Showing papers on "Polycarbonate published in 2003"

Complex permittivity measurements of common plastics over variable temperatures

Abstract: In this paper, we present complex permittivity data at microwave frequencies (approximately 10 GHz) for many common plastics over a temperature range of 122 to 375 K. The measurements were made with a TE/sub 01/spl delta// dielectric resonator placed inside an environmental chamber. Data are presented for the following materials: acrylonitrile butadiene styrene, polytetrafluoroethylene, cross-linked polystyrene, tetrafluorethylene-perfluorpropylene, polypropylene, polysulfone, polymethylmethacrylate, polyvinyl chloride, polycarbonate, high-density polyethylene, polyoxy-methylene (acetal homopolymer), and polyamide.

Surface Functionalization of Thermoplastic Polymers for the Fabrication of Microfluidic Devices by Photoinitiated Grafting

Abstract: Photografting has been used for the surface modification of a wide range of commercial commodity polymers such as poly- styrene, poly(methyl methacrylate), poly(dimethyl siloxane), polycarbonate, Parylene C, polypropylene, cyclic olefin copolymer, and hydrogenated polystyrene that are useful substrate materials for the fabrication of microfluidic chips. Since the chain propagation is initiated after UV light-activated abstraction of a hydrogen atom from the surface of channels within the materials, their permeability for UV light was tested and polyolefins were found to be the best candidates. A number of monomers with a variety of functional groups such as perfluorinated, hydrophobic, hydrophilic, reactive, acidic, basic, and zwitterionic have been successfully grafted from the surface of selected substrates, and the grafting efficiency determined using X-ray photoemission spectroscopy. Layered surface structures were prepared by consecutive grafting of different monomers. Our approach also enables photolithographic patterning of surfaces and specific functionalization of confined areas within the microchannel.

Melt mixing of polycarbonate/multi-wall carbon nanotube composites

Abstract: —Composites of polycarbonate (PC) with multi-wall carbon nanotubes (MWNT) of different concentrations are prepared by diluting a PC based masterbatch containing 15 wt% MWNT using melt mixing in a DACA-Micro Compounder (4 g scale). Electrical resistivity measurements indicate that the percolation of MWNT is reached between 1 and 1.5 wt%. In addition, melt rheology was applied as another sensitive method to detect the percolation of the nanotubes. Atomic Force Microscopy and visual observations of the composite dispersions in a PC-solvent were used to characterise the state of MWNT dispersion. Differential Scanning Calorimetry and Dynamic Mechanical Analysis were applied to detect changes in the glass transition temperature of PC as a result of processing and of MWNT interactions with the PC matrix including the state of dispersion. In addition, DMA confirmed the reinforcement effect of the nanotubes. The results show that the nanotube incorporation also influences the processing behaviour. Due to the enhan...

Dispersion and alignment of carbon nanotubes in polycarbonate

Abstract: Dispersion and alignment of carbon nanotubes in thermoplastic polymers such as polycarbonate have been studied. Dispersion was accomplished by mixing in a conical twin-screw extruder and alignment was carried out using a fiber-spinning apparatus. The effects of mixing time and fiber draw rates on dispersion and alignment were investigated. Uniform dispersions were produced with relatively short residence times in the extruder. Excellent alignment of carbon nanotubes in nanocomposite filaments was obtained when the fiber draw rate was greater than 70 m/min. The ability to closely control the dispersion and alignment of carbon nanotubes in polymers is expected to lead to the development of nanocomposites with desirable electronic and structural properties.

Intercalated Polycarbonate/Clay Nanocomposites: Nanostructure Control and Foam Processing

Abstract: Intercalated polycarbonate (PC)/clay nanocomposites (PCCN)s have been prepared successfully through the melt intercalation method in the presence of a compatibilizer. The internal structure and morphology of the PCCNs has been established by using wide-angle X-ray diffraction (WAXD) analyses and transmission electron microscopic (TEM) observations. The morphology of these nanocomposites and degradation of the PC matrix after nanocomposites preparation can be controlled by varying surfactants used for the modification of clay and compatibilizer. The intercalated PCCNs exhibited remarkable improvements of mechanical properties when compared with PC without clay. We also discuss foam processing of one representative PCCN using supercritical CO2 as a foaming agent. TEM bright field image of intercalated polycarbonate/synthetic fluorohectorite nanocomposite.

