Polycarbonate Fibers Research Articles

Electrospun mat of tyrosine-derived polycarbonate fibers for potential use as tissue scaffolding material

Desaminotyrosyl-tyrosine ethyl ester (DTE) and desaminotyrosyl-tyrosine (DT) were used as monomers in the synthesis of two tyrosine-derived polycarbonates: the slow degrading homopolymer poly(DTE carbonate) and the fast degrading co-polymer poly(DTE-co-20%DT carbonate). Ultrafine fibers of these polymers were successfully fabricated using an electrospinning process. The effects of some solution and process parameters (i.e., polymer concentration, electrostatic field strength and solvent system) on morphological appearance and diameters of the obtained fibers were investigated by scanning electron microscopy (SEM). Smooth fibers were obtained at high enough solution concentrations (i.e., 15 and 20% (w/v)). The average fiber diameter was found to increase with increasing polymer concentration and applied electrostatic field strength. The electrospinnability of poly(DTE-co-20%DT carbonate) in dichloromethane was enhanced when methanol was used as the co-solvent. In all of the conditions investigated, the average diameter of the obtained smooth fibers ranged between 1.9 and 5.8 μm. A qualitative assessment of an as-spun mat of poly(DTE carbonate) fibers as a tissue scaffolding material showed that three different cultured cell lines appeared to adhere and propagate well within the scaffold. For poly(DTE carbonate) exceptionally high cell densities could be achieved after 10 days of cell culture.

Anisotropic microstructure-impact fracture behavior relationship of polycarbonate/polyethylene blends injection-molded at different temperatures

Polycarbonate (PC)/polyethylene (PE) blend was injection molded at three temperatures: 190, 230 and 275 °C. Due to different deformability of PC phase at the different molding temperatures, the blends exhibit different morphologies. The sample molded at 190 °C only contained many uniformly dispersed spherical PC particles due to the incapability of flow and deformation of PC phase at this temperature. The samples molded at both 230 and 275 °C showed typical anisotropic (skin–core) structures, and there were many injection-induced PC fibers in the sub-skin layer. The DSC measurement showed that higher molding temperature leads to higher crystallinity and more perfect crystals of PE phase. The impact fracture of three bars behaves differently in the following aspects: (1) overall fracture surface, (2) craze and micro-void formation (stress whitening), (3) fibrillation of PE, and (4) plastic deformation of PC dispersed phase. As the molding temperature increases, the stress whitening becomes stronger, the shear lips become thicker, the amount of the stick–slip lines and the micro-voids increases, and the voids become smaller. Moreover, upon impact fracturing, numerous fibrils of PE were formed in 230- and 275-bars, at the same time, obvious plastic deformation of PC fibers occurred in the 275-bar. All these microscopic features demonstrate the impact toughness increases with molding temperature. Lamellae texture evolution and high interfacial contact were employed to partially interpret the impact fracture behavior. Numerous filaments generated around PC particles on the fracture surfaces, which bridged the PC particles and PE matrix, indicated a high interfacial adhesion between PC particles and PE matrix.

Morphology Dependent Double Yielding in Injection Molded Polycarbonate/Polyethylene Blend

AbstractSummary: Polycarbonate (PC)/polyethylene (PE) blend was injection molded at different molding temperatures. The morphological observation by scanning electronic microscope (SEM) indicated that the sample molded at 190 °C contained only uniformly dispersed spherical PC particles. The samples molded at 230 and 275 °C had a typical skin‐core structure, and there were many injection‐induced PC fibers in the subskin. While the sample molded at 190 °C had the usual stress‐strain behavior, the samples obtained at 230 and 275 °C showed apparently double yielding behavior. It was suggested that the double yielding points were morphology‐dependent. The first one was the result of the yielding of PE at low strain, and the second one was caused by the yielding of the PC fibers. Moreover, it is the frictional force in the interfaces between PC and PE that transferred the stress to the PC fibers, hence giving rise to the reinforcement of PE by PC.Stress‐strain curves of PC/PE blends injection molded at various temperatures showing first (I) and second (II) yielding points.magnified imageStress‐strain curves of PC/PE blends injection molded at various temperatures showing first (I) and second (II) yielding points.

