bluuebunny/crossref_metadata_2025_split huggingface dataset:
High speed compression properties of textile structures and sheet‐like materials
Authors: Victory E. L. 
Published: April 2003

AbstractHigh speed compression properties of textile structures and sheetlike materials that pass through a set of press rolls are found to be the controlling factor in determining the pressure schedule within the nip region, the loading of the rolls, and the minimum separation of the roll surfaces (nip thickness) of the press. Factors affecting the high speed compression properties of felts (napped textile structures) which are used to carry a wet sheet of paper through the press section of a paper machine are examined. The compressive stress‐strain curves of a single felt design are obtained using the Plastechon High Speed Tester to simulate the strain schedule within the nip region of the press section of the paper machine. Compression curves of new, used and worn felts are obtained at deformation rates from 20 in./sec. to 100 in./sec., equivalent to paper machine speeds ranging from 1000 ft./min. to 5000 ft./min. and at various levels of water content (dry, wet and saturated). The results show that the felt offers more resistance to compression as the strain rate and/or its water content is increased. Similarly, worn felts are found to require more force to achieve a given level of compression than new, napped felts. These compression curves are used to verify a general theory for determining the load versus nip strain relationship of the press section. The results of the experiments conducted on an experimental press section tend to confirm the theory and have thus pointed to the extreme importance of the high speed compression characteristics of the material in the nip region in determining the dynamics of a press.
A new class of block polymers
Authors: Tobolsky A. V. , Rembaum A. 
Published: April 2003

AbstractThe reaction of industrially available “prepolymers,” containing one or several isocyanate groups per chain, with tert‐butyl hydroperoxide yielded long‐chain peroxycarbamates. These were found able to initiate the polymerization of a wide variety of vinyl monomers as well as dienes leading to a new class of block polymers of very interesting physical properties. Polyether and polyester “prepolymers” with one, two, or three isocyanate functionalities were linked chemically to polystyrene, polymethyl methacrylate, poly‐n‐butyl acrylate, polyarylonitrile, and polyisoprene. The formation of block polymers was proved by both physical and chemical methods. Their mechanical properties were illustrated by means of torsional modulus–temperature curves. The effect of varying composition and of a crosslinking agent on the elastic modulus was examined. Tentative reaction mechanisms were also presented.
Cleavage of disulfide polymers. III. By disulfides
Authors: Fettes E. M. , Mark H. 
Published: April 2003

AbstractA study was made of the cleavage of polymeric disulfide by organic disulfides of different structures in the presence and absence of sodium disulfide. While aliphatic disulfides will cleave polymeric disulfides only in the presence of sodium disulfide, hydroxyethyl disulfide and aromatic disulfides will cause partial cleavage in the absence of inorganic disulfide. It is believed that cleavage results not from a disulfide–disulfide interchange, but from cleavage of the organic disulfide by water to form a RS− anion. Other salts known to cleave disulfide groups promote the cleavage of polymer by butyl disulfide, sodium sulfoxylateformaldehyde being particularly active. Benzothiazyl disulfide and tetraalkylthiuram disulfides reacted to cleave in the absence of sodium disulfide but had no effect when sodium disulfide was present. By carrying out the reaction stepwise, it was found that sodium disulfide reversed the softening action of the disulfide reforming the cleaved linkages. When the disulfide polymer contained terminal thiol groups, tetramethylthiuram disulfide would reform the high polymer by converting thiol terminals to disulfide links. In spite of the known ability of these complex disulfides to dissociate homolytically into radicals and initiate vinyl polymerization, no evidence was found that the cleavage of polymeric disulfides involved RS·radicals.
Transport of liquids in structurally modified polyethylene
Authors: Baddour Raymond F. , Michaels Alan S. , Bixler Harris J. , De Filippi Richard P. , Barrie James A. 
Published: April 2003

