bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potential of adhesives for the future
Authors: Epstein George 
Published: April 2003

AbstractRapid technological advancements have contributed to the increasing application of adhesives. Because of these accomplishments, because of continuing materials research and process development activities, and because of their inherent advantages, adhesives have a great potential for the future. Requirements for the future impose a severe challenge on developmental capabilities. More severe structural requirements and environmental conditions may be expected. Because of increasing complexity and costs, there are requirements for significantly higher orders of reliability and lower fabrication costs. Improvements in bonding processes and development of comparatively new techniques are desirable. Test methods require further development and standardization—especially nondestructive methods. Continuing work in collecting and reporting pertinent information, especially on properties and design parameters for adhesive bonding is helping to advance the utilization of adhesives. Current trends indicate that adhesives are progressing from the realm of “art” to science, a factor which should substantially aid in advancing the future potential for adhesives.
A flywheel impact test for measuring physical properties of tire cords
Authors: Parker J. P. , Kemic C. S. 
Published: April 2003

AbstractThe development and operation of a dynamic tire cord testing apparatus is described. The apparatus consists of a rotating wheel which applies a transverse load to a tire cord and carries it to break. It can be operated at speeds which impact tire cord at velocities of from 10 to 80 ft./sec. The techniques used for detecting, recording, and calculating energy load‐elongation characteristics and time to break are described. Some data showing the effect of impact velocity on the physical properties of nylon, rayon, and polyester tire cords are presented.
The viscoelastic behavior of isotactic polypropylene fibers
Authors: Laible Roy C. , Morgan Henry M. 
Published: April 2003

AbstractThe stress‐strain properties of isotactic polypropylene yarn have been studied over a wide range of strain rates up to 2,000,000% per minute. The testing equipment used included the Instron, three pneumatic and pneumatichydraulic type of high speed testers, the falling weight method, the rotating disc longitudinal impact and ballistic techniques. Evaluation of the behavior of polypropylene at strains of 2, 6, 12, and 16% shows the existence of two relaxation peaks, one at τ = 10−2 sec. and the other at about 102 sec. with a plateau of little time dependency in between. The data, especially at the shorter testing times, can be well represented by a single mechanical model composed of two Maxwell units in parallel. Information concerning the ultimate properties of isotactic polypropylene yarn was also obtained. The work‐to‐rupture values for polypropylene at most strain rates exceed those characteristic of any other available textile material.
Investigations of the phenomena of coacervation. Part III. Phase equilibrium in the three‐component system toluene–ethanol–polystyrene
Authors: Utracki Lechoslaw 
Published: April 2003

AbstractThe goal of this work was to prove that the phenomenon of cacervation was one of the phenomena of phase separation determined by the general laws of thermodynamic phase equilibrium. In this connection, the toluene–ethanol–polystyrene system, known from the literature to be capable of forming coacervates: was studied, and the binodial curve as well as a number of semiempirical coefficients necessary for its theoretical determination established experimentally. For the latter purpose use was made of a generalized form of Maron's equation for the thermodynamic potential of mixing. The experimental and theoretical data showed good agreement. It was therefore concluded that systems capable of forming coacervates are subject to the general laws of thermodynamic equilibrium, and formation of coacervates is a phenomenon within the limits of a simple phase separation.
Polyspiroacetal resins. Part I. Initial preparation and characterization
Authors: Cohen Saul M. , Lavin Edward 
Published: April 2003

AbstractThe reaction of various dialdehydes and one diketone with pentaerythritol or pentaerythritol–dipentaerythritol mixtures, has produced a series of thermoplastic, Polyspiroacetal resins. These possess molecular weights up to 10,000, solubility in a limited range of solvents, and high melting points. Some of these, with an optimum amount of crosslinking, have produced transparent, tough, flexible films.
Rheological properties of viscose
Authors: Hopkins T. E. , Whatley J. W. 
Published: April 2003