Plasticization of polymers with supercritical carbon dioxide: Experimental determination of glass-transition temperatures

Abstract: High-pressure partition chromatography, a modification of the inverse gas chromatography technique, is presented as suitable technique for the study of the plasticization effect of carbon dioxide on the following polymers: poly(methyl methacrylate), polystyrene, and bisphenol A–polycarbonate. Polymers in the presence of a compressed gas or a supercritical fluid become plasticized; this means that their glass-transition temperatures (Tg's) can be lowered by 10s of degrees, which causes changes in their mechanical and physical properties. CO2-induced plasticization has an important impact on many polymer processing operations in which the Tg depressions of the polymers can be evaluated. The experimental results are discussed and compared with data available from literature for each polymer we considered. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2189–2193, 2003

Physical properties of aliphatic polycarbonates made from CO2 and epoxides

Abstract: A homologous series of aliphatic polycar- bonates with different side-chain lengths was synthesized by ring-opening polymerization of terminal epoxides with CO2 using zinc adipionate as catalyst (patented process of Empower Materials (formerly PAC Polymers Inc.)). Addi- tionally, a polycarbonate was made having a cyclohexane unit in its backbone, together with a terpolymer having both cyclohexane and propylene units. After characterization of thermal properties the aliphatic polycarbonates were found to be completely amorphous. Polycarbonates derived from long-chain epoxides showed a glass-transition temperature (Tg) below room temperature, whereas polycarbonates de- rived from cyclohexene oxide showed a Tg of 105°C, the highest yet reported for this class of polymers. The initial decomposition temperature of the polymers in air and ni- trogen atmospheres was found to be less than 300°C. The mechanical properties and the dynamic mechanical relax- ation behavior of the polymers were also reported. The effect of the chemical structure on the physical properties of ali- phatic polycarbonates was discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1163-1176, 2003

Inorganic–organic hybrid coatings on polycarbonate.: Spectroscopic studies on the simultaneous polymerizations of methacrylate and silica networks

Abstract: Hybrid methacrylate–silica coatings derived from 3-(methacryloxypropyl)-trimethoxy silane were deposited on polycarbonate via hydrolysis–condensation reactions followed by UV curing ( λ =253.7 nm). The formation of –Si–O–Si– (inorganic backbone) and polymethacrylate (organic) networks leading to the generation of hybrid structure was monitored by UV and Fourier transform infrared (FTIR) spectroscopies. UV and FTIR spectra showed complete polymerization of methacrylate groups during UV curing of the coatings. The silica network was initially formed through the hydrolysis–condensation reactions of alkoxy groups in the sol as evident from the appearance of FTIR peaks due to –Si–O–Si– vibrations. Further silanol (Si–OH) condensation reactions leading to the generation of more silica network were occurred simultaneously with methacrylate polymerization during UV photo curing of the coating.

Thermally conductive nylon 6,6 and polycarbonate based resins. I. Synergistic effects of carbon fillers

Abstract: Increasing the thermal conductivity of typically insulating polymers, such as nylon 6,6, opens new markets. A thermally conductive resin can be used for heat-sink applications. This research focused on performing compounding runs followed by injection molding and thermal conductivity testing of carbon filled nylon 6,6 and polycarbonate based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch-based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 23 factorial design and a complete replicate in each polymer. The objective of this article was to determine the effects and interactions of each filler on the thermal conductivity properties of the conductive resins. From the through-plane thermal conductivity results, it was determined that for both nylon 6,6 and polycarbonate based resins, synthetic graphite particles caused the largest increase in composite thermal conductivity, followed by carbon fibers. The combination of synthetic graphite particles and carbon fiber had the third most important effect on composite thermal conductivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 112–122, 2003

Flame retardant aromatic polycarbonate resin composition

Abstract: A flame retardant aromatic polycarbonate resin composition comprising 100 parts by weight of an aromatic polycarbonate (A), 0.01 to 0.5 part by weight of branched metal oxide particles (branched metal oxide aggregates and/or branched metal oxide agglomerates) (B), 0.0001 to 0.2 part by weight of an alkali metal salt (C) of an organic sulfonic acid, and 0.01 to 0.5 part by weight of a fluoropolymer (D), the branched metal oxide particles (B) being dispersed in a mixture of components (A), (C) and (D), wherein at least 70% of the branched metal oxide particles (B) have a diameter within the range of from 10 to 200 nm.

