Injection molding process of silicone products

OneSilicone material properties


A. The silica gel material is generally gelatinous, somewhat similar to plasticine, colorless, translucent and tasteless.

B. The main features are: high temperature resistance (up to 300 ° C) and low temperature resistance (lowest -100 ° C), is currently the best cold and high temperature resistant rubber; at the same time excellent electrical insulation, high stability to thermal oxidation and ozone , chemically inert. The disadvantage is that the mechanical strength is low, oil resistance, solvent resistance and acid and alkali resistance are poor, it is difficult to vulcanize, and the price is relatively expensive. Use temperature: -60 ° C ~ +200 ° C. The above is a description of silicone rubber in the manual.

C. Operating temperature: As described above, it is generally set to -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 there is little relationship with the stress.

E. Adhesive problem: Before the surface treatment, except the silicone product is used as the adhesive and the silicone parts are bonded, the other parts must be surface-activated, and the vulcanized surface can be cured. Any substance that can be vulcanized or crosslinked with rubber is collectively referred to as a vulcanizing agent, also known as a crosslinking agent. There are many types of vulcanizing agents, and they are still increasing. The vulcanizing agents that have been used include sulfur, selenium, tellurium, sulfur compounds, metal oxides, peroxides, resins, terpenes and amines.

F. Material hardness: The rubber parts can be theoretically selected between 10 and 80 degrees in terms of Shore hardness in the domestic market. It can be easily found in 20 to 70 degrees, and the most commonly used is 40 to 50 degrees.

 

TwoIntroduction to silicone raw materials


Silicone is increasingly favored by people for its environmental performance. Nowadays, more and more other materials on the market are replaced by silicone material. If you want to know more about silicone products, you must start with silicone raw materials.

1. Silicone raw materials can be divided into domestic materials and imported materials according to their sources.

Domestically produced materials mainly include: Dongjue, Ruiying, Hongda, Tianyu, New Oriental, and other large producers.

The main imported materials are: Shin-Etsu, Toshiba, Dow Corning America, Rhodia France, WACKER Germany, etc.


2. Silicone raw materials can be divided into ordinary silica gel and meteorological silica gel according to their performance.

Ordinary silica gel

Color: translucent, milky white, light yellow, gray, etc.

Hardness: 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, etc., commonly used between 40 ° - 70 °.

Density: 1.1-1.12g/cm2

Elongation: 400%

Uses: The most used are low-end silicone products such as mobile phone buttons, miscellaneous pieces, conductive adhesives.

 

Meteorological silica gel, also known as pure silica gel

Color: Transparent.

Hardness: 30°, 40°, 50°, 60°, 70°, 80°, etc., commonly used between 40° and 60°.

Density: 1.1-1.12g/cm2

Elongation: 600%-700%

Features: Because of the transparency of this material, the tensile strength is strong. The cost is high.

Uses: Silicone tube, protective sleeve and other high-end products that require high elasticity.

 

3. The silica gel raw materials can be divided into solid silica gel and liquid silica gel according to physical properties.

Solid silica gel is mainly used for molded products. For example: silicone sleeve, silicone tableware, silicone buttons, etc., liquid silicone is mainly used for extrusion molding products, such as silicone nipples, silicone tubes and so on.

 

ThreeSilicone product production process


A. Material shape and color

B. After the color mixing and mixing, the milky white silica gel is changed into a sheet C of various colors, and then the raw materials are pressed into strips and cut into strips.

D. Vulcanization molding

E. Trimming, trimming, inspection, packaging.

F. Finished drawing

 

FourProduct size and characteristics


A. Limit size: 15~20MM can be achieved at the thickest point. If it is a sphere, it can be 30mm in diameter. The recommended thickness for general thickness is no more than 3MM. When it is greater than 3MM, it will cost more curing time and increase cost. The thinnest processing can reach 0.2MM, but the design is generally the thinnest 0.3MM, 0.4MM recommended.

 

B. Relative size: In the thickness difference, the thinnest part and the thickest part are recommended not to exceed 3 times. Such problems are mainly determined by the temperature and pressure requirements of the material vulcanization.

 

C, shrinkage rate: The shrinkage rate of the silica gel material is related to the hardness of the material. The secondary material provided by the manufacturer is mostly between 1.022 and 1.042. For the material of 40 to 50 degrees, the shrinkage rate of 1.03 is generally taken. Compared to plastics, silicone products do not produce similar apparent surface defects due to shrinkage.

 

D. Dimensional Accuracy: Because silicone products are mostly a multi-hole, the number of holes is very large compared to plastic products. Therefore, there is no convenience in the size control of 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 and the button of the plastic part, the minimum gap is 0.1, and the recommended value is 0.2 on one side.

 

E. Shape design: For the rubber sleeve parts, the original drawing can be provided to the mold factory according to the outline drawing of the product. The explanation of the matching problem is decided by the mold factory. Under normal circumstances, depending on the size of the product, the fit of the rubber sleeve to the product is generally a negative deviation of 0.2 to 0.5 on one side.


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