Home About us Contact
|
Home About us Contact | ||
|
|
||
Polycarbonate
Terms modified by Polycarbonate Selected AbstractsPrediction of cooling time in injection molding by means of a simplified semianalytical equationADVANCES IN POLYMER TECHNOLOGY, Issue 3 2003D. M. Zarkadas Abstract A simplified semianalytical equation, used successfully in food freezing/chilling time prediction, is proposed as a potential simple alternative for cooling time prediction in injection molding of polymer parts, amorphous or semicrystalline. This equation is based on a convective boundary condition for the mold-part interface and requires information on the thermal contact resistance (TCR) or thermal contact conductance (TCC) at this interface, as well as information on the initial and final product temperatures, the mold surface temperature, and the thermal properties of the part. Eighty-five data points for four polymers, Polystyrene (PS), Polycarbonate (PC), Polypropylene (PP), and Polyethylene (PE) were generated with C-MOLDÔ, a commercial injection molding design software, and the performance of the proposed equation was tested. The % mean error and its standard deviation (SD) in cooling time prediction were, respectively, ,11.61 and 2.27 for PS, ,6.04 and 2.13 for PC, ,7.27 and 6.55 for PP, and ,8.88 and 2.93 for PE. It was also shown that the accuracy of the proposed equation is not affected significantly by the exact knowledge of the TCC, provided that the latter is not smaller than 1000,2000 W m,2 K,1. Since in this comparison all necessary temperatures were obtained from C-MOLDÔ, methods of using the proposed equation independently were tested. The use of the inlet melt temperature as the initial product temperature increased the % mean error by mostly 1.5% while its SD remained practically the same. By incorporating a literature based heat balance method in the proposed equation, it was possible to use it as a stand-alone predictor of polymer cooling time. The % mean error and its SD calculated this way were, respectively, ,9.44 and 0.97 for PS, ,9.44 and 0.83 for PC, ,14.22 and 5 for PP, and ,20.12 and 1.38 for PE. The proposed equation, at least in a preliminary stage, can be used successfully to predict the cooling time of the selected semicrystalline or amorphous polymers with the accuracy being higher for amorphous polymers. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 188,208, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10048 [source] Organic,Inorganic Interactions in Poly(trimethylene carbonate),Titania HybridsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2009Elisa Cortecchia Abstract Polycarbonate,titania hybrids have been synthesized by a sol,gel reaction, starting from poly(trimethylene carbonate) (PTMC) and titanium isoproproxide in different ratios. PTMC with a given chain length was obtained by ring opening polymerization. FT-IR spectra reveal the presence of TiOC covalent bonds between organic and inorganic phases, and their number increases with increasing inorganic phase content. Solvent extractions show that hybrid soluble fraction contains low PTMC chains with isopropoxide ends, which suggests that TiOC bond formation is mainly promoted by transesterification reactions of isopropyl alcohol onto the polymer chain, catalyzed by Ti compounds. Hybrid thermal properties reflect the combined effect of the decrease of PTMC molecular weight and of bond formation between PTMC and the inorganic network. The nanometric dimension of the TiO2 domains, confirmed by atomic force microscopy, provides optically transparent hybrids. [source] Isothermal Crystallization Kinetics of Poly(, -caprolactone) with Tetramethyl Polycarbonate and Poly(styrene- co -acrylonitrile) Blends Using Broadband Dielectric SpectroscopyMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2006Samy A. Madbouly Abstract Summary: Phase behavior and isothermal crystallization kinetics of poly(, -caprolactone) (PCL) blends with tetramethyl polycarbonate (TMPC) and poly(styrene- co -acrylonitrile) with 27.5 wt.-% acrylonitrile content have been investigated using broadband dielectric spectroscopy and differential scanning calorimeter. An LCST-type phase diagram has been observed for PCL/SAN blend while all the different blend compositions of PCL/TMPC were optically clear without any phase separation structure even at high temperatures up to 300,°C. The composition dependence of Tgs for both blends has been well described by the Gordon-Taylor equation. The phase diagram of PCL/SAN was theoretically calculated using the Flory-Huggins equation considering that the interaction parameter is temperature and composition dependent. The equilibrium melting point of PCL depressed in the blend and the magnitude of the depression was found to be composition dependent. The interaction parameters of PCL with TMPC and SAN could not be calculated from the melting point depression based on Nishi-Wang approach. The isothermal crystallization kinetics of PCL and in different blends was also investigated as a function of crystallization temperature using broadband dielectric spectroscopy. For pure PCL the rate of crystallization was found to be crystallization temperature (Tc) dependent, i.e., the higher the Tc, the lower the crystallization rate. The crystallization kinetics of PCL/TMPC blend was much slower than that of