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Application of NMR Spectroscopy and Multidimensional Imaging to the Gelcasting Process and In-situ Real-time Monitoring of Cross-linking Polyacrylamide Gels
註釋In the gelcasting process, a slurry of ceramic powder in a solution of organic monomers is cast in a mold. The process is different from injection molding in that it separates mold-filling from setting during conversion of the ceramic slurry to a formed green part. In this work, NMR spectroscopy and imaging have been conducted for in-situ monitoring of the gelation process and for mapping the polymerization. 1H nuclear magnetic resonance spectra have been obtained during polymerization of a premix of soluble reactive methacrylamide (monomer) and N, N'-methylene bisacrylamide (cross-linking molecules). The premix was polymerized by adding ammonium persulfate (initiator) and tetramethyl-ethylene-diamine (accelerator) to form long-chain, cross-linked polymers. The time-varying spin-lattice relaxation times T1 during polymerization have been studied at 25 and 35°C, and the variation of spectra and T1 with respect to extent of polymerization has been determined. To verify homogeneous polymerization, multidimensional NMR imaging was utilized for in-situ monitoring of the process. The intensities from the images are modeled and the correspondence shows a direct extraction of T1 data from the images.