Simplifying Polymer Characterization with DSC Curve Recognition

The novel NETZSCH DSC 214 Polyma makes DSC investigations easier and more comprehensive than ever before. It includes a series of smart innovations which together address all aspects of a perfect DSC investigation as shown in Figure 1.

The completely new Arena furnace and Corona sensor in the instrument, along with the new Concavus sample pan, allow for extremely fast and unique high-quality measurements.

The new software features the SmartMode user interface which greatly facilitates operation. The innovative AutoEvaluation even allows for completely autonomous evaluation of the measurement - reproducibly and reliably.

The final step in a complete DSC investigation is the interpretation of the measurement results. Identify is a groundbreaking DSC curve recognition and database system. Using Identify, known database curves and literature data are used to recognize and identify unknown DSC curves, ultimately resulting in interpretation of the DSC result.

The process can be applied to a completely unknown sample or to routine quality control (QC), where Identify can show a sample's level of agreement with saved measurements for samples already deemed as acceptable. Identify is a highly powerful tool for any day-to-day task such as material identification, as well as for quality control and failure analysis. It also acts as an archiving system, as it allows direct access to the evaluated DSC curves stored in the database. With just a single click, Identify offers results.

Figure 1. All aspects (360° view) of a complete DSC investigation

Material Identification

Figure 2 shows how Identify is executed on a non-evaluated DSC curve. With a single click, the DSC curve is autonomously evaluated by the NETZSCH Proteus® software using AutoEvaluation, and the Identify results are immediately displayed as seen in Figure 3. The left side list shows measurements and literature data from the database sorted according to their similarity to the unknown DSC curve.

The list on the right shows the similarity between the "unknown" and defined classes which are explained in detail below. In this instance, the glass transition around 80°C and the melting peak around 250°C detected in the unknown DSC curve clearly allow the measured sample to be identified as PET.

Figure 2. Applying Identify to a non-evaluated DSC curve with a single click.

Figure 3. Identify results after only one click on a DSC curve; the white line represents the unknown curve, the black line the most similar database curve.

Working of Identify

The approach used by Identify is very similar to that used by modern image recognition software for identifying persons or objects as seen in Figure 4.

Figure 4. Approach used by Identify – based on image recognition.

It is possible to divide this approach into three key tasks:

Segmenting the DSC Measurement Curve

Significant caloric effects such as glass transitions or exothermic and endothermic effects must be identified and distinguished from irrelevant parts of the DSC curve.

This highly challenging task is performed consistently for most measurements by AutoEvaluation without any user interaction required.

Extraction of the Properties of the Effects Found

Properties such as the peak area or the extrapolated onset temperature are studied automatically with the classical features of the NETZSCH Proteus® software.

Recognition of the DSC Curve

The unknown DSC curve is compared not just to specific database measurements and literature data but also to classes of each. Similarity values are computed practically in-situ using advanced mathematical algorithms. The database "hits" are sorted in terms of similarity in decreasing order.

Identify is capable of searching through hundreds of database entries and within a single second, find the DSC measurement curves most similar to the unknown sample, as shown in figure 5. All it takes is just one click.

Figure 5. An unknown DSC measurement curve in comparison with some database curve examples. The most similar curve is labeled "best hit'.

Furthermore, effect-based algorithms allow Identify to work not only with true measurement results, but also with literature data as library entries. Identify is more powerful than that. Different general approaches to database searches are displayed schematically in figures 6A and 6B.

Some material classes such as PE or PET are already included in the software, but users can additionally create their own classes, which will "learn" as each new member is added.

Figure 6. Different approaches to a database search: Queries (A), classification (B) and the Identify solution (C), which applies both.

Application in Quality Control

In a quality control setting, Identify is highly beneficial as well. Figure 7 shows the use of a quality class within Identify to analyze a DSC measurement on a rejected PA6 part (with broken clip). The melting peak of the defective part is at a lower temperature than that of the good parts, and an additional small peak was detected at 239°C.

The calculated similarity to the user class "PA6_GF30_parts_passed" was thus relatively low (only 56.61%).

Figure 7. DSC measurement on a rejected PA6 part (with broken clip) analyzed by means of Identify.

Employment and Optional Settings in Identify

Identify is also very easy to use. Results are seen after a single click and with regards to the management of libraries (creation and extension) and their entries, everything is accessible at a glance.

It is possible to easily include or exclude existing libraries from the search using a list with checkboxes in the main view of Identify. The algorithm types "Single" and "Multi" are used to distinguish between whether the DSC curve stems from a single- or a multi-component sample like a polymer blend.

Summary

To summarize, Identify is a unique DSC curve recognition and interpretation system providing results with a single click, is useful for material identification and quality control, is both easy to use and sophisticated, includes a database with NETZSCH libraries for polymers as a basis as well as libraries that can be created by the user and manages measurements, literature data and classes, incorporating the user's knowledge.

This information has been sourced, reviewed and adapted from materials provided by NETZSCH-Gerätebau GmbH.

For more information on this source, please visit NETZSCH-Gerätebau GmbH.