Jianming He,Shaoying Liu,Dongliang Chen,Gongying Wang,Qingyin Wang
Melamine formaldehyde fiber is widely used in various fields because of its excellent heat resistance and flame-retardant properties. In this study, melamine and paraformaldehyde are used as the main raw materials, 2,2′-bis(trifluoromethyl)benzidine (TFMB) is successfully introduced into the molecular chain. The TFMB modified spinning solutions (MF-TFMB) are obtained by one-step copolymerization, the TFMB-modified melamine-formaldehyde fibers (MFF-TFMB) are prepared by dry spinning. The surface contact angle and surface energy are measured by a contact angle measuring instrument. The thermal stability and mechanical properties of the fibers are measured by a thermogravimetric analyzer and a single-fiber strength tester. The results show that the introduction of the TFMB group reduces the surface free energy of the polymer and effectively improves the heat resistance and mechanical properties of the fiber. When the addition amount of TFMB is 3%, the MFF-TFMB-3% fiber has smooth surface and bubble-free inside, the breaking strength is 2.25 cN/dtex and the elongation at break is 11.85%. The limiting oxygen index is 32.5%, and the mass loss rate is decreased from 63.88% to 51.36% at 400°C. The fiber has excellent thermal stability and flame-retardant properties.
Crosslinking is a crucial step to keep fibrous morphology and improve ceramic yield in the fabrication process of SiC fibers. Comparing with the oxygen crosslinking, thermal crosslinking can reduce the introduction of oxygen within fibers. In this study, a novel method for preparing the SiC fibers was proposed by combining dry spinning and thermal crosslinking. The spinning solution was prepared by blending a low-molecular-weight (~ 1000 Da) polycarbosilane (PCS) with polyisobutene (PIB) as spinning additive, acrylic acid (AA) as crosslinking agent, and 2,2'-Azobis (2,4-dimethyl) valeronitrile (ABVN) as initiator. The crosslinking mechanism, morphology, composition and microstructure, and mechanical properties of fibers were investigated. The results showed that the morphology of AA-containing PCS fibers was well preserved at 300 ℃ with a low heating rate (0.5 ℃/min), while PCS fibers without AA exhibited the melting or deformation. The crosslinking reaction between C = C groups in AA-containing PCS and Si–H bonds in PCS was triggered by ABVN. Furthermore, AA-containing PCS green fibers experienced pyrolysis at 1100 ℃ and then were annealed at 1500 ℃ (denoted as SiC-1500). SiC-1500 fibers, with an average diameter of 10.47 ± 0.50 μm and average tensile strength of 1.35 ± 0.65 GPa, have a smooth surface and relative dense structure. But SiC-1500 fibers were still an amorphous structure due to the suppression of graphite phase for the growth of β-SiC grains. This work not only breaks through the limitations that only uses high-molecular-weight PCS for dry spinning, but also successfully combines dry spinning and thermal crosslinking technology to obtain SiC fibers. Graphical abstract
This article reports an innovative method for using flexible, extremely sensitive double-layer composite fibers in thermal response sensors. A double-layer fiber sensor with dual corresponding effects is prepared by assembling poly(methyl methacrylate) (PMMA) and graphene layers using dry spinning. The sensor achieves sensitive thermal deformation ability by utilizing the bimetallic sheet principle and the difference in thermal expansion performance between the two materials. The sensor can respond to light stimuli by doping the graphene layer with TiO2 and TiN. The reduced graphene oxide (rGO)/PMMA double-layer fiber thermal response sensor prepared by the chemical reduction of graphene has a fast response ability. When the relative temperature changes from 20 to 50 °C, the sensor response time averages within 2 s, and the bidirectional curvature change rate of the fiber material can reach a maximum of 300%. The sensor exhibits real-time, sensitive electrical performance changes under the stimulation of moisture or light temperature, demonstrating excellent stability and recyclability. Weaving double-layer fibers into two-dimensional (2D) fabrics and monitoring environmental temperature through changes in sensor deformation and electrical properties lays a solid theoretical foundation in thermal sensing and intelligent fabrics.
危险品化学品经营许可证（带存储）