PAN Content Research Articles

Preparation of functionalizable poly(propylene–styrene)/polyacrylonitrile millimeter‐scale particles with core‐shell morphology

AbstractCore‐Shell (CS) polymeric particles have attracted great interest due to their high mechanical, thermal, and chemical stability and their surface properties. In this study, functionalizable CS poly(propylene/styrene)/poly(acrylonitrile) (PP/PS/PAN) particles were prepared through heterogeneous polymerizations in a batch reactor. Commercial PP particles and PP/PS particles (prepared by seeded suspension polymerization of styrene (Sty) on PP spheres) were applied as core components of the final structure, while the shell was prepared through acrylonitrile dispersion polymerization. The degree of swelling of the core particles by Sty played an important role for the adhesion of the PAN shell, which for PP particles was 24 wt%, whereas for PP/PS hybrid particles it was 57 wt%. The particles (PP/PS and CS) were characterized through image analysis, revealing a uniform and smooth surface for PP/PS spheres and a uniform porous shell for CS particles. Particle size distributions, thermal degradation, chemical structures, degrees of crystallinity, and textural properties were also evaluated. The PAN shell adhered to the PP/PS particles without forming a copolymer, and the CS particles formed by a PP/PS core and PAN shell had sizes of 4.54 ± 1.24 mm, specific area of 2.70 m2g−1 and PAN content of 15.98 ± 0.82% (m/m) of total particles.

Prediction of PAN oxidation in a gas turbine bearing chamber using coupled chemical kinetics and CFD simulation of lubricant flow

A Computational Fluid Dynamics (CFD) model, using COMSOL 6.1, was developed in this work to simulate the oil temperature distribution within a bearing housing, to provide a means of predicting the most probable zones for PAN oxidation. Three different zones in the radial direction and two distinct zones in the axial direction were specified with different temperature profiles. It was also found that the rotational speed of the rotor and oil outlet pressure can significantly influence the temperature distribution. Oil inlet temperature was the other factor that had a minor impact on the temperature profile. Furthermore, the highest temperatures were observed in the bulk oil in the area surrounding the rotor. A chemical reaction analysis, which was performed using MATLAB R2022a, was performed to estimate the rate of PAN oxidation. According to the final results; higher rotational speeds increase the rate of oxidation. Moreover, a reduction in revolution speed extends the time required to completely consume the original PAN content. These findings were also used to demonstrate where varnish deposits start to form. Multiple temperature zones were used instead of the average temperature to carefully check the mutual relation between the revolution speed and temperature, and accurately calculate the rate of PAN oxidation reaction.

Facile construction of a core-shell structured metal-organic frameworks nanofiber membrane for removing Co(II) from simulated radioactive wastewater

A novel core–shell structured composite of UiO-66-Tu/PAN nanofiber membranes (NFMs) functionalized with thiourea (Tu) was developed for the efficient separation of Co(II) from simulated radioactive wastewater. Various analytical techniques were employed to characterize the structure and properties of the NFMs. The filtration performance, flux, and hydrophilicity of the membrane were evaluated using a membrane flux tester and contact angle (CA) measurements, respectively. The adsorption performance of UiO-66-Tu/PAN for Co(II) was investigated through batch adsorption experiments. The results indicate that at a UiO-66-Tu/PAN content of 7 %, the UiO-66-Tu/PAN NFMs exhibit better hydrophilicity (CA of 37.8°) and a higher cobalt ion retention rate (77.41 %). Under optimal conditions, the theoretical maximum adsorption capacity for cobalt ions is 51.2 mg/g. X-ray photoelectron spectroscopy (XPS) analysis was utilized to clarify the adsorption mechanism of Co(II) by the 7 %UiO-66-Tu/PAN composite, showing a coordination mechanism that involves the participation of oxygen, nitrogen, and sulfur atoms in the ligand. In addition, the material also demonstrates excellent radiation stability (50–100 kGy). It should be pointed out that this is the first time that metal–organic frameworks (MOFs) core–shell nanofibers membranes have been used for cobalt ion separation. The development of this new material effectively addresses the challenges associated with using MOFs as powdered adsorbents, achieving efficient purification of wastewater and providing important engineering significance for the treatment and disposal of trace amounts of 60Co radioactive wastewater.

