Showing papers on "Polycarbonate published in 1993"

Model of the selective laser sintering of bisphenol-A polycarbonate

Abstract: Selective laser sintering (SLS) is a new additive process for rapidly preparing prototype parts by selectively fusing portions of layers of polymer powder with a rastered, modulated, CO 2 laser beam. Layer to layer fusion is important for achieving good mechanics properties. Generally, the fusion depth is found to be a function of laser beam overlap on adjacent scans, scan speed, and intensity. It is also a function of the kinetic rates of powder sintering and of heat transfer. A one-dimensional model of the SLS thermal process is presented that can accurately predict, to within 20%, the effect of these process and material parameters on experimentally observed fusion depths in bisphenol-A polycarbonate powders

Gas transport properties of polycarbonates and polysulfones with aromatic substitutions on the bisphenol connector group

Abstract: The effect that substitution of aromatic groups on the bisphenol connector unit of bisphenol-A based polycarbonate and polysulfone materials has on their gas transport properties was assessed. Replacement of a methyl group by a phenyl ring (bisphenol acetophenone polycarbonate, PC-AP, and bisphenol acetophenone polysulfone, PSF-AP) gives a small increase in permeability coefficients with similar or slightly higher selectivity for all gases compared to bisphenol-A polycarbonate, PC, or polysulfone, PSF. Substitution of two locked phenyl rings (fluorene bisophenol polycarbonate, FBPC, and fluorene bisphenol polysulfone, FBPSF) in place of the methyl groups in the connector unit leads to permeability and solubility coeffcients that are about twice those observed for PC or PSF. Increases in permeability for the polycarbonate and polycarbonate and polysulfone materials with aromatic substitutions are related to their larger fractional free volume. FBPC and FBPSF have the largest fractional free volume and the largest permeability coefficients. Thermal measurements show that the fluorene based polycarbonate and polysulfone materials have the highest thermal and oxidative stability. Such aromatic substitutions can be useful for developing gas separation membranes to be used in harsh thermal or oxidative environments. © 1993 John Wiley & Sons, Inc.

Simulation of elastic and plastic response in the glassy polycarbonate of 4,4'-isopropylidenediphenol

Abstract: The previously determined molecular structure model of the dense, glassy polycarbonate of 4,4'-isopropylidenediphenol («Bisphenol A polycarbonate» (PC)) has been used in conjunction with the structure-probing techniques of Theodorou and Suter and those of Mott et al. developed for stactic polypropylene (PP) to determine the small-strain elastic constants and study the mechanisms of large-strain plastic deformation of PC. The calculated elastic moduli of the microstructures all fall above the experimentally reported range but are not considered unreasonable in view of the relatively small size of the simulation cell and the rigidity of the PC repeat unit

Heavy-ion Tracks in Polycarbonate - Comparison With a Heavy-ion Irradiated Model-compound (diphenyl Carbonate)

Abstract: The chemical modifications induced by energetic heavy ion irradiation of polycarbonate (PC) film are determined by GPC, HPLC, ESR, TGA, IR and UV spectrophotometry. The main results of the irradiation are creation of radicals, chain scission, cross-linking and appearance of new chemical groups in the main polymer chain. As far as the creation of new groups is concerned, they are determined by means of a model compound of PC: the diphenyl carbonate (DPC). The following compounds are identified after energetic heavy ion irradiation of DPC: salicylic acid, phenol, 4,4'-biphenol, 2,4'-biphenol, 2,2'-biphenol, 4-phenoxyphenol, 2-phenoxyphenol, phenyl ether, phenyl benzoate, phenyl salicylate, 2-phenylphenol and 2-phenoxyphenyl benzoate. A similarity between the heavy ion irradiation and a heat treatment has also been established with DPC. On the basis of these results, we try to give an explanation of the preferential attack along the tracks of the irradiated film. Also, an explanation of the well-known beneficial effect of an UV exposition of the irradiated film on the selectivity of this preferential chemical attack is suggested.