Air-channel fabrication for microelectromechanical systems via sacrificial photosensitive polycarbonates

Abstract: This research involves the fabrication of encapsulated air-channels via acid-catalyzed degradation of photosensitive polycarbonates (PCs). There is a need for lower-temperature, degradable polymeric materials to fabricate buried air-channels for microelectromechanical systems (MEMS), microfluidic devices, and micro-reactors. Some polycarbonates undergo thermolytic degradation in the temperature range of 200 to 350/spl deg/C. These polycarbonates are also known to undergo acid-catalyzed decomposition in the presence of catalytic amounts of acid. A small percentage of an acid in the polycarbonate formulation can greatly reduce the onset of decomposition temperature to the 100 to 180/spl deg/C temperature range. The photoacid and thermal acid induced degradation behavior of PCs and its use as a sacrificial material for the formation of air-gaps have been studied in this work. The decomposition of several polycarbonates with the aid of in situ generated photo-acid has been demonstrated and applied to the fabrication of micro air-channels. Based on FT-IR, mass spectrometry, and thermogravimetric analysis (TGA), a degradation mechanism was proposed.

Preparation of high molecular aliphatic polycarbonates

Abstract: Polycarbonate having aliphatic polycarbonate block(s) is produced by producing low molecular weight aliphatic polycarbonate, and condensing the low molecular weight aliphatic polycarbonate with diaryl carbonate in melt transesterification to form high molecular weight aliphatic polycarbonate. An Independent claim is also included for an aliphatic polycarbonate having weight-average molecular weight of at least 30000 g/moles comprising structural units conforming to formula (VII) or radical conforming to (II). T, Al = optionally branched and optionally saturated alkyl or cycloalkyl radical with 2-40C; and -O-Ar-O- = aromatic radical with 12-24C.

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

Abstract: 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.

Articles of manufacture incorporating polyester/polycarbonate blends

Abstract: This invention relates to thermoplastic article having one or more decorative materials on the surface thereof which is obtained by applying heat and pressure to a laminate wherein said thermoplastic article comprises (1) one or more decorative materials; and (2) an upper or lower sheet material; wherein the upper or lower sheet material is formed from a polyester/aromatic polycarbonate blend .

Fabrication of a paraffin actuator using hot embossing of polycarbonate

Abstract: In this paper a fabrication process for integrating paraffin-actuated structures in polycarbonate is outlined. A paraffin-actuated membrane with a diameter of 2.5 mm, where the volume expansion of 10–15% associated with the solid-to-liquid phase transition of paraffin is utilized, has been fabricated and evaluated. Microstructures fabricated in silicon have via an electroplated nickel mould been replicated in polycarbonate by hot embossing and the resulting structures have been sealed by thermal bonding. The bonding strength was measured by a pressurizing test, and the polycarbonate surfaces were characterized with electron spectroscopy for chemical analysis (ESCA). It was found that the bond strength increased when an oxygen plasma treatment was used prior to bonding. ESCA measurements showed a corresponding increase in oxygen content on the plasma treated surfaces. This procedure also improved the wetting properties. The contact angle between paraffin and polycarbonate decreased from 10° after embossing to about 5° after plasma treatment. The fabricated actuator had a total thickness of 1 mm and the membrane deflected about 140 μm when heating the actuator above the melting point of paraffin. Paraffin wax actuators are possible to integrate in plastic structures making them promising candidates in applications such as disposable microfluidic systems where inexpensive and robust valves and pumps are needed.

Physical Aging of Polycarbonate: Elastic Modulus, Hardness, Creep, Endothermic Peak, Molecular Weight Distribution, and Infrared Data

Abstract: For the first time, load and depth sensing indentation (DSI) was used in order to monitor physical aging of bisphenol A polycarbonate for 30 months at room temperature and for 1 month at an elevated temperature. The DSI experiments were combined with differential scanning calorimetry, gel permeation chromatography, and infrared spectroscopy. The endothermic peak of polycarbonate shifted toward higher temperatures upon aging at an elevated temperature and did not change its location upon aging at room temperature. The elastic modulus and hardness of polycarbonate increased in a stepwise fashion during aging at room temperature. The molecular weight distribution broadened slightly, and the trans−trans conformational population increased during annealing. No simple correlation between changes in the mechanical properties and the shift of the endothermic peak during annealing was found. These changes seem to be caused by phenomena of different nature; namely, the changes in the mechanical properties appeared ...

