Poly P-phenylene Benzobisthiazole Research Articles

Fiber hybrid polyimide‐based composites reinforced with carbon fiber and poly‐p‐phenylene benzobisthiazole fiber: Tribological behaviors under sea water lubrication

Fiber hybrid polyimide‐based (PI‐based) composites reinforced with carbon fiber (CF) and poly‐p‐phenylene benzobisthiazole (PBO) fiber of different volume fractions were fabricated by means of hot press molding technique, and their mechanical properties and tribological behaviors under sea water lubrication were systematically investigated in relation to the synergism of CF and PBO fiber. Results showed that the incorporation of CF or PBO fiber improved the tensile strength, hardness, and wear resistance of PI. More importantly, because of the synergistic enhancement effect between CF and PBO fiber on PI matrix, the combination of 10%CF and 5%PBO fiber reinforced PI‐based composite had the best mechanical and tribological properties, showing promising application in ocean environment. POLYM. COMPOS., 37:1650–1658, 2016. © 2014 Society of Plastics Engineers

Preparation and characterization of nanocomposites of poly-p-phenylene benzobisthiazole with graphene nanosheets

Poly-p-phenylene benzobisthiazole (PBT)/graphene nanocomposite films were fabricated using a simple method with methanesulfonic acid (MSA) as the processing solvent. In this approach, graphene nanosheets were exfoliated in the MSA solution of PBT using ultrasonication and mechanical stirring, and then processed into thin films. The structure and composition of as-prepared graphene oxide (GO) and reduced graphene oxides (rGO) were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrical conductivity of pristine PBT was enhanced by 10 orders of magnitude upon incorporation of 5 wt% rGO nanosheets. The enhanced conductivity of the nanocomposites was interpreted by the percolation model. The thermo-oxidative stability of PBT was improved with the incorporation of both GO and rGOs, while rGOs showed more pronounced effect. On addition of only 5 wt% GO, the tensile strength and Young's modulus of PBT increased by ∼4-fold and ∼7-fold, respectively, whereas relatively inferior tensile properties were observed for the PBT/rGO nanocomposites. The enhanced mechanical properties could be attributed to the molecular-level dispersion of the exfoliated GO nanosheets in PBT matrix, as evidenced by the results from morphological studies. A modified Halpin–Tsai model has been used to evaluate the reinforcement or orientation effects of GO/rGO on the Young's modulus of the nanocomposites.

Influence of plasma treatment time on plasma induced vapor phase grafting modification of PBO fiber surface

The surface of poly-p-phenylene benzobisthiazole (PBO) fibers was treated through oxygen plasma induced vapor phase grafting (PIVPG) method under various oxygen plasma pre-treatment time conditions. The surface chemical composition, surface morphologies and surface free energy of pristine and treated PBO fibers were studied using X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and Cahn DCAA system. The mechanics property of these fibers was evaluated by tensile strength and interfacial shear strength (IFSS). It was found that the surface characteristics of treated PBO fibers occurred significant change compare with the pristine PBO fibers. After treatment, the polar functional groups were introduced on the fiber surface. Carbon concentration decreased; oxygen concentration and elemental ratio of oxygen to carbon increased. Acrylic acid can react with the activated PBO fibers surface, which led to the fiber surface roughness increased. The surface free energy increased from 41.4mN/m to 62.8mN/m when PBO fibers were plasma pre-treated for 10min, while the IFSS of PBO fibers with epoxy resin increased from 36.6MPa to 55.8MPa. Therefore, PIVPG can be used to enhance the interfacial bond between PBO fibers and epoxy resin.

The Improvement of Wettability, Mechanical and Thermo-mechanical Performances of PBO Fiber/Epoxy Composites by Adding Reactive Carbon Nanotubes

A kind of reactive multi-walled carbon nanotubes (r-MWNTs) was prepared and incorporated in an epoxy matrix. Then the epoxy matrix containing 0.5 wt.% r-MWNTs was reinforced by poly-p-phenylene benzobisthiazole (PBO) fibers and the NOL-rings were prepared on a filament winding machine. The wettability of the uncured epoxy was evaluated by measuring the surface energy and viscosity. It was demonstrated that the epoxy with r-MWNTs exhibited much better wettability than that of pristine epoxy. After adding 0.5 wt.% r-MWNTs, the tensile strength, tensile modulus, elongation and interlaminar shear strength (ILSS) of NOL-rings demonstrated an enhancement of 11.02%, 1.86%, 16.52% and 61.1%, respectively, compared to the pristine epoxy composites. In addition, scanning electron microscopy (SEM) studies revealed that the addition of r-MWNTs could significantly improve the interfaces bonding between PBO fiber and epoxy matrix. The dynamic mechanical analysis results also showed that the glass transition temperature of the composites increased by about 5 °C after the addition of 0.5 wt.% r-MWNTs.

