Insulated epoxy fiberglass is “glass reinforced plastic”
First, what is FRP?
FRP, also known as GFRP, is a fiber reinforced plastic, generally referred to as a glass fiber reinforced unsaturated polyester, epoxy resin and phenolic resin matrix. Reinforced plastics made of glass fibers or their products as reinforcing materials are called glass fiber reinforced plastics, or glass reinforced plastics, unlike tempered glass.
Because of the different types of resins used, there are different types of polyester glass reinforced plastics, epoxy glass reinforced plastics, and phenolic glass reinforced plastics. Light and hard, non-conductive, stable in performance, high in mechanical strength, low in recycling and corrosion resistant. Machine parts and automobiles, ship casings, etc. can be manufactured instead of steel.
FRP is a fiber reinforced plastic, commonly known as FRP (Fiber Reinforced Plastics), which is a fiber reinforced composite plastic. According to the different fibers used, it is divided into glass fiber reinforced composite plastic (GFRP), carbon fiber reinforced composite plastic (CFRP), boron fiber reinforced composite plastic and so on. It is a composite material of glass fiber and its products (glass cloth, belt, felt, yarn, etc.) as a reinforcing material and synthetic resin as a base material.
The fiber reinforced composite material is composed of reinforcing fibers and a matrix. The diameter of the fiber (or whisker) is very small, generally below 10 μm, the defect is small and small, and the strain at break is about 30 parts per thousand. It is a brittle material, which is easily damaged, broken and corroded. The matrix has much lower strength and modulus than the fiber, but it can withstand large strains, often has viscoelasticity and elastoplasticity, and is a ductile material.
Second, the principle of FRP:
The concept of composite material means that one material cannot meet the requirements of use, and it is necessary to combine two or more materials to form another material that can meet people’s requirements, that is, composite material. For example, a single type of glass fiber, although high in strength, is loose between fibers, can only withstand tensile forces, cannot withstand bending, shearing, and compressive stress, and is not easily formed into a fixed geometry, and is a soft body. If they are bonded together with synthetic resin, they can be made into a variety of rigid articles with a fixed shape that can withstand tensile stress and withstand bending, compression and shear stress. This constitutes a glass fiber reinforced plastic matrix composite.
Because its strength is equivalent to steel and glass components, it also has the color, shape, corrosion resistance, electrical insulation, heat insulation and other properties of glass. Like glass, it has historically formed this easy-to-understand name “FRP”. This term was proposed by the former Minister of Construction Materials Industry Lai Jifa in 1958 and expanded from the building materials system to the whole country.
The meaning of FRP refers to the reinforced plastics made of glass fiber as reinforcing material and synthetic resin as binder. In other countries, it is called glass fiber reinforced plastic. With the development of China’s FRP industry, as a plastic-based reinforcement material, it has been expanded from glass fiber to carbon fiber, boron fiber, aramid fiber, alumina fiber and silicon carbide fiber. Undoubtedly, these new fiber made of reinforced plastic , is a high-performance fiber reinforced composite material, and the common name of glass fiber reinforced plastic can not be summarized. Considering the origin and development of history, glass-steel composites are usually used, so the name is more comprehensive.
(Glass steel structure drawing)
Third, FRP product classification:
FRP tank: FRP storage tank, hydrochloric acid storage tank, sulfuric acid storage tank, reaction tank, anti-corrosion storage tank, chemical storage tank, transportation storage tank, food tank, fire tank, etc.;
Glass steel pipe: FRP pipe, FRP sand pipe, FRP pipe, FRP cable pipe, FRP pipe, FRP pipe, etc.;
Tower: drying tower, washing tower, desulfurization tower, acid mist purification tower, exchange column, etc.;
Bathroom: bathroom chassis, bathroom ceiling.
Others: angle steel, wire trough, pultruded profiles, tees, crosses, FRP gratings, etc.
Fourth, the advantages and disadvantages of FRP:
A. Lightweight and high strength: the relative density is between 1.5 and 2.0, only 1/4~1/5 of carbon steel, but the tensile strength is close to or even higher than that of carbon steel, and the specific strength can be compared with high-grade alloy steel. . As a result, it has achieved excellent results in aerospace, rockets, spacecraft, high-pressure vessels, and other applications that require weight reduction. Some epoxy FRPs have tensile, bending and compressive strengths of more than 400 MPa.
B. Corrosion resistance: FRP is a good anti-corrosion material with good resistance to atmospheric, water and general concentrations of acids, bases, salts and various oils and solvents. It has been applied to all aspects of chemical corrosion protection and is replacing carbon steel, stainless steel, wood, non-ferrous metals, etc.
C. Good electrical performance: It is an excellent insulating material used to make insulators. Good dielectric properties are still protected at high frequencies. It has good microwave permeability and has been widely used in radar antenna covers.
