bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal oxidation of fractionated polypropylene in solution
Authors: Osawa Zenjiro , Saito Takashi , Kimura Yuji 
Published: April 2003

AbstractThermal oxidation of fractionated polypropylene was carried out in trichlorobenzene under atmospheric oxygen at 125°C with conventional oxygen uptake. The oxidizability of the polymers is discussed on the basis of the oxygen uptake curves and the properties of the polymers. Fractions of atactic polypropylene oxidized easily at the initial stage of the oxidation and showed neither autoxidation phenomena nor the induction period observed in the isotactic polymer. Hydrogenation of the ether‐soluble fraction by a Wilkinson catalyst gave a polymer which was, according to infrared spectrometry, free from impurity groups such as hydroperoxide, carbonyl, and unsaturation groups. The hydrogenated fraction was more stable to thermal oxidation than the unhydrogenated fraction and showed an induction period. The results indicate that the initiation process of the oxidation of polypropylene is apparently dependent on the impurities such as hydroperoxide, carbonyl, and unsaturation and that stereoregularity of the polymer affects the kinetic dependence of the oxidation.
Liquid exclusion chromatography. A technique for monitoring the growth of polymer particles in emulsion polymerization
Authors: Singh S. , Hamielec A. E. 
Published: April 2003

AbstractAn experimental investigation of the growth of polymer particles in the emulsion polymerization of styrene and of vinyl acetate is reported. The growth of polymer particles in the size range of 200–6500 Å was monitored by liquid exclusion chromatography (LEC). This relatively new analytical technique permits very rapid analysis for particles as small as 200 Å and should prove extremely useful as an online monitor of polymer particle size for the control of latex reactors.
Reverse osmosis with dynamically formed membranes from water‐soluble polymers
Authors: Igawa M. , Senō M. , Takahashi H. , Yamabe T. 
Published: April 2003

AbstractMembranes were dynamically formed from poly(acrylic acid), poly(1‐methyl‐2‐vinylpyridinium iodide), and methylcellulose on a Millipore filter. The effects of the conditions of membrane formation on reverse osmosis performances and the membrane structure were investigated. The primary factors that affect membrane performance were ascertained to be the kind and concentration of salts and the pH of the preparing solutions, the concentration and the polymerization degree of the membrane materials, the pore size of filters, and the pressure and circulation velocity during membrane formation. Two types of dynamically formed membranes, the membranes inside the filter and the membranes on the filter, were distinguished.
Effects of molecular weight distribution and long‐chain branching on the viscoelastic properties of high‐ and low‐density polyethylene melts
Authors: Han Chang Dae , Villamizar Carlos A. 
Published: April 2003

AbstractUsing the Han slit/capillary rheometer, rheological measurements were taken of several commercially available low‐ and high‐density polyethylene melts, namely, three low‐density polyethylene samples of Chemplex Corp. (CX 1005, CX 1016, and CX 3020), three low‐density polyethylene samples of U.S. Industrial Chemicals Co. (NA 205, NA 244, and NA 279), two high‐density polyethylene samples of Union Carbide Corp. (DMDJ 5140 and DMDJ 4306), and two high‐density polyethylene samples of Mitsui Petrochemical Industries, LTD. Molecular characterization of these samples was carried out by the resin suppliers. The rheological measurements included (1) entrance pressure drop, (2) exit pressure, (3) pressure gradient, (4) die swell ratio. These then permitted us to determine the shear viscosity and normal stress differences. The rheological measurements were interpreted to identify the effects of long‐chain branching and molecular weight distribution on the rheological properties of polyethylenes in the light of the existing molecular viscoelasticity theories. It was found that fluid elasticity is greater for polymers having a broader molecular weight distribution and that, for polymers having more long‐chain branching, viscosities are lower while elasticities are higher.
Settling behavior of fillers in thermosetting epoxy casting resins during cure
Authors: Fukushima Jiro , Yasuda Kazuo , Teratani Hiroshi , Nishizaki Shunichiro 
Published: April 2003

