Poly P-phenylene Benzobisoxazole Fibers Research Articles

Radiation effect on stability and interfacial property of PBO fibers through high energy electron beam

Poly-p-phenylene benzobisoxazole (PBO) fibers have been studied and applied in many extreme environments owing to their excellent physical, mechanical properties and great chemical inertness. Here, radiation effect on PBO fibers is investigated through high energy electron beam with a high adsorbed dose up to 100 MGy. Changes of structure, mechanical strength, molecular weight and interfacial property are investigated in detail. It can be found that the structure and mechanical strength do not change obviously. Results of XPS and relative viscosity retention rate show a high radiation resistance of PBO fibers at below 10 MGy. Though PBO fibers can be degraded under over 50 MGy in a certain degree, the relative viscosity retention rate is still over 85% even at the absorbed dose of 100 MGy. Results of optical contact angle and interfacial shear strength of fiber/epoxy composite indicate the interfacial reaction activity decreases under 100 MGy. Therefore, it can be inferred that PBO fibers show a high radiation stability and an increasing trend of the interfacial inertness with the increase of absorbed dose. Through this work, it can provide references for PBO fibers application in the extreme environment.

Dynamic Mechanical Properties of Several High-Performance Single Fibers.

High-performance fiber-reinforced composites (FRCs) are widely used in bulletproof structures, in which the mechanical properties of the single fibers play a crucial role in ballistic resistance. In this paper, the quasi-static and dynamic mechanical properties of three commonly used fibers, single aramid III, polyimide (PI), and poly-p-phenylenebenzobisoxazole (PBO) fibers are measured by a small-scale tensile testing machine and mini-split Hopkinson tension bar (mini-SHTB), respectively. The results show that the PBO fiber is superior to the other two fibers in terms of strength and elongation. Both the PBO and aramid III fibers exhibit an obvious strain-rate strengthening effect, while the tensile strength of the PI fiber increases initially, then decreases with the increase in strain rate. In addition, the PBO and aramid III fibers show ductile-to-brittle transition with increasing strain rate, and the PI fiber possesses plasticity in the employed strain rate range. Under a high strain rate, a noticeable radial splitting and fibrillation is observed for the PBO fiber, which can explain the strain-rate strengthening effect. Moreover, the large dispersion of the strength at the same strain rate is observed for all the single fibers, and it increases with increasing strain rate, which can be ascribed to the defects in the fibers. Considering the effect of strain rate, only the PBO fiber follows the Weibull distribution, suggesting that the hypothesis of Weibull distribution for single fibers needs to be revisited.

Flexural and Tribological Properties of Polyimide Composites Reinforced by Poly-p-Phenylenebenzobisoxazole Fibers with Different Content

In this paper, the tribological property of polyimide (PI) resin was improved by adding poly-p-phenylenebenzobisoxazole (PBO) fibers. The effects of PBO fiber volume fraction were studied by mechanics and tribology tests. The fracture and wear surfaces of PBO/PI composites were investigated by using scanning electron microscopy (SEM). The measurement showed that the flexural properties of composites reinforced by 10 vol% PBO fibers were lower than pure PI resin. With the increase of PBO fiber content, the flexural strength was first increase and then decrease. The frictional coefficient and wear rate of the PBO/PI composites varied with the variety of fiber content, and the optimum parameter was obtained at 20 vol%. The dominant wear mechanism and friction process were discussed on the basis of microscopic morphology analysis of wear surface of PBO/PI composite and the counterpart.

