Polyacrylonitrile solution homogeneity study by dynamic shear rheology and the effect on the carbon fiber tensile strength (original) (raw)
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2012
Polyacrylonitrile (PAN)/acrylamide (AM) fibers were fabricated via dry-jet wet spinning process using a solvent-free coagulation bath. The effects of AM loading as comonomer on the mechanical and thermal properties of PAN-based carbon fiber have been studied. The thermal stability and mechanical stability of the fibers were characterized using differential scanning calorimetry (DSC) and tensile testing. Fibers fabricated from PAN with 5 wt% AM had the highest Young Modulus at 5.54 GPa. It also showed better exothermic trend process with broader exothermic peak and lower initiation stabilization temperature compared with homopolymer PAN. The elemental composition and chemical structure evolution of the fibers during the heat treatment processes were evaluated by elemental analyzer and Fourier Transform Infrared Spectroscopy. Crystal structure evolution of the fibers during the heat treatment process was elucidated by X-ray diffraction (XRD) analysis. The elemental analyzer, XRD and FTIR results revealed that pyrolysis process used had successfully transformed PAN/AM fibers produced from solvent free coagulation bath into carbon fibers that were comparable with the conventional coagulation bath.
Structural features of polyacrylonitrile-based carbon fibers
Journal of Materials Science, 2011
The structural changes as functions of spinning conditions and heat treatments were investigated with respect to the structural feature of PAN-based carbon fibers by scanning tunnelling microscopy (STM). The distinct granule structure on the cross section of both high tensile strength (HS) and high modulus (HM) carbon fibers was observed by SEM, while slender granule-shape domain on the longitudinal surface was revealed by STM. A structure model was proposed, which depicted that the PAN-based carbon fiber was a heterogeneous structure composed of aggregated mesostructural domains. These domains were closely arranged into spiral form along fiber axis, allowing the fibers have high strength and good elongation. The initial shape and size of domains was determined by the precursor composition and spinning conditions and also strongly depended on the heat-treated temperature and stretching conditions. The smaller or slender domain, the higher tensile strength obtained for fibers. We expect that the PAN-based carbon fiber with better performance should be produced by optimizing the size and shape of these domains.
LATEST ADVANCEMENTS IN CARBON BASED FIBER, A REVIEW
Universal interest in Carbon fiber composites are reflected in manufacturing capability that is increasing day by day. Carbon fiber reinforced polymers (CFRPs) are one the stiffest and lightest composite materials. They are much persuading than other traditional materials. Carbon fibers are from the family of advanced composites materials. This paper is mainly related to the research and development stages of carbon fiber of last few years. Two most predominant precursors are e.g. (Polyacrylonitrile (PAN), Mesophase Pitch (MP)) are in carbon-fiber industry. The structure of Carbon fiber and composition of utilized precursors is directly related with properties of resultant carbon fiber. The production processes of carbon fibers are same and according to requirement, different precursors are used for different processing conditions. This paper represents the review related with various process optimizations, and also tries to cover the study on some other precursor materials development, mostly for the cost reduction. Moreover , carbon fiber composites fabrication techniques, applications and properties are also discussed herewith.
Journal of Applied Polymer Science, 1995
The progression of polyacrylonitrile (PAN) fibers on multistage stabilization stage has been monitored by following the variations in density, elemental composition, morphological aspect, and mechanical properties. The effects of various processing conditions during the multistage stabilization on the mechanical properties of final carbon fibers were evaluated in detail. To achieve an optimal extent of stabilization of PAN fibers is critical as the final mechanical properties of carbon fibers are concerned. This aim can be realized by adjusting and matching the temperatures in each step and the processing rates during multistage stabilization. Imposing stretching on multistage stabilization is beneficial to mechanical properties of carbon fibers.
Fibers
The aim of this work is to review a possible correlation of composition, thermal processing, and recent alternative stabilization technologies to the mechanical properties. The chemical microstructure of polyacrylonitrile (PAN) is discussed in detail to understand the influence in thermomechanical properties during stabilization by observing transformation from thermoplastic to ladder polymer. In addition, relevant literature data are used to understand the comonomer composition effect on mechanical properties. Technologies of direct fiber heating by irradiation have been recently involved and hold promise to enhance performance, reduce processing time and energy consumption. Carbon fiber manufacturing can provide benefits by using higher comonomer ratios, similar to textile grade or melt-spun PAN, in order to cut costs derived from an acrylonitrile precursor, without suffering in regard to mechanical properties. Energy intensive processes of stabilization and carbonization remain a...
Carbon Fibers: Precursor Systems, Processing, Structure, and Properties
Angewandte Chemie International Edition, 2014
This Review gives an overview of precursor systems, their processing, and the final precursor-dependent structure of carbon fibers (CFs) including new developments in precursor systems for low-cost CFs. The following CF precursor systems are discussed: poly(acrylonitrile)based copolymers, pitch, cellulose, lignin, poly(ethylene), and new synthetic polymeric precursors for high-end CFs. In addition, structure-property relationships and the different models for describing both the structure and morphology of CFs will be presented. Scheme 1. Synthesis of a typical terpolymer consisting of acrylonitrile, methyl methacrylate, and itaconic acid (AN/MMA/IA).
Structure-property model for polyethylene-derived carbon fiber
Carbon, 2016
This paper presents a structure-property model for carbon fiber derived from a polyethylene (PE) precursor that relates tensile modulus to the elastic properties and angular distribution of constituent graphitic layers, as measured using wide-angle x-ray diffraction of individual carbon fiber filaments. The observed relationship and interpretation of data using a uniform-stress model has revealed fundamental differences in the nature of the microstructure present in carbon fiber produced from polyethylene compared to carbon fiber produced from polyacrylonitrile (PAN) or pitch precursors. Specifically, it was found that the shear modulus, indicative of the shear between adjacent graphitic layers of the carbonized fiber is lower for polyethylene-derived carbon fiber than for PAN-or pitch-derived carbon fiber, suggesting that the covalent CC sp 3 crosslink density connecting adjacent graphitic layers in PE-derived carbon fiber is reduced. This structure that is less crosslinked is anticipated to be easier to orient during carbonization and high-temperature graphitization processes, yielding a highly oriented structure necessary for high tensile modulus.
Materials, 2014
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