Showing papers on "Polycarbonate published in 1997"

Template synthesis of nanowires in porous polycarbonate membranes: electrochemistry and morphology

Abstract: The potentiostatic electrochemical template synthesis of nanowires (Ni, Co, Cu, Au, and polyporrole) in polycarbonate track-etched membranes with nominal pore diameters dN between 10 and 200 nm is ...

Determination of Bisphenol-A in Reusable Polycarbonate Food-Contact Plastics and Migration to Food-Simulating Liquids

Abstract: Bisphenol-A (BPA) is a principal reactant in the preparation of polycarbonate (PC) plastics and has been shown in in vitro cell proliferation studies to exhibit estrogen-like characteristics. Reusa...

Flame-retardant thermoplastic resin composition

Abstract: A flame retarded thermoplastic resin composition comprising (R) a thermoplastic resin comprising (A) a polycarbonate resin and (B) an aromatic polyester resin in an (A)/(B) ratio of 99/1 to 50/50 by weight, and per 100 parts by weight of the thermoplastic resin (R), (C) 0.5 to 100 parts by weight of a silicate compound and (D) 0.5 to 30 parts by weight of an organic phosphorus based flame retarder. The composition can exhibit excellent flame resistance and anti-drip property without containing a halogen atom and, moreover, has excellent properties such as heat resistance, mechanical strength, solvent resistance, surface property of moldings, and dimensional stability.

Alternating Copolymerization of Carbon Dioxide and Propylene Oxide with a Rare-Earth-Metal Coordination Catalyst

Abstract: The copolymerization of carbon dioxide and propylene oxide using rare-earth-metal catalyst systems was investigated in this study. It was found that the ternary rare-earth-metal coordination catalyst consisting of Y(CF3CO2)3 (I), diethylzinc (II), and glycerine (III) was the most effective catalyst system to generate an alternating polycarbonate. The effects of the molar ratio of catalyst components, the solvent, and the operating temperature and pressure on the yield and the molecular weight of polycarbonate were systematically studied. At an appropriate combination of all variables, the yield could be as high as 4200 (g/(mol of Y))/h and the molecular weight as high as 1.0 × 105 in a 12 h reaction period. The carbonate content in the resulting polycarbonate was found to be 95.6%.

Synthesis and Characterization of Hyperbranched Polycarbonates

Abstract: Hyperbranched aromatic polycarbonates were prepared by the polymerization of an A2B monomer derived from 1,1,1-tris(4‘-hydroxyphenyl)ethane. Protection of one of the three phenols of the triphenol by a tert-butyldimethylsilyl group was followed by conversion of the remaining two phenolic groups to carbonylimidazolide functionalities to give the A2B monomer. Polymerization was accomplished via the anhydrous removal of the silicon protecting group and subsequent reaction of the phenoxide with a carbonylimidazolide moiety to yield the hyperbranched aryl polycarbonate bearing carbonylimidazolide chain ends. Subsequent cleavage of these end groups by reaction with methanol upon precipitation, yielded the phenol-terminated hyperbranched polycarbonate. Silylation of the phenol-terminated material with tert-butyldimethylsilyl chloride, followed by degradation of the carbonate linkages by reaction with lithium aluminum hydride and analysis of the products by HPLC allowed for the degree of branching to be determine...

Clear polycarbonate and polyester blends

Abstract: A blend of polycarbonates of dihydroxydiphenyl cycloalkanes and optionally 4,4'-isopropylidenediphenol with polyesters from terephthalic acid, isophthalic acid, 1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, having the advantage of being colorless and providing an unexpected amount of impact strength, hardness and heat resistance. The polymer blends are especially suitable for the manufacture of clear molded articles, fibers, sheeting, and film.

Comparison of the effect of ethylene oxide and γ-irradiation on selected tyrosine-derived polycarbonates and poly(L-lactic acid)

Abstract: Tyrosine-derived polycarbonates are a new class of degradable polymers that have possible biomedical applications. In this study, the effect of the two most common sterilization techniques, ethylene oxide and γ-irradiation (0.3, 1.1, 3.9, 6.4, 10.6 Mrad), was evaluated for a family of four structurally related tyrosine-derived polycarbonates and for poly(L-lactic acid) (PLLA). The four polycarbonates were poly(DTE carbonate), poly(DTB carbonate), poly(DTH carbonate), and poly(DTO carbonate) and differed only in the length of the pendent chain. Ethylene oxide exposure had little effect on molecular weight, surface composition, mechanical properties, or degradation rate of all test polymers except for poly(DTO carbonate). Poly(DTO carbonate) was unique since following ethylene oxide exposure it degraded faster than did the nonsterilized control. γ-Irradiated tyrosine-derived polycarbonates retained over 81% of their initial molecular weight when exposed to a clinically relevant dose of 3.9 Mrad and retained still 58% of the initial molecular weight when exposed to the highest test dose of 10.6 Mrad. No changes in surface composition and only slight changes in yield strength and the Young's modulus were detected for any of the tyrosine-derived polycarbonates following γ-irradiation. In vitro, irradiated films of poly(DTE carbonate), poly(DTB carbonate), and poly(DTH carbonate) degraded at approximately the same rate as did the nonsterilized films regardless of irradiation dose. Only poly(DTO carbonate), irradiated at high doses, degraded faster than did the control. Medical-grade PLLA was tested under identical conditions. Ethylene oxide exposure of PLLA did not affect the molecular weight, surface composition, mechanical properties, or in vitro degradation rate. However, upon irradiation at 10.6 Mrad, PLLA retained only 29% of its initial molecular weight; a dose of 3.9 Mrad resulted in retention of 49% of the initial molecular weight. In correspondence with earlier publications, irradiation of PLLA induced significant losses in the Young's modulus, % strain at break, and changes in the postirradiation rate of degradation in some specimens. Compared to PLLA, tyrosine-derived polycarbonates are significantly more stable to γ-irradiation and can be sterilized by conventional γ-sterilization techniques. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1499–1510, 1997

Hydrolytically-and proteolytically-stable polycarbonate polyurethane silicone copolymers

Abstract: A biocompatible, biodurable polycarbonate polyurethane with internal polysiloxane segments and devices made therefrom.

Direct Fullerenation of Polycarbonate via Simple Polymer Reactions

Abstract: Direct fullerenation of polycarbonate (PC), a commercially important optical polymer, is achieved by simply irradiating a solution of PC and C60 at room temperature using a conventional UV lamp or

Impact modified carbonnate polymer composition having improved resistance to degradation and improved thermal stability

Abstract: An aromatic carbonate polymer composition having improved thermal stability consisting of an aromatic carbonate polymer such as a polycarbonate or polycarbonate/polyester blend and an impact modifier which is free of alkali materials which catalytically degrade a polycarbonate. Also an impact modifier which is preferably of a shell-core structure prepared by the emulsion polymerization process and has a pH of about 3 to about 8. A preferred emulsifier is an alkyl sulfonate having an alkyl group of C6-C18 carbons.

Glass fiber-reinforced polycarbonate resin composition

Abstract: The present invention relates to a glass fiber-reinforced polycarbonate resin composition comprising: (A) 70 to 92% by weight of an aromatic polycarbonate resin; (B) 1 to 20% by weight of an aromatic polycarbonate oligomer; (C) 3 to 20% by weight of a glass fiber comprising a short glass fiber having a fiber length of not more than 140 μm and a long glass fiber having a fiber length of more than 140 μm; and (D) 05 to 15% by weight of a composite rubber-based graft copolymer, halogen content in said resin composition being not more than 05% by weight based on total weight of said resin composition

Structural Heterogeneity in Poly(methyl methacrylate) Glasses of Different Tacticity Studied by Thermally Stimulated Current Thermal Sampling Techniques

Abstract: The thermally stimulated current thermal sampling (TSC-TS) technique was used to study the cooperative glass transition like relaxations in different tacticity poly(methyl methacrylates) (PMMAs) including iso- and syndiotactic forms We use the high sensitivity of the TSC-TS method to study these weak and sometimes overlapping relaxations at a frequency of about 10 -3 Hz where one can resolve cooperative relaxations well below the main glass transition (Tg), even if the species are a minor fraction of the overall relaxing species The magnitudes of the values of E a are compared with a theoretical prediction as a function of temperature, showing that the low-temperature tail of the glass transition in conventional atactic (eg, 45% syndiotriads) extends down to 15 °C, while in our highest syndiocontent PMMA (80% syndiotriads), the glass-transition-like relaxations only extend down to about 80 °C Results taken from the literature also substantiate the results obtained here for atactic PMMA The results are contrasted to those for bisphenol-A polycarbonate and other polymers and suggest that compositional heterogeneity, more specifically the presence of low T g pockets of predominantly isotactic sequences, contributes to the broad glass transition extending almost 90 °C below the main glass transition in atactic PMMA

The role of transesterification on the miscibility in blends of polycarbonate and liquid crystalline copolyester

