Epoxy adhesive is widely used in electrical/electronic industry because of its versatility, excellent adhesion, wide adaptability, convenient use, good electrical performance and aging resistance. Silicone adhesive is suitable for flexible, wide temperature, high frequency, high temperature and air pollution bonding. Hot melt adhesive can be used under the conditions of high assembly speed, low strength and low working temperature. Acrylate adhesives are chosen mainly because they have excellent electrical properties, stability, good aging resistance and transparency, and can be cured quickly. Polyurethane adhesive keeps soft, tough and firm from low temperature to 12 1℃. Pre-coated polyvinyl butyral can form tough and easy-to-assemble joints. The main applications of adhesives in microelectronics are:
(1) die bonding;
(2) bonding the circuit elements to the substrate;
③ packaging;
④ Printed circuit board.
Because it must withstand the welding temperature of 250℃, the application of adhesive in bonding steel foil and laminated printed circuit board is limited. Adhesives are also used for large-scale equipment, such as generators, transformers and other equipment operating at high temperature, and equipment that must operate in harsh environment and high shrinkage for 20~40 years. The size of many devices excludes the possibility of oven curing. The heat conduction of copper and other metals makes local heating impossible. Therefore, room temperature curing adhesives must be used.
Whether printed circuit board is rigid or flexible, it is inseparable from adhesive. For epoxy glass plate, acetal phenolic aldehyde, nitrile phenolic aldehyde or modified epoxy can be used, and the most suitable temperature is about 1500℃. When used at high temperature of 260℃, glass, silicone laminate or copper-PTFE composite plate should be used. Laminated components of rigid printed circuit boards can be bonded together with plastic films coated with thermoplastic or thermosetting adhesives. Sometimes complex components require thin/flexible printed circuits. At this time, RTV silicone rubber coating can not only be used as insulation coating, but also reduce vibration, because this vibration will increase the unwanted fatigue load of welded joints. In addition, the stressed parts are coated with epoxy glue and organic chain glue to reduce impact and vibration. At present, packaging materials are developing in the direction of beauty, portability, durability and ensuring the quality of contents, and production is developing in the direction of automation, mechanization and rapidity. Therefore, the adhesives must meet the above requirements: starch and modified starch adhesives are used in the production of corrugated cardboard, paper bags, cartons, paper tubes and paper cups, and polyvinyl acetate homopolymers or * * * poly adhesives and hot melt adhesives are used in high-quality cardboard and paper containers. Because the latter is waterproof, it can withstand the erosion of condensed water in the air taken out of the freezer and the changeable environment of long-distance transportation or even crossing the ocean. The bottom of the polyester bottle and the beverage can can be bonded with adhesive.
With the improvement of people's living standards, quick freezing and fast food came into being. Its packaging materials are mostly plastic or aluminum films with multi-layer structure formed by adhesive, which can withstand the sudden temperature change from refrigerator to microwave oven and is convenient to use. This composite film packaging material can also be used to package medicine, electronic components and chemical raw materials.
Bonding technology can also make the production of cigarettes, bottle labels and book covers develop at a high speed, and their productivity is 8000 cigarettes per minute, 1300 bottles and 100 copies respectively.
The surface of precision machined parts can be protected by pressure-sensitive adhesive tape or peelable pressure-sensitive adhesive to avoid damage or damage during handling. The extensive use of pressure-sensitive adhesive tape in packaging industry has greatly reduced the labor intensity of workers and improved the labor productivity.
The application of adhesive in packaging industry includes: ① manufacturing corrugated boxes, sticking corrugated boards on the surface, sealing and making boxes; ② Folding box; ③ Stratification; ④ Pipe winding (spiral and spiral winding) ⑤ Assembly box; 6 bags; ⑦ Label.
Polyvinyl acetate and polyvinyl alcohol are important components in the production of corrugated box adhesives. Starch glue is used for pasting corrugated board and sealing boxes; Polyurethane adhesive is used for compounding ester film, aluminum foil and polyethylene film. Hot sol is used in various food packaging, such as paper boxes, paper cans, paper bags, paper cups and laminated metal foils. Adhesives are widely used in manned and unmanned spacecraft. Use adhesives to make parts, assemblies or fix parts on spacecraft. The following are some representative applications:
(1) refrigeration plate (to keep the working temperature of electronic components)
② container;
③ detector;
④ cover plate;
⑤ Loading capacity and spare parts;
⑥ Thermal shielding (for reentry);
⑦ Shock/vibration damper;
8. Launcher components (rocket engine, engine, nozzle, nozzle extension, shielding plate and insulating material);
Pet-name ruby fixed plate supporting equipment;
Attending multilayer circuit board;
(1 1) electronic components and components;
(12) workbench (positive and negative rotation;
(13) Main components (adding struts, reading cylindrical components, conical components, frames, etc. );
(14) radiator (for temperature control);
(15) reflector (used for temperature control;
(16) sensor;
(17) solar cells;
(18) thermal insulation material;
(19) Wiring (configuration, connection and fixation). Synthetic adhesives have been used on airplanes for decades. Its application has greatly changed the structure of aircraft, and it can produce aircraft with high strength, light structure, good fatigue, long life, reliability and high efficiency. For example, the aircraft structural material is mainly aluminum alloy, and the shear strength is 3.9~7.8MPa when riveted. It's just 16. 7~34.3MPa is used for bonding fans, which is 2~4 times of the former.
