What are the production processes for silicone products?
1. Characteristics of silicone material
A. The raw materials of silica gel are generally gel-like, somewhat similar to plasticine, colorless, translucent, and tasteless.
B. Its main feature is high temperature resistance (300℃) and low temperature resistance (low -100℃). It is currently cold and high temperature resistant rubber; at the same time, it has excellent electrical insulation, high stability to thermal oxidation and ozone, and is chemically inert Big. The disadvantage is that the mechanical strength is low, oil resistance, solvent resistance, acid and alkali resistance are poor, it is difficult to vulcanize, and the price is more expensive. Operating temperature: -60℃-＋200℃. The above is the description of silicone rubber in the manual.
C. Operating temperature: As mentioned above, it is generally set at -40°C—200°C, and can reach 230°C in a short time.
D. Aging problem:
Oil resistance, acid and alkali resistance are poor, and it has little to do with stress.
E. Bonding problem: Before surface treatment, in addition to using silica gel products as adhesives to bond with silicone parts, the adhesion to other parts must be surface activated, and the rubber surface can be vulcanized to stick firmly. Any substance that can react with rubber or cross-link it is collectively called vulcanizing agent, also called cross-linking agent. There are many types of vulcanizing agents, and they are increasing. The vulcanizing agents that have been used include sulfur, selenium, tellurium, sulfur-containing compounds, metal oxides, peroxides, resins, quinones, and amines.
F. Material hardness: According to the Shore hardness, the plastic parts can be selected between 10 degrees and 80 degrees theoretically in the domestic market. The ones that can be easily found are generally between 20 degrees and 70 degrees, and the commonly used ones are between 40 and 50 degrees.
Second, the production process of silicone products
A material shape and color
B After color matching and mixing, the milky white silica gel is transformed into various color sheets
C After mixing and shaping, the raw materials are pressed into strips and cut into strips.
D vulcanization molding
E trimming, dismantling, inspection, packaging.
F. Finished drawing
3. Product size and characteristics
A. Limit size: The thickness can be 15-20MM, if it is a sphere, the diameter can be 30MM. Generally, the recommended size of the thickness is not more than 3MM. When it is more than 3MM, it will take more curing time and increase the cost. In theory, the thickness can reach 0.2MM, but in the design, the thickness is generally 0.3MM, and 0.4MM is recommended.
B. Relative size: In terms of thickness difference, it is recommended not to exceed 3 times the thickness of the thin part. Such problems mainly depend on the temperature and pressure requirements of the material during vulcanization.
C. Shrinkage rate. The shrinkage rate of silicone material is related to the hardness of the material. Most of the secondary materials provided by the manufacturer are between 1.022-1.042. For the material of 40 to 50 degrees, the shrinkage rate is generally 1.03. Compared with plastic, silicone products will not produce similar obvious surface defects due to shrinkage.
D. Dimensional accuracy: Because silicone products are mostly one mold with multiple holes, there are many holes compared to plastic products. Therefore, the size control is not as convenient as plastic products. The general accuracy is plus or minus 0.1, and the high-precision product is plus or minus 0.05. When the fit is used for the fit between the hole of the plastic part and the button, the minimum gap is 0.1 on one side, and the recommended value is 0.2 on one side.
E. Shape design: For rubber sleeve parts, it is generally sufficient to provide the original drawing to the mold factory according to the shape of the product, and the explanation of the matching problems is left to the mold factory's own decision. In general, depending on the size of the product, the fit between the rubber sleeve and the product is generally a negative deviation of 0.2-0.5 on one side.