bluuebunny/crossref_metadata_2025_split huggingface dataset:
The dynamic properties of carbon black‐loaded natural rubber vulcanizates. Part I
Authors: Payne A. R. 
Published: April 2003

AbstractThe dynamic properties of a natural vulcanized rubber containing carbon black were studied for dynamic tensions of amplitude varying greatly. It was shown that both the elastic responses and viscosity change with amplitude of oscillation and with concentration and type of carbon black. The effects of thermal treatment on the dynamic modulus were also studied. Beginning with conditions of equilibrium between the hard and soft regions of the vulcanizate for very weak stresses, the values for the formation of hard regions from soft regions were determined by means of the Van't hoff isochore.
Temperature dependence of nuclear magnetic resonance absorption in coal
Authors: Sanada Y. , Honda H. , Nishioka A. 
Published: April 2003

AbstractThe proton magnetic resonance in the vitrain of Yūbari caking coal and its residue of pyridine extraction has been studied over the range 90 to 423°K. At lower temperature the absorption line consists of a broad component. At higher temperature this component begins to decrease rapidly in the line width and resolves into two components. This rapid narrowing of the absorption line width suggests a glass transition attributed to the molecular motion in coal. The variation of the second moment of the absorption line with temperature reflects the line width variation. From these results some information on the molecular motion and arrangement in coal have been obtained.
Adhesives in ordnance applications
Authors: Tanner W. C. 
Published: April 2003

AbstractThe advantages to be derived from the use of structural adhesives are discussed. Specific developments are cited to illustrate the effectiveness of adhesives in ordnance materiel. Problems peculiar to ordnance applications are discussed. The strengths of adhesive bonds as determined by “static” and “dynamic” conditions are compared, and the importance of proper joint geometry is illustrated.
Significance of good process control
Authors: Bair Floyd H. 
Published: April 2003

AbstractThe important place that adhesive bonding of structural and nonstructural parts has reached is largely due to the recognition and the practice of adequate and exacting processes necessary to produce acceptable parts. The procedures necessary for adhesive bonding are not common for all adhesives, adherends, or parts being bonded. During any process many variables occur that must be satisfied by the results of tests before production is started. This must be followed by quality control tests to continuously assure that high quality parts are being produced. Closely connected with processes are the temperament and capabilities of personnel doing the bonding. It is recommended that a detailed procedure be established in order to develop methods for bonding any specific end item. The purpose of this paper is to examine some processes in relation to their effect on the finished item and to recommend a pattern to follow in establishing good bonding processes.
High‐temperature ceramic adhesives
Authors: Whitney John B. 
Published: April 2003

AbstractThis paper describes the preparation, application, maturing, and fired properties of ceramic adhesives. The great majority of ceramic adhesives are based on a glass‐type bond similar to that found in porcelain enamels and ceramic coatings. Using a frit as the basic constituent, the adhesives are applied to clean metal surfaces and fired to produce the bond. The adhesives resulting from this process retain a useful strength at temperatures of 1000°F. or higher. A process for combining ceramic adhesives and brazing alloys is also described. This combination has produced joints superior in strength to straight ceramic adhesives and comparable in strength to standard brazed specimens.
A modified method of reduced variables for stress relaxation
Authors: Chang Franklin S. C. 
Published: April 2003

AbstractIt has recently been shown that stress relaxation data may be conveniently interpreted using multiple box distribution of relaxation times. The multiple box distribution treatment suggested the possibility of modifying the method of reduced variables or time‐temperature superposition principle to avoid the difficulty of shifting curves in the rubbery region. This modification has now been applied to the experimental stress relaxation data for polyisobutylene. The results obtained verify the earlier observations that the logarithms of relaxation times and modulus constant are related to the reciprocal of temperature linearly, that the slope of these semilog linear relations changes when there is a phase transition, and that two types of mechanisms are operating in the relaxation of mechanical stress. The theorized stress‐time curves predicted by both methods fit the experimental data equally well, but the modulus at very short time predicted by the reduced variables method generally is higher than that by the multiple box distribution method. Relaxation data collected under high speed stretching condition are needed for better elucidation of the short time behavior of viscoelastic material.
Behavior of high strength parachute components at impact velocities up to 700 feet per second
Authors: Coskren Robert J. , Morgan Henry M. , Chu Chauncey C. 
Published: April 2003

