Showing papers on "Polycarbonate published in 2014"

Mechanical and electrical properties of multiwall carbon nanotube/polycarbonate composites for electrostatic discharge and electromagnetic interference shielding applications

Abstract: Home-made multiwall carbon nanotubes (MWCNTs) were used as a reinforcing conducting filler for a thermoplastic polymer, polycarbonate (PC) and the mechanical and electrical properties of the composites were investigated for electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding applications. A uniformly dispersed MWCNT/PC composite system was fabricated using solvent casting and a combination of solvent casting and compression molding techniques. The effect of MWCNTs on the failure mechanism of the polymer under tensile loading showed a ductile to brittle transition with increasing amount of carbon nanotubes. ESD studies showed that the composite films of 2 and 5 wt% functionalized-MWCNT/PC with respective charge decay times of 1 and 0.6 s show promise as electrostatic dissipative materials. EMI shielding effectiveness of a five-layered system (∼2 mm thickness) of as-synthesized-MWCNT/PC composite films at 20 wt% loading reached 43 dB in the X-band (8.2–12.4 GHz). The primary mechanism of shielding was absorption, suggesting possible use as an EMI absorbing material. By using low pressure (contact pressure) compression molding the EMI shielding properties of bulk composites (∼2 mm thickness) improved by about 14 dB at 10 wt% MWCNT loading.

Self-Cleaning Properties, Mechanical Stability, and Adhesion Strength of Transparent Photocatalytic TiO2–ZnO Coatings on Polycarbonate

Abstract: Transparent layers containing TiO2 have been intensively studied because of their interesting application potential including photocatalytically active and self-cleaning surfaces. In the present work, transparent TiO2–ZnO thin films on a SiO2 interlayer were successfully deposited on the surface of polycarbonate to provide polymeric sheets with a self-cleaning, superhydrophilic, and photocatalytically active surface layer. To ensure a good adhesion of the SiO2 interlayer, the polycarbonate sheets were first modified by irradiation with UV(C) light. The prepared films were characterized by UV/vis spectrophotometry, SEM, XRD, Raman spectroscopy, ellipsometry, and water contact-angle measurements. All prepared films are transparent, have thicknesses in the range between 120 and 250 nm, and possess superhydrophilic properties. Moreover, they exhibit good adhesion qualities as defined quantitatively by cross-cut tests. However, their mechanical strengths, checked by felt-abrasion tests, differ by changing the ...

Interactions, structure and properties in poly(lactic acid)/thermoplastic polymer blends

Abstract: Blends were prepared from poly(lactic acid) (PLA) and three thermoplastics, polystyrene (PS), polycarbonate (PC) and poly(methyl methacrylate) (PMMA). Rheological and mechanical properties, structure and component interac- tions were determined by various methods. The results showed that the structure and properties of the blends cover a rela- tively wide range. All three blends have heterogeneous structure, but the size of the dispersed particles differs by an order of magnitude indicating dissimilar interactions for the corresponding pairs. Properties change accordingly, the blend con- taining the smallest dispersed particles has the largest tensile strength, while PLA/PS blends with the coarsest structure have the smallest. The latter blends are also very brittle. Component interactions were estimated by four different methods, the determination of the size of the dispersed particles, the calculation of the Flory-Huggins interaction parameter from sol- vent absorption, from solubility parameters, and by the quantitative evaluation of the composition dependence of tensile strength. All approaches led to the same result indicating strong interaction for the PLA/PMMA pair and weak for PLA and PS. A general correlation was established between interactions and the mechanical properties of the blends.

Bisphenol A exposure and cardiac electrical conduction in excised rat hearts.