AbstractCast linear polyethylene films subjected to dry and solvent annealing display markedly different sorption and difusion barrier properties than do untreated films. The subsequent sorption of liquid o‐ and p‐xylene and cis‐ and trans‐acetylene dichloride per unit volume of amorphous polymer increases as the annealing temperature and/or treating solvent concentration increases. Integral diffusivities calculated from sorption and steady‐state permeation rates show a monotonic increase with sorption per unit volume of amorphous polymer. The concentration dependence, however, is less marked than observed in similar systems at low permeant activity. Apparently the above treatment reduces the effective crosslinking imposed by the crystallites on the amorphous polymer chains through disentangling and incorporating some of these chains into crystallites. Thus the polymer is capable of a greater degree of swelling when brought into contact with a compatible liquid in a spite of a higher degree of crystallinity. The low concentration dependence of the diffusivities is probably due to heterogeneous distribution of excess permeant in a treated film. If the excess permeant were preferentially sorbed in regions of low polymer concentration then the above observations could be explained. Long‐duration, osmotic stress‐induced swelling and recrystallization have been cited to account for time‐dependent permeation rates in treated and untreated films.
Temperature dependence of tensile properties of polycarbonate films
Authors: Ekvall R. A. , Low J. R. 
Published: April 2003

AbstractThe tensile properties of bisphenol A polycarbonate films were measured as a function of temperature from +25 to −180°C. The tensile properties at a given temperature were determined from the measured true stress‐true strain behavior of the polycarbonate films by means of a photographic strain recording technique. The temperature dependence of the following tensile properties is presented: the yield stress, the fracture stress, the strain to yield, the cold‐drawing strain, the fracture strain, and the strain‐hardening rate.
Sorption of organic vapors by wool keratin
Authors: Watt I. C. 
Published: April 2003

AbstractThe absorption and desorption behavior of organic vapors and wool keratin has been investigated. At low relative vapor pressures sorption is Fickian and the rate of diffusion is determined by the size and configuration of the sorbate molecule. For absorption to saturation vapor pressure a second absorption mechanism is involved, depending on the ease with which the sorbate can disrupt the keratin network structure. This mechanism is superimposed on the Fickian mechanism, and the uptake shows non‐Fickian anomalies. On desorption there is an initial rapid removal of sorbate before the rate of removal becomes extremely slow. The amount of retained sorbate in the region of slow removal is dependent on the temperature, the size, and the configuration of the sorbate molecules and has been qualitatively related to the measured diffusion coefficients at low relative vapor pressures.
Factors affecting the heptane solubility of polypropylene polymers and yarns
Authors: Ross S. E. , Wolf H. W. 
Published: April 2003

AbstractThe heptane solubility of polypropylene yarns prepared under a variety of experimental conditions from several molecular weight ranges of polymers has been examined. The heptane solubilities of the yarns have been found to vary over a wide range, depending upon the conditions of extrusion during fiber formation and the subsequent degree of orientation of the fibers. The solubility of the yarns increases with higher spinning temperatures presumably as a function of the formation of low molecular weight soluble fractions formed as a result of thermal degradation. A reduction in the solubility occurs as the yarns are oriented either during the winding operation or by subsequent drawing. The reduced solubility has been explained on the basis of increased molecular alignment thereby promoting increased crystallinity as well as the possible entrapment of normally soluble atactic polymer. The fact that the polymer solubility can be decreased by bringing the polymer to a higher state of crystallinity has been shown by annealing studies. The solubilities of the original polymers, therefore, exhibit little correlation with the yarns produced from them. The solubilities of the annealed polymers, however, more closely approach the values obtained for the highly oriented yarns.
Effect of morphology on biaxial stress rupture of polyethylene
Authors: Cooney J. L. 
Published: April 2003

