bluuebunny/crossref_metadata_2025_split huggingface dataset:
Emulsion polymerization kinetics and its reactor design. II. The MWD behavior in isothermal batch operation
Authors: Lin Chen Chong , Chiu Wen Yen 
Published: April 2003

AbstractThe emulsion polymerization of styrene in an isothermal batch operation can be divided into three stages, and the corresponding kinetic rate equations are obtained from the experimental conversion‐reaction time curve. The course of polymerization between the beginning of the reaction and any subsequent time is successfully computed for the reaction rate, the MWD, and the average degree of polymerization using the intergrals of these rate equations, which could readily explain the behavior of the emulsion polymerization. A comparison is made between the theoretical results and the experimental data. Both the theoretical treatment and the experimental data predict that the MWD for a typical emulsion polymerization is characterized by the rapid decrease in Mw/Mw ratio at the entrance of the zero‐order stage and a gradual increase in the first‐order stage regardless of an autoacceleration effect. An autoacceleration effect in the first‐order stage is, however, evidence for a typical emulsion polymerization.
Energy balances and uniaxial failure of solid propellants
Authors: Lepie A. H. , Adicoff A. 
Published: April 2003

AbstractA simple test procedure was used to determine the total damage in a propellant that accumulates during a tensile test from 0% strain to failure. Damage energies of two propellants were measured at various temperatures and straining rates, and Williams‐Landel‐Ferry shift procedures were applied to the results. The reduced master curves for the total damage energy at failure are used to compare the failure behavior of the two propellants.
A quantitative treatment of particle size distributions in emulsion polymerization
Authors: Sundberg Donald C. 
Published: April 2003

AbstractA quantitative analysis is presented for predicting the particle size distributions obtained in emulsion polymerization. The results obtained are compared with experimental data in terms of the particle‐size‐distribution curves as well as the statistical parameters of the distributions. Comparisons are made for changes in initiator level, surfactant level, water:monomer ratio, and temperature. The manner in which these variables change the distributions and the reasons for these changes are identified. The distribution of radicals among particles of different sizes is seen to be significant. Large particles are expected to contain a greater number of radicals per particle than the smaller ones in the same latex. The effects of such a radical distribution upon the properties of the latex are discussed.
Production of levoglucosan and glucose from pyrolysis of cellulosic materials
Authors: Shafizadeh Fred , Furneaux Richard H. , Cochran Todd G. , Scholl Jackson P. , Sakai Yoshio 
Published: April 2003

AbstractVacuum pyrolysis of cellulose within the temperature range of 300–500°C provides a tar fraction containing mainly levoglucosan and glucose condensation products. It was found that pyrolysis proceeds at a much faster rate at the higher temperatures without detrimental effect on the yields. At 400°C the reaction was essentially complete within 3 min yielding a tar that contained 39% levoglucosan and, upon mild acid hydrolysis, gave 49% D‐glucose. The yields could be further improved by washing or treatment of cellulosic substrates with acids. Cotton hydrocellulose provided up to 58% levoglucosan or 77% D‐glucose. This is the highest yield determined by unequivocal methods. Commonly available cellulosic materials such as wood and newsprint give very poor yields of levoglucosan. However, the yields could be improved substantially by acid washing or prehydrolysis to the extent that pyrolysis of these substrates may become an attractive industrial process. The data in this report provide the technical basis for such a process and resolve the existing controversies on the reported yields.
Kinetics and mechanism of the alkali‐catalyzed p‐cresol–formaldehyde reaction
Authors: Malhotra H. C. , Kumar Vinod 
Published: April 2003

AbstractThe kinetics of the reaction of p‐cresol with formaldehyde in relation to the functionality of p‐cresol using NaOH as catalyst has been studied at temperatures of (65 ± 0.05)°C, (70 ± 0.05)°C, (75 ± 0.05)°C, and (80 ± 0.05)°C. The pH maintained was 7.0, 8.0, 9.0, 9.4, and 10.0. The reaction follows a second‐order rate law. The rate was found to increase with increase in pH. The stepwise rate constants (k1 and k2) for the formation of monomethylol‐p‐cresol and dimethylol‐p‐cresol, respectively, were calculated from the overall rate constant k. The values of Arrhenius parameters and the entropy of activation for the overall as well as the stepwise reactions were calculated. The experimental and calculated values of k at pH 10.0 and temperatures 65, 70, 75, and 80°C were found to agree well within experimental errors. A mechanism conforming to the energies and entropies of activation of the reaction is suggested.
“Dry latex.” A new method for the preparation of rubber‐filler powders
Authors: Caspary R. , Heske J. 
Published: April 2003

