bluuebunny/crossref_metadata_2025_split huggingface dataset:
A viscosity–molecular weight relationship for polydimethylsiloxanes
Authors: Takimoto H. H. , Forbes C. T. , Laudenslager R. K. 
Published: April 2003

AbstractThe relationship of intrinsic viscosity [η] to the weight‐average molecular weight M̄w of polydimethylsiloxane in toluene at 25°C. has been determined. The modified Staudinger equation, [η] = KM̄wa, with K = 2.43 × 10−5 and a = 0.84, describes the relationship for the above polymers in the range of weight‐average molecular weight from 18,900 to 124,500 (as determined by light‐scattering measurements). These constants differ from the values reported by Barry, where K = 2 × 10−4 and a = 0.66 were obtained. The difference is attributed to the fact that Barry dealt with number‐average rather than weight‐average molecular weight.
Crosslinking efficiency of dicumyl peroxide in natural rubber
Authors: Thomas D. K. 
Published: April 2003

AbstractThe rate of decomposition of dicumyl peroxide in natural rubber has been measured at four temperatures and the results lead to the expression k = 3.9 × 1013e−32500/RT for the rate constant. The crosslinking efficiency is high and is constant over the range 110 to 140°C. The low values found for the ratio of acetophenone to cumyl alcohol in the reaction products indicate that hydrogen abstraction is brought about mainly by cumyloxy radicals, although it seems likely that methyl radicals present are also effective in producing crosslinks. No cumyloxy radicals become attached to the polymer during the crosslinking reaction.
The thermal diffusivity of polymer melts
Authors: Shoulberg Robert H. 
Published: April 2003

AbstractA study of the thermal diffusivity of polymer melts as a function of temperature over the range 25–325°C. is described. Measurements were carried out with an apparatus especially designed and constructed for this purpose; this apparatus and the theoretical treatment of data obtained with it are treated in detail. The polymers examined include polystyrene, poly(methyl methacrylate), some of their copolymers, poly(vinyl chloride), linear polyethylene, polyacetal, polycarbonate, cellulose–acetate–butyrate, some “highimpact” polymer blends and terpolymers, and some higher methacrylates. The thermal diffusivities of the melts vary from about 11 × 10−4 cm.2/sec. (for linear polyethylene) to about 5 × 10−4 cm.2/sec. (for poly(sec‐butyl methacrylate)). In general the thermal conductivity of an amorphous polymer decreases as it passes from the glassy state to a melt, but remains quite constant over a wide temperature range in the melt state. On the basis of a limited amount of data one might tentatively conclude that the thermal diffusivities of the melts of vinyl polymers become lower as larger as longer groups are added to the carbon‐carbon backbone. As regards molecular weights equal to those common for molding powders, molecular weight seems to have no effect on the thermal diffusivity.
Thermal degradation of fluorine‐containing polymers. PART II. Degradation in oxygen
Authors: Cox J. M. , Wright B. A. , Wright W. W. 
Published: April 2003

AbstractThe thermal degradation in oxygen of a number of fluorine‐containing polymers has been studied by using a weight loss technique. The relative thermal stabilities of the different polymers have been determined and, where possible, the overall activation energy and frequency factors for their breakdown. The results have been compared with those for samples of the same polymers degraded in vacuum. There is little change in the relative thermal stabilities observed under both conditions, the fully fluorinated structures being the most stable. The changes in the rates of breakdown in the presence of oxygen are difficult to interpret in the absence of mechanistic information.
Effect of the chemical and physical properties of carbon black on its performance in polyethylene
Authors: Williams F. R. , Jordan M. E. , Dannenberg E. M. 
Published: April 2003

