bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural characterization of vulcanizates. Part IV. Use of triphenylphosphine and sodium di‐n‐butyl phosphite to determine the structures of sulfur linkages in natural rubber, cis‐1,4‐polyisoprene, and ethylene–propylene rubber vulcanizate networks
Authors: Moore C. G. , Trego B. R. 
Published: April 2003

AbstractDeterminations of the degree of chemical crosslinking and crosslinking efficiency values E (i.e., the number of sulfur atoms combined in the network per chemical crosslink present) have been used in conjunction with the chemical probes triphenylphosphine and sodium di‐n‐butyl phosphite to establish the structural features of sulfur links in vulcanizate networks derived from a variety of accelerated natural rubber–sulfur systems, from a cis‐1,4‐polyisoprene–TMTD–zinc oxide system, and from natural rubber and ethylene–propylene rubber crosslinked with a dicumyl peroxide–sulfur system. The triphenylphosphine converts polysulfide links into monosulfide and, to a lesser extent, disulfide links. The values of E′, i.e., the number of sulfur atoms combined in the network per chemical crosslink present after triphenylphosphine treatment are, therefore, a measure of the extent of main‐chain modification in the network by cyclic monosulfide groups and/or pendant groups of the type: SxAccel. (where x ≥ 1 and Accel. is an accelerator fragment). Sodium di‐n‐butyl phosphite cleaves di‐ and polysulfide crosslinks but leaves monosulfide and carbon–carbon crosslinks intact, and thus determination of the degree of chemical crosslinking before and after treatment with this reagent yields estimates of these two different classes of crosslinks. The combined results indicate that the efficiency of utilizing sulfur for crosslinking and, therefore, the structural complexity of the derived networks are very sensitive to the nature of the vulcanizing system (type and relative concentrations of crosslinking agent, accelerator, and activator) and vulcanizing conditions (time and temperature of cure). In general, the proportion of crosslinks which are di‐ and/or polysulfidic decreases with increasing cure time, and for the accelerated sulfur systems the structural complexity of the network increases with cure time, especially at higher vulcanizing temperatures and with low concentrations of fatty acid activator.
Wet oxidation of undrawn nylon 66 and model amides
Authors: Mikolajewski E. , Swallow J. E. , Webb M. W. 
Published: April 2003

AbstractUndrawn nylon was found to be susceptible within a few days to degradation in wet or humid conditions at temperatures between 50 and 90°C. Model N‐substituted amides, although not affected by these conditions, were attacked by hydrogen peroxide solutions. The degradation proceeded principally by rupture of the bond between the nitrogen of the amide and the carbon of its α‐methylene group, consequent upon oxidation at this carbon. Unsubstituted primary amide, carboxyl, and aldehyde endgroups were formed, together with ammonia by hydrolysis of the oxidized amide. The bond between the α and β carbons of an N‐methylene chain also suffered breakage, giving formic acid and carbon dioxide. The former could also arise by rupture of any initially produced N‐formyl or N‐formoyl amides. The appearance of lactic acid from butylacetamide showed that oxidation could proceed along the N‐alkyl chain. Fragments of suitable size broken from the main chain of nylon became water‐soluble and relatively stable to further attack by air or oxygen. These pieces essentially retained the nylon structure, but possessed two carboxylic ends and an average molecular weight of less than 600. A maximum oxygen uptake of about 30 moles per mole of original amide was calculated, corresponding to complete conversion into these soluble fragments. Significant degradation did not occur for many months at 60°C. in dry conditions or in solutions of 8‐hydroxyquinoline, a process which has been patented. The latter was considered to function by chelating heavy metals into an inactive form and inhibiting peroxide formation.
Solution of gases in oriented poly(ethylene terephthalate)
Authors: Vieth W. R. , Alcalay H. H. , Frabetti A. J. 
Published: April 2003