Abstract: Background: Bisphenol A (BPA) is used to produce polycarbonate plastics and epoxy resins that are widely used in everyday products, such as food and beverage containers, toys, and medical devices

Glass transition temperature of thin polycarbonate films measured by flash differential scanning calorimetry

Abstract: Flash differential scanning calorimetry was used to study the glass transition temperature Tg of polycarbonate ultrathin films. The investigation was made as a function of film thickness from 22 to 350 nm and over a range of cooling rates from 0.1 to 1000 K/s. Polycarbonate spin cast films were floated on a layer of grease on the calorimetric chip. The results show a greatly reduced glass temperature for the thinnest films relative to the macroscopic value. We also observed that the magnitude of the glass temperature reduction decreases as the cooling rate increases with the highest cooling rates showing little thickness dependence of the Tg. Dynamic fragility and activation energy at Tg were found to decrease with decreasing film thickness. The results are discussed in the context of literature reports for supported and freely standing polycarbonate films. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1462–1468

One-step surface modification for irreversible bonding of various plastics with a poly(dimethylsiloxane) elastomer at room temperature

Abstract: Here, we introduce a simple and facile method for bonding poly(dimethylsiloxane) (PDMS) to various plastics irreversibly via a one-step chemical treatment at room temperature. This was mediated by poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane] (amine-PDMS linker), a chemical composed of a PDMS backbone incorporating an amine side group. Room temperature anchoring of the linker was achieved via a reaction between the amine functionality of the linker and the carbon backbone of the plastics, thereby producing urethane bonds. This resulted in the PDMS functionality being exposed on the plastic surface, mimicking the surface properties of bulk PDMS. Following corona treatment of the PDMS-modified plastic and a sheet of PDMS, the two surfaces were placed in contact with each other and heated at 80 °C for 1 h. This resulted in permanent bonding between PDMS and the plastic. To examine the effectiveness of the amine-PDMS linker coating procedure, the surfaces were characterized by measuring water contact angles and by employing X-ray photoelectron spectroscopy (XPS). Polycarbonate (PC), poly(ethylene terephthalate) (PET), poly(vinylchloride) (PVC), and polyimide (PI) were bonded successfully to PDMS using this method, with bond strengths of PC, PET, and PVC with PDMS measured to be approximately 428.5 ± 17.9, 361.7 ± 31.2, and 430.0 ± 14.9 kPa, respectively. The bond strength of a PC-PC homogeneous assembly, also realized using the proposed method, was measured to be approximately 343.9 ± 7.4 kPa. Delamination tests revealed that the PC-PC assembly was able to withstand intense introduction of a liquid whose per-minute injection volume was approximately 278 times greater than the total internal volume of the microchannel fabricated in PC. This demonstrated the robustness of the seal formed using the proposed technique.

The influence of ZnO nanoparticles on thermal and mechanical behavior of polycarbonate-based polyurethane composites

Abstract: In this work a series of thermoplastic polycarbonate-based polyurethane (PC-PU) nanocomposites were prepared by addition of ZnO nanoparticles (0.5, 1 and 2 wt.%) in one-step procedure using all aliphatic starting reactants. The influence of zinc oxide on the structure and hydrogen bonding of PC-PU hybrid materials was studied by Fourier transform infrared spectroscopy (FT-IR). Thermal stability and thermal properties of obtained nanocomposites were studied by thermogravimetry (TGA) and differential scanning calorimetry (DSC), respectively. The effect of phase separation on the mechanical performances was determined by tensile measurements. It was found that the addition of ZnO particles may cause the disruption of phase separation and, hence, affect thermal and mechanical behavior of segmented polycarbonate-based polyurethane nanocomposites.

Experimentally simulating high-rate behaviour: rate and temperature effects in polycarbonate and PMMA.

Abstract: This paper presents results from applying a recently developed technique for experimentally simulating the high-rate deformation response of polymers. The technique, which uses low strain rate experiments with temperature profiles to replicate high-rate behaviour, is here applied to two amorphous polymers, polymethylmethacrylate (PMMA) and polycarbonate, thereby complementing previously obtained data from plasticized polyvinyl chloride. The paper presents comparisons of the mechanical data obtained in the simulation, as opposed to those observed under high-rate loading. Discussion of these data, and the temperature profile required to produce them, gives important information about yield and post-yield behaviour in these materials.

