Lecture 013.001

NON-INVASIVE INVESTIGATION OF AGED RESINS USING UNILATERAL NMR
BY CINDIE KEHLET

During the past decades conservators have experienced increasing problems with objects made of synthetic resin materials. Identification of the material and characterization of the degradation state of the artifact is a natural first step before conservation can take place. With advancements in technology potential new techniques arise that so far only have found limited use for the study of cultural heritage. Nuclear magnetic resonance (NMR) constitutes such a technique. It is an insensitive technique and relatively large sample sizes are therefore a requirement. At the same time samples need to be small enough to fit into a magnet with a typical bore diameter of only a few centimeters. Until the development of the non-invasive single-sided NMR instrument the technique was not suitable for cultural heritage applications. Here we present how the Profile NMRMOUSE ® can be used for monitoring and diagnostics of the degradation state of works of art made of resins. The advantage of the technique is that it can assess the degradation state of the material underneath the surface which is a limitation of most other noninvasive techniques such as Fourier transform infra red spectroscopy. The technique measures the mobility of protons and as materials degrade their mobility changes which is captured in the resulting relaxation decay. The technique is suitable for recording the degradation state of objects in three dimensions. We have applied this technique to a large set of test samples of various types of resins that have undergone artificial aging. The goal is a systematic study of the influence of aging on the materials and how the molecular changes are captured in the measured relaxation decays. We furthermore explore the applicability of the technique for assessment of the effect of conservation and how treatments affect the material at different depths.

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