bluuebunny/crossref_metadata_2025 huggingface dataset:
Number and size distribution of particles in cellulosic solutions
Authors: Parks L. R. , Jurbergs K. A.
Published: April 2003

A large amount of work has been reported in the literature on the influence of insoluble materials on the viscose process. Detrimental effects of insolubles on filtration has been the subject of the majority of the research in the past, but some efforts have included studies of the effect of insolubles on yarn strength. A wide range of physicochemical techniques have been applied to the problem with varying degrees of success. Counting of the insoluble particles has been mainly done by microscopic methods or equipment utilizing the breaking of a light beam and photoelectric detection. In the work reported herein, a commercially available particle counter (Coulter counter) which operates on electronic principles has been applied with considerable success to cellulosic solutions. The instrument permits determination of cellulosic particle sizes and size distributions in the size range of real interest to cellulose workers (4–50 μ) and over an even wider range with other accessories. Viscose solutions, diluted 1:10 with dissolving caustic, have been counted before and after filtration. The number of counts varies considerably with species, pulp type, processing conditions, and the presence or absence of surfactant. Filtration through a medium similar to that used in commercial viscose preparation causes a fairly sharp drop in the number of particles greater than 8 μ. The counts below 8 μ are not changed appreciably by filtration. The filter cutoff of cellulose acetate solutions (diluted to similar concentrations) is much less sharply defined. Acetate counting is done in aqueous acetone solution with sulfuric acid as electrolyte. Coulter counts parallel microscopic values, but are far less laborious, and more information about the size distributions is obtained. The instrument has also been used to evaluate filter media for both viscose and cellulose acetate filtration.
Temperature dependence of dynamic mechanical properties of mixed polymer systems
Authors: McIntyre A. D.
Published: April 2003

The temperature dependence of the viscous component E2(1/T) of the dynamic modulus is reported for a homologous series of butadiene–styrene copolymers incorporated at various levels in styrene homopolymer. By the use of a vibrating reed technique based on resonance tuning, the frequency of the applied deformation was maintained essentially constant throughout the temperature range which included the glass transitions of the copolymers. It is shown that, when E2(1/T) for such mixed polymer systems is plotted against reciprocal absolute temperature, the area under the peak corresponding to a given copolymer affords a direct measure of the quantity of the copolymer present. Further, the temperature of maximum E2(1/T) is related to the mole fraction of bound styrene in the copolymer, and the shape of the peak is related to the statistical sequence lengths of styrene and butadiene in the copolymer.
Peroxide‐ and radiation‐cured compounds filled with reinforcing fine‐particle silica
Authors: Sellers J. W. , Wagner M. P. , DeWitt B. J. , Stueber C. C. , Bachmann J. H.
Published: April 2003

There are indications that the chemical reaction involved in bound rubber formation proceeds via a free‐radical mechanism for compounds filled with reinforcing hydrated fine‐particle silica, as well as in the case of carbon black as filler. The high potential of silica as a rubber reinforcer is indicated by its bound rubber formation. This potential was realized by the extent of filler‐polymer interaction developed in silica‐filled vulcanizates cured by peroxide and by high‐energy radiation, respectively. Both these relatively simple curing systems are postulated to effect crosslink formation via a free‐radical mechanism. The value, after cure, of the ratio of the crosslink density of the filled compound to the crosslink density of the respective unfilled compound, η/η0, was taken to be a logical measure of the ability to reinforce. In natural rubber compounds filled with silica (30 vol.), the values of η/η0 obtained were 1.6–1.9 for peroxide‐cured material, and 3.6 for radiation‐cured material. Comparisons are made with similarly cured HAF black‐filled stocks. Sulfur‐cured natural rubber stocks filled with HAF black (30 vol.) generally exhibit η/η0 values in the range of 1.5 to 2.0. Comparative effects of antioxidants are described.
Electron spin resonance studies of polyvinyl chloride irradiated in NH3 gas
Authors: Ueda Hisashi , Kuri Zen'ichiro , Shida Shoji
Published: April 2003

The electron spin resonance of polyvinyl chloride (PVC) irradiated in NH3 was studied. The radicals produced on irradiation in NH3 do not differ greatly from those obtained on irradiation in vacuum, but the reactivity of the former to SO2 to form RSO2ċ radicals is far higher than that of those obtained in vacuum. The radicals produced by irradiation at −78°C. and in vacuum was also studied. The spectra of these radicals were different from those of the radicals produced at 20°C. and in vacuum. The reactivity of the radicals produced in PVC is interpreted on the basis of the length of double bonds conjugating with the radical π‐electron.
A quantitative study of crosslinking cotton with N‐methylol acrylamide
Authors: Gardon John L.
Published: April 2003