AbstractA comprehensive study of the performance of various types of carbon black in polyethylene has been made. The physical and chemical properties of carbon blacks are discussed, and the effectiveness of various blacks as ultraviolet screening agents for polyethylene is assessed. It is seen as a first approximation that primary particle size is the property of the carbon black which largely governs the weatherability of a compound. The data suggest that this is due to that fact that the degree of ultraviolet protection is dependent on the presence of submicroscopic aggregates and their distribution throughout the polymer mass. It is proposed that the aggregate size and distribution are largely controlled by the surface energy arising from the dimensions of the primary particles. Studies of carbon black‐antioxidant systems gave results which were in agreement with those of Hawkins et al., who found that carbon blacks having a polar surface exhibit a synergistic behavior with organosulfur type antioxidant, greatly increasing the time required to absorb a given amount of oxygen or undergo thermal degradation. The present study shows that use of antioxidants also contributes to the ability of polyethylene compounds to resist accelerated aging. Outdoor aging of the same compounds are in progress, but more time is required to see if antioxidants are helpful in the manner indicated by the accelerated weathering studies. The effect of carbon blacks on the mechanical properties of polyethylene is discussed, and data are presented to show that higher loadings of carbon black than normally used for ultraviolet protection greatly increase the tensile yield (stress at draw point) at relatively fast rates of applied stress. It is suggested that the use of moderately high concentrations of carbon black would enhance the performance of polyethylene in applications such as pipe which often fails under rapidly applied stress.
Poly(vinyl alcohol)–iodine complexes
Authors: Zwick M. M. 
Published: April 2003

AbstractThe poly(vinyl alcohol)–iodine blue color reaction in dilute aqueous solution has been investigated, and extinctions at the absorption maximum have been measured as a function of the concentrations of polymer, iodine, iodide ions, and boric acid. Depending upon the reaction conditions, the main absorption maximum can be made to appear at any wavelength between 580 and 700 mμ, with the longest wavelengths and highest extinctions per vinyl alcohol group showing up at high boric acid concentrations. Poly(vinyl alcohol) samples from various sources displayed, under identical reaction conditions, great differences in staining intensities. This can be ascribed to differences in the regularity of the polymer chain structures. To account for the behavior of poly(vinyl alcohol) towards iodine under a wide variety of reaction conditions, as well as for a number of irreversible or only slowly reversible phenomena, a model for the mechanism of the PVA–iodine complex formation is proposed involving a dual process of helix formation and intramolecular helix association. There is evidence to indicate that at full iodine saturation of the polymer, 12 vinyl alcohol residues supported by one boric acid molecule form a single turn of a helix which enwraps one iodine atom, out of a long polyiodide chain nested in the interior of a poly(vinyl alcohol) helix.
Stress softening in rubber vulcanizates. Part I. Use of a strain amplification factor to describe the elastic behavior of filler‐reinforced vulcanized rubber
Authors: Mullins L. , Tobin N. R. 
Published: April 2003

AbstractMeasurements of Young's modulus of vulcanized rubbers containing thermal carbon black show the predicted dependence on the volume concentration given by relationships derived for a suspension of spherical particles, for example, that due to Guth, Simha, and Gold which gives E = E0 (1 + 2.5c + 14.1c2). A simple interpretation of the results is that the strain in the rubber is increased by the presence of filler so that the ratio of the average strain to the measured overall strain is given by the factor X = 1 + 2.5c + 14.1c2. This factor was used to analyze simple extension stress–strain data obtained at larger extensions. For this purpose the Mooney‐Rivlin relation was used to describe the behavior of the rubber phase. Values of C1 independent of the volume concentration and in close accord with measurements of the equilibrium volume swelling of the rubbers were obtained. Values of λ* were also consistent with those of C1. Analysis of stress–strain data obtained on rubbers containing smaller particle‐sized carbon blacks is more complex. For these materials the relation due to Guth, viz., E = E0 (1 + 0.67fc + 1.62f2c2), was chosen. By the choice of suitable values of f, good agreement with the Mooney‐Rivlin stress–strain relation was achieved at volume concentrations less than about 0.15.
A light‐scattering and membrane formation study on concentrated cellulose acetate solutions
Authors: Kunst B. , Škevin Đ. , Deželić Gj. , Pétres J. J. 
Published: April 2003

AbstractAn improved explanation of the mechanism of the porous membrane formation with asymmetric structure has been proposed. It emerged from the correlation of the results obtained by the light‐scattering measurements of the ternary membrane casting solutions and by the reverse osmosis and ultrafiltration testing of the asymmetric membranes prepared from these solutions. The results of anisotropic light‐scattering measurements indicated the extent of supermolecular structurization of the casting solution which affected the porous structure formation in the membrane surface region. The variation of the casting solution composition and, particularly, the role of the CA/F ratio, the formamide content, and their influence on the asymmetric membrane properties were investigated and explained using the improved concept of the membrane‐making mechanism.
Kinetics and energetics of a fast polyurethane cure
Authors: Lipshitz Stephen D. , Macosko Christopher W. 
Published: April 2003