Aircraft manufacturing industry is the earliest industry to study and apply metal structural adhesive, and it is also the main user of structural adhesive. Each aircraft needs about 400~2200gk of adhesive, which is mainly used for bonding aircraft skin with frame or truss, assembling and bonding honeycomb components, helicopter propeller blades and interior parts. For example, bonding 1 Boeing 747 aircraft consumes about 3700m2 of adhesive film, 43 1kg of polysulfide sealant and 234kg of silicone rubber sealant. Except supersonic aircraft, the application of adhesives is limited by the high temperature of skin. With the improvement of materials and technology, the demand for adhesives in aircraft manufacturing is increasing and will continue to grow. Most of them use high-performance structural adhesives such as phenolic-nitrile, phenolic-epoxy, epoxy-nitrile and so on. In recent years, there is still a demand for flame retardant structural adhesives, and most of them are jumping.
Machinists led by the aviation industry have become the main driving force to promote the development of modern adhesives, and the number of single-machine adhesives often marks the level of aircraft manufacturing technology in a country. The successful application of adhesives can promote advanced heat-resistant and high-strength composite materials, such as carbon fiber and boron fiber, which may be used in aviation industry and further improve aircraft structure.
Sealants are also widely used in aircraft manufacturing, especially polysulfide sealing materials for sealing oil tanks. Other applications are pressure-free bonding of the edges of rectifying devices and sealing honeycomb sandwich plates. Where heat resistance is required, such as nozzle seal near exhaust pipe, silicone sealants should be used. Each 8-58 rogue bomber has about 420m2 of bonded wallboard, and its structure includes components bonded with high peeling strength and high temperature resistance nitrile-based phenolic resin and aluminum skin honeycomb bonded with epoxy-nitrile base. Both aluminum and glass fiber reinforced plastic honeycomb sandwich structures can be used, and the shape changes from flat plate to sharp turning front edge.
The appearance of two-phase NBR- phenolic/epoxy film and the use of nylon-epoxy and NBR- epoxy adhesives are helpful to overcome some shortcomings of NBR- phenolic film, so that the edge and skin can be bonded to the honeycomb structure with a single adhesive. Other applications of aircraft bonding include glass fiber laminates and core components, and epoxy-phenolic paste adhesive is usually used because it can foam, fill holes and have a large contact area with the edge of honeycomb sandwich structure. Civil jet aircraft uses adhesive to bond horizontal and vertical wing plates, brush wings, conical tail assembly and nose radome. In the construction industry, adhesives are mainly used for structure and decoration, making many building components, such as cork plywood, laminated wood boards, laminated cardboard and some similar components, plastic floors, carpets, tiles, wallpaper and so on. In recent years, adhesives have been used to replace mechanical steel bars in the installation and construction of building projects. This kind of adhesive is called structural adhesive. For joints with poor coordination, a thick adhesive layer or a thin adhesive layer can be firmly adhered. At present, there are two main problems in bonding in construction industry: one is the lack of proper temperature control during bonding; Second, there is no suitable process equipment and mechanical reinforcement is needed. Applications of adhesive components in the construction industry include:
(1) Bonding the integral lining wall with the wooden frame;
(2) The floor and ceiling with lining board are bonded with longitudinal beams and rafters to play the role of T-beams;
(3) Sandwich plates with various surfaces stressed;
④ Assembly of glued wooden frame;
⑤ Box beams used as longitudinal beams or rafters and other types of woven beams;
⑥ Glue all parts into the final structural member. Adhesives are used in automobile industry (including automobiles, trucks, motorcycles and related means of transportation) for the sake of simple process, reliable performance, economy and high efficiency; Used for structural connection, fixing and sealing of metal, plastic, fabric, glass, rubber, etc. Themselves or each other and paint the surface. There are about 25 kinds of adhesives suitable for automobile assembly, and the amount of adhesives used in a typical automobile is about 9 to 8 kinds. Automobile adhesive must meet some unique requirements, which have nothing to do with the performance of adhesive joints, and must be easy to use under the following conditions: ① basically unskilled workers, often replaced frequently; ② The productivity is high (100 vehicles /h), and each operation is a short fixed time; ③ The bonding surface only needs minimal cleaning (there may be oil stain); ④ The allowable limit of health and safety standards is low; ⑤ The curing time, pressure and temperature can be changed slightly, which should match the baking process or the low thermal deformation temperature of the material; ⑥ Want to avoid accurate weighing and complicated mixing. The automobile industry has very strict requirements for adhesives. Modern cars must be able to run well in the temperature range of -40~93℃, and also be resistant to temperature change, salt water, fuel oil, grease, high temperature, vibration, washing and dust. The structural applications of adhesives in automobile industry are as follows: ① body and roof reinforcement plates; ② Top plate of double-layer shell; ③ the inner and outer panels of the car cover; ④ Brake shoe ⑤ Clutch and transmission belt; ⑥ window sealing; ⑦ Plastic baffle; ⑧ Disc brake friction plate; Pet-name ruby glass fiber reinforced plastic (FPR) body panel (sports cars and trucks, attending radiator water tank; 1 1 plastic floor.
