Natural rubber has high mechanical strength, good elasticity, but poor aging resistance and medium resistance, high prices and large price fluctuations. Therefore, it is often used in combination with other synthetic rubber and recycled rubber to improve the overall performance of rubber products and reduce costs. In actual production, sulfur vulcanization systems are selected for most of the natural rubber blends. The diffusion effect of sulfur in different rubbers is different, and the combination of vulcanization accelerators and vulcanization characteristics are different.
1. The diffusion of sulfur in natural rubber and rubber
Natural rubber can be used together with styrene butadiene rubber, butadiene rubber, butyl rubber, isoprene rubber, latex reclaimed rubber, tire reclaimed rubber, etc. Taking natural rubber/butyl rubber and natural rubber/styrene butadiene rubber as examples, the sulfur content in the two rubbers is related to the diffusion of sulfur in the rubber.
After the natural rubber/butyl rubber mixed rubber is mixed with sulfur, a large amount of sulfur is mixed in the natural rubber, resulting in the lower sulfur content at the two-phase interface in the mixed rubber and the sulfur content in the butyl rubber; at this time, the natural rubber 2YLYY914 The sulfur in the butyl rubber can gradually diffuse into the butyl rubber. In the natural rubber/styrene-butadiene rubber combined rubber, the mixed sulfur is also mixed in a large amount of natural rubber, and the sulfur in the natural rubber can also gradually diffuse into the styrene-butadiene rubber.
2. Commonly used sulfur-accelerator compounding skills for natural rubber and rubber
When natural rubber is used in combination with other rubbers, a variety of sulfur-accelerator coordination systems can be adopted, including ordinary sulfur vulcanization systems, or low-sulfur or sulfur carrier vulcanization systems. In actual production, vulcanization accelerators such as benzothiazole sulfonamide or dithiomorpholine are used in the actual production of natural rubber combined with sulfur, and the physical and mechanical properties of the vulcanized rubber are good. Using sulfur and sulfur carriers (such as dithiomorpholine or thiuram disulfide accelerator) vulcanization system or semi-effective vulcanization system (low sulfur and high acceleration), natural rubber combined with rubber has better heat aging performance.
Take natural rubber/butadiene rubber combined rubber as an example: when using sulfur vulcanized NR/BR combined rubber, you can choose accelerators CBS, TMTD, DTDM, etc. In the traditional sulfur system, sulfur can be combined with a small amount of accelerator CBS, the semi-effective vulcanization system can use the sulfur/CBS/DTDM combination system, and the effective vulcanization system can use the ratio of CBS/DTDM/TMTD in the ratio of 1/1/1.
3. The diffusion effect of accelerator in natural rubber and rubber
When an effective vulcanization system is adopted for the combination of natural rubber and butadiene rubber, the vulcanization accelerators CBS, DTDM, and TMTD have different dispersion states in the two rubbers. In the continuous phase of natural rubber, three vulcanization accelerators can be dispersed in it; in the dispersed phase of butadiene rubber, only CBS and DTDM can be dispersed, and TMTD is not easy to enter the butadiene rubber components. After vulcanization with rubber, the natural rubber component of the continuous phase has a higher degree of vulcanization, and the degree of vulcanization in the dispersed phase of the butadiene rubber component is relatively small; therefore, the degree of vulcanization network generated in the natural rubber component is much greater than that of the butadiene rubber component The degree of vulcanization network in the score.
When selecting a sulfur-accelerator system for the combined use of natural rubber, synthetic rubber, and reclaimed rubber, rubber product manufacturers must combine the dispersion of sulfur and accelerators in various rubbers and the physical properties of the finished product, and reasonably determine the types and types of sulfur and vulcanization accelerators. Dosage, the editor will continue to discuss related issues with you later.
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