AbstractMethods for obtaining kinetic data on bulk polymerizing systems are reviewed, and adiabatic temperature rise is found to be the most useful for fast systems. An adiabatic method is described and used to study the polymerization of poly(ε‐caprolactone triol) with chain‐extended 1,6‐hexane diisocyanate catalyzed with dibutyltin dilaurate.
Thermal stability of phosphonitrilic fluoroelastomers
Authors: Valaitis J. K. , Kyker G. S. 
Published: April 2003

AbstractThe thermal stability of the polymer prepared by substituting poly(dichlorophosphazene) with an excess of a 64/36 mole‐% mixture of the sodium salts of 2,2,2‐trifluoroethanol/2,2,3,3,4,4,5,5‐octafluoropentanol were studied by thermogravimetric and gel permeation chromatography techniques. The primary mode of degradation of this polymer was shown to be via random scission. The overall degradation reaction corresponds to quasi‐zero‐order kinetics.
Laser marking in dye–polymer systems
Authors: Novotny V. , Alexandru L. 
Published: April 2003

AbstractLight‐induced marking in dye–polymer systems based on dye diffusion was investigated. It was demonstrated that when a dye film coated on an appropriate polymer substrate is exposed to a laser beam, marked areas are obtained. In the exposed areas the dye melts and diffuses into the substrate and also flows laterally. The dye, when diffused into the polymer, shows altered spectral characteristics, and significant changes of optical densities can occur in the marked areas. A direct optical marking process based on these phenomena is described. Good spatial resolution and adequate marking sensitivities were demonstrated as submicron marks and energy density requirements below 100 mJ/cm2 were obtained.
Active transport membrane for chlorine ion
Authors: Ogata Naoya , Sanui Kohei , Fujimura Hideo 
Published: April 2003

AbstractA specific functional group that could interact with ions was introduced in a synthetic membrane to achieve an active transport of ions. One way to synthesize the active transport membrane was to introduce a functional group which has a tautomerism upon pH changes in an aqueous solution. A polymer having pendent N‐hydroxyethyl amide groups was synthesized to form a membrane, and the membrane was fixed in a cell as a partition film, in which one side of the solution was adjusted to be acidic and the other side basic. It was then possible to transport chlorine ion through the membrane owing to the carrier functions caused by tautomerism of the N‐hydroxyethyl amide group from the acidic to the basic sides. The transport of the chlorine ion was not dependent on diffusion control.
The kinetics of hydrolytic polymerization of ε‐caprolactam. V. Equilibrium data on cyclic oligomers
Authors: Tai Kazuo , Tagawa Takashi 
Published: April 2003

AbstractThe concentrations of the cyclic oligomers (Ci; i = 3, 4, 5, and 6) in the polymeric products of ε‐caprolactam were determined by high‐performance liquid chromatography. The equilibrium data on the oligomers were obtained as a function of the polymerization temperature and initial water concentration. The concentration of each oligomer in the equilibrated polymer was found to increase with the temperature and/or initial water concentration. A set of the kinetic equations to express the oligomer formation during the polymerization was also proposed.
Effect of pH on the critical micelle concentration of sodium dodecyl sulphate
Authors: Rahman A. , Brown C. W. 
Published: April 2003

AbstractCritical micelle concentration (CMC) of sodium dodecyl sulphate (SDS) at various pH's between 2 and 10 has been studied using three methods as dye absorption, conductance, and light scattering measurement. At low pH (below pH 4) the CMC decreases whereas at higher pH it remains constant.
Effect of grafted UV stabilizers on wood surface erosion and clear coating performance
Authors: Williams R. Sam 
Published: April 2003

