Experience, expertise, and equipment: GRAFE is an expert in colouring translucent plastics

Decades of experience, the highest level of technical expertise, and state-of-the-art technical equipment – these are the three pillars on which the comprehensive competence of the GRAFE GROUP, Blankenhain, in the colouring of transparent technical plastics rests. Compounds are predominantly used, with masterbatch only being used in special cases. “The demands on dispersion and homogenisation are much higher for transparent materials than for opaque colourings,” explains Sales Manager Lars Tonnecker. “Thus, in product manufacturing, a compound is the better and cleaner solution compared to a masterbatch. This is because error patterns on the component, such as uneven colour distribution, streaks, and differences in concentration, can be avoided or eliminated, as there is no need for additional dosing of the masterbatch at the plant.”

“Whether headlights, rear lights, or displays – mostly the coloured transparent plastics are used in lighting applications. For this, there are precisely defined wavelength ranges from the manufacturers that must be adhered to, and no deviations are acceptable,” adds project manager Elke Milus. “We can adjust our compounds so that each batch matches the other, with minimal tolerances, with the greatest reproducibility and thus the best quality.” This is ensured by an exceptional production control and quality assurance process developed by GRAFE itself, which ensures the highest level of repeatability in recurring process steps.

Tonnecker also points to the high availability of the right raw materials and the comprehensive production know-how at GRAFE: “Not only do we have a large selection of colourants and additives for transparent polymers, but also a huge stock of existing formulations that we can draw on. This enables us to make the appropriate adjustments very quickly.”

GRAFE has also recently made extensive investments in its laboratory equipment and now has, among other things, a high-resolution spectrophotometer for measuring transmission in different wavelength ranges (UV/VIS/NIR = ultraviolet / visible / near infrared). Thus, thanks to its higher optical resolution in an extended wavelength range of 350 to 1,050 nanometres, the device even measures in five-nanometre steps instead of the usual ten-nanometre steps and is thus much more precise. “To evaluate the colours, you don’t measure the reflection, i.e. what is absorbed, but the transmission, what passes through,” explained Milus.

“With the device, we also cover the UV and infrared range. Some customers, for example, want thermal radiation to pass through the transparent component as well. We can check that with this device,” she reports. “Most customers don’t have these measuring devices. We therefore offer to support them with these measurements and thus drive corresponding development projects forward,” Tonnecker adds. In doing so, she says, GRAFE is able to measure even large components and produce test specimens with wall thicknesses of one to four millimetres itself.

“A current trend is that transparent components are backlit with LEDs and the demand for corresponding covers and laminations is increasing. We can simulate the different properties of the LEDs – more precisely, their colour temperatures – with our special laboratory equipment and thus measure the colour perception in order to readjust if necessary,” Milus explains.

Finally, the sales manager also reports on a separate team in the company that is only responsible for transparent polymers: “This is a separately organised project group in the field of lighting technology that has special extruders and injection moulding machines for producing the test specimens. This is the prerequisite for clean work and for our speed in setting the materials,” he affirms and emphasises GRAFE’s experience in processing transparent plastics, which has grown over more than 20 years.