The hottest thermoplastic composite molding proces

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Thermoplastic composite molding process

thermoplastic composite is the general name of various thermoplastic resins reinforced with glass fiber, carbon fiber, aramid fiber, etc., which is called fiber reinforced thermo plastics (FRTP) abroad. Due to the different types of thermoplastic resins and reinforcing materials, the production process and the properties of the composites made of them are very different

from the perspective of production technology, plastic composites are divided into short fiber reinforced composites and continuous fiber reinforced composites: (1) short fiber reinforced composites ① injection molding process; ② Extrusion molding process; ③ Centrifugal molding process. (2) Continuous fiber reinforced and long fiber reinforced composites ① prepreg molding; ② Sheet molding plastic stamping; The material is scientifically compounded with polyurethane (PU) materials and materials containing silicone components. ③ vacuum molding of sheet molding compound; ④ Pre impregnated yarn winding; ⑤ Pultrusion molding

The special properties of thermoplastic composites are as follows:

(1) the density of thermoplastic composites with low density and high strength is 1.1 ~ 1.6g/cm3, only 1/5 ~ 1/7 of steel, and 1/3 ~ 1/4 lighter than thermosetting glass fiber reinforced plastics. It can obtain higher mechanical strength with smaller unit mass. Generally speaking, whether general-purpose plastics or engineering plastics, after being reinforced with glass fiber, they will obtain higher reinforcement effect and improve the strength and application grade

(2) the physical, chemical and mechanical properties of thermoplastic composites with large degree of freedom of performance designability are designed by reasonably selecting the type of raw materials, proportion, processing method, fiber content and ply method. Because there are more kinds of matrix materials of thermoplastic composites than thermosetting composites, the freedom of material selection and design is much greater

(3) thermal properties generally, the service temperature of plastic is 50 ~ 100 ℃, which can be increased to more than 100 ℃ after being reinforced with glass fiber. The hot deformation temperature of nylon 6 is 65 ℃, and the hot forming temperature can be increased to 190 ℃ after being reinforced with 30% glass fiber. The heat resistance of PEEK resin can reach 220 ℃, and the service temperature can be increased to 310 ℃ after being reinforced with 30% glass fiber. Such high heat resistance cannot be achieved by thermosetting composites. The linear expansion coefficient of thermoplastic composites is 1/4 ~ 1/2 lower than that of unreinforced plastics, which can reduce the shrinkage rate in the molding process and improve the dimensional accuracy of products. Its thermal conductivity is 0.3 ~ 0.36w (㎡ K), which is similar to thermosetting composites

(4) chemical corrosion resistance the chemical corrosion resistance of composite materials is mainly determined by the performance of matrix materials. There are many kinds of thermoplastic resins, and each resin has its own anti-corrosion characteristics. Therefore, the matrix resin can be optimized according to the service environment and medium conditions of composite materials, which can generally meet the use requirements. The water resistance of thermoplastic composites is better than that of thermosetting composites

(5) electrical properties generally, thermoplastic composites have good dielectric properties, do not reflect radio waves, and have good microwave transmission performance. Because the water absorption of thermoplastic composites is smaller than that of thermosetting FRP, its electrical properties are better than the latter. Adding conductive materials to thermoplastic composites can improve their conductivity and prevent static electricity

(6) waste can be recycled, thermoplastic composites can be processed repeatedly, and waste products and leftover materials can be recycled without causing environmental pollution

because thermoplastic composites have many special properties better than thermosetting glass fiber reinforced plastics, they are widely used in many fields. From the analysis of foreign applications, thermoplastic composites are mainly used in vehicle manufacturing industry, electromechanical industry, chemical anti-corrosion and construction engineering

