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  • Chemistry  (3,899)
  • Cosmology  (1,607)
  • 2015-2019  (1,847)
  • 1945-1949  (3,659)
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  • 1
    Publication Date: 2021-05-19
    Description: 0Genetic polymorphism by means of biochemical genetic markers using polyacrylamide gel electrophoresis system in four barbus fish species has been investigated. Species scientific name were Barbus sharpeyi ; Gunther, 1847 , Barbus grypus ; Heckel, 1843, Barbus xanthopterus ; Heckel, 1843 and Barbus esocinus ; Heckel, 1843.Sampling site and location were mainly in the rivers located in Khoozestan province such as Karoon and Karkheh rivers and the Dez dam. Different organs such as blood, muscle, kidney, eye and heart were sampled and analysed for the presence of tf, es, sod and pgm alleles. High polymorphism and presence of different alleles scored, but populations were not in the H-W equilibrium. Considring results, using current and avaiable genetic markers such as microsattelits is recommended for future works.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: Chemistry ; Genetics ; Genetics Markers ; Distinguish ; Barbus ; Species ; Barbus sharpeyi ; Barbus xanthopterus ; Barbus esocinus
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 62pp.
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  • 2
    Publication Date: 2021-05-19
    Description: Cheshmehkileh River and adjacent mountainous streams, play a strategic role as a historical axis for anthropogenic civilization, human welfare also habitat and migration pathway of commercial – biologic valuable fishes e.g. Caspian trout, Caspian kuttum, members of Cyprinidae family in south Caspian Sea drainage. Treats such as overfishing of Caspian trout and Red spotted trout stocks in mountainous headwaters, barriers construction and manipulations those are out of river carrying capacity developed by human activities, affected normal function of river as well. Sand mining big factories establishment next to the river, legal and illegal trade of river sediments, direct entry of Tonekabon landfill leakage into the river, development of Rainbow trout farms since 3 decades and huge effluents into the river containing dead fish and types of solids, escapement of cultured Rainbow trouts into the river, … are major minimum factors which needs basic information for integrating inclusively drainage management system. Cheshmehkileh River contains Headwaters of Dohezar (Daryasar & Nusha), Sehezar and Valamroud rivers during 13 monthly sampling phases between September 2009 and October 2010 based on macrozoobenthoses investigations by EPT, EPT/C EPA protocols, measurements of nominated physic-chemical and microbiologic parameters. Probability of Rainbow trouts escapement and invasion, existence, nutrition in Cheshmehkileh environment indeed investigated. Data analysis explained significant differences (P〈0.05) between groups of measured parameters in different sampling stations. Dendogram of clustered analysis based on consolidation of major biologic/ physic-chemical and microbiologic parameters, separated stations No. 1, 3, 2, 4 in one group and remained classified in different groups. Station 8 and 9 similarly separated which expressed general similarities according to Sehezar river environment which were differs in comparison with other stations. Station 11 separated according to its natural quality of water and environment. Similarities between station 10 to Sehezar river stations 8 and 9 expressed general influence of Sehezar River more than Dohezar River in Cheshmehkileh condition especially in station No. 10. High scores of EPT and EPT/C indices in upstream stations 1, 3 and 8 also low score of indices in stations 7, 13 and 6 expressed levels of environment quality between these groups of stations. Maximum average biomass of macroinvertebrates belongs to Trichoptera order in Cheshmehkileh River. Significant decrease of biomass in stations 11, 12 and 13 in comparison with other stations stated environment degradation in mentioned stations relevant to excessive sand mining as well. Pollution resistant groups of invertebrates significantly increased in downstreams against upstream stations. Also disappearing of Plecoptera order in station No. 7, 9, 10 and 13 stated low quality of environment in comparison with upstream stations. Confirmation of effects quality and quantity for point and non-point sources of imported pollutants require specific management considerations in order to present exploitations, pollutants control and emergencies for river monitoring in forthcoming years.
    Description: Iranian Fisheries Science Research Institute
    Description: Published
    Keywords: River ; Pollution ; Aquaculture ; EPTC ; Assessment ; Macroinvertebrates ; Chemistry ; Microbiology
    Repository Name: AquaDocs
    Type: Report , Refereed
    Format: 138pp.
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  • 3
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    Station Océanographique de Salammbô | Paris, France
    Publication Date: 2021-05-19
    Description: La détermination de la chloruration des eaux de mer est effectuée depuis de nombreuses années par la méthode volémetrisque de Moher.
    Description: Published
    Keywords: Volumetric analysis ; Sea water ; Chemistry ; Density ; Water density ; Chlorination ; Methodology ; Marine
    Repository Name: AquaDocs
    Type: Book/Monograph/Conference Proceedings , Refereed
    Format: 28pp.
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  • 4
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-05-25
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2018
    Description: Many chemical constituents are removed from the ocean by attachment to settling particles, a process referred to as “scavenging.” Radioisotopes of thorium, a highly particle-reactive element, have been used extensively to study scavenging in the ocean. However, this process is complicated by the highly variable chemical composition and concentration of particles in oceanic waters. This thesis focuses on understanding the cycling of thorium as affected by particle concentration and particle composition in the North Atlantic. This objective is addressed using (i) the distributions 228,230,234Th, their radioactive parents, particle composition, and bulk particle concentration, as measured or estimated along the GEOTRACES North Atlantic Transect (GA03) and (ii) a model for the reversible exchange of thorium with particles. Model parameters are either estimated by inversion (chapter 2-4), or prescribed in order to simulate 230Th in a circulation model (chapter 5). The major findings of this thesis follow. In chapters 2 and 3, I find that the rate parameters of the reversible exchange model show systematic variations along GA03. In particular, 𝑘1, the apparent first-order rate "constant" of Th adsorption onto particles, generally presents maxima in the mesopelagic zone and minima below. A positive correlation between 𝑘1 and bulk particle concentration is found, consistent with the notion that the specific rate at which a metal in solution attaches to particles increases with the number of surface sites available for adsorption. In chapter 4, I show that Mn (oxyhydr)oxides and biogenic particles most strongly influence 𝑘1 west of the Mauritanian upwelling, but that biogenic particles dominate 𝑘1 in this region. In chapter 5, I find that dissolved 230Th data are best represented by a model that assumes enhanced values of 𝑘1 near the seafloor. Collectively, my findings suggest that spatial variations in Th radioisotope activities observed in the North Atlantic reflect at least partly variations in the rate at which Th is removed from the water column.
    Description: This work was supported by the US National Science Foundation. Two US NSF grants have supported the research in this thesis (OCE-1232578 and OCE-155644).
    Keywords: Thorium ; Chemistry
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 5
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-05-25
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2017
    Description: This thesis documents the origin, distribution, and fate of methane and several of its isotopic forms on Earth. Using observational, experimental, and theoretical approaches, I illustrate how the relative abundances of 12CH4, 13CH4, 12CH3D, and 13CH3D record the formation, transport, and breakdown of methane in selected settings. Chapter 2 reports precise determinations of 13CH3D, a “clumped” isotopologue of methane, in samples collected from various settings representing many of the major sources and reservoirs of methane on Earth. The results show that the information encoded by the abundance of 13CH3D enables differentiation of methane generated by microbial, thermogenic, and abiogenic processes. A strong correlation between clumped- and hydrogen-isotope signatures in microbial methane is identified and quantitatively linked to the availability of H2 and the reversibility of microbially-mediated methanogenesis in the environment. Determination of 13CH3D in combination with hydrogen-isotope ratios of methane and water provides a sensitive indicator of the extent of C–H bond equilibration, enables fingerprinting of methane-generating mechanisms, and in some cases, supplies direct constraints for locating the waters from which migrated gases were sourced. Chapter 3 applies this concept to constrain the origin of methane in hydrothermal fluids from sediment-poor vent fields hosted in mafic and ultramafic rocks on slow- and ultraslow-spreading mid-ocean ridges. The data support a hypogene model whereby methane forms abiotically within plutonic rocks of the oceanic crust at temperatures above ca. 300 C during respeciation of magmatic volatiles, and is subsequently extracted during active, convective hydrothermal circulation. Chapter 4 presents the results of culture experiments in which methane is oxidized in the presence of O2 by the bacterium Methylococcus capsulatus strain Bath. The results show that the clumped isotopologue abundances of partially-oxidized methane can be predicted from knowledge of 13C/12C and D/H isotope fractionation factors alone.
