Polycarbonate Solution Research Articles

Manipulating epoxy-polycarbonate sandwich films with enhanced dielectric performance via solution-immersion process

Epoxy-polycarbonate sandwiched films with enhanced dielectric performance were prepared in this study. Unlike traditional tedious multiple scratch-coating approach, the sandwich dielectric films were prepared based on a convenient solution-immersion process. Polycarbonate solutions with different concentration were applied to adjust the film composition and compared with epoxy-polycarbonate blending film. We found that rather than deteriorating the breakdown strength as shown in the blending counterpart, sandwiched films prepared by solution immersion shows superior breakdown strength (709.6 MV/m), almost 40 % better than both epoxy and polycarbonate components. Moreover, tan δ of the films prepared from solution-immersion (<0.005) is apparently smaller than blending samples (∼0.008). Both factors lead to admirable ideal dielectric energy storage performance (8.44 J/cm3) of the film, better than many conventional polymers.

Experimental investigations on the beta attenuation properties of lead monoxide – Polycarbonate composite films

Lead monoxide filled polycarbonate polymer composite films have been prepared with twelve different filler levels, ranging from 0.5 up to 10.0 percent by weight, by using ultrasonic dispersion of lead monoxide in the polycarbonate solution, followed by solution casting. For these composites, beta radiation shielding properties such as mass attenuation coefficient, range of beta particles and half value layer thickness for beta particles from low activity thallium −204 and yttrium – 90 radioactive sources have been found experimentally and computationally, along with the mass density and modified atomic number of the composite material. Two different computational methods, namely, Baltakment’s empirical formula method and Bragg’s mixture rule have been used to calculate the theoretical value of mass attenuation coefficient, whereas Katz and Penfold relationship has been used to calculate the range of the beta particles obtained from these sources in the prepared composite films. The results obtained are discussed.

Additive manufacturing of multimaterial and multifunctional structures via ultrasonic embedding of continuous carbon fiber

Multimaterial and multifunctional parts were fabricated using an ultrasonic embedding technology in combination with 3D printing of thermoplastic. Continuous carbon fiber (CF) bundles were impregnated with polycarbonate solution (7 wt.%) prior to use in the embedding process. Using an ultrasonic embedding tool, a single layer of CF bundle was embedded into 3D printed polycarbonate parts containing one of three raster angles (RA): 0°, +45/-45°, and 90° RA. In tensile testing, the highest ultimate tensile stress (UTS) was found in samples printed with +45/-45° RA (75% higher UTS when compared to neat samples having the same RA), followed by those printed with 0° RA (60% UTS increase). Samples printed with 90° RA and containing a single layer (bundle) of embedded CF yielded the least UTS improvement (13%). Statistical t-test results showed that +45/-45° RA samples with embedded CF had superior mechanical strength while exhibiting less variation. Flexural testing of +45/-45° RA specimens with embedded CF showed an average flexural strength increase of 7%, and an average modulus increase of 7% when compared to the neat specimen. In addition to the mechanical reinforcement, multilayer CF embedding using ultrasonic energy was demonstrated. In addition, the change in electrical resistance in embedded CF layers was measured during mechanical loading to demonstrate structural health monitoring functionality.

Study of polycarbonate–bismuth nitrate composite for shielding against gamma radiation

Polycarbonate (PC) loaded with different filler levels equal to 0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 2.5, 3.5 and 5.0 wt% (weight percent) of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O or BNP) were prepared by dispersion of filler in PC solution, followed by casting. The values of mass attenuation coefficient (μm), effective atomic number (Zeff), effective electron density (Nel), half value layer (HVL) thickness, tenth value layer (TVL) thickness and photon mean free path (MFP or λ) were determined for specific gamma photon energies ranging from 303 up to 1332 keV, both computationally and experimentally. Considerable variation in the radiation attenuation parameters was observed, which is mainly dependent on the energy of incident gamma ray photon and the concentration of BNP incorporated as filler within the PC matrix. Values of the experimentally determined parameters like μm, Zeff and Nel were compared with the computationally estimated values, and they are found to be in good agreement. The results are discussed, taking into consideration our understanding of the interaction of gamma radiation with matter.