Corrosion degradation behavior of PBO fibers under strong inorganic acid

Known as the super fiber of the twenty-first century, poly-p-phenylenebenzobisoxazole (PBO) fibers exhibit outstanding strength and modulus, fire and heat resistance, which are superior to those of poly-p-phenylene terephthalamide fiber. However, the poor resistance of acid corrosion is regarded as a fatal weakness, which restricts its application in complicated chemical environment. In present work, PBO fibers were exposed in strong acid solutions under different conditions, and then, surface morphology was observed by optical microscopy and scanning electron microscopy. Substantial changes in functional groups were investigated by Fourier-transform infrared (FTIR) spectroscopy, as well as changes in crystalline structure using differential scanning calorimetry (DSC) and thermal stability using thermogravimetric analysis (TGA). After treatment by H2SO4 and HNO3 solution, the strength of the fibers declines typically, while the modulus increases. It is attributed to the formation of N–H bonds in the vicinity of 3410.0 cm−1 confirmed by FTIR spectra. Hydrogen bonds, derived from N–H bonds, increase the thermal degradation temperature from 716.4 °C (untreated) to 725.6 °C (treated by H2SO4), shown in TGA curves. HNO3 treatment is more destructive than that of H2SO4. There exist longitudinal corrosion cracks after treatment by HNO3 solution. Furthermore, HNO3 solution penetrates into crystalline region and destroys the ordered crystal structure of PBO fibers demonstrated by DSC results.

Probabilistic model for structural mechanics of fiber bundle and its application to PBO fiber

The stress-strain relationship of single fiber and fiber bundle based on the different strain distribution functions of single fiber, including rectangular distribution, normal distribution and Weibull distribution, was studied. Strain distribution of Poly-p-phenylene benzobisoxazole (PBO) single fiber was measured, and the stress-strain curve of PBO fiber bundle can be deduced from the different strain distribution functions of single fiber. The results showed that normal distribution was closer to the measured strain distribution of PBO single fiber than rectangular distribution, and the stress and strain values of PBO fiber bundle estimated by the normal distribution were closer to the measured stress and strain values of PBO fiber bundle. In addition, the stress and strain values of PBO fiber bundle estimated by Weibull distribution were between those of rectangular distribution and normal distribution. In a word, the normal distribution can be effectively used to predict the fracture process of PBO fiber bundle.

Friction and Wear Behavior of Polyimide Composites Reinforced by Surface-Modified Poly-p-Phenylenebenzobisoxazole (PBO) Fibers in High Ambient Temperatures.

(1) In order to improve the properties of antifriction and wear resistance of polyimide (PI) composite under high temperature conditions, (2) 3-Aminopropyltriethoxysilane (APTES) and Lanthanum (La) salt modifications were employed to manufacture poly-p-phenylenebenzobisoxazole (PBO)/PI composites with different interface properties. The representative ambient temperatures of 130 and 260 °C were chosen to study the friction and wear behavior of composites with different interface properties. (3) Results revealed that while both modification methods can improve the chemical activity of the surface of PBO fibers, the La salt modification is more effective. The friction coefficient of all composites decreases with the increase of sliding velocity and load at two temperatures, and the specific wear rate is increases. Contrary to the situation in the 130 °C environment, the wear resistance of the unmodified composite in the 260 °C environment is greatly affected by the sliding velocity and load, while the modified composites are less affected. Under the same test parameters, the PBO–La/PI composite has the lowest specific wear rate and friction coefficient, and (4) La salt modification is a more effective approach to improve the properties of antifriction and wear resistance of PI composite than APTES modification in high ambient temperatures.

Interfacially enhancement of PBO/epoxy composites by grafting MWCNTs onto PBO surface through melamine as molecular bridge

Melamine and multi-walled carbon nanotubes (MWCNTs) were grafted onto Poly-p-phenylene benzobisoxazole (PBO) fiber surface effectively via layer-by-layer method. Both of them have been chemically bonded as fourier transform infrared spectroscopy (FTIR) confirmed. Grafting melamine overcame the inertness of PBO surface. Ammoniation was processed on PBO surface through grafting melamine so that the MWCNTs could be grafted onto PBO surface. Scanning electron microscopy (SEM) images indicated that melamine used as molecular bridge could increase MWCNTs’ quantity on PBO surface. X-ray photoelectron spectroscopy (XPS) results revealed the variation of chemical composition of PBO surface. Test of interfacial shear strength (IFSS) and tensile strength indicated the great mechanical properties of modified PBO fibers when combining with epoxy resin. Furthermore, whole reaction was processed under a simple condition. Results in this research also promised a potential method to modify PBO surface.

