Masterbatch Dispersion FAQ: Specks, Streaks, and How to Fix Them

Solving Specks and Streaks

Dispersion — how uniformly pigment is distributed in plastic — is the most common source of color defects. Specks, streaks, and color variation almost always trace back to dispersion. This FAQ explains the causes and solutions.

What is pigment dispersion?

Dispersion is the process of breaking down pigment agglomerates and distributing individual particles uniformly through the polymer. Good dispersion means no visible pigment clusters in the finished plastic.

What causes specks in my plastic?

Specks are undispersed pigment agglomerates. They result from insufficient shear during compounding, poor pigment wetting, or using pigment powder instead of well-dispersed masterbatch.

What causes color streaks?

Streaks usually indicate uneven mixing — often from carrier resin melt-flow mismatch with your base resin, or inadequate screw mixing in your processing machine.

How is dispersion quality measured?

Dispersion is measured by filter pressure value (FPV) — pressure build-up from agglomerates on a screen pack — and by microscopic inspection. Lower FPV and no agglomerates above 10 μm indicate good dispersion.

Why does dispersion matter for thin film and fibers?

In thin film (15–80 μm) and fine fibers (10–30 μm), even a single agglomerate becomes a visible defect or causes filament breakage. These applications demand the highest dispersion quality.

How does twin-screw compounding improve dispersion?

Twin-screw extruders apply high shear through intermeshing kneading blocks, breaking agglomerates to sub-micron size. Single-screw machines cannot match this dispersion capability.

What are dispersants?

Dispersants are additives (waxes, stearates, hyperdispersants) that coat pigment surfaces, improving wetting and preventing re-agglomeration. They are essential for difficult pigments like carbon black.

How can I fix dispersion problems?

Switch to a higher-quality masterbatch with verified dispersion, check your carrier resin matches the base resin, verify dosing accuracy, and ensure your processing screw provides adequate mixing.

What dispersion standard should I expect?

Professional masterbatch achieves no agglomerates above 10 μm, FPV below 50 bar (below 20 bar for demanding applications), and flawless drawdown films with no visible specks.

Conclusion

Dispersion quality separates professional masterbatch from commodity products. MHK Color compounds on twin-screw extruders with rigorous FPV and microscopic testing, delivering sub-micron dispersion for even the most demanding film and fiber applications.