The core performance requirements for oil-resistant cloth rubber tubes are excellent oil resistance, pressure resistance, adhesion, and aging resistance. They are generally processed mainly from nitrile rubber. However, nitrile rubber is expensive, and during processing, there are issues such as poor compound flowability, difficulty in hard rubber plasticization, and poor self-adhesive and roller wrapping properties. Therefore, many manufacturers have started mixing nitrile reclaimed rubber into oil-resistant cloth-filled rubber hoses to reduce raw material costs and improve rubber processing techniques. When adding nitrile reclaimed rubber to oil-resistant cloth rubber tubes, pay attention to the following issues.
1. Tips for choosing nitrile reclaimed rubber for oil-resistant cloth rubber hoses
Nitrile reclaimed rubber is made from nitrile machine head rubber, sub-brand nitrile rubber, or waste nitrile rubber products. It retains the basic performance characteristics of nitrile rubber, has a high oil resistance coefficient, good tactile elasticity, E6LYY128 heat resistance, wear resistance, and good compatibility with nitrile rubber. It can replace some nitrile rubber in producing oil-resistant cloth rubber hoses. Priority is given to nitrile reclaimed rubber with a rubber content of ≥70%, fineness of 60-80 mesh, a Mooney viscosity of [ML(1+4)100°C] of 50±5, and acrylonitrile content of ≥28%. This avoids issues such as roughness and poor adhesion caused by impurities and uneven crosslinking, resulting in good oil resistance for finished rubber hoses.
2. The proportion of nitrile reclaimed rubber in oil-resistant cloth rubber tubing
The performance requirements for oil-resistant cloth rubber hoses vary under different working conditions, and the proportion of recycled rubber varies: in special conditions of high-pressure, high-frequency oil conveying, the proportion of nitrile reclaimed rubber is controlled at 10%-20%, while in oil-resistant cloth rubber hoses operating under normal low pressure, the proportion can be appropriately increased to 25%-35%.
Different layers of oil-resistant cloth rubber hoses have different core performance requirements. The inner layer of rubber comes into direct contact with oily substances, so oil resistance requirements are strict. The proportion of nitrile reclaimed rubber is controlled at 10%-30%; The outer layer rubber requires high wear resistance and aging resistance to the compound, while the cloth layer must have good adhesion, softness, and flex resistance. The proportion of nitrile reclaimed rubber is higher than that of the inner layer.
3. Oil-resistant cloth rubber tubes are formulated with nitrile reclaimed rubber
(1) Vulcanization system: Compounds using a combination of nitrile rubber and nitrile reclaimed rubber generally use low-sulfur formulations; In the formulation of nitrile rubber, nitrile reclaimed rubber, and neoprene rubber, the ratio of neoprene is higher than that of nitrile compound, so the vulcanization system of neoprene rubber should be used.
(2) Reinforcement and filling system: When oil-resistant cloth rubber tubes are mixed with nitrile reclaimed rubber, the reinforcement system can use carbon black N330 or GPF, or combined with SRF; The outer layer should be mainly SRF; Combine calcium carbonate and clay filling.
(3) Softening plasticizer system: When producing oil-resistant clamped rubber tubing using nitrile rubber and nitrile reclaimed rubber together, the softening plasticizer should be one that is not easily dissolved by the conveyed medium. Under process requirements, the softening plasticizer should be used as little as possible; For compounding compounds used together with nitrile rubber, nitrile reclaimed rubber, and neoprene rubber, it is recommended to use ester softening plasticizers. For oil-resistant rubber hoses formed by the coreless method, solid softening plasticizers can be used in appropriate amounts.
4. Processing techniques for oil-resistant cloth rubber hoses mixed with nitrile reclaimed rubber
(1) Mixing: Nitrile rubber mixing has issues such as high heat generation, slow powder absorption, and poor roller wrapping properties; low-temperature mixing is recommended; When the proportion of nitrile reclaimed rubber is high, it is recommended to premix some of the original rubber first; Strictly control the feeding sequence, first adding zinc oxide, stearic acid, sulfur, and other difficult-to-disperse powders, and take advantage of the poor adsorption of nitrile gel to ensure uniform dispersion; Later, accelerators and softeners are added to prevent burning. Nitrile reclaimed rubber has good plasticity, and after doping, it can improve the mixing performance of the original rubber to some extent and reduce power consumption.
(2) Vulcanization: The vulcanization temperature for nitrile reclaimed rubber oil-resistant clamped rubber tubing is generally controlled at 140-155°C, with vulcanization time determined by tube thickness and vulcanization system characteristics; If the vulcanization temperature is too high, the surface of the compound may be over-sulfurized while the internal under-sulfur may occur; Set vulcanization pressure reasonably to ensure dense filling of the mold, avoiding bubbles and glue deficiency defects; If necessary, two-stage vulcanization or fully flat vulcanization can be performed to reduce permanent compression deformation. The outer layer can be appropriately vulcanized to enhance aging resistance.
Properly blending nitrile reclaimed rubber into oil-resistant cloth rubber tubes can reduce raw material costs, improve the processing performance of the compound, and lower production energy consumption. With the continuous advancement of reclaimed rubber production technology, the application prospects for nitrile reclaimed rubber in oil-resistant clapped rubber hoses will become even broader, providing strong support for the sustainable development of rubber product enterprises.
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