摘要 :
Nylon hydrolase degrades various aliphatic nylons, including nylon-6 and nylon-66. We synthesized a nylon-66 copolymer (M_w=22,900, M_n=7,400), in which a part of an adipoyl unit (32 % molar ratio) of nylon-66 was replaced with a ...
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Nylon hydrolase degrades various aliphatic nylons, including nylon-6 and nylon-66. We synthesized a nylon-66 copolymer (M_w=22,900, M_n=7,400), in which a part of an adipoyl unit (32 % molar ratio) of nylon-66 was replaced with a succinyl unit by interfacial polymerization. To quantify the reaction rate of the enzymatic hydrolysis of nylons at the surface of solid polymers, we prepared a thin layer of nylons on the bottom surface of each well in a polystyrene-based micro-assay plate. The thickness of the nylon layer was monitored by imaging analysis of the photographic data. More than 99 % of the copolymer with thicknesses of 260 nm (approximately 600 layers of polymer strands) were converted to water-soluble oligomers by nylon hydrolase (3 mg enzyme ml~(-1)) at 30 °C within 60 h. These results were further confirmed by TLC analysis of the reaction products and by assay of liberated amino groups in the soluble fractions. The degradation rate of the thin-layered nylon-6 was similarly analyzed. We demonstrate that this assay enables a quantitative evaluation of the reaction rate of hydrolysis at the interface between the solid and aqueous phases and a quantitative comparison of the degradability for various polyamides.
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The effect of isothermal crystallization process on the crystal structure of nylon-6 and nylon-6/montmorillonite nanocomposite between 0 and 180 deg C is examined using X-ray diffraction method. For the examined process, nylon-6 e...
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The effect of isothermal crystallization process on the crystal structure of nylon-6 and nylon-6/montmorillonite nanocomposite between 0 and 180 deg C is examined using X-ray diffraction method. For the examined process, nylon-6 exhibits a gradual transition from gamma- to alpha-phase with increasing crystallization temperature. The crystals of alpha-phase expand and a high temperature crystallization peak appears at 2 theta =28.5 deg in X-ray diffraction pattern for nylon-6 crystallized at 180 deg C. The addition of montmorillonite improves crystalline-phase transition, and increases the perfection of crystallization.
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摘要 :
Poly(butylene terephthalate) (PET) and a poly(ether ester) (PEE) based on PET and poly(ethylene glycol) were melt-blended and extruded as films with quenching. They were then zone-drawn (ZD) and zone-annealed (ZA) at various stres...
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Poly(butylene terephthalate) (PET) and a poly(ether ester) (PEE) based on PET and poly(ethylene glycol) were melt-blended and extruded as films with quenching. They were then zone-drawn (ZD) and zone-annealed (ZA) at various stresses (between 10 and 50 MPa) at temperatures of 160 and 190 degrees C. The goal was to improve their mechanical properties relative to those of the same blend, but cold-drawn (lambda = 5) and isothermally annealed with fixed ends at the same temperatures for 6 h. All samples were characterized by DSC, WAXS, SAXS, and static mechanical property measurements. In contrast to the isothermally annealed samples, the zone-drawn and zone-annealed ones exhibit one population of crystallites arising from the homo-PBT, as demonstrated by the DSC and SAXS measurements. In addition, however, the WAXS photographic patterns indicate that zone annealing at 190 degrees C results in isotropization of crystallites originating from the PEE, resulting in the formation of a microfibrillar-reinforced composite. It is assumed that some of the isotropic crystallization occurs on preexisting homo-PBT crystallites, i.e., a partial cocrystallization occurs, improving the adhesion between the components of the blend. The structural features created in the zone-drawn-zone-annealed materials result in higher values of the Young's modulus and tensile strength in comparison to the materials receiving the simple isothermal treatment (1,200 vs. 480 MPa and 213 vs. 113 MPa, respectively). (C) 1996 John Wiley & Sons, Inc. [References: 26]
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This work describes the interaction of nylon6 (N6) with the random copolymer poly(vinyl butyral) (PVB) at various hydroxyl levels of residual vinyl alcohol in the PVB. The methylene and amide groups of N6 were observed to interact...
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This work describes the interaction of nylon6 (N6) with the random copolymer poly(vinyl butyral) (PVB) at various hydroxyl levels of residual vinyl alcohol in the PVB. The methylene and amide groups of N6 were observed to interact favorably with the PVB, resulting in thermodynamic miscibility at PVB compositions in the range of 0.50-0.65 volume fractions of vinyl alcohol in PVB. The polymers' interaction parameters were estimated to be -0.04 and 0.04 for chi(N6/VA) and chi(N6/PVB). respectively. Miscibility parameter results compared favorably with the miscibility window determined. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 14]
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Two groups of potential migrants were found in nNYlon 'microwave and roasting bags' (MRBs): volatile compounds were released at cooking temperatures and non-volatile compounds were extracted with methanol and/or water. A dynamic h...
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Two groups of potential migrants were found in nNYlon 'microwave and roasting bags' (MRBs): volatile compounds were released at cooking temperatures and non-volatile compounds were extracted with methanol and/or water. A dynamic headspace system at 200 deg.C followed by gas chromatography (GC) coupled to mass spectrometry (MS) was used for determination of volatile compounds. cyclopentanone (31.7 mg/bag), 2-cyclopentyl cyclopntanone (17.4 mg/bag), hxade- cane (2.6 μg/bag), heptadecane (3.2 μg/bag), octade- cane (3.0 μg/bag) and ε-caprolactam (5.0-35.5 mg/ bag) were the main volatile compounds present in the MRBs.
