A photocrosslinkable melt processible acrylonitrile terpolymer as carbon fiber precursor

Covalent organic framework functionalized smart membranes with under-liquid dual superlyophobicity for efficient separation of oil/water emulsions

The smart membrane with under-liquid dual superlyophobicity, which can achieve on-demand separation of oil/water emulsions only by simple liquid pre-wetting, is of essential value for the treatment of complicated real oil/water systems. Here, we first fabricated a stable suspension of imine-linked covalent organic framework nanospheres (TPB-DMTP-COF), and subsequently fabricated COF functionalized smart membranes with under-liquid dual superlyophobicity by immersing polyacrylonitrile-based (PAN-based) membranes into TPB-DMTP-COF nanosphere suspension. Accordingly, effective switchable separation of both oil-in-water and water-in-oil emulsions by TPB-DMTP-COF/PAN membranes can be achieved by employing pre-wetting processes (both the oil contact angle under water and the water contact angle under oil are over 150°). Specifically, the separation flux and the separation efficiency are higher than 1200 L/m2‧h and 98.0 %, and 2100 L/m2‧h and 97.4 % for the surfactant-stabilized oil-in-water and water-in-oil emulsions, respectively. Furthermore, the ultralow adhesions in liquid contributed to the outstanding reusability and antifouling resistance of the prepared TPB-DMTP-COF/PAN membranes. This work provides a feasible approach for fabricating a smart membrane with under-liquid dual superlyophobicity for oily wastewater treatment.

Melt-Spinnable Polyacrylonitrile-An Alternative Carbon Fiber Precursor

The review summarizes recent advances in the production of carbon fiber precursors based on melt-spun acrylonitrile copolymers. Approaches to decrease the melting point of polyacrylonitrile and acrylonitrile copolymers are analyzed, including copolymerization with inert comonomers, plasticization by various solvents and additives, among them the eco-friendly ways to use the carbon dioxide and ionic liquids. The methods for preliminary modification of precursors that provides the thermal oxidative stabilization of the fibers without their melting and the reduction in the stabilization duration without the loss of the mechanical characteristics of the fibers are discussed. Special attention is paid to different ways of crosslinking by irradiation with different sources. Examples of the carbon fibers preparation from melt-processable acrylonitrile copolymers are considered in detail. A patent search was carried out and the information on the methods for producing carbon fibers from precursors based on melt-spun acrylonitrile copolymers are summarized.

Controlling the elasticity of polyacrylonitrile fibers via ionic liquids containing cyano-based anions

As the predominant precursor for high-performance carbon fiber manufacturing, the fabrication of polyacrylonitrile (PAN)-based composite fibers attracts great interest. Ionic liquids (ILs) have recently been investigated for melt-spinning of ultrafine PAN fibers. The plasticizing properties of ILs are significantly affected by the structure of ILs and can be influenced by electronegativity, steric effects, etc. Herein, we report a facile strategy to control the elasticity of the PAN/ILs fibers by tuning the anion structure of ILs. Particularly, the ILs containing nitrile-rich groups exhibited enhanced plasticizing effect and nucleating ability on dissolving PAN components, achieving highly stretchable PAN/ILs fibers.

Highly stretchable PAN/ILs fibers were fabricated through melt-spinning with ionic liquids containing cyano-based anions.

N,N′-Substituted acryloamidines – novel comonomers for melt-processible poly(acrylonitrile)-based carbon fiber precursors

Novel, melt processible PAN-based CF precursors preparedviathe copolymerization of acrylonitrile withN,N′-substituted acryloamidines and their transformation into carbon fibers is presented.

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

A synthesis of acrylonitrile (AN)/butyl acrylate (BA)/fumaronitrile (FN) and AN/EHA (ethyl hexyl acrylate)/FN terpolymers was carried out by redox polymerization using sodium bisulfite (SBS) and potassium persulphate (KPS) as initiator at 40 °C. The effect of comonomers, BA and EHA and termonomer, FN on the glass transition temperature (T_g) and stabilization temperature was studied using Differential Scanning Calorimetry (DSC). The degradation behavior and char yield were obtained by Thermogravimetric Analysis. The conversions of AN, comonomers (BA and EHA) and FN were 55%-71%, 85%-91% and 76%-79%, respectively. It was found that with the same comonomer feed (10%), the T_g of AN/EHA copolymer was lower at 63 °C compared to AN/BA copolymer (70 °C). AN/EHA/FN terpolymer also exhibited a lower T_g at 63 °C when compared to that of the AN/BA/FN terpolymer (67 °C). By incorporating BA and EHA into a PAN system, the char yield was reduced to ~38.0% compared to that of AN (~47.7%). It was found that FN reduced the initial cyclization temperature of AN/BA/FN and AN/EHA/FN terpolymers to 228 and 221 °C, respectively, in comparison to that of AN/BA and AN/EHA copolymers (~260 °C). In addition, FN reduced the heat liberation per unit time during the stabilization process that consequently reduced the emission of volatile group during this process. As a result, the char yields of AN/BA/FN and AN/EHA/FN terpolymers are higher at ~45.1% and ~43.9%, respectively, as compared to those of AN/BA copolymer (37.1%) and AN/EHA copolymer (38.0%).

Effects of drawing process on the structure and tensile properties of textile-grade PAN fiber and its carbon fiber

Carbon fibers (CFs) were prepared using low-cost, textile-grade polyacrylonitrile fibers, which were 200% to 400% drawn in a hot water bath at 90°C or/and in a tubular furnace at 180°C. X-ray diffractograms confirmed that the drawing process led to higher crystallinity and molecular orientation. These fibers were stabilized in a convection oven at 25–255°C for 390 min. After stabilization, carbonization was performed to obtain carbon fibers. The tensile strength of CFs without drawing was ∼0.8 GPa; however, CFs with 200% and 200% drawing in a hot water bath at 90°C and in a tubular furnace at 180°C, respectively, showed a tensile strength of ∼1.7 GPa. These results suggest that the drawing process of precursor fibers affected the tensile properties of the resulting CFs significantly.

Fabrication and Properties of Carbon Fibers

This paper reviews the research and development activities conducted over the past few decades on carbon fibers. The two most important precursors in the carbon fiber industry are polyacrylonitrile (PAN) and mesophase pitch (MP). The structure and composition of the precursor affect the properties of the resultant carbon fibers significantly. Although the essential processes for carbon fiber production are similar, different precursors require different processing conditions in order to achieve improved performance. The research efforts on process optimization are discussed in this review. The review also attempts to cover the research on other precursor materials developed mainly for the purpose of cost reduction.