Perylene-doped polycarbonate coatings for acrylic active greenhouse luminescent solar concentrator dryers

Red fluorescent Polycarbonate (PC) films were prepared by solvent-casting technique from PC solution doped with different dye concentrations of perylene dyestuff (KREMER Red 94720). The effect of the dye concentration on the structure and photophysical properties was studied using X-ray diffraction, UV–Vis and fluorescence spectroscopy. The optimum dye concentration of red fluorescent PC films showed the best emission efficiency for the doping concentration 0.3 wt%. These results endorsed a new application of this film for active greenhouse luminescent solar concentrator dryers (LSCDs) with enhanced feature of integrated solar powered convection. Field performance of LSCD prototype was examined under normal climatic conditions of Riyadh city (24.68 N, 46.72 E) during summer. The final moisture content was calculated for five kinds of fruits (banana, mango, lemon, fig, and tomato) which showed a better product quality and less drying time for LSCD compared to open sun drying.

Novel radiochromic porphyrin-based film dosimeters for γ ray dosimetry: investigation on metal and ligand effects

Abstract As the utilizing of porphyrins and metalloporphyrins in high dose dosimetry becomes more prevalent, research on structural effects of these molecules on dosimetric characteristics and physicochemical properties of their film dosimeters becomes more and more essential. The present study emphasizes dosimetry (measuring radiolytic bleaching of two novel film dosimeters with spectrophotometric methods against 60Co γ-rays exposure in dose range of 0–100 kGy) and evaluating substituent effects on the radiation response of the film dosimeters (role of organic groups and changing the metal core of porphyrins). With casting of solutions of polycarbonate (PC) containing 0.5 wt.% 5,10,15,20-Tetrakis(2,4,6-trimethoxyphenyl) porphyrin (TTMPP) and 5,10,15,20-Tetraphenyl-21H,23H-porphine manganese (III) chloride (Mn-TPP), two novel radiochromic films with the thickness of 20 μm were fabricated. The presence of porphyrin fragments has been observed in the UV–Vis spectra after γ radiation. Due to the changes of the metal core and substituents of the dye ring, meaningful shifts of maximum absorbance of Soret bands of porphyrins and different radiation response of film-dosimeters were observed. The results were compared with the other polycarbonate/porphyrin film dosimeters. The results indicate that the radiation-induced decoloration of PC/Porphyrin films can be reliably tuned and used in high dose dosimetry.

Structuring of the Surface Layer of Polycarbonate Film upon Interaction with Nematic Liquid Crystal

The structure formation observed in the surface layer of polycarbonate which proceeds when nematic liquid crystal is deposited on a film is studied. Films prepared from polycarbonate solutions in dichloromethane, chloroform, or pyridine and dried in thermobalance at different temperatures and different drying times are studied. Textures are prepared in the process of domain growth. The effect of the orientation of the disclination lines in a magnetic field and the memory effect of molecular ordering after removal and redeposition of the liquid crystal layer are observed. The process of structure formation is analyzed on the basis of the model of cooperative interaction of liquid crystal molecules with polymer chains taking into account the adsorption mechanism.

A Robust Fabrication Method for Amphiphilic Janus Particles via Immobilization on Polycarbonate Microspheres.

Immobilizing particles on beads, fibers, or filaments, when only one side is exposed to the reaction medium and therefore can be selectively functionalized, is a scalable and easy to control strategy for the fabrication of amphiphilic Janus particles. Here we describe a new, robust method for the fabrication of amphiphilic Janus particles based on immobilization of polymethylsilsesquioxane (PMSQ) particles on polycarbonate (PC), a high impact-resistance polymer with superior mechanical properties. The immobilization of the particles on the PC microspores is performed via inverse solvent displacement method. PMSQ particles are added to a PC solution in tetrahydrofuran (THF), a good solvent for PC. The solution is then precipitated by the introduction of aqueous surfactant solution (antisolvent for PC) under an ultrasonic field. It is important to note that THF and water are miscible and do not form emulsion. During precipitation, PMSQ particles are assembled onto the surface of the PC spherical precipitates/microspheres. The exposed hemispheres of the PMSQ particles are then selectively silanized by (3-Aminopropyl)triethoxysilane (APTES) to introduce amine groups on their surface. To increase the polarity of the functionalized hemispheres, the amine groups are further modified to introduce carboxyl groups. SEM characterization confirms the fine embedment of PMSQ particles onto the PC microspheres. Covalent attachment of silica nanoparticles (NPs) to the functionalized hemispheres of the resulting particles along with fluorescent confocal microscopy conclusively prove the successful fabrication of amphiphilic Janus particles. The immobilization of particles onto highly rigid polymeric microspheres such as PC may pave the way for the development of a robust fabrication procedure with high resistance to temperature fluctuations and harsh mixing conditions that can arise during preparation. This method can be implemented toward a large variety of other synthetic commercial polymers such as polyamide, polyether sulfones, Polyether, ether ketone, or similar.

