bluuebunny/crossref_metadata_2025_split huggingface dataset:
The resilience of chemically modified cottons. I. Reactions of alkali cellulose and of sodium cellulosates with methylene dibromide
Authors: Lobunez W. , Dusenbury J. H. 
Published: April 2003

AbstractA study has been made of the reactions of alkali cellulose with methylene dihalides, particularly methylene dibromide. These reactions have involved cotton cellulose in a swollen state, and the treated fabrics have been found to exhibit improved wet crease recovery, with little or no effect on dry crease recovery. The rates of reaction of methylene dibromide with alkali celluloses prepared from potassium hydroxide have been found to be more than double those with alkali cellulosed prepared from sodium hydroxide. The energies of activation in both cases are about 25 kcal./mole, statistically indistinguishable for the two types of alkali, and consistent with the view that covalent bonds are being formed in the course of reaction. The implications and limitations of these results are discussed. Studies have also been made of the reactions of sodium cellulosates with methylene dibromide. In one case, the sodium cellulosates were prepared by reaction of the cellulose with sodium dissolved in liquid ammonia. Here, the reactions appear interesting, but essentially difficult to control. Sodium cellulosates were also prepared by reaction of the cellulose with sodium isoamylate in xylene. When proper care is taken to exclude water from the reaction system, it is found that the reproducibility of duplicate experiments is quite good and that the rate of reaction of the sodium cellulosate with methylene dibromide is much greater than that found for an alkali cellulose prepared from sodium hydroxide.
Environmental stress cracking of polyethylene
Authors: Hittmair P. , Ullman Robert 
Published: April 2003

AbstractThe stress cracking of polyethylene was studied under various experimental conditions, and the importance of the effect of both crystallinity and molecular weight of the polymer was established. Many of the variables were investigated, such as the thermal pretreatment of the sample, temperature of the sample, surface tension, and concentration of the stress‐cracking agent, and the magnitude of the stress. The importance of this test procedure and the relationship that exists between the stress cracking of polymers and between similar problems affecting nonpolymeric systems have been analyzed. Some microscopic studies of stress cracking have also been made.
Design of bonded joints
Authors: Lunsford L. R. 
Published: April 2003

AbstractEssentially the entire surface of the U. S. Air Force B‐58 supersonic bomber is aluminum‐bonded panel construction. Primary as well as secondary structural bonded panels were designed and manufactured to operate under demanding service conditions which include high stress, subzero temperature, high temperature, and severe acoustical vibration. Smooth surfaces are an additional requirement at subsonic and supersonic speeds. These requirements demanded that bonded joints in the B‐58 be carefully designed and thoroughly evaluated. Joints in the B‐58 were designed by “empirical procedures,” established for a specific adhesive syetem. Large numbers of test panels were required to confirm panel integrity and establish allowables for design. The development and adoption of accurate theoretical technique for predicting joint streqgths has been pursued and can be expected to reduce both the cost and the amount of testing required to achieve reliable deign with adhesives.
Studies on the orientation phenomena by fiber formation from polymer melts. IV. Effect of molecular structure on orientation. Polyethylene and polystyrene
Authors: Ziabicki Andrzej , Kedzierska Krystyna 
Published: April 2003

AbstractThe effect of spinning conditions on fiber birefringence and spinning stress has been studied on high‐pressure polyethylene and two atactic polystyrenes. The general character of the relations observed is similar to that found for polycondensation polymers, but some deviations concerning the effect of deformation ratio have been noted. The x‐ray patterns of the obtained fibers have been presented and discussed. A general interpretation of the observed structural phenomena in the molten linear polymers, based upon the relative crystallization and orientation rates has been given.
The predominant reaction of some fluorinated polymers to ionizing radiation
Authors: Timmerman Robert , Greyson William 
Published: April 2003

