Properties Of Polyacrylonitrile Fibers Research Articles

Processing, structure and properties of polyacrylonitrile fibers with 15 weight percent single wall carbon nanotubes

For the first time, a polyacrylonitrile (PAN) fiber with up to 15 wt% single-wall carbon nanotubes (SWNTs) was produced by dry-jet wet-spinning while maintaining good SWNT individualization. These fibers exhibited a tensile modulus of 32.1 GPa, tensile strength of 0.8 GPa, and axial electrical conductivity of 2.2 S/m. This was possible by using SWNTs that were non-covalently wrapped with poly (methyl methacrylate) (PMMA-SWNTs). Furthermore, this non-covalent PMMA functionalization significantly reduced the amount of solvent and time needed for processing of the spinning solution, as compared to the methods used in prior studies. Rheology of the spinning dispersions and mechanical properties and structural parameters of the produced fibers were related to the filler individualization, filler content and presence of filler-matrix interaction. Potential applications of this PAN fiber with high SWNT loading are briefly discussed.

Simultaneously electrochemical exfoliation and functionalization of graphene nanosheets: Multifunctional reinforcements in thermal, flame‐retardant, and mechanical properties of polyacrylonitrile composite fibers

AbstractFunctionalized graphene has a promising prospect in improving the thermal, mechanical, and flame‐retardant properties of polymer composites, which was unfortunately limited by the low yield and high pollution during graphene production. In this study, we reported a facile and eco‐friendly electrochemical approach to prepare ferric diethylenetriaminepentakis (methylphosphonic acid) functionalized graphene nanosheets (FGNS), which were subsequently used to fabricate polyacrylonitrile (PAN) composite fibers by a wet spinning strategy. Composite fibers showed better thermal stability above 350°C in contrast to pure PAN. Furthermore, a significant improvement on flame‐retardant properties of PAN fibers in the case of peak heat release rate (decreased by 36.7%) was caused by the inclusion of FGNS. The analysis results of condensed phase revealed that FGNS facilitated the formation of the compact and graphitic char residues, protecting underlying composite fibers during combustion. With adding 3.0 wt% FGNS, the tensile strength and breaking elongation of PAN composite fibers achieved 67.6% and 126.5% increment, respectively. This electrochemical method provides an eco‐friendly approach for scale production of functional graphene.

The influence of stabilization efficiency on skin–core structure and properties of polyacrylonitrile fibers

In this paper, we report the efficient preparation of polyacrylonitrile-based carbon fibers (CFs) by increasing the stabilization temperature and shortening the stabilization time. The oxidized fibers (OFs) were firstly prepared from precursor fibers (PFs) with different diameters at high stabilization efficiency. The skin–core structure of the obtained OFs was studied by optical microscopy, scanning electron microscopy, atomic force microscopy and nanoscale infrared laser spectroscopy, which revealed that fine denier PFs were more suitable for high-efficient stabilization treatment. Moreover, fine denier PFs were stabilized using four different temperature profiles, and then carbonized under stationary processing conditions to fabricate CFs with different stabilization efficiencies. The skin–core structure, crystallite thickness and mechanical properties of the obtained CFs were tested by scanning electron microscopy, Raman spectra, wide-angle X-ray diffraction and tensile testing methods. Noteworthily, T400-grade CFs were achieved and the manufacturing time was reduced by increasing stabilization efficiency, thus lowering the production costs of CFs.

Preparation and properties of polyacrylonitrile fibers with guanidine groups

The polyacrylonitrile (PAN) fibers grafted with guanidine groups were prepared by hydrolyzing with sodium hydroxide solution followed by reacting with polyhexamethylene guanidine hydrochloride (PHGC). The grafting degree could be controlled by changing the treatment time of hydrolyzed PAN fibers with PHGC. The chemical composition and morphology of the modified PAN fibers were characterized by Fourier transform infrared spectroscopy (FTIR), Elemental analysis (EA), X-ray photoelectric spectroscopy (XPS) and scanning electron microscope (SEM). The results showed that the guanidine groups were effectively grafted on the fibers. The water contact angle of the surface modified PAN fibers was reduced and moisture regain was improved significantly with the immobilization of PHGC on the fibers. Furthermore, the modified PAN fibers exhibited favorable acid dyeability at low temperature (50 °C) over a wide pH range and good mechanical properties. The simple and applicable synthesis process provides a new avenue for modification of PAN fibers with improved hydrophilicity and acid dyeability.

Study on Structure and Properties of Polyacrylonitrile Fiber Modified by Hydrazine Hydrate

In this study, the flame-retardant PAN fiber with good moisture absorption, good mechanical properties and better thermal properties has been prepared by blending solution of sodium hydroxide and hydrazine hydrate. FTIR spectra presented that new amide and cyclization-crosslinked pyridine group band peaks appeared. X-ray diffraction showed that the the crystal structure of PAN fibers has been converted from quasicrystalline structure into partially crystallized structure after modification treatment. SEM micrographs indicated that the original longitudinal surface microgroove has changed to layered structure by surfical etchant.

Effect of Solvent Residuals on the Structure and Properties of Polyacrylonitrile Fibers

In order to study the effect of solvent residuals on structure and properties of polyacrylonitrile fibers, the morphology, crystallinity and thermal properties of the fibers were discussed by Electron Microprobe Analysis, X-Ray Diffraction and DSC Analysis. It showed that the cross-section of the fibers with a lower solvent residual tends to be circular. The higher the solvent residuals are, the lower the crystallinity of the fibers and the bigger the crystal size. With the increase of solvent residual, the initial temperature of the fibers’ exothermic peak is in advance and the terminal temperature lags behind, the peak temperature increases, and the heat release also increases. Excessive solvent residuals make the heatrelease reaction very violent and the heatrelease increases. The ladder-shaped cyclation structure formed during the preoxidation process often breaks down because of the instant vast heatrelease.