Fabrication of thioflavin‐T‐modified nanopillared SERS substrates for ultrasensitive beta‐amyloid peptide detection

AbstractAlzheimer disease (AD) is a major cause of death in the world, and despite intense efforts, there is still no cure for this neurodegenerative disorder. Therefore, early diagnosis of AD is of prime importance, and extensive studies are being conducted to improve the current early detection capabilities and to identify new potential biomarkers for this disease. Here in, we report the fabrication of a novel nanobiosensor platform for the surface‐enhanced Raman spectroscopy (SERS)‐based ultrasentisitive detection of beta‐amyloid (1–42) peptide (Aβ[1–42]), a well‐established biomarker of AD. Polymeric films having multibranched nanopillared surfaces (MNS) were first fabricated by drop‐casting polycarbonate solutions onto anodized aluminum oxide molds that possess hierarchically branched pores. After peeling from the nanoporous molds, a 20‐nm Au coating allowed these MNS substrates to sense sub‐picomolar levels of Thioflavin‐T (ThT), a SERS‐active dye, clinically used to diagnose amyloid plaque presence. Of particular interest, the ThT‐modified MNS films demonstrated a gradual ThT SERS signal suppression when incubated with increasing concentrations of Aβ(1–42), and this trend was used to obtain a limit of detection value of 0.5 pg/ml and a linear dynamic range between 0.5 pg/ml and 100 ng/ml. The developed biosensor platform has stable ThT SERS signals for extended periods and displayed promising results in artificial saliva. Ongoing studies are focused on its potential with real body fluids.

The effect of concentration and molecular weight of polycarbonate on the elastic constants of a nematic liquid crystal solvent

We utilized the Light Scattering from Anisotropy of Turbidity (LSAT) method and determined the three Frank’s elastic constants of; "splay" (K1), "twist" (K2) and "bend" (K3), in dilute solutions of polycarbonate (PC) in 4-pentyl-4’-cyanobiphenyl (5CB) nematic liquid crystal solvent. Within the limited solubility range of PC/5CB solutions, we determined the elastic constants of 5CB as a function of the concentration and molecular weight of PC. The results showed that K2 increases, K1 and K3 decrease, whereas K1/K3 and <K> ratio remain almost invariant by increasing the PC concentration and molecular weight.In contrast to the theoretical models and experimental data, the values and trends of K1, K2 and K3 moduli indicate that, increase of K2 at the expense of K1 and K3 moduli is due to extended chain conformation PC polymer structure and enhancment of lateral interactions between PC and 5CB moieties.

Evaluation of Uniformity and Glare Improvement with Low Energy Efficiency Losses in Street Lighting LED Luminaires Using Laser-Sintered Polyamide-Based Diffuse Covers

Energy saving in street lighting is garnering more interest and has become a priority in municipal management. Therefore, LED luminaires are gradually becoming prevalent in our cities. Beyond their energy/economic saving potential, quality in public lighting installations concerns aspects such as uniformity and glare which must be maintained if not improved in any installation renewal project using this technology. The high light intensity generated in a discrete point in LED packages and its directional nature result in significant deficiencies in these last two parameters. To soften these effects, translucent covers are being used as one of the most common solutions with the drawback of significant light intensity losses. The objective of this paper is to evaluate the behavior of LED luminaire’s polyamide-based optical covers manufactured with a laser-sintered process. These are designed to improve glare and uniformity output, to minimize light output reductions, and to be industrially manufactured with no increment of cost for their lighting equipment compared to conventional transparent polycarbonate solutions. A laboratory and field lighting test study has been applied to different covers with the same LED lamp and luminaire to compare the performance of three different solutions built with different polymeric materials and with different light transmission surface textures. The photometric results have been observed and discussed to demonstrate the ability to significantly improve the lighting performance of LED luminaires—illuminance and uniformity levels and discomfort and disability glare indexes— using an improved optic cover.

