bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscoelastic properties of branched whole polymers. I. Calculation of relaxation times
Authors: Peticolas Warner L. 
Published: April 2003

AbstractThe calculations of the relaxation times of whole polymers has been extended to include the effect or branching. These relaxation times depend upon the weight average of the mean‐square radii, 〈R〉w, of the branched polymer molecules. It is proposed that this quantity may be obtained in a θ solvent from the equation [η] = 61/2ΦC〈R〉w, where [η] is the limiting viscosity number, Φ is a universal constant, and C = Kb, where b is the root‐mean‐square of the end‐to‐end distance of a submolecule and K is the ratio of the number of submolecules to the molecular weight. The constant C may be obtained from measurements of [η] and 〈R〉 on linear, monodisperse polymers. Equations are given by which the effect of branching and molecular weight distribution on rheological measurements may be calculated.
A study of the mechanism of interfacial polyamidation and polyesterification
Authors: Hodnett Ernest M. , Holmer Donald A. 
Published: April 2003

AbstractThe interfacial polyamidation reaction between phthaloyl chloride and piperazine and the interfacial polyesterification reaction between phthaloyl chloride and 4,4′‐isopropylidenediphenol were found to be second‐order at 0°C. Studies with C14‐labeled phthaloyl chloride and with piperazine in one case and with 4,4′‐isopropylidenediphenol in the other case showed no isotope effect. However, the interfacial monoamidation reaction between carboxy C14‐labeled benzoyl chloride and morpholine gave an isotope effect of 0.950. These results are interpreted, and a mechanism is proposed for the interfacial polycondensation reactions.
Statistische methoden zur ermittlung der verteilung der molekülgrössen in hochpolymeren polymolekularen systemen aus experimentalergebnissen der fraktionierten fällung. II. Mitteilung: Auswertungsmethoden
Authors: Hosemann R. , Schramek W. 
Published: April 2003

AbstractDie messtechnisch bedingte Unkentnis des in polymolekularen Systemen vorkommenden höchsten Polymerisationsgrades Pe bedingt bei der konventionellen Auswertungsmethode nach der sogenannten summierenden Stufenkurve in der Errechnung der Standardabweichung ΔP eine grosse Unsicherheit. Diese Unsicherheit wird abgeschätzt und auf den aus ihr abzuleitenden Fehler in der Polydispersität g hingewiesen. Dieser Fehler wird als “Abbrucheffekt” bezichnet. Er wird in der III. Mitteilung ausführlich behandelt. Dahingegen vermittelt eine halbgraphische Auswertungsmethode nach Funktionstyp bei sachkundiger Anwendung gelegentlich schon Informationen, die auf wenige Prozent genau sein können. Dies wird an dem Beispiel einer realen Fraktionierung erläutert. Schliesslich wird eine neuartige statistische Auswertungsmethode unter Anwendung der Dirac'schen δ‐Funktion beschrieben, bei welcher die hypothesenfreien Informationen des Fraktionierungsexperimentes klar getrennt sind von obigen Unsicherheiten. Dies Methode verwendet ausschliesslich die 2k Informationen des Experimentes und eine wichtige Beziehung über die Natur der Fraktionen. Zur Erläuterung wird das Beispiel der nach der Gleichgewichtstheorie von Schulz vollständig durchgerechneten theoretischen Fraktionierung eines hochpolymeren, polymolekularen Systems mit acht annähernd äquidistanten Fraktionen discutiert.
Thermooxidative degradation of polyesters. A contribution to the study of degradation reactions of some types of linear polyesters
Authors: Gömöry I. , Mlejnek O. , Štímeľ J. 
Published: April 2003

AbstractThis report is part of an extensive investigation on thermal and thermooxidative degradation. The results of an analysis of the products formed during degradation of the glycol esters of phthalic, maleic, adipic and sebacic acids are discussed. The experiments were carried out in an apparatus especially devised for this purpose. The specimens were subjected to heat treatment at 200, 250, and 300°C. in a current of air for periods varying between 4 and 200 hr. The degradation products were selectively trapped and analyzed by classical methods and by paper chromatography. Some of the degradation products were determined quantitatively, others only qualitatively. Among the degradation products of all types of the polyesters studied were found the monomers, formaldehyde, acetaldehyde, formic and acetic acids, carbon dioxide, carbon monoxide, water and compounds of the type of hydroxyaldehydes, hydroxyacids, and aldehydic acids, which were not identified closer. Furthermore, among the degradation products of glycol adipate and glycol sebacate acids and aldehydes were found with three and more carbon atoms to the molecules. Benzoic acid is a specific product of the degradation of glycol phthalate, as well as cyclopentanone of glycol adipate. The qualitative composition of the degradation products changes little with change in temperature and duration of the experiment. The change in quantity with these factors is greater. From the quantitative standpoint the main degradation products are the monomers, carbon dioxide, carbon monoxide and water. A mechanism for the degradation is proposed which includes consecutive reactions (hydrolysis, esterification, and ressterification) leading to the formation of free endgroups and monomers on the one hand, and radical reactions of which the products are mainly oxidized substances of the structural units of the polymer, on the other.
Thermal stability of polydimethylsiloxane. II. Formation of stable complexes on basic active centers
Authors: Kučera M. , Láníková J. 
Published: April 2003