Cotton was acrylamidomethylated by applying N‐methylol acrylamide to it with the aid of a mild acid catalyst. When the molal ratio of N‐methylol acrylamide to anhydroglucose exceeded about 0.2, the efficiency of this reaction was suddenly reduced and the variation of density with addon departed from linearity. These and other available facts indicated that only one of the three hydroxyls in cellulose, probably the one in the 6‐position, was involved in the acrylamidomethyl ether formation and that cotton was about 20% accessible to this reagent. When acrylamidomethylated cotton was treated with free radical or alkaline catalysts, the double bonds became partially saturated and the mechanical properties changed in a spectacular manner. In particular, the resilience of the fabric, as measured by crease recovery, was improved. Analysis of double bond reaction at various levels of acrylamidomethyl content of the fabric indicated that free radical catalysis caused homopolymerization of the pendant double bonds, that alkaline catalysis in the presence of water resulted in Michael condensation between double bonds and the hydroxyls of cellulose, and that these two reactions competed with each other when the alkaline aftertreatment was conducted in dry state. These reactions crosslinked the fabric, and the crosslink content could be calculated from the difference of molal methylene and double bond contents.

The crease recovery reached the maximum attainable value characteristic for the method of catalysis when the ratio of accessible anhydroglucose units to crosslinks was 4 to 5. When the crosslinked fabrics were hydrolyzed in acid, the crease recovery increment produced by crosslinking was eliminated after about half of the crosslinks were broken. The residual crosslinks did not contribute to crease recovery. Dry state crosslinking treatments reduced the moisture regain, increased the density, and had no effect on the x‐ray pattern. In contrast to this, wet state crosslinking in‐increased the moisture regain, changed the x‐ray pattern, and, under certain conditions, reduced the density. These results indicate that wet state crosslinking increased the amorphous portion of cotton. Wet state crosslinking lead to higher wet than dry crease recovery whereas the opposite was true for dry state crosslinking. Although the alkaline catalyst did not degrade the fabric, alkali catalyzed crosslinking substantially reduced the tensile strength. Free radical catalysis was more favorable for tensile strength, in spite of the fact that it degraded the fabric in the absence of crosslinking agent.
Sur la déagradation thermique du chlorure de polyvinyle. II. Etudes cinéatiques sous atmosphéare inerte
Authors: Guyot Alain , Benevise Jean‐Paul , Trambouze Yves
Published: April 2003

For a commercial polyvinyl chloride (PVC), polymerized in suspension, decomposition kinetics were studied in a nitrogen atmosphere and isothermal conditions, from 150 to 250°C., by measuring simultaneously loss of hydrochloric acid and loss of weight. Below 200°C., hydrochloric acid is the only volatile product freed; reaction is zero order and activation energy is 20 kcal./mole HCl. Active centers are mainly end chains of unsaturated structures. The reaction is terminated by mutual destruction of radicals, creating crosslinks. Above 200°C., when the degree of dehydrochlorination is high enough, a minor difference is observed between loss of weight and hydrochloric acid loss. The reaction is autoaccelerated and can be classified as a degenerated branching chain reaction. It is suggested that activation of irregular structures, initially present or created during the course of the reaction, and thus responsible for autocatalysis, provides active centers for chain dehydrochlorination. Some of these structures are active at temperatures lower than that of their formation. Each kind of structure is believed to be at the origin of a radical zero‐order chain reaction; its activation energy depends on its type. The reaction chains are terminated by inactivate irregular structures.
Studies on the orientation phenomena by fiber formation from polymer melts. III. Effect of structure on orientation. Condensation polymers
Authors: Ziabicki Andrzej , Kȩdzierska Krystyna
Published: April 2003

The principal regularities of molecular orientation occurring by fiber formation from polymer melts have been proved for several polyamides, copolyamides, polyurethane, and polyester. It has been found for these polymers, as for the formerly investigated polycapronamide, that fiber birefringence (used as a comparative measure of the mean degree of macromolecular orientation) practically does not depend on the deformation ratio S = VE/V0, and monotonically increases with velocity difference (VE − V0) and reciprocal fiber diameter ϕE−1 (measure of cooling rate). Hence the general character of the postulated mechanism of orientation, simultaneous action of velocity field and thermal relaxation, seems to be proved for the typical fiberforming polymers. The differences between the shapes of characteristics birefringence–velocity difference, birefringence–spinning stress, and between the x‐ray patterns of polyamides and polyester have been interpreted in terms of molecular structure and occurrence of H bonds.
Joint design for primary structures
Authors: de Bruyne Norman A.
Published: April 2003

This paper describes European use of glued construction for structural joints in aircraft. It discusses the important considerations in design and strength analysis of stiffened compression and shear panels and considers aspects of detail design in bonded structures.
Special adhesives for rubber bonding
Authors: Peterson Charles H.
Published: April 2003

Special adhesives for bonding of unvulcanized and vulcanized elastomers are discussed. Major emphasis is placed on adhesives and conditions for bonding of vulcanized elastomers. The decline of brass plating is reviewed. Various methods of adhesion testing are discussed and illustrated. Available organic polymer based adhesives will produce high strength bonds to a wide variety of unvulcanized olefinic elastomers. A single coat adhesive has been developed which provides “maximum performance adhesive bonds” to a variety of unvulcanized elastomers. Factors affecting bonding and “bondability index” for the common elastomers are described. The bonding of vulcanized elastomers is a more difficult task. Present adhesives require mechanical or chemical modification of the surface of the elastomer. Brute force tactics used in conjunction with epoxy‐polyamide, phenolic‐polyvinyl formal, or nitrilephenolic systems have performed well in some applications. The quality of these bonds, however, does not equal those produced to unvulcanized elastomers. With cooperation of the users, the adhesive suppliers are developing newer, more effective products to meet the challenge of the advanced polymers and increasingly severe environments in which they are used.
Recent developments in high‐temperature adhesives
Authors: Levine Harold H.
Published: April 2003

