Silane coupling agent in the organic adhesive application and technology development

At present, the application of the adhesive has to soak in all areas of the national economy, on many occasions, the adhesive can effectively substitute for welding, riveting, and then Lo and other mechanical connection, in order to simplify the production line technology, energy conservation, reduce costs and improve Economic benefits provided an effective way. With the rapid development of science and technology, the performance of adhesive bonding technology and the ever-increasing demands. As a result of different materials have different properties Interface, in the bonding process in order to be sticky and adhesive material between the surface to obtain a solid adhesive layer interface, often with the use of reactive groups of the coupling agent with the sticky surface of solid - To achieve the formation of chemical bonds. The material can be used as a coupling agent class of organic silane, titanate ester, phosphate, as well as certain types of organic acids and so on, are found among the silane coupling agent of the most mature.
⒈ silane coupling agent in the role of organic adhesive
Silane coupling agent and at the same time is able to polar material and non-polar material must have a combined force of the compound, which is characterized by elements in both polar and non-polar part of the general formula that can be used for the Y (CH2) nSiX3, Y, said one of alkyl, phenyl and vinyl, epoxy, amino, organic thiol, and other functional groups, often with the adhesive resin matrix organic chemical combination of functional group; X, said chlorine-based, methoxy, ethoxy, and so on, These vulnerable groups into the hydrolysis of silicon and alcohol and inorganic material (glass, silica, metal, clay, etc.) or on the surface of the oxide-reaction, to form a stable silicon-oxygen bond. As a result, through the use of silane coupling agent, organic and inorganic substances in the interface between the material to build "bridges elements," the two very different nature of the material linked, so effective in improving the level of the interface bonding Intensity.
In the adhesive by adding silane coupling agent can not only improve the adhesive strength, but also to improve the durability of the adhesive and resistant to heat aging properties. For example, although many of the polyurethane material has a high bonding strength, but its durability is not ideal, silane coupling agent after its accession to the durability can be significantly improved. Chen Ruizhu such as titanium bonding pieces of research in the heat durability, through the epoxy adhesive used to add silane coupling agent, then pieces of plastic made in the heat after the aging of the post-shear strength retention rate from 80% to improve To about 97%. Silane coupling agent can even be used as adhesive for silicone rubber, fluorine rubber, nitrile rubber and metal bonding, adhesives, such as CK-1 and Chemlock 607 (United States) is that type of silane.
To improve the performance of some of the organic adhesive (such as heat resistance, self-extinguishing, dimensional stability, etc.), or to reduce the cost of organic adhesives, often in the adhesive to add a number of inorganic filler. If the use of silane coupling agent in advance of packing for processing, packing because on the surface of polar groups and silane coupling agent have taken place in response, thus greatly reducing the filler and resin structure of the role, not only for filling adhesive matrix Resin compatibility and greatly improve the dispersion and a significant reduction in the viscosity of the system, which would increase the amount of filler. However, not all the filler used to deal with agents are effective, different types of filling materials, there are differences in the effect on some of them even have no effect. The silica, glass, aluminum powder and the like with a large number of surface-Fill material is best for calcium carbonate, graphite, boron and so on the surface of the non-filling, there is no effect.
⒉ the use of silane coupling agent
⑴ surface pretreatment method to match silane coupling agent from 0.5 to 1% concentration of dilute solution, when used only in cleaning the sticky surface to be painted with a thin layer, can be dried on plastic. Solvents used for more water, alcohol, water or a mixture of alcohol and fluoride ions in water is not cheap and non-toxic ethanol, isopropanol is appropriate. In addition to the alkyl silane ammonia, the other by the silane coupling agent in the preparation of the solution required for accession to the acetic acid hydrolysis catalyst, and pH value of 3.5 to 5.5. Long-chain alkyl silane and stability due to the poor, the match should not be used in aqueous solution. Silane acetyl chloride and silane hydrolysis process, accompanied by a serious condensation and it is not proper match solution or alcohol solution of water use, and more than match the use of alcohol solution. Less water-soluble silane coupling agent, can join the 0.1 to 0.2 percent (mass) of non-ionic surfactant, coupled with water and then processed into the use of water emulsion.
⑵ migration law will silane coupling agent directly into the adhesive component, to join the general capacity of the matrix resin volume of 1 to 5%. After the glue to rely on the molecular diffusion, coupling agent who moved to the bonding interface coupling have a role. The need for curing the adhesive, glue, after a period of time required to place further solidified, so that the coupling agent to complete the relocation process, in order to obtain good results.
Actual use, often coupling agent on the surface to form a sedimentary layer, but the real work is only the single-molecule level, the amount of coupling agent do not have too many.
⒊ silane coupling agent of choice
Silane coupling agent in the performance of the two types of differences in the group to group Y of the most important, it decided to direct application of silane coupling agent. Only when the Y group to and the corresponding response from the matrix resin, in order to improve the organic adhesive bonding strength. General requirements Y group will resins and histocompatibility and from coupling reaction, so for different resins, to choose the appropriate Y-bearing group of silane coupling agent. When no response for the Y-alkyl or aryl, the polarity of the resin is a non-functional, but can be used for non-polar resins, such as silicone rubber, such as polystyrene plastic in the next. When the Y for the reactive functional groups, such as vinyl, epoxy, SH, and so on, must pay attention to it with the resin used in the response and histocompatibility. Amino-silane coupling agent belongs to the category of general-purpose, with almost all kinds of resin coupling effect, but with the exception of polyester resin. Adhesives used in the silane coupling agent (see Table 1).
4, silane coupling agent in their research on
At present, silane coupling agent commonly used for the three-alkoxy, but the three-alkoxy coupling agent may reduce the stability of the resin matrix, which in recent years, two alkoxy-coupling of research and application of attention . Silane activity with a synthetic polymer-based silane coupling agent is the development direction of one of this coupling agent on the adhesive resin has better compatibility, can be a sticky surface are a And thus have a better bonding effect. Silane in recent years have also started to look a coupling agent, which is characterized by fever in the role, the coupling agent to generate free radicals break down, can occur with the vinyl polymer cross-linked so as to promote, PCDF polymerization The bonding material.