Effects of positive and negative stretching on the structure and properties of polyacrylonitrile fibers in the pre-oxidation process

Polyacrylonitrile (PAN) fibers were pre-oxidized in a temperature range of 180-275<TEX>$^{\circ}C$</TEX>. The effects of positive and negative stretching on the structure and morphology of PAN fiber in the pre-oxidation process were studied by FTIR spectroscopy, XRD, and SEM. Mechanical property changes were also investigated. No changes in the movement and intensity of functional groups of PAN fibers were caused by positive stretching of up to 10% and negative stretching down to -8%. The crystal structure can be affected by the positive stretching and negative stretching. The maximum strength is 479.81 MPa when the stretching is positive, and the maximum strength is 420.55 MPa when the stretching is negative.

Effect of spinning conditions on the mechanical properties of polyacrylonitrile fibers modified with carbon nanotubes

AbstractCarbon nanotubes (CNTs) were used to modify polyacrylonitrile (PAN) polymer. The PAN/CNT composite fibers were spun from dimethylformamide solutions containing different types of CNTs. The effect of nanotube addition to the fiber precursor on the resulting mechanical properties is discussed. In this study, we examined the relationship of the rheological properties of PAN spinning solutions containing various types of CNTs and the tensile strength of the resulting PAN fibers. The presence of CNTs in the PAN spinning solution enhanced its deformability during the drawing stage. This effect resulted in a higher tensile strength in the fibers containing nanotubes, as compared to the pure fibers. The use of a three‐stage drawing process resulted in a significant increase in the tensile strength of PAN fibers modified with multiwalled nanotubes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Change in the properties of polyacrylonitrile fibre in replacement of itaconic acid in the copolymer by acrylic acid

Change in the properties of polyacrylonitrile fibre in replacement of itaconic acid in the copolymer by acrylic acid

Some reasons for the origin of instability in thermal and thermo-mechanical properties of polyacrylonitrile fibres

-- Industrial polyacrylonitrile fibres which have been prepared by the thiocyanate method are characterized by considerable instability in thermal and thermo-mechanical properties. -- Lack of constancy in such technological parameters as itaconic acid content of the polymer, temperature and concentration of the precipitation bath, and stretch ratio exert a considerable effect on the stability of thermal and thermo-mechanical properties. -- Stabilization of these investigated parameters will obviously make it possible to significantly reduce instability and mechanical properties of carbon fibres.

The effect of modification on structure and dynamic mechanical behavior during the processing of acrylic fiber to stabilized fiber

AbstractPolyacrylonitrile (PAN) fibers pretreated with potassium permanganate have reduced the time required for stabilization, and also improved mechanical properties of the resultant carbon fibers. In this study, the effect of modification on the stabilization process and the dynamic mechanical properties of PAN fibers have been examined. The beta peak appeared at about 125°C on the loss tangent curves caused by molecular motion in the PAN fiber. Appearing at about 254°C, the alpha peak is attributed to chemical reactions and molecular motion in the formation of the crystalline phase of stabilized fibers. The alpha peak of the modified PAN fiber had lower absorption and had a smaller peak in the temperature range of 212–239°C. This indicated that potassium permanganate acts as a catalyst to lower the reaction temperature by about 20°C of the initial cyclization reaction. The dynamic storage modulus analysis indicated that modified PAN fibers have a lower initial transition temperature and that formation of the ladder polymer is gradual and steady.

Defect content and nonuniformity in mechanical properties of polyacrylonitrile fibres

Defect content and nonuniformity in mechanical properties of polyacrylonitrile fibres have been investigated in the cross section of tow and over the length of individual elementary fibres.

Reasons for the retention of long-term antistatic properties of polyacrylonitrile fibre which has been modified at the gel stage with polyethylene glycol-9 diacrylate

The reasons for the resistance of the antistatic properties of polyacrylonitrile fibre, which has been modified at the gel stage with a polyethylene glycol diacrylate, to boiling washes have been investigated. It has been suggested that the retention of the antistatic effect is caused by the manifestation of a cryptoheterogeneity effect under the washing conditions and by the possibility of migration of the antistat from the fibre pores into its surface under definite drying conditions.

Relative length of the spinneret channel as a factor in the properties of polyacrylonitrile fibre

Relative length of the spinneret channel as a factor in the properties of polyacrylonitrile fibre

Properties of polyacrylonitrile fibres modified with a biomass of microorganisms, and of the products processed from the fibres

Properties of polyacrylonitrile fibres modified with a biomass of microorganisms, and of the products processed from the fibres

Effect of stretching on the elastic properties of polyacrylonitrile fibres

Effect of stretching on the elastic properties of polyacrylonitrile fibres

Properties of polyacrylonitrile fibre modified with fibroin

Properties of polyacrylonitrile fibre modified with fibroin

The influence of the macrostructure on the properties of polyacrylonitrile fibre

The influence of the macrostructure on the properties of polyacrylonitrile fibre

Fibres from co-polymers of acrylonitrile and isoprene

In an earlier communication the writers reported that they had spurt fibre with good abrasion resistauce and cyclic bending strength from mixtures of polyacrylonitrile (PAN) and nitrile rubber /I/. It was assumed that the introduction of diene monomer units into the co-polymer molecule would also improve the elastic properties of PAN fibre. The writers have now produced fibre from these co-polymers for the first time. It was spurt in an aqueous dimethyl formamide bath from 15% dimethyl formamide solutions on small laboratory equipment.