Investigation of reactivity and biocompatibility poly-p-phenylene benzobisoxazole fiber grafted hyperbranched polysiloxane

Abstract Hyperbranched polymer was synthesized via Michael addition. The biocompatible peptide was incorporated into hyperbranched polymer. As a result, they are promising candidates for cell adhesive molecular. Herein, we developed a strategy for synthetic hyperbranched polymer based on polysiloxane. A poly-p-phenylene benzobisoxazole (PBO) fiber as substrate, polyhedral oligomericsilsesquioxane (POSS) as core, prepared hyperbranched polymer was grafted to surface of PBO fiber. Experiment results show that hyperbranched polysiloxane was uniformly grafted onto the PBO fiber and significantly increase the surface activity. In addition, the functional PBO fiber as substrate presents biocompatible based on activity peptide. Hela cell selectively adhered on surface functional PBO fiber with activated peptide spots. Thus, the results of this study further extend the application of engineered polymer materials to cell biology.

キンク損傷を有するPBO繊維の疲労強度特性

In this study, fatigue strength properties of PBO (Poly-p-Phenylene Benzobisoxazole) fiber with kinking damage were investigated in monofilament fatigue tests. Two types of the PBO fibers were used in the experiment. One was the conventional type (AS fiber). The other was high-modulus type (HM fiber) with a higher crystal orientation than AS fiber. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod set to 0.625 mm. Load-controlled fatigue tests were carried out using a sinusoidal load with frequency 10 Hz and stress ratio of R = 0.5, and the load cell capacity was 10 N. It was found that fatigue strength with kinking damage was lower than that without kinking damage in neither AS fiber and HM fiber. Fatigue strength decrease of AS fiber and HM fiber with kinking damage in a low cycle area was larger than that in a high cycle area. The fatigue fracture of PBO fiber with kinking damage presented the different aspect at a high cycle area and a low cycle area in neither AS fiber and HM fiber.

Novel Fine Structures in poly-p-phenylenebenzobisoxazole (PBO) Fibers Induced by Water Vapor, Hot Water, and Nonaqueous Coagulation III. Random and Radial Preferential Orientations of the Crystal b-Axis

ABSTRACTThe preferential orientation of the crystal b-axis in PBO fibers was estimated from the diffraction intensities of micro-focus X-ray diffraction patterns. The observed X-ray diffraction intensities were compared with the calculated scattering volume in the fiber, with the crystal planes of the (010) and () giving coherent X-ray diffraction intensities on the detector. The calculation for the scattering volume was carried out based on an extended method of a previously-proposed two-phase model, which was utilized to predict the scattering volume by searching for the suitable crystal planes in the fiber according to Bragg's Law. Agreement was achieved between the predicted and measured intensity profiles for the (200) and () diffraction intensity profiles.

A Novel Composite Poly-p-Phenylenebenzobisoxazole (PBO) Fiber Including Molecularly-Dispersed Copper Phthalocyanine in the Structure

ABSTRACTThe possibility to make a composite poly-p-phenylenebenzobisoxazole (PBO) fiber including a second component without distorting its original structures and mechanical properties was examined. Copper phthalocyanine was found to fulfill the above-mentioned condition and can be dispersed in the fiber molecularly. It was shown that part of the embedded copper phthalocyanine can be aligned one-dimensionally with periodicity along the fiber axis in the fiber. The color of the resultant fiber was dark blue, which is different from the original fiber having its yellowish golden color. According to X-ray diffraction analysis the preferential orientation of the a-axis of the PBO crystal was slightly more oriented by the addition of copper pthalocyanine than that of the pure PBO fiber, but the crystal size of PBO wasn't also affected. We thus show the possibility of adding a second material that can add additional properties to the fiber, but keeping the original high mechanical properties and oriented structures.