AbstractPolytetrafluoroethylene was irradiated in air, in a vacuum, at elevated temperature, in a nitrogen atmosphere, and in some combinations of these conditions. In all cases the plastic was found to degrade in its structural characteristics. Even the most favorable condition of irradiation (irradiation in vacuo) resulted in a 44% reduction of tensile strength at a dose of 2 Mrad. Polyvinylidene fluoride resisted radiation to at least 100 Mrad effectively. Polyvinyl fluoride was structurally degraded at this dose but retained its structural properties to at least 32 Mrad A cut‐through test under heat, comparing polytetrafluoroethylene with polyvinylidene fluoride and polyvinyl fluoride, showed: (a) Unirradiated polytetrafluoroethylene was most resistant to heat aging. (b) Irradiated and unirradiated polyvinylidene fluoride was inferior to irradiated polytetrafluoroethylene in heat resistance. (c) Irradiated polyvinyl fluoride was superior to irradiated polytetrafluoroethylene; polytetrafluoroethylene at 2 Mrad was inferior to polyvinyl fluoride at 32 Mrad in cut‐through testing. (d) Polyvinylidene fluoride Irradiated and unirradiated and polyvinyl fluoride and irradiated polytetrafluoroethylene all embrittled during heat testing.
Some chemical effects in fatigue cracking of vulcanized rubbers
Authors: Gent A. N. 
Published: April 2003

AbstractAn apparatus is described for studying the fatigue of rubber strips under repeated simple extensions in different atmospheres. The fatigue life is shown to be greatly increased in vacuo for vulcanizates of natural rubber and SBR. The effect of oxidation inhibitors and radical acceptors has been examined; they are found to prolong the life in air, but have little effect in vacuo. The results suggest that a substantial proportion of crack growth in air is due to oxidative deterioration of the rubber at the crack tip, probably initiated by mechanical rupture.
The study of cracking and fracturing of spherulitic isotactic polypropylene
Authors: Barish Leo 
Published: April 2003

AbstractIsotactic polypropylene was melted and crystallized at 125°C. Crystallization was observed dynamically on a microscopic heating stage. Spherulites, when first formed, appear to have a lower order of birefringence than after some growth. Between 4–4.5 min. of crystallization cracking occurs between spherulitic boundaries. In a parallel experiment samples crystallized at 125°C. were quenched after different degrees of spherulization. The effect of degree of spherulization on stress‐strain properties was studied and the necks and fractures of the samples studied. The completely spherulitic samples broke abruptly at spherulitic boundaries without necking. The rate of elongation affected the nature of the fracture of completely spherulitic samples. At low rates of elongation the spherulites have a tendency to “pull out” at the fracture. At high rates of elongation the spherulites break more sharply at their boundaries.
Swelling of filler‐reinforced vulcanizates
Authors: Kraus Gerard 
Published: April 2003

AbstractA theory is developed to account for the restricted swelling in solvents of crosslinked elastomers containing reinforcing fillers. Assuming swelling to be completely restricted at the filler‐rubber interface due to adhesion, the following relation is obtained:

where vr is the volume fraction of rubber in the swollen rubber phase, Vro is the same quantity referred to on otherwise analogous, unfilled vulcanizate, Φ is the volume fraction of filler, and c a parameter depending on the filler, but independent of Φ and Vro. This equation is shown to hold for a large volume of experimental data on carbon blacks, involving four rubbers, several sulfur vulcanizing systems, five solvents, and a wide range of crosslinking. Conformance with the theory indicates that carbon blacks are firmly bonded to the rubber and that, in the sulfur crosslinking systems investigated, they have no significant effect on the stoichiometry of vulcanization (although they may affect the rate of vulcanization). Illustrative examples of applications of the theory to problems in filler reinforcement and vulcanization are shown.
Dynamic properties of heat‐treated butyl vulcanizates
Authors: Payne A. R. 
Published: April 2003

AbstractHeat treatment of butyl rubber containing carbon black can considerably reduce “structure effects” in the dynamic properties of the vulcanizate, although swelling measurements indicate that G ∞ the shear modulus at very high amplitudes is unaltered. This paper compares the G′, G″ and phase angle δ changes that occur with the amplitude of oscillation for both a normal butyl rubber containing HAF black and a vulcanizate of the same composition but which has been subjected to an additional heat‐treatment process with N‐methyl‐N, 4‐dinitrosoanaline.
Orientation in cold‐rolled polypropylene
Authors: Wilchinsky Zigmond W. 
Published: April 2003