Polymer powders for SIB processes

Abstract: A process of selective inhibition of bonding (SIB) to produce three-dimensional objects is used to obtain high-quality moldings. High-quality moldings can be produced by using pulverulent materials which have a median particle size of from 10 to 200 μm in which at least one polymer or copolymer selected from polyester, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl methacrylate (PMMA), PMMI, ionomer, polyamides, copolyester, copolyamides, terpolymers, or ABS, or a mixture of these, is present.

Long-Range, Entangled Carbon Nanotube Networks in Polycarbonate†

Abstract: A method is presented for dispersing ropes or bundles of single-walled carbon nanotubes (RCNTs) in a polycarbonate (PC) matrix. Films of PC/RCNT composites are produced, with thicknesses ranging from 10 to 60 μm, and containing small concentrations (0.06–0.25 wt.-%) of RCNT. Our process is based on a unique method of hot casting, annealing, and drying from dichlorobenzene solution. A wet annealing prior to complete drying yields a uniform and transparent film. Despite the low RCNT loading, scanning electron microscopy (SEM) analysis of the films after fracture reveals that the RCNTs form an entangled network throughout the film, which is a key requirement for enhanced properties. An increase of up to 30 % in the Young's modulus, as compared to PC, results with this method of composite fabrication.

Feasibility of conducting semi‐interpenetrating networks based on a poly(ethylene oxide) network and poly(3,4‐ethylenedioxythiophene) in actuator design

Abstract: A new type of synthetic pathway—the use of interpenetrating polymer networks (IPNs)—is proposed to design conducting polymer-based actuators Two types of materials with interesting conducting properties were prepared: (1) a semi-IPN between poly(3,4-ethylenedioxythiophene) (PEDOT) and branched poly(ethylene oxide) (PEO) network; (2) a tricomponent IPN between PEDOT and a PEO/polycarbonate (PC)–based network as the ionic conducting partner In the first case, the influence of the amount of branching in the PEO network on the EDOT uptake and electrochemical properties was studied A maximum conductivity (15 S cm−1) was obtained for 60 wt % branched PEO in the material Moreover, the dispersion profile of PEDOT in the material was shown by elemental analysis and energy dispersion spectroscopy to follow a gradient through the thickness of the film leading to a built-in three-layered device With respect to PEO/PC materials, the best results were obtained for about 80 wt % PEO in the matrix where the material remains sufficiently elastomeric In this case, the conductivity reaches about 1 S cm−1 for a 10 to 30 wt % polycarbonate content These materials are capable of reversible 45° angular deflections under a 05V potential difference © 2003 Wiley Periodicals, Inc J Appl Polym Sci 90: 3569–3577, 2003

Flame retardant polycarbonate resin composition

Abstract: PROBLEM TO BE SOLVED: To obtain a polycarbonate resin composition having a high level flame retardant property without exhibiting environmental problems. SOLUTION: This resin composition is obtained by blending 100 pts.wt. polycarbonate resin, 0.05-10 pts.wt. silicone resin, 0.01-2 pts.wt. perfluoroalkane sulfonic acid metal salt, and/or 0.02-3 pts.wt. aromatic sulfur compound metal salt and also 0.7-20 pts.wt. carbon black. COPYRIGHT: (C)2004,JPO

Nanotechnology of transparent metals for radio frequency electromagnetic shielding

Abstract: The aim of this paper is to present an innovative one-dimensional photonic bandgap structure on plastic substrate, for electromagnetic field shielding applications in the radio frequency range. A complete study is performed, from material characterization and design, to fabrication and experimental test of a prototype sample consisting of seven alternating zinc oxide and silver (Ag) layers, on Lexan polycarbonate. The transparent metal is designed to obtain high shielding effectiveness (SE), not just as a theoretical prediction, but as experimentally measured according to the standard ASTM-D 4935/89. Actually, the shielding performance of multilayered coatings having similar values of sheet resistance but different design are strongly affected by the bonding conditions. The following properties of the structure, which contains only 66 nm of Ag, are highlighted: 1) it remains transparent in the visible range; 2) it retains the conductivity of bulk metal; 3) it has SE in the 30-kHz to 1-GHz range over 40 dB; 4) the overall thickness of the multilayer shielding coating is 312 nm; and 5) it has been realized on both glass or plastic substrate.