    Description: The research activities documented in this thesis were made possible by grants to my advisor from the U.S. National Science Foundation (NSF award EAR-1250394), the National Aeronautics and Space Administration (NASA) Astrobiology Institute (NAI, University of Colorado, Boulder, CAN 7 under Cooperative Agreement NNA15BB02A), the Department of Energy (DOE, Small Business Innovation Research program, contract DE-SC0004575), the Alfred P. Sloan Foundation via the Deep Carbon Observatory, and a Shell Graduate Fellowship through the MIT Energy Initiative. I completed the bulk of the work in this thesis while being supported by a National Defense Science and Engineering Graduate (NDSEG) Fellowship awarded through the Office of Naval Research of the U.S. Department of Defense. The StanleyW.Watson Fellowship Fund provided support during my first summer term at WHOI.The Charles M. Vest Presidential Fellowship at MIT supported me in the first year of my Ph.D. studies. I received additional support that year through NSF award EAR-1159318 (to S. Ono and T. Bosak) and theWalter & Adel Hohenstein Graduate Fellowship of Phi Kappa Phi. The MIT Earth Resources Laboratory and PAOC Houghton Fund funded my attendance at several conferences.
    Keywords: Methane ; Chemistry ; Isotopes ; Oxidation
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 6
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-05-26
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2017
    Description: Salt marshes are physically, chemically, and biologically dynamic environments found globally at temperate latitudes. Tidal creeks and marshtop ponds may expand at the expense of productive grass-covered marsh platform. It is therefore important to understand the present magnitude and drivers of production and respiration in these submerged environments in order to evaluate the future role of salt marshes as a carbon sink. This thesis describes new methods to apply the triple oxygen isotope tracer of photosynthetic production in a salt marsh. Additionally, noble gases are applied to constrain air-water exchange processes which affect metabolism tracers. These stable, natural abundance tracers complement traditional techniques for measuring metabolism. In particular, they highlight the potential importance of daytime oxygen sinks besides aerobic respiration, such as rising bubbles. In tidal creeks, increasing nutrients may increase both production and respiration, without any apparent change in the net metabolism. In ponds, daytime production and respiration are also tightly coupled, but there is high background respiration regardless of changes in daytime production. Both tidal creeks and ponds have higher respiration rates and lower production rates than the marsh platform, suggesting that expansion of these submerged environments could limit the ability of salt marshes to sequester carbon.
    Description: Financial support for my doctoral research was provided by the United States Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program, the National Science Foundation under grant OCE-1233678, and the Woods Hole Oceanographic Institution (WHOI) under grants from the WHOI Coastal Ocean Institute, Ocean and Climate Change Institute, and Ocean Life Institute. WHOI Academic Programs Office also provided funding support for research, through the Ocean Ventures Fund, and for my stipend, as graduate research assistantships including an assistantship from the United States Geological Survey administered by WHOI.
    Keywords: Marshes ; Chemistry ; Metabolism ; Knorr (Ship : 1970-) Cruise KN210-04
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 7
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diethyl silicon dichloride was prepared by a Grignard synthesis and purified highly. The material in various stages of purification was hydrolyzed and then polymerized. The properties of the hydrolyzate and of the final polymer depended markedly upon the degree of purification of the dichloride. The reaction of diethylsilicanediol with phosphorous pentoxide was also studied; the predominating reaction appears to involve entrance of the pentoxide into the polymeric structure, rather than a simple acceleration of the polycondensation reaction by the removal of water.
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  • 8
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 127-145 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This and a following article review the literature from 1910-1945 on polymerization of olefins and diolefins in suspension and emulsion, and present a number of new measurements not published to date. The subject is considered mainly from the point of view of scientific information on the mechanism of polymerization in aqueous suspensions and emulsions, but brief mention is also made of the more important disclosures in the patent literature. The new data presented in this article refer to (1) initial rates of polymerization of styrene, methyl methacrylate, vinyl acetate and acrylonitrile in aqueous suspensions and in soap emulsions as a function of catalyst concentration, temperature, and soap concentration; (2) influence of water-soluble activators, such as sodium bisulfite; (3) influence of initial size of monomer droplets on initial rates of monomer consumption; (4) study, with the aid of the electron microscope, of size of monomer droplets and polymer particles throughout polymerization; and (5) a few experiments on side reactions in the domain of higher conversions. No attempt is made in this paper to review and appraise the very large number of recent patents (from about 1930 on), which protect special procedures on the use of various promoting, regulating, or modifying ingredients. A complete digest of this practice does not exist at present, but reference may be made to the excellent chapter on emulsion polymerization in the book of Talalay and Magat (55), to the very valuable compilation of patents by Hosch in “India Rubber World” (27), and to the enumeration of a selected number of patents in the book of Scheiber (50) on pages 210-213.
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  • 9
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 329-339 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of experiments on the elastic behavior of various textile materials was carried out. All results are described with the aid of a mechanical model. For this purpose it is necessary to introduce the possibility of a blockade of a part of the model. The elastic properties are characterized by the values of seven independent fundamental constants of the model. The value of one of these constants associated with the blockade can be determined experimentally in a direct way; it is found to be independent of the moisture content. The most important properties of the model correspond with the molecular image of Hermans.
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  • 10
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 353-363 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mixtures of butadiene and dimethylbutadiene with varying quantities of styrene and acrylonitrile have been copolymerized under various catalytic conditions at 100°C. The formation of cyclic dimers from dienes and vinyl compounds is, in some cases, much more pronounced than the dimerization of the dienes alone. Since the latter is also a kind of Diels-Alder reaction, a series with increasing dienophilic properties can be established from a comparison of the yields of cyclic dimers. From solubility and swelling experiments it is evident that the polymers prepared from butadiene and the vinyl compounds and those from dimethylbutadiene and acrylonitrile are true copolymers. The mechanical properties of the copolymers from butadiene and increasing amounts of a vinyl compound change gradually from those of a rubber to those of the polyvinyl compound. The copolymers from a mixture containing 30% styrene or acrylonitrile are very similar, respectively, to Buna S and Perbunan. Copolymers of the same composition from dimethylbutadiene and acrylonitrile, on the other hand, form a new class of thermoplastics with a much higher temperature of elasticity.
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  • 11
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 364-379 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolymerization in emulsion of butadiene with varying amounts of styrene and acrylonitrile and of dimethylbutadiene with the latter vinyl compound has been studied on a laboratory scale. An essential difference between polymeric vinyl compounds and polydienes is the olefinic character of the latter, which leads to typical secondary changes in the polymers originally formed during the completion of the reaction. Such changes are of fundamental importance for the ultimate mechanical properties of polymers and copolymers based on dienes. After a brief discussion of the general theoretical line of thought serving as a base for our experiments, the influence of various factors on the rate of polymerization is pointed out and demonstrated by experiments. The changes in the nitrogen content of copolymers from acrylonitrile and the yields as a function of the reaction time have also been studied. From an investigation of some physical properties, such as solubility and swelling, the existence of true copolymers (of unknown irregularity) has been established. Copolymers from dimethylbutadiene and acrylonitrile represent a new class of olefinic thermoplastics resembling gutta-percha. Abbreviations used are BP (benzoyl peroxide) and DAB (diazoaminobenzene).
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  • 12
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 380-388 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The transversal dimension of the statistical coil formed by a long-chain molecule in solution or in bulk rubber is independent of the longitudinal dimension, h1, of the coil as long as h1 is small compared with the length of the stretched molecule. On the other hand, the lateral dimension of a coil whose longitudinal vector, h1, is oriented in the direction of stretch undergoes a forced contraction during the deformation of bulk rubber. The forced contraction of the transversal dimension is therefore supplying an extra contribution to the entropy change. Its amount has been estimated in earlier work and it influences the numerical factor occurring in the formula connecting the strain-stretch relation for rubber with the molecular weight of the net fragments.
