TESTING | MATERIALS Right:
Instruments such as the Netzsch DSC 300 Caliris can be used to determine content and consistency of recycled plastic feedstocks
Testing first “A complete physical property characterisation should be performed before a recycled resin enters the design phase. Design engineers need to ensure that the products can endure the same physical stresses whether using virgin or recycled material,” advises Regele. “Dynamic Mechani- cal Analysis (DMA) can be used to screen and analyse the behaviour and properties of such materials. The Waters TA Instruments DMA850 measures mechanical properties of materials as a function of time, temperature, and frequency. DMA can also quantify finished component and product characteristics, demonstrating the effect that processing has on end-use product performance. In turn, the results can predict adverse performance effects.” The value of using thermal and rheological testing systems is highlighted by Dr Shona Marsh, Sector Manager Polymers at Netzsch, who de- scribes them as key to improving the recycling process’s efficiency and sustainability. “Mixed plastics frequently find their way into recycling streams, making it crucial to develop methods for straightforward identification of various plastic types. As the recycling industry grows, being able to perform consistent analysis across global production locations is essential,” she says. “DSC can enable the analysis of mixed plastic waste by utilising the thermal fingerprint of a material, which is influenced by factors such as the
IMAGE: NETSCH
polymer backbone structure, molecular weight, side groups, and branching. Different melting temperatures can be used to identify different components of a mixture, while their weight percent- age is estimated based on the melting enthalpy. DSC performs regardless of colour pigments, making it more universal than IR technologies,” Marsh says.
Machine learning Netzsch says the integration of machine learning and data analytics is revolutionising the materials testing sector. The company’s software offering to enable identification of plastics in recycling streams and to automate analysis across global production sites includes AutoEvaluation, PeakSeparation, and Identify. AutoEvaluation uses mathematical algorithms to detect and assess all phenomena within DSC curves and other thermal analysis techniques to guarantee consistent, clear results. Advanced users can benefit from the automatic and autonomous analysis for additional validation, improving both reliability and precision. The PeakSeparation function presents experi- mental data as the additive superposition of peaks and allows separation of overlapped peaks through the application of basic mathematical profiles. The algorithm looks for the peak param- eters and gives the best minimal least square fit between simulated and experimental curve. Figure 1 shows a DSC trace of 20/80 wt% PP/HDPE mixture (represented by the black curve). The PeakSeparation function is applied to reveal the blue and the green curve at higher temperature, representing the HDPE and PP component respectively. The red curve reflects the superimpo- sition of the blue and green curve as a fit function to the measured DSC signal (black curve). The Identify database, included in Netzsch
Figure 1: Fig 3 - Example of a 20/80 PP/HDPE mixture separated using the Netzsch PeakSeparation DSC software to enable easier identification of mixed plastics Image: Netzsch
46 COMPOUNDING WORLD | March 2024
Proteus software, currently features around 1,300 entries. In addition, there is an optional library with DSC measurements on 1,150 different polymer products (169 polymer types). “Intelligent software tools are vital for address- ing challenges on a global scale, with automation, precision, and repeatability playing key roles in delivering effective outcomes,” Marsh explains. “Moreover, they are crucial not only for improving recycling rates but also for mitigating knowledge
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