bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model relating the elastic properties of high‐density polyethylene melts to the molecular weight distribution
Authors: Bersted B. H. 
Published: April 2003

AbstractAn earlier model relating the variation of the steady‐shear melt viscosity of high‐density polyethylene to the molecular weight distribution is applied toward predicting the steady‐shear elastic compliance, the first normal stress difference, and relaxation spectrum as a function of shear rate from the molecular weight distribution. The model envisions the cutting off of longer relaxation times as the shear rate is raised such that at any shear rate ${\rm \dot \gamma }$ the molecular weights and their corresponding maximum relaxation times τm are partitioned into two classes; the relaxation times are partitioned into operative and inoperative states, depending on whether they are less than or greater than τc, the maximum relaxation time allowed at ${\rm \dot \gamma }$. Equations relating molecular weight and relaxation time to the steady‐shear elastic compliance and viscosity are assumed valid at nonzero shear rates, except for the partitioning effect of shear rate. The shear rate dependence of the first normal stress difference and the steady‐shear viscosity for polyethylene melts is successfully predicted over the range covered by the cone‐and‐plate viscometer. The assumed proportionality constant between τc and 1/${\rm \dot \gamma }$ was determined to be 1.7. Using this relation, the maximum relaxation time at 190°C for a polyethylene molecule of molecular weight M is given by τm = 1.4 × 10−19 (M)3.33. Reasonable agreement has been obtained between the experimentally determined relaxation spectrum of a polyethylene melt and that predicted from the molecular weight distribution. The agreement is best at the longest relaxation times.
Internal stresses and activation volumes from the stress relaxation behavior of polyethylene at low deformations
Authors: Kubát J. , Rigdahl M. , Seldén R. 
Published: April 2003

AbstractInternal stress levels and values of the activation volume have been evaluated from the kinetics of stress relaxation in annealed samples of LD and HD polyethylene. The initial deformation of the samples was varied, the maximum values amounting to ca. 1%. The temperature of the experiments was 24°C for LDPE, and 24°, 50°, and 69°C for HDPE. The internal stress level was found to be approximately proportional to the initial deformation and independent of the temperature used. Such internal stresses appear to be introduced upon deformation, since permanent stresses had been removed by careful annealing. The activation volume (v) was found to satisfy the relation vσ* ≈ 10kT, where σ* is the effective stress, i.e., the difference between the applied and internal stress, k is Boltzmann's constant, and T is the absolute temperature. This is in good agreement with results reported elsewhere for a wide variety of materials. This relation applies primarily to the exponential flow portion of the relaxation curves, but by a simple transformation the power‐law region can also be encompassed.
Synthesis of high molecular weight polyacrylamide flocculant by radiation polymerization
Authors: Wada Takeshi , Sekiya Hiroshi , Machi Sueo 
Published: April 2003

AbstractThe radiation‐induced polymerization of acrylamide was studied to prepare a high molecular weight and highly effective polyacrylamide flocculant. Among various solvents, mixtures of water–tert‐butyl alcohol and water–acetone were found to be suitable for the synthesis of the high molecular weight polyacrylamide. For polymerization in acetone–water mixtures, the molecular weight of polymer increases with monomer concentration; but at the high concentration, intermolecular imidation of amide groups tends to take place during the polymerization to from crosslinked and water‐insoluble polymer. The water‐soluble polymer with the largest molecular weight of 6.7 × 106 is produced in the polymerization with monomer concentration of 2.91 moles/1. at 0°C at a dose rate of 6.2 × 102 rad/hr in acetone–water mixture containing 60 vol‐% water. The crosslinking of polymer of the formation of water‐insoluble polymer could be avoided by the addition of K2CO3 or NaOH to raise the pH of the reaction mixture above 6.5. The flocculation effects were evaluated from sedimentation speed of kaolin suspension and transparency of the separated water. The sedimentation speed is proportional to the intrissic viscosity of the polymer in the range of 4 to 23 dl/g. The polymers prepared in this study show much higher sedimentation speed than commercial polyacrylamide flocculants. The transparency of the separated water is higher than 93%, similar to the results with commercial flocculants.
Analysis of the types and amounts of carbonyl species present in oxidized polyethylene
Authors: Benham John V. , Pullukat Thomas J. 
Published: April 2003

