Reinforced plastic are plastic containing reinforcing materials and are an important polymer composite material. Reinforced plastic are divided into reinforced thermosetting plastic and reinforced thermoplastic plastic, with thermosetting being the main type.

Overview

Thermosetting resins used in reinforced plastic include: unsaturated polyesters, phenolic resins, epoxy resins, silicone resins, alkyd resins, and melamine-formaldehyde resins; the thermoplastic resins used include: polyamide, fluororesin, polycarbonate, polysulfone, acrylic resin (polymers of acrylic acid or methacrylic acid and their esters), polyoxymethylene, ABS resin, polyethylene, and polypropylene. The reinforcing materials used include metal materials, non-metallic materials, and polymer materials, all of which are mainly fibrous materials. Commonly used reinforcing fibers include glass fiber, carbon fiber, asbestos fiber, boron fiber, and aromatic polyamide fiber. Reinforced materials have higher strength and modulus. Resins have many inherent excellent physical, chemical (corrosion resistance, insulation, radiation resistance, instantaneous high temperature ablation resistance, etc.) and processing properties. After the resin and the reinforcing material are compounded, the reinforcing material can enhance the mechanical or other properties of the resin, while the resin can play a role in bonding and transferring loads to the reinforcing material, so that the reinforced plastic has excellent properties (see table).

Plastic coupling agent

In order to improve the bonding ability between the resin and the reinforcing material, some reinforcing materials need to be surface treated with a coupling agent before use. Different coupling agents are selected for different resins and reinforcing materials. Taking glass fiber as an example, the coupling agents used are mainly chromium complexes and silanes. The commonly used chromium complex is methacrylic acid chromium chloride complex (also known as Wolan), one end of which acts on glass fiber (glass) containing silanol groups, that is:

The other end can react with epoxy resin, polyester and phenolic resin, thereby playing a role in bonding resin and glass fiber. Vinyl triethoxysilane is also a commonly used silane coupling agent, and its effect on glass fiber is similar to that of Wolan.

Molding method

According to whether the molding pressure is lower or higher than 7MPa, it can be divided into low-pressure method and high-pressure method; according to the process characteristics, it can be divided into hand lay-up molding, lamination molding, compression molding, injection molding and winding molding. Hand lay-up molding is also called contact molding, that is, first spray a layer of resin on the mold with a release agent on the surface, and then lay a layer of reinforcement material. Each layer is evacuated once until the required thickness is reached, and then the curing treatment is carried out, and then the mold is demolded and repaired. The advantage of this molding method is that it can be used to manufacture large products, and the equipment and operation are simple; the disadvantage is low production efficiency and poor product accuracy. Winding molding is mainly used for the manufacture of storage tanks, large pipelines and pressure-resistant containers. The process is to regularly wind the fiber (or fabric) impregnated with resin on the core mold or lining equivalent to the shape of the product, and then heat and cure it. According to the different manufacturing methods and uses, the core mold is divided into non-removable metal core mold, removable metal core mold, breakable core mold (made of gypsum, quartz sand, paraffin or clay), rubber bag core mold (rubber bag inflated by compressed air) and combined core mold (metal-rubber, metal-gypsum, etc.). Non-removable core mold can be used for any core mold used as lining to improve the strength or air tightness of the product.

The components contain reinforcing materials such as high-strength fibers, which greatly improve some mechanical properties compared with the original resin. It is also a polymer composite material. There are thermoplastic reinforced plastic and thermosetting reinforced plastic depending on the resin used. The reinforcing materials used are mostly glass fiber, carbon fiber, polyaramid fiber, and asbestos fiber, ceramic fiber and cotton fiber can also be used. Reinforced plastic not only retain the excellent properties of the original resin, but also greatly improve the mechanical properties. It can be used as electrical insulating materials, decorative materials, and in machinery, automobiles, and aerospace.

Plastic classification

Classification of reinforced plastic

1. According to the shape of the reinforcing material, it can be divided into:

1) Granular reinforced plastic: such as calcium plastic.

2) Fiber reinforced plastic: such as glass fiber or glass cloth reinforced plastic.

3) Sheet reinforced plastic: such as mica reinforced plastic.

2. According to the material of the reinforcing material, it can be divided into:

1) Cloth-based, asbestos reinforced plastic: such as rag reinforced plastic.

2) Inorganic mineral filled plastic: such as quartz, mica filled plastic.

3) Glass fiber reinforced plastic: such as prepreg.

4) Special fiber reinforced plastic such as SMC and BMC: such as carbon fiber and Kevlar fiber reinforced plastic.

5) Metal fiber reinforced plastic: such as steel wire reinforced plastic.

Glass Fiber Plastic

Glass fiber reinforced plastic (GRP), commonly known as FRP, is the main type of polymer composite material. It has stronger impact resistance than ordinary plastic; it is light, mechanically strong and corrosion-resistant. The scientific name of FRP is glass fiber reinforced plastic. It is a composite material with glass fiber and its products (glass cloth, tape, felt, yarn, etc.) as reinforcing materials and synthetic resin as matrix material. The concept of composite material refers to a material that cannot meet the use requirements and needs to be combined with two or more materials to form another material that can meet people's requirements, that is, a composite material. For example, a single glass fiber, although it has high strength, is loose between fibers and can only withstand tension, but cannot withstand bending, shearing and compressive stress. It is also not easy to make a fixed geometric shape and is a soft body. If they are bonded together with synthetic resin, they can be made into various hard products with fixed shapes, which can withstand both tensile stress and bending, compression and shear stress. This constitutes a glass fiber reinforced plastic matrix composite material. Because its strength is equivalent to that of steel, and it contains glass components, it also has the color, shape, corrosion resistance, electrical insulation, heat insulation and other properties of glass, just like glass. In history, it has formed the easy-to-understand name "glass reinforced plastic". This term was proposed by Comrade Lai Jifa, former Minister of the Ministry of Building Materials Industry in 1977. It has been expanded from the building materials system to the whole country and is still widely used.

It can be seen that the meaning of glass reinforced plastic refers to reinforced plastic with glass fiber as reinforcing material and synthetic resin as binder. It is called glass fiber reinforced plastic abroad.

With the development of China's glass reinforced plastic industry, as a plastic-based reinforcing material, it has expanded from glass fiber to carbon fiber, boron fiber, aramid fiber, alumina fiber and silicon carbide fiber. Undoubtedly, reinforced plastic made of these new fibers are some high-performance fiber-reinforced composite materials, which can no longer be summarized by the common name of glass reinforced plastic.

Taking into account the origin and development of history, glass reinforced plastic is usually used.

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