PCL/SAN at a constant crystallization temperature. This behavior was attributed to the fact that PCL is highly interacted with TMPC than SAN and consequently the stronger the interaction the higher the depression in the crystallization kinetics. It was also attributed to the different values of Tg of TMPC (191,°C) and SAN (100,°C); therefore, the tendency for crystallization decreases upon increasing the Tg of the amorphous component in the blend. The analysis of the isothermal crystallization kinetics was carried out using the theoretical approach of Avrami. The value of Avrami exponent was almost constant in the pure state and in the blends indicating that blending simply retarded the crystallization rate without affecting the crystallization mechanism. Dielectric constant, ,,, of pure PCL, blends of PCL/TMPC,=,80/20 and PCL/SAN,=,80/20 as a function of crystallization time at 47,°C and 1 kHz. [source] The Influence of Molecular Orientation on the Yield and Post-Yield Response of Injection-Molded PolycarbonateMACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2009Tom A. P. Engels Abstract The influence of the flow history experienced during injection molding on the mechanical properties of amorphous polymers is investigated. It is demonstrated that flow-induced molecular orientation only causes a small anisotropic effect on the yield stress, which can be regarded as insignificant with respect to its absolute value. Its influence on the post-yield strain-hardening response is also shown to be imperceptible, in contrast to a orientation which is applied during deformation below the glas transition. [source] Improvement of the Long-Term Performance of Impact-Modified Polycarbonate by Selected Heat TreatmentsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2009Tom A. P. Engels Abstract Next to the intended increase of the impact toughness, impact modification of polycarbonate generally results in an unwanted decrease in yield stress and time-to-failure under constant stress. It is demonstrated that this loss in strength can be fully compensated for by an annealing treatment, or by increasing the mold temperature. The influence of impact modification on the short- and long-term strengths of glassy polymers is predicted by the extension of existing models with a scaling rule based on the filler volume percentage. Introduction of this scaling rule in the evolution of yield stress during physical aging even allows for the direct prediction of yield stress on the basis of processing conditions. [source] Polycarbonate Crystallization by Vapor-Grown Carbon Fiber with and without Magnetic FieldMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2003Tatsuhiro Takahashi Abstract Polycarbonate (PC)/vapor-grown carbon fiber (VGCFÔ) composite was prepared through melt compounding. It was unexpectedly found from differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) that the crystallization of PC was substantially accelerated in the presence of the ordered graphite surface of VGCFÔ. To make an aligned structure of PC crystallization together with the orientation of VGCFÔ, a magnetic field of 2.4 T was applied to the composite under several temperature profiles. The WAXD pattern revealed that not only dispersed VGCFÔ but also matrix PC crystallization was magnetically aligned through the optimization of processes. The evidence for PC crystallization by VGCFÔ with and without magnetic force is described. Optical micrograph (a) and WAXD pattern (b) of PC/VGCFÔ (95:5 wt. ratio) composite which was treated under a magnetic field (vertical direction) of 2.4 T under an optimized heating profile. [source] Chemical Micropatterning of Polycarbonate for Site-Specific Peptide Immobilization and Biomolecular InteractionsCHEMBIOCHEM, Issue 3 2007Olivier Carion Dr. Abstract Polycarbonate (PC) is a useful substrate for the preparation of microfluidic devices. Recently, its utility in bioanalysis has attracted much attention owing to the possibility of using compact discs as platforms for the high-throughput analysis of biomolecular interactions. In this article we report a novel method for the chemical micropatterning of polycarbonate based on the printing of functionalized silica nanoparticles. The semicarbazide groups present on the surface of the nanoparticles were used for the site-specific semicarbazone ligation of unprotected peptides derivatized by an ,-oxoaldehyde group. The peptide micropatterns permitted the specific capture of antibodies. We report also the characterization of micropatterns on PC by using a wide-field optical imaging technique called Sarfus; this allows the detection of nm-thick films by using nonreflecting PC substrates and an optical microscope working with reflected differential interference contrast. The method described here is an easy way to modify polycarbonate surfaces for biomolecular interaction studies and should stimulate the use of PC for developing plastic biosensors. [source] A multilayer poly(dimethylsiloxane) electrospray ionization emitter for sample injection and online mass spectrometric detectionELECTROPHORESIS, Issue 24 2005Jamie M. Iannacone Abstract An ESI emitter made of poly(dimethylsiloxane) interfaces on-chip sample preparation with MS detection. The unique multilayer design allows both the analyte and the spray solutions to reside on the device