Showing papers on "Polycarbonate published in 2006"

Nanoscale Mechanical Characterization of Polymers by AFM Nanoindentations: Critical Approach to the Elastic Characterization

Abstract: AFM nanoindentations show a dependence of penetration, i.e., the relative motion between the sample and the tip (indenter), on material elastic properties when using the same load. This relationship becomes visible by using of samples being homogeneous down to the scale of nanoindentation. They were prepared from materials covering a broad range of mechanical behavior: from rubbery networks to glassy and semicrystalline polymers. The elastic modulus can be obtained applying Sneddon's elastic contact mechanics approach. To do this, some calibrations and instrumental features have to be measured accurately. All the polymers tested show that the contact between the tip and the sample is dominated by elastic behavior with negligible plastic deformation. In contrast to a standard metallic material like lead, the penetration dependence on load follows an exponent of 1.5, consistent with elastic contact mechanics. This can be justified on the basis of the large elastic range polymers exhibit, on the constraints...

Core‐Sheath Structure in Electrospun Nanofibers from Polymer Blends

Abstract: Electrospinning of polymer blends offers the potential to prepare functional nanofibers for use in a variety of applications. This work focused on control of the internal morphology of nanofibers prepared by electrospinning polymer blends to obtain core-sheath structures. Polybutadiene/ polystyrene, poly(methylmethacrylate)/polystyrene, polybutadiene/ poly(methylmethacrylate), polybutadiene/polycarbonate, polyaniline/polycarbonate, and poly(methylmethacrylate)/ polycarbonate blends were electrospun from polymer solutions. It was found that the formation of core-sheath structures depends on both thermodynamic and kinetic factors. Incompatibility and large solubility parameter difference of the two polymers is helpful for good phase separation, but not sufficient for the formation of core-sheath structures. Kinetic factors, however, play a much more important role in the development of the nanofiber morphology. During the electrospinning process, the rapid solvent evaporation requires systems with high molecular mobility for the formation of core-sheath structures. It was found that polymer blends with lower molecular weight tend to form core-sheath structures rather than co-continuous structures, as a result of their higher molecular mobility. Rheological factors also affect the internal phase morphology of nanofibers. It was observed the composition with higher viscosity was always located at the center and the composition with lower viscosity located outside.

Polymer/silica nanocomposites prepared via extrusion

Abstract: Three polymer/silica nanocomposites were prepared by a single-screw extrusion approach: poly(methyl methacrylate), polystyrene and polycarbonate/silica nanocomposites. The resulting nanocomposites were subjected to comprehensive studies of mechanical, thermal and flammability properties. All materials showed improved mechanical performance and thermal stabilities, although they are not strictly flame retardant when subjected to fire tests like Oxygen Index or horizontal Bunsen burner tests. However, the nanocomposites showed reduction in peak heat release rates and total heat release when evaluated by cone calorimetry. Moreover, the polycarbonate showed improvement in flammability according to vertical burning tests. All polycarbonate materials subjected to vertical burning testing are V2 rated, but after flame times with 1% silica were significantly reduced. A flame retardant mechanism is proposed in order to understand the relationship between interfacial interaction and flammability of polymer/silica nanocomposites. Copyright © 2006 John Wiley & Sons, Ltd.

Polycarbonate molding compositions

Abstract: An impact modified thermoplastic molding composition comprising aromatic polycarbonate and/or polyester carbonate and a rubber-modified graft polymer prepared by the bulk, solution or bulk-suspension polymerization process is disclosed. The composition that is characterized by its low content of lithium ions features improved hydrolytic resistance.

Morphology and properties of organoclay modified polycarbonate/poly(methyl methacrylate) blend

Abstract: Virgin and organoclay modified polycarbonate (PC)/ poly(methyl methacrylate) (PMMA) (30/70 w/w) blends were prepared by melt-mixing of PC, PMMA, and organically modified montmorillonite (OMMT). The morphology of OMMT modified PC/PMMA blend with two different weight percents of OMMT was studied using scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The size of the phase-separated domains decreased dramatically with increasing the content of OMMT. XRD patterns and TEM observations revealed that silicate layers were intercalated and nicely dispersed in the blend matrix. Differential scanning calorimetry analyses showed efficient mixing of two immiscible polymers in the presence of OMMT. The blend nanocomposites showed greatly improved mechanical properties when compared with the same blend sample without OMMT. Finally, the opaque immiscible PC/PMMA blend became translucent after modification with OMMT addition.

