The interfacial tightness of hybrid polymer-metal parts such as injection-molded connectors represents a decisive quality characteristic. Until now, however, there has been a lack of suitable measurement technology with which to quantify the media tightness of such molded parts. A new method delivers significantly more accurate results than previous test methods.

Measurement Method for the Exact Leakage Determination of Polymer-Metal Hybrid Parts

Messtechnik

Verbundwerkstoffe / Werkstoffverbunde

Kunststoff Werkstoffe

Prüfen von Kunststoffen

Stecker

Elektromechanik

Kunststoff

Bauwesen

Baustoffe

Steckverbinder

How Tightly Sealed are Connectors Really?

Susanne Schröder will become editor-in-chief of the magazines Kunststoffe and Kunststoffe international on December 1, 2020. The current editor-in-chief Dr. Karlhorst Klotz will leave the company by mutual agreement.

Werkzeuge für Leichtbauwerkstoffe

Präzisionswerkzeuge

Tiefziehwerkzeug

Dienstleistungen

Werkzeug-, Formen- und Modellbau

Werkzeugüberwachung

Toolmanagement

Werkzeugwechselsysteme, Spritzgieß

Kunststoffverarbeitung: Maschinen und Komponenten

Werkzeuge für die Kunststoffverarbeitung

Spritzgießwerkzeuge

Werkzeug- und Formenbau

Modulare Werkzeugsysteme

Absaugungen für Werkzeugmaschinen

Betriebsausrüstung / Betriebsmittel

Absaugvorrichtungen

Fluorkunststoffe

Thermoplaste

Werkzeugverwaltungssoftware

Biokunststoffe

Presswerkzeuge, Kunststoff

Werkzeugreinigung, Kunststoffe

Standardkunststoffe

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Lohnfertigung

Technische Kunststoffe

Füllstoffe für Kunststoffe

Kunststoffhandel

Handel

Betriebstechnik für Kunststoffverarbeitung (Peripherie)

Kunststoffverarbeitung: Verfahren

Kunststofffasern

Verstärkungsstoffe

Kunststoff-Recycling

Kunststoff-Aufbereitung

Hochleistungskunststoffe

Qualitätssicherung Kunststoff

Qualitätssicherung

Change in the Chief Editorial Office of Kunststoffe

The non fossil fuel-based portfolio offers same high quality and performance for applications in all industries.

Gehäuse aus Kunststoff

Kühlkörper

Polyethylen

Polystyrol

Polypropylen

Kunststoff-Regenerate

Borealis Launches Portfolio of Circular Polyolefins

The Danish company Plastix recycles old fishing nets and ropes. The granules produced are used by JSP International, among others, to manufacture expanded polypropylene (EPP).

Expanded Polypropylene from Maritime Plastic Waste

Schaumstoffe und Vorprodukte

Schaumstoffe

Recycling

Umweltmanagement

Polypropylen-Compound

Kunststoff-Rezyklat

From Fishing Net to Particle Foam

The central issue in all polyurethane applications is the conversion from the past linear economy into a circular economy, and the use of sustainable raw materials in manufacturing. To do so, manufacturers are taking measures such as using bio-based raw materials, chemical recycling, and CO2 as a synthesis component. Digitalization, electromobility, autonomous driving and the construction industry are also driving PU development.

Polyurethane (PU)

Bauchemie

Automotive

Elektronik

Polyurethan-Schaumstoffe (PUR)

Halbzeuge und Zwischenprodukte

Kunststoff-Halbzeuge

Baubetrieb / Bauwirtschaft

Polyurethan

Windkraft

Energieerzeugung

Erneuerbare Energie

Sustainable Growth

Styrenics can be polymerized using different technologies and it can be modified with a range of copolymers. The resulting plastics offer a wide range of properties allowing to customize them for different applications. Because of this range of properties they are suitable for many industries. Strong demand is for example driven by the automotive industry, healthcare and the packaging industry.

Styrenic Polymers

Verpackungsmaterial

Logistik

Styrol-Copolymerisate

Medizintechnik

Medizinprodukte

Diverse Shapes and Applications

Lightweight construction, functionality and design are characteristic of material development in all areas of application for PC compounds, composites and films. The range of materials has enormous opportunities when it comes to the mobility of the future, lightweight structural construction with continuous fiber-reinforced composites, 5G technology and medical technology.

