In the world of plastics coloring, weather resistance (or weatherability) is a make-or-break property for products exposed to the elements. Rated on a 1–8 scale—where 8 is excellent and 1 is poor—this metric measures a pigment’s ability to withstand UV radiation, oxidation, moisture, heat, and chemical attack outdoors. Whether you’re manufacturing automotive parts, outdoor furniture, or architectural profiles, choosing the right pigment grade ensures vibrant, long-lasting color. This blog dives deep into the science, factors, applications, and top-performing brands based on industry benchmarks.
What Influences Weather Resistance in Plastic Pigments?
No two pigments behave the same under sunlight and rain. Here’s what drives performance:
1. Pigment Chemistry
- High performers: Phthalocyanines (e.g., Pigment Blue 15:3, Green 7), DPP (diketopyrrolopyrrole), and quinacridones owe their stability to aromatic rings and high molecular weight.
- Lower performers: Monoazo lake pigments (e.g., some yellows/reds) degrade faster due to weaker chromophores.
2. Dispersion Quality
- Poorly dispersed pigments form agglomerates, creating high-local-concentration zones that accelerate photo-oxidation.
- Uniform dispersion = larger surface area protected by resin + additives.
3. Environmental Stressors
- UV light is the primary culprit—shorter wavelengths (290–400 nm) break C=C and C-N bonds.
- Synergistic degradation: High humidity + oxygen + heat speeds up hydrolysis and chain scission.
- Pollutants: Acid rain, salt spray (coastal), and industrial SO₂/NOₓ attack pigment particles.
4. Polymer Matrix & Additives
- Resin matters: Polyester and acrylic resins > polyolefins (PE/PP) in UV transparency and stability.
- Stabilizer packages: UV absorbers (e.g., benzotriazoles), HALS (hindered amine light stabilizers), and antioxidants extend pigment life by 2–3 grades in some cases.
Weather Resistance Ratings: Real-World Brand Examples
| Brand | Product Example | Lightfastness (1/3 SD) | Weatherfastness | Key Applications |
|---|---|---|---|---|
| Clariant | PV Fast Yellow HGR (PY 191) | 7–8 | 5 | Engineering plastics, masterbatches |
| Clariant | Graphtol Red F3RK70 | 8 | High (implied 7–8) | High-heat polyamides |
| BASF | Paliogen® / Sicopal® series | 8 | 7–8 | Automotive exteriors |
| Lanxess | Colortherm® / Macrolex® | 7–8 | 7–8 | High-performance engineering polymers |
| Sudarshan | Sudafast / Sudacolor series | 7–8 | 6–8 | Outdoor profiles, toys |
| Guangdong CDJ | R-66R (inorganic red) | 7–8 | 8 | Long-term outdoor (8+ years) |
SD = Standard Depth; higher values at 1/25 SD indicate excellent tinting strength retention.
Application Guide by Weatherfastness Grade
| Grade | Durability | Typical Lifespan (Outdoor) | Recommended Uses |
|---|---|---|---|
| 1–3 | Poor | < 1 year | Indoor disposables, short-term displays |
| 4–5 | Moderate | 1–3 years | Indoor appliances, shaded outdoor furniture |
| 6–7 | Good | 3–7 years | Automotive interiors, garden toys, signage |
| 8 | Excellent | 7–15+ years | Car exteriors, window profiles, marine parts |
Pro Tip: Even Grade 8 pigments fade eventually in equatorial climates. Combine with 2–3% HALS + 0.5% UV absorber for maximum longevity.
Top Recommended Brands for High-Weatherability Pigments
1. Clariant (PV Fast & Graphtol Series)
- Industry gold standard for organic pigments.
- Exceptional color strength and heat stability (up to 300°C).
- Widely validated in polyolefins, PVC, and engineering resins.
2. BASF (Sicopal®, Heliogen®, Paliogen®)
- Leaders in automotive-grade pigments.
- Inorganic/organic hybrids offer 8/8 lightfastness in reduced shades.
- Compliant with OEM specifications (VW, BMW, GM).
3. Lanxess (Macrolex®, Colortherm®)
- Strong in high-temperature applications (PA, PC, PBT).
- Inorganic oxides (e.g., iron oxides, chromium greens) hit Grade 8 consistently.
4. Sudarshan Chemical Industries
- Cost-effective Grade 7–8 alternatives to European brands.
- Growing presence in Asia-Pacific outdoor markets.
How to Test & Specify Weather Resistance
- Accelerated Testing:
- Xenon Arc (ISO 4892-2): Simulates full-spectrum sunlight.
- QUV (ASTM G154): UVA-340 lamps for budget screening.
- Target: ΔE < 2.0 after 2,000 hours for Grade 7–8.
- Real-World Correlation:
- Florida exposure (5° south, high UV/humidity) ≈ 1 year = 1000 kLy (kilo-Langley).
- Grade 8 pigments typically survive 8–12 Florida years before noticeable fade.
- Specification Checklist:
- Request 1/3 and 1/25 SD data.
- Confirm migration resistance in flexible PVC.
- Verify heavy metal compliance (EN 71-3, FDA).
Final Thoughts: Future-Proof Your Colors
Weather resistance isn’t just a number—it’s insurance against customer complaints, warranty claims, and brand damage. By selecting Grade 7–8 pigments from proven suppliers like Clariant, BASF, or Lanxess, and pairing them with optimized dispersion and stabilization, you can achieve decade-long color stability even in harsh climates.
Ready to upgrade your masterbatch? Contact suppliers for Xenon-tested certificates and custom shade matching—because in outdoor plastics, fading is not an option.
Sources: Clariant PV Fast Technical Datasheets, BASF Plastics Additives Brochure, Lanxess Colorant Guide, ISO 4892-2, industry exposure correlations.
