Polyester resin is a material that consists of organic compounds that are typically viscous or solid and have a synthetic origin. It is a low-viscosity resin that is made from a chemical reaction of a diacid and an alcohol. Polyester resin is a thermoset resin that begins curing as soon as the catalyst is added and turns from a viscous liquid to a solid under the correct conditions.

Thermoset polyester resins, used as the matrix in the manufacturing of the GRP Pipes and other composite materials, are classified as:

• Terephthalic resins, a resin containing primarily terephthalic acid are known as a Terephthalic resin which is commonly used in GRP Pipe manufacturing. It is often prepared for buried pipeline applications where weathering effects are kept away. Terephthalic resins are used when high modulus and strength are desired, but the low colour properties of an Iso resin are not necessary. Terephthalic acid is generally lower cost than isophthalic acid, but both give similar strength characteristics to a GRP product.

• Orthophthalic resins, which are the general-purpose resins used in water conveying and sewerage applications. They are used for manufacturing laminates, which are not supposed to undergo strong chemical attacks or weathering. From the thermal point of view, orthophthalic resins are employed at ambient or medium-low temperatures. They should not be used for the making of the internal liner of a fiberglass pipe.

• Isophthalic resins, the most suitable end-use are in the manufacturing of pipes conveying waste liquids, drinking water and seawater above or below ground. They are more resistant to corroding substances present in the ground, to most salts, and medium concentrations of oxidizing acids.

• Vinylester resins, combine a greater resistance to chemicals with a high mechanical strength, which is also true at high temperatures. Isophthalic and Vinylester resins are mostly used for the internal liner of the pipe. They are also used for the transportation of hot water up to 80°C (for example in the heating systems), as well as for the transportation of water in the cooling systems, sea water outfalls from power plants, desalination plants, etc.

• Bisphenolic resins, have lower mechanical properties compared to vinylester resins, but they are characterized by high resistance to the chemicals.

For each of the resin types given above, there are a wide variety of subtypes. The resin manufacturers usually supply the Chemical Resistance Tables and suggestions for the use and curing of each resin.

The below graph shows a general-purpose comparison of different kinds of resins, based on their several characteristic properties. The behaviour will vary as per the specific resin product.

Resin systems offer several advantages in various applications and provide unique characteristic parameters to the composite materials as they are the matrix. Below are some of the advantages of resin.

1. Versatility

There are many different kinds of resin types formulated to meet specific requirements, making it suitable for a wide range of applications.

2. Lightweight

Resin is lightweight compared to many traditional materials such as metal or concrete. This characteristic is beneficial for GRP pipes since it increases the strength-to-weight ratio.

3. Corrosion Resistance

Resin exhibits excellent corrosion resistance, making it an ideal choice for applications where exposure to harsh chemicals, moisture, or corrosive environments is expected.

4. Design Flexibility

Resin can be applied to complex shapes and sizes, allowing for intricate designs and customization.

5. Good Insulating Properties

Resin exhibits excellent electrical insulation properties, making it suitable for applications in electrical and electronic components, such as insulators, circuit boards, and encapsulation of electronic devices.

6. Chemical Resistance

Resin offers resistance to many chemicals, including acids, alkalis, solvents, and oils. This property is beneficial in applications where exposure to various chemicals is expected, such as sewage pipelines, chemical processing spools and storage tanks.

7. Low Cost

Resin materials can often be produced at a lower cost compared to other materials, making them a cost-effective choice for a wide range of applications.

8. Durable and Long-lasting

Resin materials can exhibit good durability and long-term performance, with resistance to wear, impact, and fatigue, depending on the specific formulation and reinforcement. GRP pipes offer min. 50 years of lifetime.

As TOPFIBRA, we provide specific requirements for different kinds of resin systems that are going to be used in E-CFW and E-CWS technologies for GRP Pipe and Coupling manufacturing purposes.