bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow birefringence and viscosity of cellulose solutions in semi‐dilute regime
Authors: Yasuda Katsunari , Saito Masatoshi , Kamide Kenji 
Published: April 2007

AbstractAn attempt was made to study the flow birefringence and the viscosity of the systems of cellulose in aqueous sodium hydroxide and cadoxen solutions. For this purpose alkali‐soluble cellulose samples with crystal form I (simply denoted as cellulose I sample), prepared from conifer wood pulp by the steam‐explosion method, and alkali‐soluble cellulose samples with crystal form of cellulose II (cellulose II sample), regenerated from cuprammonium cellulose solution under specific conditions, were used. The extinction angle χ of aqueous alkali solutions of the cellulose I sample is significantly less shear rate (γ) dependent as compared with that of the cellulose II sample. In the latter system the χ versus γ relations for a given cellulose sample shifted to the higher γ side with decrease in the average molecular weight. The viscosity of the cellulose II sample in aqueous sodium hydroxide solutions is approximately twice that of the cellulose I sample in the same solvent if compared at the same molecular weight, same concentration, and same temperature. The latter solution showed a non‐Newtonian property at relatively smaller γ than the former solution did. Spin‐lattice relaxation time T1 (by 13C‐NMR) of cellulose in cadoxen solution was smaller in cellulose I, suggesting the existence of intra‐ and intermolecular hydrogen bondings at the C6 position of cellulose molecules in cellulose I solution. A dynamic light scattering study on cellulose in cadoxen showed that in a 5 wt % solution of cellulose I cellulose particles are dispersed with time into smaller particles and the larger particles could be excluded by ultracentrifuge and in cellulose II solutions the cellulose particles had almost the same size during storage. The above findings indicate that in 5 wt% cellulose I solutions in aqueous alkali or in cadoxen, cellulose I is not dissolved molecularly, but a supra‐molecular structure of the solid is at least partly reserved in the above solutions.
Mechanism and kinetics of emulsion copolymerization of vinylidene chloride—Critical conversion at the end of interval 2 and rate of polymerization
Authors: Yu Zaizhang , Jia Hongbing , Li Bogeng , Li Baofang 
Published: April 2007

AbstractIn this paper, the change of vapour pressure in the emulsion copolymerization of vinylidene chloride (VDC) was determined. It was observed that the vapour pressure drops at conversion about 60% when VDC/comonomer = 90/10 (wt). The types of emulsifier, concentrations of emulsifier and initiator, temperature do not effect these conversion values significantly. According to the principle of phase equilibrium, that the critical conversion at the end of Interval 2 in the emulsion copolymerization of VDC is about 60% was suggested. The effects of types of emulsifier, concentrations of emulsifier and initiator, temperature, types and concentrations of comonomer on rate of copolymerization were also studied. It was found that the different types of comonomer will have no great effect on the copolymerization rate and intrinsic viscosity of a VDC copolymer. And a common route and recipe can be adopted for producing different grades of PVDC latex.
Laser photoacoustic and photothermal spectroscopies as novel characterization methods for microparticles
Authors: Kitamori Takehiko , Sawada Tsuguo 
Published: April 2007

AbstractPhotoacoustic and photothermal spectroscopy methods can be effectively applied to the characterization of single microparticles. As the optical beam deflection method, in which a thermal wave generated by non‐radiative transition is detected by deflection of a probe beam, is sensitive for a single microparticle, and is a remote‐measurement method without using a cell, it is suitable for nondestructive characterization of microparticles. This method was applied to determination of chemical species adsorbed on a single microparticle, and spectral differences between leukemia and normal white blood corpuscles could be obtained. A more violent photothermal conversion phenomenon of a particle, laser breakdown and accompanying plasma and acoustic emission, was applied to individual detection and analysis of ultrafine particles in liquids. Laser‐like nonlinear emission from the plasma was observed.
Production of micron‐size monodisperse polymer particles by seeded polymerization utilizing dynamic swelling method with cooling process
Authors: Okubo Masayoshi , Shiozaki Masaya 
Published: April 2007