キンク損傷を有する高弾性率タイプPBO繊維の疲労強度

In this study, fatigue strength of high-modulus type PBO (Poly-p-Phenylene Benzobisoxazole) fiber with kinking damage was investigated in monofilament fatigue tests. PBO fiber is high polymer material and has the highest tensile strength and tensile modulus of elasticity in any polymeric fiber. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 0.625 mm. Average value of compressive strain on surface of fiber determined based on the diameter of steel rod was -1.71 %. Load-controlled fatigue tests were carried out using a sinusoidal load with frequency 10 Hz and stress ratio of R = 0.5, and the load cell capacity was 10 N. It was found that fatigue strength of PBO fiber with kinking damage was lower than that of PBO fiber without kinking damage. Fatigue strength decrease of PBO fiber with kinking damage in a low cycle area was larger than that in a high cycle area.

818 キンク損傷がPBO繊維の引張破壊挙動に及ぼす影響(GS4-4 材料力学・計算力学)

In this paper, effect of kinking damage on tensile fracture behavior of poly-p-phenylene benzobisoxazole (PBO) fiber was investigated in monofilament tests. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 5, 2.5, 1.25 and 0.65 mm. Kinking damage density was defined to evaluate occurrence of kinking damage owing to bundle fiber was wound onto the steel rod. The fracture surface was observed using Scanning Electron Microscope (SEM). It was found that the tensile strength of fiber with kinking damage was well fitted the Weibull distribution function with 2 parameters. The tensile strength of PBO fiber with kinking damage was explained in the concept of the effective volume. It was shown that the crack growth of PBO fiber with kinking damage developed along the kinking damage.

Morphological studies of poly-p-phenylenebenzobisoxazole (PBO) fibers on the process that determines the direction of the crystal a-axis along the radius direction during the formation of fiber structures

This article concerns preferential orientations of the crystal a-axis for the standard type PBO AS and high modulus type HM fibers. The degree of radial preferential orientation of the crystal a-axis along the fiber radius direction was analyzed based on a newly-proposed 3D two-phase model. The result was compared with the previously analyzed three PBO fibers made through water vapor, hot water and non-aqueous coagulation processes. The proposed model fitted well the measured micro-focus X-ray scattering patterns of the (200) crystal plane as a function of the position of the fiber on which the source beam was focused. The crystal orientation of the c-axis was strictly estimated from the three equatorial diffractions based on Wilchinsky's generalized model.

Novel Fine Structures in Poly-p-phenylenebenzobisoxazole Fibers Induced by Water Vapor, Hot Water, and Non-Aqueous Coagulation II Random and Radial Preferential Orientations of the Crystal a-Axis

The preferential orientation of the a-axes of poly-p-phenylenebenzobisoxazole (PBO) crystals in PBO fibers made with differential coagulation processes is characterized. Electron diffraction and micro-focus X-ray diffraction were carried out for this purpose. To estimate the alignment quantitatively a two-phase model is proposed and the calculated X-ray diffraction profiles fit well with the measured profiles. Water vapor coagulation at high temperature gave mostly almost random preferential orientation while a non-aqueous coagulation produced radial orientation. The fibers made with hot liquid water coagulation were characterized as a middle form between the limits of radial and random orientations.

Structure performance of UVA and UVB light irradiated poly-p-phenylene benzobisoxazole fiber (PBO)

Abstract By UVA and UVB irradiating, the performance of poly-p-phenylene benzobisoxazole (PBO) fiber is changed with an increase in irradiation time, and the surface morphology, chemical structure, mechanical performance and thermal properties of the fiber are poorer. After 320-h irradiation, the properties of the PBO fiber irradiated by UVB are stronger than those irradiated by UVA. The strength of PBO fiber irradiated by UVB and UVA declined by 40% and 20%, respectively, than that of non-irradiated fiber. The roughness of fiber surface improved, and there was corrosion on the surface of PBO fiber irradiated by UVB. After the UV irradiation, the degree of macromolecule crystallinity and orientation changed, the macromolecule chain is broken, new groups (-NO2) are produced in the PBO fiber, and the temperature (660°C) of the thermolysis is decreased by 100°C from that of fibril.

Tensile Strength of Surface Treated PBO Fiber

Poly p-phenylene benzobisoxazole (PBO) fiber is a kind of organic fiber with high performance, but the properties of the interface between PBO fiber and resin are poor, which limit its application in the field of composite materials. Therefore, the surface modification methods were employed to enhance the interface properties, which could damage the fiber. This article assessed the influence of plasma modification, γ-ray irradiation, coupling agent, acid treatment and combined treatments on the strength of PBO fiber filament, and investigated its tensile strength with Weibull analysis. Through observation of fiber surface by SEM，it can be found that some combined treatments caused less damage to PBO fiber compared to the individual treatments. This indicates that if combining the different treatments appropriately, the interface energy of PBO fiber will increase, with the excellent mechanical properties well retained

G0300803 キンク損傷を有するPBO繊維の紫外線照射による強度低下要因の検討

In this paper, residual strength of poly-p-phenylene benzobisoxazole (PBO) fiber with kinking damage under ultraviolet irradiation was investigated in monofilament tests. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 5, 2.5, 1.25 and 0.65 mm. Kink damage density was defined to evaluate occurrence of kinking damage. UV irradiation time was 1 and 10 h, the irradiation intensity was 8 W/m^2. It was found that the residual strength of fiber with kink damage decreased with increasing kink damage density. When the PBO fiber with kink damage was subjected to ultraviolet light, the residual strength is greatly reduced due to the auto-oxidation generated in the kink damaged region.

Effects of light stabilizer on the ultraviolet stability of poly-p-phenylenebenzobisoxazole (PBO) fibers

A UV-resistant PBO fiber containing light stabilizer OB-1(2,2′-(1,2-ethenediyldi-4,1-phenylene) bis-benzoxazole) is reported. OB-1/PBO Fiber, which had excellent mechanical properties as PBO was prepared via in situ polymerization and dry-jet wet-spinning technique. Effects of the light stabilizer (OB-1) on UV stability of PBO fiber and possible degradation mechanism were investigated by tensile testing, intrinsic viscosity measurement, SEM, and ATR-FTIR analysis. Under UV-accelerated aging, the tensile strength of PBO fiber declined sharply. After exposed to UV 340-nm light for 310 h, the strength retention was only 44.17 %. SEM analysis showed the smooth and compact surface with well-oriented microfibrils was damaged. Meanwhile, the photostability of PBO fiber could be enhanced greatly by adding a small amount (0.05–0.2 %) of OB-1. Under the same conditions, the strength retention of 0.2 %OB-1/PBO fiber increased to 64.84 %, which was 47 % higher than that of PBO fiber. SEM observation showed the surface of OB-1/PBO fiber was also damaged, but it was not as so severe as PBO fiber. After UV irradiation, the intrinsic viscosity of PBO and OB-1/PBO fiber decreased which implies that mild chain scissions occurred. ATR-FTIR analysis revealed that oxazole rings in PBO and OB-1/PBO backbone were disrupted and formed amide linkages. These results indicated the loss of strength is mainly due to the break of microfibrils and fiber morphology, mild chain scission, and the disruption of oxazole rings.

Effect of Surface Modification on Mechanical and Tribological Performance of Poly-p-phenylenebenzobisoxazole Fiber-Reinforced Polyimide Composite

This work examined the effect of coupling agent surface modification of Poly-p-phenylenebenzobisoxazole (PBO) fibers on mechanical and tribological performance of PBO fiber-reinforced thermoplastic polyimide (PBO/PI) composites. The results show that tensile strength and flexural strength are largely improved by coupling agent treatment. Under dry sliding conditions, coupling agent treatment is effective to reduce the wear of PBO/PI composite. The principle of improvement in interfacial adhesion between PBO fiber and PI matrix after coupling agent treatment was discussed. The surface characteristics of PBO fibers were characterized by X-ray photoelectron spectroscopy (XPS). It is found that the content of polar groups on the surface of PBO fiber treated by coupling agent increases compared with the untreated fiber. The presence of polar groups is probably leading to an increment of interfacial binding force between fibers and matrix in a composite system, and accordingly enhances the mechanical and tribological properties.