AbstractThe relationship between biaxial stress‐rupture behavior and polymer morphology has been investigated for a series of compression‐molded disks of linear polyethylene. Rupture data were obtained over a range of temperatures on polymers of several melt indices that had been solidified at two rates. Two failure mechanisms were observed: one at high stress levels, which was ductile; the other at low stress levels, which was brittle. The stress level at which the mechanism changed from ductile to brittle decreased as the measurement temperature increased, as the melt index of the polymer increased, and as the rate or solidification decreased. It was shown that initial pressurization of the disks causes the formation of microscopic surface fissures along spherulite boundaries as well as within individual spherulites. The extensive growth of these fissures at high stress levels sufficiently raises the stress on the sound portions of the polymer to cause large‐scale macroscopic drawing of the spherulites. At low stress levels the initially formed fissures grow by a localized drawing process at their ends. A macroscopic crack forms by a chance coalescence of a number of individually growing fissures. This process is more rapid in disks of polymer that form large spherulites when cooled slowly from the melt. The spherulite size in disks of polymer of low melt index is much smaller under the same conditions of cooling and is less sensitive to the cooling rate than in disks of polymer of high melt index. Annealing of rapidly cooled disks whose microstructure contains relatively small spherulites reduces the stress at which the failure mechanism changes without appreciably altering the spherulite size. Oxidation of the polymer also reduces the transition stress.
Mechanism of ultraviolet stabilization of polymers by aromatic salicylates
Authors: Newland G. C. , Tamblyn J. W. 
Published: April 2003

AbstractMany derivatives of phenyl salicylate turn yellow when they are exposed, in solution, to ultraviolet light. This limits their usefulness as ultraviolet stabilizers for plastics. Evidence is presented to support the postulation that the yellowing is due to the formation, by a photochemical ortho rearrangement, of a derivative of 2,2′‐dihydroxybenzo‐phenone. Aromatic salicylates, such as 2,6‐dialkylphenyl salicylate, in which the ortho rearrangement is blocked, are found to be nonyellowing stabilizers, although less effective than the better yellowing varieties, such as p‐octylphenyl salicylate. Loss of stabilizer by volatilization, either in compounding or during subsequent exposure, is shown to be an important factor in limiting the effective performance of the stabilizer.
Mechanism of ozone cracking. II. Nucleation and growth of cracks in a plastic film
Authors: Salomon G. , Van Bloois F. 
Published: April 2003

AbstractPartly unsaturated natural rubber hydrochloride films undergo stress cracking in ozonized oxygen. The origin of cracks and the correlation between stress distribution and rate of crack growth have now been studied. Cracks are initiated at foreign particles and/or surface fissures of microscopic dimensions. Fracture is promoted only if the shape of the incipient crack fulfils certain geometric conditions. These films become highly birefringent when stretched beyond the elastic limit; specific birefringence increases linearly with strain. It follows from stress optical studies that large plastic deformations take place ahead of the crack, whereas the film is deformed only elastically. Cut growth experiments confirm these conclusions. Fractography reveals that cracking consists mostly of a series of discontinuous events on a microscopic scale. The influence of crack length and polymer modulus on the critical stress, necessary for the onset of ozone cracking, is predictable from the Griffith criterion. The maximum stress at the tip was calculated from the observed dimensions of the crack and found to surpass the yield stress of the polymer. Mechanical brittle fracturing and ozone‐induced stress corrosion have been compared. The remaining empirical element, which determines the rate of cracking, is the rate of hardening on ozonization of the fresh surface.
Acid–base properties of fibers. Part II. A polyelectrolyte theory of the combination of fibers with acids and bases
Authors: Mathieson A. R. , Whewell C. S. 
Published: April 2003

AbstractA. new theory for the acid–base properties of fibers is presented, resembling those for polyelectrolytes, and based on the normal titration of the charged groups of the fibers and the energy needed to remove the protons from the fiber to the solution, against the electrostatic, osmotic, and affinity differences. The acid titration equation for a poly‐ampholyte fiber is:

where pK0′ is the intrinsic dissociation constant of the titration groups in the fiber, α is the degree of dissociation, χ is the electrostatic potential of the fiber, τ the osmotic pressure, V̄H the partial molar volume of the hydrogen ion, and Δμ the difference of standard chemical potential in the fiber and the solution. In all cases examined, the osmotic term proved to be negligible. The electrostatic potential was calculated as suming it to be uniform over the fiber. For wool, pK0′ is independent of salt concentration but varies linearly with degree of dissociation, indicating that two pK's are operating, pKq = 3.585 for paired groups and pKp = 4.855 for nonpaired groups at 0°C., present in equal proportions. Titrations of wool with sulfuric acid and a wide range of strong monobasic acids also obey the theory, and values of the anion affinities in general agreement with those given by Gilbert and Rideal are found. The acid titration of native ox‐hide collagen gave a constant value of pK0′ = 4.0. For nylon, the value of pK0′ is, to a first approximation, independent of degree of dissociation and salt concentration, in agreement with the theory.
Synergism of free radical initiators with self‐extinguishing additives in vinyl aromatic polymers
Authors: Eichhorn J. 
Published: April 2003

AbstractVinyl aromatic polymers such as polystyrene can be made nonflammable by the addition of halogen compounds. The amount of halogen required to make such polymers nonflammable can now be greatly reduced by the addition of small amounts of certain free radical initiators. Normally about 5 phr of acetylene tetrabromide (parts of additive per hundred parts of polymer) must be added to polystyrene to obtain a self‐extinguishing polymer. Only 0.5 phr of acetylene tetrabromide is required if 0.5 phr dicumyl peroxide is added. This synergistic effect has been observed with a series of peroxides, hydroperoxides, azo compounds, quinone imines, benzothiazole sulfenamides, disulfides, and a bibenzyl compound. The synergistic mechanism seems to be based on a series of reactions involving attack of the polymer by the initiator and subsequent reaction between polymer fragments and the halogen compound. The result is a delay in the loss of halogen from the polymer mass and thus a more efficient use of the halogen additive for flame quenching. Known inhibitors of free radical reactions have a detrimental effect on the synergistic mechanism.
Preparation and chelating properties of 8‐hydroxy‐quinoline—formaldehyde polymers
Authors: Degeiso R. C. , Donaruma L. G. , Tomic E. A. 
Published: April 2003

AbstractCondensation of 8‐hydroxyquinoline with formaldehyde in acid solution yielded a polymer of molecular weight ∽3300. Modification of this polymer with resorcinol resulted in improved physical properties of this material. 8‐Hydroxyquinoline‐formaldehyde polymers can be used as selective chelating ion‐exchange rains which permit separation of various cations. The polymeric metd chelates are thermally less stable than the unchelated polymer.
Fracture surface work measurements on glassy polymers by a cleavage technique. II. Effects of crosslinking and preorientation
Authors: Broutman L. J. , McGarry F. J. 
Published: April 2003

AbstractIt has recently been postulated that viscous flow, or plastic deformation, occurs near the tip of an advancing crack in glassy amorphous polymers such as Plexiglas, and this results in molecular orientation at the fracture surface. The evidence for this has been the appearance of colors on fresh fracture surfaces of Plexiglas and the extremely high measured surface work which is 1000 times greater than the theoretical surface energy. The effect of crosslinking has been studied by measuring the surface work of crosslinked forms of Plexiglas and highly crosslinked thermosetting polymers. The surface work decreases as the degree of crosslinking in Plexiglas increases. Colors are absent on the fracture surface of the highly crosslinked Plexiglas, and the surface is mirror‐smooth. The effect of crosslinking is to inhibit viscous flow or plastic deformation at the tip of the crack. The surface work of polyester and epoxy resins have been measured and found to be a factor of 10 smaller than the linear polymers, but still remain much higher than the theoretical estimates. Preorienting Plexiglas or polystyrene reduces the surface work of a crack propagating parallel to the orientation and increases the surface work of a crack normal to the orientation. The colors on the fracture surfaces of preoriented Plexiglas samples either disappear or change to colors of shorter wavelengths if the crack is propagated parallel to the orientation. This is a good indication that orientation occurs at the tip of a crack and is responsible for the appearance of colors on Plexiglas fracture surfaces. The surface work of 150% hotstretched polystyrene is 7000 erg/cm.2, and the fracture surface is mirror‐smooth. This surface work is greater by only a factor of 10 than the theoretical estimate and suggests that only a small amount of molecular motion has taken place.
Structural effects in metal ion catalysis of isocyanate–hydroxyl reactions
Authors: Robins Janis 
Published: April 2003