AbstractMonodisperse polystyrene particles (6.6 μm diameter) were produced by seeded polymerization utilizing the dynamic swelling method with cooling process as follows. Monodisperse polystyrene seed particles (1.8 μm diameter) were dispersed in ethanol/water (3/4 w/w) medium containing styrene monomer, benzoyl peroxide as initiator and poly(vinyl alcohol) as stabilizer at 65d̀C. By lowering the temperature to −5d̀C at a speed of −1d̀C/min the polystyrene seed particles were swollen from 1.8 to 7.7 μm by the absorption of styrene monomer, keeping the high monodispersity. An appropriate amount of water was then added to the dispersion at −5d̀C to depress the redissolution of styrene from the swollen particles into the medium. By elevating the temperature the seeded polymerization was carried out at 70d̀C. The production of submicron‐size polystyrene new particles as a by‐product was depressed by the addition of NaNO2 to the medium.
Soapfree emulsion polymerization of methyl methacrylate in the presence of CaSO3
Authors: Lee Chia‐Fen , Chiu Wen‐Yen 
Published: April 2007

AbstractIn the soapfree emulsion polymerization of a methyl methacrylate‐K2S2O8‐CaSO3‐H2O system, the polymerization rate, average molecular weight of polymer, particle size and particle concentration would vary with the concentration of CaSO3.It was shown that when the concentration of CaSO3 was well below the saturation concentration (3 × 10−4mol/litre H2O), the polymerization rate was higher than that of the system not containing CaSO3. On the other hand, when the concentration of CaSO3 was above the saturation concentration, the polymerization rate at the latter stage was lower than that of the system not containing CaSO3 within our experimental conditions.The molecular weight of polymer was measured by Gel Permeation Chromatography (GPC). It decreased initially and then increased due to the gel effect over the entire course of polymerization. The size of the polymer particles was measured by both photo correlation spectroscopy (PCS) and transmission electron microscopy (TEM), The reaction mechanism was studied according to the above observation. The mechanical property of poly(methyl methacrylate)‐CaSO3 composite obtained from soapfree emulsion polymerization was tested and compared with that obtained from mechanical blending.
Particle nucleation in emulsion copolymerization containing multifunctional monomers
Authors: Nomura M. , Fujita K. 
Published: April 2007

AbstractCharacteristic features of particle nucleation and growth in the emulsion copolymerization of styrene and multifunctional monomers such as ethylene glycol dimethacrylate and divinylbenzene were investigated. It was found that in these emulsion copolymerization systems the rate of polymerization per particle decreased drastically with an increase in the content of the multifunctional monomer in the initial monomer feed, and the number of polymer particles produced, on the other hand, increased corresponding to the decrease in the rate of polymerization per particle. The increase in the number of polymer particles produced was explained on the basis of Smith‐Ewart theory, which predicts that the number of polymer particles produced would increase inversely proportional to the 0.4 power of the volumetric growth rate per particle, that is the rate of polymerization per particle during the interval of particle formation (Interval I). It was pointed out that the decrease in the rate of polymerization per particle in Interval I would be due mainly to a decrease in the monomer concentration in the polymer particles which was caused by crosslinking networks of the resultant polymer.
Polymerization of micelle‐forming monomers: Mechanistic study and characterization of the systems before and after polymerization
Authors: Cochin D. , Zana R. , Candau F. 
Published: April 2007

AbstractCationic surfactants bearing a polymerizable styryl headgroup and a variable alkyl chain with 8–16 carbon atoms have been synthesized. Their aqueous solutions have been characterized by the surfactant critical micellar concentration (CMC) and aggregation number using electrical conductivity, spectrofluorimetry and time‐resolved fluorescence quenching. The photoinitiated polymerization of these surfactants in the micellar state led to stable and transparent or slightly bluish systems. The kinetics of polymerization were measured by dilatometry and were found to be close to those obtained for styrene emulsion polymerization. A mechanism of polymerization is proposed and discussed in terms of micellar dynamics. The polymerized systems, p(Cn‐STY), and the recovered polymers were characterized by means of several complementary techniques. The polymers have high molecular weights (3 × 105‐3 × 106), which indicates that the initial micellar structure is not preserved upon polymerization. The structure of the polymerized systems depends on the alkyl chain length of the surfactant. The p(C16‐STY) systems exhibit a structure similar to that of a polysoap with intramolecular hydrophobic microdomains whereas the p(C8‐STY) systems behave like classical polyelectrolytes.
Effect of crosslinked core on minimum film formation temperature and morphology of composite microspheres
Authors: Omi Shinzo , Kohmoto Takeyoshi , Iso Mamoru 
Published: April 2007

