The composite process of glass fiber reinforcement and epoxy resin curing is the core of epoxy insulated pipes, and its manufacturing process covers five key links: material selection, fiber winding, resin impregnation, curing molding, and post-treatment, forming an insulation structure that combines high mechanical strength and excellent electrical performance.
Material selection is the starting point of the process. Glass fiber adopts alkali free and untwisted type, with a diameter usually ranging from 5-15 μ m. The warp and weft density can be adjusted according to the diameter requirements, such as 8 × 8 or 10 × 10 specifications, to ensure a tight fit between fiber layers. Epoxy resin is mainly composed of bisphenol A type (such as E-51), which has a high epoxy value and good electrical properties after curing. When combined with anhydride curing agents (such as methyl tetrahydrophthalic anhydride), it can achieve low-temperature curing and avoid damage to fibers caused by high temperatures.
Fiber winding is the key to structural reinforcement. Using wet winding technology, glass fibers impregnated with epoxy resin are spiral wound around a metal core mold at an angle of 50-60 °, and the bending strength is improved through multi-layer cross laying. For example, Taipu Electric's winding tube adopts a composite structure of longitudinal winding with a thickness of 3.5mm, circumferential winding with 2 layers, and longitudinal winding with a thickness of 3.5mm, resulting in a strength ratio of 3:1 between the axial and circumferential directions of the tube body, meeting the mechanical requirements of high-voltage equipment.
Resin impregnation requires control of the adhesive content and permeability. After mixing resin and curing agent in a ratio of 100:45, the resin is fully penetrated into the fiber gaps through vacuum impregnation or pressure impregnation, and the gel content is controlled at 26% -30% to avoid pore defects. Part of the process involves wrapping a heat shrinkable plastic tube in the outer layer and using hot air shrinkage to achieve secondary pressure, further increasing the density.
The solidification molding adopts a step heating process. Raise the temperature to 95 ℃ at a rate of 3 ℃/10min and hold for 3 hours to preliminarily crosslink the resin; Raise to 160 ℃ and hold for 4 hours to complete deep curing, with a final heat distortion temperature (HDT) of over 180 ℃. This process requires strict control of the temperature uniformity inside the furnace to prevent local overheating and delamination of the fiber resin interface.
Post processing includes demolding, cutting, and surface finishing. After demolding, the end face is cut using a CNC machine to ensure a verticality error of less than 0.1mm. The surface is sanded with sandpaper and coated with protective paint to enhance corrosion resistance and wear resistance. The final product needs to pass 100kV high voltage testing and partial discharge detection to ensure a dielectric strength>50kV/mm and a partial discharge capacity<5pC.