Abstract: Transesterification mechanisms and rate in blends of polycarbonate (PC) and random liquid crystalline polyester copoly(oxybenzoate-p-terephthalate) at molar ratio 40/60 (P46) were studied through a five-component diad analysis and with 13C and 1H-13C nuclear magnetic resonance spectroscopy. It was found that the ester-ester interchange in the two polymers took place within 15 min when the blend was annealed at 260 °C in vacuum. In the annealed blend, the Bisphenol A unit in polycarbonate reacted first with the terephthalate unit and then with the oxybenzoate unit in copoly(oxybenzoate-p- terephthalate). As the transesterification in the blend continued for about 1 h, the forming of diad Bisphenol A-oxybenzoate exceeded that of diad Bisphenol A-terephthalate. This large loss (57%) of the diad oxybenzoate-oxybenzoate caused the disappearance of the liquid crystalline phase in the blend. In sharp contrast to the originally immiscible blend of PC and P46 (two distinctive glass transition temperatures), the large loss of the liquid crystalline diad resulted in complete miscibility in the annealed blend, as evidenced by the appearance of a single glass transition temperature in the differential scanning calorimetry measurement.

Dielectric relaxation spectroscopy of amorphous and liquid-crystalline side-chain polycarbonates

Abstract: The molecular dynamics of amorphous and liquid-crystalline (LC) side-chain polycarbonates was studied by dielectric spectroscopy at frequencies from 10−2 to 106 Hz and at temperatures from −160 to 180°C. ‘Model’ compounds containing no mesogenic side-groups showed two relaxations, which originate from the carbonate group (α, βm-relaxation). By contrast, in LC-polycarbonates bearing a mesogenic nitrostilbene side group around and above the glass transition temperature Tg up to three relaxation modes were distinguished (α-, λ1-, λ2-process); below Tg four secondary relaxations (γ-, βm-, βs-, βsc-relaxation) were observed. The γ-relaxation was found only in compounds possessing an aliphatic spacer linked to the backbone by an ether bond. Apart from βm-, two additional β-processes were identified as relaxations associated with the mesogenic unit in the glassy (βs) or in the crystalline state (βsc).

Volume Change of Glassy Polymers by Sorption of Small Molecules and Its Relation to the Intermolecular Space

Abstract: The volume changes caused by the sorption of H2O, Ar, N2, CO2, CH4 and Acetone in Bisphenol-A polycarbonate and of CO2 in different substituted polycarbonates and in Kapton were measured in a dilat...

Analysis of the density and the enthalpy of poly(epsilon-caprolactone)-polycarbonate blends: Amorphous phase compatibility and the effect of secondary crystallization

Abstract: The dependency of the density of poly(epsilon-caprolactone)-polycarbonate (PCL-PC) blends on composition has been studied. PCL/PC blends are typical of miscible blends containing crystallizable components, and miscibility is therefore considered with respect to the amorphous phase. In literature, a single glass transition temperature is reported for the PCL-PC system; however, the exact dependency on amorphous phase composition is not clear. For quenched amorphous blends, we found the Fox equation to be appropriate in order to describe the glass transition temperature as a function of composition. For amorphous samples containing low amounts of PCL (less than or equal to 40 wt %), an increase in the density of the blend over that of a linear average of the densities of amorphous PC and PCL was observed experimentally. This is indicative of significant interactions in the blend. For samples containing greater than or equal to 50 wt % PCL, crystallization of PCL has to be accounted for in the analysis of the density. It is shown that the experimental density data can only be described satisfactorily by assuming that secondary crystallization of PCL does not lead to an increase of the overall blend density. This is attributed to the rigid and volume filling primary crystalline structure at room temperature, i.e., below the melting point of PCL. Excess density is present in the amorphous phase of the PCL/PC blend over the whole range of composition; therefore, specific interactions exist in the amorphous phase of the blend over the whole range of composition. (C) 1997 John Wiley & Sons, Inc.

The Mechanism for 3-Aminopropyltriethoxysilane to Strengthen the Interface of Polycarbonate Substrates with Hybrid Organic–Inorganic Sol-Gel Coatings

Abstract: An aminolysis mechanism is proposed to explain the enhanced adhesion between the interface of a bisphenol-A polycarbonate substrate with an alkoxysilane containing sol-gel coating when 3-aminopropyltriethoxysilane (3-APS) is used as a primer Both a model solution study and surface analyses of polycarbonate substrates exposed to 3-APS indicate that the latter reacts with the carbonate groups in the polycarbonate chain by forming urethane linkages With 3-APS bonded to the substrate, a sol-gel coating can be chemically bonded to the substrate through hydrolysis of alkoxysilane groups and subsequent silanol condensation Consequently, enhanced adhesion between the sol-gel coating and the substrate is achieved