Recommending instead of taking down: YouTube hyperpartisan content promotion amid the Brazilian general elections

AbstractYouTube released a global commitment to reduce the spread of problematic content by actively recommending “trusted” news sources on their platform but did not disclose the criteria used to classify the reputation of channels and the list of trusted news sources favored by the company. We aim to understand the patterns of recommendation by YouTube's algorithm and identify what the platform classifies as “reliable informative sources.” In our experiment, we performed 205 tests on YouTube's recommendation system, simulating the behavior of new Brazilian users with no historical data on the platform looking for reliable news throughout the elections. We documented the Brazilian media groups that were suggested on the homepage, further analyzing the presence, position and content of Jovem Pan videos, Brazil's flagship conservative media group. We identified that, far from reigning in extremist content, YouTube systematically prioritized Jovem Pan and did not actively take down toxic Jovem Pan content. Our findings indicate that YouTube magnified the imbalance between candidates' portrayals, exposing the regulatory asymmetry between broadcast media and online platforms in the country. In spite of the opaque commercial agreements and business strategies, the platform's recommendation decisions may have an “advertising effect” of sponsorship and endorsement on users.

Membranes Based on Cellulose and Copolymers of Acrylonitrile Prepared from Joint Solutions.

Cellulose and copolymers of acrylonitrile (PAN) are characterized by their chemical resistance to several conventional solvents. Therefore, these polymers are often used to obtain membranes for the recovery of such solvents. In this work, for the first time, composite membranes formed from highly concentrated mixed solutions based on cellulose and PAN are considered (the total content of polymers is 18 wt.%). For mixed solutions, the morphology and rheological behavior were evaluated. It is shown that the resulting solutions are two-phase, and their morphology depends on the components' ratio and the system's history. The non-monotonous change in the viscosity with the PAN content indicates a specific interaction of cellulose and PAN in N-methylmorpholine-N-oxide solutions. The rheological behavior of mixed solutions allows for their processing in conditions identical to those of cellulose solutions. The introduction of PAN into the cellulose matrix promotes a decrease in the structural order in the system, affecting the membranes' transport properties. For composite membranes, it was found that with an increase in the content of the PAN phase, the retention of Remazol and Orange decreases, while the observed values are several times higher than those for cellulose membranes. The permeability of ethanol increases with increasing terpolymer content.

Impedance-matched (hydroxylated nano-BN/reduced graphene oxide) @Fe3O4/polyaniline composite for efficient microwave absorption and thermal management

A microwave absorbing composite material with good thermal conductivity has been prepared to solve the problem of electromagnetic wave pollution in high-power density electronic equipment without increasing the heat load of the equipment. Herein, we prepared the quaternary absorbing material hydroxylated boron nitride nanosheets (BN-o)/reduced graphene oxide (r-GO) @Fe3O4@polyaniline (PAn) (BCFA) and adjusted the content of PAn to enhance the impedance matching and modulate the microwave absorption effect. At a PAn content of 40 wt%, the absorber exhibits admirable microwave absorption performance, the lowest reflection loss (RLmin) of −54.72 dB and effective microwave absorption bandwidth (RL < −10 dB, EAB) of 3.12 GHz at a thickness and frequency of 3.5 mm and 7.2 GHz, respectively. The excellent microwave absorption is due to a suitable mechanism of dielectric and magnetic losses and the excellent impedance matching of the absorber. Moreover, the high thermal conductivity and phonon transport properties of the BN-o/r-GO van der Waals heterostructure give the composite thermal conductivity of 1.69 W(m·K)−1 when the BN-o/r-GO content is approximately 14 wt%. Therefore, BCFA has become a candidate material to solve the electromagnetic pollution problem of high-power density electronic equipment.

High performance nanofiber-supported thin film composite forward osmosis membranes based on continuous thermal-rolling pretreated electrospun PES/PAN blend substrates

One of the major challenges facing the practical application of forward osmosis (FO) membranes is the need for high performance. Thus, the fabrication of highly permselective FO membranes is of great importance. The objective of this study was to improve the wettability/hydrophilicity of electrospun nanofiber (ESNF)-based substrates for the fabrication of nanofiber-supported thin film composite (NTFC) membranes for FO application. This study explored the impact of electrospun polyethersulfone/polyacrylonitrile (PES/PAN) nanofibers as the blend support to produce NTFC membranes. The blending of PES/PAN in the spinning dope was optimized. The blending of hydrophilic PAN (0–10 wt%) in PES affects the fiber diameter, hydrophilicity, water uptake, and roughness of the ESNF membrane substrates. Continuous thermal-rolling pretreatment was performed on the ESNF substrates prior to interfacial polymerization for polyamide active layer deposition. The results indicated that the fabricated NTFC membrane achieved significantly greater water flux (L/m2 h) while retaining a low specific salt flux (g/L) compared to traditional TFC membranes. The NTFC membrane flux increased with an increase in PAN content in the ESNF substrate. According to the FO performance results, the NTFC-10 (PES/PAN blend ratio of 90:10) exhibited optimal performance: a high water flux of 42.1 and 52.2 L/m2 h for the FO and PRO modes, respectively, and low specific salt flux of 0.27 and 0.24 g/L for the FO and PRO modes, respectively, using 1 M NaCl as the draw solution. This demonstrated the higher selectivity and water flux achieved by the developed NTFC membranes compared to the traditional TFC membranes.

