Fraunhofer Institute for Structural Durability and System Reliability LBF
Fraunhofer Institute for Structural Durability and System Reliability LBF

Ultrasonic Testing

With ultrasound, mechanical properties can be examined at high frequencies. Ultrasonic measurement techniques allow non-destructive examinations at measurement frequencies between 1 MHz and 100 MHz with rates of up to 1000 measurements per second. Typical applications are monitoring of:

  • Drying and curing of paints and varnish (water or solvent based)
  • The hardening of adhesives (acrylates, polyurethanes, epoxy resins, UV)
  • Crystallization processes

We offer ultrasonic measurements in reflection or transmission, the examination of various issues and the adjustment of these specialized methods to your needs.

Expand all Close all

Ultrasound Film Rheometer

The measurement method serves the time-resolved measurement of mechanical moduli of polymer coatings: The simultaneous measurement of shear modulus, longitudinal wave modulus, Young's modulus, bulk modulus and Poisson´s ratio is possible.

An important field of application is the time-resolved measurement to monitor drying and hardening processes of varnish, coatings and adhesives. At the beginning, the usually viscous sample is applied to the glass surface of the measurement cell (see picture). Ultrasonic signals are reflected at the interface between measurement cell and sample and are detected, evaluated and plotted online on the measuring computer.

Special characteristics of this method are the exposed sample surface facing up, the high frequencies of ultrasound and the high time resolution. The open surface allows the variation of environmental conditions (such as temperature, humidity, light and UV irradiation) and the combination with other measurement techniques (for example: IR-Spectroscopy).

Instrument parameters:

Measurement frequency:   1 MHz to 100 MHz (standard 5 MHz)

Temperature:                     10 °C to 60 °C

                                          High temperature option: up to 180 °C

Time resolution:                 <10 ms (>100 measurements per second)

Film formation of water borne polymer dispersions

For the optimization of formulations for lacquers or adhesives, it is important to know the viscoelastic properties and the drying and hardening processes over the course of time. The ultrasonic film rheometer allows the direct measurement of the viscous and elastic properties during the drying process of lacquers and adhesives, crystallization processes and other solidification processes. Moreover, the ultrasound measurement method has been coupled with IR-spectroscopy. In this way the quick acquisition of both moduli values and chemical conversion values during chemical hardening reactions is possible.

  • Monitoring of film formation of waterborne dispersions and solvent based lacquers (see figure)
  • Monitoring of thermal hardening or UV hardening of adhesives (acrylates, polyurethanes, epoxy resins, casein glue, and many more)
  • Temperature dependent examinations ( Crystallization processes, phase transitions, glass transition)
  • Determination of mechanical properties of polymer modifies cement
  • Monitoring of foam formation (for example PU-foams)
  • High throughput screening with parallelized measurements with up to 16 measurement channels

  • I. Alig, D. Lellinger, J. Sulima, S. Tadjbakhsch, Filmbildung von Lacken und Klebstoffen: Neues Meßverfahren mittels Ultraschall ermöglicht bessere Charakterisierung, Farbe & Lack 102 (1996) 56
  • I. Alig, D. Lellinger, J. Sulima, S. Tadjbakhsch, Ultrasonic shear wave reflection method for measurements of the viscoelastic properties of polymer films, Rev. Sci. Instr. 68 (1997) 1536-1542
  • I. Alig, D. Lellinger, Ultrasonic methods for characterizing polymeric materials, Chemical Innovation (2000) (2) 12-18
  • I. Alig, S. Tadjbach, D. Lellinger, H. Oehler, M.Wenzel, Ultraschallverfahren zur Verfolgung von Trocknung und Verfestigung von Lacken und Klebstoffen, Farbe & Lack 109 (2003) 76
  • H. Oehler, D. Lellinger, I. Alig, Filmbildung von Dispersionen mit Ultraschall verfolgen, Farbe & Lack 111, 7 (2005) 22-26
  • I. Alig, S. Tadjbach, D. Lellinger, H. Oehler, M. Wenzel, Ultraschallverfahren zur Verfolgung von Trocknung und Verfestigung von Lacken und Klebstoffen, Farbe & Lack 109 (2003) 74-78

Related Links: