Neat PC Research Articles

Preparation of lightweight polycarbonate composite foams with robust hollow glass microspheres via CO2 foaming

AbstractPolycarbonate (PC) composites are often used in the production of high value‐added products, but it is necessary to improve its environment stress cracking condition in the presence of pre‐strain and soluble solvents. In this work, the effect of weight reduction and strengthening is realized by introducing microstructures and hollow glass microspheres (HGMs) into the PC composites. It is found that the addition of HGMs can reduce the melt viscosity and Tg value of the composite materials, which will change the foaming behavior of PC/HGMs composites. Besides, the effect of different content of HGMS and foaming temperature on the foaming behavior of PC/HGMs composite foams are studied. The PC/HGMs composite foams exhibit a typical structure of both large and small cellular pores, because of the existence of hollow beads and cellular structures. Moreover, compared to the neat PC foam, the tensile strength as well as the flexural strength of the composite foams are significantly increased by 110.9% and 364.7%, respectively. Furthermore, the as‐prepared PC/HGMs composite foams have low thermal conductivity (lower than 0.07 W/mK), which can effectively insulate heat propagation.Highlights Hollow glass microsphere can reduce melt viscosity and Tg of composites. The mechanical properties of composite foams have been greatly improved. Composite foams exhibit excellent thermal stability due to their microstructure.

Energy levels in dilute-donor organic solar cell photocurrent generation: A thienothiophene donor molecule study

To investigate photocurrent generation mechanisms in these organic solar cells (OSCs), we design and synthesize four thienothiophene (TT)-based small-molecule donors with the highest occupied molecular orbital (HOMO) levels varying from −6.4 eV to −5.1 eV, which span across the HOMO value of the [6,6]-phenyl-C70-butyric acid methyl ester (PC 71 BM) acceptor. We measure TT-based donor:PC 71 BM films’ electronic and optical properties, OSC current density-voltage characteristic, and external quantum efficiency, and perform density functional theory (DFT) calculations. Our results show that photocurrent generation depends strongly on the substitutions of the center TT groups, cyano (-CN) versus hexyloxy (-OHex). With 1 wt% donor, TTOHex:PC 71 BM devices produce seven times, increasing to twelve times for 5 wt % donor, higher photocurrent than neat PC 71 BM devices. In contrast, TTCN:PC 71 BM devices do not generate additional photocurrent even with 10 wt% donor. The photocurrent generation in TT-based donor:PC 71 BM devices depends critically on the HOMO value of the donor molecule with respect to that of PC 71 BM, indicating the importance of type II energy level alignment to facilitate exciton dissociation at the donor-acceptor interface. The photovoltage of all TT:PC 71 BM devices are comparable to neat PC 71 BM devices, 0.85–0.90 V, with a low voltage loss due to non-radiative recombination. The fill factor of TTOHex:PC 71 BM devices are low due to the low hole mobility, ~10 −8 cm 2 /V. Following exciton dissociation, hole transport is analyzed according to three possible mechanisms: tunneling, percolation pathways, and hole back transfer. We find that the hole back transfer mechanism can explain all experimental results and therefore is the primary hole transport mechanism for photocurrent generation in TT-based donor:PC 71 BM dilute-donor OSCs. • Design and synthesis of thienothiophene (TT)-based small molecule donors with varied HOMO levels. • Functional group substitutions on center TT groups have stronger effect on energy levels and photocurrent generation. • Favorable HOMO offset between donor and acceptor is required for exciton dissociation. • Hole back transfer is the primary hole transport mechanism for photocurrent generation in the TT:PCBM dilute-donor devices.

Novel polycarbonate membrane embedded with multi-walled carbon nanotube for water treatment: a comparative study between bovine serum albumin and humic acid removal