AbstractThe carbonyl species present in oxidized polyethylene are qualitatively and quantitatively determined through the use of infrared measurements on the polymer. The method described makes use of a carbon monoxide/ethylene copolymer wedge in the reference beam of the infrared spectro photometer to compensate the large 1720 cm−1 ketone absorbance. This allows one to observe the 1710 cm−1 and 1735 cm−1 carbonyl absorbances as distinct peaks rather than as shoulders on the 1720 cm−1 peak. This is a significant advantage over other published infrared methods for this analysis. The absorbances obtained at 1710 cm−1 and 1735 −1 are then used in an equation to calculate the absorbance at 1720 cm−1 due to ketonic carbonyl only. Our results confirm Cooper and Prober's assignment of both the 1710 cm−1 and 1735 cm−1 absorbances in the infrared spectra of oxidized polyethylene to acid functionality. Our quantitative results are comparable to those reported by Cooper and Prober, and our method represents a significant reduction in the time required for the analysis (1.5 hr vs. ∼45 days). The carbonyl distribution in a commercially oxidized polyethylene wax was determined as being ∼11.0 ketone CO/2000 C and ∼21.7 acid CO/2000 C (with a σ of 1.8 CO/2000 C and 3.0 CO/2000, respectively). A high‐density polyethylene, oxidized with air in the laboratory, contained ∼1.91 ketone CO/2000 C and 2.19 acid CO/2000 C (with a σ of 0.08 CO/2000 C and 0.16 CO/2000 C, respectively).
Thermal behavior of cotton grafted with vinyl monomers individually and in mixture compositions
Authors: Sharma V. N. , Daruwalla E. H. 
Published: April 2003

AbstractThermal analysis of cotton samples grafted with acrylamide, acrylonitrile, methyl acrylate, and methyl methacrylate individually and in mixture compositions has been carried out. Additional endothermic peaks in the DTA curves characteristic of the polymers grafted were observed. Graft copolymerization of acrylamide and acrylonitrile makes cotton thermally more stable, while in the case of methyl acrylate‐and methyl methacrylate‐grafted cottons, the initial decomposition starts at higher temperatures, but subsequent decomposition is faster and the overall thermal stability is lowered. In the case of binary mixtures of acrylamide and acrylonitrile, inception of decomposition starts earlier, but subsequent decomposition takes place at much higher temperatures than for individual monomer‐grafted cottons. Interaction between monomers during grafting is indicated. When fabric samples containing polyacrylamide grafts are methylolated and subsequently cross‐linked, there is a reduction in the thermal stability of the treated cotton.
Thermomechanical studies of semicrystalline polyether–ester copolymers. Effect of thermal, mechanical, and solvent treatment
Authors: Kalfoglou Nikos K. 
Published: April 2003

AbstractThe thermomechanical spectra of a series of elastoplastic polyether–ester copolymers were determined at 110 Hz and between −120°C and 200°C at five compositions. Emphasis was given to samples containing an increasing amount of poly(tetramethylene terephthalate) constituting the hard segment in these copolymers. The effects of thermal history, uniaxial drawing, and solvent absorption were examined. Specimens cut from injection‐molded slabs were also included in the study. Thermal and mechanical treatment had an important effect on the dynamic mechanical properties. The relaxation spectra do not indicate distinct phase separation, but rather a structure of closely interacting hard and soft segments. The molecular origin of the various relaxations was characterized, and it is shown that as the amount of the hard component increases, features in the relaxation spectrum characteristic of poly(tetramethylene terephthalate) become prominent.
Diffusion of radioactively tagged penetrants through rubbery polymers. II. Dependence on molecular length of penetrant
Authors: Rhee Chong‐Kon , Ferry John D. , Fetters L. J. 
Published: April 2003