AbstractSheets of isotactic polypropylene were prepared to have initially random orientation and were subsequently rolled at temperatures below the crystalline melting point. Their crystal orientation was investigated. The orientation of the c axis (fiber axis) was determined from pole figure data obtained by x‐ray diffraction. It was found that rolling produced orientation of the c axis in two preferred directions in the plane defined by the rolling direction and the normal to the sheet. These two directions made equal angles of inclination with the rolling direction. With increased severity of rolling the component of the orientation vector in the rolling direction increased and the angles between the preferred c axis orientation and the rolling direction decreased. Increasing the temperature reduced the angle of inclination of the preferred c axis orientation. This double c axis orientation was not observed in extruded film. An explanation of the c axis orientation in cold‐rolled polypropylene is offered on the basis of local necking down within the sample during the deformation.
The fine structure of fibers and crystalline polymers. III. Interpretation of the mechanical properties of fibers
Authors: Hearle J. W. S. 
Published: April 2003

AbstractThe mechanics of extension of plant fibers is considered in terms of a spiral arrangement of crystalline fibrils embedded in a noncrystalline matrix. Deformation may take place either by stretching of the fibrils or by extension such as that of a spiral spring. In the latter, the major resistance comes from the reduction in volume. The extension mechanism predominates for low spiral angles; the spring mechanism, for high spiral angles. There is reasonable agreement between the theoretical expressions and experimental results. The application of similar ideas to other types of fiber structure is considered.
Melting temperatures and polymer–solvent interaction for polycaprolactam
Authors: Gechele G. B. , Crescentini L. 
Published: April 2003

AbstractMelting points of four polycaprolactam samples of different molecular weight and their mixtures with various diluents were determined. Heats of fusion and polymer–diluent energy of mixing parameters were calculated according to the theory of Flory. The heats of fusion were found to be about 38 cal./g. The experimental results (independence from molecular weight above a certain value, and from the nature of terminal groups, etc.) agree with the theory. However, in a few cases of poor solvents anomalous behavior can be suspected.
Crosslinking efficiencies of dicumyl peroxide in unsaturated synthetic rubbers
Authors: Loan L. D. 
Published: April 2003

AbstractThe crosslinking efficiencies of dicumyl peroxide in SBR, cis‐polybutadiene, acrylonitrile–butadiene rubber, and polychloroprene have been measured. For the first two rubbers approximately ten crosslinks are formed per molecule of peroxide decomposed, while for the acrylonitrile–butadiene rubber an efficiency close to unity is found. With polychloroprene approximately two molecules of peroxide are used for each crosslink formed. Analysis of the low molecular weight products of the reaction shows that ease of hydrogen abstraction by cumyloxy radicals decreases in the order given above.
Polymerization activity test for methyl methacrylate
Authors: Georgieff K. K. 
Published: April 2003

AbstractTwo activity (polymerization) tests have been developed for evaluating the purity of methyl methacrylate industrially. A 10‐ml. portion of monomer is heated with 0.0400 g. of benzoyl peroxide in a test tube immersed in a bath at 101.2°C., until a spontaneous boil occurs. The effect of temperature, catalyst concentration, oxygen, barometric pressure, and weighing errors on the reproducibility of the test were studied. The inhibition factors for divinylacetylene, hydroquinone, p‐tert‐butylcatechol, and diphenylamine were determined. A second test in which 20 g. of monomer and 0.400 g. of benzoyl peroxide are brought to a spontaneous boil in a round‐bottomed flask heated with a Glass‐Col mantle was also developed. However, the sensitivity of this test to inhibitors and stabilizers was much lower than that of the test tube test.
Network characterization from stress–strain behavior at large extensions
Authors: Morris M. C. 
Published: April 2003