Flat sheet polycarbonate/multi-walled carbon nanotube (PC/MWCNT) nanocomposite membranes with different nanoparticle contents were prepared by applying the phase inversion method. The characteristics of the prepared membranes were analyzed by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), water contact angle, porosity, pure water flux (PWF), and mechanical properties. The performance of the membranes was evaluated in a submerged membrane system for two cycles and also for the filtration of humic acid (HA) and bovine serum albumin (BSA). The obtained results revealed that nanocomposites containing 0.1 wt% of MWCNTs showed better hydrophilicity, porosity, PWF, and mechanical properties. The FE-SEM images from surface indicated that the density and pore size of membrane increased from 0 to 0.1 wt% of MWCNTs. Moreover, according to AFM images, the PC/MWCNT-0.1 membrane showed a smoother surface than other samples. The antifouling performance of the membranes in a submerged membrane system revealed that the BSA solution flux for all membranes was lower than that of the HA solution due to the pore blocking of membranes occurring in the initial filtration of BSA. Apart from that addition of the 0.1 wt% of MWCNTs led to significant improvement in the fouling recovery ratio in the filtration of both HA and BSA because of the lower roughness and high hydrophilicity of the membrane surface. The rejection results revealed that the neat PC membrane had the highest value in the removal of HA and BSA with respect to other samples due to the formation of a thicker and denser cake layer on the membrane surface.

A Zr-based metal organic frameworks towards improving fire safety and thermal stability of polycarbonate

Zr-based metal organic frameworks (Zr-BDC) with high porosity were synthesized by a solvothermal method and then compounded with polycarbonate (PC, one of the most important engineering plastic) to reduce the fire hazard and improve the thermal stability of PC. It was found that Zr-BDC could prolong the time to ignition (TTI) and time to peak of heat release rate (t-PHRR) of PC up to 90 and 75 s, respectively. Compared with the neat PC, 2 wt% Zr-BDC could increase the temperature at the maximum degradation rate (Tmax) of PC in N2 atmosphere by 33 °C; 4 wt% Zr-BDC reduced the values of peak heat release rate (PHRR) and total smoke release (TSR) by 48% and 34%, respectively. Moreover, only 4 wt% Zr-BDC made the composites reach UL-94 V-0 rating in vertical burning test. Unsaturated Zr metal site made Zr-BDC have activity in catalytic oxidation, isomerization reactions etc., which imparted it the ability to catalyze char formation (cross-linking) in the degradation process of PC matrix, therefore more compact, and highly graphitized char layers were obtained.

Evaluation of Structures and Morphologies of Recycled PC/PET Blends Fabricated by High-Shear Kneading Processing

Abstract We fabricated polymer blends of recycled-PC (PC) and recycled-PET (PET) using high-shear processing technology. We also assessed its structure, morphology, and physical properties. Results of DSC measurements show that Tg of PC and Tc of PET shifted to higher temperatures by kneading under high-shear conditions. Results show further that the Tm of PET shifted to a lower temperature. Moreover, compatibilization progressed. TEM observations show that the PET domain was not confirmed completely under the kneading condition of 1 000 min−1/10 s or more. Compatibilization progressed. Tensile test results show that the PET ratio of 30 wt% (1 000 min−1/10 s) has higher breaking strain than neat PC does. Chemical resistance test results obtained by good solvent of PC demonstrated that blending of PET makes PC elution difficult.

Residual charge and filtration efficiency of polycarbonate fibrous membranes prepared by electrospinning

ABSTRACTPolycarbonate (PC) ultrafine fiber membranes with benzyl triethylammonium chloride (BTEAC) were prepared by electrospinning of PC/chloroform solution with different BTEAC contents. In the presence of BTEAC additive, the PC solution showed a better electrospinnability and led to thinner fibers with uniformity than the neat PC solution. The charge retention of the electrospun PC fibrous membranes with BTEAC was investigated in terms of additive content, membrane thickness and storage condition. The residual charge on the PC fibrous membrane was increased to 1 wt % BTEAC content, but thereafter gradually decreased up to 10 wt % BTEAC. In addition, the residual charge on the membrane was increased with increasing the membrane thickness, but was rapidly decreased at a high humidity condition in comparison with a low humidity. The filtration efficiency was examined for the fibrous membranes with or without BTEAC. The PC membrane with BTEAC had higher filtration efficiency than one without BTEAC, not affecting the pressure drop. The filtration efficiency between the PC membranes with or without residual charge was also compared. When the residual charge existed on the membrane, the membrane showed higher filter efficiency because of the enhanced filtration effect by an electrostatic attraction. Therefore, the PC fibrous membranes with BTEAC have a great potential as an electrets filter for air filtration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41340.