AbstractThe critical element for a durable exterior clear coating on wood is photochemical stability of the wood surface beneath the coating. If this interface is not stabilized, even a durable coating will delaminate due to photoinduced wood degradation. A new method for stabilizing the wood surface was developed and evaluated. HEBP [2‐hydroxy‐4‐(2,3‐epoxypropoxy)benzophenone] was grafted to western redcedar (Thuja plicata). HEBP contains an ultraviolet (UV) stabilizer moiety that improved the xenon are accelerated weathering performance of western redcedar (WRC). The weathering performance of the HEBP‐modified WRC was compared with WRC treated with an unbound UV stabilizer of similar type and with untreated controls. The grafted stabilizer reduced the erosion rate (weathering) of unfinished WRC, and, as a pretreatment under clear finishes (spar varnish and exterior grade polyurethane), the stabilized surfaces improved coating performance and color retention.
Polyamide–polyether copolymers: A new family of impact‐resistant thermoplastics
Authors: Rasmussen Jerald K. , Smith H. K. 
Published: April 2003

AbstractA new family of thermoplastic polyamide–polyether copolymers that display outstanding impact resistance and are especially useful as hot melt adhesives are described. These polymers are prepared by copolymerizationof polymerized fatty acid derivatives (dimer diamines) and poly(oxyalkylene) diamines with the typical polyamide monomers sebacic acid and piperazine. Impact resistance is apparently achieved through synergistic interaction between the dimer and the polyether portions of the polymers.
Mechanical behavior and dilatation of particulate‐filled thermosets in the rubbery state
Authors: Yilmazer U. , Farris R. J. 
Published: April 2003

AbstractThe stress–strain–dilatational response of glass‐bead‐filled, amorphous, network polyurethanes was investigated above their glass transition temperature. The mechanical–dilatational behavior was studied as functions of filler content, particle size, crosslink density of the polymer, and the surface treatment of the filler. It was found that the stress–strain properties are strongly affected by separation of the filler from the matrix. Measurements of the vacuole formation and growth processes enabled modeling the stress–strain response as well as understanding the ultimate behavior of the composites. Also, it was found that the dilatational response of the composites can be shifted on a single curve given by the second integral of the Gaussian function.
Moisture effects during cure of high‐performance epoxy matrices
Authors: Stark E. B. , Ibrahim A. M. , Munns T. E. , Seferis J. C. 
Published: April 2003

AbstractThe effects of absorbed moisture on the cure reactions and subsequent solid‐state properties of a high‐performance epoxy system were investigated in this study. The resin systems investigated were a model system, TGDDM–Novalac–DDS–BF3:MEA (TNDB), and its commercial analog, Hercules 3501–6. The samples were exposed to three environments: a liquid water environment at 50°C; an 85% relative humidity vapor environment at 50°C; and an evacuated, desiccated atmosphere at 22°C. Differential scanning calorimetry (DSC) thermograms were obtained for the Hercules 3501‐6 formulation as well as various compositions of the TNDB system for samples exposed to each of the three environments. Moisture was found to accelerate the cure especially for formulations exposed to the vapor environment. Dynamic mechanical experiments were also performed on cured, thin film samples. The “wet” samples were produced by adding water to the resin mixture prior to B‐staging. The moisture was shown to increase the extent of reaction, but produce a slightly lower degree of crosslinking as related to the sample's glass transition. This has been attributed to chain‐extension reactions, such as the hydroxyl–epoxide etherification reaction, which are favored in the presence of hydroxyl groups from water.
Primary molecular products of mechanical fracture of polymers
Authors: Enikolopian N. S. , Zarkhin L. S. , Prut E. V. 
Published: April 2003

AbstractPrimary molecular products of mechanical fracture were determined for polymers of different structure. For the first time the velocities of the products translation were measured, and kinetic energies and translation temperatures (2000–5400 K) were calculated.
The effect of certain processing variables on the form ii to form i phase transformation in polybutene‐1
Authors: Hong Kwang‐Bum , Spruiell Joseph E. 
Published: April 2003