AbstractUsing a theory based on a modified Stokes' law equation, the settling behavior of fillers was investigated (glass beads and silica powder) in thermosetting epoxy casting resins during cure. In this study a suspension (a thermosetting epoxy casting resin) containing a large amount of filler particles is assumed to be a homogeneous fluid, and the settling phenomena are treated such that one or more particles of the filler settle into the homogeneous fluid under gravity without interference from other particles. The viscosity increase of the fluid during cure is taken into consideration. The experimental results agree well with the theoretical predictions when the settling distances are small and the particle size distribution is narrow. When these conditions are not satisfied, various effects are observed such as convection, filtering, combination, bottom effect, and a broad particle size distribution. In addition, the formation of a compression zone and of a compaction zone are clearly observed.
Pressure drop through tapered dies
Authors: Lenk R. S. 
Published: April 2003

AbstractA simple method is presented for calculating the pressure drop for the flow of power law liquids in dies with a wide slit profile and with vertical and/or lateral tapers, as well as in dies with the shape of a circular truncated right cone. Tapered dies are known to give improved extrudate quality and/or higher output rates without encountering extrudate defects which occur in dies with parallel channels at similar extrusion pressures. A possible ultimate optimization of the extrusion process—as far as die design is concerned—is discussed. It is suggested that this be based upon an extension of the method from dies with a rectilinear convergent taper to dies with a curvilinearly converging channel aspect the generation of which latter is indicated.
The kinetics of polyesterification. III. A mathematical model for quantitative prediction of the apparent rate constants
Authors: Lin Chen Chong , Yu Ping Chang 
Published: April 2003

AbstractA mathematical model for the apparent constants k1 and k2 which presents a quantitative explanation of the observed kinetic behavior in both uncatalyzed and acid‐catalyzed polyesterification between ethylene glycol and a dibasic acid in different initial molar ratios was developed. This model consists of two types of similar semiempirical equations, one of which applies to the uncatalyzed reaction and the other to the acid‐catalyzed reaction. They are both based on the same apparent dissociation coefficient, kh, of a dibasic acid in ethylene glycol, which can be expressed as kh = K ear at constant temperature. The symbol a in the equation represents the sensitivity constant to change in the initial molar ratio r = [OH]0/[COOH]0. The value of the true rate constant for polyesterification between succinic acid and ethylene glycol at 195°C was estimated to be 3.02 × 10−3 [in kg2/(equiv. moles)2·min] based on this model.
Poly(methyl methacrylate) membranes
Authors: Sakai Yoshitada , Tanzawa Hiroshi 
Published: April 2003

AbstractUniform and symmetric membranes were formed from poly(methyl methacrylate) (PMMA) by making use of the stereocomplex phenomenon which characteristically occurs in the solution of a mixture of isotactic PMMA and syndiotactic PMMA. The water permeability of the membrane was very high compared to a commercially available cellulosic membrane, whereas their NaCl permeabilities were the same. The permeabilities of the membranes are explained by a simple capillary model. By varying the tacticity of the polymer it was found that the finest membrane structure is formed at the isotactic polymer ratio of ca. 30%. This shows the close relationship between complex formation and membrane permeability.
Utilization of lignins in rubber compounding
Authors: Kumaran M. G. , De Sadhan K. 
Published: April 2003

AbstractLignin in the form of lignosulfonate containing about 33% moisture was found to be dispersible in natural rubber by dry mixing. Properties such as tear resistance, abrasion resistance, flex crack resistance, and crack growth resistance improved upon addition of lignin, irrespective of the nature of filler added. This lignin was found to have negative effects on modulus, tensile strenght, resilience, heat buildup, and compression set, which showed, however, remarkable improvement upon aging.
Controlled drug release by polymer dissolution. I. Partial esters of maleic anhydride copolymers—properties and theory
Authors: Heller J. , Baker R. W. , Gale R. M. , Rodin J. O. 
Published: April 2003

AbstractThe kinetics of drug release from a series of partial esters of vinyl acetate–maleic anhydride has been investigated. These polymers in their un‐ionized forms are hydrophobic and water insoluble, but in their ionized forms they are water soluble. Polymer dissolution is pH sensitive, and different half‐esters have a characteristic pH range above which they are soluble and below which they are insoluble. When films are placed in buffered media, they erode at a constant rate that depends on the pH of dissolution of the polymer and on the pH of the buffered medium. Dissolution of the polymer is limited to the polymer–buffer medium interface, and drugs dissolved or uniformly dispersed in the polymer are released by zero‐order kinetics. A detailed model has been developed that successfully correlates dissolution behavior and various experimental parameters.
Effect of notches and glass fiber reinforcement on fatigue behavior of polycarbonate
Authors: Misaki Toshikazu , Kishi Junji 
Published: April 2003