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

Abstract: 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 microm. 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.

Apparatus and method for making form-fitted molded protective cases for products

Abstract: A method and apparatus for making inexpensive, form-fitted, protective cases of thermal plastic or polycarbonate material that can be easily printed with decorative imagery and/or electronic circuitry for a variety of products, such as portable music players or radios, cell phones, lap-top computers, and the like. The method involves creating a tool having substantially the same surface dimensions of a product. An element is then molded from bulk film of thermoplastic material using the tool. Once the element is molded, it is trimmed from the bulk film. The resulting apparatus is a protective case intended to form-fit over the surface features and dimensions of the actual product used to define the tool.

Flame Retardants in Commercial Use or in Advanced Development in Polycarbonates and Polycarbonate Blends

Abstract: The polycarbonates, intrinsically rather flame retardant, have been further flame retarded with various bromoaromatic additives, such as tetrabromobisphenol-A polycarbonate. Other bromine additives used include brominated epoxy condensates and brominated polystyrenes. Sodium or potassium sulfonates, such as potassium perfluorobutylsulfonate, potassium diphenylsulfonesulfonate and sodium trichlorobenzenesulfonate are effective in very low loadings to meet less stringent flame retardancy. The first two allow for transparency. The blends of polycarbonate and poly(acrylonitride butadiene styrene) (ABS) are widely used for flame-retardant electrical and electronic enclosures. The major flame retardants used at present in the blends are tetraphenyl resorcinol diphosphate and tetraphenyl bisphenol-A diphosphonate (both with oligomers).

Surface modification and ultrasonication effect on the mechanical properties of carbon nanofiber/polycarbonate composites

Abstract: The effect of plasma surface modification and ultrasonication time on the mechanical properties of multi-wall carbon nanofiber polycarbonate composites were investigated. The study showed that plasma polymerization treatment of multi-wall carbon nanofibers enhanced the dispersion of the nanofibers in the polymer, and hence improved the mechanical properties of the nanocomposite. The study also showed that the mechanical properties of the nanocomposite depended on the ultrasonic dispersion time. Long term dispersion damaged the surfaces of both untreated and plasma polymerized carbon nanofibers. The interface behavior and strengthening mechanisms are discussed.

Thermoplastic polycarbonate compositions, method of manufacture, and method of use thereof

Abstract: A thermoplastic composition comprising in combination an aliphatic/aromatic co-polycarbonate component; an impact modifier; and a rigid copolymer, and optionally a polycarbonate component and/or a polycarbonate-polysiloxane copolymer is disclosed. The co-polycarbonate comprises repeating carbonate units and repeating aliphatic units. The compositions have a significantly improved balance of properties, including melt flow and impact.

Consecutive solvent evaporation and co-rolling techniques for polymer multilayer hollow fiber preform fabrication

Abstract: All-polymer multilayer hollow core photonic fiber preforms were fabricated using consecutive deposition from a solvent phase of two polymers with high and low refractive indices (RI). Processing techniques for two polymer pairs—polystyrene (PS)/poly(methyl methylacrylate) (PMMA) and polycarbonate (PC)/poly(vinylene difloride) (PVDF)—were established. The fabrication process involved consecutive film deposition by solvent evaporation of polymer solutions on the inside of a rotating PMMA or PC tube, used as a cladding material. By injecting right volumes of the polymer solutions into a spinning tube the thickness of each layer could be reliably controlled from 20 to 100 μm. Proper selection of solvents and processing conditions was crucial for ensuring high optical and mechanical quality of a resultant preform, as well as compatibility of different polymer films during co-deposition. Preforms of 10 layers for PMMA/PS material combination and 15 layers for PVDF/PC were demonstrated. Fabrication of preforms with higher number of layers is readily possible and is only a question of preform fabrication time. An alternative method of preform fabrication by co-rolling of polymer bilayers is also presented in this paper, drawing of PMMA/PS, PVDF/PC fibers with up to 32 layers is demonstrated.