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Three kinds of star-shaped nylon 6 samples with different branched-chain length were prepared by the hydrolytic polymerization of ε-caprolactam using trimesinic acid as trifunctional reactant. The structure of prepared star-shape...
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Three kinds of star-shaped nylon 6 samples with different branched-chain length were prepared by the hydrolytic polymerization of ε-caprolactam using trimesinic acid as trifunctional reactant. The structure of prepared star-shaped nylons was characterized by infrared spectroscopy and ~1H-NMR. Compared with linear-chain nylon 6, star-shaped nylons with the equivalent molecular weight present higher melt flow indices and lower relative viscosities due to decreased molecular dimensions and reduced hydrogen bond interactions between neighboring molecules. The molecular weights of the products were determined by end-group titration and 1H-NMR, and the molecular weight distributions (MWDs) were evaluated by gel permeation chromatography. The results show that the molecular weight decreased and the MWD narrowed as the concentration of trimesinic acid increased. Wide-angle X-ray diffraction patterns of star-shaped and linear-chain nylons show that increasing the concentration of trimesinic acid leads to good symmetry and high crystallizability, but this also degrades crystal perfection as observed using a polarized optical microscope. The viscosity of nylon 6 can be significantly reduced while maintaining its mechanical performance through the use of star-branching and an appropriate concentration of trimesinic acid.
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摘要 :The recovery of platinum from solutions containing [PtCl6]2? using inherently conducting polymer (ICP) powders, membranes and coated fabrics has been investigated. Polyaniline (PAn) powders were able to recover platinum from solut...
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The recovery of platinum from solutions containing [PtCl6]2? using inherently conducting polymer (ICP) powders, membranes and coated fabrics has been investigated. Polyaniline (PAn) powders were able to recover platinum from solution, whereas polypyrrole (PPy) powders and membranes displayed almost no ability to perform this task. Uncoated pieces of nylon and nylon-lycra showed a significant capacity to recover platinum metal, unlike each of the other common fabrics investigated. Surprisingly the amount of platinum recovered by nylon-lycra was not improved by coating the fabric with a layer of ICP. Pieces of nylon-lycra that had previously been soaked in solutions containing [PtCl6]2? released only a small percentage of the bound metal when treated with 5 % HCl. However, subsequent treatment with aqua regia released all of the remaining platinum. A mechanism of platinum recovery by nylon and nylon-lycra involving coordination to functional groups present in their polymeric structures is proposed.
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Ferroelectric behaviour in an aromatic urethane, 4,4'-biphenyl bis-stearyl carbamate, was investigated. It was found that the remanent polarization and coercive field obtained from the D-E curve at 80 degrees C were 49 mC m(-2) an...
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Ferroelectric behaviour in an aromatic urethane, 4,4'-biphenyl bis-stearyl carbamate, was investigated. It was found that the remanent polarization and coercive field obtained from the D-E curve at 80 degrees C were 49 mC m(-2) and 35 MV m(-1), respectively. The pyroelectric constant was found to be 10 mu C m(-2) K-1, and was stable up to the material's melting temperature. [References: 7]
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We have formulated a linear theory for the shielding effectiveness of composite matrix materials and have tested the theory for various amounts of ThermalGraph DKD X carbon fiber within nylon 6,6. The theory predicts that the most...
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We have formulated a linear theory for the shielding effectiveness of composite matrix materials and have tested the theory for various amounts of ThermalGraph DKD X carbon fiber within nylon 6,6. The theory predicts that the most important parameters for the shielding effectiveness of a sample are the carbon-fiber volume percentage and the frequency of the wave to be shielded. Although we expected the model to be valid at low filler-loading levels, it actually performs remarkably, covering an electrical-resistivity range of 10(16) (at low filler-loading levels) to 10(1) Ohmcm (at high filler-loading levels), well above the percolation threshold of electrical-resistivity theory. The model performs much better than those reported in the literature and can be used to determine filler loadings needed to provide a certain level of shielding of electromagnetic waves. (C) 2005 Wiley Periodicals, inc.
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Graft copolymcrization of acrylonitrile (AN) monomer into nylon fabrics without homopolymer formation in the raction medium was carried out to avoid the environmental problems and minimize the product cost.This was enabled by crea...
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Graft copolymcrization of acrylonitrile (AN) monomer into nylon fabrics without homopolymer formation in the raction medium was carried out to avoid the environmental problems and minimize the product cost.This was enabled by creation of free radicals built-in insitue on both surfaces and intermicelles of nylon fabric.The creation of these free radicals was generated by using potassium persulfate (KPS) as a main oxidizing agent in conjunction with sodium bisulfite (SBS) or benzaldehyde sodium bisulfite adduct (BSBS) as reducing agents.In addition to the redox initiation type and concentration,the graft yield (GY).homopolymer (HP),and total conversion percents were also studied in relation to the reaction time and temperature as well as liquor ratio and monomer concentration.At AN concentration of 0.754 mol/L,grafted nylon fabrics having GY of 12.5% and 14.9% were obtained without any HP formation using 1.0/2.0Xl0~(-2)mol/L for each of KPS/SBS and KPS BSBS.respectively.Increasing the monomer concentration up to 1.886 mol/L outstandingly increases the GY to 31.7% and 35.6%.also without HP formation,using 0.3 0.6X10~(-2) mol/L for each KPS SBS and KPS BSBS.respectively.The grafted nylon fabrics were characterized by infrared (IR) spectra and thickness measurement.
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