It is understood that stearic acid is a white flake, bead or block solid at room temperature. It is composed of saturated fatty acids mainly C16 and C18. It is insoluble in water, slightly soluble in benzene and carbon disulfide, easily soluble in hot ethanol, non-toxic and tasteless, and has the general chemical properties of organic carboxylic acids. Stearic acid is a fatty acid widely found in nature. Almost all oils contain stearic acid in varying amounts. The content is higher in animal fats. For example, the content in butter can reach 24%, and in vegetable oils it is less. , tea oil is 0.8%, palm oil is 6%, but the content of cocoa butter is as high as 34%. There are two main production methods for industrial stearic acid: fractionation method and pressing method. A decomposing agent is added to the hardened oil, and then it is hydrolyzed to obtain crude fatty acids, which are then washed, distilled, and decolorized to obtain the finished product, while glycerol is produced as a by-product.
Stearic acid can play the role of these additives in rubber:
1. Plasticizer: improve the softness and ductility of rubber. A certain amount of plasticizer needs to be added to rubber during the manufacturing process to improve its processing performance and service life. Stearic acid has a high plasticizing effect, which can make rubber easier to process and shape, and can also improve the heat resistance and cold resistance of rubber.
2. Stabilizer: Prevent rubber aging and deterioration. Rubber will be affected by factors such as oxidation, ultraviolet rays, heat and moisture during long-term use, resulting in reduced performance and shortened life. Stearic acid can react with free radicals in rubber to form stable compounds that prevent further reactions of free radicals, thus extending the service life of rubber.
3. Anti-aging agent: protects rubber from oxidation and squeaking. Rubber will be affected by oxidation and ultraviolet rays during use, causing its surface to turn yellow, harden and crack. Stearic acid can form a protective film with the rubber surface to prevent oxidation and squeak damage, thereby maintaining the original color and luster of the rubber.
4. Foaming agent and release agent: When manufacturing foam rubber, stearic acid can be used as a foaming agent, and stearic acid can also be used as a release agent for rubber products: reclaimed rubber is used in the production When it is difficult to demould rubber products during the process, adding a certain amount of stearic acid can help the reclaimed rubber products to demould smoothly. Therefore, stearic acid can be used as a release agent for reclaimed rubber products.
5. Other additive functions: Stearic acid is a vulcanization activator widely used in natural rubber, synthetic rubber and latex. It can also be used as a plasticizer and softener. In the process of producing synthetic rubber, stearic acid is added as an emulsifier.
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