MHK ColorPigment Selection for Plastics: Organic vs Inorganic, Heat Stability, and Light Fastness
A comprehensive guide to selecting pigments for plastic coloring, covering organic vs inorganic pigments, heat stability, light fastness grades, and migration resistance.
Overview
This technical guide provides in-depth information from MHK Color's R&D engineering team. Drawing on 25+ years of polymer coloring experience and a database of 30,000+ formulations, we share practical knowledge to help you make informed masterbatch decisions.
Key Technical Considerations
When evaluating masterbatch for your application, several technical factors determine the final product quality, processing efficiency, and cost. Understanding these factors helps optimize your production and avoid common pitfalls.
Dispersion Quality
Dispersion is the most critical quality factor in masterbatch. Poor dispersion leads to color streaks, fish-eyes, inconsistent coloration, and even mechanical property degradation. MHK Color achieves sub-micron pigment dispersion through high-shear twin-screw extrusion and pre-dispersion processing, ensuring uniform color distribution in the final product.
| Dispersion Level | Particle Size | Visual Quality | Application |
|---|---|---|---|
| Standard | < 20 micron | Good for general products | General injection molding |
| High | < 5 micron | No visible agglomerates | Thin films, fibers |
| Ultra-fine | < 1 micron | Perfect surface finish | Optical, high-gloss parts |
Carrier Resin Compatibility
The carrier resin in masterbatch must be compatible with the base polymer to ensure proper dispersion and avoid mechanical property degradation. Using an incompatible carrier can cause delamination, surface defects, and reduced impact strength.
| Base Polymer | Recommended Carrier | Universal Carrier |
|---|---|---|
| PE (LDPE/HDPE) | PE | PE universal |
| PP | PP | PE/PP universal |
| PS | PS | Universal (limited) |
| ABS | ABS | Universal (limited) |
| PA (Nylon) | PA | Not recommended |
| PET | PET | Not recommended |
| PC | PC | Not recommended |
Thermal Stability
Pigments and additives in masterbatch must survive the processing temperature of the base polymer. Some pigments degrade at high temperatures, causing color shifts, gas evolution, and mechanical defects. Always verify that the masterbatch thermal stability exceeds your processing temperature by at least 20°C.
| Processing Temp Range | Pigment Class | Examples |
|---|---|---|
| 160-200°C | Most organic & inorganic | Carbon black, TiO2, phthalocyanine |
| 200-260°C | High-stability organic | Quinacridone, diketo-pyrrolo-pyrrole |
| 260-320°C | Specialty high-heat | Ceramic pigments, specialty organics |
| 320°C+ | Inorganic only | Metal oxides, complex inorganic |
Quality Control Standards
MHK Color maintains rigorous quality control standards on every production batch. Our 7-person QC team uses the following testing protocols:
- Color measurement: Spectrophotometric CIELAB measurement, Delta E < 1.0 batch-to-batch
- Dispersion testing: Microscopic inspection at 100x magnification, no agglomerates > 10 micron
- Melt flow index: Verified against specification range
- Moisture content: Karl Fischer titration, < 0.1% for hygroscopic products
- Pigment content: Ash content test to verify concentration
- Batch retention: Samples retained for 2 years for traceability
Conclusion
Selecting and working with masterbatch requires understanding of polymer chemistry, processing conditions, and quality standards. MHK Color's technical team is available for free consultation to help you optimize your coloring process. Contact us for product recommendations, samples, and technical support.
For specific product recommendations or custom formulation development, contact our technical team for free consultation and samples within 24 hours.
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