Showing papers on "Polycarbonate published in 2007"

A complex plane analysis of α‐dispersions in some polymer systems

Abstract: The α-dispersion in many polymer systems is the process to be associated with the glass transition temperature where many physical properties undergo drastic changes. We have measured and analyzed the complex dielectric behavior of the α-dispersions for five polymers [i.e., polycarbonate and polyisophthalate esters of bisphenol A, isotactic poly-(methyl methacrylate), poly(methyl acrylate), and a copolymer of phenyl methacrylate and acrylonitrile] and have found that the usual methods of analysis cannot be used to represent the data. However, it is possible to represent the relaxation process as the sum of two dispersions but there is no evidence to support this contention. An empirical expression is proposed to represent the data. This expression which takes the form of appears to be a general representation for the three known dispersions, i.e., Debye, circular arc, and skewed semicircle. The complex dielectric constants calculated with the aid of this expression and the parameters for each polymer system which was determined graphically were found to be in excellent agreement with the experimental complex dielectric constants. This method of representation was extended to sixteen α-dispersions reported in the literature always with excellent results.

Polycarbonate compositions and articles formed therefrom

Abstract: A polycarbonate composition is disclosed having zero or minimum halogen content, while also exhibiting improved fire-retardance and/or drip-resistant characteristics. The composition comprises an effective amount of a polycarbonate, an anti-dripping agent, an aromatic sulfone sulfonate, an aromatic sulfonate, a synergistic combination of an elastomer-modified graft copolymer and a polysiloxane-polycarbonate copolymer, and an optional siloxane oligomer. The polycarbonate composition is useful for manufacture of electronic and mechanical articles, among others.

Nanocomposites of Polyhedral Oligomeric Phenethylsilsesquioxanes and Poly(bisphenol A carbonate) as Investigated by Dielectric Spectroscopy

Abstract: Nanocomposites were prepared by solution blending of polyhedral oligomeric silsesquioxane with phenethyl substituents (PhenethylPOSS) into poly(bisphenol A carbonate) (PBAC). The nanocomposites were investigated by dielectric spectroscopy, differential scanning calorimetry (DSC) and density measurements. PhenethylPOSS shows one relaxation process, the α-relaxation, confirmed by DSC investigations. PBAC shows a β-relaxation at lower and an α-relaxation at higher temperatures. With increasing PhenethylPOSS content the α-relaxation of the composites shifts to lower temperatures. Thus, incorporation of PhenethylPOSS leads to a plasticization of PBAC due to a decrease of the packing density which is rationalized by density measurements. For higher concentrations of PhenethylPOSS (>10 wt %) the α-relaxation of the polycarbonate matrix splits into two peaks. Moreover, close to the α-relaxation of PhenethylPOSS a third process is observed. These results indicate a phase separation into a PBAC matrix with a few pe...

Flame retardant and scratch resistant thermoplastic polycarbonate compositions

Abstract: A flame retardant thermoplastic composition comprising in combination a polycarbonate homopolymer or copolymer comprising repeat carbonate units having the following structure: (I) wherein R1 and R2 are independently at each occurrence a C1 -C4 alkyl, n and p are each an integer having a value of 1 to 4, and T is selected from the group consisting of C5-C10 cycloalkanes attached to the aryl groups at one or two carbons, C1-C5 alkyl groups, C6-C13 aryl groups, and C7-C12 aryl alkyl groups; an impact modifier, wherein the impact modifier comprises wherein the impact modifier comprises a rubber modified thermoplastic resin comprising a discontinuous elastomeric phase dispersed in a rigid thermoplastic phase, and wherein the impact modifier has a specific mean particle size and Q value; and a flame retardant. The compositions have excellent scratch resistance as well as an improved balance of physical properties such as impact strength and spiral flow, while at the same time maintaining their good flame performance.

Role of Specific Interactions and Solubility in the Reinforcement of Bisphenol A Polymers with Polyhedral Oligomeric Silsesquioxanes

Abstract: Polycarbonate (PC) and phenoxy resin (PKFE) have similar structures derived from bisphenol A. PKFE resin possesses pendant hydroxyl groups along its backbone; instead of the carbonate carbonyl groups found in polycarbonate, PKFE contains 2-hydroxypropyl groups instead. This difference in structure significantly influences thermomechanical properties when these materials are blended with phenyltrisilanol polyhedral oligomeric silsesquioxanes (POSS). While POSS exhibits some level of solubility in the each of the polymer matrixes tested, the glass transition temperatures of phenoxy composites increase with incorporation of POSS, while the glass transition temperatures of polycarbonate composites decrease significantly. Addition of POSS to PC also results in embrittlement of the composites; POSS thus serves as an antiplasticizer in the PC/POSS system. In the case of PKFE/POSS composites, significant interactions are evidenced by the change in the shape of the infrared spectra for the C−H phenyl stretch. Whil...