simultaneously in discrete microfluidic environments that are spatially separated by a polycarbonate track-etched, nanocapillary array membrane (NCAM). In direct spray mode, voltage is applied to the microchannel containing a spray solution delivered via a syringe pump. For injection, the spray potential is lowered and a voltage is applied that forward biases the membrane and permits the analyte to enter the spray channel. Once the injection is complete, the bias potential is switched off, and the spray voltage is increased to generate the ESI of the injected analyte plug. Consecutive injections of a 10,,M bovine insulin solution are reproducible and produce sample plugs with limited band broadening and high quality mass spectra. Peptide signals are observed following transport through the NCAM, even when the peptide is dissolved in solutions containing up to 20% seawater. The multilayer emitter shows great potential for performing multidimensional chemical manipulations on-chip, followed by direct ESI with negligible dead volume for online MS analysis. [source] Fracture behaviour of PC/ABS resin under mixed-mode loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2001Husaini Fracture behaviour of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) under mixed-mode loading conditions was studied for several weight fractions of PC and ABS. Mode I and mixed-mode fracture tests were carried out by using compact,tension,shear specimens. At a certain value of mixed-mode loading ratio KII,/KI, a crack of the shear type will initiates at the initial crack tip. Fracture toughness increases under mixed-mode loading with an increase in the mode II component, whereas it reduces with the appearance of a shear-type fracture. Fracture toughness and the appearance of a shear-type fracture depends on the blending ratio of PC and ABS. The transition to shear-type fracture occurs at lower value of KII,/KI for resins with higher fracture toughness. [source] Use of Reversal Nanoimprinting of Nanoparticles to Prepare Flexible Waveguide Sensors Exhibiting Enhanced Scattering of the Surface Plasmon ResonanceADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Dehui Wan Abstract A flexible surface plasmon resonance (SPR)-based scattering waveguide sensor is prepared by directly imprinting hollow gold nanoparticles (NPs) and solid gold NPs onto flexible polycarbonate (PC) plates,without any surface modification,using a modified reversal nanoimprint lithography technology. Controlling the imprinting conditions, including temperature and pressure, allows for the fine adjustment of the depths of the embedded metal NPs and their SPR properties. This patterning approach exhibits a resolution down to the submicrometer level. A 3D finite-difference time domain simulation is used to examine the optical behavior of light propagating parallel to the air/substrate interface within the near-field regime. Consistent with the simulations, almost an order of magnitude enhancement in the scattering signal after transferring the metal NPs from the glass mold to the PC substrate is obtained experimentally. The enhanced signal is attributed to the particles' strong scattering of the guiding-mode waves (within the waveguide) and the evanescent wave (above the waveguide) simultaneously. Finally, the imprinting conditions are optimized to obtain a strongly scattering bio/chemical waveguide sensor. [source] Fire hazard evaluation of thermoplastics based on analytic hierarchy process (AHP) methodFIRE AND MATERIALS, Issue 5 2010Baogang Yu Abstract Combustibility performance of 14 compositions including five main thermoplastics (polycarbonate (PC), polypropylene (PP), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS) and poly (vinyl chloride) (PVC)) was tested by cone calorimeter. The fire growth index, total heat release amount index, total smoke release amount index and toxicity product index were calculated, based on which an index system for evaluating fire hazard was set up. All factors in this index system had been analyzed by the analytic hierarchy process, and the specific weight for each factor had been determined. Then fire hazard of thermoplastics was evaluated considering integrated fire hazard index. The results show that fire hazards of HIPS-phosphate fire retardant (PFR), PVC-non-flame retardant, ABS-brominated flame retardant (BFR) and PC/ABS-PFR are higher than PC-BFR and PP-non-halogenated flame retardant. Copyright © 2009 John Wiley & Sons, Ltd. [source] Cone calorimeter analysis of UL-94 V-rated plastics,FIRE AND MATERIALS, Issue 4 2007Alexander B. Morgan Abstract Cone calorimeter analysis was conducted on 18 thermoplastics with different UL-94 vertical burn test (V) ratings. Ratings varied from V-0 to no rating (NR), and the types of thermoplastics included were polycarbonate (PC), acrylonitrile,butadiene,styrene (ABS), PC/ABS blends, high-impact polystyrene (HIPS), polypropylene (PP), and poly(vinyl chloride) (PVC). Our analysis of the cone calorimeter data found that there were correlations between UL-94 V rating and some cone calorimeter measurements (peak heat release rate (HRR) average and HRR at 60 s) and no relationship for other measurements (time to ignition and total heat release). However, no precise correlation was found due to significant differences in flame retardant mechanism and polymer fuel