Car fuel hoses, fuel station valve diaphragms, fuel seals, and other fuel-resistant rubber products are in long-term contact with gasoline, diesel, and similar media, requiring the rubber materials to have excellent oil swelling resistance, stable mechanical properties, and a longer service life. Traditional fuel-resistant rubber products are mainly made from nitrile rubber, but the processing is difficult, raw material costs are high, and the flexibility is not great. Nitrile reclaimed rubber retains the original rubber's oil resistance. Can it be used in the production of fuel-resistant rubber products, and what should we pay attention to?
1. Advantages of using nitrile reclaimed rubber in fuel-resistant rubber products
Nitrile reclaimed rubber is made from off-spec nitrile rubber or waste nitrile products such as nitrile gloves. Its molecular chains contain polar nitrile groups, which have poor compatibility with non-polar media like gasoline and diesel, resulting in excellent oil resistance. It’s also cheaper than virgin nitrile rubber. Using it to replace nitrile rubber in fuel-resistant products can effectively reduce raw material costs. Besides, nitrile reclaimed rubber has high plasticity and good flow, and when used together with nitrile rubber, it can improve processing performance, shorten mixing time, and lower energy consumption.
2. Tips for choosing nitrile reclaimed rubber for fuel-resistant rubber products
When choosing nitrile reclaimed rubber for fuel-resistant products, it’s recommended to prioritize grades with high rubber content and medium-high acrylonitrile content (28% or higher). The higher the rubber content, the closer the physical and mechanical properties are to the original rubber; the higher the acrylonitrile content, the better the oil resistance. Mooney viscosity of 40-60 makes mixing easier and avoids sticking or scorching; screening with a mesh size of ≥40 and low impurities can reduce defects in the final products.
3. Mixing ratio and vulcanization formula for nitrile reclaimed rubber in fuel-resistant products
Using only nitrile reclaimed rubber usually cannot meet the strength requirements, so it is often blended with nitrile rubber. The mixing ratio ranges from 30% to 70%, depending on the desired performance of the rubber product. A typical formula for producing fuel-resistant rubber products with a blend of nitrile and nitrile reclaimed rubber is: Nitrile rubber 30 parts, nitrile reclaimed rubber 70 parts, zinc oxide 5 parts, stearic acid 1.5 parts, antioxidant 1 part, N330 carbon black 35 parts, dioctyl phthalate 8 parts, accelerator 3 parts, sulfur 2 parts, totaling 155.5 parts.
When using nitrile reclaimed rubber to lower costs, manufacturers also need to adjust the production process, especially the mixing process. It’s recommended to operate at low temperatures for a short time, keeping the temperature below 110°C. By designing the formula properly, fuel-resistant products can maintain good overall performance while reducing production costs further.
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