bluuebunny/crossref_metadata_2025_split huggingface dataset:
The immobilization of enzymes onto hydrolyzed polyethylene‐g‐co‐2‐HEMA
Authors: Beddows C. G. , Gil M. H. , Guthrie J. T. 
Published: April 2003

AbstractA study of the immobilization of trypsin and other enzymes onto hydrolyzed poly(2‐hydroxyethyl methacrylate)‐g‐co‐polyethylene using hydroxyl and carboxyl activating agents has been undertaken. Some emphasis was placed on the immobilized trypsin system which involved examination of the variation of (i) the extent of hydrolysis of the graft copolymer, (ii) the concentration of activating agent, and (iii) the temperature of coupling. With the trypsin system, an increase in carbodi‐imide concentration gave an increase in the amount of protein immobilized but a marked decrease in the retention of enzymic activity. Comparison of the behavior of the free with the immobilized enzyme showed that satisfactory yields were obtained and the immobilized system has an extended pH profile and good stability and thus would have broad applicability. The kinetic factors were examined further, and the role of the graft copolymer chains in the immobilized system is discussed.
Characterization of styrene–methyl methacrylate–n‐butyl acrylate terpolymers. I. Average diad concentration determined by 1H‐NMR
Authors: Kobayashi Minoru 
Published: April 2003

AbstractThe average diad concentrations of methyl methacrylate (MMA) unit, P2{MiMj}, of the title terpolymer prepared by radical polymerization with various conversions were studied by 1H‐NMR measurements. Several methoxy proton peaks of MMA resolved by the diamagnetic shielding effects of styrene were assigned to the individual microstructures of MMA‐centered triads. The P2{MiMj} were determined from these peak ratios according to the terminal copolymerization model and the Ham's assumption of statistical simplification for a multicomponent copolymer (P2{MiMj} = P2{MjMi}), The observed values, P2{MiMj}, agreed with the values calculated from the monomer reactivity ratios for each conversions, and agreement with the copolymerization theory was evident.
Effect of flaw size on tensile rupture and morphology of fracture surface of synthetic rubbers with special reference to rocket insulator compound
Authors: Deuri A. Saha , Bhowmick Anil K. 
Published: April 2003

AbstractStudies on tensile strength of polybutadiene (BR) and ethylene–propylene diene rubber (EPDM) having a wide range of flaw sizes have been carried out under both normal and aging conditions. A similar study has been done for a solid propellant rocket insulator compound, based on EPDM. The morphology of tensile fracture surface has also been reported in each case in order to understand the mechanism of rupture. Unlike NR, EPDM, and BR gum vulcanizates, both unaged and aged, show no critical cut length (lc). lc may be defined as the cut length at which the strength decreases abruptly (sometimes there is a drop of a factor of 3 or more, at lc). However, the insulator compound, based on EPDM, exhibits a definite lc in the region of 1.5–1.7 mm. This arises because of anisotropic effect of asbestos fibers. Scanning electron microscopic studies show that the mechanisms of rupture of EPDM and BR gum vulcanizates are similar throughout the whole range of precuts. It occurs through a tearing process originated from the given precut at the center of the samples. A quantitative relation between tensile strength and distance between crack lines/tear lines has also been found. Though insulator compound shows a definite lc, similar fracture surface has been observed over the entire range of flaw sizes.
Preparation of photoresist polymer by a photoreactive monomer containing N,N‐diethyldithiocarbamate group
Authors: Yamashita Keiji , Nakano Akio , Tsuda Kazuichi 
Published: April 2003

AbstractA novel photosensitive monomer with a pendant photoreactive diethyldithiocarbamoyl group, VBDC, was synthesized and copolymerized with some vinyl monomers by AIBN. The copolymers obtained have efficient photocrosslinking abilities, and are thermally stable. Therefore, there was no loss of dithiocarbamoyl group during radical polymerization, and the polymerization proceeded through vinyl group. The degree of photocrosslinking was proportional to the concentration of the photosensitive group, but photosensitivity of the polymer was not. Water‐soluble photoreactive copolymers, VBDC with AAm or MA, were also prepared. AAm copolymer has a good photosensitivity by only 3 mol % VBDC incorporation. Photocrosslinking yields of these polymers depend on the viscosity of original polymers except in the case of low concentration of VBDC. The relation between copolymer composition and glass transition temperature was also investigated. From the investigation of Tg, it was concluded that the copolymer structure largely affected on ΔTg. The mechanism of photocrosslinking was studied by photodecomposition of benzyl N, N‐diethyldithiocarbamate, and the result that the decreases of sulfur content clearly related to photocrosslinking points was also obtained.
Gas transport in poly(vinyl cyclohexanecarboxylate)
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori 
Published: April 2003