AbstractA new method of preparing rubber powders, especially masterbatch powders, is described. It consists of the dispersion of polymer latices in highly hydrophobic fine particle‐size powders such as special silicas and carbon black, followed by drying. During the whole procedure the powders never lose their pourable state. Several powder properties, e.g., particle size distribution, pourability, bulk density, and angle of repose, are dealt with for NR and SBR powders. These powders require a high shear processing stage to disperse the black and rubber chemicals into the rubber matrix. For direct extruder feeding, a highly efficient extruder mixing screw is necessary. It is shown that the powders can be sufficiently protected against aging by use of special antioxidants. The procedure is characterized by an outstanding simplicity in respect to engineering and equipment. The future outcome of the method will depend on the balance between that simplicity and the energy demand which can be tolerated.
Vulcanization of butyl rubber by p‐quinone dioxime dibenzoate
Authors: Gan L. M. , Chew C. H. 
Published: April 2003

AbstractThe maximum crosslink density for the dioxime‐butyl vulcanizate was obtained at equimolar quantity of the dioxime and red lead. The formation of each quinoid crosslink required about 1.25 molecule of p‐quinone dioxime dibenzoate. The vulcanizates consisted mainly of the anil‐type crosslink. It was estimated that about 20% of the combined dinitro compounds was wasted in the form of the pendent groups. The vulcanization mechanisms are also discussed.
Preparation and characterization of poly(methyl methacrylate)–lead silicate composites
Authors: Rabie A. M. , Moustafa A. B. , Badran A. S. 
Published: April 2003

AbstractPoly(methyl methacrylate)–lead silicate composites were prepared with different amounts of crystalline or amorphous PbO–SiO2 binary composition (70 mole % PbO). The polymerization reaction was carried out in aqueous medium and in methanol–water mixture at 40°C using sodium bisulfite as initiator. The presence of lead silicate was found to increase the molecular weight of the poly(methyl methacrylate). The prepared composites were characterized by studying their shielding properties to γ radiation, mechanical hardness, dielectric constant, and thermal stability. It was found that lead silicate increases the absorbing power of the composites to γ radiation. This behavior was found to be dependent on the amount and the type of lead silicate (amorphous or crystalline). Gamma irradiation of the composites was found to cause chemical degradation of the poly(methyl methacrylate) leading to a decrease in mechanical hardness. Molecular weights of the poly(methyl methacrylate) for some of the composites were determined before and after irradiation viscosimetrically. Dielectric constants for some of the composites were determined at two different temperatures. The thermal stability of the composites was studied by means of an automatic thermogravimetric analyzer.
Recoverable compliance behavior of high‐density polyethylenes
Authors: Plazek Donald J. , Raghupathi N. , Kratz Robert F. , Miller William R. 
Published: April 2003

AbstractEight samples of high‐density polyethylene with weight‐average molecular weights ranging from 5.5 × 104 to 17.3 × 104 have been studied. In addition to GPC molecular weight characterization, the recoverable compliance, the shear viscosity, and the extrudate swell were determined at temperatures between 138 and 200°C. The range of the maximum creep stresses ranged from 60 to 1840 dynes/cm2. The creep recovery response was in the linear or near‐linear range. The results are interpreted in the light of the anomalous results of Mendelson and Finger.
Ethylene solubility and diffusion in low‐density polyethylene and ethylene copolymers
Authors: Beret S. , Hager S. L. 
Published: April 2003

AbstractEvolution rate measurements were conducted to determine the solubility and the diffusion constants of ethylene in three semicrystalline polymers: low‐density polyethylene (LDPE), ethylene‐ethyl acrylate (EEA), and ethylene–vinyl acetate (EVA) copolymers. The apparatus for such measurements utilizes a flame ionization detector interfaced to a computer for continuous monitoring of the ethylene evolution from the polymer pellets. Solubilities are obtained by calculating the total ethylene evolved over a 12–48‐hr period. Analysis of the evolution rate data in terms of the nonsteady‐state diffusion equation for spheres yields the diffusivity. The ethylene solubility and diffusion constants in EVA and EEA are very similar to those in LDPE. This is due to compensating effects of decreased crystallinity and increased cohesive energy density with the incorporation of bulky polar groups into the polymer chain.
Thermogravimetric and mass‐spectrometric study of the thermal decomposition of PBCT resins
Authors: Thomas T. John , Krishnamurthy V. N. , Nandi U. S. 
Published: April 2003