Single-walled carbon nanotubes /polycarbonate composites : basic electrical and mechanical properties

Abstract: The focus of this paper is to investigate the electrical conductivity and the mechanical properties of single-walled carbon nanotubes/polycarbonate composites. Two different direct incorporating methods were applied. In the first method PC and SWCNTs were mixed with different ratios in a small scale conical twin screw extruder. Here, additional variations in the feeding of the filler material were tested in order to improve the state of dispersion of the melt mixing method. The second one is the coagulation method, here, the filler material was suspended and the polymer material was dissolved in liquid organic substances. The mechanical properties were examined by tension tests and by measuring the Vickers hardness. It should be stressed, that the nanofiller material was provided in large batches (m > 100 g) and extensively mechanically homogenized in order to eliminate quality fluctuations and density differences in the SWCNT occurrences. The filler material was synthesized in a Kratschmer reactor (carbon arc). After homogenization, the nanomaterial was characterized. Based on this the SWCNT content was estimated to be between 30 and 40%, which is usual for arc discharge material.

Effects of oxygen plasma treatment on the surface of bisphenol A polycarbonate: a study using SIMS, principal component analysis, ellipsometry, XPS and AFM nanoindentation

Abstract: The effects of oxygen plasma treatment and the subsequent air exposure on the surface composition and properties of bisphenol A polycarbonate (BPA-PC) were analysed by X-ray photoelectron spectroscopy (XPS), ellipsometry, static time-of-flight secondary ion mass spectrometry (ToF-SIMS) with principal component analysis (PCA) and nanoindentation using an atomic force microscope (AFM). PCA showed systematic changes in the film chemistry after short treatment times (0.1 s), with the main sites of attack being the carbonate and aromatic ring structure. On the basis of this multitechnique analysis, it was unambiguously determined that extended oxygen plasma treatment times resulted in the formation of low-molecular-weight material (LMWM) within the first 50 nm on the surface, and not in a cross-linked skin as has been proposed by other researchers. The study shows that controlled surface modification of BPA-PC polymers is possible, allowing surface oxygen incorporation without degradation of the polymer structure. This result is relevant for improved adhesion of coatings applied to BPA-PC polymers. Copyright © 2006 John Wiley & Sons, Ltd.

Effect of γ‐aminopropyl trimethoxy silane on the performance of jute–polycarbonate composites

Abstract: The composites of jute fabrics (hessian cloth) and polycarbonate were prepared by compression molding The jute surface was modified with γ-aminopropyl trimethoxy silane (Z-6011) to improve interfacial adhesion between jute and polycarbonate The treated and untreated jute surfaces as well as composites were investigated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Environmental scanning electron microscopy, Dynamic mechanical analysis, and mechanical testing XPS and FTIR assure that the silane plays important role to form interfacial bonding with the jute fibers and polycarbonate The surface topography of silanized and virgin fibers, and the interfacial adhesion properties of the composite were investigated by ESEM DMA analysis shows the improved storage and loss moduli of silanized jute composite as compared to the untreated one The modified jute composite also produces enhanced mechanical properties © 2006 Wiley Periodicals, Inc J Appl Polym Sci 100: 4142–4154, 2006

Thermoplastic polycarbonate compositions, articles made therefrom and method of manufacture

Abstract: A thermoplastic composition, contains a polycarbonate resin, a polycarbonate-polysiloxane copolymer, an aromatic vinyl copolymer, an impact modifier, and a mineral filler, wherein the composition has least about 40% ductility under multiaxial impact strength test conditions per ASTM D3763 at −30° C. Alternatively, a composition contains a polycarbonate resin, a polycarbonate-polysiloxane copolymer in an amount sufficient to provide at least about 2.5 wt. % siloxane by weight of the composition, an aromatic vinyl copolymer comprising SAN, an impact modifier comprising ABS, and a mineral filler. Such compositions may be made by combining, by weight of the composition, polycarbonate resin, a polycarbonate-polysiloxane copolymer, an aromatic vinyl copolymer, an impact modifier, and a mineral filler, wherein the composition has at least 40% ductility under multiaxial impact strength test conditions per ASTM D3763 at −30° C. An article may be made from such a composition, optionally by molding, shaping or forming the composition to form the article.

