Mei Wan,Congling Shi,Lei Chen,Lei Deng,Yueping Qin,Honglei Che,Jingyun Jing,Junyi Li,Xiaodong Qian
Ammonium polyphosphate (APP) is the most commercially valuable phosphorus-based flame retardant, but poor interaction with the polymer interface limits the flame-retardant efficiency. In this work, a new type of multi-layered nanomaterial coating APP (APP-PEI@MXene@ZIF-67) was prepared and introduced into thermoplastic polyurethane (TPU) polymers by a simple and green assembly strategy. The effects of different loading shells of modified APP on the flame retardancy of TPU composites were investigated, as well as their gas/condensed phase thermal degradation products and their flame-retardant mechanisms. The results showed that APP-PEI@MXene@ZIF-67 was more favorable for catalytic char formation than APP, and the residual char formed by its composites was denser and more continuous. Compared with the pure TPU, the pHRR, THR, pSPR, and TSP of TPU/APP-PEI@MXene@ZIF-67–2BL composites were decreased by 72.75 %, 87.25 %, 59.58 %, and 85.97 %, respectively, which significantly reduced the heat and smoke release during the combustion process. The gas-phase and condensed-phase flame retardant mechanisms synergized to construct a possible approach to address the fire risk and heat/smoke hazards of TPUs and promote the extensive application of TPU polymers.
Renbo Wei,Kexin Liu,Yongxian Liu,Zaixing Wang,Yayao Jiao,Qi Huo,Xiufu Hua,Lingling Wang,Xun Wang
With the increasing application of electronic devices, absorption-dominated electromagnetic interference shielding materials (EMISM) have garnered significant attention for preventing secondary electromagnetic pollution. In this study, polyethyleneimine (PEI)-modified MXene (PEI@MXene) is fabricated and achieved its controlled distribution on the pore walls of polyarylene ether nitrile (PEN) porous films via the phase inversion method (PIM) to obtain a closed porous skeleton of MXene on the pore walls (CPS–MPW). The resulting PEI@MXene/PEN composite film (CFx) exhibited absorption-dominated EMIS efficiency (EMISE). Attributing to the strong interaction between PEI and the hydrophilic segment of amphiphilic Pluronic F127, with its hydrophobic segment anchored by the PEN matrix, PEI@MXene is directionally distributed on the pore walls of CFx. In addition, resulting from the cladding of MXene with PEI and isolating it with closed honeycomb pores, the obtained CFx are insulators without forming a conductive network. As a result, these CFx demonstrate absorption-dominated EMISE with the highest SE T of 41.2 dB and coefficient A higher than 0.51. Further continuous hot pressing of CFx results in thinner and denser films with an impressive specific EMISE up to 750 dB cm −1 . The successful fabrication of these CPS–MPW-type CFx with absorption-dominated EMISE provides a reference for developing and preparing novel EMISM.
In recent years, electrophoretic deposition (EPD) MXene nanoparticles have been used to improve the interface performance of high modulus carbon fiber (HMCF) composites. However, the traditional cathodic electrophoretic deposition technique causes carbon fibers to oxidize, which affects the strength of the carbon fibers themselves. The unstable and easily decomposable characteristics of MXene nanosheets particularly limit the effectiveness of improving the interface performance of thermoplastic polyetheretherketone (PEEK) composites. This study adopts the cathodic electrophoretic deposition process to reduce the damage to carbon fibers; it introduces a temperature-resistant antioxidant polyethyleneimine (PEI), and combines MXene with it through hydrogen bonds and electrostatic interactions to prepare a water-based PEI/MXene nanoparticle dispersion with positive surface charge and excellent thermal stability. These nanoparticles meet the requirements of the cathodic electrophoretic deposition process and the processing of HMCF/PEEK composites. The surface energy of PXM-HMCF is 174.93 % higher than that of D-HMCF. PMX provides a rigid mechanical locking structure at the interface and a flexible modulus transition layer, which increases the interlayer shear strength (ILSS) of PMX-HMCF/PEEK composites to 70.66 MPa, which is 63.22 % higher than that of D-HMCF/PEEK (43.29 MPa). The bending strength of PMX-HMCF/PEEK composites also increases by 22.77 %.
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