Effect of calcium aluminate cement variety on the hydration of portland cement in blended system

Two kinds of CACs with different monocalcium aluminate (CA) contents were used in the PC/CAC (PAC) mixtures. Effects of CA and CACs on the properties of PAC were analyzed by setting times and the compressive strength tests, and also by means of calorimetry, XRD, DTA-TG and ESEM. The experimental results show that the compressive strength of the PAC mortars decreases with increasing content of CAC while it declines sharply with a higher content of CA in CAC. Compared with neat PC paste, the content of calcium hydroxide in hydrates of PAC paste decreases significantly, and the hydration time of PC is prominently prolonged. Additionally, the higher the content of CA in CAC, the more obviously the hydration of PC is delayed, confirming that the CA phase in CAC plays an important role in the delay of PC hydration.

Thermal degradation mechanism and kinetics of polycarbonate/silica nanocomposites

Polycarbonate nanocomposites filled with pristine and modified silica were prepared by simple melt compounding. The thermal degradation behavior of composites was investigated by thermogravimetric analysis coupled with differential scanning calorimetry (TGA/DSC). To understand the thermal degradation mechanism, the chemical structures of gaseous and solid degradation products were detected by thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TGA/FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods were employed to analyze the thermal degradation kinetics. High thermal degradation temperature was obtained by incorporating both types of nanoparticles into matrix, but the maximum mass loss rate increased. According to the DSC curves for degradation process, the change of the number and position of absorption peaks meant that the degradation mechanism of composites was different from that of neat PC. The analysis for TGA chars confirmed the presence of alcoholysis reaction between PC and silica nanoparticles during the thermal decomposition. TGA/FTIR results proved that no new degradation volatiles were produced during the thermal degradation of composites, but the total amounts of all gaseous products decreased by adding silica nanoparticles. The degradation activation energies of both composites increased significantly relative to neat PC, especially for the composite with modified silica.

Tetramethylammonium difluoro(oxalato)borate dissolved in ethylene/propylene carbonates as electrolytes for electrochemical capacitors

Tetramethyl ammonium difluoro(oxalato)borate (TMADFOB) dissolved in the mixed solvents of ethylene and propylene carbonates (EC/PC) instead of neat PC have been proposed as the electrolyte solutions for electrochemical capacitors. The ionic conductivity of 1 M TMADFOB-EC/PC electrolyte solutions has been measured. It climbs up monotonously as EC content increases. Accordingly, the power density of electric double-layer capacitors is enhanced with certain EC addition. The optimum EC content for the power of EDLCs is about 30 volume percentage in the mixed EC/PC solvents. This tendency has been testified by impedance study. The electrochemical behavior of activated carbon/graphite capacitors using these electrolyte solutions has also been studied by galvanostatic charge–discharge test and the charge storage mechanism at the graphite positive electrode has been investigated by in situ XRD and ex situ Raman. The effect of EC addition on DFOB− intercalation into graphite has also been addressed at both room and elevated temperatures.

In vitro evaluation of UHMWPE/zirconia composite using human peripheral blood mononuclear cells

The objective of the present study was to investigate in vitro biocompatibility of ultra high molecular weight polyethylene (UHMWPE)/zirconia-polymerized composite (PC) using human peripheral blood mononuclear cells (PBMCs). This study was undertaken to compare the levels of free radical generations for neat UHMWPE and PC through irradiation sterilization, and their response to PBMCs viability. Electron spin resonance (ESR) studies showed that γ-ray irradiation of the samples generated free radicals; the extent was inversely related to zirconia content, and the free radicals strongly influenced cell viability. DNA fragmentation and DAPI staining assays revealed that cell death was associated with the induction of apoptosis. Flow cytometry also showed that cell death was largely dependent upon both early and late apoptosis, and, importantly, oxidized PC (ox-PC) exhibited a significantly lower rate for late apoptosis compared to that of oxidized UHMWPE (ox-UHMWPE). Open image in new window

Thermal Conductivity and Mechanical Properties of Wood Sawdust/Polycarbonate Composites

Wood sawdust was increasingly being used as reinforcement in commercial thermoplastics due to low cost, reusable raw materials. One of the problems of using wood sawdust is its interfacial adhesion with polymeric matrix. In this research, two types of silane coupling agents (N-(3-Trimethoxysilylpropyl) diethyllenetriamine and γ-aminopropyl trimethoxy silane) and sodium hydroxide were used for the modification of interfacial adhesion in wood sawdust/polycarbonate composites. The effects of chemical treatment and wood sawdust content (10, 20 and 30 % by wt) were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), thermal conductivity analysis. Youngs modulus of composites was in general higher than the neat PC except for the one with γ-aminopropyl trimethoxy silane treatment. Tensile modulus of composites was increased as the filler loading increased. Nevertheless, the addition of wood sawdust resulted in the tensile strength reduction of the composites. The SEM micrographs reveal that the aggregation of wood particles and weak interfacial bond between the treated wood sawdust and the polymeric matrix with increasing filler loading. Furthermore, the thermal conductivity was reduced significantly with the increment of wood sawdust contents.