D. Good thermal performance: FRP has low thermal conductivity, 1.25~1.67kJ/(m·h·K) at room temperature, and only 1/100~1/1000 of metal, which is an excellent thermal insulation material. In the case of instantaneous ultra-high temperature, it is an ideal thermal protection and ablation resistant material, which can protect the spacecraft from high-speed airflow at 2000 °C.
E, designability is good:
(1) Various structural products can be flexibly designed according to needs to meet the requirements of use, and the products can be well integrated.
(2) The material can be fully selected to meet the performance of the product, such as: it can be designed to be resistant to corrosion, resistant to transient high temperatures, and has a particularly high strength in a certain direction, good dielectric properties, and the like.
F, excellent craftsmanship:
(1) The molding process can be flexibly selected according to the shape, technical requirements, use and quantity of the product.
(2) The process is simple, it can be molded at one time, and the economic effect is outstanding, especially for products with a complicated shape and less forming, and the process superiority is more prominent.
A. Low modulus of elasticity: The elastic modulus of FRP is twice as large as that of wood, but 10 times smaller than that of steel (E = 2.1 × 105). Therefore, it is often insufficient in rigidity and easily deformed in the product structure. It can be made into a thin shell structure or a sandwich structure, and can also be compensated by high modulus fibers or reinforcing ribs.
B. Poor long-term temperature resistance: Generally, FRP can not be used for a long time at high temperature. The strength of general-purpose polyester FRP is obviously lower than 50 °C, generally only below 100 °C; general-purpose epoxy FRP is above 60 °C, the strength is obvious decline. However, it is possible to select a high temperature resistant resin so that a long-term operating temperature of 200 to 300 ° C is possible.
C. Aging phenomenon: Aging phenomenon is a common defect of plastics. FRP is no exception. It is easy to cause performance degradation under the influence of ultraviolet light, sand, rain, snow, chemical medium and mechanical stress.
D, low shear strength: the interlaminar shear strength is borne by the resin, so it is very low. The adhesion between layers can be improved by selecting a process, using a coupling agent, etc., and most importantly, avoiding shearing between layers during product design.
Fifth, FRP production methods:
There are basically two major categories, namely wet contact type and dry pressure forming. According to the characteristics of the process, there are hand lay-up, lamination, RTM, pultrusion, compression molding, and winding molding. Hand lay-up includes hand lay-up, bag press, spray, wet paste low pressure and moldless paste.
There are currently four types of molding methods that are most used in the world.
1 hand paste method : The main countries used are Norway, Japan, the United Kingdom, Denmark and so on.
Kenny hand lay-up products: FRP fan
Kenny hand lay-up products: FRP fan
2 injection method: the main countries used are Sweden, the United States, Norway and so on.
3 molding method: the main use of the country is Germany.
4RTM method (resin transfer molding): The main use countries are Europe and the United States, Japan.
Also: filament winding method, pultrusion method and hot potting method.
Hand paste products: glass steel fan picture
More than 90% of FRP products in China are produced by hand-paste method, and others have molding methods, winding methods, lamination methods, and the like. Japan’s hand-paste method still accounts for 50%. From the perspective of countries around the world, the hand-paste method still accounts for a considerable proportion, indicating that it still has vitality. The hand paste method is characterized by molding with a wet resin, simple equipment, low cost, and the entire product can be pasted more than 10 m at a time. The disadvantages are low mechanization, long production cycle and unstable quality. China has introduced process equipment such as squeezing, spraying and winding from abroad. With the development of FRP industry, new methods will continue to emerge.
Sixth, FRP application:
By first producing a FRP sculpture mold, we will produce and produce FRP products to meet the needs of people in real production and life.
1. FRP sculpture plaster mold
The gypsum model points are heat-resistant, inexpensive, have a small thermal conductivity, and have good copyability. Generally used to make master molds. Easy to manufacture, suitable for large products. But not durable, afraid of impact, slow drying. It is mostly used for single products and complex linear products such as embossing. Most of the gypsum used is hemihydrate gypsum, ie, plaster of Paris. Like the cement mold, the brick base and wood can be used as the skeleton foundation and then covered with a plaster layer. In order to increase the rigidity and prevent cracking, enough filler can be added to the gypsum, such as adding quartz to reduce shrinkage and cracking, and adding cement (gypsum: cement = 7:3) to increase the strength. It has also been proposed to add an appropriate amount of latex with gypsum, dilute with water to make a mold, and the strength is good, and powder is not obtained.
The plaster mold can be used as a master mold for a low melting point alloy mold to cast the alloy in a hot state. When casting a gypsum mold (sub-mold) with a gypsum master mold, the surface of the master mold should be coated with a separating agent such as potassium soap solution, transformer oil, edible oil, 20% stearic acid, 80% kerosene, or gasoline ten Vaseline. . The plaster mold can be repaired by taking a gypsum powder with a water pen. The gypsum mold drying process is: (60 ~ 120) ° C / (4 ~ 5) L, after natural cooling, gently polished with metallographic sandpaper, and then baked (100 ~ 150) ° C / (8 ~ 10) L, ( 200 to 230) ° C / (20 ~ 24) L.