Polycarbonate (PC)

Polycarbonat

Present in a Multitude of Trends

Due to its high-performing properties polyetheretherketone thermoplastic polymer is being used more and more frequently in many products.

Polyetheretherketone (PEEK)

Elektronik-Fertigung

Polyetherketon

Mikroelektronik

Delivering Efficiency Even in  Harsh Environments

Optics play an increasingly important role in plastic components. Glossy and even surfaces are decisive for an attractive appearance. With glass fiber-reinforced polyamides (PA), these requirements can usually only be achieved with an additional coating. A PA specially developed for surface design offers an alternative approach.

Aliphatic High-Performance Polyamide for Plastic Surfaces

Spritzgießen

Polyamide

Oberflächentechnik

Faserverbundwerkstoffe

Andere Werkstoffe

Glossy Components without Painting

Renouncement is the trend that determines public perception of plastics today. Many consumers prefer products that are better for the environment, which is often equated to using less plastics. It is true, though, that plastics are important materials when it comes to finding answers to the challenges posed by the increase in population, high energy demand as well as growing urbanization and mobility.

Guest Commentary by Dr. Michael Zobel

Kunststoffe

Photonik

Optik

Leichtbau

Werkstoff

The Answer to Many Questions

In this interview with Kunststoffe, Alfred Stern, CEO of Borealis, explains why he considers fixed recycling quotas to be necessary and why voluntary commitments do not work.

Alfred Stern, CEO of Borealis, Talks about the Circular Economy

Schröder, Susanne

Streifinger, Florian

“Unfortunately, the Only Globally Accepted Ideology Is Money”

Bio-based plastics can lock away vast quantities of CO<sub>2</sub> in durable, recyclable applications and make a real contribution to climate protection. All that is needed for this is the right product design and a functioning circular economy. By focusing more on this approach, the plastics sector has the chance to evolve into a key industry of a green economy.

How Bio-Based Polymers Can Help Sequester CO<sub>2</sub> for the Long Term

Kunststoffe, biobasiert

Kunststoffe, bioabbaubar

Into the Future with Biopolymers

Dow expertise and Endurance insulation system supports Saudi cable manufacturers supplying power grid upgrade.

Elektrotechnik

Ingenieurwissenschaften

Bau- / Elektroinstallation

Elektrokabel, -leitung, -drähte

Elektrotechnik, Elektronik

Dow and NGSA Cooperate on Ambitious Grid Upgrade

For a long time, chemical recycling was considered an unfinished addition to established material processes. In the meantime, however, some technologies are making the leap into large-scale industrial use: an overview of the various processes and providers.

Overview of the Various Processes and Suppliers

What Is Happening in Chemical Recycling?

Lupine Lighting Systems manufactures extremely bright mountain bike lights with lenses made of Plexiglas. The molding compounds from Röhm meet the most important standards for e-bike and bicycle lighting.

Technische Optik

Fahrzeugbau

Polymethylmethacrylat

Bright Lights with Precision Lenses Made from Plexiglas

Characterize Plastic Surfaces More Easily with Atomic Force Microscopy

Atomic force microscopy can be used to determine various properties of polymer surfaces. However, until now it was still necessary to change the hardware on the probe for different measurement methods. A special sensor technology eliminates the need to replace the head. The example of an investigation of a polymer thin film shows how this enables the precise characterization of polymers.

Atomic force microscopy can be used to determine various properties of polymer surfaces. However, until now it was still necessary to change the hardware on the probe for different measurement methods.

Atomic Force Microscopy (AFM) has been used for a long time to characterize mechanical, electrical, magnetic and other surface properties of plastics. When using this microscopy measurement method for characterization, it is often critical that all measurements are performed at the same location on the sample surface. In this case, different surface properties can be correlated accordingly and brought into a quantitative relationship.

Until now, however, AFM measurements with different modes at exactly the same location were difficult to perform, since this usually required a hardware change on the AFM measuring instrument. In this case, the AFM head must be removed and, after appropriate modification, reinstalled. This is not only time-consuming, but also carries the risk of damaging the AFM head. With the AFM-z sensor technology, Anton Paar GmbH has now developed a possibility that allows the use of all available AFM modes in the measuring instrument without hardware change. This allows switching between modes without lifting the AFM head. The characterization of a polymer thin film made from a mixture of polymethyl methacrylate (PMMA) and styrene-butadiene-styrene (SBS) shows how this works in practice.

