The use of silane coupling agent mainly includes surface pre-treatment method and direct addition method. The former is to treat the surface of the filler with diluted coupling agent, while the latter is to add the coupling agent solution directly into the resin and filler mixture.
Preparing a solution with silane coupling agent can promote its dispersion on the material surface. The solvent for the solution is prepared by mixing water and alcohol, and the solution generally consists of 20% silane, 72% alcohol, and 8% water. The alcohols used are typically ethanol (for ethoxy silane), methanol (for methoxy silane), and isopropanol (for silanes that are not easily soluble in ethanol or methanol). The hydrolysis rate of silane is related to pH value, and it is slower at neutral pH but faster at acidic or alkaline pH. Therefore, the pH value of the solution needs to be adjusted and a small amount of acetic acid can be added to adjust the pH value to 4-5, excluding amino silane which does not require adjustment. As silane hydrolyzes quickly and cannot be stored for long, the solution should be used within an hour of preparation.
Below are some specific applications for users' reference:
The filler is placed in a solid mixer and the above silane solution is sprayed directly onto the filler and stirred. The higher the stirring speed, the better the dispersion effect. Generally, the stirring time is 10-30 minutes (the slower the speed, the longer the time). After the filler treatment, it should be dried at 120°C for 2 hours.
The fiberglass surface treatment agent commonly contains film-forming agent, antistatic agent, surfactant, coupling agent, and water. The dosage of silane coupling agent is generally 0.3%-2% of the total amount of the fiberglass surface treatment agent. Firstly, adjust the pH value of the 5-fold water solution to a certain value with organic acid or salt. Then, add silane under sufficient stirring until it becomes transparent. Finally, add the remaining components. Isopropanol can be used to dissolve insoluble silane. During the drawing process, dry the fiberglass surface treatment agent on the fiberglass, remove the solvent and water.
A 5%-20% solution of silane coupling agent is prepared as described above, and the substrate surface is treated by coating, brushing, spraying, or impregnating. Let it dry at room temperature for 24 hours and bake at 120°C for 15 minutes.
Silane can also be directly added to the mixture of "filler/resin". When mixing the resin and filler, the silane can be directly sprayed into the mixture. The dosage of silane coupling agent is generally 0.1%-2% of the filler amount (determined by the diameter of the filler). Then, the resin/filler mixture with silane added can be molded (extruded, injected, coated, etc.).