Modified Aramid Fiber Research Articles

Composites based on polymeric blends reinforced with TiO2 modified aramid fibers

AbstractThe paper presents a study on composites based on 50:50 (PP:LLPE‐g‐MA) reinforced with 0.5, 1, and 2 wt% aramid fibers unmodified/modified with TiO2, processed by melt compounding. Micronic aramid fibers were acetone washed to remove impurities and treated with Ti(IV)isopropoxide precursor via sol–gel method, adding microcellulose for TiO2 particle dimension control. Composites were hot‐pressed into 4 mm‐thick plates for sampling and 0.5 mm‐thick sheets for thermoforming. All composites were successfully thermoformed, fibers‐based samples showing improved thermoforming ability without wrinkling. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive X‐ray spectroscopy (EDS) analysis confirmed the formation of TiO2 particles on the fiber surface. Optical microscopy, SEM and FTIR analysis exhibit the fibers' strong embedment into the matrix due to physical interlocking, generating surface defect reduction. Water absorption decreased from 0.195% (control) to 0.075 and 0% for 1 TiO2 and 2 TiO2 samples, due to material compactization. Contact angles increased from 95.18° (Control) to 108° (1 TiO2) and 112.89° (2 TiO2). The highest flexural strength and modulus were exhibited by 1 TiO2 sample that increased by 44.88% and 47.6% compared to the control sample, due to higher intrinsic rigidity of fibers and TiO2 modifying surface rugosity and phase interaction. The impact strength of the control sample improved by 139% compared to PP due to brittleness reduction, 1 TiO2 by 209% compared to PP, 29% compared to the control sample. The results and excellent thermoformability recommend the materials for encapsulation of electronic/expensive parts in automotive or drone applications, offering viable, facile, rapid, and cost‐effective solutions to easily replace damaged parts.Highlights Aramid fibers were successfully modified using isopropoxide precursor; Strong embedment of fibers in the polymer diminishes crack propagation/damage; Improved impact and bending properties and water contact angle; The composites showed a high ability to thermoform into complex shapes; Potential to replace non‐reusable materials as encapsulation solutions.

Enhanced mechanical and electromagnetic interference shielding performance of carbon fiber/epoxy composite with intercalation of modified aramid fiber

Enhanced mechanical and electromagnetic interference shielding performance of carbon fiber/epoxy composite with intercalation of modified aramid fiber

Fabrication of silver ions aramid fibers and polyethylene composites with excellent antibacterial and mechanical properties

Abstract Nowadays, with the continuous understanding of the pathogenic mechanism of bacterium, the demand for antibacterial plastic products had significantly increased. Besides that, many counties issued mandatory standards for plastic products, which imposed strict requirements on ash content to prevent the addition of excessive inorganic matter to plastics in order to avoid weakening the properties of plastics and deteriorating the recyclable property. Based on this, the development of composites with organic fiber-loaded antibacterial agents is of practicable value and urgency. We used an open-ring addition reaction to modified aramid fiber (AF) by utilizing epoxypropyltrimethoxysilane to react with the reactive groups on the surface of AFs. Subsequently, the modified fibers were surface loaded with silver ionic glass beads. After that, a series of high-density polyethylene composites with excellent mechanical properties and antibacterial properties were prepared using melt mixing method. It was shown that the composite had a low ash value (1.88 wt%) even at a higher filling concentration (7 wt%) and the fibers could change the crystalline properties and morphology of the composite. Because of the fiber reinforcement and crystallization induction effects, the tensile strength and elasticity module of the composites could be improved by 141% and 136%, respectively. In addition, the composites had excellent long-lasting contact antibacterial effects against the inhibition of E. coli. The proposed organic fiber loading technique and antibacterial composites will provide a method for designing and preparing eco-friendly and high-performance plastic products.

Study on the Construction of Dopamine/Poly(ethyleneimine)/Aminoated Carbon Nanotube Multilayer Films on Aramid Fiber Surfaces to Improve the Mechanical Properties of Aramid Fibers/Epoxy Composites.

