Polyimide fibers prepared by a dry‐spinning process: Enhanced mechanical properties of fibers containing biphenyl units

Wang, Shihua; Dong, Jie; Li, Zhentao; Xu, Yuan; Tan, Wenjun; Zhao, Xin

doi:10.1002/app.43727

Cited by 13 publications

(8 citation statements)

References 21 publications

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“…It can be observed that a wide dispersion peak occurred at about 2 θ = 24.7°, indicating that a certain ordered crystalline structure has been formed during the solidifying and imidizing process of PAA. The degree of crystallinity of PI nanofibers was 23.56%, which was higher than that of most as-spun PI fibers [ 35 ] due to the flexibility of ODA units in PI molecules. The crystallinity of PI nanofibers fabricated by SBS method might contribute to their strong mechanical properties.…”

Section: Resultsmentioning

confidence: 99%

Preparation of Solution Blown Polyamic Acid Nanofibers and Their Imidization into Polyimide Nanofiber Mats

Song

et al. 2017

Nanomaterials

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Solution blow spinning (SBS) is an innovative process for spinning micro/nanofibers. In this paper, polyamic acid (PAA) nanofibers were fabricated via a SBS apparatus and then imidized into polyimide (PI) nanofibers via thermal process. The morphology and diameter distributions of PAA nanofibers were determined by scanning electron microscope (SEM) and Image Tool software, the processing parameters, including PAA concentration, solution feeding rate, gas pressure, nozzle size, and receiving distance were investigated in details. The fourier transform infrared spectroscopy (FTIR) was used to characterize the chemical changes in the nanofibers after thermal imidization. The results showed that the solution concentration exhibited a notable correlation with spinnability, and the formation of bead defects in PAA nanofibers. Solution feeding rate, gas pressure, nozzle size, and receiving distance affected nanofiber production efficiency and diameter distribution. The average diameters of fibers produced ranged from 129.6 to 197.7 nm by varying SBS parameters. Precisely, PAA nanofibers with good morphology were obtained and the average diameter of nanofibers was 178.2 nm with optimum process parameter. After thermal imidization, the PI nanofibers exhibited obvious adhesion morphology among interconnected fibers, with an increased average diameter of 209.1 nm. The tensile strength of resultant PI nanofiber mat was 12.95 MPa.

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Section: Resultsmentioning

confidence: 99%

Preparation of Solution Blown Polyamic Acid Nanofibers and Their Imidization into Polyimide Nanofiber Mats

Song

et al. 2017

Nanomaterials

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“…The pristine and O 2 plasma treated PI filaments were fixed on a glass plate and dipped with 10 wt % PAA solution by a coating technology, followed by thermal imidization using the following process: (1) Heating to 80 °C (5 °C/min) and annealing for 1.5 h; (2) heating to 120 °C (5 °C/min) and annealing for 1 h; (3) heating to 160 °C (5 °C/min) and annealing for 1 h; (4) heating to 350 °C (5 °C/min) and annealing for 1 h; (5) cooling down to room temperature [30,31,32,33]. The manufactured composites had a thickness of ~100 um, and the fiber volume fraction in the composites was ~30%.…”

Section: Methodsmentioning

confidence: 99%

High-Performance Polyimide Filaments and Composites Improved by O2 Plasma Treatment

Lin

Tang³

et al. 2018

Polymers

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Abstract:Interface issues urgently need to be addressed in high-performance fiber reinforced composites. In this study, different periods of O 2 plasma treatment are proposed to modify twist-free polyimide (PI) filaments to improve hydrophilicity and mechanical and interfacial properties. Feeding O 2 produces chemically active particles to modify the filament surface via chemical reactions and physical etching. According to the X-ray photoelectron spectroscopy (XPS) results, the PI filaments exhibit an 87.16% increase in O/C atomic ratio and a 135.71% increase in the C-O functional group after 180 s O 2 plasma treatment. The atomic force microscope (AFM) results show that the root mean square roughness (Rq) of the treated PI filaments increases by 105.34%, from 38.41 to 78.87 nm. Owing to the increased surface oxygenic functional groups and roughness after O 2 plasma treatment, the contact angle between treated PI filaments and water reduces drastically from the pristine state of 105.08 • to 56.15 • . The O 2 plasma treated PI filaments also demonstrate better mechanical properties than the pristine PI filaments. Moreover, after O 2 plasma treatment, the adhesion between PI filaments and poly(amic acid) (PAA) is enhanced, and the tensile strength of the polyimide/poly(amic acid) (PI/PAA) self-reinforced composites increases from 136 to 234 MPa, even causing the failure mode of the composite changes from adhesive failure to partly cohesive failure.

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“…The structure of PI filaments was characterized by WAXD and is shown in Figure 4 are responsible for the outstanding mechanical properties of PI-H filaments. 23,31 Straight tensile properties of the PI monofilament Typical stress-strain curves and the tensile properties of the PI monofilaments are plotted in Figure 5 and summarized in Table 2. The tensile behaviors of the three PI monofilaments are quite different from each other.…”

Section: Structure Of Pi Filamentsmentioning

confidence: 99%

Structure, property and knittability of polyimide filaments with various strength and modulus

Lin

et al. 2018

Textile Research Journal

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This paper presents an experimental investigation on the knittability of various polyimide (PI) filaments, namely PI-H (high strength and modulus), PI-M (moderate strength and modulus) and PI-L (low strength and modulus) filaments. The tensile strength of the PI-H, PI-M and PI-L filaments is 3.41, 1.65 and 0.88 GPa, and the Young’s modulus is 92.94, 40.71 and 9.43 GPa, respectively. The chemical compositions and structures of various PI filaments were characterized to explain the mechanical performance differences. The results show that the imidization degree, structural crystallinity and orientation have significant effects on the mechanical behaviors of PI monofilaments. The filament forces during the knitting process are simplified into straight tensile, loop tensile and abrasion actions, which have been tested and analyzed on PI monofilaments. A home-made simulative knittability analyzer was designed to test the knittability of the PI filaments. A hand flat knitting machine was used to verify the validity of the simulating methods and the constructed knittability analyzer. The PI-H, PI-M and PI-L filaments have poor, moderate and excellent knittability, respectively. The results also demonstrate that the simulating methods and the constructed simulative knittability analyzer are reasonable and efficient to evaluate the knittability of PI filaments.

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Polyimide fibers prepared by a dry‐spinning process: Enhanced mechanical properties of fibers containing biphenyl units

Cited by 13 publications

References 21 publications

Preparation of Solution Blown Polyamic Acid Nanofibers and Their Imidization into Polyimide Nanofiber Mats

Preparation of Solution Blown Polyamic Acid Nanofibers and Their Imidization into Polyimide Nanofiber Mats

High-Performance Polyimide Filaments and Composites Improved by O2 Plasma Treatment

Structure, property and knittability of polyimide filaments with various strength and modulus

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