bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solid state polymerization of poly(ethylene terephthalate): Kinetic and property parameters
Authors: Jabarin S. A. , Lofgren E. A. 
Published: April 2003

AbstractThe kinetics of solid state polymerization of poly(ethylene terephthalate) (PET) have been investigated at a variety of conditions. Equations have been developed to describe the relationships of time, temperature, and final molecular weight for PET precursors prepared from specified catalyst and monomer systems. These studies show effects of: time and temperature of solid stating, moisture concentration, oxygen exposure, and nitrogen purge flow rate. Measurements of inherent viscosity, carboxyl end group concentration, melting point, residual acetaldehyde, and acetaldehyde generated during melting are used to monitor molecular weight, purity, and thermal stability of these solid stated resins.
High shear rheology and shear degradation of aqueous polymer solutions
Authors: Buchholz F. L. , Wilson L. R. 
Published: April 2003

AbstractWe have investigated the possibility of replacing hydraulic oils with aqueous polymer solutions having the same rheological properties. We measured the low and high shear rate viscosities of polymer solutions at several moderate concentrations and compared the results to the predictions of a molecular model. We found that viscosities measured at shear rates near 1 million reciprocal seconds are in good agreement with those calculated using the model of Mochimaru.6 Shear degradation studies were also conducted using higher molecular weight versions of some of the polymers. Exposure of these to very high shear rate caused a permanent decrease in viscosity and a corresponding change in the molecular weight and molecular weight distribution. Taken together, these results show that very low molecular weight polymers at moderate concentrations are necessary to formulate an aqueous hydraulic fluid with approximately Newtonian behavior at shear rates near 1 million reciprocal seconds, and without long‐term polymer degradation.
Water immersion of polysulfide sealants. II. An interpretation of the influence of curing systems on water resistance
Authors: Hanhela Peter J. , Huang Robert H. E. , Paul D. Brenton , Symes Theodore E. F. 
Published: April 2003

AbstractDichromate cured polysulfide sealants have superior resistance to swelling in hot water than those cured with manganese dioxide and examinations to identify the reasons for this difference were undertaken. The commercial sealants PR‐1422, PR‐1750, and Pro‐Seal 899 were shown to contain similar types and loading of fillers. Crosslink densities were compared through a procedure involving an oscillating disc cure meter modified to accommodate mobile mixtures. No relationship between stability and crosslinking was observed. Formation of large voids in MnO2‐cured sealants after prolonged immersion at 70–90°C, suggests the formation of a water‐soluble acid which then reacts with the CaCO3 filler, and this was supported by pH measurements. The acid was shown to arise through autoxidation of formal groups in the polysulfide, and this process can be suppressed by radical scavengers (including ammonium dichromate). When PR‐1750 was examined under nitrogen or with carbon black as filler, a similar time–swell curve to that of PR‐1422 was produced. It was concluded that abnormal swell does not result simply from autoxidation: a filler capable of reacting with the acid must also be present.
Electrical conductivity of γ‐irradiated native and mercerized cotton celluloses
Authors: Moharram M. A. , Abou‐Sekkena M. M. , Hakeem Nagwa Abdel 
Published: April 2003

AbstractIn the present study the electrical conductivity (σ) of ball‐milled and NaOH‐treated cotton fibers were measured in vacuum. The induced electrical conductivity and the activation energy ΔE of γ‐irradiated samples were measured as a function of radiation doses and at various temperatures. It was found that γ‐irradiation of cotton fibers either decreases or increases its electrical conductivity. Thus, it was found that γ‐irradiation of cotton reduces the conductivity of the samples having particle sizes ranging from 0.07 to 0.11 mm and the magnitude of the reduction diminishes as the particle size increases. The results have also shown that, for any given concentration, γ‐irradiation of NaOH‐treated samples causes an increase of the measured electrical conductivity.
Heterogeneous styrene–divinylbenzene copolymers. Stability conditions of the porous structures
Authors: Okay Oğuz 
Published: April 2003

