Pigments for Plastics
Copper phthalocyanine blues and greens are the workhorses for blue and green coloration across the entire plastics industry, valued for their exceptional heat stability, chemical inertness, and total resistance to migration. Unlike many organic pigments that sublime or bleed at polymer processing temperatures, CPC pigments remain locked in the polymer matrix from extrusion through end-use, satisfying the strict migration and extraction limits of food-contact, toy safety, and medical-device regulations. PB 15:3 handles the vast majority of commodity-resin applications — PVC, polyolefins, and polystyrene — while PB 15:4 is the grade of choice for engineering resins such as PA, PC, and PBT that require processing above 280 °C. PG 7, with its fully chlorinated ring, routinely withstands 300 °C and above, making it the only viable single-pigment green for polycarbonate and high-temperature nylon compounds.
Key Performance Requirements
Heat stability
Polymer processing temperatures range from around 160 °C for PVC up to 330 °C for polycarbonate and high-temperature nylons, with residence times from seconds in injection moulding to minutes in extrusion. The pigment must survive these conditions without shade change, strength loss, or decomposition. Beta-form CPC blues are stable to approximately 300 °C; PG 7 exceeds 300 °C, making crystal form and stabilisation treatment the key selection criteria.
Migration resistance
In plastics, migration means the movement of colourant molecules from the coloured article into adjacent materials, food, or skin. CPC pigments are fully insoluble in all common polymer matrices and plasticisers, giving them a clean pass on extraction tests under EN 71-3, FDA 21 CFR, and EU 10/2011 food-contact regulations. This zero-migration behaviour is a fundamental advantage over soluble dyes and many azo pigments.
Dispersion in polymer melt
Achieving uniform pigment dispersion in a viscous polymer melt requires that the pigment wets out and breaks down to primary particle size under the shear and temperature conditions of the compounding equipment — typically a twin-screw extruder or internal mixer. Poor dispersion leads to specks, colour streaks, and reduced mechanical properties in the finished part. Particle size distribution, surface treatment, and pigment form (powder vs. pre-dispersed) all affect dispersion quality.
Regulatory compliance
Plastics for food contact, toys, medical devices, and childcare articles must comply with a complex web of regional regulations including EU 10/2011, FDA 21 CFR 178.3297, EN 71-3, and REACH SVHC screening. Each production batch of pigment should be accompanied by a certificate of analysis confirming heavy-metal content below the applicable thresholds and the absence of listed substances. CPC pigments are broadly positive-listed, but ongoing compliance verification is a non-negotiable requirement.
Recommended Grades
| Grade | Shade | Rationale |
|---|---|---|
| PB 15:3 | Greenish blue | The default blue pigment for commodity plastics including HDPE, LDPE, PP, PS, and ABS. Its beta crystal form offers a clean greenish-blue shade, high strength, and heat stability sufficient for the processing temperatures of these resins (typically up to 280 °C). Cost-effectiveness and broad availability make it the volume leader in the plastics segment. |
| PB 15:4 | Greenish blue | Non-flocculating beta-form blue selected for engineering resins — polycarbonate, polyamide, PBT, and POM — where processing temperatures exceed 280 °C and high injection pressures demand perfect dispersion. Its stabilised surface treatment also prevents warpage-inducing nucleation in polypropylene, a critical requirement for thin-wall moulding. |
| PB 15:0 | Reddish blue | Untreated alpha-form blue with a reddish shade, suitable for PVC and LDPE applications where processing temperatures remain below 220 °C. Its lower cost and warm hue make it the preferred choice for flexible PVC products such as cables, flooring, and garden hose where a red-shade blue is specified. |
| PG 7 | Bluish green | The only single-pigment green capable of withstanding processing temperatures above 300 °C, making it mandatory for polycarbonate, high-temperature nylon, and PBT compounds. Its total chemical inertness and zero migration also make it the default green for food-contact and toy-safety applications across all resin types. |
Technical Considerations
- In polypropylene, certain CPC blue pigments — particularly fine-particle or untreated grades — can act as nucleating agents, accelerating crystallisation and causing differential shrinkage that manifests as warpage in injection-moulded parts. PB 15:4 with its larger, surface-treated particles has a significantly reduced nucleation effect and is the recommended grade for PP applications where dimensional stability is critical.
- PVC compounds contain heat stabilisers (calcium-zinc, barium-zinc, or organotin systems) and plasticisers (phthalate, adipate, or polymeric types) that can interact with the pigment surface. CPC pigments are chemically inert to these additives, but the pigment's surface treatment must be compatible with the stabiliser system to avoid discolouration during processing. Pre-testing in the customer's specific formulation is always recommended.
- Masterbatch production requires pigments with controlled particle size distribution and good wetting behaviour to achieve high pigment loading (30–60 %) in the carrier resin without excessive torque or die-lip build-up. Pre-dispersed or specifically treated CPC grades designed for masterbatch use reduce let-down ratio requirements and improve colour consistency in the final article.
- For toys and childcare articles, EN 71-3:2019 specifies extraction limits for 19 elements in three categories of toy material. CPC pigments routinely pass Category III (scraped-off material) limits, but each production batch must be verified against the standard because trace-metal content can vary with raw-material sourcing. Certificates of analysis referencing EN 71-3 should accompany every shipment.
Need help selecting the right grade?
Tell us about your application and we'll recommend the optimal pigment grade for your formulation.
Contact Us