AbstractA machine has been designed and constructed which is capable of evaluating high strength parachute components in the laboratory at impact speeds ranging from 200–750 ft./sec. The system consists mainly of a device for propelling various masses with photographic instrumentation for observing the impact. Measurement of missile deceleration gives applied force. Extension is measured for changes in gage marh on the test specimen. Energy absorbed can be calculated from the displacement of two ballistic pendulums. Results reveal that a t impact speeds force and strain waves are generated within the material which cause rapid changes in the forces measured. A theory has been proposed to explain this behavior. Energy measurements indicate a potential change in the stress‐strain curve of nylon webbings and joints during impact. Improvements in energy absorption result.
A comparison of the static and dynamic strengths of several phenolic‐ and epoxy‐impregnated paper and cloth honeycombs in compression
Authors: Lacey R. M. , Smith J. E. 
Published: April 2003

AbstractFive organic crosslinked materials have been studied for compression properties at room temperature. Their static behavior (0.02 in./min.) and dynamic behavior (up to 1300 in./min.) have been measured as a function of the nature of the material or of its apparent density. The materials with‐ stand a higher stress, 30 to 40%, and show a higher modulus of elasticity, about 100%, when subjected to rapid loading. Resistance to fracture is a linear function of the apparent density at two speeds. Equipment as well as methods are described.
Relaxation processes in vulcanized rubber. I. Relation among stress relaxation, creep, recovery, and hysteresis
Authors: Gent A. N. 
Published: April 2003

AbstractAn experimental study is described of stress relaxation, creep, recovery, and hysteresis in vulcanized rubbers under moderate deformations. The measurements indicate that the rate of stress relaxation is substantially independent of the amount or type of deformation for moderate deformations, and is simply related to the hysteresis. The rates of creep and recovery are found to be in good agreement with values calculated from the form of the loaddeformation relationship and the (constant) value of the relaxation rate.
Polymerization of tetrahydrofuran
Authors: Burrows R. C. , Crowe B. F. 
Published: April 2003

AbstractTetrahydrofuran has been polymerized in bulk using 5–20 wt.‐% BF3 without the addition of cocatalysts to give a very high molecular weight, crystalline polymer which exhibits cold‐drawability, toughness, and low temperature flexibility. Within the ranges studied a maximum conversion of 74% was reached at 10% BF3 and 10°C. and a maximum intrinsic viscosity of 3.3 at 10% BF3 and −5°C. Equilibrium molecular weights were obtained in about two days but the highest conversions required about an eleven day polymerization period. Structure, crystallinity, mechanical properties, solubility, thermal properties, and effect of irradiation are among the aspects of the polymer discussed.
Crosslinking of vinylsilicone resins initiated by dicumyl peroxide
Authors: Hartung H. A. , Berger S. E. 
Published: April 2003

AbstractThe effects of cure time, temperature, and initiator concentration on the mechanical properties of a vinylsilicone resin cured with dicumyl peroxide were investigated. The resin had a second‐order transition extending from below 25 to about 100°C. The transition region broadened as the degree of crosslinking increased. Measurements of physical properties at room temperature were very sensitive to small temperature changes. Ultimate strength measurements were particularly unreliable indicators of degree of cross linking because of large random variations and because they depended upon other structural factors besides crosslink density. The best test of degree of crosslinking was modulus measurements above the transition temperature of the resin. Such measurements have a sound theoretical basis and the practical advantage of being insensitive to small temperature changes. Modulus measurements have the additional advantages of being a nondestructive test with a high degree of inherent precision compared to other physical tests. A concentration of about 1.5 wt.‐% dicumylperoxide was optimum for crosslinking the vinylsilicone resin studied. Maximum crosslinking was obtained when the peroxide was utilized slowly a t low temperatures for long cure periods. When a 4‐hr. cure was used the optimum temperature range was 125 to 135°C.
Sur la dégradation thermique du chlorure de polyvinyle. III. Etudes cinétiques sous atmosphère d'air
Authors: Guyot Alain , Benevise Jean‐Paul 
Published: April 2003

