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Efficient and sustainable disposal of waste rubber remains an extreme challenge worldwide due to the huge quantities and non-biodegradable structures. Although many self-healable and reprocessable rubbers have been designed to overcome the challenge, these rubbers are elaborately synthesized and still industrial waste rubbers are not reutilized in their synthesis. Herein, waste natural rubber powders (WNRPs) are re-crosslinked by disulfide bond-containing polysulfide rubber (PSR) via a thiol–ene reaction to produce a self-healable and reprocessable reclaimed rubber. Increasing the PSR content is beneficial for conversion and crosslinking density, but it decreases mechanical properties. The produced reclaimed rubber can self-heal its damage at 100 °C for 24 h, and the recovery of mechanical properties is more than 90%. Moreover, the reclaimed rubber is still reprocessable at 100 °C for 12 h, and the recovery of mechanical performance exceeds 95%. More importantly, both virgin and self-healed and reprocessed reclaimed rubbers can withstand the repeated running over of a 2.0-T automobile, and the weight loss is less than 0.2% after 200 times. Therefore, this self-healable and reprocessable reclaimed rubber not only is synthesized by reusing huge amounts of waste rubbers, but also exhibits wide applications in damping materials due to its low cost. [ABSTRACT FROM AUTHOR]

Developing aqueous stable and catalytic Ti3C2Tx MXene suspensions remains a grand challenge. MXene nanosheets always undergo rapid degradation when exposed to water and oxygen, and the incorporation of reducing or capping agents may deteriorate the intrinsic characteristics of MXenes. Here, we coupled dialdehyde xylan (DAX) with MXene nanosheets to significantly increase the long-term storage of MXene in an aqueous solution (>3 months) with a dramatic enhancement of their room temperature catalytic activity for ultrafast gelation. DAX can form thick and smooth layers on the nanosheets via multiple hydrogen bonds, providing a reduction environment to prevent the occurrence of oxidation. Meanwhile, DAX can accelerate the generation of free radicals from the potassium persulfate (KPS)/MXene pair, reducing the polymerization time of vinyl monomers from ∼30 min to ∼90 s. Moreover, the DAX layer is capable of serving as additional crosslinks by leveraging Schiff base bonds with chitosan (CS), with the elongation at break increasing from 100% to 909%. The resultant MXene-based hydrogel can be further explored as a sustainable sensor for real-time physical signal monitoring. This work offers an enticing prospect for the development of eco-friendly and high-performance MXene-based materials. [ABSTRACT FROM AUTHOR]

The modeling method of the pogo system of launch vehicles with a staged combustion cycle engine is mainly limited to the transfer matrix modeling method, which contains transcendental functions that are difficult to solve. A state-space modeling method for the pogo system of launch vehicles with a staged combustion cycle engine is proposed in this paper. First, the second-order differential dynamic equation of the gas path is constructed by approximating the exponential term in each element of the gas path with Taylor expansion and inverse Laplace transformation. Second, the liquid and gas paths are combined in the form of mass flow to establish the second-order dynamic equation of the propulsion system. Third, the state-space equation of the coupled system is obtained by combining the structural and propulsion systems. Finally, an example of a propulsion system is modeled using the transfer matrix modeling method and the proposed method to verify the correctness of the proposed method, and the stability of the model is analyzed when the parameters of the accumulator and gas path change. The major contributions are as follows: 1) the proposed method is a systematic method that is universally applicable to the pogo analysis of a launch vehicle with a staged combustion cycle engine; 2) the proposed method inherits the advantages of Rubin's state-space method for liquid rockets. [ABSTRACT FROM AUTHOR]

A method for deriving a non-singular state-space formulation based on Rubin's model for Pogo analysis is presented in this study. Because of the non-singularity, the state-space model can be directly used in frequency-domain analyses and time-domain simulations. To describe the assembly method concisely, the dynamic equations of the nine types of independent elements are described in a standard manner. The nine types of elements are divided into two classes according to characteristics of the dynamic equations. The mapping relationship between the local and global numbers of elements and nodes is obtained by numbering all of the elements and nodes. By integrating the element stiffness matrixes to obtain the total stiffness matrix used in the finite element method, the coefficient matrixes of the improved Rubin's model are assembled from the coefficient matrixes of all of the elements according to the mapping relationship. Based on the non-singular model, the time-varying simulation with the nonlinear property of the accumulator can be done conveniently by revising the state-space model. The successful application of this method to a Pogo analysis of a certain type of CZ rocket used in China verifies the correctness and efficiency of the method of this study. [ABSTRACT FROM AUTHOR]