(1) The prognosis for adhesives uieful up to an hour at 1000°F., in air, is good. (2) Organic adhesives based on phenolic and silicone‐phenolic resins are more capable than expected of usefulness at 1000°F. (3) Preparation of semiinorganic adhesives by reaction of heat stable organic polymers with inorganic reagents is feasible. (4) The prospect appears excellent for the achievement of adhesives to be used for 1000 hr. at 500°F., in air, on steel. (5) Despite research on 2000°F. adhesives, effort is still urgently needed on materials for use at lower temperatures. (6) Perhaps the area with the most serious shortage of information and research is the development and testing of adhesives for use at 180–500°F. for periods of three to five years. Both military and civilian agencies are planning the construction of supersonic transports which need such structural adhesives.
Process control considerations for adhesive bonding in production
Authors: Bandaruk William
Published: April 2003

A system by which adhesive bonding would be best applied to production on ordnance items has been presented. In this system, process controls must be established. Significant and meaningful process controls must be selected and utilized toward producing the quality and reliability expected of the ordnance article.
Infrared spectra and crystallization of poly‐3,3‐bis(chloromethyl)oxacyclobutane
Authors: Hatano Masahiro , Kambara Shu
Published: April 2003

The process of crystallization and the characteristics of crystalline poly‐3,3‐bis(chloromethyl)oxacyclobutane were investigated by infrared spectroscopy. A comparison of the spectra obtained when the electric vector was vibrating parallel to and perpendicular to the extended direction of specimens of this polymer showed significant dichroism in the majority of absorption bands; also, intensity changes as crystallization of the polymer proceeded were observed in both types of spectra. The crystallization process was examined by noting changes in the spectra with increase in the temperature of the polymer; many crystallization‐sensitive bands were found. The dichroism was particularly marked in the absorption bands which may be due to the wagging‐mode, twisting‐mode, and rocking‐mode vibrations of the methylene groups in this polymer. Optical densities of the bands a t 1027 cm−1, an amorphous band, and 897 cm−1, a crystalline band, were observed a t various temperatures during cooling of the polymer. By use of a plot of the optical densities of both bands against the temperature of the polymer, the degree of crystallinity of the polymer could be estimated as a function of the polymer temperature. The results are in good agreement with the dilatometric results for the crystallization rate. Also, the polymorphism of the polymer, which had been detected by x‐ray analysis, was investigated by the use of infrared spectroanalysis. On the basis of deductions derived from these experimental results, we hypothesized a macromolecular structure for this polyether.
Apparatus for studying the effects of rapid thermal cycles and high strain rates on the elevated temperature behavior of materials
Authors: Savage Warren F.
Published: April 2003

A new research tool is described which permits determination of short‐time elevated temperature properties of metals and alloys. Test specimens are heated by their own resistance to the flow of a large magnitude heating current, and a rapid‐acting electronic‐proportioning rate‐control action permits achieving programmed heating of the specimen under test at rates up to and exceeding 3000°F./sec. with negligible thermal overshoot. Complete thermal cycles involving complex programs of alternate heating and cooling may be automatically programmed by means of a special electronic reference generator with a dynamic accuracy of ±15°F. for peak temperatures up to the working limit of existing thermocouple materials. The electronic programming device also initiates testing of the specimen in tension with any desired rate of crosshead motion up to 4.5 in./sec. with loads up to 10,000 lbs. Specimen temperature, load, and crosshead position as a function of time are automatically recorded by a direct—developing recording oscillograph. Examples of recent applications of the apparatus to some metallurgical problems are described briefly, and suggested areas of future application are summarized.
Viscoelastic characterization of solid propellants by transient test techniques
Authors: Jones J. W.
Published: April 2003

The experimental determination of solid propellant viscoelastic physical characteristics using specialized test procedures is described. Experimental and analytical difficulties connected with propellant physical characterization in the millisecond time domain are discussed. Viscoelastic property specification by linear differential operator techniques is described.
The dynamic properties of carbon black loaded natural rubber vulcanizates. Part II
Authors: Payne A. R.
Published: April 2003

The dynamic shear modulus at very high strains, (G∞), of carbon black filler loaded vulcanizates is regarded as due to the product of two factors: (a) a hydrodynamic interaction due to filler particles, and (b) a second factor for which evidence is given suggesting that it arises from a few strong linkages which are known to link filler particles to the matrix. Experimentally a measure of (a) has been obtained from model vulcanizates using glass spheres as the filler, and of (b) from equilibrium swelling measurements on rubber vulcanizates containing carbon black. Quantitatively, the difference between the shear modulus of the pure gum vulcanizate, Gpure gum, and G∞ can be explained by these measurements.
Electromechanical hysteresis measurements: A new tool for investigation of the properties of plastics
Authors: Kern Edward L. , Skinner Selby M.
Published: April 2003

