Electron Spin Resonance Imaging and ATR−FTIR Study of Poly(acrylonitrile−butadiene−styrene) Containing a Hindered Amine Stabilizer and Thermally Treated at 353 K

Synthesis of anti-photolysis lignin-based dispersant and its application in pesticide suspension concentrate

In the formulation of pesticide Suspension Concentrate (SC), some photosensitive pesticides are easily decomposed in the preparation. In this study, a hindered amine modified lignosulfonate (SL-Temp) with anti-photolysis function was synthesized using 4-amino-2,2,6,6-tetramethylpiperidine (Temp) and Sodium Lignosulfonate (SL) to solve this problem. The obtained SL-Temp was used as a dispersant to prepare 5% SC of avermectin, which shows good physical stability. The decomposition rate of the avermectin in SC after accelerating hot storage is 0%, which is much lower than 6.1% when SL was used as the dispersant. After being exposed to UV irradiation for 60 hours, the highest retention rate of avermectin is 87.1% when SL-Temp was used as the dispersant, which is much higher than 73.6% when SL was used as the dispersant, and also higher than 76.3% when a small molecule antioxidant (BHT) was added to the formulation. QCM-D studies revealed that the SL-Temp adsorption layer on avermectin particles can compete to absorb partial ultraviolet rays, hinder the penetration of ultraviolet light, and scavenge the free radicals produced by photooxidation, so as to protect avermectin from degradation.

Hindered amine grafted lignosulfonate was synthesized and used as functional dispersant in suspension concentrate of photosensitive pesticide avermectin.

Deducing 1D concentration profiles from EPR imaging: a new approach based on the concept of virtual components and optimization with the genetic algorithm

Application of the genetic algorithm (GA) in conjunction with the concept of virtual components (VC) to determine 1D concentration profiles from EPRI spectra (images) is described. In this approach the concentration profile is expressed as the superposition of virtual components described by analytical functions of the Gaussian and Boltzmann type. The method was implemented in the computer program ACon, which allows for fully automated profile extraction via the nonlinear least-squares fitting of experimental images. The parametric sensitivity of the GA internal parameters such as population size, probabilities of the crossover, mutation and elitist retention to the search space was investigated in detail in order to find their optimal settings. The customized genetic algorithm was evaluated using simulated and experimental test data sets and its performance was compared with the Monte Carlo approach.

Spatial distribution of stabilizer-derived nitroxide radicals during thermal degradation of poly(acrylonitrile–butadiene–styrene) copolymers: a unified picture from pulsed ELDOR and ESR imaging

Double Electron-Electron Resonance (DEER) provides information on the spatial distribution of radicals on the length scale of a few nanometres, while Electron Spin Resonance Imaging (ESRI) provides information on a length scale of millimetres with a resolution of about 100 micrometres. Despite the gap between these length scales, results from the two techniques are found to complement and support each other in the characterization of the identity and distribution of nitroxide radicals derived from the Hindered Amine Stabilizer (HAS) Tinuvin 770 in poly(acrylonitrile-butadiene-styrene) (ABS) copolymers. DEER measurements demonstrate that there is no significant formation of biradicals from the bifunctional HAS, and provide the distributions of local radical concentrations. These distributions are poorly resolved for model-free analysis of the DEER data by the Tikhonov regularization; the resolution was significantly improved by utilizing information obtained by ESRI. DEER data can be fitted with only one adjustable parameter, namely the average radical concentration, if 1D and 2D spectral--spatial ESRI results on both the spatial distribution of nitroxides and their distribution between the acrylonitrile--styrene-rich (SAN) and butadiene-rich (B) microphases are considered.