Electrospinning of polycarbonate nanofibers with solvent mixtures THF and DMF

The current work demonstrates the electrospinning of polycarbonate dissolved in solvent mixtures of tetrahydrofuran (THF) and dimethylformamide (DMF) to obtain fibers on a nanoscale. The solvent mixtures played a significant role on the morphology of the fibers. The spun fibers showed the characteristics of strong networking with each other as the THF ratio was increased in the solvent mixtures (like 60:40, 70:30 of THF:DMF). The electrostatic voltage, viscosity and surface tension also showed major effects on the fiber morphology and formation of beads. At lower THF and DMF ratios and lower spinning voltages, the bead revealed a globular mushroom shape, while at higher ratios and higher voltages, the beads formed the shape of spindle. The microstructures of the electrospun polycarbonate fibers were quantitively investigated by Scanning Electron Microscope (SEM) and Transmission Electron Microscope as a function of processing variables.

Morphological study of electrospun polycarbonates as a function of the solvent and processing voltage

Unlike conventional spin methods, electrospinning is capable of yielding fibers with sub-micron range diameters and high specific surface areas. In this study a Bisphenol-A polycarbonate was electrospun using two solvents: Chloroform and a 1:1 mixture of Tetrahydrofuran (THF) and Dimethylformamide (DMF). The morphological features of the electrospun polycarbonate fibers have been studied as a function of the solvent used and also as a function of the processing voltage. The studies were conducted using the SEM, TEM and Scion image analysis program. The results indicate that the morphological features of the fiber such as fiber diameter, diameter-distribution, internal structure and the Bead density variation with voltage are dependent on the solvent used. Electrospun polycarbonate fibers also exhibit a “Raisin like” puckered structure. However, such a feature is independent of the solvent used, and could enhance the functional efficiency of an electrospun material when used in an area-based application. In addition, studies on crazing of bulk polycarbonate and the surface features of electrospun polycarbonate fibers have been conducted. Results indicate that crazing of bulk polycarbonate results in surface damage and features that are also seen on the surface of electrospun polycarbonates.

Morphology in Immiscible Polymer Blends During Solidification of an Amorphous Dispersed Phase under Shearing

AbstractSolidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene‐methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break‐up times of PC fibers were taken into account. Shear rate and quenching‐time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching.

Microstructures of Electrospun Polycarbonate Fibers With Solvent Mixture THF and DMF by SEM/TEM

Microstructures of Electrospun Polycarbonate Fibers With Solvent Mixture THF and DMF by SEM/TEM

Preparation and Characterization of Nanometer-scale Polycarbonate Fibers: Bead Formation

ABSTRACTElectrospinning is a superior process compared to other conventional spinning methods for the production of fibers in the sub-micron to nanometer scales. Such fiber membranes have exceptionally large surface areas and small pore sizes. The process requires an electrostatic force, which induces charges on the liquid droplet of the polymer solution or melts and therefore overcomes the surface tension and viscoelasticity forces to create an electrically charged jet. When the jet dries or solidifies, an electrically charged fiber remains, which can be directed or accelerated by the electrical forces and then collected in non-woven fiber membrane or other useful shapes. The present research work demonstrates the electrospinning of polycarbonate solution with solvent mixtures THF (Tetrahydrofuran) and DMF (Di-methyl formamide) to produce nanometer scale polycarbonate fibers. The solvent mixture of THF and DMF was the major parameter for producing nano-polycarbonate fibers along with the formation of byproducts beads. The electrostatic voltage, viscosity and surface tension also showed significant effect on bead formation and bead density. The microstructures of the polycarbonate beads were quantitvely investigated by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM).