AbstractIn order to investigate the effect of a notch on the tensile properties of polycarbonate and 30% glass fiber‐reinforced polycarbonate, two types of notched specimens were prepared. These notches were a sharp 60° notch and a dull notch with rounded tip 1.5 mm in radius at the base of the 60° notch. The notches decreased the tensile strength of polycarbonate. The sharp notch reduced tensile strength more effectively than the dull notch. In 30% glass fiber‐reinforced polycarbonate, even the dull notch decreased the tensile strength considerably. Unnotched polycarbonate was subjected to cyclic tensile loading of 104 cycles at 10 Hz, with varying cyclic stress. It was found that the elongation at break decreased rapidly with increase in cyclic stress. The notches considerably decreased the tensile fatigue strengths of polycarbonate and glass fiber‐reinforced polycarbonate in 104 cycles at 10 Hz.
Thermal degradation of polymers. Part XVIII. The synthesis and characterization of quinazolone pre‐polymers
Authors: Chan H. S. O. , Still R. H. 
Published: April 2003

AbstractA series of quinazolone pre‐polymers have been prepared from 4,4′‐diaminodiphenyl‐3,3′‐dicarboxylic acid and aromatic diacetamido compounds by melt polycondensation. The pre‐polymers have been characterized by combustion analysis, viscometry, vapor pressure osmometry, and thermal analytical methods (TG, DTA, and DSC). Structures have been elucidated by spectroscopic methods (IR and NMR). The thermal cyclization of these pre‐polymers to the partial ladder polyquinazolone has been studied and optimized using IR, DSC/DTA, TG, and evolved gas analysis. The cyclization behavior of these systems has been resolved in terms of concurrent dehydration and decarboxylation.
Redox‐initiated graft copolymerization onto wool with thiourea as reductant. IV. Grafting of vinyl sulfone dyes onto wool using thiourea–H2O2 redox system
Authors: Hebeish A. , Abdel‐Fattah S. H. , El‐Rafie M. H. 
Published: April 2003

AbstractWool samples were dyed with a vinyl sulfone dye in the presence of thiourea and H2O2 under a variety of conditions. Increasing the H2O2 concentration from 2.5 mmole/l. to 20 mmole/l. caused a significant enhancement in the rate of the dyeing, whereas increasing the thiourea concentration from 1.25 mmole/l. to 10 mmole/l. brought about an increase in the rate of dyeing. Further increase in the thiourea concentration (i.e., up to 15 mmole/l.) caused a significant decrease in the rate of dyeing. Raising the dyeing bath temperature from 30°C to 70°C accelerated appreciably the rate of dye uptake. With respect to dye concentration, complete exhaustion occurred at dye concentrations of 0.5% and 1% (owf) when dyeing was performed at 70°C and pH 6 over a duration of 2 hr. This contrasts with 90% and 55% exhaustion for dye concentrations of 3% and 5% (owf), respectively. The rate of dyeing obtained at different pH's follows the order pH 2 < pH 4 < pH 6 < pH 8. A dye fixation of approximately 68%, 64%, and 50% could be achieved at pH 4, 6, and 8, respectively, if dyeing was performed at 70°C for 2 hr in a bath containing a dye concentration of 3% (owf) in the presence of thiourea (10 mmole/l.) and H2O2 (15 mmole/l.). The mechanism of dyeing is believed to be grafting by vinyl addition to wool radical formed under the influence of the decomposition products of thiourea and H2O2. Evidence of this mechanism is presented.
The influence of nucleation density and cooling rate on crystallization of polyethylene from the melt
Authors: Fraser G. V. , Keller A. , Odell J. A. , Wills H. H. 
Published: April 2003