2, glass steel sculpture rubber mold
The rubber mold is generally made of silicone rubber or polyurethane resin. It is used to make complex reliefs, round carvings and various shapes. It is not used alone. It must be composed of other materials such as plaster sleeve molds. It is usually used in molds for thread type pouring. Or a part that overlaps and cannot be directly demoulded, because it has a certain softness. When the outer mold is demoulded, it can be pulled out at will, such as lions, dragons and other animals or bodhisattvas, cartoon characters. Use this method when the batch size is not large.
3, glass steel sculpture parafilm
Paraffin films are used in products that are not numerous or complex in shape and are not easily demolded. For example, to make a monolithic elbow, including a 90° elbow, two elbows can be used as a master mold. After the paraffin is filled in the 90° cavity, the paraffin core is slightly removed after removing the Huff master. After finishing, the FRP is coated on the outer wall, heated and solidified to melt and flow the paraffin to obtain a whole FRP product.
In order to reduce the shrinkage deformation and increase the rigidity, about 5% of stearic acid can be added to the paraffin wax. It is easy to manufacture, easy to demould, and can be used repeatedly. But the accuracy is not high. Another method: when wet-rolling, the steel pipe can be immersed in paraffin wax melted at 70-80 °C, lifted and then immersed, repeated, until the required thickness, the surface is slightly trimmed, can be coated FRP, in order to prevent paraffin cracking, add a small amount of butter to the wax. It is also possible to coat a thin layer of cellophane on the outside of the wax as a core. After the glass reinforced plastic is cured, the heated steel tube paraffin is melted to release the mold.
4, concrete mold
Concrete molds are often used for line type rules and products with low reusability, such as spiral, wavy, circular, arched or three-dimensional grooved products. The cost is low and the rigidity is good. The bricks can be used as a foundation, and then covered with cement mortar, polished, putty, and then polished, polished, painted and other measures. This cement mold can be directly used to produce FRP products, and can also be used as a master mold for reversing FRP molds. The cement mold dries slowly, and even under normal conditions, it takes more than one week to perform surface painting such as painting.
5, glass steel sculpture wooden mold
Wood molds are mainly used for large products with flat lines. The wood mold can be used directly as a forming mold for FRP products or as a transitional mold for reversing FRP molds. The wood used for making the mold has red pine, ginkgo, fir, etc., and the water content is required to be 15%, and it is not easy to shrink and deform, and has no knot. After the wood mold is made, it can be coated with a resin (surface putty) with a thickness of 0.2 to 0.3, and then sanded from coarse to fine four times with water sandpaper. The last time it is polished with 800# or 1000# sandpaper, and then coated with polishing paste. The polisher is polished, then waxed, and the wood mold is ready. It is also possible to paint and cover the wood mold directly to make a wooden mold.
6, glass steel sculpture metal mold
Metal molds, especially steel molds, are generally used for molded products with small size and large batch size. For example, stainless steel plates with smooth surface when making FRP flat plates; angle steel and channel steel for making profiles. Because the molded product is not only pressurized, but also heated. There are also large products for uncomplicated shapes. Although brass is a common metal, it is easily attacked by resin adjuvants and adversely affects the curing of the resin. It should not be used unless the working surface has been chromed or otherwise. The manufacturing and processing of metal molds is difficult and costly.
In addition, the composition of the low-melting alloy mold is: Zn93%, Al4%, Cu3%, Mn0.5%, and when the temperature is 50-80 °C, the hardness (HB) of the alloy is about 100. It has good fluidity and poor wear resistance. It is suitable for the manufacture of plastic molding cavities with complex shapes and fine patterns. The use temperature is generally >80 °C. Another low melting point metal is 58% bismuth, 42% tin, melting point 135 °C. The low melting point alloy mold has the advantages of short molding cycle, simple process and reusability.
Seventh, FRP use:
FRP is a composite material that has developed rapidly in the past 50 years. 70% of the glass fiber production is used to make FRP. FRP has a high hardness and is much lighter than steel. It is used as a fuel tank and pipe on jet aircraft to reduce the weight of the aircraft. The astronauts who boarded the moon, the miniature oxygen cylinders they carried on their bodies, were also made of fiberglass. FRP is easy to process, stainless steel is not bad, no need for paint. China has widely used FRP to manufacture a variety of small motorboats, lifeboats, yachts, and automobile manufacturing industries, saving a lot of steel.