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  • 13
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The course of the reactions of benzoyl peroxide with cyclohexane and cyclohexene may be accounted for by a mechanism involving free radicals and radical chain reactions. With cyclohexane, the average length of the chain hardly exceeds one step and one mole of hydrocarbon reacts with one mole of peroxide. With cyclohexene, chains of two and three steps also occur and about two and one-half moles of hydrocarbon per mole of peroxide take part in the reaction. It is shown that this is due to the one-sided addition of the primary radicals (originating from the peroxide) to the double bond, yielding a new radical without a double bond which can in turn react in the same way with another unsaturated molecule, thus giving rise to polycyclic compounds (chain formation). This polymerization reaction is, however, soon halted by a competitive side reaction involving substitution of the α- (or β)-methylene group, which leaves the double bond intact. In polymerizable vinyl derivatives in which no reactive α-methylene group is present, the competitive reaction cannot occur and the radical chain reaction continues to form a growing chain of interlinked monomeric molecules with annihilation of the double bonds. The two terminal groups of the macromolecules of the final polymerizate are radicals originating from the peroxide used as a catalyst. If a solvent is used, radicals of the latter may also appear occasionally as terminal groups of the polymer. The mechanism of the catalytic action of diacyl peroxides in the polymerization of vinyl derivatives is thus clarified. The molecule linking reaction induced by free radicals in unsaturated compounds also provides an explanation of the action of benzoyl peroxide as a rubber vulcanizer; the peroxide radicals are found as substituents in the rubber molecule.
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  • 14
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 434-436 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By suitable alteration of the exponent the fit of viscosity-concentration data by a Philippoff type equation may be substantially improved. For a series of cellulose acetate solutions the exponent of best fit appears to be related to the physical properties and chemical type of the solvent.
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  • 15
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 16
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 175-182 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ultraviolet absorption of polystyrene, with maximum absorption at 262 mμ, is due to the presence of phenyl residues in the polymer. The specific extinction coefficient is constant, i.e., independent of the molecular weight of the polymer. This shows that the extinction of the phenyl residues is additive. On the basis of this fact, it is shown that the styrene content of a butadiene-styrene copolymer (such as GR-S rubber) can be determined by ultraviolet spectrophotometry. The relative precision of the determination is about 1%, the probable relative accuracy is about 3%.
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  • 17
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A micromethod is described for density determinations of artificial cellulose fibers by the floating method, in carbon tetrachloride in a dry and air-free atmosphere, permitting an accuracy of one part per thousand. The density is derived from the temperature at which the samples neither sink nor float. This temperature varies, with the kind of fiber, between 45° and 65°C. Measurements of the refractive power were carried out simultaneously. The refractivity calculated according to Gladstone and Dale yields slightly lower figures than those found for model fibers in the preceding communication (Part II). The average difference amounts to seven parts per thousand and is ascribed to a systematic error in the density determinations, due to a slight absorption of carbon tetrachloride by the fibers at elevated temperatures. This explanation is supported by experiments. The density of native ramie, of contracted and reoriented ramie, and of several series of rayon fibers spun with increasing stretch, is given. The conclusion is reached that the density is a measure of the percentage of crystalline substances in the fiber and it is shown that there is a correlation between density and sorptive capacity toward water vapor. The percentage of crystalline matter is estimated to be 55-60% in native ramie and 20-25% in rayon.
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  • 18
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    Journal of Polymer Science 1 (1946), S. 183-199 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecules of high-molecular substances, for instance, those present in rubber, can be treated statistically in two ways. On the one hand, these molecules are such complicated structures that it is possible to attribute a separate entropy and free energy to each giant molecule. On the other hand, solutions of high-molecular substances represent systems in which the single chain molecule is the elementary particle, and to which statistical considerations and concepts such as entropy and free energy can be applied. Depending upon the parameter considered, the same chain molecule must sometimes be treated as a complicated system and at other times as an elementary particle. The problems originating from the simultaneous existence of two stages in the statistical treatment are examined. It is shown that the entropy of an assembly of many chain molecules is not simply equal to the sum of the entropies of the separate chain molecules. This becomes apparent particularly when determining the distribution function with respect to a particular parameter (e.g., distance between the two end points of a molecule) from a statistical consideration of the single molecule on the one hand, and from a consideration of an assembly of identical molecules on the other hand. The relations between entropy and free energy of the individual particle and the a priori probabilities on which the treatment of an assembly is to be based are explained. It is further shown that the same particle can give rise to a macroscopic phenomenon in two ways and to approximately the same extent: first, as a complicated system, and second, as an element in a large assembly of identical particles. This applies in particular to the elastic retractive force and to the strain birefringence in rubber and related substances.
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  • 19
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of dienes under the influence of heat, of diazoaminobenzene, and of benzoyl peroxide, has been studied. Diazoaminobenzene probably acts as a slow, but continuous, source of free radicals giving quantitative yields of methyl rubber of good quality from dimethylbutadiene after a few days to a few weeks at 100-125°C. The effect of diazoaminobenzene on butadiene is the same, but the rate of the uncatalyzed dimerization of butadiene at 100°C. is as fast as that of dimethylbutadiene at 150°C. and, therefore, dimerization interferes much more strongly with the polymerization of butadiene. Only 60% of polybutadiene has been obtained. A few experiments with isoprene showed its position between the two other dienes. The effect of benzoyl peroxide on the polymerization of the dienes appeared to be much smaller than was expected from its known catalytic action on the polymerization of vinyl compounds, e.g., styrene, for in this case its activity is about 100-1000 times greater than that of diazoaminobenzene. It is assumed that a larger number of radicals, produced by the fast decomposition of benzoyl peroxide, causes this difference. Diazoaminobenzene has about the same effect on the polymerization of styrene and acrylonitrile as on that of the dienes. The catalytic effect of benzoyl peroxide on the polymerization of the dienes is, on the contrary, 10,000-100,000 times smaller than on that of the vinyl compounds. This difference can be understood by the assumption that the catalyst is quickly used up by oxidizing the dienes and their polymers. While methyl rubber and the polyisoprene resemble raw natural rubber, polybutadiene, prepared under comparable conditions, is hard, swells moderately, and has a tendency to become brittle as a result of oxidation (aging). Abbreviations used are DAB (= diazoaminobenzene) and BP (= benzoyl peroxide).
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  • 20
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 217-224 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chief result of irradiation of cellulose acetate-butyrate with ultraviolet light is cleavage of the cellulose chains so that the average molecular weight is lowered. The exposed material dissolves more slowly in common solvents than the unexposed. The acyl content and carbon and hydrogen contents are not altered appreciably. The rate of the reaction is independent of the type of common mineral impurities, the concentration of expected decomposition products, such as acetic and butyric acids, and the molecular weight of the cellulose ester. Ultraviolet light is necessary for appreciable reaction. Wave lengths shorter than 3500 Å. are most effective; longer wave lenghts are much less active.
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  • 21
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 225-228 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A rapid procedure is described for estimating the average molecular weights of polyisobutylenes from deformation-rate measurements.
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  • 22
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 1 (1946), S. 229-230 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 23
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    Journal of Polymer Science 1 (1946), S. 230-231 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 24
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 25
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    Journal of Polymer Science 1 (1946), S. 245-246 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A device is described which permits rapid sampling of systems under pressure.
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  • 26
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    Journal of Polymer Science 1 (1946), S. 237-244 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chain lengths of polymethyl methacrylates prepared with ferrous ion-hydrogen peroxide as the initiating system are consistent with the scheme advanced for the mechanism of the polymerization. The relation between intrinsic viscosity in benzene and molecular weight for fractionated polymethyl methacrylate has been determined and leads to the equation: n = 2.81 × 103 [η]C6H61.32. This equation agrees very well with the data of Schulz, provided that the correct method of extrapolating the osmotic pressures to zero concentration is used. Using the relationship between [η]C6H6 and [η]CHCl3 obtained experimentally, the relation between n and [η]CHCl3 (at 20°C.) is: n = 1.81 l3 × 103[η]CHCl31.22.
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  • 27
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    Journal of Polymer Science 1 (1946), S. 233-236 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that the sedimentation and diffusion constants of cellulose at infinite dilution conform with a formula derived on the assumption of randomly coiled structures. The principle is introduced that the sedimentation velocity of closely packed particles moving through a liquid exerts an influence on their motion, according to known hydrodynamic laws.
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  • 28
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A comparison has been made of the ultraviolet spectrophotometric and chlorine analysis methods for the composition of copolymers of butadiene and p-chlorostyrene. The results of the two methods are in good agreement.