AbstractAmphoteric hydroxides are found to possess a great ability to deactivate the “living” ends of polydimethylsiloxane molecules. They not only prevent depolymerization but also suppress the formation of crosslinks between polymer molecules (which is due to the oxidation of methyl groups). Deactivation of active centers can also be carried out by benzoic acid; however, this acid attacks siloxane bonds at elecated temperatures and promotes decreased molecular weight of polydimethylsiloxane. This undesirable decrease in molecular weight is not caused by benzoic acid only in polymers which originally contained basic active centers; it is found also in polymers without any “living” ends, whether these were removed by transformation into stable complexes or decomposed by heating at 150°C. (as in the case of SiOPBu4).
Elastic moduli of oriented polymers. II. (A1A2)n‐type polymers
Authors: Asahina M. , Enomoto S. 
Published: April 2003

AbstractWe have calculated the elastic moduli for (A1A2)n type polymers. Polyvinyl chloride is a model of a planar zigzag structure for the (A1A2)n type polymer, and the calculated value for E is of the magnitude of 1012 dyne/cm.2. As polyisobutylene, isotactic polypropylene and polyoxymethylene have helical structures, their E values are of the magnitude of 1011 dyne/cm.2. A polymer having a helical structure shows a smaller calculated value of E than that of polymers having planar zigzag structures.
Cyanoethyl and aminopropyl ethers of polyvinyl alcohol
Authors: Alexsandru L. , Opris M. , Ciocǎnel A. 
Published: April 2003

AbstractThe presence of free hydroxyls in polyvinyl alcohol presents a multitude of opportunities for changing the properties of this polymer, a fact which is of considerable theoretical and practical interest. The results are presented of a study of the incorporation of nitrile and amino groups in polyvinyl alcohol. Despite the fact that the cyanoethylation reaction has been described in the literature it is still insufficiently elucidated. The reaction was carried out in an organic medium. The present investigation is concerned with the effect on the extend of cyanoethylation of the chemical nature of the substance used as reaction medium, of the preliminary swelling of the polymer, of the molar ratio of the reactants, and of the reaction time. The relation between the degree of crystallinity of polyvinyl alcohol and its reactivity in the cyanoethylation reaction has been determined. It was found that with growth in crystallinity there is a fall in reactivity and in exent of cyanoethylation. It follows from this that the reaction takes place predominately in amorphous regions. Depending upon the degree of cyanoethylation, polyinyl alcohol changes its structure, being transformed into a rubberlike mass. The solubility of polyvinyl alcohol in water also falls with increasing cyanoethylation. Polyvinyl alcohol with 35–40% cyanoethylated hydroxyl groups is insoluble in water even on heating. On reducing the cyanoethylated Polymer, the polyaminopropyl vinyl ether is obtained.

The effect of the reaction medium, pressure, temperature, concentration, type of catalyst, etc. on the degree of reduction has been investigated. The greatest influence is exerted by the degree of cyanoethylation of the initial polymer. Polyvinyl alcohol having 30–35% of the hydroxyl group sin ether linkage with propanolamine has been synthesized. The polymer is insoluble in water and methanol, is partially soluble in acetone, benzene, and dimethylformamide and has the appearance of a rubbery mass.
Regarding the change of crystallinity and average crystallite size occurring at polycaprolactam filaments by the cold drawing process
Authors: Urbańczyk G. W. 
Published: April 2003

AbstractChanges of crystallinity and average crystallite size which occur in polycaprolactam filaments during the cold drawing process are analyzed. The estimation of fiber crystallinity was carried out by use of the differential‐filtration x‐ray method. The crystallite size was evaluated on the basis of the broadening effect of Debye lines from x‐ray powder‐method diagrams and from the large identity period interferences obtained by small‐angle scattering patterns. The results obtained show that with the change of draw ratio the crystallinity and the average crystallite size also change. The highest values of crystallinity and average crystallite size were found at 375% nominal draw (315% real elongation). The total increase in crystallinity in comparison with the undrawn state of a filament is approximately 27%.
The chemistry of xylylenes. XIV. The moldability and thermal stability of poly(p‐xylylene) and related polymers
Authors: Errede L. A. , Knoll N. 
Published: April 2003

