Yunbo Zhang,Bing Wang,Yiang Du,Wei Li,Quzhi Song,Yingde Wang
Employing inorganic nanofillers as reinforcements to modify the mechanical and electromagnetic properties of organic materials has been documented to be an extremely efficient method. Herein, an inorganic BN nanosheet (BNNS) was employed to promote the mechanical performance and optimize the crystal structure of ceramic BN materials. First, spinnable hybrid BNNS/polyborazine precursors with different mixing ratios were synthesized by high-temperature polymerization. The exfoliation and amine-functionalization of BNNSs were achieved by ball milling before they were doped into pure borazine monomer (PMAB) through a deamination reaction. The results demonstrate that the dopant of modified BNNS (aBNNS) promotes the ceramic yield of hybrid precursors (up to 66.3%) without destroying fiber spinnability. HP-0.05% shows optimal spinnability with low flow activation energy (1.04 kJ/mol). The finest diameter of green fibers spun by them could reach 5.61 µm, with a smooth and integral surface. Then the influence of aBNNS on the fiber micro-structure and mechanical performance was also measured. It is found that aBNNS benefits the improvement of fiber density (from 1.6 to 2.0 g/cm 3 ), and significantly enhances the crystallinity from 66.65% to 94.28%. Thus, the strength is increased by nearly 60% (up to 1.2 GPa) and the Young's modulus is increased by about 72% (up to 125.0 GPa). The incorporation of trace BNNS offers new insight and potential for the preparation of high-performance BN fibers.
Yiang Du,Bing Wang,Wei Li,Quzhi Song,Changwei Shao,Cheng Han,Yingde Wang
Synthesis of spinnable precursors with high ceramic yield is a crucial issue in BN fibers manufacturing by polymer-derived ceramics (PDCs) route. Spinnability and high ceramic yield are the basis of precursor processability, formability, and mechanical properties. Herein, based on DFT simulation, we designed and synthesized a novel polymer precursor poly[2-propylamino-4,6-bis(methylamino) borazine-co-tri(methylamino) borazine] (PPMAB) via a facile one-pot copolymerization strategy. The random copolymerization model of condensations was obtained through DFT calculation. The molecular chain structure, molecular weight, and molecular weight distribution were optimized by adjusting the synthesis conditions. The precursor PPMAB-1:1 with a high ceramic yield of 62.43% and concentrated molecular weight distribution (PDI < 1.3) was obtained. Rheological performance research revealed the excellent and stable spinnability of PPMAB-1:1 by the tunable viscosity and low flow activation energy (23.61 kJ/mol). As a demonstration of spinnability, continuous BN fiber with a fine diameter (>10 km, 7.60 ± 1.13 μm, and 1.6 GPa) was obtained after melt spinning. The present work effectively improved the ceramic yield and spinnability of polyborazine precursors. Simultaneously, it can be used extensively as a universal method to prepare multifunctional copolymers with precise structure control.
危险品化学品经营许可证（带存储）