Universal hydrophilic coating of thermoplastic polymers currently used in microfluidics

Abstract: A number of materials used to fabricate disposable microfluidic devices are hydrophobic in nature with water contact angles on their surface ranging from 80° to over 100°. This characteristic makes them unsuitable for a number of microfluidic applications. Both the wettability and analyte adsorption parameters are highly dependent on the surface hydrophobicity. In this article, we propose a general method to coat the surface of five materials: polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), polyethylene terephthalate (PET), polycarbonate (PC), and polytetrafluoroethylene (PTFE). This fast and robust process, which is easily implementable in any laboratory including microfabrication clean room facilities, was devised by combining gas-phase and wet chemical modification processes. Two different coatings that improve the surface hydrophilicity were prepared via the "dip and rinse" approach by immersing the plasma oxidized materials into an aqueous solution of two different poly(dimethylacrylamide) copolymers incorporating a silane moiety and functionalized with either N-acryloyloxysuccinimide (NAS) (poly(DMA-NAS-MAPS) or glycidyl methacrylate (GMA) (poly(DMA-GMA-MAPS). The coating formation was confirmed by contact angle (CA) analysis comparing the variation of CAs of uncoated and coated surfaces subjected to different aging treatments. The antifouling character of the polymer was demonstrated by fluorescence and interferometric detection of proteins adsorbed on the surafce. This method is of great interest in microfluidics due to its broad applicability to a number of materials with varying chemical compositions.

Characterization of Thermo-Mechanical and Fracture Behaviors of Thermoplastic Polymers

Abstract: In this paper the effects of the strain rate on the inelastic behavior and the self-heating under load conditions are presented for polymeric materials, such as polymethyl methacrylate (PMMA), polycarbonate (PC), and polyamide (PA66). By a torsion test, it was established that the shear yield stress behavior of PMMA, PC, and PA66 is well-described by the Ree-Eyring theory in the range of the considered strain rates. During the investigation, the surface temperature was monitored using an infrared camera. The heat release appeared at the early stage of the deformation and increased with the strain and strain rate. This suggested that the external work of deformation was dissipated into heat so the torsion tests could not be considered isothermal. Eventually, the effect of the strain rate on the failure modes was analyzed by scanning electron microscopy.

Benzyl Chloride-Functionalized Polycarbonates: A Versatile Platform for the Synthesis of Functional Biodegradable Polycarbonates

Abstract: An aliphatic polycarbonate containing pendant benzyl chloride groups was synthesized by organocatalytic ring-opening polymerization (ROP) of a cyclic carbonate monomer (MTC–OCH2BnCl). Facile postpolymerization modification of the resultant polymer with various nucleophiles facilitated access to a functionally diverse variety of polycarbonate materials in high yield, including those that contained diethanolamine, phosphonium, and azide groups. The azide-functionalized polycarbonates could be further elaborated via Cu-catalyzed click chemistry with alkynyl-functionalized poly(ethylene glycol) (PEG) or pyrene to form the corresponding PEG- or pyrene-grafted polymers. Finally, an amphiphilic block copolymer containing grafted pyrene units in the hydrophobic block was synthesized using the aforementioned postpolymerization click functionalization strategy. We show by transmission electron microscopy (TEM) and light scattering that the block copolymer self-assembles into micelles of ∼48 nm diameter in aqueous m...

The Effect of Surface Chemistry of Graphene on Cellular Structures and Electrical Properties of Polycarbonate Nanocomposite Foams

Abstract: Electrically conductive polycarbonate (PC) nanocomposites are prepared by blending PC with thermally exfoliated graphene and p-phenylenediamine (PPD)-functionalized and reduced graphene oxide (GO-P...