Pbzt Microcomposites with Advanced Thermoplastic Matrices

ABSTRACTThermoplastic microcomposites offer the potential for better economics and improvements in composite processing, and possibly performance, over conventional ‘string-and-glue’ composites. The early development of molecular composite technology focused on polyamide matrix polymers; however, for many aerospace applications higher use temperatures and greater solvent resistance than that of conventional polyamide matrices will be required. This paper describes work performed under contract to the U.S. Air Force to develop PBZT (poly p-phenylene benzobisthiazole)/thermoplastic molecular composites with high performance matrix resins into a viable technology.A scaleable process has been defined based on a novel technology developed by Du Pont. Advantages of this process include better economics, superior processing performance, and improved MC fiber tensile properties versus prior art. Using this process we have obtained rule-of-mixtures properties in our microcomposite fibers with matrix polymers offering use temperatures from 330 to 600°F. Consolidation of PBZT/PEKK fibrous preforms into uniaxial panels up to 1011 × 1511 has been demonstrated and material propperty evaluation and data base development are in progress. Uniaxial property levels achieved to date for all systems compare favorably with conventional ‘string-and-glue’ PBZT/epoxy composites although as with other organic fiber reinforcements, compressive and shear performance may be limiting factors in MC applications.

Calculation of limiting young's moduli of rigid-rod polymers including poly-p-phenylene benzobisthiazole (PBT)

Limiting Young's modulus along the chain direction has been calculated based on the lattice dynamical theory for the several rigid-rod polymers: 371.0 GPa for poly-p-phenylene benzobisthiazole (PBT) (macroscopic modulus ca. 250 GPa), 275.1GPa for poly-p-phenylene, 588.3GPa for poly-pbenzobisthiazole, and 505.3GPa for poly-p-phenylene pyromellitimide (macroscopic modulus ca. 130GPa). The difference in the Young's modulus among these polymers has been discussed based on the atomic displacements and potential energy distribution calculated for the tensile deformation of the chains. Tentative band assignments of the infrared and Raman spectra of PBT were made in order to check the propriety of the force field used in the above calculation.

Analytical Electron Microscopy of a Polymer Blend

A polymer blend which is composed of poly-p-phenylene benzobisthiazole (PBT) and poly-2,5(6)benzimidazole (ABPBI) has been processed into both a phase-separated material and a “molecular composite”. In the molecular composite, the PBT and ABPBI components are dispersed at a scale finer than 3 nm. This results in high mechanical properties as the rod-like, high strength PBT reinforces the flexible-coil ABPBI matrix. In the phase- separated blend, micron-sized aggregates form within a more ductile matrix. This study qualitatively examines the structure and composition of the phase- separated 20% PBT / 80% ABPBI blend using the analytical electron microscopy (AEM) techniques of energy dispersive x-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), and microdiffraction. Beam damage of the components is also considered.

Composites on a molecular level: Phase relationships, processing, and properites

Abstract Phase relationships in concentrated solution and in the bulk of a solvent/rigid-rod/flexible-coil system were investigated. The solvent was a mixture of two strong acids. The rigid-rod polymer was poly-p-phenylenebenzobisthiazole (PBT). The flexible-coil polymer was poly-2,5(6)benzimidazole (ABPBI). The concentrated solution and bulk morphologies were investigated by means of polarized optical microscopy, small-angle light scattering, scanning electron microscopy, and wide-angle x-ray diffraction techniques. Above a critical concentration, Ccr, the pseudo ternary solution separated into two coexisting phases, one optically anisotropic (liquid crystalline) and the other isotropic. The anisotropic domains were highly birefringent. They contained primarily the PBT macromolecules oriented perferentially along a domain axis. Numerical values of Ccr, determined experimentally, were in good agreement with calculated predictions. Aggregates composed of PBT molecules were observed to be dispersed in a con...