bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reactivity of cellulose. III. Acid hydrolysis of eucalypt α‐cellulose in the intermediate molecular weight range
Authors: Higgins H. G. , Goldsmith Valerie , McKenzie A. W. 
Published: April 2003

AbstractAn α‐cellulose pulp from Eucalyptus wood was hydrolyzed under homogeneous conditions (mainly 67.5% sulfuric acid at 0 and 20°C.) and under heterogeneous conditions with small weight losses (sulfuric acid solutions of up to 50% concentration for 2 hr. at 50°C. and for periods of up to a week in 21.3% acid at 50°C.). Intrinsic viscosities, [η], of the regenerated samples and the residues, respectively, were determined from measurements in cupriethylenediamine solution. Between weight‐average degrees of polymerization of ca. 310‐70 the apparent rate constants decreased with time of hydrolysis. Comparison of data for homogeneous and heterogeneous conditions confirm the influence of supermolecular factors on the course of hydrolysis of the fiber. Finely ground cellulose is hydrolyzed more rapidly than intact fibers. The concept of a welldefined noncrystalline fiber fraction in which the β‐glucosidie linkages are the only labile bonds and are almost immediately accessible to the hydrolyzing agent is inconsistent with these data. It seems rather that in this material a sharp distinction cannot be drawn between the amorphous and crystalline regions. The observed activation energy for homogeneous hydrolysis, ca. 28 kcal./mole, is in agreement with that determined by other workers under different conditions. The Huggins‐Kraemer equation was followed for heterogeneously hydrolyzed samples, with k′ values of 0.47 for [η] > 2, rising to 0.60‐7 for [ηl] < 1. Regenerated samples gave an average k′ of 0.44 for [η] > 1. Infrared spectra of the hydrolyzed fibers revealed no modification of the cellulose I structure over the whole time series and up to 50% acid in the concentration series. Material regenerated from strong acid solution shows the cellulose II spectrum.
Deuterium isotope effect in inhibited oxidation of butadiene–styrene rubber
Authors: Shelton T. Reid , McDonel E. T. 
Published: April 2003

AbstractThe importance of hydrogen abstraction by peroxy radicals as a mechanism of antioxidant action in rubber has been studied by investigation of a deuterium isotope effect with amine and phenolic inhibitors in the oxidation of butadiene‐styrene rubber. Deuterium was substituted for the active hydrogen of N‐phenyl‐2‐naphthylamine and 2,6‐di‐tert‐butyl‐4‐methylphenol by reacting the antioxidants with methylmagnesium iodide and then with deuterium oxide. The oxidation rates of butadiene–styrene polymer inhibited with 3 parts per hundred of these compounds were measured and compared with the oxidation rates using normal antioxidants. A kinetic isotope effect in the rate of oxidation was observed with both the phenolic inhibitor (kD/kH = 1.3 with not less than 77% substitution) and the amine inhibitor (kD/kH = 1.8 with not less than 60% substitution). The existence of an isotope effect leads to the conclusion that hydrogen donation to a peroxy radical is a controlling step in the mechanism by which these antioxidants function to retard the oxidation of rubber.
Dependence of the ultimate properties of a GR‐S rubber on strain rate and temperature
Authors: Smith Thor L. 
Published: April 2003

AbstractThe tensile properties of an unfilled GR‐S rubber were measured with an Instron tensile tester at strain rates between 0.158 × 10−3 and 0.158 sec.−1 and at fourteen temperatures between −67.8 and 93.3°C. The tensile strength and ultimate strain at the various strain rates and temperatures were superposed to give two composite curves which are functions of a reduced strain rate. From this superposition, the temperature dependence of the ultimate, properties was obtained. The temperature dependence between −53.8 and 71° is essentially the same as obtained by superposing the stress‐strain curves and is given by the Williams, Landel, and Ferry equation. From the composite curves and the temperature function, the tensile strength and the ultimate strain can be predicted at any strain rate and temperature, provided heating and wave propagation effects are negligible. The linear viscoelastic properties were obtained from the initial portions of stress‐strain curves and are represented by a reduced stress‐strain curve.
Specific heat of synthetic high polymers. IX. Poly(ethylene sebacate)
Authors: Wunderlich Bernhard , Dole Malcolm 
Published: April 2003

