silane coupling agent
It is a kind of organosilicon compound with two different chemical properties in molecule to improve the actual bonding strength between polymer and inorganic substance. This may refer not only to the improvement of real bonding strength, but also to the improvement of wettability, rheology and other operating properties. Coupling agents may also modify the interface region to enhance the boundary layer between organic and inorganic phases.
Therefore, silane coupling agents are widely used in adhesives, coatings and inks, rubber, casting, glass fibers, cables, textiles, plastics, fillers, surface treatment and other industries.
Its classical products can be expressed by general formula XSiR3.
In the formula, X is a non-hydrolyzable group, including alkenyl group (mainly Vi) and alkyl group with Cl, NH2 and other functional groups at the end, namely carbon functional group; R is a hydrolyzable group, including OMe, OEt and so on.
The functional groups in X are easy to react with the functional groups in organic polymers, such as OH, NH2, COOH and so on, thus linking silane to organic polymers. When the functional groups are hydrolyzed, Si-R is converted to Si-OH, and HR, such as MeOH, EtOH, etc. However, Si-OH can not only dehydrate with other Si-OH molecules or Si-OH on the surface of treated substrates to form Si-O-Si bonds, but also react with some oxides to form stable Si-O bonds, so that silane can be connected with inorganic substances or metals.


Common silane coupling agents are:
Sulfur-containing silane: bis-[3-(triethoxysilane)-propyl]-tetrasulfide, bis-[3-(triethoxysilane)-propyl]-disulfide
Aminosilane: gamma-aminopropyl triethoxysilane, N-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane
Vinyl silane: vinyl triethoxysilane, vinyl trimethoxysilane
Epoxysilane: 3-glycidyl ether oxypropyl trimethoxysilane
Methacryloxysilane: gamma-methacryloxypropyl trimethoxysilane, gamma-methacryloxypropyl triisopropoxysilane


Silane crosslinking agent
Silanes containing two or more silicon functional groups can bridge the linear molecules, thus enabling multiple linear molecules or mild branched-chain macromolecules and polymers to bond and cross-link into a three-dimensional network structure, promoting or mediating the formation of covalent or ionic bonds between polymer molecular chains.
Crosslinking agent is the core part of one-component room temperature vulcanized silicone rubber, which is the basis of determining the crosslinking mechanism and classification of products.
According to the different condensation products, one-component room temperature vulcanized silicone rubber can be divided into deacidification type, deketone oxime type, dealcoholization type, deamine type, deamidation type and deacetylation type. Among them, the first three kinds are general products produced on a large scale.
Taking methyl triacetyloxysilane as an example, the condensation reaction product is acetic acid, so it is called deacetic acid room temperature vulcanized silicone rubber.
Generally speaking, crosslinking agents are different from silane coupling agents, but there are some exceptions. For example, alpha series silane coupling agents represented by aniline methyl triethoxysilane have been widely used in one-component dealcoholic room temperature vulcanized silicone rubber.


Common silane crosslinkers are:
Dealcoholic silane: alkyl triethoxy, methyl trimethoxy
Deacidified silane: triacetyloxy, propyl triacetyloxy silane
Deketone oxime silane: vinyl tributyl ketone oxime silane, methyl tributyl ketone oxime silane