Electrospinning of Polycarbonates and their Surface Characterization using the SEM and TEM

ABSTRACTUnlike conventional spin methods, electrospinning is capable of yielding fibers with sub-micron range diameters and high specific surface areas. The use of such electrospun materials in applications, whose functionality depends on the area available, such as separation processes, will be useful. In this study a Bisphenol-A polycarbonate was dissolved in two solvents: Chloroform and a 1:1 mixture of Tetrahydrofuran (THF) and Dimethylformamide (DMF) and resulting polycarbonate solutions were then electrospun to produce polycarbonate fiber-mats. The morphological features of the electrospun polycarbonate fibers have been studied as a function of the solvent used and also as a function of the processing voltage. The studies were conducted using the SEM, TEM and Scion image analysis program. The results indicate bold differences in the fiber morphology and bead density trends with the solvent used. Electrospun polycarbonate fibers exhibit a “Raisin like” puckered structure. Such a structure will enhance the functional efficiency of an electrospun material when used in an area-based application. In addition, studies on crazing of bulk polycarbonate and the surface features of electrospun polycarbonate fibers have been conducted. Results indicate a relation between crazing and the topological features of electrospun polycarbonates.

A novel TLCP blended with PET and PC matrices

AbstractThis investigation focused on the potential of improving the performance of poly(ethylene terephthalate) (PET) and polycarbonate (PC) fibers by incorporating a novel thermotropic liquid crystalline copolymer (TLCP). The degree of mechanical enhancement obtained in the fibers incorporating 20 wt % TLCP depended upon the chosen matrix material and the processing conditions. The PET matrix systems did not exhibit any modulus improvements until after posttreatment of the fibers. Following posttreatment, the blends exhibited a modulus of 24 GPa, an increase of 40% compared to the PET control fiber. The PC systems exhibited a 1 GPa modulus increase in the as‐spun fiber blends, but improvement was negligible after fiber posttreatment. The morphologies of the as‐spun and posttreated fibers suggest that different mechanisms of reinforcement are occurring depending upon the matrix material selected. © 1994 John Wiley & Sons, Inc.

Different in vitro generation of C3d by cuprammonium and polycarbonate capillary hemodialyzers.

Cellulosic membranes have been shown to activate C3 via the alternative pathway. Generation of the stable product C3d was compared in polycarbonate (PC) and cuprammonium (CU) hollow-fiber minidialyzers with identical geometry, using an in vitro recirculation system with platelet-poor plasma (recirculation rate 20 ml/min; 1,600 fibers; 0.115 m2; 40 ml system priming volume; recirculation time 120 min). After extensive washing, residual protein was removed by reverse transmembrane pressure (1.5 bar) from the air-filled dialysate compartment. Such protein fraction, functionally defined as 'secondary membrane', was similar in quantity for PC and CU fibers. Plasma proteins were present in the membrane without selective adsorption (flat-bed polyacrylamide gel electrophoresis and rocket immunoelectrophoresis using monospecific antibodies). C3d, measured by immunoelectrophoresis, increased with time in the fluid phase compartment of both dialysers, but C3d generation was consistently and significantly (p less than 0.05) less in PC than in CU dialysers. The observation documents an activation of C3 with PC, in contrast to previous reports of no activation. However, C3 activation with PC was less intense than with CU.

Drawing behavior and mechanical properties of highly oriented polycarbonate fibers

AbstractFibers from bisphenol‐A polycarbonate are typical representatives of the less crystallizing synthetic fibers. Because of the high glass transition temperature, textiles produced from these fibers have outstanding laundry‐resistance and noncreasing properties. Polycarbonate fibers can be produced both by the dry or wet‐spin and by the melt‐spin process. The stretching of the fibers is carried out in accordance with the proposed textile characteristics below or above the glass transition temperature or by a special swelling–drawing process, in the course of which fibers of particularly high tenacity and elastic modulus can be obtained. The fibers produced by the latter process were investigated by a number of physical measurements of their morphological structure (density, birefringence, X‐ray wide‐ and small‐angle scattering, differential calorimetry, thermo‐mechanical analysis). These measured values of density, birefringence, and heat of fusion show that these fibers have a higher degree of crystallinity than the fibers produced by a melt or dry spinning process. Whereas with dry‐spun fibers an increase in tenacity can be obtained by raising the molecular orientation up to a limited tenacity value, it is possible with fibers produced by the swelling‐drawing process to virtually double the tenacity due to the higher crystallinity and improved crystal structure (creation of a large number of physical linkages). By means of X‐ray small‐angle scattering on annealed swollen‐drawn polycarbonate fibers, we were able to detect, for the first time, a marked two‐phase structure consisting of crystalline and noncrystalline regions with a long‐period of about 120 Å. With other crystalline polymers, a period of this kind has been known for many years.