Press Releases Sensor Instruments

There are already a number of systems for separating and sorting plastic waste according to color and plastic type. In addition, image processing systems, paired with artificial intelligence (AI), provide good services in the recognition of shapes or in the search for applied barcodes or QR codes and so-called digital watermarks when separating plastic packaging. But what happens in the further course of the recycling process after washing and shredding the pre-sorted material? Especially if they are fragments or flakes of the same color and the same type of plastic?
A printed code or digital watermark can then no longer be used, which means that it is no longer possible to differentiate between food and non-food, for example. After regranulation, the recyclate can no longer be used to determine the area in which the source material was used.
In order to be able to check the section in the recycling process immediately before and after the recyclate is extruded, a permanent, processing-resistant and temperature-resistant marking or coding must be applied to the plastic matrix. This makes it possible to close the gap in material monitoring, particularly with regard to identity, origin and quality. The marking typically consists of phosphorescent, inorganic microparticles. Due to their inert properties and size,
they can be incorporated into almost all plastic products. Marker-based masterbatches from Gabriel-Chemie are now available under the brand name TAGTEC (Taggant Technology). (...)

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The use of more and more recyclates in the plastic processing industry, driven not least by the EU Packaging and Packaging Waste Regulation (PPWR) with regard to the proportion of recyclates in plastics, also increases the need to carry out a check according to the type of plastic of the respective recyclate in addition to the color check already carried out in the laboratory. There is no lack of adequate sensor technology during the sorting and separating process, as various machine builders offer sorting systems equipped with so-called hyperspectral cameras suitable for the NIR range. These are suitable for sorting whole objects as well as for separating plastic fragments and flakes. However, for economic reasons these NIR cameras are less suitable for more selective product monitoring. Discrete sensors and sensor systems, which are both very compact in design and inexpensive to purchase, are more appropriate for this purpose.
In addition to stationary laboratory devices SPECTRO-T-3-0°/45°-LAB-LF and SPECTRO-T-3-DIF/0°-LAB-LF, mobile laboratory systems SPECTRO-T-3-0°/45°-MOBILE-P and SPECTRO-T-3-DIF/0°-MOBILE-P are also available. To avoid sending the measuring systems in for regular recalibration, on-site calibration has been integrated into the devices. (...)

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Soot-blackened plastic, like a black hole that devours all light? Not quite! Although a large proportion of the light hitting the black plastic material is absorbed in the visible and near infrared range (NIR), the absorption behavior of Carbon Black products in the mid infrared range (MIR) is rather low compared to light-colored materials. In the MIR range, therefore, a window opens that provides an insight into the type of plastic used. Different Carbon Black plastics have a characteristic spectral absorption behavior in the MIR range, which makes it possible to differentiate between different types of plastic in this wavelength range.
Up to now, black plastic has tended to be downcycled, at least in open cycles, i.e. the recycled material is no longer intended for its original use but is instead used for lesser purposes.
In view of the fact that around 1/6 of the plastic material produced each year currently consists of carbon black, there is an increasing need for action to return the recycled material to its original area of application. In the automotive industry in particular, but also in the electronics and construction industries, soot-blackened plastic is predominantly used.
At present, however, the range of sorting and separation systems for separating Carbon Black by type of plastic is still limited. This is probably preliminary due to the fact that hyper¬spectral cameras suitable for the MIR range are still quite expensive and require intensive servicing. Together with partner companies, Sensor Instruments is taking an alternative approach here; the three-range method known from the visible wavelength range has been transferred to the MIR range. L*a*b* became M*i*r* and instead of measuring in the visible range (400nm to 700nm), measurements are taken in the mid-infrared range between 2.5µm and 5.0µm. (...)

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Why should the color of recyclates also be measured?
A lot of effort is already put into separating the color of the objects to be recycled. The color separation of whole plastic objects is followed by a further color separation of the flakes or plastic fragments after shredding and the subsequent washing and drying process.
However, due to the changes in the EU Packaging and Packaging Waste Regulation (PPWR) regarding the proportion of recycled material in plastics (for example, from 2025, at least 25% of disposable PET beverage bottles must contain recycled plastic (recyclate) and from 2030 at least 30%), the quality require¬ments for the recyclate to be produced is increasing.
The plastics processing industry places the same quality demands on the recyclate as it does on virgin material, and the color of the recyclate is one of these quality demands. Although random recyclate color measurements are carried out in the laboratory at recycling companies, in most cases, the color of the recyclate is not monitored at the production facilities.
This is certainly also due to the fact that fewer recyclates have been used in new plastic products to date and also to the lack of suppliers of such inline recyclate color measurement systems, but measuring systems are now also available for this field of application. Sensor Instruments took care not only to develop an inline color measurement system, but also include the items required for on-site calibration in its product range. (...)

