Fabrication of carbon fibers from the cupric ion impregnated and thermally stabilized poly(hexamethylene adipamide) precursor

2021 ◽  
pp. 152808372110569
Author(s):  
Levent Erzurumluoglu ◽  
Md. Mahbubor Rahman ◽  
Tuba Demirel ◽  
Ismail Karacan
Keyword(s):  
Heating Rate ◽  
Carbon Fibers ◽  
Strong Dependence ◽  
Tensile Modulus ◽  
Thermal Stabilization ◽  
Volume Density ◽  
Amorphous Structure ◽  
Structural Defects ◽  
Heating Rates ◽  
Polyamide 66

The conversion of poly (hexamethylene adipamide) or polyamide 66 precursor fiber to carbon fibers was accomplished through thermal stabilization and carbonization processes. Thermal stabilization was conducted of cupric chloride (CuCl2)–ethanol-impregnated polyamide 66 (PA66) fibers in the air. To determine the influence of heating rate on the fiber structure and properties of the resultant carbon fibers, carbonization experiments were performed at selected temperatures of 500, 700, 900, and 1100°C using 2.5 and 5 °C/min heating rates with no dwelling. The results conclusively revealed that the volume density and tensile properties of the PA66 fiber were higher at 2.5 °C/min heating rate. After fixing the heating rate as 2.5°C/min, further carbonization experiments were conducted at temperatures from 500 to 1100°C, using increments of 100°C with no dwelling time. Linear density, volume density, fiber diameter, carbon yield, elemental composition, tensile, and electrical properties exhibited a strong dependence on the carbonization temperature. After taking into account the effects of structural defects (i.e., microvoids), tensile strength, and tensile modulus of the carbon fibers increased to 794 MPa and 92.4 GPa, respectively, when carbonized at 1100°C. X-ray diffraction analysis of the carbon fibers further revealed the existence of a greatly disordered (i.e., amorphous) structure, which developed during the carbonization process. FT-IR analysis confirmed the formation of highly aromatic carbon clusters at temperatures of 500°C and higher. The outcomes of electrical conductivity in this study confirm that the PA66 precursor was converted into a semi-conducting state once it was carbonized.

scholarly journals CHARACTERIZATION OF CARBON FIBERS DERIVED FROM THERMALLY STABILIZED POLY(HEXAMETHYLENE ADIPAMIDE) PRECURSOR FIBERS

2021 ◽  
Vol 5 (3) ◽  
pp. 48-55
Author(s):  
Mahbubor Rahman ◽  
TUBA DEMIREL ◽  
İsmail Karacan
Keyword(s):  
Carbon Fibers ◽  
Strong Dependence ◽  
Thermal Stabilization ◽  
Processing Parameters ◽  
Volume Density ◽  
Ethanol Solution ◽  
X Ray Diffraction ◽  
Polyamide 66 ◽  
Air Atmosphere ◽  
Disordered Carbon

The thermal oxidative stabilization and carbonization processes of poly(hexamethylene adipamide) or (polyamide 66) fibers were accomplished to transform into carbon fibers. Polyamide 66 fibers were pretreated with a ethanol solution of cupric chloride followed by a stabilization process in the air atmosphere. Carbonization experiments were executed at temperatures of 500, 700, 900, and 1100°C utilizing heating rate of 2.5 °C/min. Carbonization experiments were performed at temperatures between 500 and 1100°C employing the rises of 100°C. X-ray diffraction analysis of the carbon fibers shown a highly disordered carbon structure developed during the carbonization process. The values of fiber diameter, linear density, volume density, carbon fiber yield, elemental analysis, and electrical properties revealed a strong dependence on the carbonization temperature. As an insulating material, the polyamide 66 or PA66 precursor was transformed to a semiconducting stage after the thermal stabilization and carbonization processes. The current study demonstrated how processing parameters influence the structure and characteristics of carbon fibers produced from poly(hexamethylene adipamide) fibers.

scholarly journals Mesophase Pitch-Based Carbon Fibers: Accelerated Stabilization of Pitch Fibers under Effective Plasma Irradiation-Assisted Modification

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6382
Author(s):  
Yuanshuo Peng ◽  
Ruixuan Tan ◽  
Yue Liu ◽  
Jianxiao Yang ◽  
Yanfeng Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Heating Rate ◽  
Carbon Fibers ◽  
High Performance ◽  
Low Cost ◽  
Tensile Modulus ◽  
Mesophase Pitch ◽  
Stabilization Time ◽  
Plasma Irradiation