AbstractAs part of a comprehensive study of the copolymer system poly(ethylene terephthalate‐sebacate), specific heat measurements have been carried out on the annealed polyester, poly(ethylene sebacate), over the temperature range −20 to 140°C. From estimates of densities of completely crystalline and amorphous polymer, the crystallinity at room temperature was calculated to be 57%, and the heat of fusion of completely crystalline polymer to be 30.5 cal. g.−1, a value considerably greater than that calculated by Edgar and Ellery from copolymer data. This discrepancy is attributed to the small crystallite size in their copolymer study. It is shown that the low melting point of the aliphatic polyesters as compared to that of polyethylene is due to the low heat of fusion rather than to a large entropy of fusion as previously supposed. Finally, it is pointed out that in the liquid range, the heat content is closely proportional to volume.
Response of linear high polymers to hydrostatic pressure
Authors: Matsuoka Shiro , Maxwell Bryce 
Published: April 2003

AbstractThe bulk compressibility of linear high polymers has been found to be a function of temperature, pressure, and time. Linear high polymer melts are highly compressible. Addition of pressure causes a structural change in some linear high polymer melts. In the case of amorphous polymers, such as polystyrene, a glassy state response to hydrostatic compression was found at a temperature well above the second‐order transition temperature. In the case of polycrystalline materials, such as polyethylene, pressureinduced crystallization can take place at temperatures above the melting point. In either case, the process requires a higher pressure as temperature is increased. This process is found to be time dependent. There are indications that such structural changes could not take place above a specific temperature limit for any given material, regardless of the amount of pressure. By subjecting a melt of polyethylene to pressure and then cooling, a material that is more dense, more rigid, and more crystalline than the original injection‐molded specimen can be obtained. The effects of the bulk compressibility on the fabrication condition of plastics as well as product properties are discussed.
A new absolute molecular weight method for linear polymers
Authors: Bueche F. , Harding S. W. 
Published: April 2003

AbstractThe measured viscosity for concentrated solutions of linear coiling polymers decreases with increasing rate of shear. By use of a theory previously derived to explain this phenomena, it is possible to determine the absolute molecular weight of the polymer from measurements of this effect. The necessary data required for this determination are readily obtained using a simple cone viscometer. Since the theory requires only a knowledge of the variation of viscosity with shear rate together with the polymer concentration and temperature to compute the molecular weight, the method is easily applied to any polymer of this general type. This shear rate method for determining molecular weights has been checked by measuring M for a large number of samples of polystyrene and polymethyl methacrylate. Satisfactory results are obtained on these polymers. When the method is used as outlined, it gives a value for M which is close to the viscosity average. For very wide molecular weight distributions, the value found is somewhat higher than the weight average. Since the method is only strictly valid for linear polymers, it appears that it may also be used in conjunction with other molecular weight methods to obtain useful information concerning the extent of branching in the molecules.
The denaturation of the proteins of the groundnut (arachis hypogaea) with guanidinium salts, metal salts, and urea
Authors: Williams R. K. , Naismith W. E. F. 
Published: April 2003

AbstractThe denaturation of arachin and conarachin II with urea, guanidinium chloride and thiocyanate, and of arachin with alkali metal thiocyanates and lithium halides has been examined using sedimentation velocity and viscosity techniques. The effect of various anions on the alkaline denaturation of arachin has also been investigated. It was found that with reagents which denature arachin and conarachin II at similar rates, the arachin half molecule was not observed as an intermediate stage in the arachin denaturation with the exception of lithium chloride. The denaturation of arachin with urea and guanidinium chloride was faster at pH 10 than at pH 8. The denaturing power of the alkali metal thiocyanates decreased in the order Li, Na, K, and of lithium halides in the order Lil, LiBr, LiCl. It was found that in the case of denaturation with guanidiniun and alkali metal salts, the cation appeared to be the main denaturant but anions inhibited the denaturation with the exception of the thiocyanate ion which was either noninhibiting or was itself a denaturant. With ionic denaturants in general the nature of both ions was important.
Linear phenol–formaldehyde polymers. Condensation of o‐chlorophenol with formaldehyde
Authors: Burke W. J. , Ruetman S. H. 
Published: April 2003