AbstractThe change in the porosity of styrene–divinylbenzene (S–DVB) copolymers during drying as a function of the quality of the diluent and of the divinylbenzene (DVB) concentration was investigated after drying the networks from water (maximum porosity) and from toluene (stable porosity). Two different diluents, namely toluene and cyclohexanol, were used in the polymerization system at a fixed volume fraction of the organic phase (0.50). The phase separation in toluene is accompanied by a slight deswelling of the network phase, whereas that in cyclohexanol leads to largely unswollen network phase. The stable porosity increases abruptly over a narrow range of the DVB concentration, i.e., between 40 and 50% DVB in toluene and between 15 and 25% DVE in cyclohexanol. The maximum porosity increases almost linearly with increasing DVB concentration up to a certain value, and then remains constant. The results indicate that the two main factors which determine the physical state of the swollen heterogeneous S–DVB copolymers, as well as the stability of the porous structures, are (1) the critical conversion at the incipient phase separation and (2) the degree of the inhomogeneity in crosslink distribution.
Manufacturing of polypropylene laminates and related structural reorganization in the crystalline phase
Authors: Guerra Gaetano , Rosa Claudio De , Petraccone Vittorio 
Published: April 2003

AbstractThe conditions for obtaining recrystallization in more ordered modifications are described for an uniaxially oriented sample of isotactic polypropylene, annealed with fixed ends. These recrystallization conditions are related to the conditions of a lamination process.
Modification of partially carboxymethylated cotton via crafting with acrylic acid and styrene using gamma radiation
Authors: Hebeish A. , Zahran A. H. , Rabie A. M. , El‐Naggar A. M. Kh. 
Published: April 2003

AbstractPartially carboxymethylated cottons (PCMC) having 15.549, 27.409, and 46.834 meq COOH/100 g cellulose as well as untreated cotton and alkali‐treated cotton, which was prepared in an analogous manner to PCMC but, in the absence of monochloroacetic acid, were graft‐copolymerized with either acrylic acid or styrene using gamma radiation under different conditions. Moisture regain and dyeing properties of the copolymers so obtained were investigated. It was found that the graft yeld increases by increasing monomer concentration and radiation dose irrespective of the monomer or substrate used. Using water/methanol mixtures as polymerization media are advantageous for grafting of styrene onto the substrates in question. The graft yields of PCMCs are much lower than those of unmodified and alkali‐treated cottons when they were grafted with acrylic acid. In case of styrene on the other hand, the graft yields for PCMCs are higher than the corresponding yields obtained with the unmodified and alkali‐treated cottons. Poly(acrylic acid)–PCMC graft copolymers show much higher moisture regain than PCMCs particulary when the carboxylic groups of the graft were in the sodium form. The opposite holds true for polystyrene–PCMC graft copolymers which exhibit much lower moisture regain as compared with PCMCs. The color strength of PCMC dyed with direct or reactive dyes decreases significantly after being copolymerized with poly(acrylic acid) prior to dyeing. On the other hand, this copolymerization improves the affinity of PCMCs for the basic dye and brings about perceptible shade. Polystyrene–PCMC graft copolymers acquire higher color strength than the PCMC when dyed with direct, disperse, and basic dyes but lower color strength upon dyeing with the reactive dye. Also reported were the moisture regain and dyeability of unmodified and alkali‐treated cotton before and after copolymerization with acrylic acid or styrene for comparison.
Sizes of long branches in low density polyethylenes
Authors: Bugada Daniele C. , Rudin Alfred 
Published: April 2003

Abstract13C‐NMR spectroscopy and size exclusion chromatography have been used to determine the mean length of long branches in a number of high pressure process low density polyethylenes (LDPEs). 13C‐NMR analyses count all branches longer than C5 as “long.” The polyethylenes studied all had 2–3 long branches per 1000 carbons. The mean branch length was of the order of 200–300 carbons in length. The size of long branches increases with increasing M̄n of the parent polyethylene, but the size of long branches relative to the overall macromolecular size decreases with increasing M̄n. The mean molecular weight of the long branches is some 5–20% of M̄n of the particular polymer and decreases as M̄n increases. Both autoclave and tubular reactor products were studied.
Glycerol contact angle measurements on exterior and interior surfaces of polyethylene rods: Difference between surface and bulk morphology
Authors: Gupta J. P. , Sefton M. V. 
Published: April 2003