AbstractLow‐pressure gas permeation measurements were performed on poly(vinyl cyclohexanecarboxylate) to evaluate its transport characteristics. The transport data of CO2, O2, N2, He, and Ar, were presented as a function of temperature ranging from 15 to 85°C. The apparent transport parameters were determined by the time lag method above and below the glass transition temperature and they were compared with other polymers of similar chemical structures. The side chain of the polymer has a bulky cyclohexyl group, which seemed to increase gas diffusivity. The activation energy for diffusion seemed to be related with the polarity of side chain. The relationships between gas diffusivity, physical properties, and chemical structure were qualitatively discussed in comparison with the data on poly(vinyl benzoate) and poly(vinyl acetate).
Direct pyrolysis mass spectrometry of chlorine‐containing polymers using capillary GC/MS
Authors: McGuire Jeffrey M. , Bryden Charles C. 
Published: April 2003

AbstractA direct pyrolysis mass spectrometric technique has been developed and applied to several chlorine‐containing polymers. The capillary column in the gas chromatograph has been replaced by uncoated fused silica tubing to avoid the problem of column degradation induced by the polymer pyrolyzates. Under appropriate conditions, the pyrolysis mass spectra were found to be highly reproducible and to serve as “fingerprints.” The technique can be readily applied to carbon‐black‐filled, crosslinked elastomers, as well as polyblends and composites. The quantitative aspects of the technique have also been addressed.
Measuring and modelling the transition layer during the dissolution of glassy polymer films
Authors: Krasicky P. D. , Groele R. J. , Rodriguez F. 
Published: April 2003

AbstractThe technique of laser interferometry is now used routinely by the microelectronics industry for the measurement of the dissolution rates of thin polymer films. In addition to the rate of dissolution, laser interferometry can also provide quantitative information on the thickness of the transition layer between the dissolving glassy polymer and the liquid solvent. This paper describes how observed patterns of reflected light intensity may be analyzed to calculate the thickness of the transition layer for polymers that dissolve with little or no swelling. The technique requires knowledge of the shape of the concentration profile in the transition layer. However, by assuming various simple model profiles one may obtain a reasonable estimate. Experimental measurements of poly(methyl methacrylate) (PMMA) films dissolving in methylethyl ketone indicate transition layers of thicknesses 0 to 0.1 μm for PMMA of molecular weights Mw = 37,000 to 1,400,000.
Separate or simultaneous immobilization of glucose oxidase and peroxidase on latex particles and their function
Authors: Kawaguchi Haruma , Koiwai Naoko , Ohtsuka Yasujii 
Published: April 2003

AbstractGlucose oxidase and peroxidase were immobilized individually or simultaneously on aminated latex particles by using sodium meta‐periodide and borohydride. The amount of immobilized enzymes and their activity depended on the surface potential of particles and the surface density of their own, respectively. In the simultaneous immobilization of two enzymes, the predominant immobilization of peroxidase is attributed to higher carbohydrate content in peroxidase compared with that in glucose oxidase. Simultaneously immobilized enzymes worked better in the determination of glucose than the mixture of separately immobilized ones because of the close proximity of the two enzymes.
Preparation of ion exchange membranes by plasma polymerization. I
Authors: Sakata Jiro , Wada Mitsuo 
Published: April 2003