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  • 29
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    Journal of Polymer Science 1 (1946), S. 249-258 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The density-gradient tube is a special glass vessel in which a vertical linear density gradient of almost any desired magnitude can be maintained in a stable condition for prolonged periods by using liquids or solutions of the proper density. This article describes the application of such a device to three typical problems appearing in the field of high polymers: crystallization-rate data, inhomogeneities in composition of copolymers, and rates of polymerization. Possible application to still other problems is indicated.
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  • 30
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The technique of obtaining polystyrene silica replicas from surfaces and cross sections of fibers is described and electron micrographs obtained from replicas of several fibers are shown.
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  • 31
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    Journal of Polymer Science 1 (1946), S. 266-274 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By embedding submicroscopic silver rodlets in micellar systems with fibrous structures, unexpectedly strongly anisotropic rodlet compounds bodies are formed. The observed dichroism, indigo blue-straw yellow, suggests the possibility that a particular anisotropic modification of silver is being dealt with, instead of cubic silver. On applying Wiener's compound body formulas, it appears, however, that in the short-wave region the observed anisotropic effects (negative rodlet double refraction and dichroism) can be computed from the optical properties of isotropic silver. In the spectral region of the average and long waves, differences are found between the observed anisotropy and the value calculated by means of Wiener's formulas. These differences are, however, not of such a nature that it is necessary to assume an unknown allotropic modification of silver with particular optically anisotropic properties in order to explain them.
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  • 32
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    Journal of Polymer Science 1 (1946), S. 289-292 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mixed cellulose acetate-ethers were prepared which contain basic-type nitrogen groups whose films were dyed by xylene brilliant blue. β-Aminoethoxylcellulose acetate was prepared from cellulose diacetate and yarn-type cellulose acetate-propionate using ethyleneimine. β-Cyanoethoxylcellulose acetate was prepared from β-cyanoethoxylcellulose and from cellulose acetate using acrylonitrile with an organic base as catalyst. The solubilities of the mixed ether-esters containing basic type nitrogen groups were less than those of cellulose esters and ethers of comparable degrees of substitution.
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  • 33
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Butadiene and styrene have been copolymerized by the use of sodium sand as a catalyst. The copolymers containing 75 parts of butadiene and 25 parts of styrene and made at 30° and 50° are soluble in benzene and have intrinsic viscosities ranging from 2.5 to 7.5. The copolymers has a very nearly constant composition throughout the course of the polymerization. The amount of butadiene which has entered the chain by 1,2 addition is greater than in the case of the emulsion copolymer.
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  • 34
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Whatever additional factors may be concerned in the production of good vulcanizates from natural rubber by the action of sulfur, there is no doubt that the action of sulfur on olefinic materials in general at the ordinary vulcanization temperature is a chemical one, the primary course of which is determined largely by the constitution of the olefin, and hence may be profitably studied by experimentation with olefins of different unsaturation patterns. Unaccelerated reaction between sulfur and simple monoolefins leads almost exclusively to cross linking of the separate olefin molecules, mostly in pairs, by groups of sulfur atoms. When, however, two or more olefinic units occur in the same molecule, as in the disoprenic hydrocarbons, intramolecular cross linking, i.e., cyclization, at once becomes possible, and the result of sulfur action consists partly in the cross linking of separate molecules as with the monoolefins, but largely in cyclization of the individual olefinic chains, thereby forming sulfur-containing rings. These changes entail a certain loss of unsaturation, from which deductions can be made as to the mechanism of the reaction.
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  • 35
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Experimental data are presented on the monomer composition of copolymers of butadiene and styrene prepared by emulsion polymerization at 50°C. The composition of the copolymers is shown to be unaffected by variations in the amount of emulsifier, of mercaptan, and of the nature of the water-soluble polymerization catalyst. The composition of the copolymers formed from a charge containing 25% styrene (by wt.) can be represented accurately over the entire conversion range by the approximate theory according to which each monomer disappears by a first order reaction with the growing chain of the polymer, without taking into account the fact that the end of the growing chain to which the monomer adds may be a radical derived from either of the two monomer molecules. If the ratio of monomers in the charge is varied within wide limits, however, it is found that the simple theory is not adequate and it is necessary to consider that the chain may end with different radicals. The analysis of the experimental data shows that a butadiene molecule adds more rapidly than a styrene molecule to a radical derived either from a butadience or a styrene molecule.
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  • 36
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Squalene containing six isoprene units is more free of end-group effects and less limited in the range of space-distributional contortions of its carbon chain than mono- and diolefins. Hence it is more comparable with rubber than the latter group where matters of chemical reactivity are concerned. Nevertheless, in its reaction with sulfur, squalene pursues a course very similar to that followed by the diisoprene, dihydromyrcene, in that intramolecular sulfide linkages as well as intermolecular polysulfide linkages are formed. Taking into consideration the amount of sulfur which would suffice for the establishment of some given number of the simplest possible intermolecular linkages (i.e., monosulfide linkages), the efficiency of sulfur as a cross-linking reagent during the vulcanization of squalene is seen to be of a rather low order; this condition might be expected to hold for rubber in the absence of auxiliary mechanisms. So far as can be determined by direct experiment the action of sulfur in forming cross links is not essentially different from that encountered with squalene, since there are indications that both intra- and intermolecular sulfide linkages are formed - the latter being of both dialkenyl and dialkyl sulfide type, and, possibly also of alkenyl alkyl type. Under the influence of small amounts of zinc oxide or of various nitrogen-containing organic accelerators, sulfur reacts with the thiol groups of organic mercaptans forming di- and polysulfides, together with hydrogen sulfide. In the presence of rubber the same reaction occurs without actual liberation of hydrogen sulfide and it thus appears that if any thiol groups are formed as intermediates in vulcanization reactions, they will undergo ready conversion into intermolecular di- and polysulfide linkages. This may well represent an important auxiliary mechanism of cross linking.
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  • 37
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Hydrogen sulfide has often been thought to play an important role in the sulfur vulcanization of natural rubber. A study has therefore been made of the reaction of hydrogen sulfide with olefins, including polyisoprenes, with special reference to the capacity of the reagent to react with olefins in the presence of free sulfur. Comparison of the products so obtained with those derived (a) by light-catalyzed reaction of hydrogen sulfide and (b) by reaction of free sulfur with polyisoprenes has greatly assisted the understanding of the course of sulfur reaction in vulcanization processes.
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  • 38
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the emulsion polymerization of butadiene, styrene, or both, potassium persulfate is often used as the catalyst. A convenient concentration of potassium persulfate in the aqueous layer of the charge is 0.10-0.2%; the method of analysis should therefore be suitable for very small persulfate concentrations. Three methods have been investigated. In the volumetric method the persulfate is allowed to react in an acid medium with an excess of standard ferrous iron, the excess being back-titrated after a given period of time with standard ceric cerium solution. The recommended procedure was found accurate and precise within 0.5%, even at such small concentrations as 5 mg. of potassium persulfate per 100 ml. When latex is analyzed by this method, the polymer is first removed by coagulation with sulfuric acid and the persulfate determined in the filtrate. In order to obtain reliable results the reaction between the persulfate and ferrous iron in the filtrate must be carried out in the absence of oxygen, although this is not necessary in solutions of pure persulfate. The interference by oxygen is attributed to substances of peroxidic character in the fatty acid soaps used as emulsifiers in the emulsion polymerization. The colorimetric method (“Becco” method) is based upon the oxidation of the leuco base of commercial wool green BSMA to a green dye by the persulfate and (colorimetric) measurement of the dye formed. The various factors affecting the accuracy and precision of this method have been investigated and a procedure is given for the analysis of latex. For several reasons, the volumetric and polarographic methods are superior to the colorimetric method. Persulfate in a latex can be determined accurately by polarographic analysis of the latex filtrate after removal of the polymer with sulfuric acid. The polarographic determination can be carried out, in the presence of oxygen, with simple equipment. The method is rapid and precise.
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  • 39
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    Journal of Polymer Science 1 (1946), S. 389-392 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A brief outline is given of the present status of research on the problem of the deformation mechanism of cellulose gels. Emphasis is placed on the prevailing idea of a molecular network structure and recognition of the existence of an intimate relationship between the phenomena of deformation and those of swelling. In these respects the problems involved in cellulose research seem to show a marked convergence with those which emerge from recent developments in rubber research. The principle of Kratky's theory of “affined transformation” and the experiments carried out by this author in order to verify his theory are discussed briefly.
