Application of the NQR method for studying polymer materials

Ab Initio Calculation of 81Br Nuclear Quadrupole Resonance Transition Frequencies for Brominated Aromatics (Flame Retardants)

“…The use of quantum chemical calculations to interpret nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and gas-phase microwave spectra has a rich history. − Recent attention to NMR chemical shift calculations demonstrates a renewed interest for calculation of NMR properties. − Less attention has been focused on calculation of NQR transition frequencies, despite the widespread use of NQR spectroscopy in the study of materials containing 2 H, − 17 O, , 27 Al 1 , 14 N, 63 Cu/ 65 Cu, , 93 Nb, 35 Cl, ,, 209 Bi, 23 Na, and 81 Br. , Of particular interest in this work are brominated aromatics, including flame retardants, recently studied by 81 Br NQR spectroscopy . High-impact polystyrene (HIPS), used in manufacturing computer monitors, televisions, and business and electrical equipment, is made less flammable by the inclusion of up to 30% by mass brominated aromatics…”

Development and relaxation of internal stresses in granular composites with an epoxy matrix

“…Under uniform all-round compression of the crystals by a pressure p, the frequency increases at a constant rate (∂ν/∂p) T = (369 ± 2) Hz/MPa. The value of the coefficient (∂ν/∂p) T is almost independent of temperature [2]. Another advantage of this indicator substance is the cubic structure of its crystal lattice, which allows Cu 2 O particles to be considered as isotropic bodies under uniform all-round compression and heating.…”

“…where V is the molar volume [2]. Experiments were performed with a stepwise change in the parameters of external action on the tested material sample; therefore, to describe the stress development and relaxation in the matrix using Eqs.…”

“…The articles are subjected to annealing to relieve technological and shrinkage stresses. However, subsequent cooling leads to the development of significant stresses in the heterogeneous matrix-filler system [1,2]. These stresses cannot be relieved by annealing or by different methods.…”