Structure–property relationship of carbon fibers derived from polyimide/polyacrylonitrile blends

A series of polyimide/polyacrylonitrile (PI/PAN) blend fibers with different PAN weight ratios were prepared through a two-step wet-spinning method and stabilization process and then were carbonized at 1500°C under high-purity nitrogen atmosphere, yielding in PI/PAN-derived carbon fibers. The effects of PAN content on the structures of the PI/PAN blend fibers were systematically investigated. The elemental composition, aggregation structure, carbon yields, and electrical properties of the PI/PAN-derived carbon fibers were also analyzed. The imidization degree and molecular orientation of the PI/PAN blend fibers increased first and then decreased with increasing PAN content, which directly affect the aggregation structures and properties of the corresponding PI/PAN-derived carbon fibers. As a consequence, the carbon fibers derived from PI/PAN-35% exhibited perfect graphite structure with a planar spacing d002 of 0.349 nm, high carbon content of 97.14%, and low electrical resistivity of 1.89 × 10−5 Ω·m, attributing to the high degree of orientation along the fiber axis and low value of φa/ φc in the PI/PAN blend fibers.

The interplay between gelation and phase separation in PAN/DMSO/H2O blends and the resulted critical gels

Isothermal aging experiments are carried out in Polyacrylonitrile/Dimethylsulfoxide/H2O (PAN/DMSO/H2O) blends, and rheological and optical methods are used to investigate the interplay between phase separation and gelation. Two types of gel structures are found. In most samples, gelation is induced by phase separation in PAN concentrated regions, yet it will subsequently slow the kinetics of phase separation down by altering the concentration balance and fluctuation. As a result, the drop of light transmittance becomes slower and a phenomenon called “RT reversal” is observed. At last, the phase separated morphology is replaced by gel structure, which inherits the inhomogeneity in PAN content distribution. Another type of gel grows from homogeneous solution and its structure disperses uniformly in space. Moreover, the temperature dependence of critical gel properties, like its size limits and thermodynamics, is discussed. It is found that the self-similar structure in homogeneous critical gel covers wider length scales and possesses stronger gel stiffness than those of inhomogeneous ones. The activation energy for gelation is also calculated, which reveals no obvious dependence on original PAN concentration or temperature.

PVDF/PAN blend separators via thermally induced phase separation for lithium ion batteries

PVDF/PAN blend porous membranes were prepared via thermally induced phase separation (TIPS) and used as separators for lithium ion batteries. TIPS behavior was investigated in detail to control the morphology, pore size, porosity, and mechanical properties of the blend separators as a function of PAN content. Rod-like pores are the typical structure resulted from solid−solid phase separation, while the pore size and porosity decrease with an increase of PAN in the blend. The introduction of PAN enhances the tensile strength and the thermal stability of the blend separator. The electrolyte uptake and the ionic conductivity reduce correspondingly with the decrease of the pore size and the porosity. However, the graphite/polymer electrolyte/LiFePO4 batteries with the blend separators exhibit higher C-rate performance, and better reversible charge/discharge cycle stability than those with PVDF separators and the commercial Celgard 2400.

조절 라디칼 중합법을 이용한 PAN 함량이 많은 PEO-b-PAN 블록 공중합체의 합성

c2015 The Korean Fiber Society Abstract: Poly(ethylene oxide-b-acrylonitrile) (PEO-b-PAN) block copolymers were prepared as precursors to mesoporous carbons. Redox-initiated radical polymerization and controlled radical polymerization techniques, such as reversible addition-fragmentation chain transfer (RAFT) and activators regenerated by electron transfer atom-transfer radical polymerization (ARGET ATRP), were successfully applied to prepare PEO-b-PAN block copolymers with high PAN content. Radical polymerization of acrylonitrile (AN) using ceric ion as redox initiator gave block copolymers with PEO:PAN ratio of up to 1:38.4, but their high molecular weight and polydispersity index (PDI) indicated that the structure was not controlled. Therefore, in order to achieve better control on the structure of the PAN block, controlled radical polymerization techniques were used. Poly(ethylene oxide) with trithiocarbonate (PEO-CTA) and bromide (PEO-Br) end groups were synthesized as polymeric chain transfer agent for the RAFT process and as initiator for the ATRP process, respectively. The RAFT process of AN using PEO-CTA gave block copolymers with PAN block length 0.53–3.58 times that of the PEO block. Moreover, ARGET ATRP allowed to prepare block copolymers with a very high molecular weight of 72,000, while maintaining a PDI value as low as 1.20.