Controlled nanostructure and high loading of single-walled carbon nanotubes reinforced polycarbonate composite

Abstract: This paper presents an effective technique to fabricate thermoplastic nanocomposites with high loading of well-dispersed single-walled carbon nanotubes (SWNTs). SWNT membranes were made from a multi-step dispersion and filtration method, and then impregnated with polycarbonate solution to make thermoplastic nanocomposites. High loading of nanotubes was achieved by controlling the viscosity of polycarbonate solution. SEM and AFM characterization results revealed the controlled nanostructure in the resultant nanocomposites. Dynamic mechanical property tests indicated that the storage modulus of the resulting nanocomposites at 20 wt% nanotubes loading was improved by a factor of 3.4 compared with neat polycarbonate material. These results suggest the developed approach is an effective way to fabricate thermoplastic nanocomposites with good dispersion and high SWNT loading.

UV curing of organic–inorganic hybrid coating materials

Abstract: The effect of UV-curing time on the mechanism of interaction between the various precursor phases in a novel sol–gel-derived organic–inorganic hybrid coating material and the resulting mechanical and thermal properties of this material when coated onto substrates in thin film form have been examined using a variety of chemical and physical characterisation methods. Microstructurally, the hybrid coating materials examined were all a single amorphous phase and were all optically transparent. The degree of interaction between the organic and inorganic phases, the scratch behaviour of the coating materials and the thermal stability of the coating materials were all found to depend strongly on the UV curing time. For the particular proportions of inorganic and organic components used to make up this hybrid coating material, an optimum UV curing time of 10 min under a UV intensity of 46.3 mW cm−2 was found to produce transparent coatings which adhered well to the substrates and which were robust in scratch tests on aluminium and polycarbonate substrates and abrasion tests on polycarbonate substrates.

Thermoplastic resin composition and molded article thereof

Abstract: Disclosed is a thermoplastic resin composition excellent in fluidity and mechanical characteristics. A preferred embodiment of this thermoplastic resin composition is also excellent in low warping property, laser transmission and laser weldability. Also disclosed is a molded article of such a thermoplastic resin composition. Specifically disclosed is a thermoplastic resin composition obtained by blending 0.1-4 parts by weight of a multifunctional compound (B) having three or more functional groups, wherein at least one terminal structure having a functional group includes an alkylene oxide unit, per 100 parts by weight of a thermoplastic resin (A). The thermoplastic resin (A) is preferably composed of one or more resins selected from polyester resins and polycarbonate resins. Also specifically disclosed is a molded article of such a thermoplastic resin composition.

Synthesis and Chemical, Physical, and Optical Properties of 9,9-Diarylfluorene-Based Poly(ether−ether−ketone)

Abstract: Fluorene-based poly(ether−ether−ketone) (F-PEEK) was designed and synthesized by reacting a 9,9-diarylfluorene-containing biphenol and a naphthalene-containing dihaloarene. High molecular weight F-PEEK (Mw > 270 000; Mn ∼ 55 000) was obtained in quantitative yields by the two-step polycondensation of 9,9-bis(4-hydroxy-3-methylphenyl)fluorene and 1,5-bis(4-fluorobenzoyl)-2,6-dimethylnaphthalene in the presence of cesium carbonate in diphenyl sulfone at 165 °C and then 220 °C. The chemical, physical, and optical properties of F-PEEK were evaluated. Good solubility of F-PEEK in ordinary organic solvents such as THF and chloroform was confirmed. F-PEEK exhibited a high refractive index of 1.64 at 589 nm, whereas it showed a much lower birefringence value than a polycarbonate or a polyester. F-PEEK was amorphous and transparent at room temperature. The transmittance of F-PEEK in film state was over 80% in the visible region. These optical properties were probably related to the cardo structure of the fluorene ...