AbstractThe diffusion of radioactively tagged n‐hexadecane, n‐dotriacontane, and a polybutadiene oligomer with molecular weight 1600 has been studied in 12 rubbery polymers. Diffusion coefficients were obtained from the theory for the thin smear method: for n‐hexadecane and for n‐dotriacontane (with one exception), in the form appropriate for a completely miscible polymer–penetrant pair, and for the oligomer in the form appropriate for slow entry of the penetrant across the penetrant–polymer interface. For the four flexible linear penetrants, n‐dodecane, n‐hexadecane, n‐dotriacontane, and oligomer, the ratios of diffusion coefficients (or translational friction coefficients) are nearly the same in every polymer. It is concluded that these penetrants travel with similar segmentwise motions, although that is not the case with bulkier, more rigid penetrants. For the three normal paraffins, the friction coefficient is approximately proportional to molecular weight, but that for the oligomer is smaller than would be predicted on this basis.
A gel permeation chromatography calibration method for a broad molecular weight distribution polymer
Authors: Mahabadi H. K. , O'Driscoll K. F. 
Published: April 2003

AbstractA novel, precise, and simple method is described for developing a GPC calibration curve for a polymer where only broad molecular weight distribution samples are available. The method demands a GPC calibration curve for another polymer (e.g., polystyrene) and measurement of the intrinsic viscosity and an average molecular weight for each of several samples of the broad molecular weight distribution polymer in addition to GPC measurements on those samples. Results of applying the procedure to poly(n‐lauryl methacrylate) are presented.
Polyurethane interpenetrating polymer networks. V. Engineering properties of polyurethane–poly(methyl methacrylate) IPN's
Authors: Kim S. C. , Klempner D. , Frisch K. C. , Frisch H. L. 
Published: April 2003

AbstractThe engineering properties of polyurethane–poly(methyl methacrylate) simultaneous interpenetrating networks (SIN's) were evaluated. The hardness behavior reflected the observed phase inversion in the electron‐microscopic studies. The maximum ultimate tensile strength was observed at 85% polyurethane–15% poly(methyl methacrylate) IPN and was due to the filler‐reinforcing effect of the rigid poly(methyl methacrylate) phase. The ultimate tensile strenght of the 75/25 polyurethane–poly(methyl methacrylate) IPN was higher than that of the corresponding pseudo‐IPN's (only one network crosslinked) and the linear blend. The leathery and glassy compositions did not show any reinforcement in the ultimate tensile strength. This indicated that the reinforcement in the ultimate tensile strength was not directly related to interpenetration (by increased physical entanglement crosslinks), but indirectly related by reducing the rigid phase domain sizes and increasing the adhesion between the two phases, thus enhancing the filler‐reinforcing effect similar to that observed in a carbon black‐filled rubber. The tear strengths of the polyurethane‐rich IPN's pseudo‐IPN's, and linear blends were found to be higher than that of the pure polyurethane as a combined result of increased modulus and tensile strength. The weight retentions in the thermal decomposition of the IPN's, pseudo‐IPN's, and linear blends were higher than the proportional average of the component networks. The results seemed to indicate that this enhancement was related to the presence of the unzipped methyl methacrylate monomer. It was suggested that the monomers acted as radical scavengers in the polyurethane degradation, thus delaying the further reaction of the polyurethane radicals into volatile amines, isocyanates, alcohols, olefins, and carbon dioxide.
Calibration and molecular weight calculations in GPC using a new practical method for dispersion correction—GPCV2
Authors: Yau W. W. , Stoklosa H. J. , Bly D. D. 
Published: April 2003

AbstractThe method of Balke, Hamielec, LeClair, and Pearce for GPC calibration and molecular weight computation is reviewed and evaluated. A new method, called GPCV2, is proposed which uses the single broad molecular weight distribution (MWD) standard for calibration developed by those workers, but which also incorporates the chromatographic dispersion σ to make the method more accurate in general use. Equations are presented for computing the relationship between actual MW and retention volume VR under the chromatographically broadened curves. This relationship is then compared to those obtained by using the Balke et al. method and the peak position method.
Studies on soluble fraction of glow‐discharge polysilazane formed from hexamethylcyclotrisilazane
Authors: Gazicki M. , Wróbel A. M. , Kryszewski M. 
Published: April 2003