Because FRP is a composite material, its performance is very wide, so its market development prospects are very broad. According to relevant statistics, the types of FRP products developed by countries around the world have reached about 40,000. Although each country has its own focus on development according to its own economic development, it has basically involved various industrial sectors. After more than 40 years of development, China’s FRP industry has also achieved successful application in various fields of the national economy and played an important role in economic construction.
The main application areas of FRP are summarized as follows:
1. Construction industry: cooling tower, FRP doors and windows New, building structure, envelope structure, indoor equipment and decorative parts, FRP flat plate, wave tile, decorative board, FRP cover, sanitary ware and whole bathroom, sauna, surf bath, Building construction formwork, storage building, concrete formwork, reinforcement and solar energy utilization equipment.
2. Chemical and chemical industries: corrosion-resistant pipes, storage tanks, corrosion-resistant pumps and their accessories, corrosion-resistant valves, grilles, ventilation facilities, as well as sewage and wastewater treatment equipment and accessories.
3. Automobile and railway transportation industry: automobile shells and other components, all-plastic miniature cars, body shells of large passenger cars, doors, inner panels, main columns, floors, bottom beams, bumpers, instrument panels, small vans , as well as fire tankers, refrigerated trucks, tractor cabs and machine covers.
4. In terms of railway transportation, there are train window frames, roof curved panels, roof water tanks, toilet floors, luggage cart doors, roof ventilators, refrigerated doors, water storage tanks, and certain railway communication facilities.
5. In terms of road construction, there are traffic signs, isolation piers, sign posts, signs, highway guardrails, etc., boats and water transport industries.
6, inland passenger and cargo ships, fishing boats, hovercraft, all kinds of yachts, rowing boats, high-speed boats, lifeboats, transportation boats, as well as FRP buoys and mooring buoys and so on.
7. Electrical industry and communication engineering: arc extinguishing equipment, cable protection tube, generator stator coil and support ring and cone shell, insulating tube, insulating rod, motor guard ring, high voltage insulator, standard capacitor housing, motor cooling casing , generator windshield and other strong electrical equipment; distribution box and switchboard, insulation shaft, FRP cover and other electrical equipment; printed circuit boards, antennas, radomes and other electronic engineering applications.
With the development of science and technology and the improvement of people’s living standards, many civilian FRP products have been developed in large quantities, such as many urban sculptures, arts and crafts, fast dining tables and chairs, motorcycle parts, fiberglass pots, helmets, and advanced amusement equipment. , home appliance casings, etc., have been successfully applied in large quantities.
It can be made of FRP tile, also known as transparent tile. It is a lighting material used with steel structure. It is mainly composed of high-performance film, reinforced polyester and glass fiber. The film should be very resistant to UV and antistatic. The role of UV protection is to protect the polyester of FRP lighting panels from yellowing and premature light loss. Antistatic is to ensure that the dust on the surface is easily washed away by the rain or blown away by the wind to maintain a clean and beautiful surface. Due to its stable quality and durability, it is well received by customers and can be widely used in industrial/commercial/civil construction roofs and walls.
The film industry is used to make props, which is convenient and fast, and cost-effective. Can imitate a lot of material effects. Welcomed by people. The chemical plant also uses phenolic resin glass steel instead of stainless steel to make various corrosion-resistant equipment, which greatly extends the life of the equipment. FRP is non-magnetic and does not block the passage of electromagnetic waves. Using it to make a missile radome is like wearing a pair of protective glasses for the missile, which does not block the radar’s “line of sight” and protects it. The radomes of many missile and ground-based radar stations are made of FRP.
In the 21st century, according to the good wave-transparency of FRP, the performance of this aspect, with the widespread popularity of cell phone communication, FRP is widely used in the manufacture of 2G and 3G antenna covers, FRP with its good formability, appearance can be Beautification, played a very good role in the community beautification, this product has square column cover, simulation stone, field application of landscaping and other FRP also made a great contribution to improve the level of sports.
Since the sport of pole vaulting, the highest record ever created by athletes using wooden poles is 3.05 meters. Later, bamboo poles were used. By 1942, the record was raised to 4.77 meters. The advantage of bamboo raft is that it is light and flexible. The disadvantage is that the lower end is thick and the upper end is thin. It is very difficult to improve the record. Therefore, people use aluminum alloy enamel instead of bamboo raft. Although it is light and firm, it is not flexible enough. Thus, from 1942 to 1957, in fifteen years, the highest record of pole vault was only increased by 1 cm. However, since the emergence of the new FRP poles, due to its light and flexible, the record has risen rapidly, and today’s pole vault record has exceeded the 6-meter mark.
Today, FRP is also widely used in people’s lives. Because of its special varieties, it still retains many of the advantages of glass, such as transparency, so people use it as a window glass to block the ultraviolet rays in the sun. Can make the living room bright. It is also used to make a variety of durable everyday items. Such as baths, kitchen utensils, toiletries, etc.