AbstractThe steady‐state flow of viscose in a capillary tube viscometer was investigated to determine the rheological properties of this fluid as a function of cellulose concentration and molecular weight. It was found that the flow consistency index increased with increasing cellulose content at constant molecular weight. The flow behavior index was not affected under these conditions. At constant cellulose content, the flow behavior index was found to decrease as the molecular weight of the cellulose molecule was increased. Steady‐state velocity profiles for viscose flowing in a round tube under laminar conditions are also presented as a function of the flow behavior index.
Energy deposition in polymers by reactor radiation
Authors: Jacobs A. , Kline D. E. 
Published: April 2003

AbstractThe temperature distribution in small polymer samples has been used to determine the rate of energy deposition by nuclear reactor radiation as a function of distance from the reactor core. Polyethylene, polystyrene, poly(hexamethylene adipamide), polytetrafluoroethylene, and polymerized epoxy resin were employed as specimen materials. The results for some of these are compared to calculated values based on a simplified radiation spectrum. The values are in good agreement, and it is thus suggested that the calculational method is valid for estimating the integral epithermal neutron flux and the relative energy deposition in different polymers.
Mechanism of discoloration of irradiated polyvinyl chloride
Authors: Ohnishi Shun‐Ichi , Nakajima Yoshiharu , Nitta Isamu 
Published: April 2003

AbstractThe radiation chemical process in polyvinyl chloride has been studied by means of electron spin resonance, optical spectroscopy, and measurement of gas evolution. The chief technique was to irradiate samples at −196°C. and then follow the change or changes with rising temperature. Resonance results showed that, on irradiation, several primary radicals, such as CH2ĊHCH2, CHClĊHCHCl, etc., were produced. Among them some CH2ĊHCH2 radicals could recombine to form crosslinks during irradiation even at −196°C. A mechanism for the discoloration of PVC, based upon results obtained by these three different methods, has been postulated. Discoloration is caused by the formation of polyenyl radicals or polyene molecules of considerable conjugation lengths, some as long as 9 conjugated double bonds. Polyenyl radicals are produced as a result of a thermally induced secondary reaction of the CHClĊHCHCl radical, above −70°C., thereby accompanied by hydrogen chloride detachment following the so‐called “zipper” mechanism. An equation relating the pressure of evolved HCl to the reaction temperature has been derived by a simple kinetic treatment of the zipper reaction. Some effect of heat treatment and increasing dose on discoloration was discussed.
Studies in hard rubber reaction. Part I. Heat of hard rubber reaction
Authors: Bhaumik M. L. , Banerjee D. , Sircar Anil K. 
Published: April 2003

AbstractA method for the determination of heat of hard‐rubber reaction by the application of differential thermal analysis is reported. The heat of reaction was determined with stocks containing different rubber/sulfur ratios and also with a 68/32 stock, preheated to contain different amounts of combined sulfur. Heat evolution is observed first with samples containing about 7% sulfur and therefrom the amount of heat evolved shows a nearly linear increase up to 30% sulfur. With increasing combined sulfur in the 68/32 stock, the quantity of exothermic heat gradually diminishes; so also does the temperature of initiation, i.e., the temperature at which heat evolution appears to begin. Initiation of exothermic reaction appears to be a function of composition and temperature of the mass. An increase in the rate of reaction was observed when the composition reached 0.5 g.‐atom of sulfur per isoprene unit. An endothermic dehydrogenation reaction is observed at the end of the hard‐rubber reaction. This, however; does not affect the determination of exothermic heat, because there is similar dehydrogenation taking place in the reference material (ebonite) which almost balances this heat loss. The final product has a lower sulfur content due to loss of sulfur as hydrogen sulfide.
Oxidation of rubber vulcanized with a sulfenamide accelerator
Authors: Bevilacqua E. M. 
Published: April 2003

AbstractThe solubility and the volatile product yields after oxidation from rubber vulcanized, with sulfur accelerated with an MBT‐selfenamide have been compared with the same quantities for peroxide and TMTD vulcanizates. No significant difference was found. It is concluded that the chain scission mechanism is independent of the nature of the crosslinking.
High‐shear capillary viscosity studies on concentrated copolymer solutions
Authors: Chinai Suresh N. , Schneider William C. 
Published: April 2003

