Pultrusion Resins and Their Importance in the Manufacturing Industry

The resins used in the pultrusion process primarily include unsaturated polyester resins, epoxy resins, vinyl ester resins, and phenolic resins. Unsaturated polyester resins are the most widely used and technically mature, accounting for approximately 90% of total usage. Generally speaking, unsaturated polyester resins used in BMC and SMC can be used in pultruded products. In practice, the resin formulation should be designed based on the characteristics of the pultrusion process and the intended use of the final product. Currently, both domestic and international resin manufacturers have developed unsaturated polyester resins specifically for pultrusion products. Epoxy and phenolic resins specifically for pultrusion have also become available. In addition to thermosetting resins, thermoplastic resins are also used in pultrusion. Thermoplastics such as polypropylene (ABS), nylon, polycarbonate, polysulfone, and polyphenylene ether are used as binders in pultruded fiberglass products, improving their heat resistance and toughness while reducing costs. Thermoplastic resin pultrusion represents a new development direction.

Thermoplastic resin pultrusion represents a new development direction, aiming to improve the heat resistance and toughness of products while reducing costs.

1.The role, components and selection principles of the substrate

1.1 The role of the substrate

1.1.1 Binder The substrate binds the reinforcement into a whole and plays the role of transferring and balancing the load.

1.1.2 Gives basic properties to the composite material The mechanical properties of FRP mainly depend on the reinforcement, but the mechanical properties of FRP such as bending and compression mainly depend on the substrate. The resin substrate plays a decisive role in the heat resistance, chemical corrosion resistance, flame retardancy, weather resistance, electrical insulation, biocompatibility and light transmittance of FRP.

1.2. Components of the substrate

1.2.1 Synthetic resin Synthetic resin refers to pure resin liquids such as polyester resin, epoxy resin, phenolic resin, etc., which are the main components of the polymer substrate.

1.2.2 Auxiliary agents are mixed with pure resin and are generally used in small amounts. They play a key role in controlling the reaction and giving the product special properties. Commonly used auxiliary agents include curing agents, accelerators, aging agents, flame retardants, diluents, toughening agents, fillers, pigments, etc.

1.3. Selection principles of the substrate

1.3.1 Design requirements Each product has design performance indicators to ensure the safety of product use. Therefore, when selecting a base material, the technical requirements of the product must be considered first, such as whether the product is a structural component, whether it requires corrosion resistance, whether there are special requirements for electrical and optical properties, whether there are hygiene standards, etc. The resin to be selected must be determined based on the specific technical requirements of the product.

1.3.2 Process requirements Based on the pultrusion process requirements, the formula design must not only meet the design and use requirements of the product, but also have a long gel time (i.e., the service life is generally required to be more than 8 hours) and a fast curing speed to achieve the requirements of continuous pultrusion and rapid curing. Therefore, the resin is required to have the following characteristics:

① Low viscosity (preferably below 2000 Pa·s), the resin has good fluidity and wettability, which is convenient for impregnation of reinforcement materials;

② Low curing shrinkage, fillers can be introduced into the resin formula, which can not only reduce the curing shrinkage of the product, improve the performance of the product, but also reduce costs;

③ Long gel time and short assimilation time;

④ Good adhesion;

⑤ With a certain degree of flexibility, the product is not easy to crack during molding.

1.3.3 Economic analysis When selecting resin, in addition to considering the technical requirements and process requirements of the product, the economic efficiency should also be considered. Among several suitable resins, the one with the lowest cost should be selected to improve the market competitiveness of the product.

2.The importance of pultruded resin in the manufacturing industry

2.1 High performance:

Pultruded resin composite materials have excellent performance, combining high strength, high corrosion resistance and lightweight characteristics. The aerospace field has strict requirements on materials. Its lightweight advantage can reduce the weight of the aircraft and improve fuel efficiency. High strength can ensure structural stability and meet complex design requirements. In the construction industry, it is used to manufacture bridges and structural components, capable of withstanding long-term loads and environmental corrosion, extending the lifespan of buildings. In the transportation sector, it is used in the manufacture of automotive and train parts, reducing weight, enhancing corrosion resistance, and reducing maintenance costs.

2.2 Manufacturing Efficiency:

Pultrusion is a continuous production process with significant advantages over traditional methods. It allows uninterrupted production, increasing output and reducing downtime due to mold changes and equipment adjustments. Cost-effectively, continuous production improves raw material utilization and reduces waste, while automated equipment also reduces labor costs. Furthermore, it enables faster delivery, meeting rapid market demand, and strengthening a company's competitive advantage.

2.3 Custom Design:

The pultrusion process offers flexible design options. By adjusting molds and parameters, it can produce products of various shapes and sizes. It can produce not only simple shapes such as rods, tubes, and beams, but also complex profiles. In electronic equipment manufacturing, it can precisely create custom-shaped brackets and housings that conform to internal layouts. In the sporting goods industry, it can create unique shapes and performance for golf clubs and skis, meeting the individual needs of athletes.

2.4 Corrosion Resistance:

Pultruded resin-based FRP composites are extremely corrosion-resistant. In the chemical processing industry, they resist corrosion from strong acids and alkalis, ensuring the long-term safe operation of equipment. In the marine industry, where seawater is highly corrosive, parts manufactured with pultruded resins can reduce maintenance and replacement frequency, lowering operating costs. In the oil and gas industry, where equipment and pipelines operate in harsh corrosive environments, FRP composites ensure safe and efficient extraction and transportation.

These advantages of pultruded resins make them an indispensable material in modern manufacturing, especially in applications requiring high performance and corrosion resistance.