The charge‐strain hysteresis curve can be measured by simple apparatus. While fundamental interpretation of the effect may be complex, the use of the curves for practical purposes such as investigation of fatigue, quality control, differentiation between materials or methods of preparation or surface characteristics, is simple. The effect shows indication of being related to the chemical nature of the material, its composition and structure, and particularly the phase or quasi‐phase structure. Chargestrain hysteresis curves have been measured. These are quite reproducible if the samples from which specimens are prepared are uniform. The shape of the hysteresis curve is affected by (1) amplitude of strain, (2) rate of straining, including constant strains, (3) the functional dependence of strain upon time, (4) repeated cycling, (5) incorporation of fillers, (6) incorporation of reinforcing fibers, (7) the mechanical properties of the plastic, (8) detailed composition of the polymers, and (9) temperature. Seven general types of hysteresis curve are observed. The general features of the curve, and the hysteresis area are sensitive methods for detecting slight changes for composition. This method of sample differentiation was illustrated with examples showing the magnitude and sensitivity of the effect. When a sample was held at a given strain, the charge decreased; this suggests that both resistivity, and the initial stages of mechanical plastic flow may be observed indirectly through this phenomenon. Continuously repeated cycling shows a change in charging‐strain response related apparently to the initial stages of flexural fatigue. A regular decrease of hysteresis area is observed with repeated cycling, with the area decrease depending upon the plastic composition. The rate of decline of the area with repeated cycling is a second method for differentiating between materials, particularly when differences are obscured in other methods of testing.
Novel technique for following the rigidity changes accompanying the curing of polymers
Authors: Lewis Armand F. , Gillham John K.
Published: April 2003

A method is described for measuring the rigidity of a curing polymer system throughout its complete course of reaction (liquid to solid). In this technique, a braided fiber (nylon), impregnated with the polymer system to be studied, is used as the supporting member for a free, torsionally vibrating mass. From the frequency of the vibration, the apparent rigidity modulus Ḡ of the impregnated braid is calculated. The rigidity of the reacting polymer is thus followed nondestructively during the curing period. In a further development, the term relative rigidity Ḡ/Ḡ0 is introduced to normalize the rigidity parameter to a more experimentally adaptable quantity. The curing behavior of several types of polymer is presented to illustrate the general utility of the method.
The attack of ozone on stretched rubber vulcanizates. III. Action of antiozonants
Authors: Braden M. , Gent A. N.
Published: April 2003

The character and extent of protection by certain additives (antiozonants) have been investigated for a number of vulcanized rubbers over a wide range of ozone concentrations. Two distinct modes of action are found: a reduction in the rate of crack growth and an increase in the critical energy necessary for attack to occur. Neither seems explicable on a simple hypothesis of scavenging. Several materials which act in the first manner have been examined. They were found to be similar in effect, reducing the growth rate to about one fifth of its original value when a sufficient amount of the additive was present. The mechanism is obscure. Certain additives, notably N,N′‐dioctyl‐p‐phenylenediamine, also cause a striking and important increase in the critical energy condition. The circumstances under which this occurs have been studied, and a tentative hypothesis for the mode of action is advanced.
Dynamic rheology of modified starches
Authors: Myers Raymond R. , Knauss Carł J. , Hoffman Ray D.
Published: April 2003

Viscosities η and rigidities G were determined for 5% pastes of phosphate‐linked white milo starches and acidmodified cornstarches, using a resonance elastometer operating in the frequency range 0.1 to 40 cycles/sec. Most of the starches behaved as ideal Kelvin solids under these conditions, thereby permitting η and G to be evaluated from the height and location of the resonance peak. Sample calculations of η and G are given, followed by a discussion of the trends displayed by these values as the severity of treatment is increased.
Détermination de la viscosité intrinsèque de solutions de polymères par une simple détermination de la viscosité
Authors: Solomon O. F. , Ciutǎ I. Z.
Published: April 2003

By studying the molecular weights of various solutions of cis‐1,4‐polyisoprene the authors arrived at the formula \documentclass{article}\pagestyle{empty}\begin{document}$$\left[ \eta \right] = \sqrt {2/c} \sqrt {\eta _{sp} - {\rm l}n\eta } _{rel} $$\end{document} which allowed the calculation of the intrinsic viscosity of the polymer solutions by a single viscosity determination. The formula was verified for different systems of polymer–solvent and the values are in accord with those obtained by extrapolation. An operating concentration of about 0.2% is recommended.
Shapes of cells in polymer foams
Authors: Gioumousis George
Published: April 2003