Dosimetric characterization of novel polycarbonate/porphyrin film dosimeters for high dose dosimetry: study on complexation effect

Abstract Two novel radiochromic films with 20 μm thickness were made from casting of solutions of polycarbonate (PC) containing 0.5 wt.% tetra phenyl porphyrin (TPPH2) and 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe-TPP). Dosimetric characterization of the films as routine dosimeters were studied by spectrophotometric method. On subjecting TPPH2/PC and Fe-TPP/PC film dosimeters to gamma radiation, radiolytic bleaching of films was observed. The effects of metal-complexation on the radiation response of the film dosimeters were studied under 60Co γ-rays exposure in dose range of 0–100 kGy. The results were also compared with the PC/TPPF20 (PC/tetrakis (pentafluorophenyl) porphyrin) dosimeter to evaluate the substituent effect (role of fluorine groups). Experimental parameters including humidity, temperature and pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were examined. The maximum absorbance of Soret band of dyes had meaningful shifts and reduction which arose from complexation and substituents. The dyed films characteristics were found to be stable enough in media with high degrees of temperature and humidity. The results indicate that the radiation-induced decoloration of TPPH2/PC and Fe-TPP/PC films can be reliably tuned and used in high dose dosimetry.

Fabrication of a flexible polycarbonate/porphyrin film dosimeter for high dose dosimetry

Abstract Dyed polycarbonate (PC) Radiochromic films with 20 μm thickness were prepared by casting of organic solution of PC containing 0.5 wt.% tetrakis (pentafluorophenyl) porphyrin (TPPF20) on a glass petri dish. Characterization of the film as a routine dosimeter was studied. On subjecting PC/TPPF20 film dosimeter to gamma radiation, a gradual decrease in the color of films was observed. The sensitivity of these films and the linearity of dose-response curves were studied under 60Co γ-rays expose in dose range of 0–100 kGy. The results were compared with the commercial and non-commercial dosimeters. Experimental parameters including humidity, temperature and pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were examined. The maximum absorbance of soret band of TPPF20 had a bathochromic shift and appeared at 414 nm which remained intact in the investigated dose range. The dyed films characteristics were found to be stable enough in media with high degrees of temperature and humidity. The results indicate that radiation induced decoloration of PC/TPPF20 films can be reliably used in high dose dosimetry.

Phase Behavior and Ternary Diagram Construction for Membrane Forming Polycarbonate Solutions

Cloud points at different polymer concentrations were obtained by the simple titration method and compared with the numerically calculated theoretical binodal curves for Polycarbonate/Dimethylacetamide/Water (PC/DMAc/Water) and Polycarbonate/N-Methyl-2-pyrrolidone/Water (PC/NMP/Water). The interaction parameters for solvent polymer and nonsolvent polymer were obtained from Hansen's solubility parameters. The cloud points determined were found to be in close agreement with the theoretical binodal curve calculated. Coagulation values for different solvents such as Dichloromethane (DCM), Dimethylacetamide (DMAc), N-Methyl-2-pyrrolidone (NMP) and Tetrahydrofuran (THF) were also determined and the results were plotted in a ternary diagram to realize the effect of interaction parameters on the coagulation values. The higher the mutual affinity of solvent to polymer (low χ23), the faster is the liquid-liquid demixing rate to occur. For DCM solvent, fastest demixing rate was exhibited and lowest for the THF.

A multi-functional polymer coating that is heat-resistant, hydrophobic and transparent

A multi-functional polymer film with high hydrophobicity and transparency was formed by simple casting of a polycarbonate solution onto a substrate having micro-scale roughness. The high hydrophobicity was heat-resistant, which can be retained up to 390°C. The polymer film may have potentially wide-ranging applications in industry and high technology.

Rheological properties of novel thermo-responsive polycarbonates aqueous solutions

Thermo-responsive multiblock polycarbonates were facilely synthesized by covalently binding poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) blocks, using triphosgene as coupling agent and pyridine as catalyst. The aqueous solutions of thermo-responsive polycarbonates were investigated by rheological measurements. Steady-state shear measurements reveal that the polycarbonate solutions exhibit shear-thinning behavior and the hydrophilic content has a pronounced effect on the flow behavior of the polycarbonates aqueous solutions. The shear viscosity decreases with increasing poly(ethylene oxide) (PEO) composition. The increase of viscosity with increasing concentration is probably attributed to the formation of stronger network owing to interchain entanglement of PEO block at higher concentration. When the flow curves are fitted to the power law model, flow index is obtained to be less than 1, as exhibiting typical pesudoplastic fluid. The viscoelastic properties of the system also show close dependence on the composition of polycarbonates. Temperature sweep confirms that the multiblock polycarbonates exhibit thermo-responsive properties. For 7% aqueous solution of polycarbonate with composition ratio of EO to PO of 1/1, the sol-gel transition occurs at 37 °C, which makes the system suitable as an injectable drug delivery system.

