In the production of rubber and certain plastic products, carbon black fineness is a key factor. It affects both product performance and cost. However, the industry does not adhere to a single standard of “the finer, the better” when selecting grinding fineness. Instead, it requires determining an appropriate particle size range based on the final application scenario. Ideally, the goal of grinding carbon black from waste tire pyrolysis is to achieve its primary particle size (approximately 325-800 mesh) and ensure good dispersion. However, in practice, it is necessary to balance product performance requirements, production costs, and processing difficulties to find an optimal equilibrium among these three factors.
Advantages of Fine Carbon Black
Fine carbon black offers several advantages.
Firstly, it can significantly improve reinforcing performance, which is the core reason why the rubber industry emphasizes fineness. Reinforcement depends on surface area. Smaller particles have a larger surface area. This creates more contact points with rubber molecules. The bond is stronger. As a result, tensile strength, tear resistance, and wear resistance are enhanced.
Secondly, in coloring applications such as inks, coatings, and plastics, finer carbon black provides higher blackness, a bluish undertone, stronger tinting strength, and superior covering power.
Lastly, in theory, smaller primary particles are easier to disperse evenly in the material matrix, reducing defects caused by particle agglomeration and ensuring product quality stability.
Drawbacks of Over-Grinding
However, carbon black grinding is not simply a matter of “the finer, the better.” Excessive grinding can bring multiple drawbacks:
- Energy and cost rise sharply. Grinding from micron to nano scale requires a lot of energy. The finer the particles, the higher the cost.
- Aggravated agglomeration – Finer particles have higher surface energy. They easily re-agglomerate into secondary clusters. These clusters are hard to disperse. This cancels out the benefits of fine size.
- Processing becomes harder – In rubber, very fine carbon black raises viscosity. Mixing becomes more difficult and energy-consuming. Vulcanization may also slow down. In plastics, excessive addition can reduce melt strength and affect molding.
- Performance surplus and cost waste – In low-end applications such as colored cement bricks or low-requirement plastic fillers, fine carbon black is unnecessary, leading to waste.
- Potential structural damage – Excessive grinding may damage carbon black aggregate morphology, weakening inherent reinforcing properties.
Grinding Fineness Selection for Different Applications
High-end rubber products (tires, conveyor belts): 500–800 mesh, close to aggregate size, with strict control of surface area and DBP oil absorption value.
Mid/low-end rubber products (sidewalls, soles, inner tubes): ~425 mesh, balancing performance, cost, and processability.
Plastic masterbatch, coatings, inks: ~500 mesh, sufficient for tinting strength and dispersion.
Low-value filling applications (concrete, tracks, paving bricks): ~80 mesh coarse powder, minimizing cost.
Kesimpulan
n summary, pyrolytic carbon black from waste tires has an “optimal particle size range,” determined by the target application. Blindly pursuing extreme fineness not only increases production cost and energy consumption but may also cause agglomeration, processing challenges, and performance decline. The scientific approach is to conduct experimental testing to identify the most economical and suitable grinding fineness that meets performance
