Determination of optical properties of pigments applied to plastics based on the Monte Carlo method

The characteristics of the pigments and the composition of the formulation have a decisive influence on the appearance of coloured plastics, mainly in terms of their reflectance and transmittance. This research presented a novel analytical approach to quantify the optical properties of pigments and predict the appearance of plastics containing these pigments accordingly. Firstly, the Monte Carlo method was employed to characterise the measurement geometry of the spectrophotometer and the light transfer in coloured plastics. Based on this, the paper proposed a method for determining the absorption coefficients and scattering coefficients of the substrate and the pigments according to reflectance and transmittance measurements. To verify the efficacy of the approach, 25 polyethylene‐based samples were prepared. The samples 1–15 were used to determine the optical properties of the respective pigments, and the samples 16–25 to test the predictive capabilities of the model. The result showed that the method can reliably predict the reflectance, transmittance and colour of plastic formulations.