energy values. In this paper, we seek to explain further why a broad quantitative relationship between UL-94 V and cone calorimeter remains elusive, and also to show how the cone calorimeter can be used to understand why a material passes or fails a particular UL-94 V rating. Copyright © 2006 John Wiley & Sons, Ltd. [source] Carbon Nanotube Polycarbonate Composites for Ultrafast Lasers,ADVANCED MATERIALS, Issue 21 2008Vittorio Scardaci Carbon nanotube polycarbonate composites with controlled nanotube-bundle size are prepared by dispersion with conjugated polymers followed by blending with polycarbonate. The composite has uniform sub-micrometer nanotube bundles in high concentration, shows strong nonlinear optical absorption, and generates 193 fs pulses when used as passive mode-locker in a fiber laser. [source] Identification of the effective distribution function for determination of the distributed activation energy models using the maximum likelihood method: Isothermal thermogravimetric dataINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2009Bojan Jankovi The new procedure for identification of the effective distribution function for determination of the distributed activation energy models, which is based on use the maximum likelihood method (MLM), was established. The five different continuous probability functions (exponential, logistic, normal, gamma, and Weibull probability functions (the extended set of distributions)) were used for searching the best reactivity model for two heterogeneous processes: (a) the isothermal reduction process of nickel oxide under hydrogen atmosphere and (b) the isothermal degradation process of bisphenol-A polycarbonate (Lexan) under nitrogen atmosphere. The MLM showed that for both processes, the most suitable reactivity model represents the Weibull distribution model. It was concluded that the values of Arrhenius parameters (ln A and Ea), evaluated from the Weibull distribution model, represent the effective kinetic values for both considered processes. This procedure enables identification the suitable distribution model for considered process only from the experimental data (based on the shapes of obtained integral kinetic curves), and this fact represents the advantage of established analysis. The established mathematical procedure, which is based on the MLM, can be applied as the preliminary analysis for evaluating the distribution of activation energies for complex heterogeneous processes. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 27,44, 2009 [source] Simple Fabrication Method of Conductive Polymeric Arrays by Using Direct Laser Interference Micro-/Nanopatterning,ADVANCED MATERIALS, Issue 9 2007A. Acevedo Thin films of polyaniline (PANI) deposited onto different polymeric substrates are nanostructured by using "direct laser interference patterning" at room temperature and pressure in air atmosphere. Regular linelike arrays (see figure) with thicknesses up to 600,nm are fabricated and their activity is determined using different techniques. The structuring mechanisms of PANI supported in both polycarbonate and polyimide films are demonstrated using cross-sectional analyses performed with a dual-beam workstation. [source] Physically and chemically modified polycarbonate by metal ion implantationADVANCES IN POLYMER TECHNOLOGY, Issue 3 2008Rashi Nathawat Abstract Changes in physical and chemical properties have been studied for polycarbonate (PC) implanted by 100 keV Ni+ with various fluences from 1 × 1014 to 1 × 1016 ions/cm2. Changes in the surface morphology and composition have been observed with atomic force microscopy and X-ray diffraction (XRD). Ni particles as precipitates in PC were observed by cross-section transmission electron microscopy at the 100-nm depth. Ion implantation induces changes in the topography of PC as indicated by a dramatic increase in surface roughness with ion fluence. Implanted metal ions show direct evidence of compound formation on the surface. Chemical changes in the surface region have been observed by Raman spectroscopy and UV,vis spectroscopy. UV,vis absorption analysis indicates a drastic decline in optical band gap from 5.46 to 1.76 eV at an implanted dose of 1 × 1016 ions/cm2. It is shown that partial destruction of the original chemical bonding under ion implantation leads to the creation of new amorphous and graphite-like structures, which are confirmed by Raman spectroscopy. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:143,151, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20130 [source] Crystallization effects on autoclave foaming of polycarbonate using supercritical carbon dioxideADVANCES IN POLYMER TECHNOLOGY, Issue 4 2006L. Mascia Abstract In this study, the conditions leading to the formation of cells and to the onset of crystallization of polycarbonate were examined with the use of supercritical carbon dioxide for the production of foams from preforms. Small plaques cut from extruded sheets were treated with supercritical carbon dioxide in an autoclave at temperatures varying from 60 to 200°C and from 4.5 to 30 MPa pressure. Visual observations and stereoscan electron microscopy examination revealed that penetration of supercritical carbon dioxide takes place via the advancing layer mechanism and that, for the particular grade of polycarbonate used in this study, the