Preparation and Characterization of Proton Exchange Membrane Based on Sulfonated Poly(arylene ether sulfone)/Polyacrylonitrile (SPAES/PAN)

Sulfonated poly (arylene ether sulfone) s (SPAESs) exhibit good proton conductivity, thermal and mechanical properties, could act as candidates of proton exchange membranes for fuel cells. At the same time, the poor oxidative stability and excessive swelling ratio of SPAESs bring limitations for its further use. In this article, PAN was employed to mix with SPAES, and then SPAES/PAN blend membranes were prepared from the blend solution by casting. The water uptake, dimensional and oxidative stability, proton conductivity were measured with respect to the addition content of PAN, the phase morphology of the resultant SPAES/PAN were also observed by SEM. The results explained that the corporation of PAN into SPAES could reduce the water uptake and improve the oxidative stability of the obtained membranes compared with the pristine SPAES membrane. That the PAN phase distributed as separated domains in SPAES matrix was found, the interaction between SPAES and PAN may be present, which is responsible for the improvement of dimensional and oxidative stability. Although the proton conductivity of the blend membranes became reduced with increase of PAN content in the SPAES/PAN blend, the conductivity of 0.0265S/cm at 30°C could still be reached, satisfying the requirement for proton exchange membrane Fuel Cell

Study on Rheology of UHMWPAN /MMWPAN/DMSO Solution

Adding a mount of MMWPAN to UHMWPAN/DMSO dilute solution is a good way to increase the total PAN content (including MMWPAN and UHMWPAN) while the UHMWPAN content of the solution is hard to be increased. In this paper, the rheological properties of UHMWPAN/MMWPAN/DMSO solution and the role of UHMWPAN in this solution were studied. The complex viscosity (h*) and the steady shear viscosity (h) both increased as the UHMWPAN content rising.

폴리비닐알콜/폴리아크릴로니트릴 블렌드 필름의 제조 및 특성

A poly(vinyl alcohol)(PVA)/poly(acrylonitrile)(PAN) blend film was prepared and its properties were characterized to investigate the possibility of improving PVA as a reinforcing materials. From the wide-angle X-ray diffraction patterns of the blend films it can be seen that the diffraction peaks from each polymer's crystal were not changed by blending, this implies there is no mutual influence in crystallization. The water contact angle of the blend film increased with increasing PAN content. The decrease rate of the water contact angle of the blend film with time was smaller than the rate for pure PVA film. The melting temperatures of the PVA/PAN blend film only at the ratios of 99/1 and 97/3 were higher than that of pure PVA film. The thermal decomposition temperature and residual weight of the blend films were increased with increasing PAN content, indicating improved thermal stability after blending with PAN. The tensile strength and Young's modulus of the film increased after blending and the PVA/PAN blend film containing 3wt% of PAN showed the best mechanical properties.

Synthesis and characterization of antibacterial semi-interpenetrating carboxymethyl chitosan/poly (acrylonitrile) hydrogels

Blend hydrogels composed of carboxymethyl chitosan (CMCh) and poly (acrylonitrile) (PAN) were synthesized via crosslinking method. Several analyses were made to investigate both physical and thermal properties of CMCh/PAN hydrogels like; FTIR, scanning electron microscope, XRD and thermogravimetric analysis (TGA). TGA results showed that CMCh/PAN hydrogels are thermally more stable than CMCh and their thermal stability increases as PAN content increases in the hydrogel. Moreover, the swelling behavior of CMCh/PAN hydrogels was studied in different buffer solutions. It was found that CMCh/PAN hydrogels swell much more than PAN especially at pH 9. The hydrogels sorption for different dyestuff and various metal ions like; Cu2+, Cd2+ and Co2+ were also studied. In this work, antibacterial characteristic of hydrogels was mainly investigated towards Escherichia coli (E. coli) as a serious disease-leading bacterium. All tested hydrogels have clearly presented good antibacterial activity as CMCh content increases in the hydrogels.