Polycarbonate and process for production thereof

Abstract: An isosorbide type polycarbonate prepared by using as the diol component isosorbide which is a plant-originating diol, which has a glass transition temperature higher than those of publicly known bisphenol-A type polycarbonates and isosorbide type polycarbonates and is excellent in heat resistance; and a process for the production thereof. The polycarbonate of the invention comprises structural units represented by formula (I) and has a glass transition temperature of 170oC or above as determined by differential calorimetry at a temperature rise rate of 10oC/min.

Polycarbonate with low photoelastic constant and film made thereof

Abstract: Disclosed is a polycarbonate having a structure containing a fluorene ring and a structure derived from an isosorbide. This polycarbonate has high heat resistance and a low photoelastic constant, and enables to obtain a film having good transparency. Consequently, this polycarbonate is extremely useful as a polymer for optical use such as a polymer for retardation films.

Thermoplastic polycarbonate compositions, method of manufacture, and method of use thereof

Abstract: A thermoplastic composition comprising in combination a polycarbonate component; a functionalized silane coupling agent; an impact modifier; and a filler is disclosed. The composition optionally comprises a polycarbonate-polysiloxane copolymer and/or a flame retardant. The compositions have a good balance of properties, and if desired, are also flame retardant.

Synthesis and Characterization of Novel Glycerol-Derived Polycarbonates with Pendant Hydroxyl Groups

Abstract: A novel type of glycerol-derived, water-soluble polycarbonate with pendant, primary hydroxyl groups was prepared from 2-(2-benzyloxyethoxy)trimethylene carbonate (BETC). Ring-opening polymerization of BETC and 2,2-dimethyltrimethylene carbonate (DTC) gave narrow distribution of homopolymers or random copolyiners with high molecular weights. The protecting benzyl groups were removed by catalyzed hydrogenation at atmosphere H 2 pressure to give hydroxyl polycarbonates without observable changes on the polymer backbone and molecular weight distribution. The hydrophilicity of the copolymers increases with tile increase in the hydrophilic glycerol-derived carbonate content.

Fabrication and characterization of polycarbonate/carbon nanotubes composites

Abstract: Polycarbonate composites containing carbon nanotubes can be prepared through a method combined solution mixing and precipitation together. The surface chemical state of the purified carbon nanotubes was studied through X-ray photoelectron spectroscopy, and the state of carbon nanotubes in the composites through transmission electron microscopy and scanning electron microscopy. Results showed that some polar functional groups such as C O, C O and O C O were present on the surface of the purified carbon nanotubes, and carbon nanotubes coated with polycarbonate layers were well dispersed through the polycarbonate matrix. Ultrasound is supposed to play an important role in the uniform dispersion of carbon nanotubes into the polycarbonate solution and the formation of the composites. The preparing method is regarded as an easy way of producing polymer based nanocomposites on a large scale.

Recycling poly(ethylene terephtalate) wastes: Properties of poly(ethylene terephtalate)/polycarbonate blends and the effect of a transesterification catalyst

Abstract: The article addresses the issue of recycling of poly(ethylene terephtalate) (PET) by melt blending with polycarbonate (PC). PET/PC blends containing various amounts of the immiscible polymers were prepared in a twin-screw extruder. Selected compositions were also prepared in the presence of an Sn-based catalyst to assess the influence of transesterification during melt mixing. The degree of miscibility in the blends was studied using differential scanning calorimetry, scanning electron microscopy, and mechanical testing. PET/PC blends exhibit enhanced tensile properties in comparison to neat components for compositions of PET higher than 50% and these properties are improved by the addition of a transesterification catalyst. The PET/PC blend containing 20 wt% of PC, prepared with stannous octoate, shows the smallest size of the dispersed phase because of transesterification reactions that generate copolymer molecules at the interface between the immiscible polymers. The melting temperature of PET is decreased with the increase of the PC content in blends extruded in the presence of the catalyst. Also, the temperatures of the cold crystallization of PET are higher than those of similar blends without added catalyst. Both features give rise to better molding properties because of a shortening of the cooling time in the range of 50–90 wt% of PET. POLYM. ENG. SCI. 46:1378–1386, 2006. © 2006 Society of Plastics Engineers

