MATERIALS | COLOURS
making coloured rPVC compounds, the company recommends separating the recyclate by colour and making a specific masterbatch for each colour. Mixed, unsorted streams are usually coloured with carbon black.
Colour measurement Measuring colour is crucial for processors trying to manage the variability in colour of recycled content while maintaining colour standards and controlling costs. “Colours can shift unexpectedly when pigments
are added to such unpredictable substrates, leading to higher scrap and rework rates, longer development and production cycles, increased use of colorants to compensate for base variability, greater complexity in quality control and formula- tion, and potential product non-conformance or customer complaints,” said Jutta Albertin, Project Manager at Datacolor. “All these issues translate directly into higher costs and operational risks. Companies need robust colour measurement and formulation tools, tighter process controls and more flexible production strategies to mitigate the impacts of recycled content variability. Only then
can they achieve both their sustainability objectives and colour quality standards without one under- mining the other.” Albertin suggested multiple ways to handle PCR in formulating colour. One method is to create a colorant set of several typical PCR materials by producing at least two calibration samples of each PCR type to calculate the optical data of the material. This PCR can then be used like a virgin polymer in the colour formulation. “Each time you get a new batch of recycled material, search for the closest match in colour and opacity. You can then compensate for the difference between the new material and the closest match by performing one or two additional correction steps using software with a correction algorithm,” she explained. Another method is to recolour the PCR as if
recolouring leftover material; this works for opaque PCR that requires only one measurement point and that is not too far from the target colour, Albertin said.
Albertin suggested that a good first step when considering whether PCR can be used to achieve a target colour is to use a software tool to determine possible recipes in the colour space. Datacolor’s
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