nucleation of the cells can take place at temperatures as low as 60°C. It requires, however, long treatment times and high pressures, and the growth of foam cells is severely restricted. Nucleation and growth of cells occurred much more readily at somewhat higher temperatures. With treatments at around 80°C, the onset of crystallization started to impose considerable hindrance to the formation of uniform and evenly distributed cells. This becomes increasingly evident at higher temperatures, between 100 and 180°C, owing to the formation of large spherulitic crystalline domains. A very effective nucleation and growth mechanism for the formation of cells was obtained, on the other hand, with treatments at 200°C due to the absence of crystallization phenomena. The degree of crystallinity increased with increasing treatment temperature, and the resulting morphology gave rise to two broad melting peaks. These are displaced to higher temperatures and become closer, merging into one peak with a low-temperature shoulder. These events were monitored by thermal analysis and wide-angle X-ray diffraction examinations. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 25:225,235, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20075 [source] Influence of processing conditions on the weld line in doubly injection-molded glassy polycarbonate and polystyrene: Microindentation hardness studyADVANCES IN POLYMER TECHNOLOGY, Issue 1 2005M. Boyanova Abstract The microhardness (H) technique has been used to characterize the quality of the weld line in injection-molded tensile bars from a two-component machine in which both melt streams from the same material can be independently controlled. More specific, the influence of melt temperature and indentation location (closer or further from the sample edge parallel to the injection direction and across the weld line) has been followed on polycarbonate (PC) and polystyrene (PS) glassy samples. For both polymers at lower melt temperatures, a strong H decrease (between 15 and 50%) followed by a sharp increase in a narrow distance (around 0.10 mm), is observed. When the melt temperature increases up to 300°C (for PC) and 270°C (for PS), a much smaller H decrease is observed in the central part of the samples. However, closer to the tensile bar edges (2 mm) the weld line remains undetectable by microhardness measurements. The present results reveal that the processing temperature affects the broadening of the weld line through the conditions for effective mutual interdiffusion of chains from the two fronts coming from opposite sides. © 2005 Wiley Periodicals, Inc. Adv Polym Techn 24:14,20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20028 [source] Synergistic effects of carbon fillers on shielding effectiveness in conductive nylon 6,6- and polycarbonate-based resinsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2003Quinton J. Krueger Abstract Electrically conductive resins can be made by adding electrically conductive fillers to typically insulating polymers. Resins with an electrical resistivity of approximately 100 , cm or less can be used for electromagnetic and radio frequency interference shielding applications. This research focused on performing compounding runs followed by injection molding and shielding effectiveness (SE) testing of carbon filled nylon 6,6- and polycarbonate-based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch-based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 23 factorial design and a complete replicate in each polymer. The objective of this study was to determine the effects and interactions of each filler on the SE properties of the conductive resins. Carbon black caused the largest increase in SE. Also, each single filler and each two filler interaction caused a statistically significant increase in SE. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 96,111, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10040 [source] In-line analysis of the influence of monomeric and oligomeric hindered amine on the hydrolysis of polycarbonate in a PC/ABS blendJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Vipin V. Rajan Abstract The polycarbonate/polyacrylonitrile butadiene styrene (PC/ABS) blends lose mechanical properties when exposed to outdoor conditions. This is due to the ultraviolet (UV) induced photo-oxidation of the PC phase and the polybutadiene portion of the ABS. It is known that ABS can be stabilised against terrestrial light by the use of hindered amine in combination with a UV absorber. However, such hindered amine cannot be used when PC is present in a multi component polymer blend. The hydrolysis of PC is accelerated when a small amount of hindered amine light stabilisers (HALS) is incorporated in the resin and is exposed to elevated temperature. In this article the effect of monomeric and oligomeric hindered amine on the hydrolysis of PC during the compounding of PC/ABS blend in a twin screw extruder at 240°C is observed by means of in-line UV-vis spectroscopy. Tinuvin 765 was used as monomeric hindered amine and Tinuvin 622 as oligomeric hindered amine. The molecular weight of the compounded sample was determined by gel permeation chromatography (GPC) and the rheological properties were observed using an online viscometer. It was found that the extent of hydrolysis induced by the oligomeric