Distinguish between PA6 and PA66 in seconds

PA6 and PA66 are among the most widely used plastics in the world. However, a simple differentiation is tricky and only possible with (time-consuming) laboratory work. There is often not enough time for these tests, especially in the incoming goods department. Near-infrared technology closes the gap and helps to separate the two plastics.

No forwarding agent waiting

A familiar situation at many plastic silos around the world: the articulated lorry with the delivery drives onto the company premises and is to be unloaded immediately.

As PA6 and PA66 hardly differ chemically, it is not possible to carry out a simple burn test directly on site. However, processing in the laboratory requires a considerable amount of time and money.

PA6 & PA66: How to differentiate?

In this article, I will show you how to differentiate quickly and reliably using NIR. The following image shows the NIR spectra of two samples: PA6 and PA66 - taken directly from the silo. The human eye cannot detect any relevant differences here:

Send in your own samples!

The raw spectra of PA6 and PA66 are very similar. Differences can hardly be detected.

Differential display shows clear differences in the NIR spectrum

The difference display also does not appear as clear as desired at first glance. However, there are clear differences between the samples at the wavelengths 1,190 nm, 1,220 nm, 1,375 nm, 1,400 nm and 1,620 nm:

The spectra of PA6 and PA66 differ significantly at several wavelengths.

3D cluster display clearly groups large numbers of NIR spectra

What is only hinted at in the difference display is clearly shown in the 3D cluster display: the material of the PA6 sample appears to be more homogeneous: The spectra of the individual measurements hardly differ, recognizable by the spatial proximity of the spectra in the 3D cluster display.

The PA6 spectra vary less than the PA66 spectra. An indication of inhomogeneous sample material.

Own references: Learn quickly

For this application, it makes sense to teach in the actual samples as separate references. The folder with the already saved and named spectra is stored as a reference database and automatic identification is activated.

For the counter sample, only the samples are held in front of the scanner: first 5x the PA66 sample and then 5x the PA6 sample. All samples are recognized correctly. In the user interface, the recognized substances are marked with an (*) in front of the material name.

I now store this data as my own references for future measurements. A workstation equipped with a solid scanner and this reference data now enables even non-experts to check the silo delivery quickly, reliably and therefore very easily.

The automatic identification algorithm recognizes PA6 correctly. Previously, PA66 and PA6 had already been recognized correctly several times.

Absolute reference data: NIR spectra from the reference database

The Basis reference database also helps with identification:

PA6-PA66_Rohspekten_Gegenpruefung.-mit-ReferenzdatenbankJPG

In this example, the Basis reference database with absolute references is used. This reference database makes it possible to determine unknown materials without having to teach them in beforehand.

Configuration

You need the following (minimum) configuration for this sample application:

Hardware

Solid Scanner - portable NIR spectrometer

Software

NIR reference spectra

Reference database “Basis” for plastics (for the determination of unknown plastics)

Curious? Request a quote for a portable NIR spectrometer

If I have aroused your curiosity and you would like more information or a concrete offer, just write to us.

We would be happy to discuss with you how the hand scanner can simplify and speed up your processes.

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