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  • 40
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The paper offers a verification by x-ray experiments of Kratky's theory of affined transformation (affine Raumverzerrung), aiming at an explanation of the mechanism of deformation of swollen cellulose gels upon stretching. Isotropic model filaments of various degrees of swelling were stretched to various extents and x-ray photographs were then taken. Following Kratky, the intensity distribution along the sickles of two paratropic planes of the ribbon-shaped crystallites, the lamellar plane, A0 and the A3 plane (perpendicular to the latter) were measured and the average orientation, expressed in terms of the orientation factor, fx, was calculated. The superposition of the (021) interference on that of the A3 sickle, which had been neglected by Kratky, was accounted for. The experimental results are in conformity with certain characteristic features of the theory; (a) the orientation of the A0 planes advances more rapidly than that of the A3 planes; (b) regardless of the initial degree of swelling of the isotropic filament, the average orientation is actually a univocal function of the elongation, va. On the other hand, the rate of orientation appears to be much greater than that required by theory; the average orientation, expressed in terms of the orientation factor, increases almost twice as rapidly. It is shown, moreover, that, apart from low degrees of orientation, Kratky's theory fails to explain the velocity function of the relative rotation of the crystallites, as derived from the experimental data according to a procedure proposed by Kratky. It is concluded that further work is required to elucidate the mechanism of deformation.
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  • 41
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    Journal of Polymer Science 1 (1946), S. 419-428 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements of the viscosity of polyvinyl alcohol solutions may be correlated with the chemical nature of the polymer. In particular it is shown that polyvinyl alcohol contains carbonyl groups in the polymer chain, which are to some extent present as ketols. The presence of these keto groups has been demonstrated by a combination of spectrophotometric and chemical techniques. The carbonyl groups appear to be randomly distributed along the polymer chain and also seem to be independent of chain length. The presence of keto groups along the chain allows an explanation for the behavior of aqueous polyvinyl alcohol solutions with acid or alkali.
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  • 42
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A convenient procedure for the determination of polystyrene in GR-S is given. The method depends upon degradation of the GR-S by tert-butyl hydroperoxide in the presence of a trace of osmium tetroxide. Polystyrene is not attacked and is separated by precipitation with ethanol.
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  • 43
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    Journal of Polymer Science 1 (1946), S. 437-439 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 44
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    Journal of Polymer Science 1 (1946), S. 466-474 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the polymerization of methyl methacrylate in emulsions has been examined. The initial rate of polymerization is independent of the amount of discontinuous monomer phase present and it is concluded that initiation occurs in the aqueous phase. Monomer is observed to disappear from the discontinuous phase more quickly than it polymerizes, and probably forms a monomer-polymer mixture with the polymer produced. An increase in the subsequent rate of polymerization is attributed to the fact that propagation of the growing polymer chains occurs in this monomer-polymer mixture and this entails a decrease in the velocity of termination due to the high viscosity of such mixtures.
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  • 45
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    Journal of Polymer Science 1 (1946), S. 455-465 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An investigation of the copolymerization of many monomer pairs induced by benzoyl peroxide has shown that an order of monomer reactivity with radicals exists. By utilizing the data available, it was possible to make a semiquantitative arrangement of many monomers according to their relative rates of reaction with radicals. A symmetrical selectivity factor is assumed to account for deviations from the order in copolymerization reactions. This selectivity may be attributed to (1) complex formation between monomers or to (2) dipole, steric, or other factors which are independent of concentration. Copolymerization equations have been derived for each case and application of them to styrene-methyl methacrylate mixtures has indicated that selectivity due to (2) is most important in this system. The equation for case (2) has been applied to other copolymer systems.
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  • 46
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    Journal of Polymer Science 1 (1946), S. 529-534 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An elementary theory is given for the rolling of polymeric materials, for the case in which the deformation is largely an irreversible flow of the viscous type. The theory treats the rolling process as the homogeneous deformation of volume elements over the arc of contact and neglects frictional forces that may exist at the roll surface. A numerical example is given of the calculation of roll pressure, which agrees with available data to a factor of two or better. A more complete test will require parallel measurements of viscosity and roll pressure on the same material.
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  • 47
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    Journal of Polymer Science 1 (1946), S. 484-494 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By treating potato juice with acid it was found that potato globulin is converted to albumin and an insoluble casein-like protein. Potato albumin, salted out with ammonium sulfate and purified by dialysis, is very similar to ovalbumin; it is reconverted into a globulin-like protein by alkali. Solutions of potato albumin in water, as well as in acids and alkali, have a very low viscosity. Alkaline solutions of globulin have a greater viscosity than those of albumin; the viscosity numbers of the difficulty soluble protein are even greater. On the basis of the viscosity data, it was concluded that the albumin particles are corpuscular, the globulin molecules are longitudinal, and that the dissymetry is greatest for the difficulty soluble protein particles. On the basis of the different solubilities of all three proteins (which apparently have approximately the same chemical composition), it was concluded that the albumin molecule was the smallest and the difficulty soluble protein molecule the largest. An aqueous solution of potato albumin is denatured when heated to 50-60°, the viscosity thereby increasing more than 100-fold. The solutions become only slightly turbid, but do not flocculate. This unusual viscosity rise can be explained by the transformation of globular albumin molecules into fibrous, elongated particles. Only a slight viscosity increase is observed when alkaline solutions of albumin are heated. Albumin, in the presence of small amounts of salt, is precipitated at 50-60°; the salts also lower the turbidity point. However, very small concentrations of calcium chloride have a stabilizing effect. Albumin is not coagulated at room temperature by 1-2 N salt solutions. The experiments on the effect of cold on potato albumin showed that albumin, after congealing and thawing out, was more easily precipitated than the control solution. The viscosity of the cold-damaged albumin was somewhat less than that of the control solution. It was ascertained that the deaminated product of potato albumin was very similar to deaminated ovalbumin (solutions of high viscosity; linear colloid).
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  • 48
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A general theory is proposed to account quantitatively for the heat polymerization and gelation of the nonconjugated vegetable oils. This is based on a direct approach to polyfunctionality as developed from quantitative considerations of partial random distribution of the fatty acid components in the triglyceride molecules. The differing polymerization rates of linseed and soybean oils are accounted for on the basis of the assumed influence of certain cis-trans geometric isomers. The theory accounts for the anomalous extensive linear polymerization and nongelation of olive oil. Calculations from the theory agree substantially with experimental results on average molecular weight, iodine value, and the percentage of insoluble, infusible cross-linked polymers.
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  • 49
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    Journal of Polymer Science 2 (1947), S. 349-349 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Polymer Science 2 (1947), S. 349-350 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 51
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    Journal of Polymer Science 2 (1947), S. 10-11 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The refractive index-temperature data for polyvinyl acetate show a second-order phase transition temperature of 24°C.
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  • 52
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The conductance in diphenyl ether at 35°C. and 60 cycles of the picrate of a 4-vinylpyridine-styrene copolymer (10:90) has been measured. The equivalent conductance, based on the nitrogen content, is of the same order as that of picoline picrate, and varies with concentration in accordance with the law of ion association.
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  • 53
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    Journal of Polymer Science 2 (1947), S. 21-35 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A polyvinyl acetate polymer of medium viscosity was fractionated into sixteen fractions (first series) and three of the larger of these further separated into twenty subfractions (second series). The intrinsic viscosities and the osmotic pressure molecular weights were determined at 25°C. and the relation between them was found to be expressed by the equations: first series: [η] = (1.88 × 10-4) M0.69; second series: [η] = (1.76 × 10-4) M0.68. The data indicate that little, if any, increase in homogeneity is to be expected by further successive fractionations and that the equations applicable to the second fractionation series are representative of essentially homogeneous polyvinyl acetates in acetone. An equation applicable to fractionated and unfractionated vinyl acetate polymers is described that is useful in obtaining the intrinsic viscosity from a single viscosity measurement. Several unfractionated materials from different sources were also studied and the calculated ratios of the viscosity-average to the number-average molecular weight indicate that the degree of heterogeneity of chain-length distribution increases with increasing average molecular weight.
