What issues should be paid attention to when injecting liquid silicone encapsulation products?

Liquid silicone, with its excellent high and low temperature resistance, electrical insulation, chemical stability, and biocompatibility, has been widely used in various fields such as medical, electronics, automotive, and baby products. And encapsulation injection technology is the process of injecting liquid silicone onto pre formed or pre fabricated components, forming a layer of silicone outer skin or a composite structure tightly bonded with other materials. This process not only requires a high degree of technical precision, but also requires a deep understanding and control of multiple aspects such as material properties, mold design, injection parameters, etc
1、 Material selection and pretreatment
1.1 Material compatibility
During the encapsulation process, liquid silicone gel needs to form a good bond with the substrate material (such as plastic, metal, etc.). Therefore, the selection of materials is crucial. It is necessary to ensure good chemical compatibility between the selected silicone and the substrate material to avoid phenomena such as delamination and delamination during subsequent use. This usually requires verifying the compatibility of materials through experiments, including interface adhesion testing, aging testing, etc.
1.2 Material Preparation
The substrate material needs to undergo necessary pretreatment before encapsulation, such as cleaning and degreasing, drying treatment, surface activation, etc., to improve the bonding strength between the silicone gel and the substrate. For plastic parts, it is also necessary to consider whether their surface energy meets the requirements of silicone wetting. If necessary, methods such as plasma treatment and primer can be used to improve the surface energy.
2、 Mold design and manufacturing
2.1 Mold accuracy
Liquid silicone injection molding requires extremely high precision for molds. The dimensions, shape accuracy, and surface roughness of the mold cavity must be strictly controlled to ensure the dimensional stability and appearance quality of the product. At the same time, the exhaust design of the mold should also be reasonable to avoid the generation of bubbles or defects during the injection process.
2.2 Temperature control
The curing process of liquid silicone is greatly affected by temperature, so the mold needs to have a precise temperature control system. By adjusting the mold temperature, the curing speed and degree of silicone can be controlled, thereby optimizing the physical properties and appearance quality of the product.
3、 Injection process parameters
3.1 Injection pressure and speed
The injection pressure and speed are key factors affecting the filling effect of liquid silicone gel. Excessive or insufficient pressure and speed can lead to product defects such as under injection, flash, bubbles, etc. Therefore, it is necessary to adjust the optimal injection pressure and speed through trial molding based on the product structure and silicone properties.

3.2 Curing time and temperature
The curing time and temperature of liquid silicone need to be set according to specific formula and process requirements. The curing time is too short, and the silicone is not completely cured, which affects the product performance; If the curing time is too long, it may reduce production efficiency. At the same time, the curing temperature also needs to match the curing curve of the silicone gel to ensure that the product achieves the expected physical properties and chemical stability.
4、 Product post-processing and testing
4.1 Removing burrs and flying edges
After liquid silicone injection molding, there may be burrs or flying edges on the edges of the product. These defects not only affect the appearance quality of the product, but may also reduce its sealing and service life. Therefore, appropriate deburring techniques (such as manual trimming, mechanical cutting, frozen deburring, etc.) need to be used for processing.
4.2 Quality Inspection
The product needs to undergo strict quality testing, including size inspection, appearance inspection, performance testing, etc. Especially for products in sensitive fields such as medical and food contact, special requirements such as biocompatibility and toxic and harmful substance testing need to be conducted.
5、 Environmental and safety factors
5.1 Production Environment
Liquid silicone injection molding should be carried out in a clean, dust-free, and temperature and humidity controlled environment. The production workshop needs to be regularly cleaned and disinfected to prevent impurities from contaminating the products. At the same time, it is necessary to control the number of dust particles in the air to reduce surface defects on the product.
5.2 Safety Protection
Liquid silicone gel and its curing agent may cause irritation or harm to the human body during use. Therefore, necessary safety measures need to be taken, such as wearing personal protective equipment such as goggles, gloves, masks, etc; Ensure good ventilation in the workplace; Set up emergency facilities such as emergency showers and eye wash stations.
In summary, liquid silicone encapsulated injection products are a complex process involving multiple aspects such as material science, mold design, injection technology, quality testing, and environmental safety. Only by strictly controlling and finely operating at every stage can high-quality and high-performance liquid silicone encapsulation products be produced.