AbstractThe condensation of o‐chlorophenol with formaldehyde occurred readily at 150°C. in a closed system in the presence of bis(2‐ethoxyethyl) ether as solvent and p‐toluenesulfonic acid as catalyst to form high molecular linear polymers. Use of a high concentration of reactants and a small excess of formaldehyde favored higher molecular weight products. Infrared spectra studies and analytical results on the polymers and their acetyl derivatives indicated that the o‐chlorophenol residues were linked together through ortho and para positions by methylene bridges.
Effect of physical state during the electron irradiation of hydrocarbon polymers. Part I. The influence of physical state on reactions occurring in polyethylene during and following the irradiation
Authors: Lawton Elliott J. , Balwit J. S. , Powell R. S. 
Published: April 2003

AbstractMeasurements of crosslinking, trans‐vinylene formation, and hydrogen evolution have been made on high‐ and low‐density polyethylenes irradiated at temperatures from about −170 to +240°C. Crosslinking produced during irradiation is mainly in the amorphous areas of the polymer; whereas trans‐vinylene unsaturation is produced as readily in the crystalline areas as in the amorphous areas. Radicals are trapped in the crystalline regions. These can react with oxygen to form carbonyl groups, rather than crosslinks. Thus, in Marlex‐50 irradiation in the crystalline state at 25°C. followed by a 7 day storage in air prior to the crosslinking measurements, was only about one‐sixth as effective in producing crosslinks as irradiation in the amorphous state at 150°C. In the low‐density polyethylene where less trapping occurs the factor is about one‐half for the same conditions of irradiation and storage. The lifetime of radicals trapped in Marlex‐50 when stored in oxygen can be thousands of hours compared with a few hours in low density polyethylene. Both the low‐density polyethylene and Marlex‐50 irradiated in the crystalline state at 25°C. (in nitrogen) could be further crosslinked by quickheating them to the amorphous state at 150°C.—delayed carbonyl formation does not occur in this case. Delayed crosslinking resulting from the quick‐heating of irradiated Marlex‐50 gave only about one‐half of the crosslinks for the same irradiation as when irradiated in the amorphous state. Hydrogen evolution as a function of irradiation temperature for Marlex‐50 is discussed; a satisfactory material balance was obtained in which the radiation yield (G value) for total hydrogen produced nearly equaled the sum of G for crosslinking and G for trans‐vinylene formation. Hydrogen yield was found to be nearly constant in the temperature range −170 to +34°C. where crystallinity is also nearly constant, indicating hydrogen production to be nearly independent of temperature. Therefore, the main change in crosslinking yield in the +34 to +150°C. range is considered to be due almost entirely to change in crystallinity. A comparison method for determining relative values of the degree of crosslinking fom the gel measurements is described.
Polymer fractionation. The method of fractionation into summative fractions
Authors: Broda Andrzej , Niwińska Teresa , Połowiński Stefan 
Published: April 2003

AbstractThe correctness of the application of the fraction method into summative fractions for polymer fractionation has been proved. The method of interpretation of the results of fractionation into summative fractions is explained. The basis of this method is the consideration of the function φ(β) which determines the relation between the average degree of polymerization and the weight fraction β of the summative fraction. The whole problem has been limited to the consideration of infinitely small calculated individual fractions. The paper describes the relation between the fractionation results and the selectivity of the polymer separation between the phases of the polymer‐liquid system. A scheme of analysis for systematic errors as well as for determining the exactness of the fractionation method is also given.
Mechanism of vinyl acetate emulsion polymerization
Authors: French David M. 
Published: April 2003