AbstractPolyvinyl chloride thermal degradation was carried out under air atmosphere from 150 to 250°C. and the kinetics followed, simultaneously by thermogravimetry and hydrochloric acid evolution measurements. The overall scheme of dehydrochlorination is the same under air and inert atmospheres: it is a chain reaction initiated by thermal instability of irregular structures initially present or created during the course of the reaction. Oxidation plays an important part in the activation of these structures and reduces all activation energies; furthermore, it creates new centers. Oxygen participates alao in propagation and termination of chains of reactions. With an increase in the reaction chains, simultaneously, backbone CC bonds are broken up, and the residue is formed by branched molecules small enough to remain soluble. All kinds of structures, but especially the polyenic ones, are oxidized. When their concentration and degree of oxidation are great enough, a further decomposition of these degraded parts into volatile oxidized products occurs; the velocity of this reaction is then nearly equal to that of macromolecular residue oxidation.
On the colligative nature of the specific refractive increment for statistical copolymers
Authors: Kinsinger J. B. , Bartlett J. S. , Rauscher W. H. 
Published: April 2003

AbstractThe specific refractive increment for statistical copolymers is shown to be colligative in nature for copolymers of styrene–methyl methacrylate thus giving direct evidence to support the assumption of Stockmayer et al. on the theory for light scattering in copolymers. The determination of the mole fraction of mer composition in copolymers by specific refractive increment measurements is shown to be a useful technique and nearly as precise as chemical analysis for carbon. The technique is restricted to soluble systems and is limited by the resolution of the measuring instrument.
Hygrophotographic studies on the permeability to water and moisture of packaging materials
Authors: Sivadjian Joseph , Corral Francisco 
Published: April 2003

AbstractThe permeability to water and humidity of films of plastic materials of different natures and thicknesses was the object of much research achieved by many methods. However, these methods, while relatively simple, are very laborious, demand much time (for example, the gravimetric method), and are often imprecise. The hygrophotographic method is as simple as it is rapid. It requires a minimum of measuring instruments, or, in cases of urgency, no instruments a t all. Special attention was given to the action on the permeability of certain factors such as presence of plasticizers, radioactive rays, temperature, and aging. It was demonstrated that while the presence of plasticizer increases the permeability to water, aging lowers it, precisely because of the departure of this plasticizer during the aging process. It was confirmed that in certain cases (e.g., polyethylene deprived of plasticizers) the law of Q10, according to which in general the permeability of a good film approximately doubles for a 10°C. (18°F.) rise in temperature, is sufficiently verified and that in other cases (e.g., plasticized PVC) the experimental results deviate considerably from ths simple law: the augmentation is at times much greater, especially between 45 and 55°C., than this law indicates, whereas between 55 and 65°C. the law obtains better. On the other hand, the action of the γ‐rays is manifested by an increase, sufficiently visible, of the permeability when the polyethylenic film is irradiated in vacuum, but when irradiated in air the films become too brittle for handling. A series of systematic tests determined the importance of the phenomenon of sorption for the different kinds of plastic films; the degrees of discoloration of the hygrophotographic plates enclosed in plastic bags new or previously heated in an oven at 65°C. during a specified time were compared. It was observed that the thicker the film, the more humidity absorbed. The Manolene films, 200 μ in thickness, had to be heated for 13 hr. at 65°C. for the sorbed water to be completely evaporated.
Internal field emission in carbon black‐loaded natural rubber vulcanizates
Authors: van Beek L. K. H. , van Pul B. I. C. F. 
Published: April 2003