AbstractPlasma polymerizations of three kinds of amines, γ‐aminopropylethoxydimethylsilane (APEMS), allylamine (AA), and pyrole (PY), were investigated by IR and XPS analysis. Plasma‐polymerized films were deposited on porous substrates, and ion exchange abilities of the composite membranes were measured. When APEMS were used as the monomer, the polymer retained the chemical structure of the monomer, amino groups. However, when AA and PY were used as the monomers, the plasma polymers contained a larger amount of amido structures than did the polymer of APEMS. Each membrane had ion exchange ability. In particular, the membrane prepared from APEMS showed superior ion exchange ability, anion permselectivity and conductivity, in acidic solutions. This property was attributed to the chemical structure of the polymer from APEMS retenting amino groups. The ion exchange properties of the membranes depended on the pH of the solution. In particular, the membrane of APEMS showed high membrane potential and low electric resistance only in a narrow pH region due to the weak basicity of amines and the hydrophobic property of the polymer.
Dynamics of the threadline in melt spinning
Authors: Martin W. K. 
Published: April 2003

AbstractIn the nylon 6 melt spinning process at speeds of 900 and 1200 m/min the quenching is done in a stepwise manner. The effect on physical data of the drawn yarn is investigated and correlation between quench height, water takeup, and boiloff shrinkage discussed. Length changes across the takeup machine are also measured as function of quench height and seem to correlate with physical data. The speed of length changes for both finished and unfinished yarn as a function of quench height suggests a molecular oscillation along the spinning line rather than a continuous orientation of the molecular structures. A secondary disorientation zone is defined.
Studies on some physical properties and structural characteristics of methyl methacrylate‐grafted silk fiber
Authors: Tsukada Masuhiro 
Published: April 2003

AbstractStructural characteristics and physical properties of methyl methacrylate‐grafted silk fiber from Bombyx mori were studied by X‐ray diffractometry, differential scanning calorimetry (DSC), thermogravimetry, and scanning electron microscopy. Methyl methacrylate (MMA)‐grafted silk fiber with a grafting yield of more than 30% showed two endothermic peaks at 320°C and 390–410°C, which are attributed to the thermal decomposition of silk fibroin and MMA polymer filled in the fiber, respectively. These DSC results indicate that MMA‐grafted silk fiber showed a poor compatibility in the relation between the silk fibroin molecules and MMA polymer. The weight of the MMA‐grafted silk fiber decreased as observed at 160°C on the thermogravimetric thermograms due to the evaporation of water from the sample with increasing graft yield. The crystalline structure of MMA‐grafted silk fiber remained unchanged regardless of MMA grafting. Taking into account the X‐ray diffraction patterns and the increasing graft yield with reaction time, it is assumed that the graft chains of MMA polymer have penetrated into a weak aggregate region and not in the crystalline region of silk fibroin.
The effect of thermal aging on xanthan solutions
Authors: Milas M. , Linossier J. L. , Contat F. 
Published: April 2003

AbstractThe viscosity stability of xanthan solutions is crucial to petroleum recovery processes. The effects of oxygen concentration, pH, and temperature on viscosity during aging up to 6 months were studied. The structure modifications of the xanthan (substituent contents, weight‐average molecular weights) with aging times were followed and related to viscosity loss. In all cases, the acetyl groups were hydrolyzed. The best stability to thermal aging corresponds to neutral or basic conditions with very low oxygen concentrations. At these conditions the viscosity was stabilized to about 50% of its initial value after 6 months at 80°C. In these cases the pyruvate groups were not hydrolyzed. The stabilization of main chain breaks in the ordered xanthan conformation improves the stability results.
Charring processes in thermoplastic polymers: Effect of condensed phase oxidation on the formation of chars in pure polymers
Authors: Martel B. 
Published: April 2003

AbstractFifteen different pure polymers were studied by thermal methods under air, nitrogen, and nitrous oxide in order to determine their tendency to char in relation with their structure and the experimental conditions used. Styrene polymers and aliphatic polyolefines give chars under air and total volatilization without carbonization under nitrogen and nitrous oxide, showing the essential part played by oxygen in the charring process. On the opposite, ambient oxygen has some effect on the carbonization of polymers containing aromatic rings in their main chain. A schematic mechanism of the charring process is discussed in which condensed phase oxidation, formation of olefinic bonds and crosslinking, dehydrogenation–aromatization are postulated.
Continuous preparative method of relatively large and uniform polymer beads and their application to immobilization of urease
Authors: Ogawa N. , Kawauchi Y. , Nishimura K. , Sugii A. 
Published: April 2003