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How can the thickness of a coating layer between two PET films actually be determined?
For this purpose, four PET film pairs with different pint layer thicknesses between the two PET films (10µm, 20µm, 50µm and 80µm) were examined using the MIR transmitted light method. On the receiver side, two wavelength ranges with center wavelengths of 2.95µm and 3.90µm (SPECTRO-M-2-2.95/3.90) were available. The distance to the MIR transmitter (SPECTRO-M-15-T) was approximately 20mm.
The presence of a silicone layer on a transparent plastic film was also investigated using this measurement method, with the result that this layer can also be detected quite well.

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Measurement of the lowest spray quantities in the Ex area
For applications with extremely low spray application, it is advisable to use a solution based on the reflected light principle. Many of these applications also take place in hazardous areas, which makes a fiber optic solution to the preferred choice. The respective spray jet is usually no longer visible to the naked eye. 
Using the ABL-V-ARRA-KL-M18-XL-A3.0 fiber optic frontend in conjunction with the SPECTRO-T-1-FIO-R/R control electronics, both the presence and the spray jet density can be reliably determined from a distance of typ. 60 mm between the front end and the spray jet.

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The Windows® Software SPECTRO3 MSM DOCAL Scope facilitates inline calibration of the color sensor system in different ways, which are explained below in further detail.

Calibration with RAL plastic color cards

The nonprofit organization RAL gGmbH, Bonn offers a collection of 300 different colored plastic cards calibrated according to the d/8° method. The corresponding L*a*b*-values are noted on every sleeve that is enclosed with the plastic color card.

In addition, for the RAL plastic color cards, which can be obtained from Sensor Instruments GmbH, the respective L*a*b*-value, which is obtained from the 45°/0° measurement, is noted on both the RAL plastic color card as well as on the sleeve and in addition, assigned a 5-digit number. Sensor Instruments assigns and enters successive 5-digit numbers for new RAL plastic color cards to be calibrated, along with the L*a*b* color value that is calibrated on the RAL plastic color card, to a calibration file. Thus, during the calibration process, the sensor system only has to be presented the RAL plastic color cards to be calibrated and the matching 5-digit number input in the software. With this calibration mode, reference is made solely to the RAL plastic color cards, as a result of which a location-independent comparison of the measurement results is made possible, for example, for companies with several locations, since in such a case, manual color measuring instruments, the so-called manual colorimeters, can be dispensed with.

Calibration using injection molded color platelets and recyclates

But very often, it is exactly this relation to the manual or laboratory colorimeters already present in the facility that is desired, since it then becomes possible to better compare the measurement values between production and laboratory. This referencing to colorimeters that are already available in the facility through the SPECTRO3 MSM DOCAL Scope software is described in some more detail below. To do this, apart from the inline color measurement systems, Sensor Instruments also supplies laboratory equipment that work according to exactly the same process and whose sensor systems are identical. The systems that are available are both those that measure through an inspection glass as well as those which directly view the recyclate itself, of which measurements are to be taken.

Inline colorimetry using the
SPECTRO-3-0°/45°-MSM-INLINE-ANA
and the matching laboratory equipment
SPECTRO-3-0°/45°-MSM-CMU

In both cases, calibration can be done directly with reference to the recyclate, while the L*a*b* reference values are determined using injection molded platelets, made from the same batch of the recyclate that is available to the devices to be calibrated. The L*a*b* reference values are determined using the injection molded platelets by means of the manual or laboratory colorimeters available in the respective facility.

Inline colorimetry using a
SPECTRO-3-FIO-MSM-ANA-DL
in conjunction with a frontend
KL-D-0°/45°-85-1200-D-S-A3.0-VIS
and the matching SPECTRO-3-0°/45°-MST
laboratory device

Here too, the injection molded platelets provide the L*a*b* reference values. The optical frontend is pointed directly at the recyclate at a distance of 85 mm. The recyclate that is available during the calibration is also used for making the injection molded platelets. Thus, the injection molded platelets and the recyclate originate from the same batch.

