Probing molecular mobility during crosslinking process of commercial resins by NMR multiexponential relaxation data analysis

Abstract

ABSTRACT:In this study, we present the experimental results for the crosslinking process of a commercial polyester resin based on measurements of the spin lattice relaxation time T 1 of protons, as function of the crosslinking time evolution. Multiexponential decomposition of the evolution of magnetization measured in inversion-recovery experiments is performed. The population of ''rigid'' and ''mobile'' nuclear spin sites was estimated as function of time evolution. In analogy to the usual monomer conversion u, site conversion from ''mobile'' to ''rigid'' sites u M were also estimated as a function of time evolution and initial concentrations of the reagents. The multiexponential decomposition approach of T 1 relaxation data allows one to follow crosslinking processes.

Nuclear spin relaxation in liquids and gases

“…Centomo et al 308 studied water-swelling of copolymer matrices using, among other techniques, proton T 1 and T 2 measurements at a (single) low magnetic field. Campello and co-workers 309 followed the process of cross-linking of a commercial polyester resin ''on the fly'' using different catalyst-to-resin ratios. They reported results of 1 H inversion-recovery and CPMG experiments under low-resolution conditions, as a function of the curing time, and analyzed the data as biexponential processes.…”