To improve the mechanical properties of aramid fiber (AF) reinforced epoxy resin (EP) composites without damaging the strength of the AF body, in this paper, poly(ethyleneimine) (PEI) and aminoated carbon nanotubes (NH2-CNTs) were successfully deposited on the AF surface layer by layer using poly(dopamine) (PDA) as the initial layer. The modified aramid fibers PDA-AF, PEI-PDA-AF, and NH2-CNTs-PEI-PDA-AF were prepared. The microstructure and chemical composition of the AF surface at different modification stages were systematically characterized. The interfacial properties, mechanical properties, and strengthening mechanism of AF surface-modified composites were studied. The results showed that with the successful deposition of PDA, PEI, and NH2-CNTs layer by layer, the interfacial properties and mechanical properties of the composites gradually improved. Among them, NH2-CNTs-PEI-PDA-AF showed the best strengthening effect. Compared with the unmodified aramid fiber (R-AF), the monofilament tensile strength of NH2-CNTs-PEI-PDA-AF increased by 8.1%, the contact angle with EP decreased by 21.9%, and the interface energy and adhesion energy increased by 115 and 21.4%, respectively. Compared with R-AF/EP, the interlaminar shear strength (ILSS), bending strength, and tensile strength of NH2-CNTs-PEI-PDA-AF/EP were increased by 75, 44.5, and 14.9%, respectively. The significant improvement of the interface properties and mechanical properties between NH2-CNTs-PEI-PDA-AF and EP can be attributed to the introduction of a large number of amino active groups in the NH2-CNTs-PEI-PDA coating layer on the AF surface, which strengthens the chemical-bond cooperation between the AF and EP matrix. At the same time, a large number of NH2-CNTs deposited on the surface effectively increased the surface roughness of AF, improved the mechanical meshing between the AF and EP matrix, and then improved the contact angle, surface energy, and interface bonding strength between the AF and EP matrix. Moreover, a large number of NH2-CNTs on the surface of AF also modified and enhanced the EP in the interface region, which could make the load more effectively transfer from the resin to the fiber, so that AF could carry the load more uniformly, significantly improving the mechanical properties of NH2-CNTs-PEI-PDA-AF/EP.

Modification of Heterocyclic Para-Aramid Fibers with Chlorine Groups and the Interfacial Properties of the Fiber/Epoxy Composites

A modified para-aramid fiber with chlorine groups based on heterocyclic aramid fibers was prepared by copolycondensation, wet-spinning and high temperature thermal treatment. The prepared fiber (named F358Cl) and other aramid fibers, including two commercial aramid fibers (K49 and F358) and one surface modified aramid fiber (F358F) by direct fluorination of F358, were characterized and analyzed in detail by infrared (IR) spectroscopy, scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), atomic force microscopy coupled with infrared spectroscopy (AFM-IR) and mechanical analysis. The experimental results indicated that the modified aramid fiber with chlorine groups showed excellent mechanical, thermal and composite properties. The interlaminar shear strength of the F358Cl/epoxy composite reached as high as 59 MPa, which was 23% higher than that of F358 (48 MPa) and 9% higher than that of F358F (54 MPa).

Comparative tribological performance and erosion resistance of epoxy resin composite coatings reinforced with aramid fiber and carbon fiber

In this work, chitosan modified aramid fiber (MAF) and carbon fiber (MCF) were prepared by simple self-assembly of chitosan on the fibers. The interface adhesion strength between fiber and epoxy resin was greatly improved, due to the active groups on the surface of chitosan. Compared with pristine composites, MAF/EP and MCF/EP showed impressive improvements of 15.61% and 18.06% in interfacial stress strength (IFSS), respectively. The effects of MAF and MCF on the tribological performance and erosion resistance of composite coatings were comprehensively studied. Compared with MAF/EP, the tensile strength of MCF/EP composite coating increased 11.09%. The test results showed that the MCF reinforced epoxy composite coating performed better anti-wear ability than that of MAF, which was due to the load-capacity and strength of MCF/EP was higher. Compared with MAF/EP, the wear rate of MCF/EP composite coating was reduced by 66.35%. Furthermore, the load-capacity and interface stress strength of MCF was higher than that of MAF, lead the erosion properties of MCF/EP was much better than MAF/EP. Compared with MAF/EP resin, the erosion volume of MCF/EP composite coating was reduced by 50.38%, showing outstanding erosion resistance, which was attributed to the resistance of high-strength carbon fiber to SiC particles.

