Q NET Engineering GmbH

NMR Inspect

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Nuclear Magnetic Resonance Surface Technique for the Rubber Processing Industry

Situation

Elastomers are exposed to high levels of mechanical, thermal and chemical stress which gradually wears down the material. An unexpected failure of these materials might have severe consequences. This is why non-destructive testing of the material properties and the ageing resistance is of increasing importance.

Up to now, quality control of rubber product production was limited to the determination of mechanical parameters with destructive testing methods. Continuous process and product quality control with non-destructive methods was not possible.

The nuclear magnetic resonance method presents a new, non-destructive approach to the characterisation of microstructures of macromolecular materials like elastomers. The method is used in chemical analyses and human diagnostics. Up to now the use of this non-destructive testing technique was limited because the sample had to be inserted into a sensor that enveloped the sample. The inspection of big and bulky parts was therefore impossible. The testing instrument NMR-INSPECT is the first portable testing device with surface technique worldwide.

The testing instrument runs on batteries, is easy to operate, enables testing of samples of any size and can also be used for process-integrated quality control.

NNMR device for rubber characterisation
Figure 1: NMR device for rubber characterisation

Method

Nuclear magnetic resonance is based on the interaction between the radio waves and atomic nuclei which are inside a strong magnetic field. Hydrogen nuclei evoke the biggest effect. The nuclei that are in the NMR sensor's sphere of influence are put into phase-coherent oscillation and generate a signal. In case of relaxation due to energy transfer processes the phase coherence is broken and the nuclei stop oscillating. The amplitude of the signals is an indicator for the number of hydrogen nuclei within the recorded volume (spin density) while relaxation times are characteristic for the nuclei's molecular mobility (spin mobility).

Our Solution

Together with Fraunhofer IZFP, Q NET Engineering GmbH developed a testing system with surface technique based on the hydrogen nuclear magnetic resonance method. The following material properties of elastomers can be tested spatially resolving:

Possible Applications

Multilayer Tyres

Modern steel belt tyres are built of several layers of different rubber compounds. NMR Inspect is designed to characterise the thickness of the different layers.

Rubber Corrosion Protection Coating

The NMR testing device is designed to identify the moisture content of rubber coatings. In this way, the precise residual service life of the coating can be determine.

Coated Fabrics

Elastomer-coated fabrics are subject to aging in case of massive mechanical, thermal and chemical stress. The NMR device with one-sided access can detect and prove this aging process.

Determination of the Moisture Content of Concrete with Nuclear Magnetic Resonance Surface Technique

Situation

Moisture within buildings can cause massive damage which can be stopped or prevented by timely and efficient countermeasures. For example renovation companies depend on a reliable estimation of the extent of the renovation. In case of safety-relevant parts like bridge piers, the analysis of the damage caused by moisture is especially important in order to evaluate the residual life.

Cost-efficient renovation work requires precise locating of the damages and correct diagnoses of the moisture content in order to evaluate the condition of the building. Up to now, only random sampling and conventional testing methods were used. Usually core samples were removed from the building and analysed in the laboratory.

In case of historically valuable buildings this procedure is unwanted due to its destructive nature. In case of safety-relevant structures, sampling is just insufficient for comprehensive damage analyses. Extracting the sample, taking it to the laboratory and repairing the test object afterwards has been quite cost-intensive up to now.

NMR device for characterizing concrete
Figure 2: NMR device for characterizing concrete

Solution

NMR Inspect is the first portable NMR testing device for on-site testing of construction material directly at the building itself. Unlike conventional NMR testing methods, NMR INSPECT enables one-sided access testing by putting a sensor very close to the construction material to be tested. Sampling and subsequent repairs are not necessary any longer even for bigger test objects like for example walls.

NMR INSPECT is designed for non-destructive, comprehensive locating and diagnosing of moisture conditions of a building at low costs.

Advantages

Testing System

The sensor of the testing system consists of a strong permanent magnet and a high frequency antenna that are aligned electronically. Outside the sensor, a circular measuring volume (sensitive volume) is generated. The distance between the sensor and the sensitive volume and thus the measuring depth can be varied by changing the antenna's transmission frequency.

The heart of the device consists of the electronic components which are very powerful despite their small size with a pulse power of up to 30 kW.

Technical Data

Contact

Paul Kröning
Phone: +49 (0) 6 81/9 76 71 53
Fax: +49 (0) 6 81/9 76 71 58