hindered amine is less compared to monomeric amine. It was also observed that polymeric hindered amine imparts better dispersion of the ABS phase into the polymer blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Tensile and lignocellulosic properties of Prosopis chilensis natural fabricJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010G. Venkata Reddy Abstract The uniaxial natural fabric Prosopis chilensis was treated with NaOH (alkali), poly (vinyl alcohol) (PVA), and polycarbonate (PC) solutions. The Prosopis chilensis fabric belongs to Leguminosae family. The properties of ligno-cellulosic fabric and the effect of sodium hydroxide (NaOH) treatment were evaluated using thermal analysis by means of thermogravimetric and differential scanning calorimetry analysis, Autonated total reflection-fourier transform infrared spectroscopy, X-ray diffraction (XRD), and field emission scanning electron microscopy. Tensile properties of the untreated and fabric treated with NaOH, PVA, and PC were also studied to assess their performance. The fabric has good thermal resistance on alkali treatment. The FTIR method indicates lowering the hemi cellulose and lignin content by alkali treatment. Further, the XRD studies reveal that crystallinity of the fabric increases on alkali treatment. Tensile properties of the fabric were enhanced on treatments with NaOH, PVA, and PC treatments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Mechanical properties and flammability of polycarbonate alloys containing nanosize additivesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Zhiyi Zhang Abstract Different organic,inorganic composite particles [montmorillonite/poly(butyl acrylate) (PBA)/poly(methyl methacrylate) (PMMA), SiO2/PBA/PMMA, and CaCO3/PBA/PMMA] were synthesized by emulsion polymerization. Furthermore, polycarbonate (PC) alloys were prepared via the doping of these composite particles into PC with a twin-screw extruder. The structure, mechanical properties, and flammability of the PC alloys were studied in detail. Although the tensile modulus of PC decreased a little, the flexibility and impact resistance were improved by the addition of these composite particles. This result was attributed to the fact that the composite particles were well dispersed in the PC matrix, with a cocontinuous phase formed between the particles and PC. In addition, the combustion behavior of the PC alloys, compared with that of the pure PC, resulted from a ceramic-like char that formed on the surface of the PC alloys during burning. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Observations of physical aging in a polycarbonate and acrylonitrile,butadiene,styrene blendJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Jacky K. Y. Tang Abstract The effects of physical aging of a 75 : 25 PC/ABS blend have been studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). From DSC, two distinct peak endotherms at about 90°C and 110°C, which are associated with the glass transition of ABS (Tg,ABS) and PC (Tg,PC) components, respectively, were observed. When progressive aging was monitored at 80°C for over 1000 h, the changes in enthalpic relaxation, glass and fictive temperatures for the blend followed similar trends to those already seen in the literature for PC aged between 125 and 130°C. The rate of enthalpy relaxation was also comparable. The plot of peak endotherm against logarithmic aging time for the PC blend constituent, however, behaved quite differently from the linear relationship known for highly aged PC. The ABS peak component also appeared to be insensitive to aging. Both observations were confirmed to be statistically significant using analysis of variance methods. Using temperature modulated-DSC, there is evidence that aging increases the blend miscibility as the Tg,PC shifts toward the stationary Tg,ABS during aging. Parallel FTIR investigations found oxidation of butadiene during aging to be even at this relatively low temperature, forming hydroxyl and carbonyl degradation products. The presence of ABS in the blend also appeared to have prevented the shifting from the trans-cis to trans-trans arrangement of the carbonate linkage, which is a well-known phenomenon during elevated temperature aging of PC alone. Moreover, the carbonate linkage appears to have been at the lower energy, trans-trans, arrangement prior to the aging process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Modification induced by alpha particle irradiationin Makrofol polycarbonateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008S. A. Nouh Abstract Makrofol DE 1-1 CC polycarbonate samples were exposed to alpha particles of initial energies at levels between 5.1 and 34 MeV. The modifications induced in polycarbonate samples due to the alpha particle irradiation have been studied through different characterization techniques such as X-ray diffraction (XRD), infrared spectroscopy, intrinsic viscosity, and color difference studies. The infrared spectroscopy indicated that the intensities of the characteristic absorption bands decrease with increasing the deposited alpha energy in the range 5.1,8.4 MeV, indicating that the degradation is the dominant mechanism at this range. At the same time, an increase in the OH groups was observed at the same energy range 5.1,8.4 MeV due to the degradation of carbonate group and the H abstraction from the polymer backbone to form hydroxyl groups. The degradation reported by IR spectroscopy enhanced the degree of ordering in the degraded samples as revealed by XRD technique. Additionally, this degradation decreases the intrinsic viscosity from 0.56 to 0.43 at 35°C, indicating a decrease in the average molecular mass. The non irradiated Polycarbonate polymer is nearly colorless. It showed significant darkness sensitivity towards alpha particle irradiation, indicated by an increase in the color intercept L* from 33.6 to 36.7. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Theoretical analysis of the effects of asymmetric membrane structure on fouling during microfiltrationAICHE JOURNAL, Issue 6 2009Weiyi Li Abstract There is a growing interest in the use of both asymmetric and composite membranes for microfiltration and ultrafiltration processes. This includes particle removal applications in the semiconductor industry and virus clearance in biopharmaceutical applications. Filter fouling plays an important role in these processes. Although flux decline models have been developed for homogeneous membranes, the effects of asymmetric membrane structure on flux decline behavior remain poorly understood on a fundamental level. Here, we develop a theoretical model to describe the effects of asymmetric membrane structure on flux decline. The asymmetric structure was described by the spatial variation in Darcy permeability in the directions normal to and parallel to the membrane surface. The velocity profile and flux decline because of pore blockage were described using Darcy's law and a pore blockage and cake filtration model. Flux decline data were obtained using pseudocomposite membranes with highly interconnected polyvinylidene fluoride membranes (PVDF) and straight through pore polycarbonate track-etched membranes (PCTE). Model composite membranes were formed by layering PCTE or PVDF membranes with different pore sizes on top of each other. Flux decline data for the composite membrane were in good agreement with model calculations. The results provide important insights into the effects of asymmetric membrane pore structures on flux decline. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Nonstationary model of the semicontinuous depolymerization of polycarbonateAICHE JOURNAL, Issue 12 2006Raúl Piñero-Hernanz Abstract The experimental work for the depolymerization process of Bisphenol A polycarbonate pellets and CD/DVD wastes in a semicontinuous reactor and a novel nonstationary model to describe the process is presented. The different steps of the process to develop the model are analyzed thoroughly. The kinetics of the alkali-catalyzed methanolysis of polycarbonate was determined. The reactor and kinetic models were validated by a series of 21 experiments performed in a laboratory semicontinuous tubular reactor at isothermal conditions from 90 to 180°C and pressures from 1.0 to 20.0 MPa in liquid phase, with and without NaOH concentrations of 1 × 10,3 to 5 × 10,3 kg/L, flow rates from 2.3 × 10,3 to 10.2 × 10,3 L/min, and CO2 molar fractions from zero to 0.374. The effects of temperature, pressure, catalyst amount, mass transfer (solvent flow rate), and CO2 addition in kinetics were investigated. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Regulation of implant surface cell adhesion: characterization and quantification of S-phase primary osteoblast adhesions on biomimetic nanoscale substratesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2007Manus J.P. Biggs Abstract Integration of an orthopedic prosthesis for bone repair must be associated with osseointegration and implant fixation, an ideal that can be approached via topographical modification of the implant/bone interface. It is thought that osteoblasts use cellular extensions to gather spatial information of the topographical surroundings prior to adhesion formation and cellular flattening. Focal adhesions (FAs) are dynamic structures associated with the actin cytoskeleton that form adhesion plaques of clustered integrin receptors that function in coupling the cell cytoskeleton to the extracellular matrix (ECM). FAs contain structural and signalling molecules crucial to cell adhesion and survival. To investigate the effects of ordered nanotopographies on osteoblast adhesion formation, primary human osteoblasts (HOBs) were cultured on experimental substrates possessing a defined array of nanoscale pits. Nickel shims of controlled nanopit dimension and configuration were fabricated by electron beam lithography and transferred to polycarbonate (PC) discs via injection molding. Nanopits measuring 120 nm diameter and 100 nm in depth with 300 nm center,center spacing were fabricated in three unique geometric conformations: square, hexagonal, and near-square (300 nm spaced pits in square pattern, but with ±50 nm disorder). Immunofluorescent labeling of vinculin allowed HOB adhesion complexes to be visualized and quantified by image software. Perhipheral adhesions as well as those within the perinuclear region were observed, and adhesion length and number were seen to vary on nanopit substrates relative to smooth PC. S-phase cells on experimental substrates were identified with bromodeoxyuridine (BrdU) immunofluorescent detection, allowing adhesion quantification to be conducted on a uniform