AbstractDifferent samples of high‐density polyethylene provided different nucleation densities which were assessed by optical microscopy and light scattering. Crystallizations were carried out under controlled cooling rates using a microscope hot stage and DSC from which crystallization temperatures were obtained. It is shown that the effective crystallization temperature is a function of the nucleation density, and a quantitative fit is found with theoretical predictions based on crystallization kinetics. The melting point was, in turn, found to be dependent on nucleation density, through the agency of lamellar thickness as assessed by low‐frequency Raman spectroscopy. The effect of cooling rate on melting point is also explained in terms of variation of supercooling. The implications of these effects together with considerations of surface and interior nucleation and sample size are discussed for the industrial processing of polyethylene.
Instabilities and failure in elongational flow and melt spinning of fibers
Authors: White James L. , Ide Yoshiaki 
Published: April 2003

AbstractA theoretical and experimental study of instability and failure behavior during melt spinning is presented. From an analysis of system dynamics, draw resonance is shown to be a continuous processing analogue of ductile failure. Using viscoelastic fluid mechanics and the White‐Metzner constitutive model, it is shown that melts which exhibit ductile failure in elongational flow tend to show draw resonance in melt spinning. Deformation hardening melts exhibit cohesive fracture in elongational flow and melt‐spinning processes.
Crosslinking and mechanical property of liquid rubber. II. Curative effect of aromatic diols
Authors: Minoura Yuji , Yamashita Shinzo , Okamoto Hiroshi , Matsuo Tadao , Izawa Michiaki , Kohmoto Shun‐ichi 
Published: April 2003

AbstractThe relationships between the properties and structure of polyurethane elastomers derived from hydroxyl‐terminated liquid polybutadiene (HT‐BD), several low molecular weight aromatic diols, and diisocyanates were studied. The curative effects of the diols were examined by such means as tensile properties, dynamic viscoelasticity, x‐ray diffraction, and others. It was found that the properties of the elastomers derived from HT‐BD were greatly affected by the structure of low molecular weight chain extender diol. These results were interpreted by the steric effect, crystallinity, and the concentration of polar groups.
Polymerization mechanisms and molecular weight distribution. II. AIBN‐initiated polymerization of styrene at 60°C
Authors: Braks Jorma G. , Huang Robert Y. M. 
Published: April 2003

AbstractAn experimental study was carried out on the AIBN‐initiated polymerization of styrene at 60°C. The kinetic rate constants were determined by the method of moments and the MWD method, which was proposed in a previous paper. The results compared favorably with the data in the literature and the MWD method was noted to yield more consistent results than the method of moments, which indicates the importance of considering the whole molecular weight distribution. The theoretical MWD was found to approximate the experimental MWD well. The chain‐transfer constant to AIBN was found to be between 0.09 and 0.14.
Mechanical α‐dispersion and interaction in filled polystyrene and polymethylmethacrylate
Authors: Iisaka K. , Yama K. Shiba 
Published: April 2003

AbstractDynamic mechanical properties of polystyrene (PS) and polymethylmethacrylate (PMMA) filled with glass beads and mica flakes have been investigated. The α‐dispersion temperature (Tα) increases with filler content in each system. The increase in Tα is larger for PMMA than for PS in the case of the same filler; the increase in Tα is larger for mica than for glass in the case of the same polymer. Polymer‐filler interaction energies have been estimated from heats of adsorption of the monomers of the filler surfaces determined by solid gas adsorption chromatography. The increase in Tα can be related to the extent of polymer‐filler interaction energy. The thickness of the partially immobilized layer on the filler surface has been estimated to be the orders of 0.1 and 1.0 μm, respectively, for the mica and the glass‐filled systems.
Graft copolymerization of hydrophilic monomers onto irradiated polypropylene fibers
Authors: Sundardi F. 
Published: April 2003

AbstractA method of graft copolymerization of hydrophilic monomers, such as 1‐vinyl‐2‐pyrrolidone, acrylonitrile, acrylic acid, and acrylamide, onto irradiated polypropylene fibers has been studied. γ ray as well as electron beam were employed for the irradiation processes. Graft‐copolymerization kinetics and the properties of grafted fibers have been investigated. Moisture regain, dyes absorption, and melting point of the grafted fibers were found to increase with the increasing of the degree of grafting. Polypropylene for 1‐vinyl‐2‐pyrrolidone grafted fibers showed excellent dye absorption for almost all kinds of dyes such as direct, basic, acid, reactive, disper, and naphthol dyes. However, for polypropylene acrylic acid grafted fibers, the colorfastness to washing was found to be unsatisfactory. The colorfastness to washing for polypropylene 1‐vinyl‐2‐pyrrolidone grafted fibers was found to be fairly good for certain types of dyes such as vat and naphthol dyes.
The preparation and tensile properties of polyethylene composites
Authors: Mead W. T. , Porter Roger S. 
Published: April 2003