AbstractA difference between surface and bulk morphologies of extruded low density polyethylene (LDPE) has been observed through measurement of the contact angle of glycerol on both exterior and interior surfaces of the extrudate. The sessile drop contact angle on the exterior surface of LDPE rods prepared in a Brabender plasticorder increasea with increasing screw speed (40–180 rpm) and correspondingly increased die pressure at each extrusion temperature (110–130°C). On the other hand, the sessile drop contact angle on the interior surface of LDPE rod, exposed by grinding, decreased with increased screw speed. Qualitative trends were identical with exterior contact angle measured by the Wilhelmy plate method or with the interior surface exposed by fracture. Contact angle variations were interpreted in term of density or crystallinity to suggest that the bulk or interior crystallinity increased with increasing die pressure (even at constant screw speed), while the crystallinity of the exterior decreased with increasing screw speed (even at nearly constant die pressure). The difference between surface and bulk morphologies was consistent with that deduced from DICUP absorption kinetics and optical microscopy [J. Appl. Polym. Sci., 29, 2383 (1984)], although differences were noted in the effect of screw speed on surface morphology.
Surface modification of Egyptian delta titano magnetite ore and its effect on the aqueous polymerization of methyl methacrylate
Authors: Abd‐El‐Hakim A. A. , Badran A. S. 
Published: April 2003

AbstractThe surface modification of Egyptian delta titano magnetite ore (EDTMO) was carried out by adsorption of stearic acid molecules from benzene solution. The adsorption isotherm was found to be one‐step. The modification process affected the sedimentation properties of EDTMO in organic medium. It was found that the maximum stability of EDTMO in organic medium is concerned with monolayer surface formation. The modified EDTMO was found to catalyze the aqueous polymerization of methyl methacrylate and resulted in increasing the viscosity average molecular weights.
Recovery of uranium from sea water. IV. Influence of crosslinking reagent of the uranium adsorption of macroreticular chelating resin containing amidoxime groups
Authors: Egawa Hiroaki , Nakayama Morio , Nonaka Takamasa , Sugihara Eiichi 
Published: April 2003

AbstractMacroreticular chelating resins (RNH) containing amidoxime groups with various degrees of crosslinking were synthesized by using various amounts of ethyleneglycol dimethacrylate (1G), dimethyleneglycol dimethacrylate (2G), triethyleneglycol dimethacrylate (3G), tetraethyleneglycol dimethacrylate (4G), and nanoethyleneglycol dimethacrylate (9G) as crosslinking reagent. The effect of crosslinking reagents on the pore structure, ion exchange capacity, swelling ratio, and adsorption ability for uranium of RNH was investigated. RNH (RNH–1G) prepared by using 1G were showed to have macroreticular structures by the measure of specific surface area. RNH–1G had the high adsorption ability and physical stability. Though RNH (RNH–4G) obtained by using 4G have little macroreticular structure (macropore), these resins showed the high adsorption ability for uranium by the treatment with 0.1 mol dm−3 NaOH at 30°C for 15 h (alkali treatment). These results suggest that the formation of not only the favorable macropore but also the micropore is important for the effective recovery of uranium in sea water, whereas RNH–4G was defined to be low physical and chemical stability. For the preparation of RNH which have effective pore structure for the recovery of uranium, chemical, and physical stability, the simultaneous use of divinylbenzene (DVB) and 1G or 4G as crosslinking reagent was examined (abbreviated as RNH–DVB–1G and RNH–DVB–4G). The specific surface area of RNH–DVB–1G increased with an increase of 1G used. These RNH–DVB–1G have been shown the high adsorption ability for uranium. On the other hand, the specific surface area and adsorption ability for uranium of RNH–DVB–4G decreased with an increase of 4G used. Repeated use did not cause the deterioration of both RNH–DVB–1G and RNH–DVB–4G. This result suggests that the simultaneous use of DVB and 1G or 4G contributed the improvement of chemical and physical stability. In particular, RNH–DVB–1G has the effective macropore and micropore for the recovery of uranium.
Application of chitosan to cobalt recovery: Evaluation by factorial design of experiments
Authors: Blazquez I. , Vicente F. , Gallo B. , Ortiz I. , Irabien A. 
Published: April 2003

