PBO Fiber Research Articles

An Important Factor Affecting the UV Aging Resistance of PBO Fiber Foped with Nano-TiO2: The Number of Amorphous Regions.

Modified nano-TiO2 was prepared by using triethanolamine and tetraisopropyl di (dioctylphosphate) titanate, respectively. Then the poly(p-phenylene benzobisoxazole) (PBO) fibers doped with different additions of modified nano-TiO2 particles were prepared by preparing PBO polymer solution and dry-jet wet spinning technique. Thermogravimetric and derivative thermogravimetry results showed that the addition of nano-TiO2 could improve the crystallinity and maximum thermal decomposition rate temperature of PBO fibers. Tensile strength results showed that nano-TiO2 addition did not affect the tensile properties of PBO fibers before ultraviolet (UV) aging began, and nano-TiO2 with addition values lower than 3% could improve the UV aging resistance performance of PBO fibers, while the aging resistance would be seriously reduced if values were over 5%. The size and quantity of the amorphous regions have a more important influence on the aging resistance of PBO fibers.

Synthesis of A Novel Cross‐linker with High Reactivity for Enhancing Compressive Strength of High‐performance Organic Fibers

AbstractLow axial compressive strength of high‐performance organic fibers is one of the most prominent problems for their application in advanced technologies. In this paper, N, N’‐diphenyl‐1,4‐phenylacetyleneamide (DPAA) as a novel external cross‐linker was synthesized. It was confirmed that DPAA could react itself and quickly form cross‐linking network above 210 °C with pore width of 1–30 nm. Then DPAA was introduced into some typical high‐performance organic fibers through post‐swelling process, followed by annealing at 250 °C. It was found that DPAA would in‐situ form cross‐linking network inside the fiber, which was regarded as semi‐interpenetration structure. Compressive strength of Kevlar‐49 fiber modified through this method increased by nearly 70% and corresponding tensile strength didn't deteriorate. When PBO, heterocyclic aramid and polyimide fibers were modified by the same procedure, their compressive strength showed 25, 36 and 72% enhancement respectively. Therefore, DPAA is an effective modifier to enhance compressive strength of high‐performance organic fibers and shows great universality.

Flexible conductive copper/reduced graphene oxide coated PBO fibers modified with poly(dopamine)

Nowadays, flexible fiber heater has attracted great interests. Here, we fabricated a copper/reduced graphene oxide (Cu/RGO) hybrids coating on the surface of poly(p-phenylene benzobisoxazole) (PBO) fiber with excellent tensile strength, high thermal stability and high flame retardancy for electrothermal heater. Copper was plated on the surface of PBO fibers by the modification of the PBO fibers with poly(dopamine) followed by RGO activation and electroless copper plating and copper coated PBO fibers (Cu/RGO-PBO) is obtained. Poly(dopamine) and RGO acted as synergistic activating agents for electroless copper plating. Cu/RGO-PBO fibers exhibit low electrical resistance of 0.16 Ω cm−1 and possess excellent electrical conductivity even after 20 cycles of washing. The heating temperature of Cu/RGO-PBO fibers is steady at around 44 °C which is suitable for keeping body warm. Additionally, Cu/RGO-PBO fibers reveal a low corrosion current density of 2.46 μA cm−2. The result indicates flexible Cu/RGO-PBO fibers with excellent electrical conductivity, heating performance and corrosion resistance, which could be used as flexible electrically conductive fiber and wearable heater with corrosion resistance.

Thermal, Mechanical, and Microstructural Study of PBO Fiber during Carbonization.

Poly(p-phenylene benzobisoxazole) (PBO) fiber shows fascinating properties including excellent mechanical performance, high crystallinity, and fairly good heat resistance as a kind of polymer fiber. Its properties make it a possible candidate as a precursor of carbon fiber. This paper mainly investigates the possibility of yielding carbon fiber from PBO by direct carbonization using a continuous process and multiple properties of yielded fiber treated under different heat treatment temperature (HTT). The results show that PBO fiber was able to sustain an HTT as high as 1400 °C under the inert atmosphere and that the shape of fiber was still preserved without failure. Using thermal gravimetric analysis (TGA) and TGA coupled with mass spectroscopy (TGA-MS), it was found that a significant mass loss procedure happened around 723.3 °C, along with the emission of various small molecules. The mechanical performance first suffered a decrease due to the rupture of the PBO structure and then slightly increased because of the generating of graphite crystallite based on the broken structure of PBO. It was observed that PBO’s microstructure transformed gradually to that of carbonaceous material, which could be the reason why the change of mechanical performance happened.