AbstractThe thermal decomposition of three commercial samples of carboxy‐terminated polybutadiene (PBCT) resins was studied by thermogravimetric analysis (TGA) at heating rates varying from 2° to 100°C/min. Kinetic parameters of the decomposition process at different heating rates were evaluated by means of the Fuoss method.1 The decomposition process and the activation energy values are found to be dependent on heating rate. Mass‐spectrometric analysis of the decomposition products shows that the pyrolysis products of PBCT resins are mainly low molecular weight hydrocarbons: ethylene, acetylene, butadiene, propadiene, vinylcyclohexene, etc. The rates of evolution of these hydrocarbon products vary with the carboxy content of the PBCT resin. Based on this, a carbonium ion mechanism has been suggested for the thermal decomposition. The data generated from this work are of importance for a consideration of the mechanism of combustion of composite solid propellants based on PBCT binders.
Graft polymerization of acrylamide and 2‐acrylamido‐2‐methylpropanesulfonic acid onto starch
Authors: Fanta George F. , Burr Robert C. , Doane William M. 
Published: April 2003

AbstractMixtures of acrylamide and 2‐acrylamido‐2‐methylpropanesulfonic acid (AASO3H) were graft polymerized onto starch by cobalt‐60 irradiation, and the water absorbency and water solubility of the resulting products were determined. The conversion of monomers to polymer was nearly quantitative when pregelatinized wheat starch and a water solution of the two monomers were simultaneously irradiated (simultaneous irradiation conditions). Products with high water absorbency were obtained with equal weights of starch and total monomers when acrylamide:AASO3H ratios ranged from 9:1 to 1:3. Water solubility of these polymers was over 50%. Neither of the two monomers gave absorbent polymers when graft polymerized individually onto starch. Although highly absorbent products were also obtained at a total monomer:starch ratio of 2:5, ratios of 1:5 and lower gave products with poor absorbency. Neutralization of AASO3H with sodium hydroxide before graft polymerization drastically reduced both the water solubility and absorbency of the final products. A reaction with granular starch was also carried out under simultaneous irradiation with a total monomer:starch ratio of 2:5 and with equal weights of the two monomers. Conversion of monomers to polymer was once again nearly quantitative. To obtain good water absorbency from this granular product, it was necessary to first neutralize the AASO3H portion with alkali, then disperse the polymer in hot water, and finally dry the resulting water dispersion. Graft copolymers with good water absorbency were also obtained by adding preirradiated starch to a water solution of acrylamide and AASO3H, although only partial conversions of monomers to polymer were realized. Selected products from the various graft polymerizations were fractionated by extraction with either water or a 1% solution of sodium chloride. The synthetic polymer content of the resulting fractions and the percentage of AASO3H in the synthetic portion of each polymer were determined. The Mn of some of the synthetic polymers was also determined after removal of carbohydrate by enzymatic hydrolysis.
Structure and properties of o‐carboxymaleanilic polyester resins
Authors: Messiha N. N. , Nosseir M. H. , El‐Hamouly S. H. 
Published: April 2003

AbstractPolyester resins were prepared by the reaction of o‐carboxymaleanilic acid with ethylene trimethylene, propylene, hexamethylene, diethylene, or 1,4‐butenediol. All the polyester resins obtained have been characterized and were found to cure with styrene, except the polyester from diethylene glycol. The properties of the cured products in the form of films were determined. Infrared. UV, and NMR spectroscopy were used for both qualitative and quantitative analyses of the polyester resins and their hydrolyzate products, after curing with styrene.
The kinetics of hydrolytic polymerization of ε‐caprolactam. II. Determination of the kinetic and thermodynamic constants by least‐squares curve fitting
Authors: Tai Kazuo , Teranishi Hiroichi , Arai Yoshihiro , Tagawa Takashi 
Published: April 2003

