Nitrile rubber is made of acrylonitrile and butadiene monomer copolymerization, with excellent oil resistance, good wear resistance, heat resistance and chemical resistance, and is widely used in rubber products such as seals, hoses, tapes, pads, oil-resistant soles, rubber rollers, etc. When using nitrile rubber to produce rubber products, a full understanding of the processing properties of nitrile rubber can optimize the production process, reduce material waste, improve product quality, and then reduce costs.
1. Characteristics of nitrile rubber processing performance
(1) It is recommended to adopt the segmented molding method of low temperature, small roller distance and small capacity during the plasticizing of nitrile rubber, which has a large power consumption during plastic refining.
(2) Nitrile rubber mixing heat is large, the powder is unevenly dispersed, and it is not easy to wrap the roller, it is recommended to use low-temperature mixing, and pay attention to the feeding sequence, and the powder such as sulfur and zinc oxide that is not easy to disperse and has low solubility is added first. When nitrile rubber is sulfur vulcanized, because acrylonitrile will reduce the solubility of sulfur, it is better to add sulfur first when mixing.
(3) When the low-temperature nitrile rubber is directly mixed, the roller needs to be fully cooled; It is recommended that high-temperature nitrile butadiene rubber and high-moni viscosity value nitrile butadiene rubber be mixed at low temperature to obtain the required plasticity.
(4) Nitrile rubber calendering and extrusion operation are difficult, and the calendering and extrusion temperature is lower.
(5) Nitrile butadiene rubber will not be vulcanized and returned to its original state at higher temperatures. The use of high temperature vulcanization can improve the degree of vulcanization and reduce the compression deformation of nitrile rubber. The tensile strength of nitrile rubber can be improved by low-temperature vulcanization, but the heat and water resistance of vulcanized rubber are poor. The vulcanization of nitrile rubber avoids under-sulfur, otherwise it will affect the compression deformation, aging resistance and oil resistance of the rubber.
(6) The thermal tearing performance of nitrile rubber is poor, and the vulcanized products need to use cold start molds.
2. Key points of rubber formula to improve the processing performance of nitrile rubber
(1) Nitrile rubber has high viscosity, poor processing performance and low self-viscosity, and the selection of appropriate softener can reduce the viscosity, improve the process performance and low temperature performance of nitrile vulcanized rubber. When nitrile rubber needs to be bonded with fabrics E4LYY325, it is recommended to use softeners such as esters, coal tar and coumerone, which are conducive to the bonding of rubber materials and fabrics, and are beneficial to calendering and extrusion; Appropriately reducing the rubber content is conducive to the flatness of rubber calendering and extrusion.
(2) Appropriate use of liquid nitrile rubber to replace nitrile rubber to improve the process performance of rubber compound.
(3) The commonly used vulcanization systems for nitrile rubber products include sulfur-accelerator system, low-sulfur vulcanization system, sulfur-free vulcanization system and peroxide vulcanization system.
(4) Use plasticizers in an appropriate amount.
(5) Black and dark nitrile rubber products can use spray carbon black to improve the process performance of vulcanized rubber; Light-colored nitrile rubber products are recommended to use silica and hard clay to increase volume and reduce costs.
(6) Compared with nitrile rubber, nitrile reclaimed rubber is easier to produce and compress, the expansion and contraction of unvulcanized rubber is small, the processing heat generation is less, and the sensitivity to heat is small; The appropriate use of nitrile rubber in the formulation of nitrile rubber products can not only reduce the cost of raw rubber, but also improve the processing performance of rubber compound.
In the processing of nitrile rubber products, strict control of the plastic, mixing, calendering, extrusion and vulcanization of nitrile rubber is essential to improve product quality and reduce costs. Proper adjustment of processing conditions and vulcanization formula, especially when nitrile rubber and nitrile reclaimed rubber are used together to produce rubber products, the processing performance of nitrile rubber can be effectively improved, and rubber products with better performance and lower cost can be produced.
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