In this work, the method of highly efficient conversion of l-rhamnose to 5-methylfurfural (MF) catalyzed by various catalysts in a biphasic system was developed. To enhance the MF yield, the effects of the catalyst species, reaction temperature (150–180 °C), extraction solvents and volume ratio of the extraction to the aqueous phase (0–5) on the conversion of l-rhamnose to MF were systematically investigated. Under optimal conditions, a high MF yield of 94% was achieved in the biphasic “diisopropyl ether (DIPE) + H₂O” system due to the fact that the extraction of MF to the DIPE phase significantly inhibits the condensation and degradation of MF in water. Finally, detailed reaction energetics and chemical structures of intermediates of the l-rhamnose dehydration to MF were investigated using the B3LYP level of theory and the SMD solvation model. It is evident that MF, which exhibits excellent chemical stability, harbors the potential to function as a bio-derived platform chemical within the domain of the green industry.

To improve the deteriorated performance caused by CO₂ release during the curing process of traditional moisture‐crosslinked polyurethane or polyurea and poor flame retardancy, this work realized an effective in situ crosslinking technique triggered by moisture for poly(urethane‐urea) with intrinsic flame retardancy, through the incorporation of trimethoxysilane and phosphorus groups via a continuous two‐stage process. Moisture‐triggered crosslinking reaction of trimethoxysilane groups resulted in the establishment of a robust Si─O─Si network, as confirmed by Fourier transform infrared spectroscopy (FTIR) test. The structure transformation considerably enhanced the material’s strength, with the stress at break increasing from 1.0 to 3.2 MPa and modulus from 32.9 to 46.9 MPa. The flame retardant properties of PUUS1 (poly(urethane‐urea) sample) were investigated through limiting oxygen index (LOI) and cone calorimeter (CCT) analysis, demonstrating satisfactory flame resistance, as evidenced by high LOI value of 29%, high char yield of 46.2%, and controlled smoke production. Combining thermogravimetric analysis‐infrared spectrometry (TG‐IR), X‐ray photoelectron spectroscopy (XPS), and flame retardant performance, it is speculated that the generation of phosphorus‐free radical scavengers in gas phase from diethyl bis(2‐hydroxyethyl) aminomethyl phosphonate (DBHAP), coupled with the barrier effects of charred layer and distinctive Si─O─Si framework in condensed phase inhibited combustion and toxic gas emission. The results highlight the successful synthesis of a moisture‐crosslinkable poly(urethane‐urea) with intrinsic flame retardancy, promising for applications necessitating moisture‐crosslinkable materials with superior flame resistance.

The electromagnet is the most used driving device for hydraulic valves; especially the proportional electromagnet with constant force characteristics is the basis for the excellent control performance of hydraulic valves. However, the constant force characteristics of the proportional electromagnet are related to many parameters and are difficult to obtain. In view of the above problems, this paper designs a proportional electromagnet for driving hydraulic valves with the goal of constant force characteristics, with the minimum variance of the output electromagnetic force in the working range as the condition. Firstly, this paper introduces the working principle of proportional electromagnets and establishes the model of electromagnetic force. Then, the influences of the basin bottom radius, the guide angle width and the basin mouth depth on the constant force characteristics of the electromagnet were studied by the finite element method (FEM). Their values are found respectively to give the electromagnet constant force characteristics. Finally, the test bench of the electromagnet was built, and its constant force characteristics and output characteristics were continuously tested. The results show that the test results of the output electromagnet force are highly consistent with the simulation results and have constant force characteristics. Related research deepens the understanding of how the key parameters affect the constant force characteristics, and helps designers optimize these parameters to develop new structures, which have certain practical engineering values.