Non-destructive testing

In shearography, components are excited by the use of halogen lamps or changes in pressure.  The resulting and always reversible deformations of the component in the micrometer range depend on the local stiffness. Since flaws such as air inclusions or delaminations influence the local stiffness, they can be measured. A special camera records the deformations of large test surfaces resulting from the excitation in a matter of seconds, thus enabling the detection of defects. The method is particularly suitable for elastomeric and thermoplastic components with relatively simple geometry. 

A shearography system with several megapixels of resolution and various excitation sources are available for testing at SKZ.

In terahertz or radar testing, electromagnetic waves are introduced into a component without contact, interact with the internal structure and are measured. One-sided access is sufficient and, in contrast to X-ray methods, the radiation is not ionizing and therefore completely non-hazardous. The systems are particularly suitable for micrometer-accurate layer thickness measurement - also of multilayer systems in films - for the detection of production and manufacturing-related defects, for monitoring changes in aggregate state, for inline determination of basis weights and for characterizing foams in terms of cell size and density. Inline use of terahertz in plastic melts directly in the compounding process can also provide valuable information on, for example, particle sizes, gel particles or degrees of melting. 

SKZ has various optical terahertz and fully electronic radar systems with high resolutions in the micrometer range and recording rates in the multi-digit Hertz range for laboratory and inline use.

In thermography, the surface temperature of a component is recorded using thermal imaging cameras. Either the component, which is heated anyway by the manufacturing process, is observed or it is brought out of thermal equilibrium with the aid of halogen lamps, flash lamps or induction, for example. The surface temperature measured depends on the internal structure of the test part, since internal defects such as air pockets, cracks, delaminations or ondulations influence the heat flow in the part. In the same way, direct imaging coating thickness measurements with accuracies in the micrometer scale are possible. Due to the robustness and size of the camera systems, they can be easily integrated into production processes from the fields of injection molding, additive manufacturing, joining and extrusion.

Numerous different thermal imaging cameras (microbolometers and quantum detectors) with high thermal, geometric and temporal resolutions are available for testing at SKZ.

In ultrasonic testing, mechanical waves are introduced into a test component by contact via a so-called coupling medium such as water or without contact via air. These waves interact with the internal structure and are then measured even if access is only possible from one side. In this way, defects and layer thicknesses on a micrometer scale and changes in aggregate state, such as occur during the curing of adhesives or solidification of plastic melts, can be detected. Inline use of ultrasonic technology in plastic melts directly in the compounding process can also provide valuable information on, for example, filler contents, viscosity or impurities.

For testing purposes, SKZ has numerous different contact or non-contact ultrasonic systems available for use in the laboratory, on the construction site or in the pilot plant with suitable transducers for testing components and plastic melts.

Dielectric analysis (DEA) enables the characterization of crosslinking processes in thermosets, composites, adhesives and coatings. This can be done with single-use sensors in the laboratory as well as multi-use sensors in the process. DEA can be used to describe the crosslinking behavior, reactivity and degree of cure of these materials via the parameters of the dielectric loss factor and ion viscosity.

The following measuring devices are available at the SKZ for this purpose:

• DEA-System (1 mHz – 1 MHz, 2 channels)
• DEA-System with Oven (1 mHz – 1 MHz, 2 channels, room temperature – 275 °C, heating rate 40 K/min)

Standardized measuring geometries are used for industrial color measurement of plastic products based on standardized procedures. The measurements are carried out spectrally, the output of the color values and the indication of the color distances are usually carried out for industrial applications according to the CIE L*a*b* system. Many other color systems are also possible. The output of reflectance curves is also possible.

The following measuring instruments are available at SKZ for this purpose:

• Laboratory instruments with d/8° geometry (reflectance/transmittance; with/without gloss trap)
• Hand-held measuring devices with 45°/0° geometry
• Gloss meter (60° angle)
• Inline melt colorimeter (reflection/transmission with temperature measurement)
• Inline colorimeter with d/8° geometry (for extrudates)
   

Spectroscopic investigations with near-infrared light (NIR) provide insight into the composition of plastics, such as additive or filler content. Similarly, the moisture content of granulates or the hydrolytic degradation of polymer melts can also be monitored. The use of mobile measuring systems also enables uncomplicated incoming goods inspection and process monitoring, e.g. during the pretreatment of plastic surfaces or the curing of adhesives and resin compounds.

The following measuring instruments are available at SKZ for this purpose:

• NIR process spectrometers (900 - 1,700 nm, with fiber connection and lamp drift correction)
• NIR process probes (with different window geometry: normal and ground hemisphere geometry, 30° bevel)
• Mobile NIR process spectrometer (900 - 1,700 nm, with fiber connection)
• Mobile NIR handheld spectrometer (900 - 1,700 nm)
   

The use of nuclear magnetic resonance enables very detailed material analyses. Among other things, it is possible to identify impurities or quantify the content of additives and unwanted residues of certain ingredients. In addition to classical solvent-based NMR spectroscopy, which uses magnets cooled with liquid helium and strong fields, more and more benchtop systems with low-field permanent magnets have become established on the market for industrial applications. Such systems are suitable for in-process material monitoring and development. They can be used, for example, to characterize the crystallinity of polyolefins or the curing state of adhesives or resins.

The following measuring instruments are available at SKZ for this purpose:

• NMR spectrometer (400 MHz, He-cooled)
• Unilateral NMR (20 MHz, room temperature, one-sided non-destructive sample access, with precision lift)
   

Knowledge of the permeation properties of films is particularly important in the packaging industry or in high-barrier applications. But gas permeability is also an important factor for pipes and components. Gas permeability is tested using a manometric method based on DIN 53380-2.

In addition, we offer a rapid test method in which the permeability test is performed using helium as the test gas and a coupled mass spectrometer. In this case, the measurement time can be reduced to a few minutes or a few hours for high barrier applications. In addition to foils, bottles and beakers can also be used as test specimens here, which can be integrated into the test system via adapted adapters. This is particularly advantageous for comparative measurements between different materials. 

In addition, the mass spectrometer can be used to perform sniff tests to detect leaks in components using helium.

The following measuring instruments are available at SKZ for this purpose:

• GDP-C (disc with Ø 110 mm, +20 - +80 °C, oxygen, carbon dioxide, nitrogen, argon, helium, other gases on request).
• GDP-C measuring cell with mass spectrometer PhoeniXL 300 (disk with Ø 110 mm, +20 - +80 °C, helium)
• Measuring cell for films and free-form surfaces with mass spectrometer Inficon 1000 (disk with Ø 100 mm at +15 - +45 °C or bottles/cups at room temperature, helium)