The shape of the cells in a foam is thought to be determined by the interplay between viscosity and surface tension. In order to assess the relative importance of the two, a simplified model is set up which considers only surface tension. It is assumed that the cells are of uniform cross section in one direction and are based on a regular hexagonal lattice in the other two. The resulting two‐dimensional problem is solved by means of the calculus of variations. For high density foams the voids take the form of circles centered within each hexagonal cell. For low densities (below about 9% solids) the solid part is concentrated at the vertices, between tangential circular areas, connected by straight segments of zero thickness. This illustrates the importance of viscosity, since in real foams the cell walls will break if too thin, while the thinner the walls become, the greater is the effect of viscosity in opposing further thinning.
Iterative calculation of relaxation spectrum from free vibration data
Authors: Hopkins I. L.
Published: April 2003

The complex elastic modulus G*(ω) = iG′(ω) + iG′(ω) is shown to be a function not only of the frequency (ω) but also of the damping factor a if the strain is of the form x = x0 exp {− at} sin ωt. The general equations for G*(ω,a) = G′(ω,a) + iG″ (ω,a) = are derived in terms of the relaxation spectrum. The use of a spring to aid the specimen and reduce the ratio a/ω is discussed, and its desirability demonstrated. If data are thus available in terms of either G″(ω) or G″(ω,a) the iterated second approximation of Ninomiya and Ferry provides a rapid and powerful method of finding the relaxation spectrum. To the accuracy to which the time–temperature reduction factor aT is known or can be predicted by means such, for example, as the WLF equation, the function G″(ω,a) over a temperature range at nearly constant frequency can be translated into terms of G″(ω,a) at constant temperature and varying frequency. In such cases, the relatively simple torsional pendulum, or some analogue of it, can economically provide a characterization of the viscoelastic behavior of the material over an extended time or frequency range.
The surface reaction of ozone with chemically protected rubber
Authors: Andrews E. H. , Braden M.
Published: April 2003

Replica electron microscopy has been used to elucidate the physical mechanisms by which various additives afford ozone resistance to natural rubber. There exist two classes of chemical antiozonants, namely, those that enhance the critical energy required for ozone cracking and those that retard the rate of crack growth; representatives of these two classes were used in the investigation. The process involved in the first of these protective mechanisms was found to be the formation at the exposed surface of an inextensible layer some 100 A. thick and inert to further ozone attack. That giving rise to rate retardation also involved the formation of a surface layer, but the layer was susceptible to further ozonolysis and, eventually, complete degradation.
Quantitative characterization of polybutadiene networks
Authors: Kraus Gerard
Published: April 2003

Using a relationship found to be applicable for natural rubber networks in establishing contributions of chemical crosslinking, entanglements, and networks defects to physical crosslinking, a physical versus chemical crosslinking “calibration” is developed for polybutadiene prepared by organolithium initiation. This calibration is then used to determine chemical crosslink yields for sulfur‐sulfenamide, thiuram, and peroxide vulcanization. Crosslink yields for polybutadiene in the sulfur‐sulfenamide and thiuram curing systems are shown to be similar to those of natural rubber. In peroxide vulcanization the crosslink yield is in excess of unity for polybutadiene. Evidence is presented which indicates that this is due to a polymerization type reaction involving vinyl groups resulting from 1,2‐addition during polymerization.
Radical decay and color formation at various temperatures in unplasticized poly(vinyl chloride) irradiated in vacuo at 25°C
Authors: Atchison G. J.
Published: April 2003

Moldings were irradiated at ambient temperature in vacuo with 2 m.e.v. electrons to doses of 5.9–7.3 Mrad. The decay of radicals was followed by EPR spectroscopy at 80, 55, and 30°C. while simultaneous extinction measurements were made at 300–700 mμ with a recording spectrophotometer. The radical decay data indicated the presence of three species at each temperature, decaying exponentially with time, with half‐lives of 20 min., 210 min., and 135 hrs. at 80°C. of 40 min., 400 min., and 141 hrs. at 55°C., and of 54 min., 720 min., and 3200 hrs. at 30°C. G values of 1.6, 2.0, and 1.4 were obtained for radical formation at 25°C. by back‐extrapolation of decay curves from the three temperatures to the end of the irradiation period. The activation energy of radical decay was found to be 4.4, 5.0, and 13.7 kcal./mole for the short‐lived, intermediatelived, and long‐lived radicals, respectively. The optical data has a broad absorption maximum at 500–550 mμ and a series of seven absorption peaks with maxima at 505–510, 483–485, 458–460, 430–435, 400–405, 364–365, and 329–330 mμ. The concentration of the material producing the broad bands was found to be inversely proportional to the long‐lived radical concentration. The fine‐structure peaks are consistent with literature data for a polyene chain of 16–17 conjugated double bonds.
Development of constitutive equations for polymeric melts and solutions
Authors: White J. L. , Metzner A. B.
Published: April 2003

The importance and characteristics of viscoelastic fluid behavior are briefly reviewed, as are theoretical predictions of the relationships between the stresses developed in such a fluid and its deformation rate and history. It is seen that most of the equations available for the prediction of these stresses(variously termed “constitutive equations” or “rheological equations of state”) either do not predict the properties of real materials correctly or, alternately, are of such overriding complexity that they cannot be applied to the solution of any but the simplest real problems. A new constitutive equation in which all the significant parameters may be evaluated from only two sets of experiments is developed. Comparison with available experimental results, while not entirely conclusive, indicates that the equation may predict correctly the behavior of nonpolar solutions and polymeric melts and that it may work well on polar systems in the range of high deformation rates, i.e., the region of primary industrial interest. Several problems of interest to the plastics industry are worked to illustrate the use of this constitutive equation.
Evaluation of light‐scattering and small‐angle x‐ray techniques using dilute dispersions of uniform polystyrene latices
Authors: Sperling L. H.
Published: April 2003

