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Hyundai Motor on the adhesive sealing technology-HongYe silicone

Writer:TcoglorSource:www.szrl.net Date:2013-04-23

Definition and function of a sealing / adhesive
Sealants for the automotive industry in general should have a higher long-term durable adhesion, and therefore sometimes referred to as adhesive and (or) structural adhesives. Some people think that such a bonding and sealing the plastic of the dual function can be called "the sealant / adhesive.
Bonding technique is to stick to a solid surface with the adhesive bonding force, the same kind or different kinds of materials are firmly connected together. Bonding of two forms: non-structural and structural-type. The non-structural bonding mainly refers to the sticky surface coating, sealing, bonding and functionality, typical non-structural adhesive surface bonding adhesive, sealing and conductive adhesive; structural bonding is the structural unit with adhesive firmly fixed on the bond phenomenon. Which structural adhesive bonding point must be able to pass the structural stress, does not affect its structural integrity and the suitability of the environment in the design range.
The main function of the glue bonding material linked. Bond component of the stress transfer compared with traditional mechanical fastening, stress distribution is more uniform high strength bond component structure than mechanical fastening (riveting, welding, interference connection and bolted, etc.) low cost, light weight. If the thin-walled parts bonding material stick received a thick-walled products can take advantage of all the strength of thin-walled parts. Mechanical fastening and welding strength of the structure subject to the restrictions of the fasteners or solder its thermal sensing area.
Smooth appearance of the component adhesive bonding features did not decline. This is particularly important structural type bond. Such as the aerospace industry in the structure of the appearance of smooth and high, so to reduce drag and friction reduced to the friction heat up to a minimum. Therefore, the helicopter rotor blades are assembled with glue. Adhesive bonding closely with electronic or electrical components to avoid the bump point benefit from the rich. Navigation electrical use adhesive assembly without the interference of available flat outer surface. Improve due to the bond joint stress distribution is very uniform, allows to be bond strength and stiffness of the objects all be reflected, but also reduce the quality, eliminate the negative load to the spacecraft using the adhesive assembly, increases the payload, flight , to reduce shipping costs.
The adhesive can be used for the bonding between the metal, plastic, rubber, ceramic, cork, glass, wood, paper, fiber and other various materials. Joints of different materials in a variable temperature, the adhesive can play its unique use of performance. The flexible plastic can adjust the difference between the thermal expansion characteristics of the bonding material and the rigid solid system to prevent damage in the environment. If the bond component is used at higher temperatures, flexible adhesive suitable to move and migration between different materials, can effectively adjust the thermal expansion differences between the different quality of materials through the movement or migration process to achieve a solid bond into one purpose. Therefore the car windows with metal frame bonding commonly used adhesive to complete.
Seal is actually a continuous bond. This bonding method is easy to seal bonding connectors. Prevent the damaging effects of liquids and gases to penetrate. The adhesive can replace a solid body or foam gasket seal for the gear box housings, valve cover, car parts. Because of its multi-use in a liquid state, can be used for potting, sealing potting such as circuit boards, motors, electrical and electronic components commonly used. Products or parts breakage or cracks is a common phenomenon, the conventional method of repair is the use of welding, welding, however often make the repair items thermal deformation stress, especially in thin-walled parts should not be using this welding method. If it is difficult to weld materials or explosion-prone situations (such as oil tank, etc.) more difficult to repair welding method, the only safe and reliable method for adhesive bonding.
Casting defects (porosity, pore blocking) has been a recurrent problem of the foundry industry, the repair methods used with defective parts need skilled workers to consume large amounts of materials and time to fix it, otherwise they become waste. Dedicated to fill the glue to repair effort and money and parts wear and the size of ultra-poor or scratch phenomenon accounting for more than 70% of the mechanical parts failure rate. The traditional approach is the use of the surfacing, thermal spraying, plating, brush and so on. Make the parts for welding or thermal spraying the surface reached a high temperature, causing parts to deformation or formation of microscopic cracks. Affect parts of the dimensional accuracy and normal use. Plating and electrical plating, although there is no heat, but the thickness of the coating requirements of the strict application is restricted to the adhesive surface-coated with a technical fix is ​​simple, neither thermal effects are not subject to the limitations of coating thickness, and to ensure wear resistance of parts.
"Drop, take, seepage, leakage" is a recurring phenomenon in the car. The use of adhesive surface-coated plugging a very safe and convenient, saving time, reliable quality, sometimes does not affect the running, the ambient pressure to repair the leaking part, to achieve the purpose of re-sealed, especially in the flammable, easy to explosion occasions the car maintenance and parking of Pressure Seal demonstrated its unique advantages.
The sealant material used to fill voids (holes, joints, seams, etc.). Amorphous sealant is the main body of the sealing materials, types of silicone (including modified silicone) class, polyurethane, polysulfide rubber, acrylic, SBR rubber, butyl rubber, asphalt, oily caulking plastic, etc., the first sealant asphalt, oil and caulking compounds. Used to fill shall be subjected to vibration or heating or cooling due to scalability gap, you must adopt a flexible sealant. Over the years, a flexible sealant been widely applied in many industries such as construction, civil engineering, automotive, shipbuilding, electrical communication, civilian areas, including building the demand for sealants. Flexible sealant will bond and seal the product of two functions rolled into one. Which the better performance of the three types of high-grade elastic sealants are silicone sealants, polysulfide sealants and polyurethane sealants.