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  • 54
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    Journal of Polymer Science 2 (1947), S. 354-354 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 55
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 56
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling of vulcanized natural rubber, Buna S, neoprene, Perbunan, and Perbunan Extra was measured in various organic liquids. The essential influence of polarizability and polarity on the swelling equilibrium is illustrated by comparing series of solvents and polymers with gradually changing geometrical and chemical structure. Experiments on the influence of temperature and of strain on the swelling equilibrium are reported. The swelling properties of ebonites and similar derivatives allow some conclusions on the amount of cross linking in these polymers.
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  • 57
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    Journal of Polymer Science 2 (1947), S. 371-380 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Practical, theoretical, and experimental aspects, including sources of error and methods of control, of the water and water vapor permeability of organic membranes are discussed. Determinations of the permeability have been made at two different temperatures. Data are given on: polyethylene (alkathene, Imperial Chemical Industries), polystyrene (Styroflex, D. Seekabelwerke), chlorinated polyvinyl chloride (Vinifol, I. G. farbenindustrie), cellulose acetates (Triacetat, Schering, and Triafol, I. G. Farbenindustrie), a plasticized polyvinyl chloride (Welvic, Imperial Chemical Industries), and a copolymer of vinylidene chloride and vinyl chloride (Saran, Dow).
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    Journal of Polymer Science 2 (1947), S. 387-396 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The heats of polymerization of acrylic acid, methyl acrylate, methacrylic acid, and methyl methacrylate have been measured. Values for the heat of polymerization of unstrained polymer molecules have been calculated, and the low heat of polymerization of methyl methacrylate has been attributed to the presence of steric hindrance in the polymer molecule.
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    Journal of Polymer Science 2 (1947), S. 381-386 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The permeability of vulcanized gutta-percha membranes to gases was determined in relation to the rate of diffusion and solubility. The measurements, as functions of temperature, with four gases were taken below and above the melting point of gutta-percha. The evidence is that the rates of permeation and diffusion increase sharply at approximately 45°C., due to melting of the gutta-percha. In the same way, although to a lesser degree, the solubility of the gas likewise increases at the melting point. The activation energies of permeation and diffusion with the heat of solution were computed from the temperature function of those quantities. It follows from the results that crystallization of the elastomer reduces the gas-solubility, the diffusivity, and the permeability - and increases the activation energy of diffusion. The interpretation of this high activation energy of diffusion is that, because of the crystallization, the macromolecules of the membrane adhere so firmly that greater energy is required to admit the gas molecules.
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  • 60
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A description is given of the preparation, birefringence, and swelling capacity of a series of microscopically homogeneous, partially acetylated cellulose model filaments with an acetyl content varying from 0 to 2.3 acetyl groups per glucose residue, and obtained either by acetylation or by deacetylation. A higher degree of acetylation of these artificial fibers could not be attained without destruction of the fiber. The same holds true for native ramie fibers. The swelling was studied in water, acetone, and methanol. The degree of swelling of the filaments plotted against acetyl content yields entirely different curves for the acetylation and the deacetylation series. These curves can be readily explained by the hypothesis that the intercrystalline (so-called amorphous) portion of the fiber substance is more accessible to the esterification and saponification reactions and is affected earlier than the crystalline portion. The birefringence of the acetylation series shows but a small - although apparently real - difference from that of the saponification series.
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    Journal of Polymer Science 2 (1947), S. 412-419 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Multi-ingredient polymeric amides have been prepared by the condensation, under amide-forming conditions of various combinations and ratios of components comprising hexamethylenediammonium adipate, hexamethylenediammonium sebacate, and ∊-aminocaproic acid or ∊-caprolactam. The physical properties of the investigated linear polymeric amides range, depending upon the polymer components and the proportions employed, from high-softening, stiff, and difficulty soluble compositions to relatively low-softening, pliable, and easily soluble polymers.
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  • 62
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    Notes: A discussion is offered of the x-ray patterns of partially acetylated and saponified cellulose model filaments with varying acetyl contents. They are substantially in conformity with the swelling experiments previously described in Part I (page 397) of this paper. (1) In nonrecrystallized filaments, chemical reaction takes place in the crystallites and the intercrystalline regions from the very beginning of the experiment. The rate of chemical conversion, however, is larger in the latter. (2) Acetylation of the hydrate cellulose crystallites results in a gradual increase in the (101) spacing, A0; the A3 and A4 reflections [corresponding to (101) and (002), respectively] remain unimpaired up to a gross acetyl content of at least 1.5 acetyl groups per glucose residue. (3) Maximally acetylated filaments containing 2.3 acetyl groups per glucose residue may be recrystallized by heating in methanol or ethanol. The diagram of the recrystallized product is identical with the pattern of cellulose triacetate II. With about halfway acetylated or saponified products, recrystallization is not realizable by means of a heating process in water or methanol. (4) Enhanced degree of local order as the result of previous recrystallization of maximally acetylated products produces a more pronounced difference in rate of saponification between the “crystalline” and “amorphous” fiber portions.
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    Journal of Polymer Science 2 (1947), S. 420-431 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Bomb calorimetric measurements have yielded for the heats of combustion ( - ΔHoc) at 25°C. of liquid styrene and solid polystyrene to form gaseous carbon dioxide and liquid water the values 4394.88 ± 0.67 int. kjoule per mole (1050.58 ± 0.14 kcal. per mole), and 4325.09 ± 0.42 int. kjoule per C8H8 unit (1033.89 ± 0.10 kcal. per C8H8 unit), respectively, and for the heat of polymerization of liquid styrene to solid polystyrene at 25°C. the value 69.79 ± 0.66 int. kjoule per mole (16.68 ± 0.16 kcal. per mole). The results obtained on two samples of polystyrene of different molecular weight were in agreement within the precision of the measurements. Measurements of the heat of solution of solid polystyrene in liquid monomeric styrene gave the value 3.59 ± 0.21 int. kjoule (0.86 ± 0.05 kcal.) evolved per C8H8 unit of polystyrene at 25°C. Addition of this to the value for the heat of polymerization of liquid styrene to solid polystyrene gives the value 73.38 ± 0.69 int. kjoule (17.54 ± 0.16 kcal.) per mole of styrene for the heat of polymerization of liquid styrene at 25°C., when the final product is a solution of polystyrene in styrene containing 6.9% by weight of polystyrene.
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    Journal of Polymer Science 2 (1947), S. 447-448 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science 2 (1947), S. 432-446 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Potentiometric titrations of polymethacrylic acid were performed at different concentrations, different molecular weights, and in the presence of neutral salts, as well as in dioxane-water mixtures. It was shown that the pH of the solutions fulfills the relation, pH = pK  -  n log [(1  -  α)/α]. pK and n are independent of the molecular weight and concentration if a suitable activity factor is introduced. The equation is applicable to free acid solutions as well as acid mixtures. Copolymers of the type, polyallyl acetate-maleic acid, show a more complicated curve. The curve is of the “polydibasic” type. Each branch of it fits equation (2) well. The formula is analyzed and is proposed to be the result of the action of the Maxwell-Partington statistical factor, as well as of the decrease in entropy accompanying the stretch of the randomly kinked molecule. This stretch is caused by the repulsive forces between the ionized carboxyl groups. The distribution curves of the various degrees of ionization present, for any pH, are given. The activity correction implies small units of the size of one or two carboxyl groups. The behavior in salt solutions is dependent not only on the activity correction, but also on the salting-out factor. This factor is high in polyvalent salts. The titration curves in dioxane-water mixtures are satisfactorily accounted for by the change in the activity factor with the dielectric constant.
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    Journal of Polymer Science 2 (1947), S. 449-449 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Polymer Science 2 (1947), S. 449-449 
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    Journal of Polymer Science 2 (1947), S. 449-450 
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  • 69
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    Notes: The inhibition by quinone and the retardation by hydroquinone derivatives of the peroxide-induced polymerization of styrene have been studied. We have examined the end products of benzoyl peroxide at 74°C. in benzene, alone and in the presence of quinone and hydroquinone ethers, and in styrene in benzene, both with and without quinone. Absorption spectra have been obtained after several time intervals for some of these systems and for the benzoyl peroxide-styrene-benzene system, alone and in the presence of alkyl substituted hydroquinones. Consideration of the end products indicates that quinone interferes but little with the normal initiation process, particularly at low (0.0045 M) concentrations. Inhibition appears to result largely from reaction between the inhibitor and newly initiated chains. Quinone is converted to products - some of which are phenolic - which do not absorb in the visible. The phenolic products may react with the peroxide or radicals from it, interfering with the normal initiation reaction. The hydroquinone derivatives, which are retarders for the polymerization, appear to be converted initially to quinonoid products. The reactions in inhibition and retardation are discussed.