AbstractSingle polymer composites have been prepared using different morphologies of polyethylene as matrix and as the reinforcement. Depending on annealing conditions, the ultraoriented fibers used as reinforcement can have higher melting points (ca. 139°C) than the matrix made from the same conventionally crystallized high‐density polyethylene (ca. 132°C) or from low‐density polyethylene (ca. 110°C). The optimum temperature has been assessed for bonding to occur by growth of transcrystalline regions from the melt matrix without considerable modulus reduction of the annealed ultraoriented and reinforcement fiber or film. Pullout tests have been used for determining the interfacial shear strength of these single polymer composites. The interfacial shear strength for the high‐density polyethylene films embedded in a low‐density polyethylene matrix is 7.5 MPa and for high‐density polyethylene self‐composites is 17 MPa. These values are greater than the strength for glass‐reinforced resins. The strength is mainly due to the unique epitaxial bonding which gives greater adhesion than the compressive and radial stresses arising from the differential shrinkage of matrix and reinforcement. The tensile modulus of composites prepared from uniaxial and continuous high‐density polyethylene films embedded in low‐density polyethylene obeys the simple law of mixtures and the reinforced low‐density polyethylene modulus is increased by a factor of 10. High strength cross‐ply high‐density‐polyethylene—low‐density‐polyethylene laminates have also been prepared and the mechanical properties have been studied as the film orientation is varied with respect to the tensile axis.
Radiation‐induced polymerization of water‐saturated styrene in a wide range of dose rate
Authors: Takezaki J. , Okada T. , Sakurada I. 
Published: April 2003

AbstractRadiation‐induced polymerization of water‐saturated styrene (water content 3.5 × 10‐2 mole/liter) was carried out in a wide range of dose rate between 1.2 × 103 and 1.8 × 107 rad/sec, and compared with the polymerization of the moderately dried styrene (water content 3.2 × 10‐3 mole/liter). Molecular weight distribution curves of the polymerization products showed that they were generally consisted of four parts, namely, oligomers, radical, cationic, and super polymers. Contributions of the four constitutents to the polymerization and the number average degrees of polymerization (DP) of the four kinds of polymers were calculated by the graphical analysis of the curves. The rate of radical polymerization and DP of radical polymers are independent of the water content; the dose rate dependences of the polymerization rate and DP agree with the well known square root and inverse square root laws, respectively, of the radical polymerization of styrene. The rate of ionic polymerization is directly proportional to the dose rate, but it decreases, at a given dose rate, inversely proportional to the water content of styrene. DP of ionic polymer is independent of the dose rate but decreases with increasing water content. The super polymer of DP about 104 is not formed in the case of the moderately dried styrene. G values for the initiating radical and ion formation are calculated to be, independently of the dose rate and water content, 0.66 and 0.027, respectively. It was suggested that oligomer was formed in the early stage by the interaction of cation with anion and only those cations which had survived underwent polymerization.
Mechanism and evaluation in electroinitiated copolymerization coatings of acrylonitrile and acrylic acid
Authors: Teng F. S. , Mahalingam R. 
Published: April 2003

AbstractAdherent films of copolymers on different metal surfaces were formed by an electrolytically initiated polymerization of acrylonitrile (AN) and acrylic acid (AA) in 0.05N H2SO4 aqueous solution. The electrolysis was carried out under a constant current. Hydrogen overvoltages for five different metals used as the cathode were measured in order to interpret the nature and quality of the coating. Solutions containing varying volume fractions of AN and containing different electrolytes gave rise to coatings of varying film thickness. Based on the analyses of copolymer compositions, it is believed that the polymer was formed at the cathode by a free‐radical propagation mechanism. The film hardness and the adhesion between the polymer and the metal surface were measured with an Arco microknife. Furthermore, the scanning electron microscope (SEM) was used to examine the structure of the film surface and cross section. The corrosion rates of the coated and uncoated metals in substitute ocean water were also measured for purposes of evaluation of the coatings.