AbstractAn apparatus for continuous preparative method of polymer beads was investigated. Monomer droplets formed in glycerol were continuously introduced to a rotating glass tube which was filled with warmed glycerol and polymerized. Polymer beads of around 4 mm diameter were obtained. As an application of the polymer beads, urease was immobilized on the beads and their properties were evaluated. Macroreticular type of beads prepared with a mixture of maleic anhydride, styrene, and divinylbenzene showed the highest enzymatic activity among the beads tested, and the urease immobilized beads could be successfully applied for determination of blood urea nitrogen in human sera.
The oxygen index method in fire retardance studies of polymeric materials
Authors: Camino G. , Costa L. , Casorati E. , Bertelli G. , Locatelli R. 
Published: April 2003

AbstractThe oxygen index test is a fundamental tool in basic research on polymer combustion and on mechanisms of fire retardance. Although the oxygen index should provide an evaluation of intrinsic flammability of polymeric materials, its response may depend on geometry of the specimen. This is shown by comparing the behavior of polypropylene fire retarded with different additive systems. The implication of such in mechanistic studies is discussed. Furthermore, new measurements are proposed to be carried out with the oxygen index apparatus, which give parameters related to ease of ignition, behavior on forced burning, and thermal insulating characteristics of char developed on burning the material.
Effect of impurities on emulsion polymerization: Case II kinetics
Authors: Huo B. P. , Campbell J. D. , Penlidis A. , MacGregor J. F. , Hamielec A. E. 
Published: April 2003

AbstractThe effects of water‐soluble and monomer‐soluble impurities on the kinetics of emulsion polymerization of monomers following Case II kinetics (e.g., styrene) are investigated. Experimental studies reveal that impurities can have an appreciable effect on both polymer particle nucleation and growth. These effects are shown to be well predicted by a mathematical model.
Block copolymers derived from azobiscyanopentanoic acid. XI. Properties of silicone–PMMA block copolymers prepared via polysiloxane(azobiscyanopentanamide)s
Authors: Inoue Hiroshi , Ueda Akira , Nagai Susumu 
Published: April 2003

AbstractMechanical, thermal, and surface properties of poly(dimethylsiloxane)–poly(methyl methacrylate) block copolymers (PDMS‐b‐PMMA) prepared by the use of polysiloxane(azobiscyanopentanamide)s were intensively investigated. The mechanical strength of block copolymers was found to decrease with an increase of siloxane contents. Dynamic mechanical analysis (DMA) of block copolymers having long siloxane chain length (SCL) and high siloxane content revealed the existence of two glass transitions attributable to microphase separation of two segments. Differential scanning calorimetry (DSC) also gave some evidence of microphase separation supporting the DMA results. It was observed that the incorporation of PDMS segments in block copolymers improved thermal stability of PMMA, as confirmed by thermogravimetric analysis. Surface analysis of the block copolymers films cast from several solutions indicated surface accumulation of PDMS segments, as revealed by water contact angle and ESCA measurements.
Structural characteristics of 2‐hydroxyethylmethacrylate (HEMA)/methacrylamide (MAA)‐grafted silk fibers
Authors: Tsukada Masuhiro 
Published: April 2003

AbstractA series of 2‐hydroxyethylmethacrylate (HEMA)/methacrylamide (MAA)‐grafted silk fibers obtained in various comonomer compositions was prepared and their structural characteristics were studied by X‐ray diffractometry, differential scanning calorimetry, and scanning electron microscopy. HEMA/MAA‐grafted silk fibers with a graft yield of about 60% obtained in a HEMA/MAA mixture system containing 20% of HEMA and 80% of MAA on a weight basis showed endothermic peaks at 280 and 420°C (shoulder form), which are attributed to the thermal decomposition of the MAA and HEMA polymers, respectively, in addition to the thermal decomposition peak of the silk fibroin fiber which appeared at 323°C. These DSC results suggest that the HEMA/MAA‐grafted silk fiber showed a low compatibility in the relation between the silk fibroin molecules and HEMA and/or MAA polymers. The crystalline structure of the HEMA/MAA‐grafted silk fiber remained unchanged regardless of the HEMA/MAA grafting ratio even when the graft yield value reached 120%.
Processing of ultrahigh molecular weight polyethylene
Authors: Wang Xi‐You , Li Sheng‐Ying , Salovey R. 
Published: April 2003