When calibrating using a SPECTRO-3-0°/45°-MST laboratory device, it is recommended that when recording the measurement value during the calibration process, the recyclate holding bowl should be moved in the x and y directions with the distance to the front end of the sensor being constant, so that the random position of the pellets can be compensated. Inline, this is done by transporting the pellets on a jolting conveyor. Here, the recyclate flow assumes a speed of typically 50mm/s to 100mm/s. During a calibration process with a duration of 30s, for example, the recyclate stream moves through 1.5m to 3m, i.e. an average is calculated across this measurement path during the calibration process. The measurement result is then correspondingly accurate and independent of the random position of the granulate grains. Even with vibrations that set the pellets in resonance and then cause them to "bounce", this can achieve significant compensation during the measurement process with a duration of a few seconds. What is decisive here is the large light spot size of approximately 20 mm diameter, as a result of which, even at standstill, optical averaging takes place across a large number of pellets.

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The increasing use of recyclates in the plastics industry means that efficient product control is assuming ever-greater importance. Whilst laboratory-based random quality control was sufficient in the past, the industry is increasingly considering the deployment of 100% control, especially in terms of the color gradient. Sensor Instruments has launched a number of inline systems to perform this function. Providing production staff with information about recyclate production at a very early stage, this covers not only the trend in the color of the recyclates, but the color of the recyclates in combination with their temperature, whilst monitoring the product flow level. The product flow level is important for exact determination of the recyclate color, whilst also providing timely information about a possible blockage of the sieve immediately after the vibrating feeder. The data is also made available for quality assurance via a digital-serial interface (Ethernet).

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While downcycling of plastic products still predominated in the past, the form of recycling in which the reused plastic is put to the same or a comparable use is now becoming increasingly important. This in turn means considerable additional technical effort in separating and sorting the items delivered to the recycling plant throughout the recycling process. After separation of as many non-plastics as possible, for example by means of metal separators and wind separation, sorting is currently primarily by color (color sorting systems) and type of plastic (NIR cameras). Despite pre-sorting, where mainly whole articles are checked, as well as post-sorting (after shredding the plastic articles and subsequent washing) of the plastic particles known as flakes, it is not possible to achieve 100% grade purity. Certain variations in color must also be expected. In order to allow unrestricted use of the recyclates produced in this way, they must be checked for purity before the next processing step, at the very latest immediately before extrusion. Typically, this could be done by a metering system equipped with appropriate sensors.

 
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Open spectrographs, designed as hyperspectral cameras, are usually used in the recycling sector to perform the separation of different plastics. Working in combination with a broadband NIR light source (e.g. built up from high-intensity halogen spotlights), these cameras combine a moderate spatial resolution with a good spectral resolution of the objects.
Plastic granulates on the other hand, do not require individual spectral differentiation. Instead, an integral process should record as many plastic pellets as possible at the same time, thereby obtaining reliable information about the quality or purity of the product. The complex technology that would be necessary to determine the spatial resolution is unnecessary and can be dispensed with.
A more cost-effective alternative is a system that works in accordance with the three-range procedure.

 
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Sometimes it makes sense to follow. For example, your conscience or good advice from friends. But following people or brands on Instagram or LinkedIn? That is not obligatory. And what about the mainstream? "All is well! Just not always, just not everywhere and not for everyone" (to “follow” Novalis). At Sensor Instruments, although we prefer to choose our own path, we do see the need to follow certain things; for instance the colors.
Especially in terms of the color of recyclates, our esteemed market companions have been quite busy lately. Today, almost every company in the plastics recycling sector uses a portable device to measure the color of recyclates. These do their job, with the expected ease of use, at an affordable price and with precision. But are they really precise?

 
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What is the best way to monitor my product throughout its life cycle?
The digital product passport from R-Cycle, DPP for short, provides an excellent basis for this task. The product and recycling-relevant data can be queried in a simple manner using the DPP. The DPP can be opened with two different codes: a QR code or a digital watermark. Both can either be applied to the product as sleeves or labels or lasered into the injection mould as a 3D code.
Digital watermarks are considered copy-proof, whereas a QR code is easy to imitate. Nevertheless, a QR code can be classified as 'safe’ in combination with the TAGTEC masterbatches from Gabriel-Chemie. The TAGTEC masterbatches from Gabriel-Chemie contain a rich selection of different light-stimulable markers that can be detected using special optical sensor technology from Sensor Instruments. TAGTEC-marked products have proven to be forgery-proof, especially when used in combination with the features provided by a DPP, thereby providing very robust and reliable supply chain monitoring.

 
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Improved Sorting of Plastic Waste with Luminescent Pigments
The HolyGrail 2.0 Initiative aims to improve the sorting of plastic waste. For this purpose, digital watermarks containing information on packaging type, material, and usage will be applied on products. However, the method also has certain drawbacks. Here, luminescent pigments provide an alternative that is permanent and can withstand several processing cycles.