AbstractFlow behavior of ten copolymer solutions of polyacrylonitrile and polymethyl methacrylate in concentrations up to 16% was studied at 30°C. with the use of capillaries of constant diameter but different lengths. The shear rate and shear stress range covered were up to 200,000 sec.−1 and 800,000 dynes/cm.2, respectively. A rheological model of the form log D = A0 + A1 (log τ)β + A11 (log τ)2β was employed in determining the inflection point of the flow curve by computer analysis. A marked dependence of the flow curve upon the lenght‐to‐diameter ratio was observed when l/d ratio decreased to below 300. At shear rates above 50,000 sec.−1 the capillary “end effect” corrections and the kinetic energy corrections were found to be large for the concentrated and dilute solutions, respectively. The flow curves were characterized in terms of the inflection point in accordance with the treatment of Schurz. An upper Newtonian viscosity η* was observed at shear rates above 150,000 sec.−1. Up to a concentration of about 1%, the value of the upper Newtonian viscosity was such that the calculated ηsp/C was essentially independent of C and equal to [η*] obtained by extrapolation to infinite dilution. The values of the heat of activation for viscous flow were found to be dependent upon the applied shear stress.
Kinetics of plasticizer migration between nitrocellulose and ethylcellulose in double‐base propellant systems
Authors: Kaufman Martin H. , Ernsberger Fred M. 
Published: April 2003

AbstractRecent experimental and theoretical work on the concentration‐dependent diffusion of solvents in polymers has led to a reasonably detailed understanding of the processes involved. The possibility exists of supplementing standard but costly surveillance testing with rapid laboratory‐scale measurements of plasticizer migration. Many solvent‐polymer systems conform rather closely to the assumption that the amount of material transferred by diffusion is a function of the composite variable t1/2/l. This means that any scale factor applied to the diffusion path length, in a one‐dimensional system, may be compensated for by applying the square of this factor to the time. It has been shown that this assumption can apply with reasonable accuracy to plasticizer diffusion in the propellant‐inhibitor systems. By approximating a particular 2 in. rocket charge with a one‐dimensional model, it is possible to predict the time required for the unit's inhibitor to reach specified levels of plasticizer migration at any storage temperature of interest. A large temperature coefficient appears to be associated with the equilibrium plasticizer migration in the system chosen for experiment, as well as with the rate. Unless suitable allowance is made, this can lead to serious misinterpretation of the results of the surveillance that has been accelerated by raising the storage temperature.
Electrical conductivity of polypropylene
Authors: Foss Richard A. , Dannhauser Walter 
Published: April 2003

AbstractThe steady‐state (d.c.) electrical conductivity of polypropylene has been measured as a function of temperature (25–150°C.) and field strength (0–94 kv./cm.). The temperature coefficient of the conductivity is 34.6 kcal./mole expressed as an activation energy. This is much larger than the activation energy for diffusion of small molecules in the same polymer. Thus, ionization rather than diffusion appears to be the primary activation process. The conductivity is nonohmic; the conductance quotient is a linear function of field strength but is larger than predicted by Onsager's theory. The ion “jump distance” as evaluated from the isothermal field dependence, is the same order of magnitude as the diffusional mean free path estimated from diffusion studies in other polymers. The conductivity, conduction activation energy, and field dependence appear to be relatively insensitive to polymer crystallinity.
Effect of atmosphere on radiation‐induced crosslinking of polyethylene. Part III. Effect of various gases and effect of electric field
Authors: Okada Yoichi 
Published: April 2003

AbstractPolyethylene film was irradiated in various atmospheres, i.e., He, Ne, Ar, Kr, Xe, N2, NO, NO2, HO2, CO, CO2, CH4, C2H6, C3H8, and C4H10 by γ‐rays from a Co60 source. Xe, Kr, CO, and H2O (vapor) accelerate the radiation‐induced crosslinking as recently shown in case of N2O. In addition, saturated hydrocarbon gases seem to be accelerative. NO depresses the crosslinking markedly and CO2, mildly. On the other hand, NO2 decomposes the polyethylene molecule without irradiation. Every other gas appears to be inactive. In relation to the effect of gas atmospheres, we examined their solubilities in polyethylene. N2O is one of the most soluble of the inorganic gases. An electric field was applied to polyethylene film during irradiation. The degree of crosslinking evidently decreases with applied field, whether the atmosphere is N2O or Ar.
Strength of filled rubbers: Temperature, rate, and oxygen effects
Authors: Bueche F. 
Published: April 2003