Waterborne UV-curable polycarbonate polyurethane nanocomposites based on polydimethylsiloxane and colloidal silica with enhanced mechanical and surface properties

Abstract: Waterborne UV-curable polycarbonate polyurethane (PCD–WUPU) nanocomposites based on polydimethylsiloxane (PDMS) and aqueous colloidal silica were prepared via an inverse emulsification process. The effects of PDMS and silica on colloidal dispersions as well as the morphology and properties of the nanostructured films were investigated. It was found that the homogeneous dispersion and network structure of silica clusters in the PCD–PDMS–WUPU matrix resulted in a significantly enhanced modulus, tensile strength, elongation at break (toughness), and thermal stability of the nanocomposite films. It was also very interesting to find that the incorporation of silica did not decrease or increase surface hydrophobicity and water resistance of the PCD–PDMS–WUPU films because of the microphase separation surface structure of the PDMS chain. The high mechanical and surface hydrophobic properties will significantly broaden the industrial applications of WUPU, especially for water-based UV-curable coatings with abrasion or scratching resistance and water resistance.

Interior train components having low smoke and low heat release, and methods of their manufacture

Abstract: A railway component comprises a polycarbonate composition comprising: a first polycarbonate selected from a linear polycarbonate homopolymer, a branched polycarbonate, a poly(carbonate-bisphenol arylate ester), a poly(aliphatic ester-carbonate), or a combination thereof; a second polymer different from the first polycarbonate, the second polymer comprising a poly(carbonate-siloxane) copolymer, a polydialkylsiloxane, a silicone graft copolymer, or a combination thereof, wherein siloxane units in the second polymer are present in an amount of 0.3 to 3 wt. %, based on the total weight of the composition; and 10 to 40 wt. % of glass fiber, based on the total weight of the polycarbonate composition.

Synthesis of fully alternating polycarbonate with low Tg from carbon dioxide and bio-based fatty acid

Abstract: The selective copolymerization of CO2 and an epoxide to form fully alternating polycarbonates is a great challenge via catalysis with the zinc–cobalt(III) double metal cyanide complex [Zn–Co(III) DMCC]. We describe the first perfectly alternating copolymerization of CO2 with a bio-based epoxide. The resultant polycarbonate had a low Tgs of −38 to −44 °C and two end hydroxyl groups, which were then used to initiate ring-opening polymerization of L-lactide via metal-free catalysis, affording a biodegradable triblock copolymer. This study provides a new platform copolymer for making various advanced polymers with biodegradable properties.

Polycarbonate resin composition

Abstract: The present invention relates to a polycarbonate resin composition including both of silicone oil and olefin-based wax at a proper ratio and thus having improved dispersibility of titanium dioxide in the composition as well as high impact strength and melt index (moldability), and also relates to a polycarbonate molded article made of the polycarbonate resin composition. The polycarbonate resin composition according to the present invention includes silicone oil and olefin-based wax at a proper ratio and thus improves dispersibility of titanium dioxide which is added to the composition to give whiteness, while preserving high impact strength and melt index (moldability), so that crawling which is generated on the surface of a final product of polycarbonate molded article is prevented and the appearance property of the molded article is improved. Therefore, the polycarbonate resin composition according to the present invention has characteristics of high whiteness as well as high impact strength and melt index (moldability), and thus is easily applicable to industries in need of the polycarbonate resin.

Polycarbonate resin composition for thin optical component, and thin optical component

Abstract: A polycarbonate resin composition for a thin optical component is provided, which has a high transmittance and a good hue and an excellent resistance to thermal discoloration, and a thin optical component is also provided. The polycarbonate resin composition for a thin optical component comprising, per 100 mass parts of a polycarbonate resin (A), 0.1 to 2 mass parts of a polyalkylene ether glycol compound (B) represented by general formula (1) and 0.005 to 0.5 mass parts of a phosphorus stabilizer (C).

Probing the Role of Poly(3,4-ethylenedioxythiophene)/Poly(styrenesulfonate)-Coated Multiwalled Carbon Nanotubes in the Thermal and Mechanical Properties of Polycarbonate Nanocomposites

Abstract: The role played by multiwalled carbon nanotubes (MWCNTs) coated with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) in the thermal and mechanical properties of polycarbonate (PC) nanocomposites was analyzed. We used differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to demonstrate that the glass transition temperature of polycarbonate nanocomposites decreased whereas the storage modulus of the samples increased by including PEDOT/PSS-coated MWCNTs. These results indicated that PEDOT/PSS acts as an antiplasticizer. We attributed the enhancement of the storage modulus to the strong hydrogen bonding between PSS and the PC matrix and the reduction of the free volume in the PC matrix due to the shrinkage of PEDOT/PSS upon heating. We also investigated changes in the thermal conductivity and thermal degradation behavior of the nanocomposites. The results indicated that PEDOT/PSS did not play a significant role in improving the thermal conductivity and thermal stab...