In Anton Paar’s Tosca series AFM, the z-sensor is integrated in a compact and lightweight “actuator body” without any cables, which ensures safe and easy handling (Fig. 1).

All measurements for the different modes can be performed with only one actuator body. This allows various properties of the sample to be measured reliably and accurately on the nanoscale without hardware modification and associated repositioning of the cantilever. The following modes are available:

<ul><li>Contact Mode,</li><li>Tapping mode,</li><li>Force Distance Curve (FDC),</li><li>Contact Resonance Amplitude Imaging (CRAI),</li><li>Electrostatic Force Microscopy (EFM),</li><li>Magnetic Force Microscopy (MFM),</li><li>Kelvin Probe Force Microscopy (KPFM),</li><li>Conductive AFM (C-AFM).</li></ul>

In the aforementioned characterization, the polymer thin film was measured on a 25 μm x 25 μm area with a resolution of 400 x 400 pixels and a scan rate of 0.5 line/s. The force-distance curves, CRAI measurement, EFM and KPFM were performed at the exact same position. This makes it possible to learn more about the sample within one measurement procedure. Each measurement step determines further qualitative and quantitative sample properties, up to the complete characterization of the sample within the selected AFM resolution.

CRAI Measurement Reveals  Height Differences

First, the mechanical properties of the polymer thin film were investigated using the CRAI mode. This measurement mode is derived from contact mode. This means that the cantilever is in constant contact with the sample in order to record the surface height. At the same time, it oscillates with a certain frequency around its contact resonance frequency. This near-resonance operation exploits the fact that the contact resonance frequency and amplitude depend on the elastic modulus of the sample, so simultaneously recorded amplitude and phase channels reflect the difference in stiffness (Fig. 2).

The height image from the CRAI investigation of the PMMA-SBS blend shows structures or islands within a matrix representing the two different polymers in the blend. The structures are higher than the matrix, as can be seen from the height profile (Fig. 3).

The contrast in amplitude and phase reflects differences in the surface mechanical properties. This reveals the information that the topography image does not show: the higher domains (islands) also include some of the other polymer, so they are not purely one polymer. This observation is a distinct advantage of the CRAI mode, as it enables a more accurate characterization of the nanoscale mechanical properties (Fig. 4).

The FDC measurement was used in the next step to quantitatively determine the elastic modulus of two distinct domains. FDC is a single point measurement of nanomechanical properties. The AFM measures the force between the probe and the sample as a function of the distance the probe moves (Fig. 5).

For quantitative results, a calibration of the cantilever is required (determination of the spring constant, cantilever sensitivity, tip geometry). After the cantilever calibration and the subsequent measurement, using a proper contact mechanics model (Fig. 6), the quantitative information on Young’s modulus, applied force, adhesion force, snap-in force and indentation depth can be easily obtained.

The values determined are similar to the literature values for PMMA or SBS, but do not correspond exactly to these . This is due to the fact that, as seen from the CRAI analysis, the stiffer structures also contain the other, less stiff polymer. It can be concluded that the matrix is predominantly SBS and the structures consist predominantly of PMMA.

Two Pass Technique for the Determination of Contact Potential Difference

In the next measurement section, the electrical properties of the sample were investigated using the KPFM. KPFM measures an electrostatic force field between the tip and the sample and provides quantitative data by measuring the contact potential difference between the tip and the sample. The KPFM is implemented as a so-called two-pass measurement (Fig. 7). In the first pass, the height information is acquired by a tapping mode scan. This is then used as input for the second pass (lift pass). In this case, the cantilever is lifted and the rescans the surface line at a constant height above the sample surface.

The oscillation of the cantilever in the lift pass is not mechanically, but electrically driven, by applying an external AC voltage between tip and sample. The feedback electronics adjust the bias voltage until the oscillation amplitude is nullified. As the result, the contact potential difference between tip and sample, or the surface potential, is obtained. This contact potential difference depends on the difference of the work function between tip and sample. The work function (Φ) is defined as the minimum energy required to remove an electron from a solid and is therefore material specific. Therefore, it can be used to characterize the material composition and relate it to the topography.

