Glass fiber tubes are manufactured by impregnating glass fiber filaments with resin and then curing them in a high-speed polymerization device that utilizes light, electricity, and heat. The process involves pultrusion molding. Due to the different types of resins used, they are known as polyester fiberglass, epoxy fiberglass, and phenolic fiberglass. They possess characteristics such as being lightweight yet rigid, non-conductive, having high mechanical strength, resistance to aging, high temperature resistance, and corrosion resistance.

Due to its unique advantages, fiberglass pipes have been widely used in industries such as petroleum, power generation, chemical engineering, papermaking, urban water supply and drainage, factory wastewater treatment, seawater desalination, and gas transportation.

2. Main Features

1. Excellent corrosion resistance. Because the main raw materials of fiberglass are unsaturated polyester resin and glass fiber, it can effectively resist corrosion from acids, alkalis, salts, untreated domestic sewage, corrosive soil, chemical wastewater, and numerous chemical liquids. Under normal circumstances, it can maintain safe operation for a long time.

2. Good aging resistance and heat resistance. Fiberglass pipes can be used for a long time in a temperature range of -40℃ to 70℃, and with specially formulated high-temperature resistant resins, they can operate normally at temperatures above 200℃.

3. Good frost resistance. Even when ice forms inside the pipe at temperatures below -20℃, it will not crack due to freezing.

4. Lightweight and high strength. The relative density is between 1.5 and 2.0, only 1/4 to 1/5 of carbon steel, but the tensile strength is close to or even exceeds that of carbon steel, and the specific strength is comparable to high-grade alloy steel. Therefore, it is highly effective in applications requiring weight reduction, such as in aviation, rockets, spacecraft, and high-pressure vessels.

5. Good design flexibility. Various structural products can be flexibly designed to meet usage requirements, resulting in excellent overall product integrity.

6. Good wear resistance. A comparative test was conducted by filling pipes with water containing a large amount of mud and sand and rotating them to simulate wear. After 3 million rotations, the wear depth of the inner wall of the pipes was measured as follows: 0.53 mm for steel pipes coated with tar and enamel, 0.52 mm for steel pipes coated with epoxy resin and tar, and 0.21 mm for surface-hardened steel pipes and fiberglass pipes. This shows that fiberglass has good wear resistance.

7. Good electrical and thermal insulation. Fiberglass is a non-conductor, and the electrical insulation of the pipes is excellent, with an insulation resistance of 10¹²-10¹⁵ Ω·cm. It is most suitable for use in areas with dense power transmission and telecommunication lines and areas prone to lightning strikes. The thermal conductivity of fiberglass is very low, only 0.23, which is five thousandths of that of steel, resulting in excellent thermal insulation performance of the pipes.

8. Low friction resistance and high conveying capacity. The inner wall of fiberglass pipes is very smooth, with very low roughness and friction resistance. The roughness coefficient is 0.0084, while the n value for concrete pipes is 0.014, and for cast iron pipes it is 0.

3. Manufacturing Process

There are three main types of fiberglass pipe manufacturing processes: reciprocating filament winding process, continuous filament winding process, and centrifugal casting process.

Reciprocating Filament Winding Process (a fixed-length method): In this process, the resin impregnation tank moves back and forth with the rotating mandrel. Long glass fibers are laid at a certain angle relative to the mandrel axis. The laying angle (i.e., winding angle) is controlled by the ratio of the impregnation tank's moving speed to the mandrel's rotational speed. The translational movement of the impregnation tank is controlled by a computerized electromechanical system. The number of winding layers gradually increases until the designed wall thickness is reached. After winding, the resin in the product is substantially cured. After curing, the mandrel is removed from the fiberglass pipe.

Continuous Filament Winding Process (a continuous method): In this process, the pipe moves through a feeding station that supplies resin-impregnated roving, chopped fiberglass, and a resin-sand mixture. The pipe is manufactured while the mandrel continuously moves forward.

Centrifugal Casting Process (a fixed-length method): In this process, chopped glass fiber reinforcement and sand are fed into a steel mold fixed on bearings. Unsaturated resin with a catalyst is injected into one end of the steel mold to impregnate the reinforcement material. Under the action of centrifugal force, the resin displaces the air in the fibers and fillers, thus creating a dense, pore-free composite material. Due to the centrifugal force, a smooth, glossy, resin-rich inner surface layer is formed on the inner wall of the pipe. The pipe is cured at a higher temperature. Pipes manufactured using this method are also called fiberglass reinforced plastic sand pipes.

Currently, there are far more manufacturers using the reciprocating filament winding process than the other two production processes worldwide. One reason is that fiberglass pipes manufactured using the reciprocating filament winding process have a wider range of applications and better applicability. 

4. Development and Applications

Due to their unique performance advantages, fiberglass rods and tubes have been widely used in more than a dozen related industries, including aerospace, railways, decorative architecture, home furnishings, advertising displays, arts and crafts, building materials and sanitary ware, yachts and boats, sports equipment, and environmental sanitation engineering. They have received widespread acclaim and have become a favored product for businesses in the new era of the materials industry. Fiberglass products also differ from traditional material products, significantly outperforming them in terms of performance, applications, and lifespan. Their ease of shaping, customizability, and ability to be produced in a wide range of colors have made them highly popular with businesses and consumers, leading to an ever-increasing market share and promising future prospects!