Conductive polyaniline/polyacrylonitrile composite fibers: Effect of synthesis parameters on polyaniline content and electrical surface resistivity

AbstractConductive polyaniline/polyacrylonitrile (PAn/PAN) composite fibers were prepared by keeping PAN fibers in various solutions containing aniline and then by polymerization of aniline sorbed by fibers with potassium dichromate as an oxidant. In examined polymerization media, aqueous HCl gave composite fibers with the highest PAn amount and these fibers also had the lowest electrical surface resistivity. It was found that, as PAn content of PAn/PAN composite fibers increased, its density also increased and mechanical properties such as tensile strength and breaking elongation decreased. From optical cross‐section images of composite fibers, it was observed that PAn coating was limited only with the PAN fiber surface. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Preparation and Characterization of PAN/SiO2 Hybrid Fibers

Two kinds of hybrid PAN/SiO2 sols were prepared via either sols blend or in-situ polymerization, respectively, and their spinnability was investigated. Hydrolysis time (t1) and spinnable time (t2) of both hybrid sols increased with PAN content. The hybrid fibers were characterized with FTIR, DSC, SEM and TG. As evidenced from the FT-IR spectra and DSC measurements, different chemical structures of hybrid fibers were different with CN groups hydrolyzed in the hybrid fibers via in-situ polymerization. SEM measurements showed the interior structures of the hybrid fibers via in-situ polymerization were more homogeneous. TG measurements suggest both of the hybrid fibers show better resistance to heat than pure PAN.

Conductive potassium feldspar/polyaniline composites prepared by in situ chemical polymerization

Conductive potassium feldspar/polyaniline (K-feldspar/PAn) composites were prepared by the chemical polymerization of aniline in the presence of K-feldspar particles using potassium dichromate in an acidic aqueous medium. The effects of K-feldspar particle size, aniline concentration and temperature upon the PAn amount in the composite and the electrical surface resistance of the composites were examined. Electrical conductivity was higher in the composites prepared by the smaller K-feldspar particles in which the PAn yield is low. The microhardness values of K-feldspar/PAn composites increased to a certain PAn content and then decreased. The microhardness of the composites containing PAn in the range of 1–6%, which were prepared by K-feldspar having particle size smaller than 0.125–0.250 nm, was higher that of pure K-feldspar and PAn (0.843 kPa). Scanning electron microscopy (SEM) showed that PAn covered the surface of K-feldspar particles with an unsmooth PAn layer. The characterization of composites was also made by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA).

Thermo‐mechanical Properties of PEO‐PU/PAN Semi‐Interpenetrating Polymer Networks and their LiClO4 Salt‐Complexes†

This paper is an investigation on the thermo‐mechanical properties of a new class of materials, which holds promise for its potential use as solid polymer electrolytes, i.e., SPE material. A series of poly(ethylene oxide)‐polyurethane/poly(acrylonitrile) (PEO‐PU/PAN) semi‐IPNs, along with their LiClO4 salt complexes, were characterized for their thermal, mechanical and dimensional stability using DSC, TG‐DTA, UTM and DMTA. The glass transition temperature (Tg) of both the undoped and doped semi‐IPNs, obtained by DSC, remained well below room temperature (∼−50°C to −35°C), satisfying one of the essential requirements to serve as a SPE host matrix. The crystallization process in the PEO segments of the PEO‐PU/PAN semi‐IPNs was prevented at higher salt concentrations, which is attributed to the Li+ ion mediated pseudo‐crosslinks. Good thermal stability of the semi‐IPNs was evident from the degradation onset temperature (T0∼240°C) with a three‐stage degradation process, which is independent of the PAN content as observed from differential thermogravimetric studies. The incorporation of PAN in the PEO‐PU networks results in improved mechanical properties, such as tensile strength and modulus while retaining the flexibility of the semi‐IPNs. The peak temperatures and storage modulus obtained from DMTA correlates well with the observations of DSC and tensile measurements. †IICT Communication No.: 0407019.

A convenient one‐step preparation of chitosan‐poly(sodium acrylate‐co‐acrylamide) hydrogel hybrids with super‐swelling properties

AbstractHydrogel hybrids were conveniently prepared from alkaline hydrolysis of chitosan–poly(acrylonitrile) mixture under highly practical conditions. The reaction of chitosan alkoxide anions with nitrile groups of poly(acrylonitrile) (PAN) forms crosslinking points and results in a three‐dimensional network with superswelling ability in aqueous media. The hydrogel hybrid was identified using FTIR spectroscopy. The PAN content of the hydrolyzing feed affects proportionally the swelling capacity of the hydrogel hybrid. The swelling properties (capacity and rate) of the ampholytic hydrogel were investigated preliminarily. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1615–1619, 2006