Various composite molding processes

Various composite molding processes
Continuous molding process
Continuous molding process of composite products refers to the whole process starting from inputting raw materials, going through the processes of glue impregnation, molding, curing, demolding, cutting, etc., until finally obtaining the finished products, which is carried out in a continuous manner.

According to the different products, continuous molding process is divided into three kinds of continuous pultrusion molding process, continuous winding molding process and continuous plate making process.
Continuous winding molding process is mainly used to produce FRP pipes and tanks of different calibers. The characteristics of continuous winding machine are: high production efficiency, stable product quality, low labor intensity, saving raw materials, reducing the number of mandrels, etc. However, this process has high technical content, large investment in equipment, and great difficulty in diameter change. Another process is the combination of plastic pipe extrusion technology and fiber winding process, plastic lined FRP pipe, extruded plastic pipe at the same time play a core mold and anti-corrosion lining two roles.
Pultrusion molding process is mainly used for the production of various FRP profiles, such as FRP rods, I-beam, angle, groove, square, hollow belly and shaped cross-section profiles. At present, the largest pultrusion molding machine, can produce section of 800mm × 800mm hollow fiberglass reinforced plastic profiles. New pultrusion molding technology continues to emerge, such as RIM pultrusion molding machine, curved profile pultrusion process.
Continuous plate process is mainly used for glass fiber felt, cloth as reinforcing materials, continuous production of various specifications of flat plate, corrugated plate and laminated structural panels.
Continuous molding process common features: ① production process is completely mechanized body automation, high production efficiency; ② production process is uninterrupted, the length of the product is not limited; ③ products do not need post-processing, the production process of edge waste less, saving raw materials and energy; ④ product quality and stability, repeatability, high yield; ⑤ easy to operate, save manpower, good labor conditions; ⑥ low cost.
Pultrusion molding process

Pultrusion molding process is to impregnated with resin glue continuous fiberglass bundles, tapes or cloth, etc., under the action of traction, through the extrusion die molding, curing, continuous production of unlimited length of FRP profiles. This process is most suitable for the production of various cross-section shapes of FRP profiles, such as rods, tubes, solid profiles (I-beam, groove, square profiles) and hollow-belly profiles (door and window profiles, blades, etc.).
Pultrusion molding is a special process in the molding process of composite materials, the advantages are: ① the production process is fully automated control, high production efficiency; ② pultrusion molding products in the fiber content can be up to 80%, soaking in tension, to give full play to the role of reinforcing materials, high strength products; ③ products longitudinal and transverse strength can be adjusted to meet the use of products with different mechanical properties; ④ No edge waste in the production process, the product does not require post-processing, so save labor, save raw materials, save energy; ⑤ product quality is stable, repeatability is good, the length can be cut off arbitrarily.
The disadvantage of pultrusion molding process is that the product shape is monotonous, only production line-shaped profiles, and the transverse strength is not high.
(1) Raw materials for pultrusion process
① Resin matrix In the pultrusion process, the most widely used is unsaturated polyester resin, accounting for more than 90% of the resin used in this process, in addition to epoxy resins, vinyl resins, thermosetting methacrylic resins, modified phenolic resins, flame-retardant resins and so on.
② reinforcing materials pultrusion process with reinforcing materials, mainly glass fibers and their products, such as untwisted roving, continuous fiber mats and so on. In order to meet the special performance requirements of the product, you can choose aramid fiber, carbon fiber and metal fiber. No matter which kind of fiber, used in pultrusion process, its surface must be treated, so that it can be well bonded with the resin matrix.
(3) auxiliary materials pultrusion process of auxiliary materials are mainly mold release agent and filler.

(2) Pultrusion molding die
Mold is pultrusion molding technology is an important tool, generally by the pre-molding mold and molding die two parts. ① Pre-forming mold In the pultrusion molding process, reinforcing materials impregnated with resin (or impregnated at the same time), before entering the molding die, must be composed of a set of guiding elements of the pre-forming mold, the role of the pre-forming mold will be impregnated with reinforcing materials, in accordance with the profile cross-section configuration form, and gradually formed to approximate the molding die-controlled shape and size of the pre-forming body, and then into the molding die, which can ensure that products The yarn content of the section is uniform. ② molding die The ratio of the cross-sectional area of the molding die to the cross-sectional area of the product should generally be greater than or equal to 10, in order to ensure that the mold has sufficient strength and rigidity, and the heat distribution after heating is uniform and stable. Pultrusion mold length is based on the molding process traction speed and resin gel curing speed decision to ensure that the product is pulled out to reach the degree of demolding and curing. General use of steel chrome-plated, die cavity surface requirements of clean, wear-resistant, to reduce the pultrusion molding is the