Poly (acrylonitrile – co -1-vinylimidazole): A new melt processable carbon fiber precursor

Abstract

Carbon fiber polymer composites have attracted worldwide interest in sporting goods and aerospace industries due to their excellent specific strength, stiffness and lightweight. The replacement of solution-spinning process by melt-spinning process is one of the major approaches to make cost effective carbon fiber. In recent years, researchers have explored the possibilities to synthesize melt processable carbon fiber precursors, but their thermal stabilization is still a challenge. The goal for this research project is to prepare melt processable carbon fiber precursors which have the capability of thermal stabilization. Acrylonitrile/1-vinylimidazole (AN/VIM) copolymers containing various mol% of VIM were synthesized by free radical solution polymerization. The copolymers were characterized by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, 1 H-NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). 82/18 mol percent of AN/VIM copolymer based carbon fiber precursor was processed by melt spinning at 192 °C and thermal stabilization of the melt-spun fiber was achieved by heating in air at 250 °C for 5 hrs. The change of fiber structure during stabilization process was confirmed with ATR-IR spectra. Tan Delta value of the stabilized fiber is 0.17, which is much lower than that of as-spun fiber, about 2.12. The oxidized fiber (250 °C / 5 h) did keep its shape after carbonization at 1000 °C for 2 h, which indicates that poly (acrylonitrile-co-1-vinylimidazole) melt-spun fiber after thermal stabilization can be carbonized. A novel dispersion polymerization of poly (acrylonitrileco-1iii vinylimidazole) by using small amount of protonated copolymer itself as a stabilizer was also introduced in this study. Poly (acrylonitrileco-1-vinylimidazolium tetrafluoroborate) and poly (acrylonitrileco-1-vinylimidazolium hexafluorophosphate) were synthesized for gas separation membranes. Terpolymers of methyl methacrylate, methyl acrylate and furfuryl methacrylate (MMA/MA/FMA) were synthesized successfully by solution polymerization and emulsion polymerization and were characterized by 1 H NMR, ATR-IR and DSC. The thermo-reversible property of MMA/MA/FMA and BMI cross-linked polymer was confirmed by solubility test. The MMA/MA/FMA and BMI cross-linked polymer emulsion can be applied for making thermally re-moldable carbon fiber composite. iv DEDICATION I dedicate this work to my parents. I am blessed for being their daughter. v ACKNOWLEDGMENTS I want to deeply thank Prof. Dennis W. Smith, Jr. for his tremendous support throughout my graduate study. I would like to express gratitude to Prof. Rhett C. Smith for his guidance and help. I would like to thank my committee members, Prof. Stephen. E. Creager, Prof.

Synthesis and Thermal Properties of Acrylonitrile/Butyl Acrylate/Fumaronitrile and Acrylonitrile/Ethyl Hexyl Acrylate/Fumaronitrile Terpolymers as a Potential Precursor for Carbon Fiber

“…Oxidation reactions undergo elimination of hydrogen and addition of oxygen. Meanwhile, the cyclization process leads to the formation of a ladder-like structure in the PAN molecule [ 12 , 13 ]. However, the rapid and exothermic process during cyclization causes sudden volatile loss which breaks the chains and damages the fiber structure [ 14 ]; consequently, causing mass loss.…”

Plasticization for melt viscosity reduction of melt processable carbon fiber precursor

“…The samples were each individually evaluated at varying ratios to the bulk polymer while being tested on the DSC, TGA, and capillary rheometer while keeping the molar ratio of AN to VIM in the bulk polymer at 82:18 AN/VIM (28). The original AN/VIM copolymer shows a T g of 115 °C, and with the addition of the plasticizer additives, the T g changes with the amount of additive used.…”

“…Poly(acrylonitrile-co-1-vinylimidazole) (AN/VIM) copolymers [25,26] have been reported by several researchers, especially of recent publications by Deng, et. al., where they reported the possibility of these copolymers could be used as precursors for carbon fibers without using UV treatment [28]. VIM comonomer can disrupt PAN crystallinity to make it melt-processable, while the unsaturated pendant imidazole groups enable the precursor to be thermally crosslinkable.…”

“…VIM comonomer can disrupt PAN crystallinity to make it melt-processable, while the unsaturated pendant imidazole groups enable the precursor to be thermally crosslinkable. Also, VIM will help in balancing the atomic ratio of nitrogen to carbon (N/C) which is related to microstructure of these precursors and further affects the structure and mechanical properties of carbon fibers [27][28][29].…”

Preparation and thermal properties of polyethylene-based carbonized fibers

“…However, due to the high cost of petroleum-based precursors and their associated processing costs, carbon fiber remains a specialty product and as such has been limited to use in high-end aerospace, sporting goods, automotive, and specialist industrial applications [5][6][7].…”