AbstractThe kinetic and thermodynamic constants of the hydrolytic polymerization of ∂‐caprolactam were determined by least‐squares curve fitting. The calculations were carried out using observed kinetic data such as concentration of ∂‐caprolactam ([CL]), endgroup ([EG]), and ∂‐aminocaproic acid ([ACA]) and time derivatives of each concentration (rates) ∂[CL]/∂t, ∂[EG]/∂t, and ∂[ACA]/∂t. The sets of the converged constants are obtained for the initial water concentrations of 0.42, 0.82, and 1.18 mole/kg. An averaged set of the constants applicable for this range of the initial composition was also evaluated. The compatibility between observed and calculated concentration and rate curves was improved by the use of the newly developed sets of the constants. The mechanism of the polycondensation reaction is also discussed, based on the rate and kinetic constants obtained by this work.
Effect of temperature on the electrical conductivity of poly(vinyl chloride)–copper composites
Authors: Bhattacharya Swapan K. , Basu S. , De Sadhan K. 
Published: April 2003

AbstractEffect of temperature on the electrical conductivity of PVC‐copper composites has been studied. The temperature coefficient of dc resistivity of composites with fillers containing negligible oxide content in the range of 77–303 K is positive, indicating metallic‐type conduction. The temperature coefficient of dc resistivity of composites with fillers containing intermediate level of oxide at higher temperatures is negative, indicating a semiconducting behavior. Plots of log conductivity versus log frequency for composites in the insulating region show the hopping‐type conduction.
Radiation‐induced polymerization of ethylene in pilot plant. IV. Kinetic analysis
Authors: Watanabe Hiromasa , Machi Sueo , Kurihara Hirondo , Wada Takeshi , Yamaguchi Kouichi , Watanabe Terutaka , Takehisa Masaaki 
Published: April 2003

AbstractThe kinetics of the radiation‐induced polymerization of ethylene in a flow system using tert‐butyl alcohol aqueous solution as a medium were studied. The polymerization was carried out in a large‐scale pilot plant with a 50‐liter central source‐type reactor at various mean residence times and does rates under constant pressure of 300 kg/cm2, temperature of 30°C, and ethylene molar fraction of ca. 0.4. The reaction mixture in the reactor was back‐mixed flow from the residual polymer concentration in the reactor. The results of the polymerization were analyzed by kinetic treatment based on a reaction mechanism with both first‐and second‐order terminations for the propagating radical. The apparent rate constants, except for that of second‐order termination (kt2), were consistent with those determined by small‐scale batch experiments. The kt2 is 20 to 40 times larger than that in the batch experiments. The kt2 increases with decrease in mean residence time and with agitation, probably because of mobility of the propagating radical.
The molecular factors affecting the solubility parameter
Authors: Peiffer Dennis G. 
Published: April 2003

AbstractA study of the solubility parameter δ2 was pursed in order to obtain further information on the prominent molecular factors affecting its value. The details of the expressions derived for the components of δ2 depends on the considerable usage of both classical statistical thermodynamics and the well‐know equations for intermolecular forces. The results confirm that relatively simple expressions for the components of δ2 are found. The disperson component of the solubility parameter, δ2d, is a function of the molecular polarizability, fractional polarity, molar volume, and van der Waals volume. The polar component of the solubility parameter, δ2p, is a function of the dipole moment, temperature, molar volume, and van der Waals volume; δ2d is found to increase linearily with molecular size, while δ2p is found to decrease with molecular size (except at low molecular volumes). As will be shown, the expressions derived here have considerable utility in elucidating results obtained by other researchers.
Dyeing of chemically modified cellulose. VII. Dyeability of cellulose bearing aromatic amino, nitro, and acrylamidomethyl groups
Authors: Hebeish A. , Waly A. , Moursi A. Z. , Mohdy F. A. Abdel 
Published: April 2003