AbstractEffect of crosslinking on minimum film formation temperature (MFT) and particle morphology was investigated using the latices composed by the combination of crosslinked soft core‐hard shell. n‐Butyl acrylate (nBA) and ethylene glycol dimethacrylate (EGDMA) were used to prepare crosslinked rubber with methylmethacrylate (MMA) or styrene (ST) as a hard plastic component. Ordinary batch (flooded with secondary monomer) and semicontinuous (starved feed) operations were employed to compare the thermal properties of composite latices resulting from the different mode of secondary polymerization. As the degree of crosslinking increases, MFT of the latices obtained by batch operation became higher than those by semibatch operation. Observation of microtomed sections of particles stained with RuO4 did not reveal much difference in particle morphologies between the two operations. There was a definite relationship between MFT and molecular weight of THF soluble fraction of composite polymers regardless the mode of operation.
Characteristics of water‐absorbent polymer emulsions
Authors: Watanabe Naotaka , Hosoya Yoshio , Tamura Akira , Kosuge Hiroshi 
Published: April 2007

AbstractWater‐in‐Oil (W/O) and Oil‐in‐Water (O/W) type water absorbent polymer emulsions were studied using two different polymerization methods. W/O type water absorbent polymer emulsions were prepared by the inverse emulsion polymerization of ammonium acrylate (AA), the quaternized salt of dimethyl‐aminoethyl methacrylate (DMQ) and acrylamide (AM) with N,N‐methylene‐bisacrylamide (MBA) as a crosslinker. A pH sensitive water absorbent polymer emulsion was prepared by the conventional emulsion polymerization of diethyl‐aminoethyl methacrylate (DEAEMA) with ethylene glycol dimethacrylate (EGDMA) as a crosslinker.It was confirmed that the water absorption capacity of crosslinked polymers in inverse emulsion was controlled by crosslink density and dissociative charge density, and the crosslinked polyDEAEMA particles had a phase transition property of swelling and shrinking with pH. The dispersions of these water swollen crosslinked polymer particles exhibited an increase in viscosity and thixotropic fluidity.
1H magnetic relaxation times in isotactic polypropylene crystallized at high temperature. Effect of molecular weight
Authors: Tanaka Hiroshi , Inoue Yoshinori 
Published: April 2007

AbstractThe temperature dependence of 1H spin‐lattice, T1(H), and spin‐spin, T2(H), relaxation times of isotactic polypropylene with relatively low molecular weight, M̄w = 1.95 × 105, and ultra‐high molecular weight, M̄w = 1.78 × 106, crystallized at high temperature (155° C) for a long time (200 h), was measured with a broad line pulse spectrometer. T1(H) for the ultra‐high molecular weight sample is shorter than that for the low molecular weight sample, while T2(H) for the ultra‐high molecular weight sample is longer than that for the low molecular weight sample. From the analysis of free induction decay (FID), three components of T2(H), i.e. T2c(H), T2m(H) and T2a(H), were obtained. These relaxation times are associated with the crystalline, intermediate and amorphous regions, respectively. Here the intermediate regions are the regions in which chain molecules have intermediate mobility between that of crystalline and amorphous regions. A decrease in signal intensity of methylene, methine and methyl carbons was measured as a function of delay time following a 90° pulse before cross‐polarization. From the slope of a log (intensity) versus t2 plot a relaxation time associated with rigid regions of proton nuclei, T2r(H), was obtained, where the rigid regions are the regions in which cross‐polarization occurs easily. The value of T2r(H) lies between that of T2c(H) and T2m(H), indicating that the intermediate regions act as the rigid regions so far as cross‐polarization is concerned.
Synthesis and thermal transition of side‐chain liquid crystalline polyoxetanes having laterally attached mesogenic group
Authors: Kawakami Yusuke , Takahashi Koji , Nishiguchi Shigeo , Toida Kozo 
Published: April 2007

AbstractSide‐chain liquid crystalline polymers with laterally attached mesogenic group were synthesized. Polymers having polyoxetane main chain were obtained by cationic polymerization, and with polymethacrylate main chain by radical polymerization. Some of the polymers showed nematic phase, and polyoxetanes having mesogen with electron‐withdrawing and electron‐donating groups in the molecule showed a little more discrete mesophase.
Studies on the hydrogenation of alkenes and alkynes using polymer coated silica‐Pd catalysts
Authors: Mathew Joice P. , Srinivasan M. 
Published: April 2007

