Size effect for asphaltene particles in the resin by NMR

© Kazan Federal University (KFU). The resin-asphaltene model systems with different sizes of asphaltenes are studied by nuclear magnetic resonance (NMR) using the solid-echo sequence. For systems with particle sizes of asphaltenes greater than 50 µm, the form of relaxation attenuation consists of two components, one of which is characterized by a typical asphaltene relaxation time of about 20 µs. In this case, the Gaussian form describes the relaxation attenuation of this component, which is typical for the NMR signal in disordered solids. At the same time, it is found that the share of the solid component in the NMR signal decreases with decreasing particle size of asphaltenes. The signal drops to zero when the size of asphaltenes particles reaches 10 microns. Based on the estimates of the rotational motion correlation time for an asphaltene particle in a dispersion medium (resin) with a known viscosity value, the influence of two factors is discussed: the difference in the values of macro-and microviscosity of the resin, as well as the possibility of partial dissolution of asphaltenes particles in the resin. The results of repeated measurements for a long time indicate the existence of a reverse process in the system, leading to the aggregation of asphaltene particles