Dramatic Effects of Scalable SNN‐Assisted Melt Dispersion on Thermal Conductivity and Coefficient of Thermal Expansion of Nanocomposites

AbstractIt is demonstrated that SNN‐assisted melt dispersion can lead to a significant improvement of the thermal conductivity of PC/MWCNT composites accompanied by a dramatic reduction in their linear CTE. The thermal conductivity of the SNN‐containing composites after the 2‐step process was about 95% higher than that of neat PC and 25% higher than that from 1‐step processing at same loading. The CTE below the glass‐transition temperature of composites with a 1.0 wt.‐% MWCNT loading is substantially reduced compared to the neat polymer. A reduction in the CTE of up to 60.8% is observed for composites from the 2‐step process. Simultaneous achievement of high thermal conductivity and low CTE is required for electronic packaging in microelectronics for device protection. magnified image

Heterogeneous nucleation uniformizing cell size distribution in microcellular nanocomposites foams

Microcellular polycarbonate/nano-silica nanocomposites (PCSN) were prepared by temperature rising process using supercritical CO 2 as the blowing agent. Neat PC foam showed a quite broad distribution of cell sizes. Under the same foaming conditions, the addition of nano-silica resulted in PCSN foams having uniform cell size distribution, reduced cell size of 0.3–0.5 μm and increased cell density of 10 11–10 13 cells/cm 3. The underlying nucleation mechanism was semi-quantitatively analyzed by the classical nucleation theory. The results indicate that the energy-barrier for heterogeneous nucleation was three orders of magnitude lower than that of homogeneous one. The heterogeneous nucleation of nano-silica aggregates dramatically increased the nucleation rate, decreased the nucleation time interval, and hence facilitated the almost instantaneous growth of cell size. Combined with the well-dispersed nucleation sites, resulted from the uniform dispersion of nano-silica aggregates, the narrow-distributed cell size was obtained in PCSN foams.

多価フェノール共沈化合物添加によるポリカーボネートの熱安定効果

The thermal stability and recyclability of polycarbonate resin (PC) composites filled with coprecipitated polyhydric phenol/polyethylene glycol (CGP) have been investigated. The composites were evaluated after 4 repeated molding. For the composites containing 0.02wt% polyhydric phenol CGP, the number-average molecular weight (Mn) of PC in the composites, measured by gel permeation chromatography, decreased from 24300 to 22100 after 4 injection molding cycles while the unfilled PC resin control decreased to 21000. These results suggest that the PC molecule depolymerized during the injection molding process due to the thermal energy and stress. On the other hand, we found that the CGP reduced the increase in PC Izod impact strength to 120% that of the neat PC resin. In addition, we studied the effects of the addition of a coprecipitate of polyhydric phenol with polyethylene glycol at levels of 0.02 to 0.03wt%. The glass transition temperatures (Tg) of the composites were evaluated by dynamic viscoelastometry. Using the Fox equation to examine the Tg-Mn-1 plots of these PC composites, it was observed that these results were different from those expected for particle dispersed PC composites.These findings suggest that the addition of polyhydric phenol/polyethylene glycol coprecipitation compounds in PC improved the stability of PC. This implies that added coprecipitation compounds may be an effective method in the recycle of PC resin.