Local order in polycarbonate glasses by 13C{19F} rotational‐echo double‐resonance NMR

Abstract: Nearest-neighbor chain packing in a homogeneous blend of carbonate 13C-labeled bisphenol A polycarbonate and CF3-labeled bisphenol A polycarbonate has been characterized using a shifted-pulse version of magic-angle spinning 13C{19F} rotational-echo double-resonance (REDOR) NMR. Complementary NMR experiments have also been performed on a polycarbonate homopolymer containing the same 13C and 19F labels. In the blend, the 13C observed spin was at high concentration, and the 19F dephasing or probe spin was at low concentration. In this situation, an analysis in terms of a distribution of isolated heteronuclear pairs of spins is valid. A comparison of the results for the blend and homopolymer defines the NMR conditions under which higher concentrations of probe labels can be used and a simple analysis of the REDOR results is still valid. The nearest neighbors of a CF3 on one chain generally include a carbonate group on an adjacent chain. A direct interpretation of the REDOR total dephasing for the polycarbonate blend indicates that at least 75% of carbonate-carbon 13C···F3 nearest neighbors are separated by a narrow distribution of distances 4.7 ± 0.3 A. In addition, analysis of the variations in REDOR spinning-sideband dephasing shows that most of the 13C···F3 dipolar vectors have a preferred orientation relative to the polycarbonate mainchain axis. This combination of distance and orientational constraints is interpreted in terms of local order in the packing of the carbonate group of one polycarbonate chain relative to the isopropylidene moiety in a neighboring chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2760–2775, 2006

Light-diffusing polycarbonate resin composition and light diffuser plate comprising the resin composition

Abstract: The present invention provides a light diffusing polycarbonate resin composition including a polycarbonate resin containing a polycarbonate copolymer which comprises a repeating unit represented by the general formula (I) shown below and a repeating unit represented by the general formula (II) shown below, which has a content of the repeating units of the general formula (II) of 1 to 30% by mass and which has a viscosity value of 30 to 71, and (B) a light diffusing agent compounded therein in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the polycarbonate resin. The light diffusing polycarbonate resin composition and a light diffusing plate thereof show improved fluidity during molding and have excellent heat resistance, dimensional stability, luminance and color tone.

Light diffusive polycarbonate resin composition and light diffusive plate using said resin composition

Abstract: The present invention provides a light-diffusive polycarbonate-based resin composition which includes (A) 100 parts by mass of an aromatic polycarbonate resin, (B) 0.01 to 10 parts by mass of a light-diffusing agent, and (C) 0.1 to 20 parts by mass of a styrene-(meth)acrylic ester copolymer, and a light-diffusing plate formed from the composition. The light-diffusive polycarbonate-based resin composition can be injection-molded to form a light-diffusing plate having satisfactory precision in thickness for use in comparatively large liquid crystal displays having a size larger than 20 inches.

Aromatic polycarbonate resin composition for lightguide plate and lightguide plate

Abstract: There is provided an aromatic polycarbonate resin composition exhibiting excellent mechanical strength, transfer property, light transmittance, thermal stability and moldability which is capable of being molded into thin-wall products and large-size products, as well as a light guide plate produced from the resin composition. The present invention relates to an aromatic polycarbonate resin composition for light guide plates, comprising an aromatic polycarbonate resin having a viscosity-average molecular weight of 13,000 to 15,000, and a ratio of a weight-average molecular weight to a number-average molecular weight (Mw/Mn) of 1.5 to 2.7 in terms of polystyrene as measured by gel permeation chromatography; and a stabilizer and a releasing agent blended in the aromatic polycarbonate resin, as well as a light guide plate produced from the resin composition.