AbstractThe solubilities of nitrogen, oxygen, argon, methane, and carbon dioxide in thin films of crystalline oriented poly(ethylene terephthalate) in the glassy state were studied by the static sorption method. High pressure sorption isotherms were obtained for carbon dioxide. Results indicate that, above a certain film thickness, solubilities of all gasses in the crystalline oriented polymer (Mylar) are virtually identical to those in the unoriented crystalline polymer. Solubility constants are correlated with gas force constants, ϵ□k, and the heats of sorption obtained for methane and carbon dioxide are nearly the same for both the oriented and unoriented films. The sorption isotherms obtained for carbon dioxide are nonlinear but may be well described by considering dual sorption modes. One of these, ordinary dissolution, is described by Henry's law, while the other, “hole filling,” is characterized by a Langmuir expression. Solubilities of carbon dioxide in the thinnest oriented films (1 mil) are markedly higher than in the unoriented film. Analysis of the sorption data indicates that both the hole saturation constant, and the hole affinity constant, are larger in the 1‐mil oriented film. The amorphous phase appears to be different also, exhibiting a larger capacity for dissolved gas. Different thermal history, relating to the manufacture of the film, is advanced as a possible explanation for increased solubility.
Polymerization activity test for vinyl chloride
Authors: Georgieff K. K. 
Published: April 2003

AbstractA polymerization activity test has been developed for evaluating the purity of commercial vinyl chloride. A 40‐g. portion of vinyl chloride is heated with 0.500 g. of benzoyl peroxide for 2 hr. at 70°C. in a glass liner in a stainless steel autoclave, and the weight of the polymer formed determined. The effects of the heat transfer medium in the autoclave, time, oxygen, limited agitation, catalyst concentration, and temperature on the percentage conversion of monomer to polymer were determined. The effect of acetaldehyde, crotonaldehyde, chloroprene, 1,1‐dichloroethane, trans‐1,2‐dichloroethylene, paraldehyde, and 1,1,2‐trichloroethane on the conversion and the molecular weight of the polymer are described.
Crystallization and melting of copolymers of polyoxymethylene
Authors: Inoue Masakazu 
Published: April 2003

AbstractCopolymers of polyoxymethylene were prepared from trioxane in the presence of comonomers such as dioxolane, 1,3‐dioxane, dioxepane and epichlorohydrin, boron trifluoride etherate being used as catalyst. Fusion and crystallization phenomena were studied on these copolymers by use of density measurement, differential thermal analysis, dilatometry, and microscopy. The spherulite growth rate and the induction periode of the crystallization were determined. The temperature dependence of the growth rate was calculated assuming a two‐dimensional surface nucleation mechanism.
Thiol group formation in the vulcanization of natural rubber
Authors: Chakravarty Shomnath , Banerjee D. , Sircar Anil K. 
Published: April 2003

AbstractThe determination of thiol groups formed during vulcanization in the complete range of 3–35 parts sulfur per hundred rubber–sulfur stock is reported. The results are explained on the basis of Fisher's mechanism for vulcanization of rubber and the assumption of three stages in the vulcanization process depending on the sulfur concentration.
Fiber melt extrusion: Deviations from steady‐state behavior in the spin line
Authors: Freeman Howard I. , Coplan Myron J. 
Published: April 2003

AbstractThe occurrence of nonsteady‐state conditions in the melt extrusion of fibers is described. Data obtained from cinephotographs are presented which indicate that the spin line diameter at a fixed point in space can have wide fluctuations dependent upon spinning parameters. It is postulated that the interaction of an elastic bulge and variable spin line tension due to a melt inhomogeneity may be responsible for the effect. Some evidence for melt inhomogeneity is presented to demonstrate the existence of domains having flow properties different from the main mass of polymer melt.
Molecular weight distribution of a polyester
Authors: Hansen Charles M. , Sather Glenn A. 
Published: April 2003

AbstractCombined solvent composition and column temperature gradients were employed to effect the efficient fractionation of a polyester into several molecular weight fractions in about 16 hr. Mixtures of methyl ethyl ketone and cyclohexane were used as eluents for the fractionation which was conducted in a copper column packed with glass beads. In previously reported polymer fractionations with solvent and temperature gradients the temperatures at all points in the column have been either above or below the melting point of the polymer. This study demonstrates that hexanediol–succinic acid polyester may be efficiently fractionated by using a column temperature range which brackets the melting point of the polymer.
Some observations on the melting behavior of textile fibers. Part II. X‐ray examination of hot‐stretched nylon 66
Authors: Warwicker J. O. 
Published: April 2003

AbstractX‐ray diagrams of different samples of nylon passed over a hot‐plate held at different temperatures show that the observed effect depends on the type of nylon used. Clear evidence consistent with the melting of the core of the nylon is obtained for monofilament.
Solvent power of solvents for poly(vinyl chloride)
Authors: Moore W. R. , Hutchinson R. J. 
Published: April 2003