Effect of nanoparticle size and size-distribution on mechanical behavior of filled amorphous thermoplastic polymers

Abstract: Different types of polymer nanocomposites on the base of polystyrene, polymethylmethacrylate, and polycarbonate with alumina and SiO2 nanoparticles and carbon nanotubes have been studied. Miniaturized, microdimensional samples were used, enabling a good control of morphology and distribution of particles by means of transmission and scanning electron microscopy. Special preparation techniques had been applied, which resulted in a very good dispersion of the nanoparticles. Using these materials with really nanosized particles of a few 10nm in size the effect on toughness enhancement could be studied without agglomerates as they often appear in the generally used large samples. Micromechanical mechanisms were studied in detail by TEM and SEM investigations of deformed samples. A “nanoparticle modulated crazing” could be detected as a toughness enhancing effect. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Preparation and Rheological Characterization of Polymer Nanocomposites Based on Expanded Graphite

Abstract: A new type of conductive filler, namely expanded graphite (EG), was used to prepare novel nanocomposites. The EG was incorporated into several rather different polymers, specifically polycarbonate (PC), low‐density polyethylene (LDPE), isotactic polypropylene (PP), and polystyrene (PS), using melt mixing in a small‐scale DACA‐Microcompounder. The EG content was varied between 1 and 20 wt%. The rheological properties and morphologies of the nanocomposites were characterized by melt rheology and scanning electron microscopy (SEM), respectively. The melt‐state linear viscoelastic properties were investigated using an ARES rheometer, with the measurements performed in the dynamic mode at various temperatures over a wide range of frequencies. Addition of the EG increased the linear dynamic moduli and melt viscosity of the materials. Up to a certain critical concentration of EG, the materials exhibited a simple liquid‐like behavior. Above this concentration, however, significant changes in the frequency depende...

Thermoplastic resin composition

Abstract: PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition having excellent rigidity and thermal stability and also having excellent heat conductivity. SOLUTION: The resin composition comprises total 100 pts.wt. of 47-98.97 pts.wt. of thermoplastic resin (component A), 1-50 pts.wt. of graphite (component B) having ≤50 μm particle diameter in the composition, and 0.03-3 pts.wt. of an acidic group-containing organic compound. Preferably, the thermoplastic resin (component A) contains ≥50% polycarbonate resin, and the thermoplastic resin composition further contains one or more kinds selected from the group consisting of a phosphorus-based stabilizer (component D), a flame retardant (component E) and a fluorine-containing drip inhibitor (component F) besides them. The acidic group-containing organic compound is preferably an olefin-based wax having a carboxy group and/or an acid anhydride group thereof. COPYRIGHT: (C)2007,JPO&INPIT

Suzuki polycondensation put to work: a tough poly(meta-phenylene) with a high glass-transition temperature.

Abstract: Challenging commercial polycarbonate: Suzuki polycondensation afforded a high-molar-mass poly(meta-phenylene) (see structure) which displays not only outstanding toughness, convenient processability, and a high glass-transition temperature, but also considerable resistance against environmental stress-cracking; thus, it rivals high-performance polycarbonate in its fundamental properties.

Deformation and orientation during shear and elongation of a polycarbonate/carbon nanotubes composite in the melt

Abstract: In this study, we focused on the elongational rheology and the morphology of an electrically conductive polycarbonate/multiwalled carbon nanotubes (2 wt%) composite in the melt. In shear and melt elongation, the influence of the carbon nanotubes was large when the externally applied stress was small. Consequently, the elastic interactions resulting from the carbon nanotubes dominated in the low frequency range of the shear oscillations. The elongational viscosity of the composite was only moderately influenced by the addition of 2 wt% carbon nanotubes. Transmission electron microscopy investigations of the stretched composite showed that isolated carbon nanotubes were oriented in elongation. In recovery after melt elongation, the recovered stretch of the composite was much smaller than the recovered stretch of pure polycarbonate. This effect is caused by the carbon nanotubes network, which prohibited large extensions of the macromolecules and led to a yield stress of the composite.

Nanowear on polymer films of different architecture.

Abstract: In this paper, we describe atomic force microscope (AFM) friction experiments on different polymers. The aim was to analyze the influence of the physical architecture of the polymer on the degree and mode of wear and on the wear mode. Experiments were carried out with (1) linear polystyrene (PS) and cycloolefinic copolymers of ethylene and norbornene, which are stabilized by entanglements, (2) mechanically stretched PS, (3) polyisoprene-b-polystyrene diblock copolymers, with varying composition, (4) brush polymers consisting of a poly(methyl methacrylate) (PMMA) backbone and PS side chains, (5) PMMA and PS brushes grafted from a silicon wafer, (6) plasma-polymerized PS, and (7) chemically cross-linked polycarbonate. For linear polymers, wear depends critically on the orientation of the chains with respect to the scan direction. With increasing cross-link density, wear was reduced and ripple formation was suppressed. The cross-linking density was the dominating material parameter characterizing wear.