AbstractThe time taken to break under fixed load has been measured for three SBR–filler systems. Two SBR–HAF black systems were used, one vulcanized with sulfur and the other with dicumyl peroxide; the third system was an SBR–silica formulation. Measurements at several temperatures between 30 and 100°C. allowed the computation of an activation energy for the breaking process: 45 kcal./mole for all three systems. By measuring the tensile strength of the filled stock in air and vacuum at various temperatures, it was shown that the presence of oxygen seriously decreases the strength of the filled stock at high temperatures, an effect not present in the gum stock or in silicasilicone stocks.
Fractionation of acrylonitrile copolymers. I. Development of a method
Authors: Cotten G. R. , Schneider W. C. 
Published: April 2003

AbstractThe mechanism of precipitation of acrylonitrile polymers was investigated using different nonsolvents. The effect of the dielectric constant and the polarity of individual bonds in the molecule of precipitant is discussed briefly. A methyl methacrylate–acrylonitrile copolymer was successfully fractionated from dimethylformamide solution, using a two‐stage fractionation technique, and a mixture of (2 parts n‐hexane + 1 part ether) as a precipitant. The molecular weight distributions of primary fractions were skewed to the left and overlapped each other. A large, 100‐g. sample of the same copolymer was separated into eight primary fractions, which on refractionation gave a result substantially the same as that obtained by the small scale experiment. An experimental terpolymer of methylvinylpyridine–vinyl acetate–acrylonitrile, prepared by suspension polymerization, was carefully fractionated by the same method. The polymer was shown to have a double‐peak molecular weight distribution in agreement with the earlier suggestion that acrylonitrile in aqueous suspension polymerizes by two simultaneous mechanisms: (1) homogeneous polymerization of single radicals in solution, and (2) heterogeneous growth of radicals present in stable suspended polymer particles. The above conclusion was further supported by methylvinylpyridine analysis on secondary fractions. It was found that the low molecular weight fractions contained appreciably more of the water‐soluble monomer (M.V.P.), than the high molecular weight fractions.
Measurement of triboelectric position
Authors: Webers Vincent J. 
Published: April 2003

AbstractA convenient technique is presented for determination of triboelectric characteristics of a film sample relative to a group of reference surfaces and to other film samples, with the use of inexpensive, easily assembled equipment. It consists of pressing a number of reference surfaces into contact with a test film, determination of the sign and intensities of the charges generated, by spraying with an indicating powder, and estimation of tribo‐electric position of the test sample by the distribution of positive and negative charges generated. With this technique, relative triboelectric characteristics were determined for films of various polymers. The measurements give some insight into the relation between polymer structure and triboelectric characteristics.
Characteristic viscoelastic parameters for amorphous polymers
Authors: Tobolsky A. V. , Takahashi M. 
Published: April 2003

AbstractBy use of a reference value of modulus equal to 109 dynes/cm.2 and a reference value of time equal to 10 sec., characteristic viscoelastic parameters are defined from stress relaxation master curves and from modulus–temperature curves. Values of these parameters are tabulated for several linear amorphous polymers and slightly crosslinked amorphous polymers.
Stress relaxation in molten polymers. II
Authors: Mussa C. , Tablino V. 
Published: April 2003

AbstractA new analytical method is suggested for the evalution of the stress relaxation phenomena arising when a viscous flow of molten polymers is suddenly stopped. This method is based on the consideration of the relaxation isochronism and of other most typical features of the experimental stress–time relationships. Such features can be deduced by means of an analysis in elementary non‐Hookean bodies in series having a stress–time low of a particular analytical type. Such an analysis is applied to four samples of high and low pressure polyethylenes and natural rubber. The new parameters difined in this way are discussed in order to state some correlations with the structural features. Attention is drawn on the importance of an elasticity number defined as the ratio of the relaxation area to the corresponding Newtonian viscosity.
Stress‐strain behavior of irradiated polyurethane elastomers
Authors: Fritz E. G. , Johnson Peggy M. 
Published: April 2003