Differences in Contact Potential Show Differences in Material Composition

The KPFM results show different electrochemical properties of the matrix and the structures. By correlating the extracted height and KPFM potential profile, it was concluded that the maximum contact potential difference between the matrix and the structures is about 250 mV. Furthermore, a nearly constant and uniform contact potential difference for the matrix is observed. However, this is not the case for the structures. A rather strong variation of the surface potential of the structures can be observed. The question arises whether the difference in contact potential can be unambiguously assigned to the material composition.

To answer the question of the exact polymer distribution and the composition of the structures, a superposition of 3D-CRAI and KPFM measurements is performed. This is only possible if both measurements are performed at exactly the same position. The superposition of the two results provides important additional information. The contact potential difference clearly depends on the composition of the individual structures. The structures where one polymer predominates show the highest potential difference. In contrast, structures consisting evenly of both polymers show a smaller potential difference (Fig. 8).

By analyzing the KPFM results, the quantitative material properties can be determined using the work function. A structure in which a polymer predominates was chosen for the analysis. From the measured maximum contact potential difference, where the composition is dominated by a single polymer, a work function of 4.1 ±0.1 eV was determined for the matrix and 4.3 ±0.1 eV for the structures.

Combination of Measurement Methods Enables Accurate Characterization

The results show that an accurate characterization of different surface properties of polymers is possible by combining the different measurement methods. CRAI and FDC measurements were first used to investigate the mechanical properties of the polymer thin film. Amplitude and phase images of the CRAI mode show important information about locations with differences in mechanical properties i. e. stiffness between the different regions of this polymer blend. FDC measurements provide quantitative information about these differences in the form of the Young’s modulus of elasticity.

KPFM shows different electrochemical properties of the matrix and the structures The analysis of mechanical and electrical properties at exactly the same location on the surface allows the superposition of the CRAI and KPFM results, which provides important insights into the polymer distribution. In addition, the work function allows a quantitative analysis of the material properties.

The investigations illustrate the measurement capabilities of the AFM Tosca series. Due to the AFM technology of z-sensor integration, Tosca series enables a faster and more extensive characterization of the polymer thin film. This allows different material properties to be determined sequentially at exactly the same position using different modes.

Anton Paar GmbH  

https://www.anton-paar.com

Ausgabenartikel

With the Tosca series, all AFM measurements can be carried out with only one actuator body and thus without hardware exchange

Fig. 1. Insertion of the actuator body with cantilever into the AFM: the z-sensor is integrated in the compact and lightweight actuator body without any cables

Fig. 2. Schematic representation of the CRAI measuring principle: differences in the stiffness of the specimen and a height image are generated

Fig. 3. The height image from the CRAI investigation reveals height differences in the polymer thin film. The determined islands are higher than the matrix 

Fig. 4. The CRAI measurement shows a contrast in the amplitude (left) and the phase (right). This indicates that the higher structures consist of not only of one but of both polymers

Fig. 5. Schematic representation of the force-distance curve (FDC): the force between the probe and the sample is measured as a function of the distance the probe moves

Fig. 6. Measurement of the force-distance curve (FDC)

Fig. 7. In the KPFM, the height information is determined by tapping mode scan in the first pass. The second pass (lift) with the cantilever lifted takes place at a constant height above the sample 

Fig. 8. Superposition of 3D CRAI amplitude and contact potential difference (CPD) shows the higher potential difference for structures which are mainly composed of one polymer 

KU 5-21_Anton Paar - Hauptartikel

 Dr. Dr. Jelena Fischer has been working as a product manager for Anton Paar GmbH in Graz, Austria, since 2012.

Dirk Meister has been working as a product specialist for Mechanical Surface Characterization for Anton Paar Germany GmbH since 2019;  <a href="mailto:dirk.meister@anton-paar.com">dirk.meister@anton-paar.com</a>

Michael Schäffler has held various positions at Anton Paar Germany GmbH since 2002, currently as Market Development Manager.

Read the German version of the  article in our magazine Kunststoffe or at  <a href="https://www.kunststoffe.de/a/fachartikel/charakterisierung-ohne-pruefkopfwechsel-322893" target="_blank">www.kunststoffe.de</a>