AbstractThe stress–strain properties of natural rubber and synthetic cis‐polyisoprene vulcanizates have been investigated over a large range of extensions. The results are in qualitative agreement with those of Mullins, in that the upturn of a Mooney‐Rivlin plot is ascribed to finite extensibility effects. It is further found that the stress–strain curves can be adequately described by a modification of existing non‐Gaussian theory. Analysis of the curves shows significant finite extensibility effects even at extensions well below the upturn. Thus, division of stress–strain curves into Gaussian and non‐Gaussian regions is to be avoided. Values for n, the number of statistical segments between crosslinks, were calculated using the proposed treatment. The values of n found were relatively unaffected by temperature. Further, the molecular weight of a statistical segment was found to be about the same for synthetic cis‐polyisoprene as for natural rubber despite differences in the crystallization behavior. Crystallization effects are therefore thought to be of little importance in determining the position of the upturn. The equivalent statistical segment was found to be 4.3 isoprene units for natural rubber and cis‐polyisoprene.
Noncorrosive nitrile elastomers
Authors: Trexler H. E. , Ilkka G. A. , Weiss P. 
Published: April 2003

AbstractThe corrosion of steel by nitrile elastomer oil seals prompted a laboratory study of the corrosivity of numerous compounding ingredients and nitrile polymers. Groups of materials studied in this investigation were plasticizers, antioxidants, black fillers, nonblack fillers, curing systems, and base polymers. A corrosion test procedure utilizing a benchtype corrosion chamber was developed, and a corrosion rating system was established. All materials were rated according to their corrosivity under conditions of 100% R. H., and 100°F. for 96 hr. From these data it was possible to formulate several noncorrosive seal compounds without the use of corrosion inhibitors.
Steric effects in the preparation and saponification of some fibrous cellulose esters
Authors: Stanonis David J. , King Walter D. 
Published: April 2003

AbstractTwo reaction paths which can be followed when an acid chloride reacts with an alcohol are discussed. The role of pyridine as solvent and catalyst in this reaction is described. The importance of inductive and resonance effects and the size and arrangement of groups near the carbonyl are emphasized. The heterogeneous preparations of seven cellulose partial esters, the phenylacetate, benzoate, trimethylacetate, triphenylacetate, β,β,β‐triphenylpropionate, α‐(4‐biphenylyl)phenylacetate, and mesitoate are described. Pronounced interference with esterification is noted only in the preparation of the triphenylacetate. Steric hindrance and a poor ability to ionize are considered to be responsible for this result. Outstanding resistance to saponification, thought to be the result of steric hindrance and a reduced tendency to ionize, is reported for three of the cellulose esters, the triphenylacetate, the β,β,β‐triphenylpropionate, and the mesitoate.
Kinetic observations of the quaternization of poly(ar‐vinylbenzyl chloride) with trimethylamine
Authors: Lloyd W. G. , Durocher T. E. 
Published: April 2003

AbstractThe quaternization of poly(ar‐vinylbenzyl chloride) with trimethylamine is shown to be a nucleophilic displacement reaction, the kinetics of which are complicated by several factors, notably differences in the reactivities of o‐ and p‐chloromethyl groups (position isomerism), differences in the reactivities of groups as a function of the reacted or unreacted status of immediately adjacent groups (neighboring group effect), and differences in the reactivities of groups arising from the microtacticity of the polymer segment (configurational effects). Estimates of mean rate constants, activation energies, and preexponential factors are given for high purity poly‐p‐vinylbenzyl chloride and for the analogous ortho polymer.
High temperature oxidative degradation of phenol–formaldehyde polycondensates
Authors: Jackson William M. , Conley Robert T. 
Published: April 2003

AbstractThe degradation of phenol–formaldehyde polycondensates has been investigated at temperatures as high as 1000°C. By employing infrared spectrophotometric techniques and vapor‐phase chromatographic methods, as well as thermogravimetric and x‐ray analyses, it has been possible to examine the oxidation chemistry of this resin system. It has been found that the primary degradation route of phenol–formaldehyde polycondensates, regardless of whether the resin is exposed to elevated temperatures in air, argon, or nitrogen, is oxidation. At elevated temperatures, products are observed from thermal pyrolysis in addition to those from the oxidation path. However, throughout the temperature region studied, the oxidative degradation is always more pronounced. The mechanism of oxidation has been found to agree favorably with the proposals formulated earlier by Conley and Bieron. It is also possible to extend this mechanism to include the formation of graphitelike char. This extension is postulated on the simultaneous formation of the char and carbon monoxide. By infrared studies of the intermediate stages in char formation, the postulation that these products arise from quinone‐type intermediates is justified. In this study, it was found that phenolformaldehyde polycondensates of unusual thermal stability could be produced by high temperature postcuring. The comparison of the oxidation rates of the resin cured at low temperature and this material indicates greatly improved oxidative stability, as well as resistance to thermal pyrolysis. This undoubtedly is due to the complete crosslinking of the resin system.
Ion‐exchange membranes. Application to the treatment of natural rubber skim latex
Authors: Sethu S. 
Published: April 2003

