Structural characterisation via C-14-PMMA impregnation technique: Method and application development
Year: 2017
Type: dissertation
Abstract: The C-14 polymethyl methacrylate (C-14-PMMA) impregnation technique is used to analyse the spatial distribution of porosity. As such, this work focuses on two interlinked aims: to further develop the C-14-PMMA impregnation technique, particularly the polymerisation and autoradiography steps; and to further develop its application extending it from granitic materials to fine-grained structures such as clays as well. To achieve these aims, method development focused on making the C-14-PMMA impregnation technique more flexible and suitable to a wide variety of conditions while maintaining its robustness. As such, we investigated the use of thermally degrading initiators and other impregnants. Thus, we examined the use of thermally degrading initiators as a way of completing the entire sample handling procedure in a laboratory without necessitating transportation to irradiation facilities, which are currently rare. Furthermore, we studied the use of a water-soluble comonomer, 2-hydroxyethyl methacrylate (HEMA), to allow for the possibility of impregnating water-saturated matrices in future, the focus of articles I and II. The second aim focused on the application-related development for the C-14-PMMA impregnation technique and tailoring the methodology to suit the different applications. Towards this end, we compared our results with those obtained via previously used methodologies and other measurement techniques. As such, the C-14-PMMA impregnation technique can be linked to multiple other techniques, providing comprehensive information on the materials studied. In this study, we examined the mineral porosities of rock at the centimetre scale using C-14-PMMA autoradiography (AG) and at the micrometre scale using scanning electron microscopy (SEM) imaging with the aim of studying the effect of the mineral structure on the spatial distribution of porosity. This is detailed in article III. We also studied the fixation of a contrast agent that does not require pressurised intrusion used to image the connected porosity of crystalline rock through SEM and X-ray tomography. In this case, impregnation with methyl methacrylate (MMA) served to fix the contrast agent in place. This research is described in article IV. Our results from the method development studies show that polymerisation can be reliably accomplished within crystalline rock using thermally degrading initiators with no notable drawbacks. We also found that clay rock could be impregnated and the impregnant could be polymerised with the same initiators as well. The two-monomer mixtures (100% C-14-labelled methyl methacrylate (C-14-MMA) and a mixture of 75% HEMA and 25% C-14-MMA) yielded fairly similar results and were consistent with reference values. The application development studies show that valuable information may be gained by combining the spatial distribution of the porosity with spatial information on the mineral structures. The contrast agent for SEM and X-ray tomography was successfully fixed in place by impregnation and polymerisation, and the contrast improved through both imaging techniques.
Source: Työväentutkimus Vuosikirja
Author: Juuso Sammaljärvi
Language: English
Topic: Rock Mechanics and Modeling
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2765540936