Surface construction of ANF/CNT onto aramid fibers to enhance interfacial adhesion and provide real-time monitoring of deformation

To solve the poor interface between aramid fiber and rubber, this paper studies a method of constructing nanostructures on the fiber surface. First, functional groups such as hydroxyl and amino groups were introduced onto aramid fiber through the Michael addition of tannic acid and polyethyleneimine. Then, the modified aramid fiber was impregnated in the aramid nanofiber/carbon nanotube aqueous dispersion to prepare a surface-coated fiber. The fibers and surface nanostructures were characterized by scanning electron microscopy, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, thermalgravimetric analysis, and H pull-out tests in detail. The results show that the H pull-out force of the coated fiber is increased by 126.4% compared with the original aramid fiber, which is due to the good mechanical interlocking at the interface of the composites. In addition, carbon nanotubes could form a conductive path through mutual entanglement and overlap on the surface of aramid fiber, which also gives the function of real-time monitoring of deformation of the composites.

Decorating aramid fibers with chemically-bonded amorphous TiO2 for improving UV resistance in the simulated extreme environment

Aramid fiber holds a great potential application in harsh environments like defense and aerospace due to outstanding integrated properties, but it still falls short in poor UV resistance and surface inertness. It is an intriguing but challenging task to obtain high anti-UV efficiency for aramid fiber without compromising the mechanical characteristics. Herein, a uniform and thickness-controlled amorphous TiO2 coating is chemically-bonded onto aramid fiber surfaces via a modified atomic layer deposition (mALD) strategy. Although mALD TiO2 has an amorphous structure, its special chemical bonding state similar to LBL enables it to absorb UV light to a certain extent, but at the same time endows it with low photocatalytic activity. In contrast to bare aramid fiber with poor UV resistance and greatly suppressed mechanical performance, the modified aramid fibers with 1000 ALD cycles possesses well-preserved mechanical strength and flexibility. Moreover, they exhibit 54.08% retention of initial tenacity even exposure to UV irradiation with intensity of 4260 W/m2 at high temperature (>200 °C) for 360 min (equals to continuous exposure to strong sunlight irradiation for about 7.5 years), simultaneously retain the excellent laundering durability and lustrousness, demonstrating a significant enhancement in anti-UV efficiency. Such highly anti-UV fibers fabricated by a facile mALD strategy provide a new perspective on designing multifunctional fibers and devices for future innovative applications.

Mussel-inspired environmentally friendly dipping system for aramid fiber and its interfacial adhesive mechanism with rubber

To strengthen the interfacial adhesion between aramid fiber and rubber, inspired by mussel adhesion protein and mimicking adhesive molecule, a new environmentally friendly dipping system was developed. Specifically, water-soluble pyrogallic acid and polyethyleneimine are reacted to form a network structure, which is then mixed with rubber latex to prepare the dipping solution. We use blocked isocyanate and epoxy aqueous solution to activate the fiber, and then conduct the dipping treatment. The H pull-out force between modified aramid fiber and rubber reached 147 N, achieving the level of traditional resorcinol-formaldehyde-latex dipping system (154 N), while avoiding the utilization of harmful resorcinol and formaldehyde. In addition, we employed atomic force microscope for the first time to quantitatively characterize the modulus of the transition layer between the fiber and rubber. Results from this research provide new insights into the interfacial design of aramid fiber/rubber composites and will facilitate the development of aramid fiber/rubber composites.

Graphene Oxide-Modified Aramid Fibers for Reinforcing Epoxy Resin Matrixes

Carboxylated and aminated graphene oxide (CGO and AGO) were first prepared by using carboxyl-terminated aromatic hyperbranched polyester (HBPC) and amino-terminated aromatic hyperbranched polyester (HBPA) noncovalent functionalized GO, respectively. Subsequently, multiscale reinforcing fibers (CGO-PDA-AF and AGO-PDA-AF) were prepared by exploiting the super adhesion of the polydopamine layer (PDA) and its physical adsorption and chemical grafting with the CGO and the AGO. This study examined the tensile strength of the modified aramid fiber (AF) monofilament and the interfacial shear strength (IFSS) between the modified AF monofilament and the EP matrix, and an investigation was conducted on the interfacial enhancement mechanism. As indicated from the results, the AGO exerted a more effective modifying effect than the CGO. The single filament tensile strength and IFSS of the AGO-PDA-AF were the maximum (4.66 GPa and 96.2 MPa), nearly 8.6 and 7.9% higher than those of the CGO-PDA-AF, respectively. The enhancement of the interface performance between the AGO-PDA-AF and the EP was attributed to the introduction of considerable amino active groups in the AGO, thereby forming a stable covalent bond with the epoxy matrix, which significantly improved the interface bonding strength. Moreover, the flexible coating layer formed by the AGO could reduce the stress concentration of the interface through deformation, so the AF could be carried more uniformly. Furthermore, the AGO increased the surface affinities of the AF and improved the mechanical interlocking with the EP matrix.

