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Introduction to the research trend of coupling agents & application fields and uses of coupling agents
Author:LongKom  Time:2017-12-21

The synthesis of polymer with active silyl alkyl is also one of the development directions of silane coupling agent. The Guangzhou titanate coupling agent has better compatibility with the resin in the adhesives, and can form a uniform surface on the surface of the adhesives, so it has better bonding effect. An important new application of silane coupling agent is to produce water-crosslinked polyethylene. This process was developed by Dow Corning Company of the United States and has been commercialized. In recent years, in the experiment of using organosilicon emulsion to treat wool fabrics, it was found that silane coupling agent and silicone emulsion can be used to improve the wearability of woolen fabrics.


At present, the commonly used silane coupling agent is trialkoxy type, but trialkoxy type coupling agent may reduce the stability of matrix resin, so the research and application of dialkyloxy type coupling agent has been paid attention in recent years.


Peroxysilane is also a kind of coupling agent which has been studied in recent years. Its characteristic is that under the action of heat, the coupling agent decomposes into free radicals, which can cross-link with olefin polymers, thus promoting the bonding of olefin polymers.


Application fields and uses of coupling agents
Fiberglass and FRP: Improve the wet physical and mechanical strength, wet electrical properties of composites, and improve the clustering, protection and processing technology of fiberglass.
Adhesives and coatings: improve the adhesion and weatherability under wet conditions, improve the dispersibility of pigments, improve the wear resistance and cross-linking of resins.
Casting: Improve the strength of resin sand. In order to achieve high, low gas.
Rubber: Improve the mechanical strength, wear resistance, wet electrical properties and rheology of products.
Sealant: Improve the wet adhesion, improve the dispersion of fillers, product wear resistance.
Textiles: Make textiles soft and full, improve their waterproof, and adhesion to dyes.
Printing ink: Improve the wettability of adhesion.
Surface treatment of filler: improve the compatibility, wettability and dispersion of filler and resin in resin.

Crosslinked polyethylene (XLPE): Used to enhance the strength of XLPE cables and hot water pipes. Durability and service life.


Main uses
In reinforced plastics, chemicals that improve the interfacial bonding between resins and materials.
At the interface between resin matrix and reinforcement material, Guangzhou titanate coupling agent promotes or establishes stronger binding material.
Note: Coupling agent can be applied to reinforcing materials or added to resins, or both.
Understanding the instructions for the use of silane coupling agents
I. General Principles for Selecting Silane Coupling Agents

It is known that the hydrolysis rate of silane coupling agent is determined by the silicon group Si-X, while the reactivity with organic polymer is determined by the carbon functional group C-Y. Therefore, it is very important to select suitable silane coupling agents for different substrates or treatment objects. The method of selection is mainly through pre-selection by experiment, and should be based on existing experience or rules. For example, in general, unsaturated polyesters use silane coupling agents containing CH2=CMeCOO, Vi and CH2-CHOCH_2-; epoxy resins mostly use coupling agents containing CH2-CHCH_2O and H_2N-silane; phenolic resins mostly use coupling agents containing H_2N-and H_2NCONH-silane; polyolefins mostly use vinyl silane; rubber vulcanized with sulfur yellow mostly uses alkyl silane and so on. The bonding degree of heterogeneous materials is affected by a series of factors, such as wettability, surface energy, interface layer and polar adsorption, acid-base interaction, interpenetrating network and covalent bond reaction. Therefore, it is not precise to select the material only by experiment, and the composition of the material and its sensitivity to silane coupling agent should be considered comprehensively. In order to improve the hydrolysis stability and reduce the cost of modification, silane coupling agent can be mixed with trialkyl silane, and for refractory materials, silane coupling agent can be used as a cross-linking polymer.


When silane coupling agents are used as tackifiers, they are mainly realized by forming chemical bonds and hydrogen bonds with polymers, wetting and surface energy effects, improving the crystallinity of polymers, acid-base reactions and the formation of interpenetrating polymer networks. Viscosity enhancement mainly revolves around three systems: (1) inorganic material to organic material; (2) inorganic material to inorganic material; (3) organic material to organic material. For the first kind of bonding, inorganic materials are usually required to be bonded to polymers, so the reactivity of Y in silane coupling agent with functional groups in polymers should be given priority; the latter two belong to the bonding between the same types of materials, so the anti-hydrophilic polymer of silane coupling agent itself and the silane coupling agent selected when inorganic materials require tackifying.


二、Usage method
As mentioned above, one of the main applications of silane coupling agents is to treat inorganic fillers used in organic polymers. The latter can transform its hydrophilic surface into a hydrophilic organic surface by silane coupling agent, which can not only avoid the aggregation of particles and the rapid thickening of polymers in the system, but also improve the wettability of organic polymers to reinforcing fillers. Carbon functional silane can also make reinforcing fillers bond firmly with polymers. However, the use effect of silane coupling agent is also related to the type and dosage of silane coupling agent, the characteristics of substrate, the properties of resin or polymer, and the application occasion, methods and conditions. This section focuses on two methods of using silane coupling agent, i. e. surface treatment method and whole blending method. The former is to treat the surface of the matrix with dilute solution of silane coupling agent, while the latter is to add the original solution or solution of silane coupling agent directly into the mixture of polymer and filler, so it is especially suitable for mixing in need of stirring.

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