AbstractA natural polymer in a commercially available form (chitosan) has been tested using a factorial design of experiments for its application to cobalt recovery either in hydrometallurgy and in analytical separations. A simple mechanically stirred system has been used, evaluating the influence of the contact time, iron(II), cobalt (II), chitosan concentration, salinity, and pH in the separation. The pH value has a dramatic influence on the metal recovery from a negligible amount of metals at pH = 1.0 to a quantitative sorption at pH = 3.0. Linear relationships between sorbed metal and the variables have been determined at constant pH value and a quantitative evaluation of the metal recovery at different pH values can be performed using the maximum sorption capacity of the chitosan (a0) and the selectivity for both metals. The obtained results allow the evaluation of the recovery of metals using chitosan as solid phase.
Unsaturated polyesters. III. Kinetics of polyesterification of cinnamylsuccinic acid with ethylene glycol
Authors: Shaaban A. F. , Salem M. A. , Messiha N. N. 
Published: April 2003

AbstractThe polyesterification reactions of cinnamylsuccinic acid with ethylene glycol in both equimolar and nonequimolar ratios were investigated over the temperature range of 130–180°C in the absence and presence of p‐toluene–sulfonic acid as a catalyst. The kinetic equations were: −d[COOH]/dt = k1[COOH][OH]2 and −d[COOH]/dt = k2[COOH]2 for uncatalyzed and acid‐catalyzed polyesterification reactions, respectively. The apparent rate constants for uncatalyzed and acid‐catalyzed reactions were evaluated by using the method of least squares for various values of initial molar ratios between [OH] and [COOH]. Also, the activation parameters were calculated.
Polymers from renewable sources. III. Hydroxy‐terminated myrcene polymers
Authors: Cawse J. L. , Stanford J. L. , Still R. H. 
Published: April 2003

AbstractA range of hydroxy‐terminated polymyrcenes has been prepared using hydrogen peroxide initiated polymerization of pyrolysate grade, β‐myrcene in n‐butanol solution at 100°C. An oligomeric fraction, containing a large proportion of dimeric material formed via the Diels‐Alder reaction, always accompanies the major polymeric fraction. Procedures are described for the removal of this oligomeric material. Polyols so prepared and purified had number average molecular weights (Mn) between 4000 and 2000 g mol−1 at low and high initiator concentrations, respectively, with corresponding number average functionalities (fn) between 1.3 and 2.3 and polydispersities (Mw/Mn) of ∼ 1.3. The microstructure of the polyols was investigated using NMR spectroscopy from which the main mode of propagation during polymerization of myrcene was deduced to be 1,4 addition across the conjugated double bonds. Glass transition temperatures of the polymyrcenes measured by differential scanning calorimetry were in the range −50–−60°C.
Polymers from renewable sources. IV. Polyurethane elastomers based on myrcene polyols
Authors: Cawse J. L. , Stanford J. L. , Still R. H. 
Published: April 2003

AbstractTwo hydroxy‐functionalized liquid rubbers, one a commercially available polybutadiene (PB) and the other a specially synthesized polymyrcene (PM), have been converted into homopoly‐urethane elastomers by reaction with 4,4′‐diphenylmethane diisocyanate (MDI). Additionally, PB and PM, each in admixture with various amounts of 1,4‐butane diol, were reacted with MDI to yield two series of segmented copolyurethanes having different hard‐block contents (0–30% w/w). The physical properties of these elastomers have been compared by stress‐strain, thermal, and dynamic mechanical analyses, and by swelling experiments. The two series of segmented copolyurethanes have similar morphologies being almost completely phase‐separated and variations in physical properties have been empirically related to hard block contents. The PM‐based elastomers exhibited higher Tg values, ultimate elongations, and larger swelling ratios, but were softer and possessed lower tensile strengths in comparison with elastomers based on PB. These differences have been related to sol‐fraction contents, the nature and distribution of molecular species present in the parent liquid rubbers and hence to polyol functionalities (fn). Analysis of the stress‐strain data from the homopolyurethanes using the Mooney‐Rivlin expression enabled the relationship between fn and elastomer structure to be quantified in terms of the molar mass (Mc) of the polyurethane network chains forming the soft blocks.
Evidence of pyrene formation in butadiene–styrene‐based rubber subjected to UV irradiation
Authors: Abu‐Zeid M. E. , Amer M. F. , Ollis W. D. 
Published: April 2003