flattened population of cells within the S-phase of the cell cycle. Findings of this study demonstrate the disruptive effects of ordered nanopits on adhesion formation and the role the conformation of nanofeatures plays in modulating these effects. Highly ordered arrays of nanopits resulted in decreased adhesion formation and a reduction in adhesion length, while introducing a degree of controlled disorder present in near-square arrays, was shown to increase focal adhesion formation and size. HOBs were also shown to be affected morphologicaly by the presence and conformation of nanopits. Ordered arrays affected cellular spreading, and induced an elongated cellular phenotype, indicative of increased motility, while near-square nanopit symmetries induced HOB spreading. It is postulated that nanopits affect osteoblast,substrate adhesion by directly or indirectly affecting adhesion complex formation, a phenomenon dependent on nanopit dimension and conformation. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:273,282, 2007 [source] Nanometer-scale surface modification by polymerization of tetrafluoroethylene on polymer substrates in supercritical fluoroformJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008Toshiaki Mori Abstract Surface penetrated polymerization of tetrafluoroethylene (TFE) was carried out on a polycarbonate (PC) plate in supercritical fluoroform (scCHF3). Since the high diffusiveness is one of peculiar features of supercritical fluids, TFE monomers and initiators (perfluorinated benzoyl peroxide) could penetrate into the surface of polymer substrates and be photo-polymerized. After washing physisorbed homopolymers on the surface, polytetrafluoroethylene (PTFE) was found to penetrate into 50,800 nm depth from the surface and covered the PC surface in the proportion of 85%. The surface coverage density and the penetration depth could be controlled by adjusting of the pressure of scCHF3. The TFE-penetrated polymerization could be applied for various polymer plates such as polyethylene, polystyrene, polypropylene, poly(ethylene terephthalate), and polyimide. In addition to polymer plates, this technique could be applied to a cellulose paper, a nylon textile, and a porous PC membrane. The PTFE-penetrated nylon textile showed a high resistance for washing test with detergents, compared with the commercial fluoropolymer-sprayed nylon textile. The PTFE-penetrated porous PC membrane showed high oxygen permeability (P/P = 5.2), compared with that of the untreated PC membrane (P/P = 3.5) in gas permeation experiments of O2 and N2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1577,1585, 2008 [source] Copolymerization of carbon dioxide and epoxideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2004Hiroshi Sugimoto Abstract An erratum has been published for this article in J Polym Sci Part A: Polym Chem (2005) 43(4) 916. The alternating copolymerization of carbon dioxide and epoxide to produce polycarbonate has attracted the attention of many chemists because it is one of the most promising methodologies for the utilization of carbon dioxide as a safe, clean, and abundant raw material in synthetic chemistry. Recent development of catalysts for alternating copolymerization is based on the rational design of metal complexes, particularly complexes of transition metals with well-defined structures. In this article, the history and recent successful examples of the alternating copolymerization of carbon dioxide and epoxide are described. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5561,5573, 2004 [source] Silicone-based impact modifiers for poly(vinyl chloride), engineering resins, and blendsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2004Akira Yanagase Abstract Silicone-based impact modifiers were prepared in a previous study. The modifiers were composed of silicone/acrylic rubber cores and grafted acrylic shells. They improved the toughness of poly(vinyl chloride) (PVC) and poly(methyl methacrylate). The silicone emulsion that was used to produce the silicone-based impact modifiers was prepared via two routes: emulsion polymerization and bulk polymerization of octamethyltetracyclosiloxane. Many silicone-based impact modifiers were produced that had different silicone/acrylic rubber characteristics. Through a toughness examination of modified PVC, the best composition of the silicone-based impact modifiers was obtained, and the silicone content in the rubber composition was 25 wt %. The morphology of the silicone-based impact modifiers, determined by transmission electron microscopy, was as follows: core and second shell polymers were mainly poly(butyl acrylate), and the first shell polymer was silicone. The silicone-based impact modifiers were blended with engineering resins such as PVC, polycarbonate (PC), poly(butylene terephthalate) (PBT), and PC/PBT mixtures. The impact strength under standard conditions and after weathering test conditions for blends of the silicone-based impact modifiers were investigated with respect to two commercially available acrylic and methyl methacrylate/butadiene/styrene impact modifiers. The results showed good weatherability and good toughness under low-temperature conditions for the silicone-based impact modifiers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1112,1119, 2004 [source] | |||||||||||||||||||||||||||||||