Influence of water sorption on mechanical properties of injection-molded thermoplastic denture base resins

Abstract: Objective. This study investigated the influence of water sorption on certain mechanical properties of injection-molded thermoplastic denture base resins. Materials and methods. Six thermoplastic resins (two polyamides, two polyesters, one polycarbonate, one polymethylmethacrylate) and a polymethylmethacrylate (PMMA) conventional heat-polymerized denture-based polymer, selected as a control, were tested. Specimens of each denture base material were fabricated according to ISO 1567 specifications and were either dry or water-immersed for 30 days (n = 10). The ultimate flexural strength, the flexural strength at the proportional limit and the elastic modulus of the denture base materials were calculated. Results. Water sorption significantly decreased the ultimate flexural strength, the flexural strength at the proportional limit and the elastic modulus of one of the polyamides and the PMMAs. It also significantly increased the ultimate flexural strength of the polycarbonate. Conclusion. The mechan...

Treatment of polycarbonate by dielectric barrier discharge (DBD) at atmospheric pressure

Abstract: Generally most plastic materials are intrinsically hydrophobic, low surface energy materials, and thus do not adhere well to other substances. Surface treatment of polymers by discharge plasmas is of great and increasing industrial application because it can uniformly modify the surface of sample without changing the material bulk properties and is environmentally friendly. The plasma processes that can be conducted under ambient pressure and temperature conditions have attracted special attention because of their easy implementation in industrial processing. Present work deals with surface modification of polycarbonate (PC) by a dielectric barrier discharge (DBD) at atmospheric pressure. The treatment was performed in a parallel plate reactor driven by a 60Hz power supply. The DBD plasmas at atmospheric pressure were generated in air and nitrogen. Material characterization was carried out by contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The surface energy of the polymer surface was calculated from contact angle data by Owens- Wendt method using distilled water and diiodomethane as test liquids. The plasma-induced chemical modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. Due to these surface modifications the DBD-treated polymers become more hydrophilic. Aging behavior of the treated samples revealed that the polymer surfaces were prone to hydrophobic recovery although they did not completely recover their original wetting properties.

Low percolation threshold and high electrical conductivity in melt‐blended polycarbonate/multiwall carbon nanotube nanocomposites in the presence of poly(ε‐caprolactone)

Abstract: This study focuses on the electrical properties of polycarbonate (PC)/poly(e-caprolactone) (PCL)-multiwall carbon nanotube (MWCNT) nanocomposites. MWCNTs were incorporated into thermoplastic PC matrix by simple melt blending using biodegradable PCL based concentrates with MWCNT loadings (3.5 wt%). Because of the lower interfacial energy between MWCNT and PCL, the nanotubes remain in their excellent dispersion state into matrix polymer. Thus, electrical percolation in PC/PCL-MWCNT nanocomposites was obtained at lower MWCNT loading rather than direct incorporation of MWCNT into PC matrix. AC and DC electrical conductivity of miscible PC/PCL-MWCNT nanocomposites were studied in a broad frequency range, 101−106 Hz and resulted in low percolation threshold (pc) of 0.14 wt%, and the critical exponent (t) of 2.09 from the scaling law equation. The plot of logσDC versus p−1/3 showed linear variation and indicated the existence of tunneling conduction among MWCNTs. At low MWCNT loading, the influence of large polymeric gaps between conducting clusters is the reason for the frequency dependent electrical conductivity. Transmission electron microscopy and field emission scanning electron microscopy showed that MWCNTs were homogeneously dispersed and developed a continuous interconnected network path throughout the matrix phase and miscibility behavior of the polymer blend. POLYM. ENG. SCI., 54:646–659, 2014. © 2013 Society of Plastics Engineers