AbstractThe applicability of the Martin‐Roth‐Stiehler stress‐strain relationship to a number of reactor‐irradiated (gamma‐ray dose range 0–1.9 × 1010ergs/g. in carbon) polyurethane elastomers has been demonstrated. For each level of dose and irradiation temperature, the stress‐strain values showed remarkably good agreement with the behavior predicted by this relationship, thus permitting a realistic characterization of the stress‐strain curves up to extension ratios of 3 by two parameters: the tangent modulusE0and a coefficientK. While the available data did not justify conclusive inferences regarding the explicit nature of the functionsE0(D) andK(D), it appears from this analysis thatE0varies exponentially with doseDand thatKis a slowly varying function of dose.
The fraction of effective sulfur crosslinking in SBR vulcanizates
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V. 
Published: April 2003

AbstractShear modulus measurements as a function of temperature have been made for SBR vulcanized with sulfur in amounts between 6 and 34% of the recipe. The shape of the modulus–temperature curves are typical of crosslinked amorphous polymers and there is a consistent displacement of the curves toward higher temperatures as the percentage of sulfur in the mixture is increased. The rubbery plateau modulus also increases with increasing sulfur, and from its magnitude the concentration of crosslinks is computed. The ratio of crosslinks to total sulfur atoms is below 0.20 in all cases. The results lend support to the conclusions of Bateman and of Bloomfield that a high proportion of cyclic structures is formed during sulfur vulcanization.
The fraction of effective sulfur crosslinking in high sulfur–natural rubber vulcanizers
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V. 
Published: April 2003

AbstractShear modulus measurements as a function of temperature for smoked sheet natural rubber vulcanized with sulfur in amounts between 2 and 34% show the crosslinking efficiency of sulfur to be much lower in natural rubber than in SBR‐1000, at least for the particular curing recipe here used. The ratio of crosslinks to total sulfur atoms computed from the rubbery plateau modulus is below 0.07 for all of the natural rubber mixtures. Ratios up to 0.20 were found in SBR mixture. The shape and slope of the modulus–temperature curves of natural rubber vulcanizates are similar to those of SBR mixtures and are typical of crosslinked amorphous polymers. Consistent displacement of the curves toward higher temperatures and higher rubber modulus as the percentage of sulfur in the recipes is increased also follows the same general pattern found for SBR. Cyclization is concluded to be the primary cause of the low sulfur efficiency in crosslinking both polymers, although polysulfide formation in natural rubber may further reduce the ratio of crosslinks formed per atom of sulfur combined.
A direct infrared estimation of cyclic oligomers in water extract of nylon 6
Authors: Anton Anthony 
Published: April 2003

AbstractMethods described in the literature for the estimation of the cyclic oligomer content (which includes cyclic dimer, trimer, etc.) of nylon 6 are indirect determinations, generally based on weight differences, and require the prior extraction of ϵ‐caprolactam (monomer) from the sample. Infrared studies show that all of the cyclic oligomers have a strong NH deformation band at 6.45 μ, whereas the monomer does not exhibit such a band. This difference in the infrared is the basis of a direct determination of the cyclic oligomer content in the presence of monomer. In the method, the residue obtained after evaporation of the water extract of nylon 6 is dissolved in tetrafluoropropanol, and the absorbance at 6.45 μ is determined by the base line method. If the per cent moisture in the original nylon 6, the per cent water extractables, and the per cent oligomers in the water extract are known, one can also estimate the monomer content of the sample.
Stress relaxation in molten polymers. III
Authors: Mussa C. 
Published: April 2003

AbstractThe parabolic law, according to the equation , of the elasticity in the relaxation phenomena of molten polymers can be deduced from the consideration of the feature that the experimental stress relaxation curves show log–log plots which are often linear in a broad field. A general analysis, only on the basis of the viscoelastic equation permits calculation of relaxation functions, which are suggested as possible means of polymer characterization.