AbstractPalladium complexes of crosslinked polyacrylamide and poly‐N‐vinylimidazole coated on silica gel have been prepared and used as hydrogenation catalysts for alkenes, dienes and alkynes under ambient conditions. The characterisation of the catalysts, the kinetic and mechanistic aspects of the hydrogenation of a few substrates, the effect of temperature, selectivity and the recycling efficiency of the catalysts are presented. A comparison of their activity is made with other silica supported and silica free polymer‐Pd catalysts.
Kinetic behaviour of permeability of polyethylene membrane to chloroform vapour
Authors: Bajpai U. D. N. , Bajpai A. K. 
Published: April 2007

AbstractThe permeability behaviour of thin polyethylene membrane to chloroform vapour has been studied from the kinetic point of view between 15 and 35 ± 0.5°C. It was found that in the constant rate region, the permeability obeys second‐order reaction kinetics. The activation energy and entropy of activation of the permeability process were found to be 13.81 kcal/deg/mol and 33.74 eu, respectively. The physical nature of the membrane was found to affect the permeability process.
Effecters on human placental alkaline phosphatase activity
Authors: Roig M. G. , Ghaïs N. I. , Burguillo F. J. , Cachaza J. M. , Kennedy J. F. 
Published: April 2007

AbstractA kinetic study has been carried out on the effects of enzyme concentration, protein (human serum albumin) concentration and ionic strength (inorganic and organic sodium salts) on the activity of human placental alkaline phosphatase in solution. The activity is depressed by serum albumin, and the corresponding complex of the protein with the substrate, decreasing its concentration available for catalysis, is responsible for an effect similar to competitive inhibition of the alkaline phosphatase activity. Activating and inhibiting effects were found for inorganic anions, respectively.
Monoalkylitaconates–vinylpyrrolidone copolymers. 2. Reactivity ratios and viscometric behaviour in dilute solutions
Authors: Radić Deodato , Opazo Alejandra , Vildósola Gonzalo , Gargallo Ligia 
Published: April 2007

AbstractCopolymerization of mono‐n‐decyl and mono‐n‐decyl and mono‐n‐dodecyl itaconate with vinylpyrrolidone (MOI‐VP, MDI‐VP and MDoI‐VP) was carried out using AIBN as initiator. The monomer reactivity ratios were determined by the Fineman‐Ross and Kelen‐Tüdös methods. Values of r1 and r2 were found to be less than unity for MOI‐VP, MDI‐VP and MDoI‐VP, corresponding to random copolymers with some tendency to alternance. Copolymers of various compositions were studied in solution, and Mark‐Houwink‐Kuhn‐Sakurada relationships were established in ethanol for MOI‐VP and MDI‐VP copolymers, and in 1‐propanol for MDoI‐VP. The rigidity factors s̀ and the characteristic ratio C∞ were obtained from Kθ values determined by using the Stockmayer‐Fixman relation. In all the copolymers the introduction of vinylpyrrolidone units produces flexibility of the polymer chain relative to the poly(monoitaconate) homopolymers, and the solution properties of these copolymers can be described by assuming a random coil model instead of a rigid rod or wormlike model as in poly(monoitaconates).
Optical activity measurements on solids. 3. Non‐optically active synthetic polymers
Authors: Xi Fu , Bartus Jan , Vogl Otto 
Published: April 2007

AbstractMeasurements of the non‐existence of optical activity in suspensions of synthetic optically inactive polymer powders were made to evaluate the limitation of our measurement technique. A particle size of less than 150μm was necessary to obtain accurate measurements. A high degree of crystallinity interfered with the measurements and gave erratic results. In all cases, for various types of commonly used polymers, the optical activity measurements with a zero value for optical rotation demonstrated that reliable measurements could be made with an accuracy of about ±3%.
Solution properties of poly(fluorostyrene‐co‐chlorostyrene) copolymers. II. High‐performance gel permeation chromatography
Authors: Segudovic Nikola , Vukovic Radivoje , Kuresevic Vjera , Karas Frank E. , Macknight William J. 
Published: April 2007

AbstractThe molecular weight distribution of random, unfractionated copolymers of ortho‐ and para‐fluorostyrene and ortho‐ and para‐chlorostyrene were determined. Good agreement was obtained between average molecular weights determined by absolute methods (light scattering and osmometry) and those determined by high‐performance gel permeation chromatography and a universal calibration procedure. The measurements were carried out in tetrahydrofuran at room temperature by using the following relationships between intrinsic viscosity [η] and weight‐average molecular weight M̄w.
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Thermal properties of a tough, new semicrystalline polyimide
Authors: Chalmers Tammy M. , Zhang Anqiu , Shen Dexing , Lien Shawn Hsun‐Shan , Tso Chung C. , Gabori Patricia A. , Harris Frank W. , Cheng Stephen Z. D. 
Published: April 2007