AbstractMetal ion catalysis of isocyanate–hydroxyl reactions is considerably enhanced by the presence of certain “activating” groups α, β, even γ to the carbon carrying the reactive hydroxyl. Few metal ions can significantly catalyze the isocyanate–butanol reaction. In general the metal ion catalysts fall into two groups: catalysts which maintain a fair portion of their activity, even in systems containing hindered isocyanates, and catalysts which are very sensitive to changes in steric factors. It is believed that metal ions fulfill a two fold function: they increase the electrophilic character of the isocyanate group by coordinating either at the oxygen or nitrogen, and they bring the isocyanate and alcohol in closer proximity. The “activating” groups are believed to have two major opposing effects: to increase the overall stability of the ternary complex while allowing the hydroxyl group to retain most of its nucleophilicity and to produce in some cases urethanes which preferentially chelate the metal ion and kill the catalysis. All metal ions exhibit greater catalytic activity in systems containing 1,2‐ than 1,4‐glycols; furthermore the sensitivity to steric hindrance increases from 1,2‐ to 1,4‐glycols, indicating that only chelation can sufficiently increase the stability of the ternary complex to produce the maximum catalytic effect.
Ultraviolet stabilizing monomers and polymers. I. Synthesis and polymerization of phenyl 5‐methacryloxymethylsalicylate
Authors: Fertig J. , Goldberg A. I. , Skoultchi M. 
Published: April 2003

AbstractWith a view to permanently incorporating ultraviolet stabilizing moieties into polymer systems, monomers containing the phenyl salicylate structure have been prepared and polymerized. Phenyl 5‐acryloxymethylsalicylate and phenyl 5‐methacryloxymethyl‐salicylate were prepared by the chloromethylation of phenyl salicylate and subsequent reaction with sodium acrylate or methacrylate. Homopolymers and copolymers of the methacryloxymethyl monomer were prepared and studied. The ultraviolet spectra of the chloromethyl derivative, the monomers, and the homopolymers were essentially similar to that of the starting material, phenyl salicylate. Copolymers of the ultraviolet‐absorbing monomers (2%) with vinyl acetate, vinylidene chloride, and vinyl chloride were prepared. The ultraviolet stability of these copolymers was then compared to that of an unstabilized control series and a series containing phenyl salicylate. While there were some differences in the behavior of the copolymerized absorber it was at least as effective as phenyl salicylate in stabilizing the polymers.
Oxidative degradation of phenol–formaldehyde polycondensation initial degradation reactions
Authors: Conley Robert T. 
Published: April 2003

AbstractThe initial degradation of phenol–formaldehyde polycondensates has been found to follow two distinct pathways. Oxidation of the dihydroxydiphenylmethane unit to substituted dihydroxybenzophenone and dihydroxybenzhydrol species has been observed and substantiated using model compounds to support the characteristic infrared spectral changes. The ingrowth of ketonic species has been evaluated kinetically on phenol–formaldehyde polymers which have been cured fully to remove residual methylol groups. The rate constants have been found to be a factor of 33 times slower than those observed earlier for partially cured resins having relatively large numbers of residual methylol groups present. The activation energy for the initial ketonic carbonyl was found to be 15.6 ± 3.9 kcal. This value compares favorably with other values obtained for phenolic oxidation. The potential oxidation of methylol groups to substituted salicylic acid moieties could not be substantiated spectrally. However, a polymer containing 2‐methylol‐p‐cresol on oxidation gave a small quantity of 5‐methylsalicylic acid, thus substantiating methylol oxidation in competition with the further curing reaction which produces new diphenylmethane linkages. The secondary oxidation resulting in chain scission can be separated on a time scale from oxidations of the methylol type. The present study therefore significantly extends the initial oxidative degradation chemistry of phenol–formaldehyde polycondensates.