New Ampacet masterbatches improve NIR sorting of black plastics

March 20, 2023
Products avoid the challenges carbon black brings to recycling lines using near-infrared optical sorters.

From the Spring 2023 issue of Plastics Recycling.

By Bruce Geiselman

Ampacet Corp., specializing in color and additive masterbatches, is taking more steps to increase the recyclability of black plastics.

The first development is the introduction of a new black coloring agent that is compatible with near-infrared optical sorters used to separate PE plastics at recycling facilities.

To recycle plastic packaging into usable resins, plastic waste is presorted by resin type at recovery facilities. Plastic, to maintain its properties, must be sorted into separate mono-material streams, such as PE, PET, polypropylene and polystyrene.

Presorting is typically done with near-infrared (NIR) optical sorters. However, NIR optical sorting typically cannot identify and separate plastics that contain carbon black, the most commonly used black pigment. Carbon black absorbs a significant part of the ultraviolet and infrared spectrum, preventing the reflection of infrared light back to the sensor. That blocks the sorting equipment from recognizing the resin’s fingerprint via NIR scan. As a result, most black plastics are either landfilled or incinerated.

Ampacet, based in Tarrytown, New York, recently announced the addition of Rec-NIR-Black PE 512 to its carbon-free Rec-NIR-Black masterbatch range. The new additive is NIR-detectable while providing a high level of opacity for use with polyethylene material in flexible applications, such as flexible packaging, according to the company.

However, Rec-NIR-Black PE 512 is only suitable for indoor use because, unlike conventional carbon black masterbatches, it does not provide a stabilizing effect against UV degradation.

In the second development, Ampacet and Pellenc ST, a company based in France that develops and sells sensor-based sorting equipment, have partnered on studies to optimize the recyclability of both black and clear PET packaging on sorting lines that employ near-infrared sorting technology.

The mechanical and optical characteristics of recycled clear PET flakes obtained from recycling transparent flow are generally close to virgin resin, according to the companies. Clear rPET flakes are used in a variety of high-value applications including water bottles and food containers.

However, optical scanners used at material recycling facilities have difficulties identifying transparent from dark plastics. The reason for the difficulty has to do with clear plastics being placed on black conveyor belts. The visible domain spectrometers installed above the conveyor belts have difficulty distinguishing dark containers from transparent ones on the black belts.

Sorting tests carried out by Pellenc ST on PET containers colored with Ampacet Rec-NIR-Black products allowed Pellenc ST to establish the optimal conditions and discover how parameters can be adjusted in the computer algorithm to accurately differentiate transparent packaging items from dark ones and direct them to the correct streams.

“Pellenc ST is happy to contribute to the validation of detectable black dyes to be used in plastic packaging,” Antoine Bourely, chief scientific officer, Pellenc ST wrote to Plastics Recycling in an email. “With the Ampacet dye, we can not only detect the material, but also tell the difference between black and transparent plastics, even on a black background.”

Tests were carried out using Pellenc ST’s new Mistral+ Connect optical sorter and previous versions of the machine, according to a statement from the companies.

“Pellenc ST and Ampacet collaboration on sorting studies allowed us to optimize the recyclability of dark PET packaging on existing recycling lines,” said Philippe Hugelé, Ampacet’s strategic business manager rigid packaging.  

“Ampacet’s wide range of innovative masterbatch solutions supports customers in achieving their sustainability objectives and voluntary commitments through improved product designs for the circular economy, optimized content of post-consumer recycled material, reduction of fossil-based raw material consumption and adoption of alternative end-of-life scenarios. The Ampacet Rec-NIR-Black range contributes to the circular economy initiatives,” he added in a statement provided to Plastics Recycling.

Bruce Geiselman, senior staff reporter

[email protected]   


Ampacet Corp., Tarrytown, N.Y., 914-631-6600, 

Pellenc ST America Inc., Charlotte, N.C., 803-396-3990,

About the Author

Bruce Geiselman | Senior Staff Reporter

Senior Staff Reporter Bruce Geiselman covers extrusion, blow molding, additive manufacturing, automation and end markets including automotive and packaging. He also writes features, including In Other Words and Problem Solved, for Plastics Machinery & Manufacturing, Plastics Recycling and The Journal of Blow Molding. He has extensive experience in daily and magazine journalism.