AbstractThe nonohmic behavior of carbon black‐loaded natural rubber viilcanizates was studied. Three samples contained high‐abrasion furnace black (HAF) in good, moderate, and poor dispersion. Another sample contained a good dispersion of medium thermal black (MT). The nonohmic behavior of the poor HAF dispersion and that of the MT dispersion could be interpreted as due to internal field emission acroM insulating gap widths of 2 and 2.5 μ. The existence of such gaps waa confirmed by electron micrographs. No clear evidence of internal field emission could be obtained for the good and moderate HAP dispersions where, according to electron micrographs, the gaps are much narrower. There is some indication that the degree of diapersion can be correlated with field emission characteristics.
Some mechanical changes during sorption of water by dry keratin fibers in atmospheres near saturation
Authors: Feughelman M. , Nordon P. 
Published: April 2003

AbstractIf a wool fiber is held at a small fixed strain in water (∼1%) the stress in the fiber relaxes and reaches a steady value in about 1 hr. If, while the fiber is still held extended, it is dried and subsequently rewetted, the stress in the fiber after rewetting drops rapidly to a minimum and then slowly rises. This rise in stress in the fiber was previously interpreted as a rebuilding of hydrogen bonds under strain in the matrix of the wool fiber. Recent torsional measurements on fibers during the absorption of moisture from dry to a high humidity throw doubt on this conclusion. It appears that the rise in stress after moisture sorption is due to the reformation of the structure of the microfibrils, which have been partially disrupted by the swelling of the keratin structure due to the entrance of moisture. Infrared evidence of increased deuterium oxide penetration of the keratin structure during sorption of deuterium oxide agrees with this interpretation. A mechanism is suggested for this disruption of the microfibrils based on the difference of swelling of matrix and microfibril with the sorption of water into the wool fiber.
Relationship between dynamic modulus of thin films and stiffness, as determined by the Handle‐O‐Meter
Authors: Hansen Orin C. , Marker Leon , Ninnemann Karl W. , Sweeting Orville J. 
Published: April 2003

AbstractA series of thirteen polyethylene and ten polypropylene packaging films was studied by both the Handle‐O‐Meter and the dynamic tensile modulus apparatus, to discover how the stiffness of polyolefin films determined with the Handle‐O‐Meter depended on the modulus of the material and the thickness of the film. The polyethylene films included low‐, medium‐, and high‐density resins and ranged in thickness from 0.7 to 4 mils. The moduli of these films ranged from 2.5 X 109 to 18 X 109 dynes/cm.2 The polypropylene films were made from several types of resins with moduli varying from 73 x 109 to 54 X 109, and the thicknesses of these films ranged from 0.5 to 4 mils. When the logarithm of the ratio of stiffness to modulus was plotted as a function of the logarithm of the thickness of the film, as determined from unit weights and densities, a straight line was obtained with a slope of 2.5. This means that over a wide range of gauge and modulus the Handle‐O‐Meter stiffness of these materials, S (in grams), is related to the modulus, E (in dynes per square centimeter), and the thickness, t (in mils), by the equation S = 1.41 X 10‐9Et2.5. This result, which shows that the Handle‐O‐Meter stiffness of polyolefin films may be represented as a function of the thickness and the modulus as given by the dynamic tensile modulus apparatus, may be used to calculate a modulus value from any single Handle‐O‐Meter stiffness value or, alternatively, to reduce Handle‐O‐Meter stiffness measurements to a standard thickness. Conversely, this relationship may be used to predict the Handle‐O‐Meter stiffness of a film made from a polymer whose modulus is known.
Rupture of rubber. X. The change in stored energy on making a small cut in a test piece held in simple extension
Authors: Greensmith H. W. 
Published: April 2003