Surface modification of aramid fiber by crystalline polyarylene ether nitrile sizing for improving interfacial adhesion with polyarylene ether nitrile

The interfacial compatibility plays an important role in the performance of fiber-reinforced composite laminates. Aramid fiber is an important class of high performances fibers. However, the inertia of fiber surface is not conducive to the improvement of composite properties. In this work, polyarylene ether nitrile terminated with phthalonitrile (PEN-t-Ph) was supplied to modify the aramid fiber (m-AF). By heat treatment and riveting PEN-t-Ph to the fiber surface, a rough fiber surface can be obtained, and then the composite material with improved performance can be obtained through the entangling compatibility. Through SEM images, it could be seen that the fiber surface had the best rivet surface morphology when the fiber surface coated with 5 wt% PEN-t-Ph (m(5 wt%)-AF). At the same time, the interfacial adhesion between m(5 wt%)-AF and the resin matrix showed the best peel strength of 1.594 kN/m. Based on these results, modified fiber resin composite laminates (m(5 wt%)-AF/PEN-t-Ph) were fabricated. The results indicated that the laminates had good interfacial compatibility and the interlaminar shear strength (ILSS) of modified aramid fiber laminates was 112.58 MPa, which is increased by 21.4% than that of original fiber composite laminates. In addition, the flexural strength of m-AF/PEN-t-Ph laminates was 324 MPa, increased by 10% compared to AF/PEN-t-Ph. The results of DMA showed that the energy storage modulus of the m-AF/PEN-t-Ph laminate was greatly improved compared with that of AF/PEN-t-Ph laminate, which was increased by 60% under the initial condition of 100 °C. To sum up, through surface treatment, the mechanical properties of fiber-reinforced composite laminates had been greatly improved, making them have great application prospects in bulletproof and other fields.

Synergistic modification by mercapto hyperbranched polysiloxane and functionalized graphene oxide on the surface of aramid fiber

With the purpose of improving the interfacial properties of aramid fibers reinforced rubber composites and enhancing the tensile strength of aramid fibers simultaneously, mercapto hyperbranched polysiloxane (HPSi) and functionalized graphene oxide (GO) were used to modify the surface of aramid fibers. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and other characterization methods were performed to confirm the process of synergistic modification. Judging from the results of mechanical property tests, it could be acquired that the tensile strength of modified aramid fiber was increased by 16.8%, which could be ascribed to the wrapping effect of GO sheets. The interfacial properties were assessed by the pull-out tests of composites, and the results showed that the maximum pull-out force after synergistic surface modification was increased by 99.3%, which could be mainly related to additive reaction between double bonds and mercapto groups and the promotion of surface energy. More critically, during pull-out test, aramid fiber bundles might bring a part of shear stress into the grafted GO sheets, namely, GO sheets could convert fracture energy into interfacial energy, which would improve interfacial properties dramatically.

Combined treatments of fiber surface etching/silane-coupling for enhanced mechanical strength of aramid fiber-reinforced rubber blends

This study sought to improve the interfacial bonding force between aramid fiber (AF) and a rubber matrix. We pretreated the aramid fiber with anhydrous calcium chloride (CaCl2) and sodium hydroxide (NaOH) solutions. We then performed a separate modification using two different methods, first, grafting the aramid fiber with silane coupling agent γ-Methacryloxypropyl trimethoxy silane (KH570) and secondly in situ formation of silica on the surface of aramid fiber. In addition, mechanical blending was adopted to prepare natural rubber/cis-1,4-polybutadiene rubber/aramid fiber (NR/BR/AF) composites. Finally, aramid fibers were characterized via Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM), then the mechanical properties of the corresponding composites analyzed. Results revealed that the synergistic action of anhydrous CaCl2 and NaOH solutions caused an increase in surface roughness and the contact area of the aramid fiber. The Sol-gel method allowed successful coating of the secondary modified aramid fiber surface with a layer of in situ-generated silica. Consequently, this improved surface reactivity of the fiber and the rubber matrix, thus promoting their combination. Moreover, we successfully grafted KH570 onto the surface of the aramid fiber through an oxygen-containing group on the surface of the pretreated aramid fiber. Tensile properties of AF composites exhibited a 31.9% increase after secondary modification with KH570 whereas their DIN abrasion performance increased by 16.2%. Notably, a significant improvement in interfacial adhesion was recorded in modified AF prepared NR/BR composites, which further improved the mechanical properties of NR/BR composites.