Stabilization is the most complicated and time-consuming step in the manufacture of carbon fibers (CFs), which is important to prepare CFs with high performance. Accelerated stabilization was successfully demonstrated under effective plasma irradiation-assisted modification (PIM) of mesophase pitch fibers (PFs). The results showed that the PIM treatment could obviously introduce more oxygen-containing groups into PFs, which was remarkably efficient in shortening the stabilization time of PFs with a faster stabilization heating rate, as well as in preparing the corresponding CFs with higher performance. The obtained graphitized fiber (GF-5) from the PF-5 under PIM treatment of 5 min presented a higher tensile strength of 2.21 GPa, a higher tensile modulus of 502 GPa, and a higher thermal conductivity of 920 W/m·K compared to other GFs. Therefore, the accelerated stabilization of PFs by PIM treatment is an efficient strategy for developing low-cost pitch-based CFs with high performance.

Kinetics Study on Non-Isothermal Crystallization of Amorphous Alloy Mg65Cu15Ag10Y10

2011 ◽  
Vol 413 ◽  
pp. 432-438
Author(s):  
Xiao Jun Wang ◽  
Tian Dong Xia ◽  
Xue Ding Chen
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Heating Rate ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Continuous Heating ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Local Activation ◽  
Local Activation Energy

The crystallization kinetics of amorphous alloy Mg65Cu15Ag10Y10has been studied by differential scanning calorimetry in the mode of continuous heating annealing. It is found that both DSC curves and activation energy show a strong dependence on the heating rate. The activation energy for crystallization are determined as 186.1 and 184.4 KJ mol−1for the heating rates β=5-20 Kmin−1, and 107.5 and 110.0 KJmol−1for the heating rates β=20-80Kmin−1, when using the Kissinger equation and the Ozawa equation, respectively. Local activation energy at any volume fraction crystallized was obtained by the general Ozawa's isoconversional method. The average value of local activation energy for heating rates ranging from 5 to 20Kmin−1is 180.9 KJ mol−1and for heating rates ranging between 20 and 80Kmin−1is 110.2 KJ mol−1. Using the Suriñach curve fitting procedure, the kinetics mode was specified. The JMA kinetics is manifested as a rule in the early stages of the crystallization. The JMA exponent,n, initially being larger than 4 and continuously decreases to about 2 along with the development of crystallization. The NGG-like mode dominates in the advanced stages of the transformation. These two modes are mutually independent. The proportion between the JMA-like and the NGG-like modes is related to the heating rate.

scholarly journals Influence of Heating Rate on the Structure and Mechanical Properties of Aromatic BPDA–PDA Polyimide Fiber

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 510 ◽  
Author(s):  
Wenke Yang ◽  
Fangfang Liu ◽  
Hongxiang Chen ◽  
Xuemin Dai ◽  
Wei Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Treatment ◽  
Heating Rate ◽  
Tensile Modulus ◽  
High Mobility ◽  
Polymer Chains ◽  
Degree Of Crystallinity ◽  
High Heating Rate ◽  
Heating Rates ◽  
Polyimide Fibers

Aromatic polyimide fibers (PI) are usually produced in two steps. The precursor fibers of polyamic acid (PAA) are fabricated first, and then the fabricated fibers are converted into PI fibers through thermal treatment. In the second step (thermal treatment), the mechanical properties of the obtained PI fibers are remarkably affected. Here, the PAA fibers derived from 3,3’,4,4’-biphenyltetra-carboxylic dianhydride and p-phenylenediamine are fabricated by a dry-jet wet-spinning method. Then, the PI fibers are prepared by heating PAA fibers from room temperature to 300, 350 and 400 °C under different heating rates, ranging from 1 °C/min to 80 °C/min. When the heating rate is low, the crystallization lags behind the imidization process, and begins only when the imidization degree reaches a high level. As the heating rate increases, the crystallization tends to occur simultaneously with the imidization process, and the degree of crystallinity of the PI fibers also greatly increases. Our findings suggest that a high heating rate causes the polymer chains to undergo high mobility during thermal treatment. The tensile modulus of the PI fiber further demonstrates a high dependence on the heating rate. Moreover, a short annealing process after treatment proves to be efficient in releasing residual stress and improving tensile strength.