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    Journal of Polymer Science 2 (1947), S. 487-487 
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  • 71
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    Notes: The correlation between structure and properties of elastomers prepared from dienes, natural rubber, gutta-percha, as well as those of some significant derivatives of natural rubber, are discussed. The similar influence exerted by methyl groups on the brittle point, elastic recovery, and permeability to gases is demonstrated and separated from the effect caused by insertion of  - CH2 - CHR -  groups in straight-chain polybutadiene, which takes place during copolymerization or 1,2 addition. The preponderant influence of an unbranched-chain structure on tensile strength at elevated temperatures and in the swollen state is illustrated. Complex compounds with silver nitrate provide further evidence for the particular symmetry of the natural rubber chain: They are rein forcing agents for synthetic elastomers. The brittle points of hydrochlorides from natural rubber, gutta-percha, and polyisoprene are compared with those of polyvinyl compounds. Correlation between the structure of molecular units in a polymeric paraffin derivative and its elasticity is pointed out.
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    Journal of Polymer Science 2 (1947), S. 544-544 
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    Journal of Polymer Science 3 (1948), S. 302-303 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Journal of Polymer Science 3 (1948), S. 303-303 
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    Journal of Polymer Science 3 (1948), S. 303-303 
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    Journal of Polymer Science 3 (1948), S. 304-304 
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    Journal of Polymer Science 2 (1947), S. 546-546 
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    Journal of Polymer Science 2 (1947), S. 547-564 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Part I traces fine structural features of polythene, beginning with the arrangement of carbon atoms disclosed by x-ray diffraction, and including the incorporation of crystalline segments into crystallites, and finally the combination of crystallites and amorphous regions to form spherulites-the largest structural elements of polythene. Attention is called to the frequent occurrence of side chains in the molecules. The structures of spherulitic and cold-drawn polythenes are compared. Part II describes an experimental study of the cold-drawing of polythene which discloses an interesting variant of this process, designated as “redrawing,” in which dimensional changes differ greatly from those of ordinary cold-drawing. On the basis of these observations and structural considerations presented in Part I, a mechanism of cold-drawing as a rheological process is outlined.
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    Journal of Polymer Science 2 (1947), S. 583-592 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Various problems related to the determination with x-rays of the atomic configuration of organic fibers are discussed. Because of the approximate nature of the underlying theory, too far-reaching conclusions should be avoided, especially since, in the case of organic fibers, the situation is much less simple than in the case of sodium chloride powder or metallic wires, for example. Because of these facts, and because of the relative poorness of fiber patterns, the atomic coordinates as well as the space group of the structure can be found only within certain limits. Though the use of macroscopic models is very helpful in visualizing the spatial arrangement, no conclusions of a quantitative nature can be reached with their aid because the assumptions embodied in these models are too numerous and too inexact to justify speculations on details of the structure. In the case of cellulose fibers, it is shown that the problem cannot yet be solved completely; the outlook for a really unique solution is not hopeful. The structure proposed by Meyer and Misch is still the best approximation available. More recent propositions are shown to be less well founded; the atomic configuration introduced by Peirce, being at variance with chemical, crystallographic and x-ray evidence, is to be discarded.
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    Journal of Polymer Science 2 (1947), S. 565-582 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: From the results of initial acid-catalyzed hydrolysis of cellulose, and from certain data in the literature it is concluded that (1) native cellulose possesses an indefinitely high molecular weight; (2) as a consequence of common procedure adhered to by most investigators, native cellulose is unintentionally degraded to about DP 3000; (3) mild, initial acidic degradation, intentional or accidental, causes further decrease in the DP values down to the probable limiting value of 128 or 256, with complete loss of the tensile strength of the cellulose fiber; and (4) the few covalent bonds (about 0.3%) which become cleaved during these mild reactions are equally spaced, acid-sensitive, and entirely different from the regular 1,4-glycosidic bonds which are responsible for the random hydrolysis of cellulose in strongly acidic media. It is suggested that these acid-sensitive linkages represent hemiacetal or acetal bonds which originate from openchain glucose anhydride residues of “limit hydrocellulose” units and connect the latter along the a and b axes of the fiber. The length of the “limit hydrocellulose” is supposed to correspond to that of 27 = 128 glucose anhydride residues - that is, 660 Å., or twice these figures. Extension of this concept to starch leads to the postulate of a three-dimensional network of glucose anhydride units of indefinite number. The latter are held together by regular 1,4-α-glucopyranosidic bonds and, at short intervals, probably by acetal bonds of open-chain glucose anhydride residues. On mild, acid-catalyzed hy-drolysis these acid-sensitive linkages rupture rapidly and completely, giving rise to a material which consists of linear molecules only, containing 1,4-, 1,6-, and possibly 1,3-, glycosidic bonds between two adjacent glucose anhydride residues.
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    Notes: Experimental methods for measuring the mechanical properties of concentrated polymer solutions and other viscoelastic systems under periodically varying stresses are reviewed. These include direct measurements of stress and strain, measurements of response at resonance frequencies determined by the inertia of the apparatus, propagation of waves in extended media, and measurements of resonance vibrations. The conditions for the suitability of each method are discussed, and equations for the interrelation of the various quantities measured are given. Examples are shown to illustrate the fitting of experimental data to the calculated behavior of mechanical models, in order to obtain frequency-independent mechanical constants which can be interpreted in terms of molecular behavior.
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    Journal of Polymer Science 2 (1947), S. 612-622 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Intrinsic viscosity, calculated in accordance with the empirical relation established by Schulz and Huggins, deviates considerably from its true value in the case of increasing viscosities. The introduction of a simple corrective, second degree term η2sp/150, applicable to most of the polymers, permits the direct computation of intrinsic viscosity based upon polymer solutions of various concentrations. Specific viscosities may vary to a great extent and reach a value as high as 15; the use of high concentrations permits the reduction of experimental errors and the determination, to within an average of one per cent, of the intrinsic viscosity of the polymer sample, and thus of its molecular weight.
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    Journal of Polymer Science 2 (1947), S. 623-625 
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    Topics: Chemistry and Pharmacology , Physics
    Notes: A substance may have a precipitating action on other dissolved substances. The concentration at which this action becomes apparent depends not only on the chemical nature of the constituents, but also on their molecular weights. In a homologous series the precipitating power increases with increasing molecular weight until it attains a very high value, as in macromolecules. The incompatibility of high polymers, which is manifested at very great dilutions, is due to this increase in the precipitating power with an increase of the molecular weight.
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    Journal of Polymer Science 2 (1947), S. 626-631 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The same point in the space cannot be occupied simultaneously by two molecules. In a solution of rigid rodlike macromolecules, each molecule prevents its neighbors from occupying certain positions, the whole of which form the forbidden angle. Calculation shows that in the case of rigid, filiform molecules, this angle is large even at very low concentrations. Isotropy is not possible at moderate concentrations. The consideration of the forbidden angle is necessary in the study of viscosity, osmotic pressure, flow birefringence, sedimentation, and molecular light scattering. In the solid state, the substance can be put under great tension, and the return to the normal state is extremely slow. This tension accounts for the abnormal solubility of disordered high polymers.
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    Notes: The orientation of model filaments stretched to various extents in three different states of swelling was investigated by quantitative x-ray analysis before and after drying. The change in orientation upon drying was found to be either very small or zero. This shows that the crystallites do not even approximately follow the rules of affined transformation which would require a very considerable increase in orientation on drying. There must be an entirely different mechanism which prevents the crystallites from being dragged along with the matrix in which they are embedded.
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    Notes: A solvent prepared by mixing 70 parts by volume of ethanol, 30 parts of toluene, and 10 parts of water is found to be a suitable solvent for the extraction of organic nonrubber material from GR-S. The presence of the water has no effect on the rate of extraction of the nonrubber, while it reduces the extractibility of low molecular polymer to one-tenth of that found in the absence of water in the solvent. A procedure is described for the determination of small amounts of GR-S in the extracts. This procedure is based on the quantitative precipitation of the ICl addition product of the rubber from a chloroform solution by addition of ethanol. A routine procedure for the determination of the amount of rubber in GR-S is given.