Surface Functionalization of Silver-Coated Aramid Fiber

Silver nanoparticles are deposited on aramid fiber surfaces by a three-step process. Calcium chloride/ethanol coarsening of the aramid fiber is followed by surface functionalization with poly(dopamine) and electroless silver plating. The chemical structure and elemental composition of the aramid fibers are determined by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy, respectively. The surface morphology of the modified aramid fibers is investigated by scanning electron microscopy and atomic force microscopy. The crystalline structure and thermal stability of the modified aramid fibers before and after silver plating are analyzed by X-ray diffraction and thermogravimetric analyses. A four-point probe is used to determine the electrical resistivity of the silver-plated aramid fibers. The results show that after the silver plating of the aramid fiber surface, its electrical resistance was reduced. At 20 g/L AgNO3, the silver layer on the aramid fiber surface is stable and durable with a high electrical resistivity.

Improving the Mechanical and Surface Properties of Aramid Fiber by Grafting with 1,4-Dichlorobutane under Supercritical Carbon Dioxide.

The mechanical and surface properties of aramid fiber were simultaneously improved by grafting with 1,4-dichlorobutane in supercritical carbon dioxide (scCO2). 1,4-dichlorobutane was penetrated and reacted with heterocyclic an aromatic polyamide backbone along with supercritical CO2 fluids. The surface roughness and surface energy of the modified aramid fiber—which were measured by scanning electron microscopy (SEM) and the dynamic contact angle (DCA) test, respectively—significantly increased. X-ray diffractometer (XRD) measurements indicated that the crystallinity of the aramid fiber obviously increased after treatment in scCO2 under stretching. A single fiber tensile test showed that the tensile strength of the aramid fiber greatly enhanced after the modification due to its improved crystallinity characteristics. Moreover, the monofilament pull-out tests indicated that the interfacial shear strength (IFSS) test of the aramid fiber/epoxy composite increased by 24.3% from 51.30 to 63.91 MPa after the modification. This research provides a novel method for the simultaneous surface modification and mechanical improvement of aramid fiber properties.

Amino graphene oxide/dopamine modified aramid fibers: Preparation, epoxy nanocomposites and property analysis

Dopamine modified aramid fiber (AF) surface was grafted with amino functionalized graphene oxide to improve the interfacial adhesive performance. The self-polymerized polydopamine (PDA) coating and subsequent amino GO grafting on the AF surface attributed to the increase in its surface roughness and surface-active groups. The functional groups, chemical composition and surface topography of unmodified and modified AF was investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM). The interfacial properties were analyzed by measuring interfacial shear strength (IFSS) of unmodified and modified AF embedded epoxy matrix. Further, the properties were tuned by optimizing the reaction temperature and concentration of ethylenediamine. The IFSS of AF/epoxy composites was increased by 34% after grafting amino graphene oxide.

Thermal degradation study of rigid polyurethane foams containing tris(1-chloro-2-propyl)phosphate and modified aramid fiber

The rigid polyurethane foams (RPUF) were prepared using tris(1-chloro-2-propyl)phosphate(TCPP) and modified aramid fiber(MAF) as flame retardants. The thermal degradation behaviors of RPUF and flame retardant RPUF were investigated by thermogravimetric analysis/infrared spectrometry (TG–IR), gas chromatography-mass spectrometry (GC–MS). Char residue for PU composites at different temperatures was analyzed by fourier transform infrared spectra (FTIR). The TGA curves suggested that aramid fiber(AF) has good ability of char formation. In TG–IR measurement, simultaneously use of TCPP and MAF in the RPUF exhibited lower smoke and toxicant production and increased char residue compared to RPUF containing TCPP. Production of toxic gases such as hydrogen cyanide (HCN) was significantly decreased, nonflammable gases carbon dioxide (CO2) and water were increased. GC–MS illustrated that TCPP and MAF exerted barrier effect in the condensed phase and the quench effect in the gaseous phase. Based on these facts, a potential thermal degradation mechanism was primarily proposed.