Estimation of the Modulus Fir Wood Reinforced With PBO Fiber Mesh

AbstractThis paper presents the results of preliminary tests for estimating the modulus of elasticity of wooden beams from firs reinforced with PBO fiber mesh. The tests were carried out in the Materials Strength Laboratory at the Kielce University of Technology in Kielce, Poland with PN-EN 408: 2004. The wooden elements were subjected to a four-point bending test with the aim of estimating the elastic modulus when bending, assuming the loading velocities of the loading forces of 5 mm / min. The obtained results show a significant increase in the load-bearing capacity of beams reinforced with PBO mesh.

Flexible reduced graphene oxide/electroless copper plated poly(benzo)-benzimidazole fibers with electrical conductivity and corrosion resistance

In order to produce conductive poly(benzo)-benzimidazole (PBO) fibers with corrosive resistance, copper plating on the surface of PBO fibers was carried out via palladium-free activation by electroless plating, followed by partial reduced graphene oxide (rGO) coating via electrophoretic deposition (EPD). The morphology, element composition and crystal structure of copper plated PBO (Cu/PBO) fibers were studied by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction, respectively. Effect of deposition time on the deposition rate of copper, deposit weight and electrical resistance of Cu/PBO fibers was investigated. In addition, electrical conductivity and heat generation of Cu/PBO fibers were evaluated. The surface of PBO fibers is uniformly and densely covered with spherical copper particles and Cu/PBO fibers possess excellent conductivity with the electrical resistance of 2.98 × 10−3 Ω m for deposition time of 70 min. The corrosion resistance of reduced graphene oxide coated copper plated PBO (rGO/Cu/PBO) fibers was studied by Tafel analysis. The corrosion potential has a negative shift of 31 mV (from − 240.2 to − 209.2 mV) and Icorr reduces from 4.34 µA/cm2 for Cu/PBO fibers to 1.24 µA/cm2 for the rGO/Cu/PBO fibers. The results indicate that the rGO coatings on Cu/PBO fibers can protect copper coating against corrosion. The results indicate that rGO/Cu/PBO fibers possess excellent electrical conductivity and corrosive-resistance, which could be used as conductive flexible materials with corrosive resistance.

Construction of Anti-Ultraviolet "Shielding Clothes" on Poly( p-phenylene benzobisoxazole) Fibers: Metal Organic Framework-Mediated Absorption Strategy.

A metal-organic framework (MOF)-mediated adsorption strategy is first developed for improving the anti-ultraviolet (UV) properties of poly( p-phenylene benzobisoxazole) (PBO) fibers. In this work, UIO-66 was successfully anchored onto the surface of PBO fibers by one-step microwave-assisted heating method. The experimental results showed an obviously enhanced surface energy (91.1%), roughness (268.4%), interfacial shear strength (49.0%), and anti-UV properties (66.7%) compared to pristine PBO fibers. The anti-UV dye (tartrazine) was further immobilized onto the surface of PBO fibers via an adsorption strategy mediated by UIO-66. Interestingly, the PBO@tartrazine fibers demonstrated superior anti-UV performance (further up to 81.5%) compared to PBO@UIO-66 fibers. The extraordinary anti-UV properties of PBO@tartrazine fibers could be rationally ascribed to the synergistic effects of UIO-66 and tartrazine molecules. Considering the diversities and functionalities of MOFs and targeted materials, our work indicates that the MOF-mediated adsorption strategy would promisingly endow PBO fibers with other desired performance and applications such as solar-thermal transition and self-healing abilities.

Effect of Surface Treatment on Flexural and Tribological Properties of Poly(p-phenylene Benzobisoxazole)/Polyimide Composites under Normal and Elevated Temperature.

(1) In order to improve the interface bonding state between poly(p-phenylene benzobisoxazole) (PBO) fibers and a polyimide (PI) polymer matrix, as well as its effectiveness under elevated temperature, rare earth solution (RES) and coupling agent were employed toward PBO fibers as surface modifiers in this article, respectively. (2) The surface characteristics of the PBO fibers before and after modifications were characterized and analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The effects of the surface treatment of the PBO fibers on the flexural properties and friction and wear behaviors of the polyimide polymer matrix composites reinforced by PBO fibers (PBO/PI) were studied under normal and elevated temperature, and the morphologies of the bending fracture and the worn surface were observed through scanning electronic microscopy (SEM). (3) The results revealed that the RES modification was superior to the coupling agent modification regarding increasing the surface activity of the PBO fibers. (4) The PBO/PI composite treated by RES had higher flexural properties and more excellent anti-friction and wear resistance than the pretreated and coupling agent-treated composites under both normal and elevated temperatures.

