Xin Zhang,Shanpeng Qiao,Hong Zhang,Bo Wang,Xu Zeng,Bo Ren,Xiaodong Yang
The literature on polyvinyl alcohol (PVA) films is extensive, however, these methods often necessitate intricate synthesis processes or the addition of plasticizers to modify the strength and water solubility of the PVA material. A high-strength UV radiation-resistant composite film by chelating Fe 3+ with lignin and PVA, which exhibits excellent hydrolysis resistance is developed. This composite film is prepared simply by incorporating a small amount of dealkalized lignin (APPL) and ferric chloride (FeCl 3 ) into PVA through a straightforward composite process. During the scanning test, it is noted that the film exhibits a high density of uniformly dispersed particles, endowing it with efficient ultraviolet absorption capabilities. The infrared and anti-dissolution tests reveal that the coordination of Fe 3+ with lignin imparts an outstanding hydrolysis resistance to the film, obviating the need for any extender, curing agent, acid or base. The tensile fracture strength reaches an impressive 187.81Mpa in the tensile test. UV and indicator card tests unequivocally demonstrate that the film achieves a remarkable 100% anti-UV efficiency. This Fe 3+ chelated lignin/PVA composite film, with its facile preparation, environmental sustainability, high strength, and outstanding anti-ultraviolet efficiency, can be deployed across diverse applications requiring robust protection against ultraviolet radiation.
Liu Yang,Deng Zongyi,Zhang Wei,Jiang Guoqin,Cao Wenjing,Huang Zhixiong,Shi Minxian,Li Jian
Lightweight ablative materials are commonly utilized as thermal protection materials for hypersonic vehicles. Ceramizable phenolic aerogel/carbon fiber (PA/CF) composites modified with TiB 2 and B 4 C were fabricated, which had the characteristics of lightweight, high strength, and low thermal conductivity. The acid-catalyzed phenol-aldehyde polymerization reaction was used to significantly shorten the gelation time, which facilitated the uniform distribution of ceramic fillers. The oxygen-consuming, oxygen-blocking, and carbon-fixing synergistic effects of TiB 2 and B 4 C high-temperature ceramic reactions, as well as the multiphase ceramic structure (C-B 2 O 3 -TiO 2 -TiC) formed, conferred excellent thermal stability (the residual weight of 58.8% at 1200 °C), oxidation resistance (the residual strength of 3.44 MPa after static ablation), and ablation resistance (the linear and mass ablation rates as low as 0.045 mm/s and 0.0115 g/s) on the composites. The lightweight, high-strength materials with anti-thermal insulation properties demonstrate significant competitiveness and application potential in the field of thermal protection.
Kexiong Gao,Siyi Tang,Zheng Li,Xin Li,Kun Fan,Haihong Zhu,Longbo Luo,Xiangyang Liu
The fabrication of high strength and toughness in polymeric materials, especially for rigid-chain polymers, has been a long-term technological challenge in high-performance materials design. In this work, the synthesized soluble poly (benzimidazole-terephthalamide) (PABI) acts as a rigid-chain intrinsic polymer. Then, the coordination effect of the HCl with the benzimidazole unit induces more extended PABI chains assembled into a gel network with a liquid crystal-like structure. Finally, the obtained PABI gel is further compressed into a layered film during solvent evaporation. Scanning electron microscopy images reveal that the resultant films present nacre-like morphologies. X-ray diffraction and polarized light microscopy demonstrate the formation of the liquid crystal-like structure. Owing to the highly oriented layers and the self-reinforcement of fibrils in layers, the strength (511.1 MPa) of PABI films increases by 41.7% through altering the gelation time. Ultimately, it reaches a record-high 708.7 MPa by altering HCl content. Meanwhile, the sliding and plastic deformation of amorphous interconnected layers, tearing of fibrils, crack branching, and crack deflection facilitate stable crack propagation and significantly dissipate the energy. Hence, the toughness (136.7 MJ/m 3 ) of PABI films also increases by 23.7% through altering gelation time and remains at a high level under high HCl content. In addition, the highly oriented layered structure unexpectedly imparts PABI films with a high dielectric strength of 686.6 MV/m. Our findings provide a facile strategy for designing high-performance polymeric materials with high strength, toughness, and even more functionality.
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