AbstractIon‐exchange membranes have been successfully used in the electrodialysis and electrodecantation of natural rubber skim latex for the recovery of ammonia as well as rubber. Diffusivity of the membrane and current efficiency were studied. An optimum condition is recommended for electrodecantation of skim latex.
Dynamic mechanical properties of several elastomers and their potentialities in vibration control applications
Authors: Yin T. P. , Pariser R. 
Published: April 2003

AbstractThe time–temperature‐dependent mechanical properties of Viton A, Neoprene ILA, Adiprene L‐167, and Nordel hydrocarbon elastomer have been measured primarily on the Fitzgerald transducer. The results cover the plastic to rubberlike transition regions which have been reduced to 25°C. whenever possible. The data are then discussed in terms of the relaxation spectra, monomeric friction coefficients and the shift factors, log QT. Following a brief presentation on the viscoelastic requirements for various vibration control devices, the potentialities of the present elastomers, as well as other common elastomers, are evaluated. It is found that Nordel, Hevea rubber, and Neoprene W are potential vibration isolators, whereas Viton A, Neoprene ILA, and polyisobutylene have desirable vibration damping characteristics. Their effective temperature‐frequency regions of application have been calculated.
Experiments on the effect of ethylamine treatment on the crystallinity of cellulose
Authors: Venkateswaran A. , Riemen W. P. 
Published: April 2003

AbstractThe results of the effect of ethylamine treatment on the crystallinity of cellulose under various conditions have been presented. The mode of removal of the swelling agent from cellulose is important in determining the amount of change in the lateral order structure of cellulose. It seems that the apparent change in crystallinity observed by ethylamine treatment is due to the swelling of cellulose, producing disorder only in the so‐called amorphous content of cellulose.
Radiation protection of polyethylene
Authors: Gardner J. B. , Harper B. G. 
Published: April 2003

AbstractIt is known that aromatic hydrocarbons are more stable to ionizing radiation than are saturated hydrocarbons. It is shown here that polyethylene can be more stable to radiation either by mixing aromatic compounds with the polyethylene or by grafting styrene onto the polyethylene. In either case, the polymer has greater radiation resistance than predicted from the law of averages. Aromatic compounds which have the greatest resonance energy protect the polymer to the greatest extent. In mixtures, polystyrene gives the least protection, and naphthalene, anthracene, and phenanthrene give the greatest protection. Polyethylene grafted with styrene has better radiation resistance than does a polyethylene‐polystyrene mixture. The G(H2) was calculated for each sample, and curves are presented illustrating the effect.
Polyacrylonitrile fiber behavior. I. Mechanisms of tensile response
Authors: Rosenbaum Shlomo 
Published: April 2003

AbstractThe behavior of polyacrylonitrile fibers has been studied by a number of methods over a wide range of temperatures. At the glass transition temperature Tg, in the vicinity of 100°C. by linear thermal expansion, creep, and dye sorption experiments, the break extension was found to rise abruptly, while an initial, stiff response disappeared. The tensile recovery as normally measured was incomplete at all temperatures; below Tg, however, all extensions were completely reversible when the kinetic conditions for retraction were provided. The main extension below Tg is attributed to the straightening of twisted molecules against the intramolecular repulsion of adjacent dipoles, the small initial extension up to the “yield” knee to an increase in volume required for the operation of the main response. The additional extension(s) above Tg appear(s) to involve permanent relative displacement of fiber elements. Water depressed Tg by 30–35°C.