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Analysis of the causes of secondary vulcanization after silicone molding (liquid silicone)
Release time:
2019-07-03 12:30
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Analysis of the causes of secondary vulcanization after silicone molding (liquid silicone)
Silicone ProductsNow let's analyze: secondary vulcanization, also known as post-vulcanization, is commonly used in silicone rubber, fluorine rubber and fluorine silicone rubber vulcanization. The role of the second vulcanization: silicone rubber with peroxide vulcanization, peroxide decomposition caused by polymer reaction, the formation of low molecular compounds in the rubber will affect the mechanical properties of rubber. Silicone rubber in the first stage after heating molding, the crosslinking density is not enough, to make the further vulcanization reaction in order to increase the density of silicone rubber, tensile strength, resilience, hardness, swelling degree, density, thermal stability than a vulcanization has greatly improved.
If the second vulcanization is not carried out, the performance of the produced silica gel may be affected to a certain extent, and products with better performance cannot be obtained. The parameters of primary vulcanization may be different from those of secondary vulcanization, which is related to actual operation! Silicone vulcanization has a variety of high temperature and room temperature. Take high-temperature silica gel for example. Before vulcanization, it is what we usually call raw rubber. Mixing rubber is to refine many additives such as vulcanizing agent, release agent, etc. together with raw rubber. It can be seen from the outside. With the hand a pull on the broken, no elasticity.
If the mixed glue is vulcanized and molded at a certain temperature at a certain temperature, the product can be obtained, just like the silicone phone case we usually see.
As for the poison is not toxic, as long as the manufacturer can provide food certification, generally speaking, it is non-toxic. Silicone can also be used for medical treatment such as: silicone breast augmentation, silicone medical tubing and so on. The linear shrinkage rate should be the percentage of error between the size of the product and the original mold size after the product is cooled and solidified and molded, which can be measured according to ASTM D955 method.
In the design of plastic molds, the shrinkage rate must be considered first, so as not to cause errors in the size of the finished product, resulting in poor answers to LZ's supplementary questions: if you want to make soft, elastic and tensile silicone products, you need to use high-temperature molding silicone. Silicone, of course, must be vulcanized before it can be used. However, it seems that silicone pressure-sensitive adhesive is what we call adhesive that does not need to be vulcanized, and vulcanization can actually be called curing.
Silicone product demoulding

In the production of silicone products, many companies are using manual methods to demoulding, this method is very time-consuming and artificial energy, does not conform to the trend of the development of modern society, in order to better improve the product demoulding speed, an automatic demoulding method came into being. Unless it is a more special formulation, generally cured LSR is easy to stick to the metal surface, which brings some difficulties to the mold release.
Nevertheless, the hot tear strength of LSR rubber can meet the demoulding requirements at present, and there is basically no loss after demoulding. The most common demolding technology equipment, including fractionation column tray, push pin and air push top. Other more applied methods include drum sweeper, removal tower, and robotic operation.
When using the ejector system, the ejector system must be kept within similar tolerances. If the clearance between the ejector pin and the sleeve is excessive, or if the component is worn for too long, it will cause the appearance of component burrs. The contact pressure of the reverse cone or mushroom-shaped ejector is relatively large, which can improve the tightness of the system, so the effect is very strong.
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