AbstractThe soluble part of glow discharge polysilazane prepared from hexamethylcyclotrisilazane was studied. The composition of the soluble fraction was examined by gas chromatography and mass spectrometry. It was found that the fraction contained five main components, and two of them, identified by mass spectrometry, were octamethylcyclotetrasilazane and bicyclic silazane dimer. A reaction mechanism leading to dimer formation from hexamethylcyclotrisilazane in glow discharge was proposed.
Melt‐spinning dynamics and rheological properties of nylon 6
Authors: Bankar Vilas G. , Spruiell Joseph E. , White James L. 
Published: April 2003

AbstractBasic studies of the melt‐spinning dynamics and rheological properties of a nylon 6 polymer are described. The magnitude of the force components on the spinline has been analyzed with special reference to the drag and rheological forces. Spinline deformation has been investigated for spinning through ambient air and through an isothermal chamber. Both sets of experiments are interpreted using an elongational viscosity. Non‐Newtonian viscosity was measured at 230°, 250°, and 270°C in a Weissenberg rheogoniometer and an Instron capillary rheometer. The principal normal stress difference was measured in the former instrument. The rheological properties are interpreted in terms of the theory of viscoelastic fluid behavior. The isothermal melt‐spinning experiments were also interpreted in terms of the theory of viscoelastic fluids, and attempts were made to understand the spinning results in terms of basic rheological properties.
Thermo‐optical analysis of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/triblock styrene–butadiene–styrene copolymer blends
Authors: Shultz A. R. , Beach B. M. 
Published: April 2003

AbstractBlending of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO resin) with a triblock butadiene–styrene–butadiene copolymer (Kraton 101) monotonically increases the softening temperature of the latter as measured by TOA. The TOA transition temperatures of the styrene/PPO resin phases closely approximate those of polystyrene/PPO resin blends having the same styrene/aromatic ether unit compositions. Uniform mixtures of the styrene blocks with the poly(2,6‐dimethyl‐1,4‐phenylene oxide) molecules is inferred.
Use of auger and x‐ray photoelectron spectroscopy to study the locus of failure of structural adhesive joints
Authors: Gettings M. , Baker F. S. , Kinloch A. J. 
Published: April 2003

AbstractThe techniques of Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) have been used to study the locus of failure of epoxy resin joints. The effects of a long water immersion and the application of a silane‐based primer have also been studied. Results indicated that for dry joints fracture occurred near an epoxy resin/metal interface while with water‐soaked unprimed joints, fracture occurred interfacially between the adhesive and iron oxide. The application of the primer to the metal surface prior to bonding prevented the formation of a water‐formed oxide although fracture was then found to occur through the primer.
The dielectric behavior of the natural resin manila copal
Authors: Goswami Dipendra N. , Bhattacharya Promode R. 
Published: April 2003

AbstractThe dielectric relaxation data of the natural resin Manila copal, obtained by Bhattacharya,1 has been analyzed by the Cole–Cole method at temperatures from 30° to 150°C. Two distinct relaxation processes were found for temperatures of 70°, 80°, and 90°C as opposed to only one as observed by Bhattacharya.1 The relaxation at 100°C and at higher temperatures could be represented by the typical Cole–Cole patterns. The variation by temperature of the static dielectric constant (ε0) exhibited three distinct slopes, which indicated the different phases of the resin during thermal transformation. Two “transformation points”, around 70° and 100°C, were found instead of only one at 105°C as observed by Bhattacharya.1 The static dielectric constant, the dielectric increment, the Cole–Cole distribution parameter, and the relaxation time decreased markedly owing to the increase of temperature from 100° to 150°C. These indicated some changes in conformation of the resin molecules during transition from the solid to the liquid state.
A kinetic and surface study of the thermal decomposition of cellulose powder in inert and oxidizing atmospheres
Authors: Fairbridge C. , Ross R. A. , Sood S. P. 
Published: April 2003

AbstractThe thermal decomposition of fibrous cellulose powder from 275° to 340°C has been studied by thermogravimetry, scanning electron microscopy, krypton adsorption, and gas‐chromatographic analysis of the gaseous products arising from pyrolysis in various oxidizing and inert atmospheres. The reaction kinetics fit a phase boundary model where the rate is controlled by the movement of an interface through a cylindrical particle and the principal kinetic parameters fit a compensation curve described previously for the decomposition of wood products. An explanation of the physical mechanism of pyrolysis is proposed which is consistent with the observed rate data and the structural changes observed by scanning electron microscopy.
Application of instrumented impact test in polymer testing
Authors: Radon J. C. 
Published: April 2003

