Four deep eutectic solvents (DESs), namely, glycerol/chlorocholine (glycerol/ChCl), urea/ChCl, citric acid/ChCl, and oxalic acid/ChCl, were synthesized and their performance in the dissolution of cellulose was studied. The results showed that the melting point of the DESs varied with the proportion of the hydrogen bond donor material. The viscosity of the DESs changed considerably with the change in temperature; as the temperature increased, the viscosity decreased and the electrical conductivity increased. Oxalic acid/ChCl exhibited the best dissolution effects on cellulose. The microscopic morphology of cellulose was observed with a microscope. The solvent system effectively dissolved the cellulose, and the dissolution method of the oxalic acid/ChCl solvent on cellulose was preliminarily analyzed. The ChCl solvent formed new hydrogen bonds with the hydroxyl groups of the cellulose through its oxygen atom in the hydroxyl group and its nitrogen atom in the amino group. That is to say, after the deep eutectic melt formed an internal hydrogen bond, a large number of remaining ions formed a hydrogen bond with the hydroxyl groups of the cellulose, resulting in a great dissolution of the cellulose. Although the cellulose and regenerated cellulose had similar structures, the crystal form of cellulose changed from type I to type II.

In this paper, a two-phase system, formed by oxalic acid/choline chloride-based deep eutectic solvent (DES) and chosen extractants, was used as a dissolution–reaction–separation system, and metal chloride was used as a catalyst to study the degradation of cellulose to produce 5-hydroxymethylfurfural (5-HMF) and glucose. The effects of the amount of organic solvent and the reaction temperature on product yield, the repeated recycling of DES, the comparison between a two-phase system and a homogeneous system, and the mechanism of cellulose degradation to 5-HMF were investigated. The results show that ethyl n-butyrate has the best extraction effect on 5-HMF. Compared with the homogeneous system, the yield of 5-HMF and glucose in the two-phase system is significantly improved. At a temperature of 140 °C and a reaction time of 120 min, the yields of glucose and 5-HMF reached the maximum, which were 23.5% and 29.8%, respectively. After DES was reused three times, the yields of glucose and 5-HMF decreased greatly, indicating that the recycling rate of DES was low.

The flame retardant dicyclohexenyl aluminum hypophosphite (ADCP) and nano-silica are added to PA66 to improve flame retardant property of the composite. The flame-retardant property of the composite is tested via oxygen index test, vertical burning test, and cone calorimetry test. Combustion residues are tested using scanning electron microscopy, EDS spectroscopy, and Fourier infrared analysis. Results show that flame-retardant ADCP can effectively promote the formation of a porous carbon layer on the combustion surface of PA66. Nano-silica easily migrates to the material surface to improve the oxidation resistance of the carbon layer and the density of the carbon layer’s structure. It can also effectively prevent heat, flammable gases, and oxygen from entering the flame zone and enhance the flame retardant properties of ADCP.

In this study, nanocrystalline cellulose (NCC) was grafted with lauric acid, palmitic acid, and stearic acid and used as stabilizer to prepare styrene butyl acrylate emulsion. The properties of the emulsion were determined, and the mechanism of modified NCC (MNCC) stabilized emulsion was analyzed. Results showed that long-chain fatty acids were grafted to NCC through esterification initiated at a low temperature. When the dosage of L-MNCC, P-MNCC, and S-MNCC was 0.05%, the styrene-acrylic emulsion had 92.5%, 94.2%, and 96.3% conversion rates, respectively, and exhibited good dilution, pH, Ca2+, and centrifugal stability. The particle size of styrene-acrylic emulsion was approximately 460 nm, and the absolute value of the Zeta potential increased with the MNCC concentration. According to the images of optical microscopy and the transmission electron microscope, the MNCC was adsorbed onto the surface of styrene-acrylic emulsion droplets. The synergistic effect from the electrostatic repulsion of MNCC, the hydrophile lipophilicity of MNCC, and the spatial hindrance of the MNCC adsorption layer provided good stability for the styrene-acrylic emulsion. Therefore, MNCC could replace traditional surfactants in stabilizing emulsion.

Three metal salts of dicyclohexyl hypophosphite, namely dicyclohexyl aluminum hypophosphite (ADCP), dicyclohexyl magnesium hypophosphite (MDCP), and dicyclohexyl zinc hypophosphite (ZDCP), were synthesized. These flame retardants were subjected to thermogravimetric analysis, and the results showed that ADCP and ZDCP had higher thermal stabilities than MDCP. They were then separately mixed with polyamide 66 (PA66)to prepare composite materials, of which the combustion properties were determined by the limiting oxygen index method and horizontal/vertical burning experiments. The mechanical properties of the materials were further evaluated using an electronic universal testing machine. The results showed that all the three flame retardants exerted a flame-retardant effect on PA66, but the flame-retardant effect of MDCP was inferior to those of ADCP and ZDCP. All the composites also showed similar mechanical properties. Among the three flame retardants, ADCP had the best overall performance for raw materials, showing good flame-retardant properties while maintaining the mechanical properties of the raw materials. The optimal dosage of ADCP was 15 wt %, at which a V-0 rating in the vertical burning test (UL 94 test) can be obtained.