AbstractApplication of the tearing energy criterion (Part I of this work) to the problem of the tearing of a rubber strip that contains a small cut or tear of length c in one edge and is stretched in simple extension is based on the relation Wi – W = K(λ)c2hE, where Wi and W are the total stored energies of the strip in the absence and presence of the cut, respectively, h is the thickness λ0 of the strip, E is the stored‐energy density in the central region of simple extension, and K(λ) is a numerical factor that varies with the extension ratio λ in this region. An experimental method is described for measuring (Wi – W), which enables the factor K(λ) to be evaluated. The results indicate that K(λ) decreases from a value of about 3 at low extensions to a value somewhat below 2 at λ = 3. The experiments also provide a more stringent test of the accuracy of the above relation than has been possible hitherto.
Differential thermal analysis of polymers. II. Melting
Authors: Strella Stephen 
Published: April 2003

AbstractA theory is presented of the way in which the melting of a polymer is manifested in a differential temperature analysis thermogram. An analytical method based on this theory allows a precise determination of both the melting point and the crystalline weight fraction as a function of temperature. Experimental results for linear polyethylene and crystalline polypropylene confirm the theory.
Flexcracking of polymers
Authors: Akkerman F. H. D. 
Published: April 2003

AbstractAccurate measurement of several types of fatigue failure in polymers was obtained with a flexing machine equipped with an automatic camera. The technique is described at length. Observations made include that an antiozonant interferes with crack initiation, that a crack may well start under the surface, and that in the growth of a crack the elastic force is equivalent to the hysteretic force. Several photographs show aspects of crack initiation.
Grafting of polyacrylonitrile in cotton fabrics
Authors: Kulkarni A. Y. , Chitale A. G. , Vaidya B. K. , Mehta P. C. 
Published: April 2003

AbstractWith a sodium thiosulfate–potassium persulfate redox system, in situ polymerization of acrylonitrile was studied in cellulosic materials. Traces of copper are found to accelerate the rate of polymerization, giving higher yields on the treated materials. Other variables studied were (a) material/liquor ratios, (b) monomer concentrations, and (c) initiator concentrations. It is found that high material/liquor ratios and higher initiator concentrations cause increased polymer yields on cotton fabrics. Fabrics containing polyacrylonitrile (PAN) are resistant to microbial degradation. Acrylonitrile was polymerized in secondary cellulose acetate, mercerized cotton, and cellophane. Studies of the insolubility behavior of the treated cellulose acetate samples in acetone and dimethylformamide, and of mercerized cotton and cellophane in cuprammonium hydroxide, were carried out for the purpose of examining the presence of cellulose‐PAN grafts. In the latter case, a constant ratio of cellulose to PAN was obtained in the cuprammonium hydroxide‐insoluble fraction over a wide range of polymer add‐ons. Alkaline saponification of the nitrile groups in the treated cotton fabrics, followed by a treatment with formaldehyde at pH 9–9.5 and subsequent curing in the presence of an acid catalyst, yield highly crosslinked fabrics which exhibit a considerable improvement in the wet crease recovery with slight loss in tensile and tear strengths. It is believed that these changes are brought about by the formation of a CO · NH · CH2. Ocellulose type of crosslink. These results strongly support the presence of a cellulose‐PAN graft.
High gloss of extruded high impact polystyrene sheet. A microscopical study of sheet morphology
Authors: Giuffria Ruth , Carhart R. O. , Davis D. A. 
Published: April 2003

AbstractMorphological changes effected in the two‐phase high impact polystyrene system by several methods of securing high surface gloss of extruded sheet were studied microscopically. In the glazing process changes occur in refractive index of the copolymer particles and in the matrix. Excessive glazing may result in oxidative damage. The effects of temperature and oxidation and temperature alone on the copolymer particles have been investigated.