Polyurethane sealants in automotive applications: window (mainly assembly sealing the windshield), body and other parts of the assembly. Polyurethane sealant for caulking seal flexible in the joints of high-grade roads, bridges, runways, and concrete, ceramic, PVC and other materials, sewer, underground gas pipes, wires and circuit piping and other piping joints in civil at the connection seal, subway tunnels and other underground tunnel junctions seal.
2 seal / physical properties of the adhesive
(1) sealant rheology. Commonly used sealants usually have two categories, namely non-contact with the degeneration of the self-leveling and thixotropy collapse. The former applied after leveling; while the latter is sometimes similar pastes can not flow, can be used for vertical surfaces and other parts.
(2) the use of temperature and pressure range. The sealant should have a wide temperature and pressure range. Compression depends largely on the strength of sealant and joint design. The silicone rubber can be made of the best high-temperature sealant, it can be used at 205 ℃ for a long time, short-term use temperature up to 260 ° C, fluorosilicone rubber in 260 ℃ under continuous use. Dichromate-type manganese dioxide curing polysulfide sealant can withstand the high temperature of 107 ℃; copolymer acrylic can withstand 175 ° C, acrylic latex class resistant to 73 ° C only.
(3) compatibility and permeability. Can match the ability of any chemical reagent corrosion sealant. Sealant due to other conditions, and thus with a sealant should take into account all its aspects. For example, some sealants can absorb a small amount of moisture, causing the sealant aging resistance and chemical resistance to change; Yet another one-component sealant requires to absorb moisture in order to cross-linking curing. A sealant for moisture transmittance value depends on the choice of polymers, fillers, plasticizers in the formula.
(4) weather resistance. Outdoor working conditions, sealants based on the use of different occasions, with varying degrees of water resistance, heat, cold, UV and sunlight irradiation performance. For example, in the oceans and seas must be resistant to salt spray, polysulfide sealant is sensitive to heat, while the polyurethane is water sensitive, Silastic both water resistance and heat resistance.
(5) mechanical properties. The sealant's mechanical properties including strength, elongation, compression, modulus of elasticity, tear and fatigue resistance, etc.. In many of the mechanical properties of sealant, the modulus is a very important mechanical properties. The use of sealants, especially in the seams sealed and in need of damping shock parts of the seal, generally require a lower modulus. Such as the inner layer of butyl sealant used for bonding and sealing of insulating glass components and the outer layer of curing type sealant, have a lower modulus, in order to absorb the stress generated due to various reasons in the hollow glass broken glass to avoid stress concentration. Wear and mechanical abrasion on sealant, flexible sealant, polyurethane, neoprene have good abrasion resistance.
(6) bond. The main factors affect the bonding interaction between the sealant and sticky surface, sticky surface shape, smoothness, and the bottom plastic. Typically, the sealant can not afford a strong external stress, modulus of the sealant varies with humidity. When the sealant for a dynamic seal the seams in the bottom of the seams should be added to anti-adhesive protective layer to prevent bonding and to avoid too much stress.
3 the construction of the sealing / adhesive characteristics
(1) sealant curing characteristics. The curing characteristics, including curing time, temperature, and temperature control. Most of the sulfide weak sealant cure time is longer. Will shorten the shelf life of sealant cure time, production efficiency; but the curing time is too short, single-hardening sealant, two-component two. Single-component sealant and some water (wet) gas as a catalyst (such as polysulfide, polyurethane), cross-linked by chemical changes in moisture exists. Some sealants need to be heated to accelerate curing.
(2) sealant operating characteristics. Operating performance, including in the form of sealant, viscosity, and the necessary pre-processing. Two-component sealant mixed simple, and can be manual or automated equipment construction. Sealants are generally a period of use can make the adjustment formula, the sealant activity in line with operational requirements. Viscosity of the sealant on the use of technology, high viscosity sealant is difficult construction, by adjusting the formula (such as by adding a solvent or diluent) to adjust its viscosity, to improve its usability, the construction of the seal on a vertical surface The glue can not collapse, the viscosity slightly higher.
(3) construction method. Most of the sealants are liquid, paste paste or putty-like supply, construction methods: brushing or roller, putty knife, scraper, scratch, and caulking the extrusion gun. Brush, scrape, squeeze method requires the operator to have a certain operating techniques.
(4) the surface of the seal base material. The general surface of the base material just dust grease and moisture can be. Critical parts, especially the place to be sealed again and bonding on the surface of the base material handling higher. Some sealants require the use of the bottom adhesive.
(5) maintenance performance. Sealant during normal use, requiring a repair sealant materials. Some sealant, especially non-hardening sealant is easy to remove and can be reused. However, some sealant, especially some of the plastic or elastomer base material, once destroyed it is difficult to repair.

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Keywords for the information:Silicone  Silicone rubber  silicon 

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