A coupling agent is a molecule with two active groups at both ends, which can react with two incompatible substances. To improve the compatibility between the two substances and enhance their binding ability. For example, the silane series from Yingchuang has one end being a silicon methoxy group that can react with hydroxyl groups on the surface of silicon powder, and the other end being an epoxy group that can react with epoxy curing agents. This can improve the bonding between silicon powder and epoxy resin. Thereby improving the strength of the epoxy adhesive.
Surfactants have two types of functional groups at both ends, one being hydrophilic and the other being lipophilic. This can reduce the interfacial energy between two incompatible liquids.
From the above, it can be seen that the two most important functional groups of coupling agents are reactive groups, while surfactants do not have chemical reactions.
The definitions of the two substances are as follows for reference.
Surfactant refers to a substance that can cause a significant change in the interfacial state of its solution system when added in small amounts. Having fixed hydrophilic and oleophilic groups, they can be oriented and arranged on the surface of the solution. The molecular structure of surfactants has amphiphilicity: one end is a hydrophilic group and the other end is a hydrophobic group; Hydrophilic groups are often polar groups, such as carboxylic acids, sulfonic acids, sulfuric acids, amino or amino groups and their salts. Hydroxyl groups, acyl groups, ether bonds, etc. can also be polar hydrophilic groups; And hydrophobic groups are often non-polar hydrocarbon chains, such as hydrocarbon chains with more than 8 carbon atoms. Surfactants are divided into ionic surfactants (including cationic and anionic surfactants), non-ionic surfactants, amphoteric surfactants, composite surfactants, and other surfactants.
Coupling agents are a type of substance with two different functional groups, and the biggest characteristic of their molecular structure is the presence of two groups with different chemical properties in the molecule. One is a hydrophilic group that is prone to chemical reactions with the surface of inorganic substances; The other is an organic group that can react chemically or form hydrogen bonds with synthetic resins or other polymers and dissolve in them. Therefore, coupling agents are called "molecular bridges" to improve the interfacial interaction between inorganic and organic materials, thereby greatly enhancing the properties of composite materials, such as physical, electrical, thermal, and optical properties. Coupling agents used in the rubber industry can improve the wear resistance and aging resistance of products such as tires, rubber sheets, rubber hoses, and rubber shoes, and reduce the amount of NR used, thereby lowering costs. The role of coupling agents in composite materials is that they can react with certain functional groups on the surface of the reinforcing material, as well as with the matrix resin, forming an interface layer between the reinforcing material and the resin matrix. The interface layer can transmit stress, thereby enhancing the bonding strength between the reinforcing material and the resin, improving the performance of the composite material, and preventing other media from penetrating the interface, improving the interface state, and promoting the aging resistance, stress resistance, and electrical insulation performance of the product.
