several raw material components to create a tailored polymer structure.

Key building blocks include:

• Dicarboxylic acids such as terephthalic acid or isophthalic acid

• Polyols (diols) such as neopentyl glycol

• Modifiers to adjust melt flow, hardness, or flexibility

• Functional end groups (typically –COOH) enabling crosslinking

• Stabilizers to improve heat and storage stability

These components form the polyester backbone that determines curing speed, mechanical performance, and outdoor resistance.

Why Polyester Resin Is Important in Powder Coatings

Polyester resin contributes most of the mechanical and weathering performance to a coating. It defines how the powder melts, flows, and ultimately crosslinks.

Roles of polyester resin:

• Provides core film-forming ability

• Determines gloss level and surface smoothness

• Controls flexibility and impact resistance

• Defines outdoor weathering performance

• Supports chemical and moisture resistance

• Enables formulation for both low and high curing temperatures

• Influences storage stability and anti-caking properties

Because it balances durability, appearance, and processability, polyester resin is the most widely used resin system in powder coatings.

Types of Polyester Resin Used in Powder Coatings

There are two major categories of polyester resins for powder applications, both supported by PCOTEC through our resin and curing agent portfolio.

1. TGIC-Cured Polyester Resin

TGIC polyester systems are the standard choice for demanding outdoor applications due to their strong UV durability and mechanical strength.

Characteristics:

• Excellent outdoor weathering resistance

• High gloss stability

• Strong chemical resistance

• Good mechanical strength

• Ideal for building materials and outdoor machinery

Common curing temperature: 180–200°C

2. HAA-Cured Polyester Resin

HAA-cured systems are formaldehyde-free and environmentally friendly. They are typically used in indoor and light outdoor applications.

Characteristics:

• Eco-friendly and non-toxic

• Smooth, uniform appearance

• Good flow and leveling behavior

• Suitable for indoor and semi-outdoor use

• Performs well in low-temperature curing systems

Common curing temperature: 160–190°C

Key Performance Properties of Polyester Resin

Below is a summary of the most important properties controlled by polyester resin:

These parameters determine the final coating appearance and long-term stability.

How Polyester Resin Behaves During the Powder Coating Process

During manufacturing and curing, polyester resin undergoes several transitions:

1. Extrusion

Resin melts and disperses pigments, Fillers, and Additives evenly.

2. Cooling & Grinding

The solidified mass is ground into powder with controlled particle size.

3. Application

Electrostatic charge holds the powder on the substrate.

4. Curing Reaction

The resin reacts with curing agents to form a crosslinked polymer network.

5. Final Film Formation

A durable, smooth, protective film is formed on the surface.

Polyester resin must melt smoothly, disperse additives evenly, and crosslink fully for a high-quality finish.

Application Areas of Polyester Resin Powder Coatings

Polyester resin is used across nearly all major powder coating segments.

Primary application fields:

• Architectural aluminum profiles

• Outdoor furniture and equipment

• Automotive parts and accessories

• Agricultural and construction machinery

• Home appliances

• General industrial coatings

• Fencing, railings, guardrails

• Metal furniture and fixtures

These industries rely on polyester resin’s stable outdoor durability and long-lasting appearance.

Advantages of Polyester Resin

Polyester resin is preferred because it provides an ideal balance of performance, cost efficiency, and formulation flexibility.

Key advantages:

• Excellent UV and outdoor durability

• Wide curing window for different production conditions

• Strong mechanical performance

• Good flow and leveling for smooth film appearance

• High color stability during curing

• Compatible with various additives and pigments

• Suitable for numerous application systems

• Low VOC and environmentally friendly

These strengths make polyester resin the most widely adopted resin for high-performance powder coatings.

Limitations of Polyester Resin

While highly versatile, polyester resin has its limitations:

Limitations:

• Requires curing agents (TGIC or HAA) for full crosslinking

• Not as chemically resistant as epoxy resin for harsh indoor chemicals

• Performance varies depending on resin quality and formulation design

Even so, polyester is the best-balanced resin for most exterior and general-purpose applications.

PCOTEC Polyester Resin Advantages

PCOTEC provides a full range of polyester resin products, designed and manufactured with strict process control to ensure consistent industrial performance.

PCOTEC advantages:

• Stable acid value and molecular weight for predictable curing

• Controlled Tg for better storage and anti-caking

• Strong compatibility with PCOTEC TGIC and HAA curing agents

• Reliable melt viscosity for smooth leveling

• Strong UV durability for outdoor use

• MES and DCS-controlled production for batch consistency

• Technical support for formulation optimization and application design

Our polyester resins support architectural, automotive, industrial, and consumer-grade powder coatings with high reliability.

Conclusion

Polyester resin is a synthetic polymer used as the main film-forming material in most powder coatings. Made from polyols and dicarboxylic acids, it provides the perfect blend of weathering resistance, mechanical strength, and formulation flexibility. Whether paired with TGIC for outdoor durability or HAA for eco-friendly indoor systems, polyester resin remains the backbone of high-performance powder coatings.

PCOTEC offers high-quality polyester resins tailored for different curing systems, ensuring consistent curing behavior, stable appearance, and long-term field performance. For architects, manufacturers, and industrial users, polyester resin continues to be the most reliable and versatile resin system available in the powder coating market.