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What are the commonly used methods of using silane coupling agents?
Author:LongKom  Time:2018-4-18

1. Surface Pretreatment

The silane coupling agent is compounded into a dilute solution of 0.5-1% concentration. When used, only a thin layer of silane coupling agent is coated on the clean adhered surface. After drying, the silane coupling agent can be glued. Most of the solvents used are water, alcohol (methoxysilane chooses methanol, ethoxysilane chooses ethanol), or mixture of water and alcohol, and water without fluoride ion and cheap, non-toxic ethanol and isopropanol are suitable. In addition to aminoalkyl silane, acetic acid is added to the solution prepared by other silane coupling agents as hydrolysis catalyst, and the pH value is adjusted to 3.5-5.5. Long chain alkyl and phenylsilane are not suitable for use in aqueous solution because of their poor stability. Because silane can not last long after hydrolysis, it's better to use it now, and it's better to use it in an hour.


2、Direct addition
Silane coupling agent is directly added to the adhesive components, the general amount of addition is 1-5% of the amount of matrix resin. After coating, the coupling agent molecules migrate to the bonding interface to produce the coupling effect depending on the diffusion of molecules. For the adhesives that need to be cured, they need to be placed for a period of time before curing, so that the coupling agent can complete the migration process, in order to achieve better results. In practical use, the coupling agent often forms a deposit on the surface, but only the single molecule layer plays a real role, so the amount of coupling agent need not be too much.

Specific Use Method of Silane Coupling Agent


1. Pretreatment packing method

The filler is put into the solid mixer (HENSHEL or V-type solid mixer of high-speed solid mixer) and the silane solution is sprayed directly on the filler and stirred. The higher the rotational speed, the better the dispersion effect. Generally stirring in 10 - 30 minutes (the slower the speed, the longer the time), filler treatment should be 120 degrees Celsius drying (2 hours).


2. Aqueous Solution of Silane Coupling Agent

(Glass fiber surface treatment agent): Glass fiber surface treatment agent often contains: film forming agent, antistatic agent, surfactant, coupling agent, water. The amount of coupling agent is generally 0.3%-2% of the total amount of glass fiber surface treatment agent. Five times of water solution is first adjusted to a certain PH value by organic acid or salt. Under full stirring, silane is added until transparent, and then other components are added. For insoluble silane, isopropanol can be used as solubilizer. In the process of drawing, the glass fiber surface treatment agent is sprayed on the glass fiber to dry, and the solvent and water can be removed.


3. Bottom Surface Method

With the solution of 5%-20% silane coupling agent as mentioned above, the substrate surface was dipped by coating, brushing and spraying, and then dried at room temperature for 24 hours, preferably baked at 120 C for 15 minutes.


4. Direct addition method
Silane can also be directly added to the mixture of filler and resin. When the resin and filler are mixed, silane can be directly sprayed into the mixture. The dosage of coupling agent is generally 0.1%-2% of the dosage of filler (depending on the diameter and size of filler). Then the resin and filler added with silane are moulded (extrusion, compression, coating, etc.).

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