When silane coupling agents are used as thickening agents, they mainly form chemical and hydrogen bonds with polymers; Wetting and surface energy effects; Titanium ester coupling agents improve polymer crystallinity, acid-base reactions, and the formation of interpenetrating polymer networks. The thickening mainly revolves around three systems: inorganic materials to organic materials; Inorganic materials to inorganic materials; Organic materials to organic materials. For the first type of bonding, it is usually required to bond the inorganic material to the polymer, so priority should be given to the reactivity between Y in the silane coupling agent and the functional groups contained in the polymer; The latter two belong to the adhesion between materials of the same type, so silane coupling agents are chosen for their anti hydrophilic polymers and inorganic materials that require increased adhesion.
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.
Pre selection of organosilane coupling agents can follow the following rules: ethylene based, epoxy based, and methacryloyl based organosilane coupling agents can be selected 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 be treated with hydrophobic organic silane coupling agents. If the minimum tax inclusive area of the organic silane coupling agent and the specific surface area of the filler are unclear, the substrate or filler should be treated with an organic alkyl coupling agent with a weight percentage of 1% of the filler, and then the concentration should be changed to obtain the appropriate amount through experimental methods. The dosage of organic brick alkane coupling agent is generally 0.1-2% of the weight of the treated substrate or filler.
Understand the instructions for using 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 experimental pre selection and should be based on existing experience or patterns. For example, in general, unsaturated polyesters often use silane coupling agents containing CH2=CMeCOO, Vi, and CH2-CHOCH2O -; Epoxy resins often use coupling agents containing CH2-CCH2O and H2N-silane; Phenolic resins often use coupling agents containing H2N - and H2NCONH - silane; Polyolefins often use vinylsilane; Rubber vulcanized with sulfur often uses alkyl silane and other materials. Due to a series of factors affecting the adhesion between heterogeneous 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 as titanium ester coupling agents; For difficult to stick materials, polymers crosslinked with silane coupling agents can also be shared.
As mentioned earlier, one of the main application areas of silane coupling agents is the treatment of inorganic fillers used in organic polymers. The latter can be treated with silane coupling agents to transform its hydrophilic surface into an organic friendly surface, which can avoid particle aggregation and rapid thickening of the polymer in the system, and improve the wettability of the organic polymer to the reinforcing filler. Carbon functional silane can also achieve strong bonding between the reinforcing filler and the polymer. However, the effectiveness of using silane coupling agents is also related to the type and dosage of silane coupling agents, the characteristics of the substrate, the properties of the resin or polymer, as well as the application scenarios, methods, and conditions. This section focuses on introducing two methods of using silane coupling agents, namely surface treatment method and overall blending method of titanium ester coupling agent. The previous method involves treating the substrate surface with a dilute solution of silane coupling agent; The latter method involves directly adding the original solution or solution of silane coupling agent into a mixture of polymer and filler, making it particularly suitable for material systems that require stirring and mixing.
