Plastic Colouring: How to Select Colourants and Maximise Pigment Performance
Plastic colouring is a complex technical process, even though coloured plastic products are part of everyday life. Achieving the desired colour requires careful decision-making, starting with the correct selection of the colourant. This choice directly affects appearance, performance, cost and long-term durability of the final product.
In industrial practice, these decisions are increasingly taken with a focus on efficiency, robustness and cost control. Through its applied R&D and industrial support activities, AIMPLAS works with companies to analyse colouring challenges at formulation and process level, helping to translate colour requirements into technically and economically viable solutions.
Key factors in colourant selection
Colourant selection mainly depends on two major aspects: the characteristics of the plastic to be coloured and the requirements of the final application. Both factors must be evaluated together, as the same colourant may perform very differently depending on the polymer type and service conditions.
Polymer properties and formulation effects
From the polymer perspective, several properties must be considered, including melt flow rate, transparency, crystalline or amorphous structure, surface finish and processing temperature. The presence of fillers, fibres or other additives in the formulation also has a significant influence on colour development and dispersion behaviour.
Types of colourants used in plastics
Colourants used in plastics are generally classified as dyes or pigments. Dyes are fully soluble in polymers and are typically used for transparent plastics, especially amorphous materials. Pigments, on the other hand, can be organic or inorganic and are either partially soluble or completely insoluble.
Organic pigments provide high colouring strength and bright, glossy colours at low dosages, but they tend to migrate more easily. Inorganic pigments offer high opacity and excellent stability, making them suitable for demanding applications, although they usually require higher loadings to achieve the same colour intensity.
Application requirements and fastness performance
Final application requirements play a key role in colourant selection. Factors such as durability, cost, exposure to UV radiation, temperature, chemicals and potential colour migration must be considered. These aspects are commonly evaluated through different fastness properties and validated through testing.
Fastness refers to a colour’s resistance to external factors such as light, heat, chemicals and migration within the plastic. Ensuring adequate fastness is essential to guarantee colour stability during processing and throughout the product’s service life, especially in technically demanding applications.
Masterbatches and industrial optimisation
In industrial practice, colourants are often supplied as masterbatches, where pigments or dyes are pre-dispersed in a polymer carrier. Through its compounding and pilot-scale facilities, AIMPLAS supports companies in optimising masterbatch formulation and dispersion, helping to improve colour consistency, process stability and industrial reproducibility.
Pigment yield and dispersion efficiency
In addition to colourant type, pigment yield is a critical concept in plastic colouring. Pigment yield describes how efficiently a pigment provides colour intensity relative to the amount used. Improving pigment yield allows companies to reduce dosage levels while maintaining visual performance.
Pigment yield is closely linked to dispersion quality within the polymer matrix. Good dispersion increases the effective coloured volume and depends on particle size, polymer viscosity, processing conditions and chemical compatibility. At AIMPLAS, dispersion analysis and process optimisation are key tools to identify improvement opportunities in existing formulations.
Improving dispersion often requires optimising compounding parameters, screw design, processing conditions or the use of dispersing agents. These improvements can lead to higher pigment yield, reduced colourant consumption and lower production costs, directly contributing to improved competitiveness and profitability for plastic manufacturers.