Several light‐ and x‐ray‐scattering formulations were evaluated using polystyrene spheres having diameters near the wavelength of the employed light. While some error in the dimensions calculated using these equations is both expected and found, it is shown that these methods may still be useful for approximate or relative results. One of the purposes of this paper will be to estimate the applicability of these light‐scattering techniques to colloidal systems having sizes near the wavelength of light when only moderate accuracy is required. It is shown that the better diameter estimations are obtained by using (1) the maxima and minima that appear in the angular light‐scattering pattern, or (2) the Shull and Roess formulation adopted from small‐angle x‐ray theory
Polymerization of dialdehydes by metal alkyls
Authors: Sweeny W.
Published: April 2003

A variety of metal alkyls have been found to be catalysts for preparing a polyester from terephthalaldehyde via the Tischenko reaction. The polymer was examined by infrared spectra, x‐ray diffraction patterns, and differential thermal analysis, and is apparently a crystallizable random 50 : 50 copolymer composed of p‐methylenebenzoate and p‐xylyleneterephthalate units. Diphenyl‐4,4,‐dicarboxaldehyde also underwent polymerization with the metal alkyls, but a hindered aldehyde, 4,6‐dimethylisophthalaldehyde, did not and was recovered quantitatively.
Reactions of irradiated polytetrduoroethylene resin
Authors: Bro M. I. , Lovejoy E. R. , McKay G. R.
Published: April 2003

Powders and compacted preforms of virgin unmelted polytetrafluoroethylene were subjected to ionizing radiation in high vacuum. The specific gravities, melt Visccmities, and mechanical strengths of the irradiated samples after a standard heating cycle in air or at reduced pressures indicate that degradation is more pronounced in the presence of oxygen than in vacuum. The presence of oxygen in the excessively degraded sample was shown by electron spin resonance and pyrolysis experiments. It is suggested that some branched molecules are also formed on heating the irradiated samples resulting in a broadening of the molecular weight distribution. Primary fluorocarbon radicals of the type . disappear rapidly when heated at 75°C. in vacuum while secondary radicals are stable thermally at 200°C. and disappear only slowly at 400°C. Both typea of radicals react rapidly with oxygen and tetrafluoroethylene at 0°C. The reactions which occur in irradiated polytetrafluoroethylene in various atmospheres and at several temperatures are reviewed in light of the information developed during this research.
Cleavage of disulfide polymers. II. By thiols
Authors: Fettes E. M. , Mark H.
Published: April 2003

The study of the interchange reaction of thiols with disulfides is extended to include additional thiols and conditions for redistribution. In aqueous suspension, polymeric disulfides are reduced in molecular weight to widely different extents by thiols of varying structures. Water‐soluble thiols as mercaptoethanol, and tertiary thiols as t‐butyl mercaptan, are relatively ineffective in cleaving. The presence of sodium disulfide with some of the thiols, particularly the thiophenols and 2‐mercaptobenzothiazole, retarded cleavage by the thiols. A study of the molecular weight of the polymer as the cleavage by thiols proceeded indicated that short chain lengths were gradually removed from the surface of the polymeric particles. The partial cleavage of a disulfide polymer by a mixture of sodium sulfite and sodium hydrosulfite produces a disulfide polymer of lower molecular weight and terminal thiol groups. This product should be capable of self‐redistribution to a random distribution. The liquid polymer resulting from the cleavage had a high heterogeneity index (M̄w/M̄n). Efforts to randomize in bulk to the theoretical index of 2.0 by heat, ultraviolet light, water, and amines were not successful. It was found possible to effect the reaction of the disulfide polymer with butyl mercaptan in solution in dioxane with sodium phenolate as catalyst. The conclusion is drawn that the reaction of a thiol with a disulfide, both in aqueous suspension and in dioxane, is ionic rather than radical.
X‐ray determination of crystallinity in poly(ethylene terephthalate)
Authors: Bosley D. E.
Published: April 2003

Three recently published x‐ray methods for determining the crystallinity of poly(ethylene terephthalate) are discussed and compared with density and infrared methods. The effect of crystallite size is shown to account for most of the disagreement among the several methods. A short method of estimating crystallinity from x‐ray diffraction, suitable for counting techniques and requiring only two measurements, is presented and compared with the density method.
Master curves for some amorphous polymers
Authors: Takahashi M. , Shen M. C. , Taylor R. B. , Tobolsky A. V.
Published: April 2003