Method for preparing polycarbonate by solid state polymerization

Abstract: Solid state polycarbonate formation comprises an initial step of converting a precursor polycarbonate to an enhanced crystallinity precursor polycarbonate and a second step of polymerizing said enhanced crystallinity precursor polycarbonate in the solid state. Several options are employed. These include modifying the precursor polycarbonate by contact with a dihydroxy compound or diaryl carbonate, conversion of the precursor polycarbonate to the enhanced crystallinity polymer by contact with at least one compound selected from the group consisting of alkali metal hydroxides, tetraalkylammonium hydroxides, tetraalkylammonium carboxylates, tetraalkylphosphonium hydroxides and tetraalkylphosphonium carboxylates, and conducting the solid state polymerization in the presence of a catalytic amount of at least one tetralkylammonium or tetraalkylphosphonium carboxylate. The preferred tetralkylammonium compounds are tetramethylammonium maleate and tetramethylammonium hydroxide. Polymerization may be conducted in the presence of a solvent resistance-imparting monomer such as hydroquinone or resorcinol or a branching agent such as 1,1,1-tris(4-hydroxyphenyl)ethane.

Anti-static resin composition containing fluorinated phosphonium sulfonates

Abstract: An anti-static thermoplastic resin composition of 90-99.95 weight % of a thermoplastic resin and correspondingly 10 to 0.05 weight % of a halogenated carbon sulfonic acid salt of a polysubstituted phosphonium compound such as a fluorinated phosphonium sulfonate and wherein the thermoplastic resin is either an aromatic polycarbonate, polyetherimide, polyester, polyphenylene ether, polyphenylene ether/styrene polymer blend, polyamide, polyketone, acrylonitrile-butadiene-styrene, blends thereof and blends thereof with other materials. Preferably the thermoplastic resin is a transparent aromatic polycarbonate.

Morphological, thermal, and mechanical properties of polypropylene/polycarbonate blend

Abstract: This work deals with the effect of compatibilizer on the morphological, thermal, rheological, and mechanical properties of polypropylene/polycarbonate (PP/ PC) blends. The blends, containing between 0 to 30 vol % of polycarbonate and a compatibilizer, were prepared by means of a twin-screw extruder. The compatibilizer was produced by grafting glycidyl methacrylate (GMA) onto polypropylene in the molten state. Blend morphologies were controlled by adding PP-g-GMA as compatibilizer during melt processing, thus changing dispersion and interfacial adhesion of the polycarbonate phase. With PP-g-GMA, volume fractions increased from 2.5 to 20, and much finer dispersions of discrete polycarbonate phase with average domain sizes decreased from 35 to 3 mu m were obtained. The WAXD spectra showed that the crystal structure of neat PP was different from that in blends. The DSC results suggested that the degree of crystallization of PP in blends decreased as PC content and compatibilizer increased. The mechanical properties significantly changed after addition of PP-g-GMA. (C) 1997 John Wiley & Sons, Inc.

Diffusion of gold and silver in Bisphenol A polycarbonate

Abstract: Diffusion of evaporated gold and silver into Bisphenol A polycarbonate has been studied using the radiotracer technique in combination with ion beam sputtering for serial sectioning. Diffusion coefficients between 4 × 10-14 and 1 × 10-16 cm2 s-1 were measured in the temperature range between 210 and 130 °C. The metal concentration in the polymer turned out to depend strongly on the evaporation rate. An Arrhenius-like temperature dependence with activation energies of 1.02 eV for silver and 1.13 eV for gold was found. The low diffusivities, which are not affected by the polymer dynamics, are interpreted within molecular theories for diffusion of gases in polymers with an additional attractive interaction between metal atoms and polymer chains.

Formation of polycarbonate film with apertures determined by etching charged-particle tracks

Abstract: A technique for creating openings in a polycarbonate film entails providing a liquid chemical formulation that contains polycarbonate material, a liquid that dissolves the polycarbonate, and possibly one or more other constituents. The liquid is typically capable of dissolving the polycarbonate to a concentration of at least 1% at 20° C. and 1 atmosphere. Examples of the liquid include pyridine, a ring-substituted pyridine derivative, pyrrole, a ring-substituted pyrrole derivative, pyrrolidine, a pyrrolidine derivative, chlorobenzene, and cyclohexanone. A liquid film (36A) of the chemical formulation is formed over a substructure (30) and processed to remove the liquid, thereby converting the liquid film into a solid polycarbonate track layer (38). Charged particles (70) are passed through the track layer to form charged-particle tracks (72) at least partway through the layer. Apertures (74) are created through the track layer by a process that entails etching along the tracks. The aperture-containing polycarbonate track layer is typically employed in fabricating a gated electron-emitting device.