Preparation of a sub‐100 nm‐thick polyetherimide coating layer with nano‐TiO2particles on poly(p‐phenylene benzobisoxazole) fiber surface

ABSTRACTTo improve the UV resistance of poly(p‐phenylene benzobisoxazole) (PBO) fibers, a sub‐100 nm‐thick coating layer was prepared on PBO fibers by evaporating the suspension of polyetherimide (PEI)‐encapsulated nano‐titanium dioxide (TiO2) particles absorbed around the fiber surface. The effects of this evaporation‐induced surface modification on the structure and properties of PBO fibers were investigated. The content ratio of nano‐TiO2particles to PEI, the contents of nano‐TiO2particles and PEI, and the evaporation method greatly influenced the surface modification of the PBO fibers, as confirmed by scanning electron microscopy observation. TiO2, 3‐methacryloxypropyltrimethoxysilane, and PEI were confirmed to exist on the suitably treated PBO fiber surfaces by X‐ray photoelectron spectroscopy analysis. The PEI coating layer containing nano‐TiO2particles was clearly observed by transmission electron microscopy of a treated PBO fiber cross section. The nano‐TiO2particle content of the treated fibers was studied by thermogravimetric analysis. The UV resistance of the PBO fibers was improved after surface modification, which was confirmed by single‐fiber tensile strength test. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2018,135, 46852.

In situ synthesis of PBO‐α‐(amino phthalocyanine copper) composite fiber with excellent UV‐resistance and tensile strength

ABSTRACTThe anti‐ultraviolet (UV) aging of the poly(p‐phenylene benzobisoxazole) (PBO) is very important and has been paid much attention recently. In this study, copolymerization of PBO and α‐amino phthalocyanine copper (α‐TDMACuPc) was carried out by in situ polymerization and the fiber was obtained by dry‐jet wet spinning in the liquid crystal state. Inducing of α‐TDMACuPc into PBO macromolecules improve the molecular network and enhanced the tensile strength of PBO fiber. With the capability of absorbing UV light into the PBO molecular chain, PBO copolymer fibers showed excellent anti‐UV aging performance and changed with the block structure. It is found that the retention of tensile strength after 100 h of UV irradiation was improved from 66.44% of PBO to 88.80% of PBO‐2.0 wt % α‐TDMACuPc fiber. Meanwhile, the degree of UV etching of the fibers decreased with the addition of α‐TDMACuPc. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46870.

Surface modification of PBO fibers by direct fluorination and corresponding chemical reaction mechanism

Due to their excellent mechanical properties and heat resistance, Poly(p-phenylene benzobisoxazole) (PBO) fibers are applied as one of most potential reinforcement in resin matrix composite. However, the poor adhesion with resin limits their application in advanced composite materials. In this study, PBO fibers were first modified by direct fluorination to improve the interface adhesion between fibers and resin. X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to characterize the change of chemical structure and surface topography of fluorinated fibers. The results show that polar groups of C-F and -COOH are produced and surface roughness is enhanced, which increases the interface bonding strength of PBO fibers/epoxy by 48%. The fluorination reaction mechanism of PBO fibers is investigated on the basis of chemical structure change. It's suggested that oxazole ring reacts with fluorine gas preferentially over benzene ring, and addition reaction dominates when fluorine reacts with benzene ring.

Fabrication and investigations on the polydopamine/KH-560 functionalized PBO fibers/cyanate ester wave-transparent composites

Abstract Functionalized poly (p-phenylene-2, 6-benzobisoxazole) (f-PBO) fibers were firstly obtained by introducing polydopamine (PDA) and 3-GlycidoxypropyltriMethoxysilane (KH-560), then performed to fabricate the f-PBO fibers/fluoride-containing bisphenol A dicyanate ester (m-BADCy) wave-transparent laminated composites. PDA was coated on the surface of PBO fibers and KH-560 was also grafted onto the PBO fibers. And the single fiber pull-out strength of the f-PBO fibers/m-BADCy micro-composites was increased from 3.2 MPa (PBO fibers/BADCy) to 4.0 MPa. Interlaminar shear strength (ILSS) and flexural strength of the f-PBO fibers/m-BADCy composites was also enhanced to 49.5 MPa and 652.2 MPa, increased by 39.8% and 12.1%, compared with that of PBO fibers/BADCy composites (ILSS of 35.4 MPa and flexural strength of 582.0 MPa), respectively. The corresponding e and tanδ was decreased to 2.86 and 5.7 × 10-3, declined by 6.5% and 23.0%, compared with that of PBO fibers/BADCy composites (e of 3.06 and tanδ of 7.4 × 10-3), respectively.

