Hard rubber has a hard texture and excellent electrical insulation properties. It is a product of the combination of rubber hydrocarbon and a large amount of sulfur. It can be said to be another state of vulcanized rubber. In actual production, natural rubber is a common raw material in the preparation process of hard rubber. A reasonable design of hard rubber formulations using natural rubber as the main raw material can further optimize the processing performance of hard rubber and the comprehensive indicators of the finished product; increase the amount of low-priced rubber raw materials , The amount of rubber accessories reduces costs.
1. Rubber combined use
(1) Combined use with styrene-butadiene rubber: In actual production, hard rubber processed from natural rubber as the main raw material has the characteristics of high mechanical strength, low water absorption, good electrical insulation, and chemical resistance. When the amount of sulfur is appropriate, styrene-butadiene rubber hard rubber generates little heat in the vulcanization reaction, which is beneficial to the temperature control of the vulcanization process. Therefore, an appropriate amount of styrene-butadiene rubber can be added to the natural rubber hard rubber formula to improve the hard rubber vulcanization performance and the aging resistance of the finished product.
(2) Combined use with reclaimed rubber: natural rubber hard rubber formula can be mixed with reclaimed rubber in an appropriate amount, which can not only reduce the production cost of hard rubber, but also reduce the shrinkage of the rubber material, which is convenient for calendering and extrusion process operations. It is beneficial to control the temperature rise of the rubber compound in vulcanized 2YLYY130, and reduce the deformation of the product during direct steam vulcanization. In actual production, mixing with appropriate amount of reclaimed rubber with high content of rubber, such as latex reclaimed rubber and tire tread reclaimed rubber, the mechanical properties of hard rubber remain basically unchanged.
2. Vulcanization system
(1) Vulcanizing agent: Natural rubber hard rubber is generally vulcanized with sulfur, and when used with selenium, it can promote vulcanization and improve the heat resistance of hard rubber. In actual production, when the amount of sulfur in 100 parts by mass of raw rubber is less than 4 parts, it is soft rubber. When the amount of sulfur is 10-25 parts, semi-hard rubber can be prepared. When the amount of sulfur exceeds 37 parts, it is hard rubber.
(2) Accelerator: Natural rubber hard rubber can be used to increase the reaction rate of rubber and sulfur and shorten the reaction time. Commonly used organic accelerators include guanidine, aldehyde amine accelerators, inorganic accelerators such as calcium oxide, magnesium oxide, etc.; the combination of guanidine or aldehyde amine accelerators with magnesium oxide has a better effect, such as magnesium oxide/promote Agent D. If the natural rubber hard rubber formula contains a large amount of hard rubber powder, reclaimed rubber or other fillers, the amount of accelerator can be appropriately increased or a small amount of thiazole accelerator can be used in combination.
3. Filling system
Adding a large number of fillers to natural rubber hard rubber can effectively reduce the cost of raw rubber, especially for thick products. Commonly used fillers include clay, talcum powder, recrystallized powder, hard rubber powder, etc. The hard rubber powder has the best filling effect. good. Natural rubber filled with hard rubber powder will not significantly reduce the mechanical strength of the rubber; it can reduce the deformation of the semi-finished product during storage and vulcanization; reduce the shrinkage of the rubber material, so that the size of the semi-finished product for calendering and extrusion is more accurate; reducing the heat of vulcanization, Especially suitable for high temperature vulcanization and thick product production.
Hard rubber powder is crushed by hard rubber, or specially processed. In actual production, hard rubber powder can be divided into four types according to composition and manufacturing method: raw rubber, sulfur type, raw rubber, sulfur and high-quality reclaimed rubber type, raw rubber, sulfur and inorganic filler type, waste hard rubber products Shaped. It should be noted that hard rubber powder will absorb sulfur and accelerators during vulcanization. Therefore, when a large amount of natural rubber hard rubber is filled with hard rubber powder, the amount of sulfur and accelerators in the formula should be appropriately increased.
4. Soften the system
The softeners commonly used in the preparation of natural rubber hard rubber include mineral oil, petrolatum, asphalt, paraffin, coumarone resin, ointment, etc.; reasonable control of the amount of softener can better ensure the impact resistance of hard rubber, Breaking strength and heat resistance to avoid vulcanization deformation.
Hard rubber itself is not prone to aging, so it is not necessary to use antioxidants in the formulation. In actual production, when reducing the production cost of natural rubber hard rubber, you can use reclaimed rubber or increase the amount of filler. There is a chance that the editor will continue to share the advantages and disadvantages of these two methods with you.
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