The morphology, mechanical properties, and flammability of aligned electrospun polycarbonate (PC) nanofibers

AbstractThe electrospinning of the polycarbonate (PC) solutions was performed for the variable electrospinning parameters such as polymer concentration, solvent composition, applied voltage, flow rate, and take‐up velocity in order to evaluate changes of morphology, mechanical properties, and flammability of the aligned PC nanofibers as a function of the electrospinning parameters. It was found that the ratio of THF/DMF solvent in the electrospinning parameters had a major effect on the spinnability and fiber morphology. Furthermore, it was confirmed that the mechanical properties were dependent upon the fiber morphology. The spinnability of the PC solutions with a lower THF ratio in THF/DMF solvent was poor. The aligned electrospun PC fiber with the best morphology was made in the range of polymer concentration of 22%, solvent ratio of 50:50 THF : DMF, applied voltage of 14 kV, flow rate of 0.050 ml/m, and a take‐up velocity of 7.3 m/s. The ultimate strength and initial modulus of the 80% drawn 22% PC fiber were 64 ± 2 MPa (commercial 55–75 MPa) and 1.9 ± 0.1 GPa. The heat release capacity (HRC) of the 22 and 25% PC fiber were 275 ± 27 J/g K and 198 ± 1 J/g K. It was found that the flame resistance of the electrospun PC nanofiber was superior to that of the PC raw material (HRC ∼360 J/g K). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Self-organized Polymer Aggregates with a Biomimetic Hierarchical Structure and its Superhydrophobic Effect

Nature always gives us inspirations to fabricate functional materials by mimicking the structure design of biomaterials. In this article, we report that polymeric aggregates with morphology similar to the papilla on lotus leaf can be self-organized in the polymer solution by adding 16 wt% water into 5 mg/ml polycarbonate solution in N,N'-dimethylformamide. The hierarchically structured aggregates at micro- and nano-scale alone show superhydrophobic effect without the need of modification with low surface energy compound. Small amount of liquid can be wrapped by the aggregates to form the so-called liquid marble. Influence of the amount of water added into the solution on the morphology of resultant polymer aggregates was investigated. By using the hierarchical aggregates as the surface building blocks, superhydrophobic coating with a static water contact angle larger than 160 degrees and sliding angle less than 5 degrees (for a water drop of 5 microl) was formed. Other solutions, like acid, basic and blood plasma are also repelled on the coating.

Preparation and characterization of antimicrobial polycarbonate nanofibrous membrane

Electrospinning of polycarbonate (PC)/chloroform solution with quaternary ammonium salt (benzyl triethylammonium chloride, BTEAC) was investigated to develop antimicrobial nanofibrous membranes for ultrafiltration. With BTEAC additive, ultrafine PC fibers were continuously generated and densely mounted without the blockage of spinning tip on electrospinning. When small amounts of BTEAC were added to the PC solution, the average diameter was also decreased from several micrometers to submicron range. It was found that the conductivity of the PC solution was a major parameter affecting the morphology and diameter of the electrospun PC fibers as well as the electrospinnability of PC. The nanofibrous membranes electrospun from the PC solution with BTEAC exhibited better excellent antimicrobial activity than those prepared without BTEAC. The PC nanofibrous filter shows a good filtration efficiency to satisfy the criterion of HEPA filter, and the pressure drop of the PC filters are within the normal range. Therefore, PC nanofibrous membrane showed a great potential as a candidate for ultrafiltration, compared to a commercial HEPA filter.

Synthesis of Polycarbonate‐Poly(methyl methacrylate) Copolymer via Sonochemical Polymerization of Methyl Methacrylate in Polycarbonate Solution

AbstractMethyl methacrylate (MMA) was polymerized in the presence of polycarbonate (PC) by ultrasonic irradiation‐initiated polymerization. The resulting products consisted of mixtures of homopolymers of poly(methyl methacrylate) (PMMA), PC and PC‐PMMA copolymer because of the homopolymerization of MMA itself and copolymerization with macroradicals of PC. Formation of the PC‐PMMA copolymer was confirmed by FTIR analysis of the reaction products after a proper extraction of free PMMA from the mixture. In order to verify the effectiveness of the PC‐PMMA copolymer as a compatibilizer for PC/styrene‐co‐ acrylonitrile (SAN) blend, 5 phr of PC‐PMMA was added during melt mixing of PC/SAN in a batch mixer. It was found from the investigation of morphology and rheological properties that interphase of SAN and PC was fortified by numerous ligaments of PC‐PMMA copolymer, which resulted in increase of melt viscosity and storage modulus of the blend.