Commercial applications of ion beam deposited diamond-like carbon (DLC) coatings

Abstract: We report the results of applications development by Diamonex on ion beam deposited diamond-like carbon (DLC) coatings. Many of the process scale-up issues for ion beam deposition of DLC coatings have been solved. Commercial applications for abrasion resistant DLC-coated optics take advantage of the transparency, chemical inertness, low friction coefficient, high hardness and excellent adhesion of ion beam deposited DLC coatings. DLC-coated polycarbonate sunglass lenses are more resistant to abrasion by #0000 steel wool than any polycarbonate sunglasses commercially available. Using DLC, highly durable coatings with a variety of iridescent reflected colors can be produced. In addition to providing polycarbonate with substantially improved abrasion and chemical resistance, the ballistic strength of polycarbonate is maintained. DLC-coated float glass windows in supermarket laser bar code scanners demonstrated a projected average lifetime of 9 years, approximately 100 times longer than uncoated glass. ZnS and ZnSe IR windows coated with DLC coatings 1–2 μm thick are highly transparent from 3 to 15 μm wavelength and exhibit large improvements in chemical resistance and abrasion resistance relative to uncoated ZnSe and ZnS. The combination of the high electrical resistivity, relatively high thermal conductivity, low friction coefficient, high hardness and excellent adhesion to metals of ion beam deposited DLC, permits its use as a scratch-resistant dielectric layer for copper heat removal devices in multichip modules.

Effect of drawing on structure and properties of a liquid crystalline polymer and polycarbonate in - situ composite

Abstract: Fibers (strands) with various draw ratios were spun from the liquid crystalline state of a pure aromatic liquid crystalline copoly(ester amide) and the melts of its blend with polycarbonate. Scanning electron microscopy (SEMI, wide angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) were employed to investigate the structure and properties of the resulting fibers. Mechanical properties of the fibers were also evaluated. It was found that both the crystallite size and heat of fusion of the liquid crystalline polymer (LCP) increase steadily with draw ratio. However, the crystal-nematic transition temperature of the LCP is virtually unaffected by drawing. Moreover, heat of fusion of LCP is much smaller than that of isotropic condensation polymers despite the presence of very sharp dmraction peaks in WAXS measurements. These results are ascribed to the (semi)rigid rod nature of the LCP chains and the persistence of an ordered structure in the LCP melt, i.e., entropy effect. It was further observed that tensile modulus and tensile strength along fiber axis rise with draw ratio for the composite fibers. The elastic modulus of the composite fibers were found to be as high as 19 GPa and tensile strength reached 146 MPa with draw ratios below 40 and an LCP content of 30 wt%. Compared with the thermoplastic matrix, the elastic modulus and tensile strength of the in-situ composite have increased by 7.3 times and 1.4 times, respectively, with the addition of only 30 wt% LCP. This improvement in mechanical properties is attributed to fibrillation of the LCP phase in the blend and the increasing orientation of the LCP chains along the fiber axis during drawing.

Multicomponent polyester/polycarbonate blends with improved impact strength and processability

Abstract: The present invention relates to polyester/polycarbonate blends having improved low temperature impact strength and processability. More particularly, this invention relates to a thermoplastic molding composition containing an aromatic carbonate polymer, a poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) resin, and a copolyester which consists essentially of repeat units from mixtures of isophthalic acid, terephthalic acid and 1,4-cyclohexanedimethanol.

Broadband dielectric study on binary blends of bisphenol-A and tetramethylbisphenol-A polycarbonate

Abstract: Broadband dielectric spectroscopy (10 -1 to 10 7 Hz) and DSC have been used to study the α- and β-relaxations in blends of bisphenol-A polycarbonate (BPA-PC) and tetramethylbisphenol-A polycarbonate (TMBPA-PC) in the temperature range from 93 to 553 K. All blends show one broadened α-relaxation as compared with the homopolymers. At temperatures below T g the β-relaxations corresponding to both homopolymers are observed in the blends. The β-relaxation strength obeys dilution laws with no indication of a critical TMBPA-PC concentration above which the β-relaxation in BPA-PC is totally suppressed