AbstractA strong pyrene emission was observed when certain block, alternate, and random butadiene–styrene‐based rubber films were subjected to intense UV irradiation in vacuum. Weak or no pyrene emission was obtained from the same films when they are irradiated in the presence of O2. A mechanistic scheme leading to pyrene formation in these samples is given together with qualitative explanation of the dependence of pyrene formation on sample composition.
Specific refractive index increments of ethylene–vinyl acetate copolymers in trichlorobenzene solutions at 145°C
Authors: Bugada D. C. , Gagnon R. , Rudin A. 
Published: April 2003

AbstractSpecific refractive index increments of ethylene/vinyl acetate copolymers have been masured in trichlorobenzene at 145°C. A relationship between these values and copolymer composition has been determined for use in light scattering measurements of weight‐average molecular weights of these materials. The data are also required for analysis of molecular weight distributions by size exclusion chromatography with light scattering detection.
Algorithm for computation of molecular weight distribution and its moments in reversible step‐growth polymerization in batch reactors
Authors: Kumar Anil 
Published: April 2003

AbstractThe differential equations governing the molecular weight distribution (MWD) in step‐growth polymerization are coupled and nonlinear and a large number of them must be solved simultaneously to keep the truncation error low. In this work, these equations have been decoupled so that they can be solved sequentially. The solution of these is independent of the truncation error and there is considerable saving of computation time. To demonstrate the efficiency of the algorithm, the formation of polyethylene terephthalate (PET) in batch reactors with ethylene glycol evaporating has been analyzed. The feed to the reactor is taken as polymer with its oligomers present according to the Flory's distribution. The effect of pressure and temperature of the reactor on the progress of polymerization has been modelled and evaluated. The amount of ethylene glycol distilled, the concentrations of the first five oligomers Q1 to Q5, the number average chain length, and the polydispersity index of the polymer have been determined. It is shown that the reduced pressure and increased temperature reduce the concentration of the condensation product in the reaction mass, thus pushing the polymerization in the forward direction. Lastly the CPU time on Dec 1090 using this algorithm is only 0.40 s compared to about 10 min for similar computations using other existing methods.
Rheological parameters of polyolefin suspensions
Authors: Suuronen M. , Seppälä J. , Laine J. , Elovainio E. 
Published: April 2003

AbstractEffects of rheological parameters of polyolefin suspension were studied to better understand stirred tank polymerization reactors and their engineering principles. Experimental results have been fitted into a quadratic model. Consistency index and behavior index have been determined as functions of solids concentration, temperature, and particle size.
Studies on tri‐n‐butyltin methacrylate (TBTM). IV. Antifouling compositions based on copolymers of tri‐n‐butyltin methacrylate and methyl methacrylate
Authors: Deb P. C. , Chakraborty B. C. , Samui A. B. , Sankholkar S. C. 
Published: April 2003

AbstractBased on reactivity ratios reported earlier, a number of copolymers of methyl methacrylate and tri‐n‐butyltin methacrylate has been prepared. Release of tri‐n‐butyltin oxide into seawater from the copolymer films has been determined at 30°C as a function of time. The copolymers behave in a typical manner—an initial increase in leaching rate followed by a steady state which is reached after about 60 days. Pigmented copolymer films behave in a similar manner, even though the overall leaching rate is slightly lower. Release rate data are also presented for a typical antifouling paint formulation.
13C‐NMR determination of the tacticity of polyepichlorohydrin
Authors: Cheng H. N. , Smith D. A. 
Published: April 2003

AbstractThe microstructure of polyepichlorohydrin was directly studied by high‐field 13C‐NMR. Spectral features were found that correspond to different tacticities. By using curve deconvolution techniques, the different tacticities were assigned and quantified.