Wet-chemical processing of transparent and antiglare conducting ITO coating on plastic substrates

Abstract: The paper reviews a low temperature sol-gel processing of transparent and antiglare conducting Sn doped indium oxide (ITO) coatings. The approach uses already crystalline nanoparticles which can be fully redispersed in an ethanolic sol containing a polymerisable organic binder. Thick single layers up to 600 nm can be deposited by spin and dip coating techniques followed either by a low temperature ( 8 lines/nm) were obtained by a conventional spraying technique. These techniques have been successfully applied to several plastic substrates such as polycarbonate (PC), polymethylmetacrylate (PMMA), polyimide, polyethylene (PE) as well as glasses.

Polyester/polycarbonate blends with reduced yellowness

Abstract: Thermoplastic compositions of polyester/polycarbonate blends have reduced yellowness and improved thermal and melt stability when the polyester is produced with a reduced level of a titanium-containing catalyst in an amount of from about 1 to about 30 ppm elemental titanium, with ppm based on the total weight of the polyester.

Method for making an aromatic polycarbonate

Abstract: This invention relates to an extrusion method preparing polycarbonates from a solution of an oligomeric polycarbonate. A mixture of bis(methyl salicyl)carbonate (BMSC), BPA and a transesterification catalyst are first equilibrated at moderate temperatures to provide a solution of polycarbonate oligomer in methyl salicylate. The solution is then fed to a devolatilizing extruder, where the polymerization reaction is completed and the methyl salicylate solvent is removed. The solution comprising the oligomeric polycarbonate can also be pre-heated under pressure to a temperature above the boiling point of methyl salicylate and subsequently fed to a devolatilizing extruder equipped for rapid flashing off the solvent. The method provides polycarbonate with greater efficiency than the corresponding process in which unreacted monomers are fed to the extruder. Additionally, the method of the invention does not require the isolation of a precursor polycarbonate comprising ester-substituted phenoxy terminal groups.

Effects of Cooling Rate and Physical Aging on the Gas Transport Properties in Polycarbonate

Abstract: The gas transport properties of bisphenol A polycarbonate films were examined as a function of the cooling rate during film processing and subsequent physical aging. Interpretation of the permeation properties using results from dynamic mechanical analysis and density measurements indicated that the diffusion coefficient of small gas molecules in glassy polycarbonate is influenced more by the local chain dynamics rather than by the overall free volume content. A one-dimensional lattice model was developed to help probe the effects of the distribution of energy barriers associated with polymer motion on the transport properties. Fast cooling rates generated highly restricted conformations, which hindered local motions leading to increases in the measured activation energy of diffusion. These results correlated well with a lattice model having a broad distribution of energy barriers. Annealing reduced the measured diffusion coefficients, which was shown to be consistent with narrowing of the energy barrier ...

Mechanically Linked Polycarbonate

Abstract: The synthesis, by solid-state copolymerization, and characterization of the first polycatenanes based on a commercial polymer are reported. Various amounts of a benzylic amide [2]catenane, the corresponding macrocycle, and a rigid bisphenol fluorene derivative have been quantitatively and homogeneously incorporated into bisphenol A polycarbonate. The resulting copolymers were characterized by size exclusion chromatography coupled with viscosimetry, (1)H NMR, differential scanning calorimetry, and dynamic mechanical analysis. The unexpectedly small influence of [2]catenane incorporation on the glass transition temperature of the copolymers points to remarkable internal mobility of the catenane comonomer rings. A new relaxation linked to the flexible catenane units is also observed. The studies represent a detailed structural characterization of a polymer containing small amounts of mechanical linkages in its backbone and demonstrate that significant effects can be induced by doping conventional polymers with small percentages (2-6% of repeat units) of flexible catenanes.