Search

The development of self‐healing materials is an effective strategy to improve the service life of polymer materials. In this study, self‐healing waterborne fluorinated polyurethane‐acrylate (WFPUA) containing UV‐responsive coumarin groups was prepared by Pickering emulsion polymerization using modified cellulose nanocrystal as a stabilizer. The effect of double bond‐terminated waterborne polyurethane content on emulsion polymerization and latex film properties was mainly studied. Due to the dynamic reversibility of the coumarin groups and the synergistic effect of hydrogen bonds, the optimized sample (WFPUA‐30) had excellent mechanical properties and self‐healing properties. The tensile strength was 5.24 MPa and the elongation at break was 267%. The self‐healing efficiency of tensile strength and elongation at break after 6 h of repair was 86.52% and 93.20%, respectively. In addition, due to the presence of fluorine‐containing groups, the water and oil contact angles of the latex film could reach 101.7° and 82.1°, respectively. This work broadens the way for the manufacture of self‐healing and multifunctional waterborne polyurethane‐acrylates. © 2024 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Pilot‐ignited ammonia‐fueled engines have drawn more and more attention for low carbon emissions compared to traditional diesel engines. The ignition processes of NH3/NC7H16 mixtures under compression ignition engine‐like conditions are numerically investigated. By comparing the ignition delay times (IDTs) calculated by six ammonia mechanisms with experimental data, the Glarborg mechanism is selected. Then, the Glarborg mechanism and the Zhang detailed n‐heptane mechanism are merged into a new mechanism, which is adopted in the present study. Results show that the negative temperature coefficient behavior of the IDTs is only observed as the ammonia mass fraction is 70%. Only temperature has a significant effect on IDTs at all research conditions, and the effect of ammonia mass fraction is significant when the temperature is lower than 1000 K. However, the effects of equivalence ratio and pressure are small, especially at high temperatures, high equivalence ratios, and high pressures. Interestingly, the IDTs are categorized into three regions by temperature and ammonia mass fraction. The sensitivity analysis indicates that the sensitivity coefficients of most reactions associated with ammonia decrease with a decrease in ammonia mass fraction, whereas only R4210 is sensitive to ammonia mass fraction for n‐heptane‐related reactions. Rates of production and consumption (ROP) analyses indicate that the ammonia mass fraction mainly affects the ROPs of NC7H16, NH3, and NNH at low and medium temperatures, whereas the ammonia mass fraction affects the ROP of H2NO before the temperature of 2000 K. The ROPs of NC7H16, NH3, and NNH significantly increase with increasing temperature, whereas the ROP of H2NO slightly increases with increasing temperature. The increase of temperature in the early and middle stages is mainly contributed by the oxidation of n‐heptane, while the increase of temperature in the middle and late stages is mainly contributed by the oxidation of ammonia. [ABSTRACT FROM AUTHOR]

Photo‐responsive cellulose nanocrystal modified fluorinated polyacrylate was synthesized by environmentally friendly RAFT‐mediated Pickering emulsion polymerization using amphiphilic block copolymer modified cellulose nanocrystal poly(acrylic acid)‐g‐CNC‐g‐poly (hexafluorobutyl acrylate‐co‐7‐(2‐methacryloyloxyethoxy)‐4‐methylcoumarin) PAA‐g‐CNC‐g‐P (HFBA‐co‐CMA) (MCNC) as a stabilizer, and the photo‐responsive coumarin groups were introduced to endow it with self‐healing function. This paper mainly studied the effect of MCNC dosage on emulsion polymerization and latex film properties. The latex particle size and its distribution decreased as the MCNC dosage increased from 0.4 wt% to 1.0 wt%, and then increased afterwards. The mechanical property and thermal stability of latex films could be significantly improved by introducing MCNC. And the surface scratches of latex films with MCNC exceeding 0.4 wt% could be completely repaired after 7 h UV irradiation. Furthermore, the photo‐responsive cellulose nanocrystal modified fluorinated polyacrylate emulsion was applied to fabric finishing by dip‐rolling treatment. And the finished fabric had good hydrophobicity, oleophobicity and surface repair performance. [ABSTRACT FROM AUTHOR]