Influence of long-chain branching on the crystallization and melting behavior of polycarbonates in supercritical CO2

Abstract: The crystallization behavior of two long-chain branched bisphenol A polycarbonates (PC-Bs) was studied in supercritical CO2 using differential scanning calorimetry (DSC), wide-angle X-diffraction, and atomic force microscopy (AFM), with a linear polycarbonate (PC-L) as reference. All the PCs had similar molecular weights and molecular weight distributions. Positron annihilation lifetime spectroscopy measurement indicated that the increase in free volume fraction of 13.1% (PC-B1) and 11.8% (PC-B2) was obtained with incorporating long-chain branches compared to PC-L. This increased segmental mobility decreased the energy barrier for PC crystallization and hence increased the crystallization kinetics for PC-Bs. Two melting peaks (Tm1 and Tm2) observed during DSC heating scan were associated with the melting of secondary and primary crystallization, respectively. The Tm2 of PC-Bs was about 2−4 °C lower than that of PC-L of at the same treatment time, pressure, and temperature. These results, qualitatively con...

Role of Processing Temperature in Polystyrene and Polycarbonate Foaming with Carbon Dioxide

Abstract: This paper examines the effect of processing temperature on polystyrene (PS)/CO2 and polycarbonate (PC)/CO2 polymeric foaming systems. Using in situ visualization data from batch foaming experiments, plastic foam characteristics including cell density and average cell size at different processing temperatures were analyzed. These results were compared with those generated by computer simulation, and satisfactory agreements between the two were observed. It was found that the maximum cell densities in the PS/CO2 foaming system were higher at lower processing temperatures. For processing temperatures above the melting temperature of PC, a similar, but less significant, relationship between the maximum cell densities and temperature was observed for the PC/CO2 system.

Some aspects of vapor‐induced crystallization of polycarbonate of bisphenol A

Abstract: A method is presented to crystallize polycarbonate of bisphenol A under constant vapor pressure of solvents at near ambient temperatures. Methylene chloride and acetone were used as crystallizing liquids. Acetone is more powerful in inducing crystallization but the final degree of crystallinity does not depend on the nature of the solvent. The crystalline degree is low as found in the literature for this polymer. This method is very useful to crystallize materials reluctant to thermally induced crystallization such as polycarbonate.

Reactive extrusion of recycled poly(ethylene terephthalate) with polycarbonate by addition of chain extender

Abstract: Poly(ethylene terephthalate) (PET) resin is one of the most widely used engineering plastic with high performance, but the poor impact strength limits its applications for the notch sensitivity. In this research, toughened PET alloy was prepared by blending recycled PET with polycarbonate (PC) and MDI (methylenediphenyl diisocyanate). Intrinsic viscosity and melt viscosity measurements proved increase of the molecular weights of PET via chain-extending reaction. FTIR and DMA results proved that some PET–PC copolymers were produced and the compatibility of PET phase and PC phase was improved. In addition, the reaction induced by MDI also affected the crystallization behaviors of PET, as observed from DSC results, and the crytallinity of PET decreased with the increase of MDI content. For all of these effects of MDI of increasing of molecular weight, improving of compatibility, and limiting the crystallization behaviors of PET/PC alloy, the notched-impact strength was greatly improved from 17.3 to 70.5 kJ/m2. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2602–2607, 2007

Polycarbonate Resin Composition with Good Flame Retardancy and Light Stability

Abstract: Disclosed herein is a polycarbonate resin composition having good flame retardancy and light stability which can be useful for a LCD backlight component comprising: about 60 to about 95 parts by weight of a thermoplastic polycarbonate resin, and about 5 to about 40 parts by weight of a polyethylene naphthalate-terephthalate copolymer, about 5 to about 50 parts by weight of titanium dioxide based on about 100 parts by weight of a base resin comprising the thermoplastic polycarbonate resin and the polyethylene naphthalate-terephthalate copolymer, about 0.1 to about 10 parts by weight of an organosiloxane polymer based on about 100 parts by weight of a base resin comprising the thermoplastic polycarbonate resin and the polyethylene naphthalate-terephthalate copolymer, and about 0.05 to about 5 parts by weight of a fluorinated polyolefin resin based on about 100 parts by weight of a base resin comprising the thermoplastic polycarbonate resin and the polyethylene naphthalate-terephthalate copolymer.