AbstractOsmotic, viscometric, and initial phase separation studies of dilute solutions of poly‐(vinyl chloride) in cyclohexanone, cyclopentanone, tetrahydrofuran, morpholine, nitrobenzene, and tetrahydropyran are reported together with some swelling measurements involving these solvents and dioxane, acetone, and methanol. Values of the polymer–solvent interaction parameter χ1 obtained from osmotic and swelling measurements suggest the order of solvent power for poly(vinyl chloride) to be cyclohexanone > cyclopentanone > tetrahydrofuran > morpholine > nitrobenzene > tetrahydropyran. A similar order is suggested by the volumes of hexane required to cause initial phase separation. Values of intrinsic viscosity and of the viscosity slope constant k′ give somewhat different orders of solvent power. Reasons for differences in order are considered. The correlation of the volume of hexane required to cause initial phase separation with χ1 is discussed and it is suggested that the polymer is solvated in solution. Other factors affecting the solvent power of solvents for poly(vinyl chloride) would appear to include the bulk and the solubility parameter of the solvent.
Ethylene–propylene copolymers: Crystallinity, infrared, and creep studies
Authors: Linnig Frederic J. , Parks Edwin J. , Wood Lawrence A. 
Published: April 2003

AbstractDensity, infrared, and creep studies have been made of ethylene–propylene copolymers containing up to about 50 mole‐% propylene and their homopolymers. The degree of crystallinity (volume fraction of polyethylene crystals), as measured by density and x‐ray studies, decreases with increased propylene content. This change is also reflected in the intensity of the 13.7 μ band in the infrared spectra of the polymers. The measured amount of unsaturation (0.1–0.2%) in the copolymers is too small to account for the presence of several infrared bands which are often attributed to unsaturation. An unsaturation of 0.90% was obtained for a terpolymer where the third component was unsaturated. Indentation–creep studies showed the creep to be nearly proportional to the logarithm of time with a slope of 10% creep per decade for 0.1–10 min. Compliance–temperature graphs were found to be quite similar to those for the styrene–butadiene rubber SBR 1500.
Gas permeability of highly oriented dibutyl maleate–ethylene copolymer films
Authors: Michaels A. S. , Vieth W. R. , Bixler H. J. 
Published: April 2003

AbstractThe effects of extreme uniaxial orientation on gas permeation through dibutyl maleate–thylene copolymer films have been examined. Gases employed were helium, argon, and methane. Permeability constants were measured as functions of temperature between 25 and 55°C., in unstretched film and in films stretched to elongations of 490, 512, 540, and 608% (breaking point). Uniaxial cold drawing of dibutyl maleate–ethylene copolymer films into the stable necking region (elongation ca. 490%) causes only a small (30%) decrease in permeability and virtually no change in apparent activation energy of permeation; when the necked films are further stretched to elongations approaching the breaking point (ca. 600%), a significant decrease in permeability and increase in activation energy is observed. It is deduced that the major changes in crystalline texture and arrangement which this polymer undergoes in the necking process have only a minor effect upon total level of crystallinity, amorphous‐phase properties, and diffusional impedance offered by the crystallites, suggesting that changes in crystallite orientation, perfection, and shape throughout the drawing process are compensatory. When necked polymer is further stretched, however, severe restraints are imposed upon the mobility of oriented chain segments in the amorphous regions, which are primarily responsible for the observed large changes in permeabilities and permeation activation energies.
Sedimentation analysis of styrene–butadiene copolymer rubber
Authors: Homma Terutake , Kawahara Kazuo , Fujita Hiroshi 
Published: April 2003

AbstractMethyl n‐propyl ketone (MNPK) at 21°C. and methyl isobutyl ketone (MIBK) at 46°C. are found to be theta conditions for a styrene–butadiene copolymer rubber commercially designated as SBR‐1500. Data for specific refractive index increment and density indicate that these solvents are appropriate for ultracentrifugation of this polymer by the method of schlieren optics. Sedimentation measurements are made on one whole polymer and six fractions in MNPK at 21°C. It is demonstrated that in this theta solvent the distribution of sedimentation coefficient s (at the limit of zero concentration) of a given SBR‐1500 can be determined, with a good accuracy, from a single sedimentation run at one nonzero concentration below 0.4 g./dl. A relation between s and molecular weight M necessary to convert this distribution of s to the distribution of M is derived by making use of the theory of Flory which correlates s limiting viscosity number, and M. It is believed that the theta conditions and the procedure of analysis presented in this paper are readily utilized for heterogeneity studies on this particular type of synthetic rubber SBR‐1500.
Thermal degradation of resins
Authors: Learmonth G. S. , Wilson T. 
Published: April 2003