scholarly journals Structural Characterization of Thermally Stabilized Poly(acrylonitrile) Fibers by Means of X-ray Diffraction, FT-IR Spectroscopy, and TGA Analysis

2021 ◽  
Vol 5 (2) ◽  
pp. 1-9
Author(s):  
TUBA DEMIREL ◽  
Md. Mahbubor Rahman ◽  
Ismail KARACAN
Keyword(s):  
Color Change ◽  
Thermal Stabilization ◽  
Volume Density ◽  
Amorphous Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ft Ir ◽  
Dehydrogenation Reactions ◽  
Tga Analysis

The structure and effects of thermally stabilized PAN original fibers were characterized utilizing a mixture of volume density, color change observations, flame tests, X-ray diffraction (XRD), infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA) measurements. The results obtained from the analysis of XRD work showed the conversion of the original molecular structure from a highly laterally ordered condition to a disordered amorphous structure. The experimental results acquired from FT-IR analysis indicated rapid and concurrent aromatization and dehydrogenation reactions assisted by the formation of oxygen-containing functional groups. TGA analysis showed a carbon yield of 72% at 1000 °C. The application and use of NH4Br pretreatment are expected to increase the productivity of carbon fiber processing at lowered cost by significantly reducing the processing time necessary for the successful completion of thermal stabilization reactions.

The effects of pre-oxidation heating rate on bio-based carbon fibers and its surface repair

2015 ◽  
Vol 29 (10n11) ◽  
pp. 1540019
Author(s):  
H. Wu ◽  
L. F. Cheng ◽  
S. W. Fan ◽  
X. W. Yuan ◽  
D. Bhattacharyya
Keyword(s):  
Heating Rate ◽  
Carbon Fibers ◽  
Surface Defects ◽  
Rapid Heating ◽  
Low Cost ◽  
Heating Rates ◽  
Positive Role ◽  
Jute Fibers ◽  
Resin Solution ◽  
Surface Repair

Low-cost carbon fibers (CFs) are fabricated from jute fibers after pre-oxidation, carbonization and surface repair. This paper investigates the effects of pre-oxidation heating rate on jute fibers, and explores a repair method for surface defects of CFs in C/C composite. The results show the reaction mechanism of jute fibers in air is not changed at higher pre-oxidation heating rates while a low heating rate is still required as the oxidation of jute fibers cannot be fully achieved under rapid heating. The tensile strength of CFs increases after repair with a 5% phenolic resin solution. Jute-based CFs play a positive role in C/C composite performance through crack bridging and deflection.

The solution curing performance of high-ortho epoxy phenolic fibers

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744090
Author(s):  
Mingli Jiao ◽  
Kai Yang ◽  
Dongxue Ren ◽  
Quan Diao ◽  
Jian Cao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heating Rate ◽  
Carbon Fibers ◽  
Melt Spinning ◽  
Electronic Devices ◽  
Activated Carbon Fibers ◽  
Heating Rates ◽  
Novolac Resins ◽  
Combined Solution ◽  
Characteristic Group

The high-ortho epoxy phenolic fibers (HEPFs) were prepared by the crosslinking of as-spun filaments derived from melt-spinning of the epoxy novolac resins copolymerized among epichlorohydrin (ECH), phenol and formaldehyde, and cured in a combined solution of formaldehyde and hydrochloric acid with a different heating rate. The changes in functional groups, thermal performance and mechanical properties during the different heating rates in solution curing were characterized. The results show that a peak of thermal stability and mechanical properties can be obtained with increasing heating rate, and crosslinking structure and characteristic group have changed after the solution curing. The epoxy phenolic fibers show great potential in the application of elastic flame-resistant textiles, aero-composites and precursors for activated carbon fibers used in electronic devices.

Maximum heating rates for producing undistorted glassy carbon ware determined by wedge-shaped samples

1996 ◽  
Vol 11 (9) ◽  
pp. 2368-2375 ◽  
Author(s):  
Hossein Maleki ◽  
Lawrence R. Holland ◽  
Gwyn M. Jenkins ◽  
R. L. Zimmerman ◽  
Wally Porter
Keyword(s):  
Heating Rate ◽  
Treatment Process ◽  
Gaseous Product ◽  
Pyrolysis Mass Spectrometry ◽  
Heating Rates ◽  
Gaseous Products ◽  
Volatile Products ◽  
Solid Bodies ◽  
Polymeric Carbon ◽  
Maximum Heating