How did we find the rigid amorphous phase

Abstract: The first experimental evidence of the existence of the rigid amorphous phase was reported by Menczel and Wunderlich [1]: when trying to clarify the glass transition characteristics of the first main chain liquid crystalline polymers [poly(ethylene terephthalate-co-p-oxybenzoate) with 60 and 80 mol% ethylene terephthalate units] [2], the absence of the hysteresis peak at the lower temperature glass transition became evident when the sample of this copolymer was heated much faster than it had previously been cooled. Since this glass transition involved the ethylene terephthalate-rich segments of the copolymer, we searched for the source of the absence of the hysteresis peak in PET. There, the gradual disappearance of the hysteresis peak with increasing crystallinity was confirmed [1]. At the same time it was noted that the higher crystallinity samples showed a much smaller ΔC p than could be expected on the basis of the crystallinity calculated from the heat of fusion (provided that the crystallinity concept works). Later it was confirmed that the hysteresis peak is also missing at the glass transition of nematic glasses of polymers. When checking other semicrystalline polymers, the sum of the amorphous content calculated from the ΔC p at the glass transition, and the crystallinity calculated from the heat of fusion was far from 100% for a number of semicrystalline polymers. For most of these polymers, the sum of the amorphous content and the crystalline fraction was 0.7, meaning that ca. 30% rigid amorphous fraction was present in these samples after a cooling at 0.5 K min−1 rate. Thus, the presence of the rigid amorphous phase was confirmed in five semicrystalline polymers: PET, Nylon 6, PVF, Nylon 66 and polycaprolactone [1]. Somewhat later poly(butylene terephthalate) and bisphenol-A polycarbonate [3] were added to this list. In this paper we also report details on a special effect of the rigid amorphous phase (RAP) on the mobile amorphous phase (MAP): the hysteresis peak at the glass transition of the MAF disappears under the influence of the RAP, and this raises the question whether the glass transition of the MAF becomes time independent in semicrystalline polymers.

Photoacid generators for catalytic decomposition of polycarbonate

Abstract: The photo-activated, acid catalyzed decomposition of polycarbonate was investigated in this study. The impact of the chemical and physical properties of the photoacid generators (PAG) and the ambient atmosphere effect on polycarbonate decomposition were discussed. The photo-patterns resulted from the photoacid catalyzed decomposition of a polycarbonate can be used as a sacrificial placeholder for fabrication of microelectromechanical and microfluidic devices. The effects of acid strength, vapor pressure of the acid, PAG activation process, and ambient conditions (temperature, moisture, and oxygen concentrations) on polymer film decomposition were studied. Several superacids (e.g. triflic and nonaflic based PAGs) were not suitable for decomposition of the polycarbonate because of their high vapor pressures resulting in the high volatility properties. From the decomposition experiments it was found that the nonfluorinated sulfonic acid based PAGs do not posses the superacidity needed for decomposition. Perfluorinated methide and a tetrakis (pentafluoropheyl)borate PAG were effective in the decomposition of polycarbonate films. The combination of two PAGs, one which generates high vapor pressure acid (thus, highly volatile) and the other with a lower vapor pressure acid (thus, less volatile) showed very low residue levels. This is because of the volatility of the generated high vapor pressure acid (usually remaining acid in the film was the cause of the residue left behind) and the remaining nonvolatile low vapor pressure acid was sufficient to decompose the polycarbonate that was not decomposed by the generated high volatile acid. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Study of the selective laser sintering of polycarbonate and postprocess for parts reinforcement

Abstract: Polycarbonate (PC) powder, a common and low-cost amorphous polymer, can be moulded easily by the process of selective laser sintering (SLS). However, the sintered parts cannot be used as functional parts because of their poor mechanical properties. In this article, epoxy resin was applied to improve the mechanical properties of PC SLS parts. Specimens for testing dimensional accuracy, tensibility, flexibility, and impact strength were made by SLS with 75-100 μ PC powder. Some of the specimens were posttreated with two types of epoxy resins. Dimensional accuracy and mechanical properties of the specimens were measured. Microstructures of tensile fracture were observed by scanning electron microscopy. The result shows that the mechanical properties of the specimens are reinforced greatly after the epoxy resin has been infiltrated. Extent of the reinforcement depends on curing agents of epoxy resins. For example, with curing agent W, it is increased to 13.82, 8.00, and 3.69 times, respectively, in tensile, f...