AbstractThe emulsion polymerization of vinyl acetate was investigated with the use of block copolymers of ethylene and propylene oxides (commercially known as Pluronic surfactants) as emulsifying agents. By electron microscopy, the average polymer particle size was determined as a function of conversion of monomer to polymer and as a function of the surfactant concentration. It was found that the number of polymer particles remained constant during the reaction. The polymer surface area per unit volume of completely polymerized emulsion was proportional to the surfactant concentration. In contrast with styrene polymerization, the number of particles varied with the cube of the emulsifier concentration, and the number of particles per unit of surfactant was much less than the number that would have been expected with styrene. It was concluded that the results were consistent with polymerization theory. An expression giving the number of polymer particles produced in the reactions proved to be much simpler than the accepted equation used in the case of water insoluble monomers such as styrene. This simplicity arises from the partial water solubility of vinyl acetate, which enables the monomer to diffuse completely into the polymer particles very early in the reaction. The variation of latex viscosity with polymer particle size was also investigated. At constant solids concentration, the logarithm of the viscosity was proportional to the polymer surface area per unit of latex.
Effect of complexing agents on the persulfate‐bisulfite catalysis of acrylonitrile polymerization
Authors: Campbell Charles H. 
Published: April 2003

AbstractThe effect of a number of iron complexing agents on the persulfate‐bisulfite catalysis of acrylonitrile polymerization was studied. Several complexing agents were found to be effective in retarding suspension polymerization of acrylonitrile with this redox system. A relationship was found betweeen the redox potential of the iron complex and polymerization rate. Evidence was shown that the persulfate‐bisulfite polymerization of acrylonitrile requires the presence of iron or other metal ions.
Dynamic mechanical properties of polyethylene terephthalate
Authors: Kawaguchi T. 
Published: April 2003

AbstractDynamic mechanical properties of polyethylene terephthalate have been measured as function of temperature at −70 to +310°C. at 100–200 cycles/sec. by a cantilever vibration method. Two mechanical loss maxima have been distinguished, and effects associated with variations in the degree of crystallinity and orientation and in the water content of the material have been investigated. The main softening region is shown to be influenced by the variations in the degree of crystallinity. Another process, which occurs at low temperature, is affected by changes in the water content of the material. The height of the loss maximum is increased when water is absorbed, although the temperature at which maximum loss occurs remains unchanged. Finally, the low temperature process is compared for members of a series of polyesters. Increasing the distance between the cyclic groups brings about a slight reduction in the temperature of this loss maximum. Interchange of the positions of the magnified image and O groups depresses the loss maximum temperature.
The stiffness modulus of polyethylene as a function of temperature and structure
Authors: Reding F. P. 
Published: April 2003

AbstractThe stiffness moduli of polyethylenes covering a wide range of degrees of branching and molecular weights have been investigated from −150°C. up to the melting points. Qualitatively, the stiffness temperature curves can be broken into three regions. The first of these is the very low temperature region which extends from −150 up to about −50°C. In this temperature region, all of the polymers have the same stiffness at a given temperature, although they do not have the same density. The second region extends from about −50° up to the melting region. In this region, it is generally true that the stiffness is a function of the density alone. This is the case even though the temperatures at which polymers have equal densities are different. There are exceptions, however. It has been found that extremely high molecular weight polymers have higher stiffness than would be expected from their densities. Presumably, this arises directly from the very high molecular weight. It has further been found that highly crystalline polyethylenes increase in density upon annealing, but show little increase in stiffness or degree of crystallinity as measured by x‐rays. This may well arise from the removal of small voids or flaws on i Annealing, the removal of which would increase density but not affect stiffness or crystallinity. The third region of the stiffness‐temperature curves is the melting region. As expected, the stiffness curves reflect the higher melting points of the more linear resins. The stiffness curves also qualitatively indicate the randomness of branching. Polymers which are nonrandomly branched suffer a more gradual decrease of stiffness with temperature, reflecting a broader melting range than the more randomlybranched polymers. This effect probably arises from a broader distribution of crystallite sizes in the nonrandomly branched polymers. Unlike any other crystalline polymer which has been examined, the stiffness‐temperature curves for polyethylene do not exhibit evidence of a sharp glass transition temperature. Rather, polethylene appears to undergo a gradual “thawing” from about −50°C. up to within a few degrees of the melting point.
The rupture process in carbon‐loaded rubbers: An electron‐microscopic investigation
Authors: Andrews E. H. , Walsh A. 
Published: April 2003

