The selection of organosilane coupling agents generally relies on summarizing the side test data of organosilane coupling agents, and accurately predicting organosilane coupling agents is very difficult. The increased bond strength after the use of organosilane coupling agents is a combination of a series of complex factors, such as wetting, surface energy, adsorption in the boundary layer, polar adsorption, acid-base interactions, etc.
The pre selection of organosilane coupling agents can follow the following rules: ethylene based, epoxy based, and methacryloxy organosilane coupling agents can be used for unsaturated polyethylene glycol; Epoxy resin should use epoxy based or amino based organosilane coupling agents; Phenolic resin should use amino or substituent based organosilane coupling agents; Ethylene based right-handed silane coupling agents should be selected for olefin polymers; Sulfur vulcanized rubber should use hydrophobic organic silane coupling agents, etc.
General principles for selecting silane coupling agents:
It is known that the hydrolysis rate of silane coupling agents is determined by the silicon group Si-X, while the reactivity with organic polymers is determined by the carbon functional group C-Y. Therefore, it is crucial to choose the appropriate silane coupling agent for different substrates or processing objects. The selection method is mainly through experimentation, pre selection, and should be based on existing experience or patterns. For example, in general, unsaturated polyesters often use silane coupling agents containing CH2=CMeCOOVi and CH2-CHOCH2O; epoxy resins often use silane coupling agents containing CH2CCHH2O and H2N; phenolic resins often use silane coupling agents containing H2N and H2NCONH; polyolefins often use vinyl silane; and rubber vulcanized with sulfur often uses alkyl silane, etc. Due to a series of factors affecting the bonding strength between dissimilar materials, such as wetting, surface energy, interfacial layer and polar adsorption, acid-base interactions, interpenetrating networks, and covalent bond reactions. Therefore, relying solely on experimental pre selection is sometimes not precise enough, and it is necessary to comprehensively consider the composition of the material and its sensitivity to silane coupling agent reactions. To improve hydrolysis stability and reduce modification costs, trialkylsilane can be added to silane coupling agents for use; For difficult to stick materials, polymers crosslinked with silane coupling agents can also be shared.
When silane coupling agents are used as thickening agents, they mainly form chemical and hydrogen bonds with polymers; Wetting and surface energy effects: achieved by improving polymer crystallinity, acid-base reactions, and the generation of interpenetrating polymer networks. The thickening mainly revolves around three systems: (1) inorganic materials on organic materials; (2) Inorganic materials to inorganic materials; (3) Organic materials to organic materials. For the first type of bonding, it is usually required to bond inorganic materials to polymers, so priority should be given to the reactivity between Y in silane coupling agents and the functional groups contained in polymers. The latter two types of bonding belong to the same type of materials, so silane coupling agents are chosen for their own anti hydrophilic polymers and inorganic materials that require increased adhesion.