AbstractThermal properties of a new semicrystalline polyimide synthesized from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and 2,2‐dimethyl‐1,3‐(4‐aminophenoxy)propane (DMDA) have been studied. Heat capacities in the solid and liquid states of BTDA‐DMDA have been measured. The heat capacity increase at the glass transition temperature (Tg = 230°C) is 145 J/°Cmol for amorphous BTDA‐DMDA. The equilibrium heat of fusion of the BTDA‐DMDA crystals has been obtained using wide‐angle X‐ray diffraction and differential scanning calorimetry measurements, and is 75.8 kj/mol. Based on the information on crystallinity and the heat capacity increase at Tg, a rigid amorphous fraction is identified in semicrystalline BTDA‐DMDA samples, which represents an interfacial region between the crystalline and amorphous states. In particular, this fraction increases with the crystallinity of the sample, which should be associated with crystal sizes, and therefore with crystal morphology. It has also been found that this polymer has a high‐temperature crystal phase upon annealing above its original melting temperature. The thermal degradation activation energies of BTDA‐DMDA in nitrogen and air are determined to be 154 and 150kJ/mol, respectively.
Properties of epoxy resin cured by phenol novolac/4‐hydroxyphenylmaleimide polymer blend hardeners
Authors: Matsumoto Akihiro , Hasegawa Kiichi , Fukuda Akinori , Pae Jong‐Se 
Published: April 2007

AbstractPhenol novolac/4‐hydroxyphenylmaleimide (HPMI) homopolymer (PHPMI) blends or phenol novolac/HPMI‐styrene copolymer (HPMI‐St) blends were used as the hardener of epoxy resins. Curing behaviour of the above systems and thermal and mechanical properties of the cured epoxy resins were studied. It was not necessary to use a curing accelerator for this system because PHPMI or HPMI‐St had an accelerating effect on the curing reaction. Curing behaviour was investigated by measurement of gelation time(JIS K 6910) and differential scanning calorimetry thermogram (JIS K 7122). Test pieces made from neat resins and from reinforced resins with glass fibre or fused silica were evaluated in terms of thermal and mechanical properties, respectively. It was found that the heat resistance and the mechanical properties improved with increase of PHPMI or HPMI‐St content in the hardener.
Studies on thermal stability and behaviour of polyacetal and thermoplastic polyurethane elastomer blends
Authors: Kumar G. , Mahesh L. , Neelakantan N. R. , Subramanian N. 
Published: April 2007

AbstractThe influence of thermoplastic polyurethane (TPU) elastomer on the rigidity of polyacetal (polyoxymethylene, POM) was studied by determining heat deflection temperature (HDT). The higher the content of TPU in the POM/TPU blend, the lower the HDT of the blend, as would be expected. A comparative study of the recycle capability of POM and the blends was carried out by measuring melt flow index (MFI) on each successive extrusion. Stress‐strain behaviour of the virgin material and that obtained after fourth‐time extrusion was analysed for POM and the blends. The effect of γ‐radiation on the mechanical behaviour of the blends was investigated. The kinetics of thermal degradation of POM, TPU and their blends was studied. The kinetic parameters, viz. activation energy and the order of reaction, were established. The values of the activation energy of the blends were found to be higher than those of the POM and TPU, indicating improved stability of the resultant blends.
Distribution of surfactants in poly(2‐ethyl hexyl methacrylate) latexes
Authors: Kientz E. , Danicher L. , Lambla M. , Holl Y. 
Published: April 2007

AbstractThe adsorption characteristics of four surfactants were studied: sodium dodecyl sulfate (SDS), hexadecyl trimethylammonium bromide (HTAB), hexadecyl pyridinium chloride (HPCI) and ethoxylated nonyl phenol containing 10 segments of ethylene oxide (NP10) in poly(2‐ethyl hexyl methacrylate) (P2EHMA) latexes. Areas per molecule at the particle‐water interface (at the critical micellar concentration) were determined as well as the compacities of the adsorbed layers and the Helmholtz free energies of adsorption (Δμ°). The order of increasing Δμ° is NP10<HTAB, HPCI<SDS. This later result provides valuable information on the rate of surfactant desorption during the latex film formation. The repartition of the surfactant in the latex, mainly between the aqueous phase and the particle‐water interface, was quantitatively determined. The main results presented here will be used in a subsequent article dealing with the interpretation of the distribution of surfactants in latex films.