AbstractAdvanced methods of conducting and analyzing instrumented Charpy impact tests are described and used in measuring the initiation fracture toughness K1c at a range of impact velocities and temperatures. Improvements developed in the impact testing of metals are discussed and applied in the toughness evaluation of polymers. In lower‐speed impact tests where load–displacement records are nearly linear, the maximum recorded load may be used to evaluate K1c by stress analysis K calibration formula. In high‐speed impact tests, where the load trace is highly oscillatory, the fracture load to be used in the calculation must be derived indirectly. The indirect derivation of fracture load for this purpose from a “low blow” stiffness measurement and specimen deflection has been studied in detail, and the use of the periodic time of the “low blow” test has been found to offer a reliable method of calculating the system stiffness.
Polyimides from diisocyanates, dianhydrides, and their dialkyl esters
Authors: Alvino William M. , Edelman Leonard E. 
Published: April 2003

AbstractHigh molecular weight polyimide polymers have been prepared by the reaction of dissocyanates and a mixture of dianhydrides and their dialkyl esters in aprotic solvents. No catalyst is necessary, but high polymer formation is affected by the anhydride/ester ratio and temperature. Dianhydrides such as PMDA, BTDA, TMA, and their esters have been used successfully. Mixtures of these materials have also been used. Tough, flexible films can be obtained from these polymers.
X‐ray diffraction orientation studies on blown polyethylene films. I. Preliminary measurements
Authors: Maddams W. F. , Preedy J. E. 
Published: April 2003

AbstractX‐Ray diffraction pole figure measurements have been made on six films blown from high‐density polyethylene. Five were prepared on an experimental unit; the sixth, blown on commercial equipment, had a higher degree of overall orientation thus enabling more extensive results for the a‐, b‐, and c‐axis distributions to be obtained. The results provide information on the orientation present, how it may be related to the stress crystallization process of Keller and Machin, and the dependence of the tear strengths in the machine and transverse directions on the orientation. The typical behavior, with the a and c axes at 90° and both at an angle to the plane of the film, is shown to be the result of a composite process involving several types of stress during the blowing operation and a partial relaxation arising at one or possibly two stages of the process. The predicted relative tear strengths, obtained from the concentration of c axes inclined towards the machine direction, are in line with the experimental values. There is some evidence that transcrystallization in the surface layers of the films may lead to a better balance of the tear strengths in the machine and transverse directions.
Limits of the chemical composition heterogeneity of random copolymers
Authors: Stejskal Jaroslav , Kratochvíl Pavel 
Published: April 2003

AbstractOne of the characteristic features of copolymers is their chemical heterogeneity. Examples are given of the dependence of conversion heterogeneity in the chemical composition of random copolymers on the initial composition of the monomer mixture, along with typical examples of the differential distribution functions of chemical composition. The maximum attainable values of the conversion heterogeneity parameter have been calculated depending on the copolymerization parameters. The conditions are discussed under which copolymers may acquire chemical heterogeneities high enough to be perceived or determined by fractionation or light scattering. Limits are estimated beyond which the chemical heterogeneity becomes undetectably low and the copolymers can be regarded as chemically homogeneous.
A study on distension index and distribution of crosslinks in formaldehyde‐crosslinked cotton
Authors: Pandey S. N. , Nair Prema 
Published: April 2003

AbstractA study on distension index (DI) and distribution of crosslinks is reported for cotton cellulose treated with selected swelling reagents and crosslinked by different processes with formaldehyde. Details of estimation of the distension index are also described. Distribution of crosslinks under different conditions of crosslinking has also been shown by electron microscopy. Marked differences in DI values and distribution of crosslinks in cellulose samples crosslinked under different conditions of treatments are discussed. The results of these analysis provide quantitative information on the gross uniformity of distribution of crosslinkages in the fiber structure of cotton celluloses.