Master curves for polystyrene, poly(methyl acrylate), and poly(methyl methacrylate) in stress relaxation are reported. The method used to obtain a wide range in modulus is to combine torsional creep data for high modulus regions with direct stress relaxation data for low moduli. The composite curves obtained are compared with existing literature data. The master curve for polystyrene obtained by a ball indentation method is also reported. Characteristic viscoelastic parameters derived from the data are tabulated.
Rate of crosslinking of gelatin in aqueous solution
Authors: Robinson Ian D.
Published: April 2003

The rate of crosslinking of concentrated gelatin solutions in water has been measured by means of a gelation timer. Some effects of temperature, pH, crosslinking agent, and gelatin concentration have been measured. The crosslinking agents have varied from fast‐acting chrome alum, glutaraldehyde, and a carbodiimide to slow‐acting mucobromic acid and dialdehyde starches. Detailed crosslinking mechanisms are discussed for dimethylol urea, mucobromic acid, and several dialdehyde crosslinking agents. Some effects of urea and other additives on the dimethylol urea crosslinking rate are described.
Measurement and interpretation of nonlinear mechanical energy losses in high polymer fibers
Authors: Moseley Walter W.
Published: April 2003

Dynamic mechanical loss measurements were made on fibers at large tensile strains which caused nonlinear viscoelastic behavior. Measurements on fibers from polyethylene, polypropylene, nylon 66, nylon 4 and an experimental polymer led to seven energy loss peaks for each sample in the temperature range of 120–350°K. The peaks were evenly spaced in temperature at intervals of 30–35°K. rather than at unequal temperature intervals of approximately 100–150°K. normally observed under conditions of linear viscoelastic behavior. In every case, the array of evenly spaced peaks occurred only at temperatures below the glass transition temperature. The temperatures at the energy loss peaks were virtually independent of crystallinity and molecular orientation and were interpreted in terms of polymer molecular structure. The data could be explained only by a single mechanism, common to all polymers, which could operate in a quantized manner, e. g., diffusional motion of molecular chain segments. To account for the constant temperature spacing between peaks of a given sample, it was necessary to assume that the rate controlling step in the energy loss process is the return of a displaced segment to equilibrium. Calculations from the experimental data indicated that peaks at higher temperatures stem from displaced molecular segments which experience high potential energy barriers and which have to be excited to higher skeletal vibrational energies to overcome the barrier. Precedence for this interpretation is provided by Tanaka and Ishida, who have associated molecular vibrations with the well‐known β loss peaks in polymers.
Influence of melt spinning variables on the tensile properties of high density polyethylene fibers
Authors: Higgins T. D. , Bryant G. M.
Published: April 2003

The tenacity and stiffness modulus of yarns melt‐spun from high density polyethylene are functions of the sum of the logarithm of the take‐up velocity in melt drawing and the true (logarithmic) deformation imparted in the cold‐drawing process (i.e., stretching at a temperature below the polymer melting temperature). Thus, for the conditions investigated the effective melt drawing deformation is independent of the calculated velocity of the melt in the spinneret orifices. The maximum cold draw ratio is shown to be a function of the production rate, increasing to a maximum value and then decreasing as the production rate is increased. The maximum cold draw ratio at a given production rate is found to be a function of the yarn temperature and the deformation introduced in melt drawing. The tenacity and stiffness modulus of yarns melt‐spun from polypropylene may also be expressed as functions of the summation of the logarithm of the take‐up velocity of melt drawing and the true deformation imparted in cold drawing. The orientation, as measured by birefringence, of yarns spun from an experimental polyester are a function of the ratio of the take‐up velocity and the orifice velocity, wheras the same measurement of the orientation of polyethylene is a function of the extrusion velocity alone. Equations of state for the tenacity and stiffness modulus of melt‐spun polyethylene yarns were found to be of the same form as for a wet‐spun madacrylic fiber.
Analysis of the finite cone‐plate viscometer and of the finite parallel‐plate viscometer
Authors: Slattery John C.
Published: April 2003

The analyses for flow of a simple fluid of Noll both in the infinite cone‐plate viscometer and in the infinite parallel‐plate viscometer are shown to be consistent with the existence of a free surface in the finite instruments. Neglected in the description of the free surface are: the effect of any gradients in surface tension, the effect of the rate‐of‐deformation of the free surface upon the surface stress tensor, the effect of mass transfer at the free surface, inertial and gravitational effects in the free surface, and distortion of the free surface at solid boundaries.
Strainwork dependence of filler‐loaded vulcanizates
Authors: Payne A. R.
Published: April 2003

The modulus and loss angle of carbon black filler‐loaded rubbers varies with the dynamic amplitude of oscillation. The dynamic modulus change with amplitude is of a sigmoid nature. This allows the data to be reduced by a normalization technique. It is the purpose of the paper to show how the normalized data are substantially independent of the carbon black loading and of the polymer type when the normalized modulus is plotted against the energy of deformation (or strainwork).
Radiochemical yields of graft polymerization reactions of cellulose
Authors: Arthur Jett C. , Blouin Florine A.
Published: April 2003