AbstractThe effect of introducing aromatic amino, nitro, and acrylamidomethyl groups in the cellulose molecules on the dyeing properties of two direct dyes (Chlorantine Fast Red 6BLL and Solophenyl Orange T4RL) as well as two reactive dyes, (Procion Brilliant Red M5B and Procion Brilliant Orange MG) was investigated. The extent and rate of dyeing for cellulose bearing aromatic amino groups were lower than those of nonmodified cellulose irrespective of the dye used. In addition, the extent of dyeing decreased as the amount of aromatic amino groups increased. The opposite held true for cellulose bearing acrylamidomethyl groups, particularly with direct dyes where increasing these groups caused a substantial enhancement in the dye uptake. On the other hand, subjecting cellulose to nitration reaction prior to dyeing diminished significantly its dyeability with the dyes.
The properties of some poly(arylene ether sulfones)
Authors: Ahmed I. K. , Walker N. , Parsons I. W. , Haward R. N. 
Published: April 2003

AbstractSome 2,4′‐substituted poly(arylene ether sulfones) have been prepared and their properties compared with those of the conventional 4,4′ homopolymer. The introduction of the comonomer leads to a small increase in yield stress and to a greater tendency to brittle fracture, which can be demonstrated from fracture surface micrographs.
Permeability of oxygen through polymers. II. The effect of humidity and film thickness on the permeation and diffusion coefficients
Authors: Petrak K. , Pitts E. 
Published: April 2003

AbstractThe values of the permeability coefficient P (cm2/sec) and the diffusion coefficient D (cm2/sec), of oxygen in some water‐soluble polymers at various values of relative humidity were determined. The amount of oxygen initially present in the polymer membranes was calculated. The effect of sample preparation and the film thickness on the transport parameters was investigated. The results confirm the possible effect of thickness on the rate of transport of oxygen in water‐soluble polymers.
Molecular weight characterization of polybutadiene rubber with high molecular weight and broad molecular weight distribution
Authors: Ambler M. R. 
Published: April 2003

AbstractFollowing the molecular weight characterization of two polybutadiene samples, it was found that Mw from gel permeation chromatography with universal calibration and light scattering were in agreement, but Mn by gel permeation chromatography was less than Mn from membrane osmometry. A more detailed analysis revealed that the high molecular weight and broad molecular weight distribution of the two samples forced two corrections to the membrane osmometry results for (a) diffusional layer effects caused by high solution viscosities, and (b) solute permeability of the membrane. In the latter effect, the high viscosities of the solutions prevented actual diffusion through the membrane, but “reflection” of these species as defined by the Staverman coefficient prevented an accurate Mn determination. After making these corrections, it was found that Mn from membrane osmometry using a very tight membrane was in very good agreement with Mn from gel permeation chromatography. A method is demonstrated for obtaining Mn from a combination of membrane osmometry and gel permeation chromatography, where membrane osmometry data from membranes of different porosities (after corrections for diffusional layers and membrane reflection) are used to verify the accuracy of the gel permeation chromatography data as representing the true molecular weight distribution, allowing the gel permeation chromatography data to be used to calculate Mn.
ESR study of the effect of ferric chloride on the photodegradation of model compound for polypropylene
Authors: Negishi Akio , Ogiwara Yoshitaka 
Published: April 2003

AbstractIn our previous article on the photodegradation of polypropyle (PP), the effect of ferric chloride (FeCl3) accelerating the formation of peroxy radical and depressing the formation of alkyl radical were reported. In the present article, the influence of FeCl3 on model compounds of PP was examined using electron spin resonance (ESR) spectrometry. The following compounds were employed as models of PP, including its irregular structures: 2‐methylpentane (2‐MP), 2,4‐dimethylpentane (2,4‐DMP), 2‐methyl‐4‐pentanone (2‐M4P), 2,6‐dimethyl‐4‐heptanone (2,6‐DM4H), 2‐methyl‐1‐pentene (2‐M1P), and tert‐butylhydroperoxide (t‐BuO2H). FeCl3 accelerated the formation of alkyl radicals for 2‐MP and 2,4‐DMP, alkyl and acyl radicals for 2‐M4P and 2,6‐DM4H, and alkyl radicals for 2‐M1P. As no definite effect of FeCl3 was observed for n‐pentane and 2‐octanone, FeCl3 was assumed to attack saturated hydrocarbons, ketones at a tertiary carbon‐hydrogen bond, and hydrocabons at an allylic hydroge, leading to easier photodegradations. FeCl3 was also effective for the photodegradation of t‐BuO2H using λ >300 nm, so that FeCl3 is believed to contribute also to the photodegradation of PP under the same irradation conditions. The catalytic effect of FeCl3 in photodegradation seems to origirate in a redox reaction.