多段表面処理シリカ粒子添加によるポリカーボネート複合系の熱安定効果と衝撃強度の向上

The thermal stability and recyclability of Polycarbonate resin (PC) composites filled with silica particles which are surface-treated with polyhydric phenol agents has been investigated. The composites were evaluated after molding 4 consecutive times. For the composites containing 1.5wt% silica particles treated with polyhydric phenol, the number-average molecular weight (Mn) of PC in the composites, measured by gel permeation chromatography, decreased from 24300 to 21800 after 4 injection molding cycles, while the unfilled PC resin control decreased to 21000.These results suggest that the PC molecule depolymerized during the injection molding process due to the thermal energy and stress. On the other hand, we found that the surface treatment of silica particles with polyhydric phenol reduced the decrease in PC Izod impact strength to 1/5 that of the neat PC resin. In addition, we studied the effects of multistage surface treatment of silica particles using two phases and three phases with benzophenone, silane-coupling agents. Three phase multistage treated silica particles resulted in higher Mn retention than those containing a single phase with polyhydric phenol.The magnitude of the activation energies (ΔE) related to the thermal degradation of the composites were evaluated by thermo-gravimetry. ΔE increased in the following order: neat PC, composite with the two-phase multistage and that with the three-phase multistage.These findings suggest that the addition of multistage surface-treated particles in PC improved the stability of PC composites. This implies that surface treatment may be an effective method in the recycle of PC resin composites.

Bisphenol‐A polycarbonate/polydimethylsiloxane multiblock copolymers. II. Effects of siloxane oligomer structure on the properties of copolymers

Polycarbonate-polydimethylsiloxane (PDMS) copolymers were synthesized by interfacial phosgenation of 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A) with different types of PDMS oligomers including α,o-amino-organofunctional polydimethylsiloxane (AT-PDMS oligomer), α,o-hydroxy-organofunctional polydimethylsiloxane (HT-PDMS oligomer), and α,o-phenol-organofunctional polydimethylsiloxane (PT-PDMS oligomer). 1H-NMR spectra indicated the conversion of AT-PDMS-PC copolymer was in the range between 85 and 95%, HT-PDMS-PC was 45–55%, and PT-PDMS-PC was 70–80%. It was found that the intrinsic viscosity of PDMS-PC copolymers decreased with increasing PT-PDMS oligomer content. The intrinsic viscosity, IV, also decreased with increasing cumylphenol content. The melt indices of PDMS-PC copolymers blended with neat PC increased with increasing PDMS-PC content and the copolymers showed good processability. Izod impact strength of PDMS-PC copolymer was improved while retaining tensile and flexural strengths of neat PC. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 67–75, 1997

Bisphenol-A polycarbonate/polydimethylsiloxane multiblock copolymers. II. Effects of siloxane oligomer structure on the properties of copolymers

Polycarbonate-polydimethylsiloxane (PDMS) copolymers were synthesized by interfacial phosgenation of 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A) with different types of PDMS oligomers including α,o-amino-organofunctional polydimethylsiloxane (AT-PDMS oligomer), α,o-hydroxy-organofunctional polydimethylsiloxane (HT-PDMS oligomer), and α,o-phenol-organofunctional polydimethylsiloxane (PT-PDMS oligomer). 1H-NMR spectra indicated the conversion of AT-PDMS-PC copolymer was in the range between 85 and 95%, HT-PDMS-PC was 45–55%, and PT-PDMS-PC was 70–80%. It was found that the intrinsic viscosity of PDMS-PC copolymers decreased with increasing PT-PDMS oligomer content. The intrinsic viscosity, IV, also decreased with increasing cumylphenol content. The melt indices of PDMS-PC copolymers blended with neat PC increased with increasing PDMS-PC content and the copolymers showed good processability. Izod impact strength of PDMS-PC copolymer was improved while retaining tensile and flexural strengths of neat PC. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 67–75, 1997

アロイ・ブレンド・コンポジットの成形加工 表面処理ゼオライト／ポリカーボネート複合系の動的粘弾性

The effects of surface treatment using four kinds of coupling agents for clinoptilolite-type zeolite powder have been investigated in zeolite/polycarbonate (PC) composites. The composites were prepared by mixing the surface-treated zeolite powder with PC using a plastometer at 280°C. The number-average molecular weight (Mn) of PC, measured by gel permeation chromatography, decreased from 24300 to 13300 with the addition of untreated zeolite. The magnitude of the storage modulus (E′) and the glass transition temperature (Tg) of the composite evaluated by dynamic viscoelastometry decreased with decreasing molecular weight of PC.The PC polymer is depolymerized during the mixing process due to the acid catalysis of zeolite. In composites where the zeolite was surface-treated with silane coupling agents with epoxygroups and polyphenol, the Mn of PC only decreased to 20700 and 22100, respectively. The E′ and Tg of the composites containing these surface-treated zeolites were larger than those of the neat PC. The coupling agents prevented the acid catalysis of zeolite powder, thus the surface-treatment of zeolites are effective in the reinforcement of composites.