AbstractDifferential thermal analysis and thermogravimetric analysis techniques were investigated with a view to predication of the thermal behavior and flammability of plastics materials. Paper‐reinforced phenolic and epoxide resins were used. It was found that with phenolic laminates the pattern of the thermograms was characteristic of the paper, while with epoxide laminates (and melamine) it was characteristic of the resin used. This cannot be correlated with fireproofness or flammability, and further work is necessary to establish better techniques and to study the thermal behavior of the laminates by service testing.
Network degradation accompanying the vulcanization of natural rubber with a sulfur–diphenylguanidine system
Authors: Scott Kenneth W. , Lorenz Otto , Parks Carl R. 
Published: April 2003

AbstractSol fraction and swelling values have been determined for a series of natural rubber–sulfur–diphenylguanidine vulcanizates. These data have been analyzed in terms of the Charlesby and Pinner gel network formation theory with a view to estimating the amount of permanent molecular chain scission accompanying the vulcanization. It is concluded that negligible chain scission occurs before the point of modulus reversion of these curves. In the region of cure reversion, permanent molecular chain scission does occur to a small extent. The principal factor responsible for cure reversion in this vulcanizate is crosslink scission. Chain scission is responsible for only about 3–8% of the observed cure reversion.
Chemistry of radiation crosslinking of branched fluorocarbon resins
Authors: Lovejoy E. R. , Bro M. I. , Bowers G. H. 
Published: April 2003

AbstractA number of commercial and experimental fluoropolymers were subjected to ionizing radiation at elevated temperatures and the changes in melt viscosity were measured as an indication of the degree of crosslinking or degradation which occurred. Polytetrafluoroethylene, polychlorotrifluoroethylene, polyhexafluoropropylene, and a copolymer of hexafluoropropylene with perfluoroheptene‐1 decrease in melt viscosity when irradiated at 200–250°C., while copolymers of tetrafluoroethylene with hexafluoropropylene, octafluorobutylene, or perfluoroheptene‐1 increase in melt viscosity, indicating crosslinking. The results suggest that the reaction of species of the type · (where × is F or CF3) with is the important one leading to crosslinking.
Poly(oxatetramethylene) glycol. I. Influence of water on polymerization catalysis
Authors: Johnston Peter R. 
Published: April 2003

AbstractTetrahydrofuran (THF) was polymerized with cocatalysts of ethylene oxide (EO) and BF3, using THF as the solvent. The yield of polymer, based on the amount of catalyst, was very low. With water present (0.5 mole per mole of BF3 and EO) the yield increased fourfold. Polymerization was stopped by the addition of a large amount of water; the addition of water also provided the polymer with terminal hydroxyl groups. The polymer had a molecular weight of 1000 and was a clear, colorless, viscous liquid.
Effects of degradation on polypropylene melt rheology
Authors: Poller D. , Kotliar A. M. 
Published: April 2003

AbstractThe viscous flow behavior of molten polypropylene has been correlated with the viscosity‐average molecular weight under degradative and nondegradative conditions. The effects of unequal extents of degradation on molecular weight distribution are shown to be an important parameter in this correlation.
Microscopic domains in some synthetic polymers
Authors: Rochow T. G. 
Published: April 2003

AbstractIt was found that all pieces of poly(methyl methacrylate) have structure and anisotropy, no matter how they were made. There is no continuum, only differences of opinion about what the discontinuities represent. Judging from these and other results and pending the results of further experiments, the author is of the opinion that he has uncovered both macromolecular and micellar domains in poly(methyl methacrylate).
Calculation of number‐average and weight‐average molecular weight of poly(vinyl chloride) polymers from intrinsic viscosity measurements
Authors: McKinney Paul V. 
Published: April 2003