AbstractA study has been made of the disposition of carbon‐black particles in the tear and fracture surfaces of various filled rubbers by replica electron microscopy. The surfaces are characterized by two parameters, viz., the proportion of the surface area occupied by filler, and the proportion occupied by particles extracted from the rubber by the gelatine first‐stage replica. Values obtained for the former quantity indicate that the rupture path departs strongly from a random plane through the material. The second quantity is a measure of filler‐to‐rubber adhesion, which is found to depend upon the nature of the filler‐rubber interface and is related to the energy required to produce rupture. Simple physical mechanisms are proposed to explain the observed influence of filler upon rupture propagation.
A comparative molecular weight study with particular reference to black wattle tannins
Authors: Evelyn S. R. , Cooper D. R. , Van Berge P. C. 
Published: April 2003

AbstractDetails are given of a further modification to the Ray ebulliometer which permits easy interchange of the Cottrell pump tube. The stability of the apparatus with different pump tubes and pumping conditions was also examined. Molecular weights obtained with the use of two ebulliometers and three solvent systems are compared. The validity of the recently developed ultracentrifuge methods for determining physical properties of molecules with molecular weights in the range 300 to 10,000 was checked by using a pure compound of known molecular weight. Agreement was obtained also between the data obtained by the Klainer and Kegeles method and separate sedimentation and diffusion data. The molecular weight of an ethyl acetate extract of black wattle tannin was determined by the ebulliometric and these ultracentrifuge methods. The ultracentrifuge value for the whole extract decreased with time due to sedimentation of high molecular weight impurities. The final ultracentrifuge weight‐average molecular weight (1175) is in good agreement with the number‐average value for the tannin polyphenols (922) obtained by ebulliometry. The difference between the values confirms the known heterogeneity of the polyphenols.
An excluded volume effect in light scattering
Authors: Hyde A. J. , Ryan J. H. , Wall F. T. , Schatzki T. F. 
Published: April 2003

AbstractAn expression for the intensity of light scattered by an isolated linear polymer chain with excluded volume has been evaluated for conditions corresponding to those met in experiment. The expression proves to be an excellent approximation to light scattering results for a very high molecular weight polystyrene fraction, thus providing an explanation for what appeared to be an anomalously large polydispersity when the data were treated according to the usual random flight model. Coil sizes were calculated and compared with the values obtained from the data by other methods.
Ionic grafting
Authors: Kockelbergh G. , Smets G. 
Published: April 2003

AbstractCationic polymerization of isobutene has been carried out in carbon disulfide solution in the presence of AlBr3 and chloromethylpolystyrene at −60°C. in order to obtain graft copolymers. The separation of the graft copolymers from the reaction mixtures in benzene solution was based on a standardized precipitation technique involving use successively of butanone and methanol as precipitating agents. By this method, fractions with an intermediate solubility have been isolated and purified twice. The differences of solubility of their products are discussed. Their isobutene content and intrinsic viscosities have been determined. The degree of grafting of these products is usually low (5–18%).
Inhibition in the polymerization of N‐carboxyglycine anhydride
Authors: Moos Gilbert E. , Budelman Hilda , Chen Pai‐Fun 
Published: April 2003

AbstractThe conversion of N‐carboxyglycine anhydride in dioxane to polyglycine has been completely inhibited with as little as 0.2 mole‐%, based on monomer, of acetyl chloride, thionyl chloride, 2,2′‐dichloro‐N‐methyldiethylamine hydrochloride, and AlCl3. Phenyl isocyanate and acetic anhydride also show strong inhibition. Myleran, and especially its 1,9‐relative, 1,9‐dimethylsulfonyloxynonane, show similar action at slightly higher concentrations. The most active inhibitors have in common a strong tendency to react with initiators such as water, alcohols, or amines.