1. Injection molding process

injection molding is the main production method of thermoplastic composites, which has a long history and is the most widely used. Its advantages are: short molding cycle, minimum energy consumption, high product accuracy, one-time molding of products with complex switches and inserts, the first mock examination can produce several products, and high production efficiency. The disadvantage is that it cannot produce fiber reinforced composite products and has high requirements for mold quality. According to the current technological development level, the maximum product of injection molding is 5kg, and the minimum is 1g. This method is mainly used to produce various mechanical parts, building products, home appliance shells, electrical materials, vehicle accessories, etc

2. Extrusion molding process

extrusion molding is one of the widely used processes in the production of thermoplastic composite products. Its main characteristics are continuous production process, high production efficiency, simple equipment, easy to master technology and so on. Extrusion molding process is mainly used to produce tubes, rods, plates and special-shaped cross-section products. Reinforced plastic pipe and glass fiber reinforced profiled sections of doors and windows have a large market in China

3. Winding process

the winding process principle of thermoplastic composites is the same as that of winding machine equipment and thermosetting glass. The difference is that the reinforcing material of thermoplastic composite winding products is not glass fiber roving, but pre impregnated yarn impregnated with glue (thermoplastic resin). Therefore, it is necessary to add a pre soaking yarn preheating device and a heating pressure roller on the winding machine. During winding, the prepreg yarn is heated to the softening point first, then the contact point with the core mold is heated, and the pressure roller is pressurized to fuse it into a whole

4. Pultrusion molding of thermoplastic composites

the pultrusion molding process of thermoplastic composites is basically similar to that of thermosetting FRP. As long as the dipping method before entering the mold is modified, the equipment for producing thermosetting FRP can be used. There are two kinds of reinforcing materials for the production of thermoplastic composite pultrusion products: one is pre impregnated yarn or pre impregnated belt after dipping, and the other is non impregnated fiber or fiber belt

5. Welding layer method

this method uses the weldability of thermoplastic composites to produce composite plates. The method is as follows: first, press and lay a layer of prepreg (generally 500mm wide) on the workbench. When laying the second layer of prepreg, start the welding device of the pressure roll to make the prepreg enter under the pressure roll. The welding device makes the upper and lower layers of prepreg heat and melt at the same time within a few seconds. When the machine moves forward, the prepreg sticks together under the pressure of the pressure roll (0.3MPa). Such repetition can produce plates of any thickness

6. Stamping and forming process of thermoplastic sheet molded products

stamping and forming of thermoplastic sheet molded products is different from thermosetting SMC pressing and forming. It needs to preheat the blank first, and then put the mold to press and form

7. Connection technology of thermoplastic composites

there are many connection methods of thermoplastic composites. Examples are as follows: ① riveting rivets used for riveting thermoplastic composites are generally made of continuous fiber reinforced thermoplastic, preferably pultruded bars. During construction, the rivet shall be preheated to a temperature that can be pressurized and plasticized, and the rivet and the hole diameter shall be closely matched, neither large nor small. Metal bolts can also be used. The advantages of riveting are good impact resistance, no electrochemical corrosion and low price. ② The welding treatment of welding thermoplastic composites is to heat the welding surface of the connected material to the molten state, and then lap and pressurize it to make it connected as a whole. The welding principle of composite materials is similar to that of plastics, but it must be noted that the fiber reinforcement effect of the weld cannot be reduced much. ③ Butt welding of pipe fittings there are two kinds of butt welding methods of thermoplastic composite pipes: direct butt welding and reinforcement butt welding. The advantage of this connection method is that the process is simple, it can be constructed on site, there is no need to machine the pipe, the connection strength is high, and it is not easy to break. The disadvantage is that the cost is high and the process requirements are strict. It is necessary to ensure that the size fits closely. ④ For winding welding, the prepreg tape is wound manually or mechanically along the weld. At the same time, the flame gun is used to heat and melt the contact point to make it stick firmly with the connected parts. When selecting the prepreg belt, pay attention to the direction and content of fiber. This method is more practical, and the connected material can retain good performance, but it is prone to uneven heating. ⑤ Ultrasonic welding of thin plate this method uses ultrasonic to heat and weld the joint, which can generally obtain high connection strength

information source: plastic wood

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