The preparation of radiation‐induced graft polymers of cotton cellulose, while retaining the fibrous nature and high molecular weight of the cellulose, depended primarily on the radiochemical yields of cellulose reactions and of graft polymerization reactions. Yields of the initial major molecular changes in cellulosic polymer indicated that, in the case of scission of the molecule and carboxyl group formation, chain reactions were not initiated by radiation; however, in the case of carbonyl group formation chain reactions were initiated but quickly terminated. Generally, experimental procedures, used in graft polymerization reactions, were: (1) simultaneous irradiation reactions, that is, application of monomers or solutions of monomers to cellulose or chemically modified celluloses, then irradiation; and (2) post‐irradiation reactions, that is, irradiation of cellulose or chemically modified celluloses, then after removal from the field of radiation, contacting the irradiated cellulose with monomer. Some of the most important factors influencing the radiochemical yields of graft polymerization reactions of styrene and acrylonitrile onto cellulose were: concentration of monomer in treating solution; solvent; ratio of monomer solution to cellulose; prior chemical modification of cellulose; and absence of oxygen, particularly in post‐irradiation reactions. Experimental data were presented, and the direct and indirect effects of Co60 γ‐radiation on these reactions were discussed.
Oxygen‐transfer resins, a new type of oxidation–reduction polymers
Authors: Helfferich F. , Luten D. B.
Published: April 2003

Bifunctional cation exchangers with carboxylic and sulfonic acid groups can be oxidized with aqueous hydrogen peroxide which converts the carboxylic to percarboxylic acid groups. The oxidized resins can be used to hydroxylate compounds with olefinic double bonds to form α‐glycols. The resins thus transfer active oxygen from a peroxide to an unsaturated substrate. Oxidation and reduction of the resins is reversible.
Thermal degradation of fluorine‐containing polymers. Part I. Degradation in vacuum
Authors: Cox J. M. , Wright B. A. , Wright W. W.
Published: April 2003

The thermal degradation in vacuum 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 methods of assessment of the weight loss results are discussed. The most stable of the polymers are those which are fully fluorinated.
Methyl α‐cyanoacrylate. II. Copolymerization studies
Authors: Kinsinger J. B. , Panchak J. R. , Kelso R. L. , Bartlett J. S. , Graham R. K.
Published: April 2003

Copolymerization of methyl alpha;‐‐cyanoacrylate with five reference monomers gave values e = +2.1 and of log Q = 0.65, with much scatter in the latter value. Alternating copolymers are formed by copolymerization with monomers of e = −0.8 or less. Bulk copolymerization with such monomers could not be accomplished, as a rapid noncatalyzed polymerization occurred upon mixing even at 0°C. Random copolymers with methyl methacrylate could be prepared in bulk; those with ca. 10% methyl methacrylate had physical properties similar to the homopolymer of methyl α‐‐cyanoacrylate, except that the heat distortion temperature was lowered 10–15°C. The alternating copolymers were more thermally stable than the random copolymers. Glass temperature values for alternating copolymers do not appear to agree with values predicted from equations for random copolymers.
Viscosity—molecular weight relationship for masticated natural rubber
Authors: Bristow G. M. , Westall B.
Published: April 2003

Intrinsic viscosity and osmotic molecular weight data are presented for toluene solutions of several types of natural rubber after mastication in air. For [η] < ca. 4 all these data fit the relationship, [η] = 7.11 × 10−7 M̄n1.25. At higher molecular weights deviations from this relation are found, the extent of which depend on the type of natural rubber used. These deviations are attributed to differences in initial molecular weight distribution.
Products of flash pyrolysis of phenol–formaldehyde by time‐of‐flight mass spectroscopy
Authors: Friedman Henry L.
Published: April 2003

A sample of phenol‐formaldehyde was flash‐pyrolyzed 11 times in the reaction chamber of a time‐of‐flight mass spectrometer. Quantitative analyses were determined for pyrolysis products which were present within 10 sec. after each flash. A high degree of consistency between compositions of products from consecutive flashes resulted. The significance of the results is discussed.
Birefringence, density, and tensile characteristics of oxycelluloses
Authors: Betrabet S. M. , Munshi V. G. , Daruwalla E. H. , Jacob C. J.
Published: April 2003

Investigations have been carried out on the changes in the characteristics such as refractive index, density, single fiber breaking strength, and moisture regain of cotton fibers brought about as a result of oxidation with sodium metaperiodate and potassium dichromate‐oxalic acid. The study has also been extended to sodium chlorite‐treated and sodium borohydride‐reduced oxycelluloses obtained from these oxycellulose products. Results indicate that in case of sodium metaperiodate oxidation, birefringence and density first increase, reach a maximum and then decrease sharply as oxidation is continued, while breaking strength decreases in the initial stages, reaches a minimum, and then increases in the later stages. With dichromate‐oxalic acid oxidation, birefringence increases sharply during the initial stages of oxidation and after reaching a maxima, decreases as oxidation progresses, while there is a rapid increase in the values of density during the initial stages followed by a slow rise as oxidation is continued. In case of dichromate‐oxalic acid oxycelluloses, breaking strength decreases continuously with the progress of oxidation. Results are interpreted in terms of changes in gross morphology and fine structure of cotton as a result of oxidation and subsequent chlorite and borohydride treatments.