1. How to choose a silane coupling agent?
There are dozens of silane coupling agents, such as amino groups, chlorine groups, alkenyl groups, epoxy groups, methacryloyloxy groups, mercapto hydrocarbon groups, cationic groups, and bifunctional groups, which are highly targeted from the application point of view. , it is crucial to choose a suitable silane coupling agent.
The selection method is mainly pre-selection through tests, and should be based on the structure and properties of the silane coupling agent and the mechanism of interaction with the silicon powder. At the same time, it is also necessary to comprehensively consider the composition of the downstream product base material and the effect of the reaction on the silane coupling agent.
In addition, if more than two coupling agents are selected, the question of which coupling agent should be added first or later should be carefully considered.

2. How to determine the dosage of silane coupling agent?
The amount of silane coupling agent is determined according to the number of reactive points (such as Si-OH) occupied by the specific surface area of the powder and the thickness of the monomolecular layer and multi-molecular layer that the silane coupling agent covers on the surface.
Generally, the Si-OH content of silicon micropowder mineral powder is 4-12 μm2, and 1 mol of silane coupling agent can cover the powder surface area of about 7500m2. After the silane coupling agent is hydrolyzed, it also produces a condensation reaction itself, which affects the accuracy of the calculated dosage, so a certain amount of addition should be added.
Calculation formula for the dosage of silane coupling agent:
Amount of silane coupling agent (g) = powder mass (g) × powder surface area (m2/g) / coverage area of silane coupling agent (m2/g)

3. How to choose the surface modification process?
The surface modification process should be determined according to the reaction mechanism between the selected silane coupling agent and the silicon micropowder:
First, the silicon micropowder should be dynamically heated to 100-110°C, and the hydrolyzed silane coupling agent or composite coupling agent should be added by atomization.
A certain reaction time should be maintained during the reaction between the silane coupling agent and the reaction time. The effect of modification is different due to different reaction times. This heating reaction process is dehydration, condensation and curing, so that the silane coupling agent and the silicon micropowder form a stable and firm covalent bond.
The powder modified by the coupling agent will produce pseudoknot particles and hard particles after condensation, which has a great impact on the product quality. Therefore, effective classification must be carried out to ensure the quality of the product.

4. How to choose surface modification equipment?
The selection of surface modification equipment is a crucial part of the surface modification of silicon micropowder. When selecting surface modification equipment, the following requirements should be considered:
The surface modification equipment can heat and keep the silicon powder under dynamic conditions, and the holding time can be automatically controlled.
If there is an exhaust device, the water removed before and after the surface modification can be discharged in the form of steam, so that the silane coupling agent and the powder have a condensation reaction to achieve the effect of forming a covalent bond.
Ensure that the silicon micropowder is in a high-speed dynamic condition in the surface modifier.
The surface modification equipment should meet the requirements for the addition of surface modifiers.
In order to solve the false agglomeration and hard agglomeration generated in the surface modification, effective classification must be carried out, and special classification equipment should be provided for matching.
At present, the domestic active silicon powder products are not ideal because they are simply mixed with silicon coupling agents, and the powder is easy to agglomerate when mixed with resins. There are many foreign patents that propose the active treatment of silicon powder, such as The German patent proposes to mix polysilane and silicon micro-powder, and stir under ultraviolet irradiation to obtain active silicon micro-powder; Japanese experts propose to treat silicon micro-powder with silanediol derivatives, and add a catalyst during the mixing process to make the coupling agent affect the powder. The encapsulation is uniform, so that the epoxy resin can achieve the ideal bonding effect with the silicon powder.
In order to do a good job in the surface modification of silica micropowder, it is necessary to carefully understand the structure and properties of the surface modifier based on the mechanism of surface modification, and at the same time consider the substrate, main formulation and technical requirements of downstream organic polymer products. Considering the selection of reasonable modifiers, the surface modification process and equipment are determined on this basis.