Novel synthesis of high‐molecular‐weight prepolymer of poly(p‐phenylene benzoxazole) in ionic liquids

Using ionic liquids (ILs) as the reaction solvent for the synthesis of prepolymer polyamide of poly(p‐phenylene benzoxazole) (PBO) was investigated. The optimum condition of prepolymer preparation was determined in ILs. A series of 1,3‐dialkylimidazolium ILs were used to be the reaction media of the polycondensation. The relationship between the molecular weight of prepolymer and the structure of ILs was analysed by changing the structure of the cation and species of anion of ILs. In order to prove the feasibility of the transformation, the prepolymer was used to prepare PBO in polyphosphoric acid media, and the conversion process was analyzed. The spinnability of the PBO solution was explored by the preparation of PBO fibers. The basic mechanical properties of PBO single fiber were tested. In a word, using 1,3‐dialkylimidazolium ILs as the reaction solvents was feasible for the synthesis of high‐molecular‐weight PBO prepolymer, which could be a promising PBO preparation method.

Light triggered interfacial damage self-healing of poly(p-phenylene benzobisoxazole) fiber composites

The interfacial microcracks in the resin matrix composites are difficult to be detected and repaired. However, the self-healing concept provides opportunities to fabricate composites with unusual properties. In the present study, photothermal conversion Ag–Cu2S nanoparticles were immobilized onto poly(p-phenylene benzobisoxazole) (PBO) fibers via a polydopamine chemistry. Benefitting from the photothermal effects of Ag–Cu2S, the obtained PBO fibers (Ag–Cu2S–PBO) efficiently converted the light energy into heat under Xenon lamp irradiation. Then, single PBO fiber composites were prepared using thermoplastic polyurethane as the matrix. It was found that the interfacial damage caused by single fiber pull-out was simply self-healed by Xe light irradiation. This wonderful interfacial damage self-healing property was mainly attributed to the in situ heating generation via photothermal effects of Ag–Cu2S in the composite interface. This paper reports a novel strategy to construct advanced composites with light-triggered self-healing properties, which will provide inspiration for preparing high performance composite materials.

Mussel-inspired immobilization of BN nanosheets onto poly(p-phenylene benzobisoxazole) fibers: Multifunctional interface for photothermal self-healing

The composites with interfacial self-healing ability are smart and promising materials in the future. Although some approaches have been used to heal the micro-cracks in composite materials, it is still a great challenge to develop a versatile strategy to fabricate multifunctional interface for self-healing. Here, boron nitride nanosheets (BN) are immobilized onto PBO fibers by facile polydopamine (PDA) chemistry. Benefiting from the photothermal effect of BN-PDA, the obtained surface layer displays interfacial self-healing properties under Xenon light irradiation.

Evaporation-induced surface coating of poly( p -phenylene benzobisoxazole) fibers with polyetherimide encapsulated nano-TiO 2

Abstract Poly( p -phenylene benzobisoxazole) (PBO) fibers were modified using the evaporation-induced surface coating method. Through this new method, nano-TiO 2 particles encapsulated with polyetherimide (PEI) chains were firmly adsorbed on the fiber surface. The coating thickness was calculated through the observation of the fiber cross-section by transmission electron microscope. The surface morphologies of the fibers were examined using scanning electron microscopy and field-emission scanning electron microscopy, the surface chemical composition was analyzed with energy dispersive X-ray spectroscopy. The surface roughness was analyzed with atomic force microscopy, and thermogravimetry and single fiber tensile strength were also measured. The results indicate that besides some nanospheres resulted from the initial agglomeration of PEI-encapsulated nano-TiO 2 , a uniform coating layer with thickness of 84 nm was formed by absorption of polyetherimide (PEI)-encapsulated nano-TiO 2 . This coating method changed the surface morphology of the PBO fibers, enhanced the surface roughness, and increased the poor UV resistance of untreated PBO fibers.