AbstractDensity and wide angle x‐ray scattering techniques were used to study the form II to form I phase transformation in polybutene‐1. The influence of deformation by cold rolling, orientation produced by melt processing (film blowing), and certain additives blended with the homopolymer on the phase transformation behavior were examined. A new technique based on a combination of wide angle X‐ray diffraction and density measurements was devised to determine the relative fractions of form I, form II, and amorphous phases present. Small reductions in thickness by cold rolling cause a rapid partial transformation to form I followed by further transformation at enhanced rates. The enhancement of crystal transformation by cold rolling is primarily the result of the stresses or strains applied rather than the orientation produced. The introduction of molecular orientation by melt processing also enhances the rate of the form II to form I phase transformation, but it is rather less effective than small amounts of cold rolling which themselves produce comparatively little change in molecular orientation. The mechanical blending of polypropylene with polybutene‐1 was found to accelerate the form II to form I phase transformation, while another additive (1‐naphtylacetamide) known to be a good nucleating agent for crystallization of polybutene‐1 did not increase the rate of phase transformation when added at concentration levels needed to nucleate crystallization from the melt.
Effect of solvent balance on the surface properties of poly(vinyl chloride)
Authors: Wildman Gary C. , Hsu S.‐J. Raymond 
Published: April 2003

AbstractFilms of poly(vinyl chloride) have been cast from solutions of varying thermodynamic quality and the film properties studied by inverse phase gas chromatography. The solvents included tetrahydrofuran, cyclohexanone, and mixtures of toluene with both tetrahydrofuran and cyclohexanone. The solvent composition was followed during evaporation and film formation for the mixed solvents, and it was shown that the slower evaporating solvent component has the greatest effect on the surface properties of the films. The porosity of the polymer film surfaces is interpreted in terms of the mobility of the polymer chains during film formation. At high concentrations, polymer chain–polymer chain interactions become stronger when thermodynamically less powerful solvents are used or are last to leave during film formation; therefore, the solvent balance has a critical influence on the film surface properties. Annealing the poly(vinyl chloride) above the glass transition temperature reduces the surface porosity of the cast polymer.
Influence of processing conditions on structure development and mechanical properties of poly(butylene terephthalate) filament
Authors: Lu Fu‐Min , Spruiell J. E. 
Published: April 2003

AbstractA study of the relationship between the drawing and annealing conditions of melt‐spun poly(butylene terephthalate) filaments and the resulting structure and mechanical properties is described. The relative amount of β‐form crystal content was found to increase with increase in draw ratio and to be directly proportional to the drawing stress for a given draw ratio. As drawing stress decreases with increase of draw temperature, the β content decreases rapidly with increased draw temperature. Annealing reduces the amount of β‐phase but increases the α‐phase content and crystallinity. The effect of these structural variations on the mechanical properties is examined. The mechanical properties are shown to be very sensitive to the structure of the filaments and, hence, to the processing conditions.
Diffusion and solubility of hydroxy compounds in polyolefines
Authors: Koszinowski Johannes 
Published: April 2003

AbstractThe diffusion and relative solubility coefficients of some alcohols, phenols, and antioxidants have been measured by a permeation method for LDPE at room temperature. The diffusion coefficients of the hydroxy compounds are compared with those of the alkanes. The diffusion coefficients of the alkanes mark out upper limiting values which are not exceeded by the hydroxy compounds of comparable molecular weight.
The role of surfactant structure and monoethanolamine in the environmental stress cracking of polycarbonate
Authors: Faulkner Douglas L. 
Published: April 2003

AbstractThe critical strains required to initiate cracking of polycarbonate exposed to a number of poly(oxyethylene)ethoxylate surfactants were determined. Solubility parameters of the surfactants were calculated from knowledge of the molecular structure. A model proposed by Jacques and Wyzgoski that uses the square of the solubility parameter difference of the surfactant and polycarbonate and the surfactant molar volume was determined to be useful for predicting critical strains for polycarbonate. A major assumption in this model is that stress cracking is related to swelling or plasticization of the polymer by the cracking agent, which ultimately leads to the polymer's failure. However, the model does not predict the observed strong stress cracking of polycarbonate by monoethanolamine. In this investigation it was determined that polycarbonate is chemically degraded by monoethanolamine. This degradation is sufficient to initiate stress cracking at lower strains than would otherwise be predicted by solubility parameter and molar volume concepts. With the knowledge obtained from this investigation, it is possible to predict which poly(oxyethylene)ethoxylate surfactants are stress cracking agents for polycarbonate.