Liquid silicone needs to be produced by an injection machine, mainly used for baby products, medical supplies and electronic products (keys). Production operation method), as well as the silicone used to make the liquid silicone roller, the trademark glue, etc., mainly depends on what product you use. Generally, liquid silicone is used after vulcanization, but it can also be used as a filler, such as electrical insulation filler, or liquid silicone filler for breast augmentation, or as an additive in cosmetics.

The injection molding process applied to the molding of liquid silicone rubber has many advantages and is widely recognized. However, compared with general molding, casting and other processes, the molding equipment used in injection molding technology is more difficult to operate, the molding process is more complicated, and the technical requirements are high. waste, then the advantages of injection molding can not be well played. The following takes the pacifier injection molding process as an example to briefly analyze the injection molding process control and problems.

1. Vulcanization temperature
Vulcanization temperature is the most critical and sensitive parameter related to the quality of molded products. Usually, the mold temperature can be molded within the range of 80°C to 200°C. However, the setting of vulcanization temperature has a great relationship with vulcanization time and mold material.
In the actual production process, if you blindly increase the vulcanization temperature to improve the production efficiency, it will not necessarily achieve the purpose of reducing the cost, because to heat the mold to a higher temperature, the energy consumption required will be greatly increased, and the energy consumption cost will be increased. . Therefore, considering the total production cost, there is a relatively optimal temperature point. According to different situations, by calculating the cost, the general vulcanization temperature is relatively economical when the vulcanization temperature is 140 ℃ ~ 180 ℃.

In addition, from the perspective of mold materials, too high temperature may cause large deformation of the mold, affecting the quality of the product, and may seriously affect the opening of the mold, or even cause the mold to fail to open. Molds made in China are generally not very large when the temperature is below 170 °C. If the temperature is higher than 170 °C, the problem of mold opening is prone to occur. For high-precision products, this problem is more likely to occur. In addition, the vulcanization temperature is too high, the vulcanization of the rubber compound is too fast, the bubbles are not eliminated, and the bubble defect is formed.

Taking all factors into consideration, generally for the injection molding of smaller-sized products, the vulcanization temperature of 150°C to 160°C is more reasonable, and there are many applications.

2. Injection Conditions
When the injection temperature is 150°C, better results can be obtained when the injection pressure ranges from 40kg/cm2 to 150 kg/cm2. In different cases, different pressures also have an impact on the product. Smaller injection pressure will cause the injection molding to be under-injected, lack of material, and the product will be incomplete; when the injection pressure is too high, the injection process will be too fast, and the product will generate air bubbles due to poor exhaust, which will affect the appearance of the product. According to the experimental practice, when the injection pressure is generally 30-60 kg/cm2, the injection process is good, the silicone rubber is evenly distributed in the mold cavity, the exhaust is smooth, and the product yield is high.

In addition, during injection, the injection method also has a great influence on the appearance of the product. If the sizing material is injected all at once, it may cause overflow, which will affect the exhaust, and produce bubbles in the product, which will seriously cause difficulty in demolding. In order to avoid the adverse consequences caused by one injection, a two-stage injection method can be adopted. Most of the glue is injected in the first time, and the remaining glue is injected in the second time. This can achieve the purpose of smooth exhaust and greatly improve the yield. Generally, two injections can meet the requirements, and sometimes three injections can be used. For multiple injections, the injection pressure should also be different, and generally the second injection pressure should be lower.

3. Other influencing factors
In addition to the influence of operation control parameters such as vulcanization temperature and injection pressure on the molded product, there are many other factors that have a great impact on the product, such as the quality of the mold and the accuracy of the metering system.

The quality of mold processing also has a great influence on the molding rate of products. The mold processing is rough, the polishing degree is not good, it is easy to cause difficulty in demoulding the product, the appearance is not smooth, the transparency is poor, and the molding rate is low. Generally, the product mold is required to be refined and the cavity smoothness is good. The mold design should be reasonable, easy to open the mold, and smooth exhaust is very beneficial to the processing process.

The measurement accuracy of the metering system directly affects the quality of the product. If the accuracy is low, the mixed product formula will have a large deviation, which will affect the curing and affect the performance of the product. Generally, the measurement accuracy of imported equipment can reach less than 1%, while the domestic equipment is generally more than 2%. Therefore, in the process of silicone rubber formulation research, the accuracy of production equipment should be fully considered to ensure that when the ratio of the two components changes within a certain range, the vulcanization and performance of the product will not be greatly affected.