Abbreviation for thermoplastic composite molding process: FRTP

Due to the different types of thermoplastic resins and reinforcing materials, their production processes and the properties of the composite materials they produce vary greatly.

From the perspective of the production process, plastic composite materials are divided into two categories: short fiber reinforced composite materials and continuous fiber reinforced composite materials:

The thermoplastic composite material is a general term for reinforcing various thermoplastic resins such as glass fiber, carbon fiber, and aramid fiber. It is called FRTP (Fiber Rinforced Thermo Plastics) abroad.

(A) Continuous fiber-reinforced and long-fiber-reinforced composite materials 

① prepreg compression molding; 

② sheet molding molding; 

③ sheet molding vacuum molding; 

④ prepreg winding molding; 

⑤ pultrusion.

(B) Short fiber reinforced composite materials 

① injection molding process; 

② extrusion molding process; 

③ centrifugal molding process.

(A) The special properties of thermoplastic composite materials are as follows:

(1) The degree of freedom in performance designability The physical properties, chemical properties, and mechanical properties of large thermoplastic composites are designed by rationally selecting the types of raw materials, blending ratios, processing methods, fiber contents, and lamination methods. Because there are many more types of matrix materials for thermoplastic composites than thermosetting composites, the freedom of material selection is much greater.

(2) The density of the thermoplastic composite material with small density and high strength is 1.1 ～ 1.6g / cm3, which is only 1/5 ～ 1/7 of steel, and it is 1/3 ～ 1/4 lighter than thermosetting glass steel. It can achieve higher mechanical strength with smaller unit mass. Generally speaking, no matter whether it is general-purpose plastic or engineering plastic, reinforced with glass fiber, it will get a higher reinforcing effect and improve the grade of strength application.

(3) The chemical resistance of chemically resistant composite materials is mainly determined by the properties of the base material. There are many types of thermoplastic resins, and each resin has its own corrosion protection characteristics. Therefore, it can be based on the environment and media of the composite material Conditions, the matrix resin is optimized, and generally can meet the requirements for use. Thermoplastic composites have better water resistance than thermoset composites.

(4) Thermal performance The general plastic is used at a temperature of 50 to 100 ° C. After being reinforced with glass fiber, it can be raised to more than 100 ° C. The heat distortion temperature of nylon 6 is 65 ° C. After being reinforced with 30% glass fiber, the heat deformation temperature can be increased to 190 ° C. Polyether ether ketone resin has a heat resistance of 220 ° C. After being reinforced with 30% glass fiber, the use temperature can be increased to 310 ° C. Such a high heat resistance cannot be achieved by thermosetting composite materials. The linear expansion coefficient of the thermoplastic composite material is 1/4 to 1/2 lower than that of the unreinforced plastic, which can reduce the shrinkage rate during the molding process and improve the dimensional accuracy of the product. Its thermal conductivity is 0.3 ～ 0.36W (㎡ • K), which is similar to thermosetting composite materials.

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

(6) The waste material can be recycled and reused. The thermoplastic composite material can be repeatedly processed and formed, and the waste and leftover materials can be recycled without causing environmental pollution.

Because thermoplastic composites have many special properties that are superior to thermoset FRP, their application fields are very wide. From the analysis of foreign applications, thermoplastic composites are mainly used in vehicle manufacturing industry, mechanical and electrical industry, chemical anticorrosion and construction engineering.

(Two) thermoplastic composite material molding process FRTP

1. Injection molding process

Injection molding is the main production method of thermoplastic composites, with a long history and the widest application. Its advantages are: short molding cycle, minimum energy consumption, high product accuracy, one-time moldable switches and products with inserts, which can produce several products in one mold, and high production efficiency. Disadvantages are the inability to produce fiber-reinforced composite products and higher requirements for mold quality. According to the current level of technological development, the largest product for injection molding is 5kg and the smallest is 1g. This method is mainly used to produce various mechanical parts, construction products, home appliance housings, electrical materials, and vehicle accessories.

2.Extrusion process

Extrusion is one of the more widely used processes in the production of thermoplastic composite materials. Its main features are continuous production process, high production efficiency, simple equipment and easy to master technology. The extrusion molding process is mainly used to produce products such as tubes, rods, plates and profiled sections. Reinforced plastic tube glass fiber reinforced door and window profiled profiles have a large market in China.

3. Winding forming process

The winding molding process principle and winding machine equipment of thermoplastic composite materials are the same as those of thermosetting glass. The difference is that the reinforcing material of thermoplastic composite material winding products is not glass fiber roving, but prepreg that has been dipped (thermoplastic resin). Therefore, it is necessary to add a prepreg yarn preheating device and a heating pressure roller to the winding machine. When winding, the prepreg yarn is first heated to the softening point, then the contact point with the core mold is heated, and the pressure roller is pressed to make it weld into a whole.

4.Pultrusion of thermoplastic composite materials

The pultrusion process of thermoplastic composites is basically similar to that of thermoset FRP. As long as the dipping method before entering the mold is modified, the equipment for producing thermoset FRP can be used. There are two types of reinforcements used in the production of thermoplastic composite pultruded products: one is impregnated prepreg yarn or prepreg tape, and the other is unimpregnated fiber or fiber tape.

5.Legal layer is legal

This method uses the weldability of thermoplastic composite materials to produce composite sheet materials. The method is as follows: firstly lay a layer of prepreg (usually 500mm wide) on the workbench; when laying the second layer of prepreg, start the welding device of the pressure roller to make the prepreg enter the pressure roller, and the welding device makes The two layers of prepreg are simultaneously heated and melted within a few seconds. When the machine moves forward, the prepreg is bonded into one under the pressure of the pressure roller (0.3 MPa). Repeat this way to produce plates of any thickness.

6. Stamping process for thermoplastic sheet molding products

The stamping of thermoplastic sheet molding is different from the thermosetting SMC compression molding. It first preheats the blank and then puts the mold under pressure to form.

7. thermoplastic composite materials connection technology

There are many ways to join thermoplastic composite materials, for example:

a. The welding process of welding thermoplastic composite materials is to heat the welding surface of the material to be joined to a molten state, and then overlap and pressurize it to form a whole. The welding principle of composite materials is similar to that of plastic welding, but it must be noted that the fiber reinforcement effect at the welding place cannot be reduced much.

b. riveting rivets for riveting of thermoplastic composite materials are generally made of continuous fiber reinforced thermoplastics, preferably pultruded rods. During construction, the rivet is preheated to a temperature that can be pressurized and deformed. The rivet and the hole diameter should be closely matched, and cannot be large or small. Metal bolts can also be used. The advantages of riveting are good impact resistance, no electrochemical corrosion, and low price.

c. Ultrasonic welding of thin plates This method is to heat-weld the joints with ultrasonic waves. Generally, a higher connection strength can be obtained.

d. Butt welding methods for butt welding of thermoplastic composite materials. There are two types of butt welding: direct butt welding and reinforced butt welding. The advantage of this connection method is that the process is simple and can be constructed on site without mechanical processing of the pipe. The connection strength is high and it is not easy to break. The disadvantage is that the cost is high, the process requirements are strict, and the dimensions must be closely matched.

e. Pre-impregnated tape for winding welding is manually or mechanically wound along the weld, and the contact point is heated and melted with a flame spray gun to make it adhere to the connected part. When selecting a prepreg tape, pay attention to the direction and content of the fibers. This method is more practical, and the material being connected can retain good performance, but it is prone to uneven heating.