Brake friction lining must be able to withstand the impact and shear stress at high temperature above 149℃, and NBR-phenolic film can be used. Disc brake pads must be able to withstand the high temperature above 177℃, and phenolic resin is needed. Other uses of structural adhesives in automobiles are bonding glass and metal. It turned out that the windshield and rear window were sealed with butyl rubber tape and mechanically fixed. Or simultaneously sealing and fixing by using cross-linked polysulfide materials. Since the early 1970s, polyurethane adhesive has replaced polysulfide to install windshield and rear window.
Polyvinyl butyral adhesive is used to bond rearview mirror and windshield. This glue is called positioning glue. The main function of positioning glue is to connect one material with another without transmitting large structural load. According to the application of positioning glue in the interior or exterior of the seat compartment, it can be divided into internal positioning glue or external positioning glue. Internal positioning glue can be used for: ① decorative lining board; 2 door panels; ③ Carpet; (4) sealing the wind-proof adhesive tape; ⑤ Silencing liner; ⑥ Body side panel molding; ⑦ Wood grain decoration; 8 8 ⑧PVC ceiling; Pet-name ruby locks.
One of the most widely used adhesives in automobile industry is chloroprene solvent-based adhesive, which is used to bond PVC ceilings, and now it tends to be pressure sensitive adhesive.
The main function of sealing adhesives (sealants and gaskets) used in automobiles and trucks is to isolate air, dust and water to reduce corrosion or improve comfort. In many cases, they also serve as positioning adhesives. Many applications on modern automobile bodies are invisible. In fact, it is better to use low viscosity rubber sealant for the connection between all metal employees and metal car bodies than spot welding. Polyethylene hot melt adhesive can be used for parts that are difficult to solve after assembly. Usually, polyethylene sealant is used to replace the welding of the front body joint, and then the joint is covered, which can not bear large bending, expansion and contraction. This sealant has good adhesion, enough viscosity to prevent sagging and good weather resistance. They must be exposed to severe salt spray and repeated freeze-thaw cycles. Epoxy sealant is replacing the traditional lead solder to weld the car body. In order to give full play to the role of wood resources and improve their utilization rate, adhesives are added to wood, shavings and branches, which can be pressed into plywood, particleboard and fiberboard, commonly known as man-made board. 1M plywood can replace 3M logs, so it is particularly important to develop wood-based panel industry in countries with scarce forest resources. Accordingly, attention should be paid to the development of adhesives for wood processing. Wood processing industry is the department with the largest consumption of adhesives. The United States accounts for about 40% of the total amount of synthetic adhesives, Japan accounts for 9%, the former Soviet Union accounts for 70% ~ 80%, and China accounts for 34% ~ 36%. It mainly includes phenolic resin, urea-formaldehyde resin and melamine-formaldehyde resin adhesive, mainly urea-formaldehyde resin adhesive (mainly phenolic resin in the United States).
In the production of furniture and wood-based panels, polyvinyl acetate emulsion and hot melt adhesive are widely used. In addition to high-quality polyvinyl acetate emulsion, adhesives such as neoprene are also used for decorative veneers and composite boards.
Since 1970s, the advent of waterborne polyurethane has provided a room temperature curing adhesive for wood processing industry, which contains no free aldehyde and can be used for sizing high moisture content wood. Its product has high strength and good water resistance. Although the price is three times that of urea-formaldehyde resin, its dosage is small, so it is a promising adhesive. ① Pressure-sensitive adhesive tape (packaging tape, transparent tape, masking tape, reinforced packaging tape, electrical tape, medical tape)
② Adhesive tape (used for stamps and shipping labels).
(3) Paste and glue (for offices, schools and libraries).
(4) Crafts (epoxy glue, cyanoacrylate glue, white latex, butyric acid glue, urea-formaldehyde glue).
(5) wallpaper pasting.
⑥ Optical element (bonded lens element).
⑦ Weapons.