Polyacrylate elastomers have enormous application potential in various fields. However, facile and universal synthetic strategies remain rare for ultrastretchable polyacrylates (especially those with extension ratios ≥50) that are adaptable to various building blocks. Here, we develop a novel chain lubrication strategy to reduce the interchain friction and improve the slip of polymer chains during deformation. By constructing polyacrylates with soft, hard, and quaternary ammonium segments, we fabricate ultrastretchable elastomers (extension ratios up to 323) through emulsion polymerization and film casting, using quaternary ammonium surfactants (QASs) as emulsifiers. The lubricating mechanism of QASs is explored by varying the chemical structures of QASs, and it is demonstrated that QASs enhance the fluidity of polymer chains while forming eutectics with quaternary ammonium segments to construct physical cross-linking sites in the polymer networks. We also demonstrate the successful synthesis of a variety of ultrastretchable elastomers by replacing soft and hard segment monomers or surfactants, confirming the effectiveness and generalizability of the chain lubrication strategy. The chain lubrication strategy promises to pioneer new methods for fabricating highly ductile elastomers and advancing industrial rubbers.
Third-generation advanced automotive medium-Mn steel, which can replace 22MnB5 steel, was newly developed to improve the lightweight and crashworthiness of automotive. Studies on the formability and simulation method of medium-Mn steel have just been initiated. This study elucidated the effects of initial forming temperature (IFT) on formability, thickness distribution, macro mechanical property and micro performance of medium-Mn steel hot-formed products. Results show that the IFT intensely affects the formability and the thickness distribution of the deep drawing zone on the medium-Mn steel hot-formed part, and the recommended IFT range is between 400 °C and 500 °C.
Summary The classical bond‐based peridynamic (BPD) model is limited with a fixed Poisson's ratio. To overcome this limitation, an improved BPD model is proposed to analyze the deformation and crack propagation of microelastic brittle materials with emphasis on varying Poisson's ratios. In the proposed model, the bond is subjected to axial and transverse pairwise forces, and the particle rotation angle is added to eliminate the additional bending moment caused by transverse forces, which is a key factor to satisfy the balance of angular momentum exactly. As a result, the bond not only has axial displacement but also has transverse displacement and particle rotation. This extension in the displacement mode overcomes the limitation of the fixed Poisson's ratio in the classical BPD model. The simulation results demonstrate the precision of the improved BPD model and prove its ability to predict deformations and crack propagations.
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