PIGMENTS | SPECIAL EFFECT
Right: Colloids says its “aged glass” effect masterbatches provide an upcycling
option for PET
round shape does not show dark edges and as a result eliminates undesirable streaks and surface defects, he says. The effect’s brilliance is at its most pronounced
in transparent thermoplastics, but the new prod- ucts are also suitable for opaque plastics. They can be used in a wide range of applications, including automotive interior and exterior parts; office electronics such as keyboards and laptop housings; large and small kitchen devices; and household items and toys. Special effect pigment producers are also likely to benefit from the trend to more easily recycled parts —plastics with metallic colours are more easily recycled than plastics that use metallized chrome or lacquer surface layers. Another sustainable effect from Tosaf employs
natural fibres (such as grass fibres, for example) to achieve a natural effect that portrays ecological and sustainable behavior, says Kruschinski. This type of effect is in demand for a number of applica- tions, particularly toys, cooking equipment, and household appliances. It is best suited for the processing temperature range of polyolefins.
IMAGE: COLLOIDS
Considering aesthetics As the use of recycled plastic feedstocks grows, their aesthetics have to be considered, according to Graham Cotton, Head of Sustainable Product Innovations at Colloids. “Virgin PET is almost colourless, and when used in packaging it allows the colour of the articles to be seen by the consum- er as brands intended it. When PET is recycled, the colour of the polymer changes and is greyer; when
Tips for creating striking effects
Special effect pigments—including pearlescents, metallics, glitters and fluorescents—add an additional dimension to the colour of plastic products, says Graham Cotton, Head of Sustainable Product Innovations at masterbatch and compound producer Colloids. But he advises there are considerations to make. “Effect pigments create the best aesthetics in transparent and semi- transparent polymers where light reflectance occurs not only on the surface but further below the surface. For example, ABS is an opaque polymer and, whilst it is possible to create a great effect, the concentration of effect pigment is twice that what would be required from using SAN or
MABS. It’s a balancing act between commercial costs, physical properties and aesthetic values,” he says. Processing conditions in master-
batch production and part conversion should also be considered. Cotton says that aluminium flakes and pearlescents can be damaged by processing shear. He says it is important to “match the melt viscosity of the masterbatch carrier to the host polymer to maximise the distribution whilst limiting flow lines” and to carefully select extrusion screw profiles with low shear. “Damaging these extremely thin
flakes, with shear in the process, can reduce their reflectance, resulting in higher addition rates to offset the damage. Or, more critically, [damage]
can interfere with the base colour, in particular with aluminium flakes and gold pearlescents, such as making the colour appear darker and greyer or redder and brownish respectively,” Cotton says. The base colour of the part also
plays a role. “It is important to avoid using opaque colourants such as titanium dioxide, which can mask the effect pigment,” he says. “Interference pearlescents can give a wide colour play when using a contrasting base colour. It is also possible to discretely use pearlescent pigments to enhance a base colour, making it appear brighter and more lively, especially using a gold pigment in green base colour.” �
www.colloids.com
Above: Careful consideration is key in achieving the most successful special effect solutions 52 COMPOUNDING WORLD | March 2022
IMAGE: COLLOIDS
www.compoundingworld.com
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