AbstractThe extent of recrystallization of nascent UHMWPE powder is easily measured by calorimetry. Melting and recrystallization of nascent UHMWPE at 140°C can be suppressed by compression molding. Crystals of UHMWPE prepared from dilute solution show a peak melting temperature of 140°C and exhibit crystallinity up to 75.5% depending on crystallization temperature. Large changes in crystallinity result from drawing single crystal mats or compression‐molded films.
Characterization of copolymers of N‐vinyl‐2‐pyrrolidone with 2‐phenyl‐1, 1‐dicyanoethene
Authors: Kharas Gregory B. 
Published: April 2003

AbstractCopolymers of N‐vinyl‐2‐pyrrolidone and 2‐phenyl‐1, 1‐dicyanoethene were studied. Infrared, proton, and carbon‐13 spectra of the copolymers are discussed by comparison with poly(N‐vinyl‐2‐pyrrolidone), model compounds, and various copolymers. Thermal behavior of the copolymers was investigated by using DSC, TMA, and TGA methods. Thermal as well as thermooxidative stability of the copolymers was found to be lower than those of poly(N‐vinyl‐2‐pyrrolidone).
Modification of polyimide coatings by high energy ion bombardment
Authors: Zussman M. P. , Wood S. , Scala L. C. , Bartko J. , Vincenz A. 
Published: April 2003

AbstractExposure of 25‐μm films of polyimide and polyamideimide to high doses (> 1015/cm2) of energetic ions (energy ≥ 100 keV) resulted in physical and chemical modification of the film surface. Cross‐section microscopy revealed damaged layers extending beyond the projected ion range; conductivity in this damaged layer was found to be as high as 103ω−1 cm−1. Surface conductivity was found to be a function of ion energy and dose, with an exponential energy dependence from 200 to 900 keV. The temperature dependence and thermal stability of the surface conductivity were determined.
Development of an elastomer with a high static or breakaway friction coefficient
Authors: Meier Joseph F. , Siemon John T. , Quirk James F. 
Published: April 2003

AbstractThis paper reviews the literature concerning the measurement of friction coefficients (μ) for elastomers and summarizes our data measured under static or breakaway conditions against epoxy painted steel using ∼ 176 psi contact pressure. Although largely related to missile launch system applications, the μ values presented are specific for interface pairs, normal loading force, and speed. Therefore, this article should serve as a starting point for those requiring specific friction data for selected elastomers.
Chemical modification of poly(2,6‐dimethyl‐1,4‐phenylene oxide) via phase transfer catalysis
Authors: Percec Simona 
Published: April 2003

AbstractThe chemical modification of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) has been performed under phase transfer catalyzed (PTC) conditions. Four types of reactions: Williamson etherification, cyanide displacement, esterification, and heterocyclic group transfer have been identified as positive reactions involving the nucleophilic displacement on PPO. In reaction with alcohols, under PTC conditions, functional yields as high as 100% were obtained while for the esterification reaction functional yields of 92% were reached. Low conversions were found in reactions with cyanides and heterocylic compounds. Possible interactions of the reactive sites leading to additional crosslinking are being suggested. Minor changes in thermal stability of substituted PPO compared with the parent polymer were recorded. The modification of their permeation properties to gases was attributed to changes in polymer chain mobility and packing as well as to changes in polymer side chain polarity.
Moisture‐induced plasticization of amorphous polyamides and their blends
Authors: Ellis T. S. 
Published: April 2003

AbstractThe moisture‐induced plasticization of some amorphous polyamides in pure and blended form has been determined by calorimetric methods. The compositional dependence of the glass transition temperature of these polymer‐diluent systems has been adequately accounted for using an existing predictive expression derived from both a conformational entropy and a thermodynamic treatment of the glass transition phenomenon. The success of this approach to account for the behavior of amorphous polyamide blends containing hydrophobic and hydrophilic constituents exemplifies the importance of compositional parameters in determining the overall response of morphologically complex hydrophilic polymers. The results add further credence to the simple plasticizing action of water in polar polymers irrespective of their chemical and physical constitution.