Aging of thin polyimide-ceramic and polycarbonate-ceramic composite membranes

Abstract: The gas-transport properties of several polymer-ceramic composite membranes with glassy polymer layers having effective thicknesses of approximately 4000 A exhibit strongly time-dependent behavior. The membranes, prepared from polyimide and polycarbonate, demonstrated decreases in gas flux of 40-60% in the first 20 days following manufacture. The pure-gas selectivity of these membranes for the He/N 2 separation increased over the same period to values approximately 50% higher than those of a thick film of the same material. Substructure compaction of these membranes is nonexistent, unlike integral-symmetric polymeric membranes, so transport property changes are less ambiguous to interpret. We suggest a true glassy state drift in the properties of the selective layer of the composite membranes as the cause for the observations. The observations show that transport properties determined on thick films of glassy polymers may differ significantly from the properties of thin, gas permeation membranes

Phenylene motion in polycarbonate - influence of tensile-stress and chemical modification

Abstract: Deuteron NMR was utilized to study phenylene group motions in glassy polycarbonate (PC) as a function of tensile stress and chemical modification. A special stretching device was constructed allowing the application of forces up to 1500 N during the measurement. While cold drawing of PC effects motional restrictions equivalent to a temperature shift of 10 K, a reversible strain near the yield point enhances the ring dynamics slightly. Methyl group substitution at the ortho positions gives rise to even more constraints, shifting the onset of fast ring flips by about 180 K.

Local packing in glassy polycarbonate by carbon-deuterium REDOR NMR

Abstract: Carbon-deuterium internuclear dipolarcouplings have been measured in a homogeneous mixture of 5% [carbonyl- 13 C]polycarbonate and 95% [methyl-d 6 ]polycarbonate using rotational-echo double-resonance NMR. The observed 13 - 1 H couplings can be interpreted in terms of intermolecular distances. The distance from the carbonyl carbon of one polycarbonate chain to the average deuterium position of the closest methyl group of the nearest-neighbor polycarbonate chain is 3.8 A

Polycarbonate resin composition

Abstract: PURPOSE:To obtain the subject composition having excellent thermal stability in granulation and molding by blending a polycarbonate resin with a specific thiobisphenol-based compound (or mixture thereof) at a specific amount CONSTITUTION:The objective composition obtained by blending (A) 100 ptswt polycarbonate resin produced from bisphenol A, etc, and having 10000-100000 (preferably 15000-35000) viscosity-average molecular weight with (B) 001-05 ptswt (preferably 003-015 ptswt) compound expressed by formula I and/or formula II ((n) and (m) are 1-3; R1 to R4 are 1-4C alkyl; R5 to R10 are 1-4C alkyl) Furthermore, the compound expressed by formula I and the compound expressed by formula II are preferably used at a ratio of 9/1 to 1/9 as the component B

Blends of linear polymers with macrocyclic oligomers

Abstract: Intimate blends of macrocyclic oligomer compositions, such as cyclic polycarbonate or poly(alkylene dicarboxylate) oligomer mixtures, are blended with linear polymers, especially addition polymers. The blends flow easily and are frequently homogeneous. The macrocyclic oligomers therein may be polymerized to produce resin blends having advantageous properties.

Multistage melt polymerization of bisphenol‐A and diphenyl carbonate to polycarbonate

Abstract: A multistage melt polycondensation of bisphenol-A and carbonate has been studied experimentally using LiOH·H2O catalyst. The reaction process consists of batch and semi-batch periods with different temperature and pressure conditions. It was observed that a small amount of diphenyl carbonate lost from the reaction mixture by vaporization had little effect on the molecular weight in the batch reaction period but the efficiency of subsequent low-pressure semibatch polycondensation was affected by the change in the mol ratio of the phenyl carbonate group to the hydroxyl end group. A molecular species model developed for the multistage process was used to analyze the kinetics of the polycondensation process. The composition of the reaction mixture was analyzed of HPLC and compared with model simulations. In particular, the effect of evaporative loss of diphenyl carbonate on the progress of reaction is discussed in detail. © 1993 John Wiley & Sons, Inc.

Process for forming scratch-resistant silicon oxide layers on plastics by plasma-coating

Abstract: In order to produce scratch-resistant silicon oxide layers (coatings) on plastics, such as polymethyl methacrylate or polycarbonate by plasma coating by means of a gaseous organosilane and/or organosiloxane, a plasma treatment with a gaseous or vapour-form unsaturated organic compound whose unsaturated group preferably contains more than one pi -electron pair bonded to carbon or nitrogen atoms, for example acetylene, or with nitrogen, optionally together with oxygen or hydrogen, is carried out before or during the plasma coating.

