Low-Field (LF)-NMR Liquid Relaxation: A Useful Technique for QC and to Determine the Equivalency of Materials for Coatings Formulations

By David Fairhurst, Colloid Consultants Ltd. , R. Sharma, Mageleka, Inc., R. Wörheide, Metromation Inc.

Paints and coatings in their final composition are complex; their formulation entails a multitude of system details that influence the final outcome. Hence, it is difficult to attribute the root cause when deviations are found via testing or performance quality control (QC). Further, a major concern in the industry is the question of material “equivalency.” Having a metric that represents a specific material quality and developing quality numbers is the key to implementing an appropriate QC protocol. Low-field nuclear magnetic resonance (LF-NMR) liquid relaxation is shown to provide such a test, and we explore its application as a powerful, fast, and nondestructive analytical tool to improve QC and assess material equivalency in coatings formulations. Traditional methods often fall short in evaluating raw materials, particle dispersions, or complex formulations without extensive sample preparation or dilution. LF-NMR relaxation, using a small benchtop spectrometer, overcomes these limitations by enabling direct measurements on opaque, high-solid suspensions under real-use conditions and affords a cost-effective methodology to identify the replacement of both powder and solvent raw materials. Measurements are also shown to be sensitive to solvent-particle intermolecular forces, making it a useful technique to easily determine the Hansen solubility parameters (HSP) for both polymers and pigments.