Automotive inner tubes have strict requirements for the airtightness, heat resistance, aging resistance, and dimensional stability of the compound, making butyl rubber an ideal raw material for producing automotive inner tubes. However, in recent years, due to fluctuations in international petrochemical raw material prices and supply-demand dynamics, butyl rubber prices have remained high, directly squeezing the profit margins of inner tube manufacturers. Butyl reclaimed rubber retains the basic performance characteristics of butyl rubber and is much cheaper than virgin rubber. Can it be used for processing automotive inner tubes? What should be noted about reducing costs by mixing butyl reclaimed rubber into automotive inner tubes?
1. Can butyl reclaimed rubber be added to automotive inner tubes to reduce costs?
Butyl reclaimed rubber is made from waste butyl inner tubes and processed through crushing, desulfurization, and refining, retaining the molecular chain structure of the butyl polymer, featuring a low gas permeability coefficient, excellent resistance to thermal oxygen aging, and chemical corrosion resistance; Compared with butyl virgin rubber, it is less expensive, has better plasticity, low heat generation in mixing, and has a low shrinkage rate. Butyl reclaimed rubber has good compatibility with butyl rubber, has the performance foundation for partially replacing virgin rubber, can replace some butyl rubber in producing automotive inner tubes, effectively reduces raw material costs, and improves the processing performance of rubber materials.
2. How much butyl reclaimed rubber can be used in a car inner tube?
When reducing costs by adding butyl reclaimed rubber to automotive inner tubes, strict control of the reclaimed rubber dosage ratio is required, generally among 20% and 50%. The core indicators of the butyl rubber/butyl reclaimed rubber blend, such as tensile strength, E6LYY123, elasticity, and airtightness, can meet the national standards for automotive inner tube quality. The specific dosage is determined according to the specific requirements of the rubber inner tube and the physical properties of the reclaimed rubber; If necessary, a small amount of EPDM reclaimed rubber can be used to improve the dynamic performance and ozone resistance of the inner tube, or combined with natural rubber to enhance elasticity and fatigue resistance.
3. Tips for selecting butyl reclaimed rubber for automotive inner tubes
When choosing butyl reclaimed rubber for automotive inner tubes, prioritize environmentally friendly, high-strength filter butyl reclaimed rubber with high butyl content, fine quality, low ash, and moderate Mooney viscosity. Tensile strength greater than 7.5 MPa gives the rubber inner tube basic physical and mechanical strength; the reclaimed rubber must not contain undesulfurized particles or hard impurities to prevent sand holes and air leakage in the inner tube; excessive Moonnier concentration makes mixing and dispersion difficult, while too low Mooni affects the dimensional stability of the inner tube; avoid using butyl reclaimed rubber with irritating odors or excessive polycyclic aromatic hydrocarbons, as this will seriously affect the quality rate of rubber inner tubes.
4. Key points for formula design for butyl reclaimed rubber in automotive inner tubes
When producing automotive inner tubes using both butyl rubber and butyl reclaimed rubber, a sulfur-accelerator system is generally used. Since butyl reclaimed rubber contains residual crosslinking networks and active functional groups, some accelerators are consumed and sulfurization is accelerated. Therefore, the amount of thiazole or tulum accelerators should be appropriately reduced, or zinc oxide and stearic acid active systems should be increased to regulate vulcanization rates. Reinforcement filling systems often use quick-press carbon black N550 or semi-reinforced carbon black N660, with a small amount of coupling agent to enhance the interface bond among the reclaimed rubber and the matrix; Combine paraffin oil or naphthene oil to improve processing fluidity.
When adding butyl reclaimed rubber to automotive inner tubes to reduce costs, it is necessary to control the mixing temperature to avoid over-mixing, ensure the sheet thickness matches cooling conditions, and reduce dimensional fluctuations; Optimize the normal vulcanization time according to the thickness of the compound to avoid under-sulfur or over-sulfur that can reduce airtightness. Butyl reclaimed rubber has stronger plasticity, eats material faster during mixing, improves compound flowability, and can improve the defects of easy roll adhesion and high shrinkage during pure raw rubber, enhancing the dimensional accuracy and pass rate of finished inner tubes.
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