Redistribution of organic polycarbonate compositions

Abstract: Polyestercarbonates, particularly those containing aliphatic dicarboxylic acid-derived structural units, are redistributed by heating in the presence of a carbonate redistribution catalyst, and, optionally, a diaryl carbonate. The redistribution products have weight average molecular weights different from, and typically lower than, the initial molecular weight.

Heat-resistant polycarbonate resins containing 2-alkyl-3,3-bis(p-hydroxyphenyl)phthalimide

Abstract: Polycarbonate resins containing repeating or recurring polymer chain units of the formula: ##STR1## wherein R represents alkyl are useful in high temperature applications, when thermoplastically molded into articles.

Continuous microscratch measurements of thin film adhesion strengths

Abstract: The adhesion strengths of metal/ceramic, metal/polymer, and polymer/polymer interfaces have been characterized using the continuous microscratch technique. In these experiments, a conical diamond indenter was driven simultaneously into a thin film at a rate of 15 nm/s and across the film surface at a rate of 0.5 μm/s until a load drop or other discontinuity occurred, indicating film failure. The critical load at failure of the thin film was taken as a measure of the adhesion strength. For metal/ ceramic systems such as Cr thin films on Al2O3, and for diamond-like-carbon (DLC) films on glass, clear load drops provided an accurate measure of the adhesion strengths. For metal/polymer systems such as Cu thin films on PET, a change in the loading pattern and periodic cracking events along the scratch track provided evidence of film delamination. For DLC films on polycarbonate substrates, the carbon thin film cracked before it delaminated. For bulk polymers such as polycarbonate and polystyrene/polypropylene, c...

Process for producing polycarbonate

Abstract: There is disclosed a process for producing a polycarbonate which comprises reacting, by the melt method, (A) a dihydroxy compound with (B) a carbonic diester having a chlorine content derived from chloroformate group of not more than a prescribed level. According to the above process, a polycarbonate which is excellent in transparency, tone of color, heat resistance and water resistance can be efficiently and economically produced.

Blends of polycarbonate containing fluorinated-bisphenol A and polymethyl methacrylate

Abstract: Bisphenol A polycarbonate containing at least 15 mole % of fluorinated bisphenol monomer units such as 2,2-bis-(4--hydroxyphenyl)hexafluoropropane (6F-Bisphenol A) can be blended with polymethyl methacrylate (PMMA) to form thermodynamically miscible, transparent, single phase blends at all compositions.

Flame retardant resin composition

Abstract: PURPOSE:To obtain a flame retardant resin composition consisting of a polycarbonate resin, a thermoplastic resin, a specific phosphorus compound and a drip-preventing agent, improved in flame retardance, mechanical properties, thermal stability in molding and processing, surface appearance, etc., and useful for electrical parts, car parts, etc. CONSTITUTION:The resin composition consists of (A) 5-95 pts.wt. of an aromatic polycarbonate containing no halogen, (B) 95-5 pts.wt. of a thermoplastic resin which is a polymer or a rubber-containing polymer obtained from an aromatic vinyl monomer and a vinyl cyanide monomer, (C) 1-20 pts.wt. (based on 100 pts.wt. total amount of the component A and the component B) of a phosphorus compound of the formula [Ar1, Ar2, Ar3 and Ar4 are monovalent aromatic groups; x is aromatic group derived from dihydric phenols; (n) is 1-5] and (D) a drip-preventing agent having an amount enough to prevent drip of the resin in burning.

Dynamics of bisphenol-a polycarbonate in the glassy and rubbery states as studied by neutron-scattering and complementary techniques

Abstract: Quasielastic neutron scattering, dielectric spectroscopy, and mechanical relaxation have been employed to study the dynamics of Bisphenol A polycarbonate (BPA-PC) in the glassy and rubbery state. Using these techniques the dynamics associated with the primary (α-) relaxation and of the γ-relaxation in a frequency interval spanning 13 decades were obtained. The temperature dependence of the primary relaxation times conforms to the Vogel-Fulcher-Tammann equation whereas the γ-relaxation times display an Arrhenius temperature dependence with an apparent activation energy of 10.8 kcal/mol