Concrete columns confined with different composite materials

In the last decades, the need for upgrading, strengthening and retrofitting of existing concrete structures is rapidly growing. Composite materials showed to be an optimal solution to face this problem, combining high efficacy with low invasiveness. The use of Fiber Reinforced Polymers (FRP) to wrap concrete columns has been widely investigated and became a very successful method to improve their structural performances. However, it has been recognized that FRPs, due to the presence of an organic resin, have a few drawbacks, such as poor mechanical behavior at high temperatures, lack of vapor permeability and impossibility to be installed on wet surfaces. This experimental work aims to propose a comparison between three different innovative methods as possible strengthening solutions for existing concrete columns. The structural behavior of 20 reduced scale concrete columns, realized by using a low performance concrete, in order to reproduce the poor mechanical properties of existing structures, was investigated. Two unreinforced column were tested in compression as reference. Six of them where reinforced by applying an external layer of FRP, with different types of fabric reinforcement (made of carbon or PBO fibers). Six columns were reinforced by using the same fabrics coupled with an inorganic matrix (FRCM) instead of epoxy. Six other columns were reinforced by using a layer of High Performance Fiber Reinforced Concrete (HPFRC) of 3 cm thick. Experimental results have been analyzed and performance of the three reinforcement systems have been compared.

Synchronously improved dielectric and mechanical properties of wave-transparent laminated composites combined with outstanding thermal stability by incorporating iysozyme/POSS functionalized PBO fibers

Synchronously improved dielectric and mechanical properties of wave-transparent laminated composites combined with outstanding thermal stability by incorporating lysozyme/POSS functionalized PBO fibers.

Preparation of PBO/ZnO fibers by hydrothermal synthesis method and its properties

In this article, zinc oxide (ZnO) nanoparticles were synthesized and deposited on the surface of PBO fibers through hydrothermal synthesis method. The structures and properties of PBO/ZnO fibers and PBO fibers were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), x-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Thermogravimetric analysis (TG), and tensile testing. The results revealed that the PBO/ZnO fibers have good mechanical properties and high thermal stability. Moreover, the fibers exhibited excellent UV-blocking properties by putting them under UV irradiation of 313 nm. Specifically, ZnO coated fibers will lose only 18.93% of tensile strength after 50 h irradiation, and then will keep over 65% of tensile strength after 100 h UV irradiation. Additionally the interface shear strength is increased significantly, and the results also showed modified PBO fibers exhibited excellent hydrophobic quality. So the functional materials have great potentials in future engineering applications.

Bond Behavior of FRCM Carbon Yarns Embedded in a Cementitious Matrix: Experimental and Numerical Results

The use of inorganic cement based composite systems, known as Fiber Reinforced Cementitious Matrix (FRCM), is a very promising technique for retrofitting and strengthening the existing masonry or concrete structures. The effectiveness of FRCM systems is strongly related to the interface bond between inorganic matrix and fabric reinforcement, and, since the major weakness is often located on this interface, the study of stress-transfer mechanisms between fibers and matrix becomes of fundamental importance.FRCM are usually reinforced with uni-directional or bi-directional fabrics consisting of multifilament yarns made of carbon, glass, basalt or PBO fibers, disposed along two orthogonal directions. The difficulty of the mortar to penetrate within the filaments that constitute the fabric yarns and the consequent non-homogeneous stress distribution through the yarn cross section makes difficult to access the characterization of the composite material. The use of polymer coatings on the fibers surface showed to enhance the bond strength of the interface between fibers and mortar and, as a consequence, to improve the mechanical performance of the composite. The coating does not allow the mortar to penetrate within the filaments while is able to improve the bond between the two materials and to increase the shear stress transfer capacity at the interface.An experimental session of several pull out tests on carbon yarns embedded in a cementitious matrix was carried out. Different embedded lengths have been analyzed, equal to 20, 30 and 50 mm. The carbon yarns object of this study were pre-impregnated with a flexible epoxy resin enhanced with a thin layer of quartz sand applied on the surface.A variational model was proposed to evaluate the pull-out behaviour and failure mechanisms of the system and to compare numerical results to the experimental outcomes. Evolution of fracture in the yarn-matrix system is determined by solving an incremental energy minimization problem, acting on an energy functional which account for brittle failure of matrix and yarn, and for debonding at the yarn-matrix interface. The model was able to accurately describe the three phases of the pull-out mechanism, depending on the embedded length.