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.

The DDP method enables more accurate determination of the tightness of polymer-metal hybrids

16:9

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?

Röhm produces antimicrobial PMMA for transparent partitions.

Plexiglas XT Antimicrobial is an extruded sheet material with a special surface treatment on both sides. The coating contains a formulation that controls microbial growth

Polymethylmethacrylat

Thermoplaste

Platten

Halbzeuge und Zwischenprodukte

Kunststoff-Halbzeuge

Disease Protection by PMMA

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.

Susanne Schröder will become editor-in-chief of the magazines Kunststoffe and Kunststoffe international on December 1, 2020. Until now she has been editor-in-chief of the trade journal FORM+Werkzeug

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

Werkzeugverwaltungssoftware

Biokunststoffe

Presswerkzeuge, Kunststoff

Werkzeugreinigung, Kunststoffe

Standardkunststoffe

Kunststoffverarbeitung

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 RadiciGroup High Performance Polymers Business Area is adding significantly to its global production capacity with new construction and installations in North America, Europe and China.

The new plant in Mexico with an area of 20,000 m2 is part of the investment strategy in North America

Compound

Compoundeure

Radici Increases Production Worldwide

Components in solar power stations are exposed to strong solar radiation and other severe environmental influences. These challenges can be met with the aid of self-lubricating, UV-resistant plastic compounds.

The self-lubricating EP-15 sliding bearings consist of a UV-resistant POM compound and therefore have long-term resistance to the intense solar radiation in photovoltaic plants

Self-Lubricating Polyoxymethylene Bearings for Solar Systems

Solar / PV

Energieerzeugung

Erneuerbare Energie

Polyoxymethylen

Defying the Sun

Thanks to new technologies and together with other chemical derivatives the greenhouse gas CO2 can be converted into plastic precursors. Covestro is developing sustainable insulating materials for the construction sector based on this raw material.

Using innovative CO2 technology, Covestro already produces the CO2-based precursor cardyon, which is utilized in the manufacture of mattresses, sports flooring, textile fibers and components for vehicle interiors

Polyurethan-Schaumstoffe (PUR)

Baubetrieb / Bauwirtschaft

Dämmstoffe

Schaumstoffe und Vorprodukte

Polyurethan

Using CO2 in Rigid Foam Insulation Boards

For lightweight applications e. g. in automotive engineering BASF developed carbon fiber-reinforced polyphthalamide (PPA) grades with fillings of 20, 30 und 40 %.

The carbon fiber-reinforced PPA e. g. can replace aluminum and magnesium 

PPA Now with Carbon Fiber-Reinforcement

Elektronik

Automotive

Faserverbundwerkstoffe

Andere Werkstoffe

Lightweight Metal Replacement

Teknor Apex presents three halogen-free FR glass-reinforced polyamide compounds with UL94 ratings of V0.

Application example: engine cover in the automotive industry

Polyamide

Glass-Reinforced and Halogen-Free Flame-Retardant

Evonik has introduced a PEEK for FFF and FDM printers. The material was developed specifically for medical technology applications such as prostheses, surgical instruments and hearing aids.

The 3D-printable filament can be used, for example, for implants or hearing aids

Polyetherketon

Additive Fertigung

Werkstoffe für additive Verfahren

Biocompatible and Easy to Process PEEK

Two new inorganic yellow pigments based on iron oxide and zinc oxide respectively are designed for coloration in a temperature range of between 220 and 260 °C.

The yellow pigments are used for all common polymer materials as well as for engineering thermoplastics even at the highest production temperatures

Pigmente, bunt

Additive

Farbstoffe und Pigmente

Farbstoffe

Yellow for High Temperatures

Polymaker will offer the Polymaker PC-r 3D printing filament made from recycled polycarbonate (PC). The PC for the filaments comes from materials supplier Covestro and consists of a combination of recycled plastic waste and virgin material.

The combination of recyclates and virgin material reduces the carbon footprint of the polycarbonate and still allows it to be extruded into filaments

Filamente für additive Verfahren

Polycarbonat

Kunststoff-Rezyklat

Water Bottles Become Filaments

Bipolar plates are one of the key components of fuel cells and redox flow batteries. They consist of plastics compounds highly filled with electrically conductive materials. To save space, cut costs, and reduce weight, there is increasing demand for the production of thinner plates without compromising robustness and service life. This can be achieved using modified polymers. With a new technology, bipolar plate films based on these modified polymers can be processed as coils.

The modified polymers enable films to be processed  as coils

Modified Conductive Compounds Make It Possible to Manufacture Bipolar Plates from a Bipolar Film Coil

Brennstoffzelle

Stromversorgung

Brennstoffzellen

Mobilität

Folien

Ultrathin Bipolar Plates for Fuel Cells

The new mobile communications standard 5G is advancing steadily. This development is also increasing the demand for materials that facilitate and ensure the high transmission rates for 5G signals. Plastics manufacturer Covestro has presented a corresponding thermoplastic polyurethane (TPU).

Covers for cell phones must not only protect the devices from shocks, but also allow mobile signals to pass through without interference

Cell Phone Covers Made from TPU

Continuous fiber-reinforced thermoplastic composites have also become established with thin-walled housings for consumer electronics and information technology. Not only do they offer high stiffness and help to reduce weight, but also enable the integration of classy appearance and functions. What is more, if the housings are produced using the hybrid molding process, costs, processing steps, and cycle times can be reduced.

The Carbon 1 Mark II smartphone from Carbon Mobile was developed in Germany. The matt-black carbon fibers lend the smartphone a classy high-tech look

Composites Reduce Weight and Simplify Production of Electronics Housings

Composite-Halbzeuge

Glasfasern / -matten

Kohlenstofffasern / -matten

Organobleche (gewebeverstärkte Thermoplast-Halbzeuge)

Lightweight to Fit in a Pocket

Electrical architecture in an E-car is significantly more challenging than for conventionally powered vehicles. Particularly for insulation of high-voltage (HV) components, the demands on the materials used are increasing. With specially-tailored materials for electric vehicles, challenges in automotive high-voltage technology can be overcome.

Insulation of high-voltage components in electric vehicles makes high demands on the materials used

Polyamide Specialties for Electromobility

Elektromobilität

High Voltage in Cars

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>