AbstractConsistent data are available from several authors to provide equations for the calculation of number‐average and weight‐average molecular weights of commercial poly(vinyl chloride) polymers from determinations of intrinsic viscosity in cyclohexanone solution at 30°C. Reasonable approximations of the molecular weights can be calculated quickly by use of the following simple equations: M̄n = ½[η] × 105; M̄w = 0.9[η] × 105.
Polymer‐diluent interactions of some nitrocellulose‐nitrate ester systems
Authors: Brooks R. L. , Lawrence A. R. 
Published: April 2003

AbstractThe Flory‐Huggins interaction χ and the closely related heat of mixing parameter B were determined for several nitrocellulose‐nitrate ester systems. A micromethod which permitted the use of a simplified version of the Flory equation was successful in evaluating the effects of two series of nitrate ester diluents with nitrocellulose. A distinct difference exists between the effect of αω‐ and α,β‐substituted diluents as shown by the χ and B parameters. Generally, the terminally substituted nitrate esters appear to be the better solvents.
Grafting of chelating monomers to styrene—butadiene latexes
Authors: Gardner John B. , Harper Billy G. 
Published: April 2003

AbstractIt has been previously reported that vinyl esters have been grafted to natural rubber latex. We have grafted two other types of vinyl monomers to styrene‐butadiene latex. These monomers are the ammonium salts of acrylic acid and methacrylic acid, and the ammonium salts of vinyl chelating agents, such as N‐(ar‐vinylbenzyl)iminodiacetic acid. (Ionizing radiation doses of 0.5–2 Mrad are sufficient to accomplish the grafting.) These monomers, in the range of 2–6%, give very definite improvement in adhesion to metals. They also improve the rust resistance, and when pigmented with an iron oxide dispersion, improve the whitening resistance of the coating. The vinyl chelating monomers give the best improvement over the untreated latex, particularly in the resistance to whitening. The optimum amount of monomer is 4–6%. This compares very well with the theoretical amount for a monomolecular layer of monomer surrounding each latex particle.
Procedures to guide experiments directed to improvement of electrostatic atomization and deposition of organic coatings
Authors: Spiller Lester L. 
Published: April 2003

AbstractMethods are described for determination of particle size D of paint atomized in an electrostatic field and for measurement of band width B and wraparound ratio W of a film pattern produced under standard conditions. A quantitative “figure of merit” F, defined as the ratio BW/D, can be correlated with qualitative aberrations of electrospray efficiency. This quantitative measure provides a more efficient guide to experiments directed toward upgrading electrospray performance of otherwise useful paints. Some examples are cited to demonstrate that incorporation of highly charged colloidal particles have significant effects on electrospray efficiency of paints containing vehicles of low conductivity.
Properties of semicrystalline polyolefins. II. Copolymers of 3‐methyl‐1‐pentene and 4‐methyl‐1‐pentene
Authors: Isaacson R. B. , Kirshenbaum I. , Klein I. 
Published: April 2003

AbstractA study of the copolymerization of 3‐methyl‐1‐pentene (3‐MP) and 4‐methyl‐1‐pentene (4‐MP) showed that the poly‐4‐MP crystal lattice is capable of incorporating large quantities of 3‐MP without a sharp lowering of melting point or adverse effect on physical and mechanical properties. The reactivity ratio of the two monomers in copolymerization are r(4‐MP) = 6.2 ± 0.2 and r(3‐MP) = 0.1 ± 0.1. As a result, mixed feeds containing up to 80% 3‐MP produce copolymers composed primarily of repeating 4‐MP units, with a random insertion of 3‐MP monomer units. Calculations indicate that in a copolymer containing 37% 3‐MP, the probability of finding a sequence of 2 units of 3‐MP is only a little better than 5%. This copolymer shows a somewhat increased resistance to deformation under load than homopoly 4‐MP. Its crystalline melting point is 248°C.
Pyrolysis of plastics in a high vacuum arc image furnace. II
Authors: Friedman Henry L. 
Published: April 2003

AbstractSamples of glass‐ and nylon‐reinforced CTL 91‐LD phenolic and G. E. 124 resin were pyrolyzed in an arc image furnace at high vacuum. Compositions of the various degradation gases are reported. Average molecular weights of these gases were calculated. A description of the mechanism of pyrolysis of G. E. 124 resins is presented. A critique of the method is included.