Production Technology of Silicone Rubber Products
I. Properties of Silica Gel Materials
A. silicone raw materials are generally gelatinous, somewhat similar to rubber paste, colorless and translucent, tasteless.
B. Its main characteristics are high temperature resistance (up to 300 C) and low temperature resistance (lowest - 100 C). It is the best cold and high temperature resistant rubber at present. At the same time, it has excellent electrical insulation, high stability to thermal oxidation and ozone, and high chemical inertia. The disadvantages are low mechanical strength, poor oil resistance, solvent resistance, acid and alkali resistance, difficult vulcanization and high price. Use temperature: - 60 ~200 ~C. These are the instructions for silicone rubber in the manual.
C. Use temperature: As mentioned above, it is generally set to - 40 C - 200 C, which can reach 230 C in a short time.
D. Aging issues:
Oil resistance, acid resistance and alkalinity resistance are poor, and have little relationship with the stress.
E. Adhesion problem: Before surface treatment, in addition to using silica gel products as adhesives to bond with silica gel parts, all other parts must be adhered to by surface activation, vulcanization treatment of rubber surface can be adhered. Any substance that can react with or cross-link rubber is called vulcanizing agent, also known as cross-linking agent. There are many kinds of vulcanizing agents, and they are increasing. Sulfur yellow, selenium, tellurium, sulfur compounds, metal oxides, peroxides, esters, quinones and amines have been used.
F. Material hardness: According to Shaw hardness, rubber parts can be theoretically selected between 10 degrees and 80 degrees in the domestic market. It's usually between 20 and 70 degrees that can be easily found. The most commonly used is between 40 and 50 degrees.
II. Production Technology of Silica Gel Products
A Raw Material Shape and Color
B Modified by opalescent silica gel after color matching and mixing
After C mixing and shaping, the raw materials are pressed into strips and cut into strips.
D vulcanization
E trimming, edge removal, inspection, packaging.
F. finished product drawings
III. Product Size and Characteristics
A. Limit size: The thickest part can be 15-20MM, and if it is a sphere, the diameter can be 30MM. Generally, the recommended size of thickness is not more than 3MM. When it is larger than 3MM, more vulcanization time will be spent and the cost will be increased. The thinnest treatment can reach 0.2MM in theory, but the thinnest treatment is 0.3MM in design and 0.4MM is recommended.
B. Relative size: In terms of thickness difference, the thinnest and thickest parts should not exceed three times. Such problems mainly depend on the requirements of temperature and pressure during vulcanization.
C. Shrinkage rate. The shrinkage rate of silica gel material is related to the hardness of the material. The secondary materials supplied by the manufacturer are mostly between 1.022 and 1.042. For materials with 40 to 50 degrees, the shrinkage rate is generally 1.03. Compared with plastics, silica gel products do not produce similar obvious surface defects due to shrinkage.
D, dimensional accuracy: because silica gel products are mostly one mold and multi holes, the number of holes is very large relative to plastic products. Therefore, the size control is not as convenient as plastic products. The general precision is positive or negative 0.1, and the high precision product is positive or negative 0.05. When the fit is used to fit the holes and keys of plastic parts, 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, the original drawing can be provided to the mould factory according to the shape drawing of the product. The problem of cooperation is explained and decided by the mould factory itself. Generally, 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.