When using nitrile rubber to produce oil resistant, wear-resistant and other rubber products, appropriate use of nitrile recycled rubber can effectively reduce raw material costs. In actual production, sulfur is most widely used in nitrile rubber products. How to design a more reasonable vulcanization system when using nitrile rubber/nitrile recycled rubber and producing rubber products with sulfur vulcanization; What issues should we pay attention to? Today, the editor will share with you the key points for choosing sulfur vulcanization for nitrile rubber/recycled rubber.
1. The sulfur vulcanization system of nitrile rubber/nitrile recycled rubber requires reasonable control of sulfur content
When producing rubber products using nitrile rubber/nitrile recycled rubber as the main raw material, it is necessary to control the amount of sulfur due to the lower solubility of sulfur in nitrile rubber compared to natural rubber; If necessary, insoluble sulfur can be used to avoid frost spraying. In actual production, the sulfur content in the nitrile rubber/nitrile recycled rubber 2SLYY44 blend is generally controlled among 1.5 and 2 parts; When the amount of nitrile regenerated rubber is high, the amount of sulfur can be appropriately increased; When choosing nitrile rubber with high acrylonitrile content, the amount of sulfur needs to be appropriately reduced.
For example, when using nitrile 18 and nitrile regenerated rubber together, the amount of sulfur should be controlled among 1.75-2 parts; When using nitrile 26 and nitrile regenerated rubber together, it is recommended to control the amount of sulfur among 1.5 and 1.75 parts. In actual production, low sulfur coordination can improve the heat resistance of vulcanized rubber, reduce compression set, and improve other properties. Therefore, nitrile rubber/nitrile recycled rubber can also use a low sulfur (sulfur content less than 0.5 parts) high promotion vulcanization system.
2. The right accelerator needs to be selected for the sulfur vulcanization system of nitrile rubber/nitrile recycled rubber
When choosing sulfur vulcanization for nitrile rubber/nitrile recycled rubber blends, the commonly used accelerators are thiuram and thiazole accelerators. Among them, the nitrile vulcanizate with Qiu Lamb type accelerator has better properties, especially good compression permanent deformation and high processing safety. Nitrile rubber and sulfur vulcanized rubber can also use sulfenamide type accelerators, while amine and guanidine type accelerators are often used as auxiliary accelerators.
(1) Heat resistant rubber vulcanization system coordination: Promoters TMTD, TRA, TRT are combined with sulfur, and low sulfur or sulfur free coordination is adopted. The heat resistance of nitrile rubber/recycled rubber vulcanizate is excellent.
(2) Combination of compression and scorch resistant rubber vulcanization system: When sulfur is used in combination with a sulfurized thiram, the rubber has lower compression set and minimum scorch tendency. The low sulfur formula of high volume thiuram and sulfonamide compounds or thiuram and thiazole compounds has excellent physical and mechanical properties, good heat resistance, small compression set, and is not prone to scorching and frost spraying.
3. The right active agent needs to be selected for the sulfur vulcanization system of nitrile rubber/nitrile recycled rubber
When using a sulfur accelerator system in the combination of nitrile rubber and nitrile recycled rubber, zinc oxide and stearic acid are commonly used as vulcanizing activators. The dosage of zinc oxide in sulfur sulfide and sulfur free sulfide systems is usually among 1.0 and 5.0 parts, the customary dosage of zinc oxide is 5 parts, and the dosage of stearic acid is generally 1.0 parts. To improve the heat resistance of nitrile rubber, a cadmium magnesium vulcanization system can also be used.
When using sulfur vulcanization as the main raw material for rubber products made of nitrile rubber/nitrile recycled rubber, it is recommended to reduce the amount of sulfur and increase the amount of accelerator to adjust the degree of vulcanization and vulcanization rate due to the slower vulcanization speed and lower solubility of nitrile rubber compared to natural rubber; The low solubility of sulfur in nitrile rubber can also cause uneven dispersion of sulfur, resulting in brown spots on light colored products and hard spots on black products, resulting in a decrease in product strength, especially in thermal tearing strength.
In the future, the editor will continue to discuss with you the selection techniques and key points for the vulcanization system of nitrile rubber/nitrile recycled rubber production rubber products.
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