Carbon Black Dispersion Tester - QualiCBCT™-100 for Rubber Compounds
The QualiCBCT™-100 Carbon Black Dispersion Tester grades how evenly carbon black and other fillers spread through rubber compounds. Mixing rooms, tire plants, compounders, and rubber R&D labs use it to check each batch before molding or extrusion. The instrument images a freshly cut specimen under 30° oblique light at 2.5 µm resolution. Software then assigns a dispersion grade from 0.1 to 10. These numbers replace subjective visual ratings and let engineers trend results over time.
Poor dispersion leaves undispersed agglomerates that act as stress concentrators inside cured rubber. These flaws lower tensile strength, tear resistance, abrasion life, and fatigue performance. They also raise scrap rates in finished goods. A quick dispersion check tells process engineers whether mixing time, temperature, or rotor speed needs adjustment. The QualiCBCT™-100 is designed to align with ASTM D7723 and ISO 11345, the rating methods customers already use.
Qualitest built this tester for routine QC and formulation research alike. Operators can select lenses from 100× to 1000× to study agglomerates at different scales. The software counts particles, measures their diameter and area, and maps size distribution across the field of view. A library of 1,000 user-defined file groups stores in-house reference images for custom grading. Saved and printed reports give each batch a traceable dispersion record.
Theory and Method
The method relies on a simple mechanical effect at a freshly cut rubber surface. A sharp blade slices cleanly through rubber where filler particles are finely distributed. Undispersed agglomerates are much harder than the surrounding matrix, so the blade deflects around them. The cut surface then shows raised bumps where agglomerates stand proud and pits where they pulled away. Surface roughness rises with the amount and size of undispersed filler.
The QualiCBCT™-100 turns that roughness into an optical signal. A halogen source lights the specimen at a 30° angle, so each bump and pit casts a shadow beside a bright edge. The camera records the field at 100× magnification with 2.5 µm resolution. Software converts the image to gray levels and calculates a threshold that separates defects from the smooth background. A bubble-elimination step then filters out air voids so they do not count as agglomerates.
The software counts each remaining agglomerate and sizes it by diameter and area. It sums the defect area as a share of the field and maps it onto a 10-grade scale, where higher grades mean better dispersion. This scale follows the same logic as the ISO 11345 reference photographs, which rate dispersion from 1 to 10. Agglomerate range settings let operators focus on the particle sizes that matter for their product. Saved grade images then serve as comparison standards for future batches.