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    Journal of Polymer Science 3 (1948), S. 10-15 
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Expreiments have been carried out on the benzoyl-peroxide catalyzed polymerization of methyl isopropenyl ketone at 25 and 40°C. in cyclohexane, a solvent which dissolves the monomer but causes the polymer to be precipitated. It is shown that in solutions of suitable concentration (40-80%) the effect of the cyclohexane is to increase both the rate of polymerization and the intrinsic viscosity of the resulting polymer. The significance of these observations and of other recent experimental work is discussed.
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    Notes: Ten series of model filaments with increasing orientation and swelling degrees ranging between 16 and 1.2 were prepared from three viscoses containing 4, 6, and 10.5% cellulose. Their birefringence was measured and their x-ray diagrams taken and quantitatively evaluated in order to determine the over-all orientation of the iiber substance and that of the crystalline portion. It is shown that a general relation exists between the orientation of the crystallites and that of the entire fiber substance which is the same in all fibers stretched in the swollen state. Once the birefringence of a filament is known, the orientation factor of its crystallitee can be computed without taking an x-ray photograph. From the data further evidence can be derived to the effect that the orientation of the crystallitm cannot be accounted for by the theory of affined deformation.
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recently published measurements of moisture sorption vs. relative humidity for a series of proteins have previously been analyzed in a way which permits calculation of the integral free energy of sorption for any final pressure of water vapor. The present paper is an extension of these calculations to additional proteins from the list reported by Bull; integral and differential free energies and integral and differential heats and entropies of sorption have been calculated as functions of the amounts of water sorbed onsilk, wool, egg albumin (unlyophilized and heat coagulated), salmine, collagen, gelatin and lactoglobulin (crystalline and lyophilized). All calculations are referred to saturated water vapor as the standard state. Some of the proteins show positive net differential entropies of sorption at low vapor pressures. It is postulated that the partial molal entropy of sorption is made up of two terms, a negative entropy of sorption proper and a positive entropy of solution. Partial rearrangements of the protein chains at the beginning of the sorption process would effectively be an incipient solution which would give rise to a positive partial molal entropy of sorption if the second term is greater than the first. This speculation has support in the fact that the differential entropy of salmine, which dissolves at a relative vapor pressure of about 0.7, begins to show positive values at a relative vapor pressure of 0.35.
    Additional Material: 4 Ill.
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  • 90
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 3 (1948), S. 410-420 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The changes in the viscosity-average size distribution of polystyrene under conditions of simultaneous degradation and polymerization in toluene solutions have been observed. The appearance of the differential distribution curves for the degraded polymers and the polymerized monomer in the steady-state viscosity region are nearly identical. Osmotic pressure data on fractions of the degraded polymers do not show evidence for the occurrence of chain branching.
    Additional Material: 6 Ill.
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  • 91
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The combination of a diazothio ether and a mercaptan in an emulsion copolymerization recipe of butadiene and styrene containing potassium ferricyanide as a “catalyst” has a very strong activating effect on the polymerization. p-Methoxyphenyl diazothio-(2-naphthyl) ether, designated as MDN, was found to be particularly suitable. In the present paper, ordinary household soap (S.F. flakes) and dehydrogenated rosin soaps of varying degrees of purity have been used as emulsifiers. By using various tertiary or primary mercaptans, polymers of any degree of modification were obtained. The recommended recipe at 40°C. gives about 80% conversion in 10 hours. The rate of conversion is greatly increased by adding to the recipe substances which have a strongly alkaline reaction in water, as sodium carbonate, trisodium phosphate, or sodium hydroxide. With such “alkaline” recipes attractive rates of conversion are obtained at around 0°C.
    Additional Material: 10 Ill.
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  • 92
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 3 (1948), S. 438-443 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The adiabatic technique of making kinetic measurements has been applied to published time--temperature data concerning the vulcanization of Buna S with 6% sulfur. The kinetic parameters of the rate-determining step are calculated within stated limits of accuracy; the rate-determining step is thereby identified as the reaction S8 (ring) → S8 (chain biradical) which has been speculatively advanced as the first step in vulcanization by some investigators.
    Additional Material: 3 Ill.
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  • 93
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Five twelve-carbon mercaptans of definite structure are prepared and used to demonstrate that the rate of diffusion of mercaptan regulators in emulsion polymerization varies inversely with the length of the longest straight chain of the mercaptan structure (including the sulfur). In a given class of mercaptans (primary, secondary, or tertiary) the mercaptan consumption during polymerization varies directly with the diffusion rate. Solution viscosities of the resulting polymers are in accord with these findings.
    Additional Material: 3 Tab.
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  • 94
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been demonstrated that the homogeneity in respect to molecular weight of emulsion copolymers of butadiene and styrene can be increased by the use of certain derivatives of n-dodecyl mercaptan rather than the mercaptan itself. These derivatives decompose and relase n-dodecyl mercaptan at an even rate during the polymerization reaction. Several new derivatives of n-dodecyl mercaptan are described.
    Additional Material: 1 Ill.
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  • 95
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Precise analytical methods are developed using iodine monochloride for the determination of unsaturation in polybutadiene and polyisoprene and their copolymers with styrene. The complicating side reactions, splitting out and substitution, as well as the influence of the solvent employed are investigated in detail. It is concluded that GR-S at various conversions has the theoretical unsaturation. Emulsion polybutadiene exhibits 97 to 98% of the theoretical unsaturation, emulsion polyisoprene 97% sodium polybutadiene 92%, and sodium polyisoprene 85%. The amount of unsaturation in these last two polymers as well as in the sodium copolymer of butadiene and styrene (75:25) is considerable less than theoretically expected.
    Additional Material: 8 Ill.
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  • 96
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 3 (1948), S. 95-96 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
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  • 97
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Methods for the preparation of fiber-forming polymeric amides from ω-amino acids and The variation in melting points of the polymeric their amide-forming derivatives are described. The variation in melting points of the polymeric amides with increasing chain length of the recurring unit is discussed.
    Additional Material: 1 Ill.
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  • 98
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study has been made of the swelling characteristics of Styrene-divinylbenzene gels containing from 0.02 to 0.12% of the cross-linking agent. Variation in swelling of samples containing the same amount of divinylbenzene was shown to increase with decreasing divinylbenzene concentration. The influence of amount of cross-linking agent, type of solvent, and temperature, on equilibrium swelling is reported. By assuming that μg is 0.44 for polymer-toluene, values of μg for over 50 different solvents have been obtained. No values of μg below 0.42 were found. A correlation of swelling values and of μg values with cohesive energy densities of the solvents is presented. The polymer appears to have a cohesive energy density of 82 cal. per cc. Equilibrium swelling decreases slightly in toluene and methyl ethyl ketone but increases markedly in cyclohexane with rising temperature. Efforts to calculate gel constants from the temperature coefficient of swelling failed completely in the case of cyclohexane, and were only moderately successful with toluene. These temperature studies, and the cohesive energy density correlations both appear to indicate a lack of complete understanding about the physical significance of μ, and why it depends so markedly on concentration.
    Additional Material: 11 Ill.
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  • 99
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The German redox system of emulsion polymerization of butadiene and styrene has been found to be very sensitive to exact details of experimental procedure. Soap may be substituted for the alkanesulfonate used by the Germans; it is then unnecessary to add ferric laurate to the system.Careful investigation of the soap-emulsified mixture leads to the conclusion that 0.25 parts of benzoyl peroxide, 0.50 parts of ferrous sulfate heptahydrate, and 3.0 parts of sodium pyrophosphate decahydrate were the optimum concentrations of the essential ingredients for polymerization of an emulsion of 75 parts of butadiene and 25 parts of styrene in 200 parts of water and 5 parts of Procter and Gamble soap Flakes (S.F.) at 30°. At very low iron concentration the addition of a reducing agent as “booster” was beneficial; for this purpose sorbose can be replaced by fructose or, less satisfactorily, by a number of other reducing agents.
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  • 100
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 3 (1948), S. 141-142 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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