Polymeric carbon artifacts are particularly difficult to make in thick section. Heating rate, temperature, and sample thickness determine the outcome of carbonization of resin leading to a glassy polymeric carbon ware. Using wedge-shaped samples, we found the maximum thickness for various heating rates during gelling (300 K–360 K), curing (360 K–400 K), postcuring (400 K–500 K), and precarbonization (500 K–875 K). Excessive heating rate causes failure. In postcuring the critical heating rate varies inversely as the fifth power of thickness; in precarbonization this varies inversely as the third power of thickness. From thermogravimetric evidence we attribute such failure to low rates of diffusion of gaseous products of reactions occurring within the solid during pyrolysis. Mass spectrometry shows the main gaseous product is water vapor; some carboniferous gases are also evolved during precarbonization. We discuss a diffusion model applicable to any heat-treatment process in which volatile products are removed from solid bodies.

scholarly journals Towards a better representation of the solar cycle in general circulation models

2007 ◽  
Vol 7 (20) ◽  
pp. 5391-5400 ◽  
Author(s):  
K. M. Nissen ◽  
K. Matthes ◽  
U. Langematz ◽  
B. Mayer
Keyword(s):  
Solar Cycle ◽  
Heating Rate ◽  
General Circulation ◽  
Temperature Response ◽  
General Circulation Models ◽  
Short Wave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Heating Rates ◽  
Radiation Scheme

Abstract. We introduce the improved Freie Universität Berlin (FUB) high-resolution radiation scheme FUBRad and compare it to the 4-band standard ECHAM5 SW radiation scheme of Fouquart and Bonnel (FB). Both schemes are validated against the detailed radiative transfer model libRadtran. FUBRad produces realistic heating rate variations during the solar cycle. The SW heating rate response with the FB scheme is about 20 times smaller than with FUBRad and cannot produce the observed temperature signal. A reduction of the spectral resolution to 6 bands for solar irradiance and ozone absorption cross sections leads to a degradation (reduction) of the solar SW heating rate signal by about 20%. The simulated temperature response agrees qualitatively well with observations in the summer upper stratosphere and mesosphere where irradiance variations dominate the signal. Comparison of the total short-wave heating rates under solar minimum conditions shows good agreement between FUBRad, FB and libRadtran up to the middle mesosphere (60–70 km) indicating that both parameterizations are well suited for climate integrations that do not take solar variability into account. The FUBRad scheme has been implemented as a sub-submodel of the Modular Earth Submodel System (MESSy).

BRIDGING OF CARBON FIBERS IN CF/EPOXY COMPOSITES USING ELECTROSTATICALLY INDUCED CNT ALIGNMENT

2021 ◽  
Author(s):  
DANDAN ZHANG ◽  
XINGKANG SHE ◽  
YIPENG HE ◽  
WESLEY A. CHAPKIN, ◽  
VI T. BREGMAN ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Electric Field ◽  
Carbon Fibers ◽  
Hybrid Composites ◽  
Tensile Modulus ◽  
Tensile Tests ◽  
Polymer Mixture ◽  
Ac Electric Field ◽  
Reinforced Polymer ◽  
Electric Field Direction

Carbon fiber reinforced polymer (CFRP) composites are lightweight materials with superior strength but are expensive due to the increased cost of carbon fibers (CFs). The addition of carbon nanotubes (CNTs) to polymer nanocomposites are becoming an excellent alternative to CF due to their unique combination of electrical, thermal, and mechanical properties. With the application of an electric field across the CNT/polymer mixture before curing, CNTs will not only be aligned along the electric field direction, but also form networks after reaching to a certain degree of alignment. In this study, an alternating current (AC) electric field was applied continuously to CNT/CF/Epoxy hybrid composites before curing. By cutting off the applied voltage when the monitored electric current increased, the degree of networking of CNTs between two CF tows was controlled. The relative electric field strength around the end of conductive carbon fiber tows in the epoxy matrix was modeled using COMSOL Multiphysics. It increased after applying AC electric field parallel to the CF tows, thereby increasing the alignment degree of CNTs and building a network to bridge the CF tows. The preliminary results indicate that the microhardness and tensile modulus between two CF tows are increased due to the networking of CNTs in this area. The fracture surface of the specimens after tensile tests were characterized to reveal more details of the microstructure.

Sign in / Sign up

Export Citation Format

Share Document