Effect of tris(1-chloro-2-propyl)phosphate and modified aramid fiber on cellular structure, thermal stability and flammability of rigid polyurethane foams

Effect of tris(1-chloro-2-propyl)phosphate (TCPP) and modified aramid fiber (MAF) on cellular structure, thermal stability and flammability of rigid polyurethane foams (RPUF) has been investigated. RPUF with liquid TCPP and MAF alone, as well as the mix of TCPP and MAF, were prepared via a one-step process in this work. Phosphoric acid was used to modify AF, the P-OH in the MAF and the improvement of interfacial strength between MAF and PU was characterized using infrared spectrum analysis and scanning electron microscopy (SEM). Limited oxygen index (LOI) results indicated that TCPP exhibited more pronounced flame retardant efficiency than MAF for the RPUF. Gas chromatography/mass spectroscopy (GC/MS) illustrated that its flame retardancy took place in both condensed and gaseous phases. Meanwhile, the use of TCPP decreased the thermal stability of RPUF unlike MAF. The decrease by 9.4, 35.7% in the max smoke density (MSD) and peak smoke product rate (PSPR) respectively compared with RPUF showed that MAF was an environmentally friendly flame retardant. However, when TCPP and MAF were used in combination, they effectively enhanced the fire resistance and ensure macro- and micro-cellular structure of RPUF, unlike standalone use of TCPP and MAF. When 20%TCPP was simultaneously used with 5%MAF, the macro- and micro-cellular structures of the residue after cone calorimeter test (CCT) were clearly improved compared with foams prepared using MAF only. Their main advantage is related to the enhancement of compactness of the char layer and higher density. Compared with foams without flame retardants, the fire resistance of RPUF prepared with 20% RPUF and 5%MAF was enhanced; specially, the LOI was enhanced by 39.2%, MSD and peak heat release rate (PHRR) decreased by 25%, 59.6% respectively. Thus, the use of liquid and solid flame retardants in combination may effectively manufacture RPUF with high quality cellular structures and excellent fire resistance.

Enhanced Interfacial Strength and UV Shielding of Aramid Fiber Composites through ZnO Nanoparticle Sizing.

Here, a simple zinc oxide (ZnO) nanoparticle sizing is reported for aramid fibers that simultaneously provides interfacial reinforcement and UV absorption to develop improved fiber-reinforced composites. Through a one-step nanoparticle deposition, the modified aramid fiber showed an increase in interfacial shear strength of 18.9% with the addition of ZnO nanoparticles when tested by single-fiber pullout. The aramid fibers were then treated with a hydrolysis process common to aramid fibers to oxidize the surface and elucidate the importance of oxygen functional groups at the interface. These oxidized fibers proved to further enhance the interface between the fiber surface and nanoparticle, leading to a 33.3% increase relative to the bare fiber. Additionally, due to the absorption properties of ZnO, the retainment of mechanical properties of coated fibers was determined after exposure to an artificial UV light source. After 24 h of exposure, fibers coated with ZnO nanoparticles retained 25% more tensile strength and 21% more modulus than uncoated bare fibers. This work shows that ZnO nanoparticles may serve as a novel, yet simple, multifunctional fiber sizing with which to increase the interfacial strength of aramid fiber composites and improve the resistance to UV irradiation, enabling stronger and more-durable structural fiber composites.

A facile method to enhance UV stability of PBIA fibers with intense fluorescence emission by forming complex with hydrogen chloride on the fibers surface

To date, the main method in improving UV stability of aramid fibers is to coat ultraviolet screening agent on the surface of fibers. However, this method has a disadvantage that the coating tends to fall off when the fibers are exposed to an external force. In the present research, A diamine monomer 2-(4-aminophenyl)-5-aminobenzimidazole (PABZ) was introduced to modify poly (p-phenylene terephthalamide) by copolymerization, and corresponding modified aramid fibers (PBIA fibers) were prepared. we found that PBIA fibers can form complex with hydrogen chloride (HCl) which would not lead to the obvious decrease in mechanical properties, and the decomplexation of HCl can only be achieved at high temperature (higher than 280 °C). At the same time, PBIA/HCl complex molecule showed intense fluorescence emission, and which can provide an effective way to dissipate the harmful UV energy, thus, the UV resistance of PBIA fibers can be improved. In addition, the HCl have the ability to quench the photoactive triplet state of PBIA fibers, which can also contribute to improve the UV resistance of PBIA fibers. After 48 h UV irradiation, the PBIA/HCl complex fibers almost remained their tensile performances (only about 3% loss in tensile strength), and UV irradiation did not bring the obvious deterioration in structure and performance of the complex fibers. On the contrary, for PBIA fibers, its chemical structure and physical properties all suffered to obvious damages (about 15% loss in tensile strength). The UV resistance of PBIA/HCl complex fibers is approximately 5 times higher than that of PBIA fibers.