AbstractFreshly prepared α‐poly(p‐xylylene) softens at 220–260°C. and then rehardens as it forms β‐poly(p‐xylylene). Consequently, homogeneous objects can be fabricated at this temperature range by simultaneous application of heat and pressure. This “moldable” poly(p‐xylylene), however, becomes nonmoldable within a week if allowed to age at room temperature. It is speculated that this change in moldability with aging at room temperature may be due to formation of tiny areas of crystalline α‐polymer which serve as seeds for rapid conversion from α‐ to β‐polymer before melt‐flow can occur in the critical temperature range of 220–260°C. of the heating cycle. The shelf life of the moldable polymer is increased considerably, however, by polymerization of the monomer in the presence of a molar equivalent of trialkylphosphines of trialkylphosphites. In vacuum, poly(p‐xylylene) has excellent thermal stability below 400°C., but in air, oxidative degradation is serious even at about 225°C. The moldability of p‐xylylene polymers is improved by copolymerization with a variety of olefinic and inorganic molecules, but the thermal stability, thermal oxidative stability, and sometimes the electrical properties of the resultant product are inferior to those of unmodified poly(p‐xylylene). These polymers appear to be resistant to degradation by γ‐irradiation.
Absolute rates in anionic copolymerization
Authors: Morton Maurice , Ells F. R. 
Published: April 2003

AbstractA study has been carried out to determine the absolute values of the rate constants in the homogeneous anionic copolymerization of butadiene and styrene, initiated by alkyllithium. The approach used was to measure the rate of formation of disappearance of the styryl anion spectrophotometrically, using the absorption peak at 436 mμ. The solutions of butadienyl and styryl anions (in benzene) were prepared by reacting butyllithium with small amounts of butadiene or styrene, in a preliminary step, until the initiation reaction was complete. Subsequently, each of the anionic solutions was mixed with the opposite monomer, and the cross‐propagation reaction measured spectrophotometrically. It was found that the rate of the reaction of the styryl anion with butadiene was extremely rapid, being virtually completed in less than one minute at room temperature. On the other hand, the rate of reaction of the butadienyl anions with styrene was easily measurable at room temperature, being of the same order as the previously measured homopolymerization rates for butadiene. These measurements enabled a calculation of the following reactivity ratios: rB = 3, rS = .06. This very large difference in cross‐propagation rates can easily account for the “anomalour” behavior previously found by several investigators, wherein butadiene polymerized preferentially in a mixture with styrene, and which had been attributed to special “solvation” effects by the butadiene.
Analysis and properties of ethylene–propylene copolymers
Authors: Smith W. E. , Stoffer R. L. , Hannan R. B. 
Published: April 2003

AbstractCopolymers of ethylene and C14‐labeled propylene were prepared with a metal‐oxide catalyst which polymerizes ethylene to a high density polymer. Methyl branches arising from the propylene were counted radiochemically and then related to the infrared absorption of films at 8.7 μ. This band was then used independently to determine methyl branching of a series of ethylene‐propylene copolymers that differed in density and stiffness. Both properties decrease in value with an increase in branching.
Relaxation phenomena in homopolymers and copolymers of ethylene and propylene
Authors: Kontos E. G. , Slichter W. P. 
Published: April 2003

AbstractThe physical properties of ethylene–propylene copolymers depend partly on the overall proportions of the monomers and on the arrangement of the two monomers within the polymer. The effect of composition upon the glass transition and related relaxation is reported, with comparisons drawn from dilatometry, dynamic mechanical loss, and measurements of nuclear magnetic resonance absorption. The relaxation times ranged from about 103 sec. to about 10−7 sec. The copolymers varied in composition from an ethylene: propylene mole ratio of 85:15 to a ratio of 16:84, and the homopolymers were also studied. The relaxation phenomena are interpreted qualitatively in terms of the expected temperature dependence of the spectra of frequencies of molecular motion.
Properties of ethylene–propylene copolymers and of terpolymers containing unsaturation
Authors: Natta G. , Crespi G. 
Published: April 2003

AbstractThe elastomeric properties of amorphous ethylene–α‐olefin copolymers have been described in previous papers, as well as the importance of both the homogeneity of composition of each macromolecule forming the raw polymer and the statistical distribution of the two comonomers. It has been observed that a narrow distribution of the molecular weights is very important with regard to the mechanical properties of the cured synthetic rubbers obtained from the ethylene–propylene copolymers, whereas a not too high average molecular weight is important as far as the processability is concerned. One of the most interesting properties of the ethylene–propylene copolymers is their good aging resistance which is due to the saturated nature of the polymeric macromolecules. It has been observed that these properties are substantially shown also by those terpolymers consisting predominantly of ethylene and propylene (or other α‐olefins), and in addition a small amount of a monomer whose molecule contains more than one double bond; on polymerization these last monomers yield monomeric units still containing a double bond. A great number of monomers are well suited for the production of terpolymers with a low degree of unsaturation, which is sufficient for the conventional vulcanization methods adopted for other rubbers, particularly for those containing a low degree of unsaturation. It is quite essential, in order to obtain good vulcanizable products, that the unsaturation is regularly distributed in all the macromolecules, and that in each of these they are distributed at random. Probably, the differences observed with various monomers depend primarily on the ability of each monomer and of the copolymerization system adopted to meet to these requirements. This is the reason why we shall discuss the properties of those products in which a considerable homogeneity of distribution has been achieved. The mechanical and dynamic properties will be related to the degree of unsaturation. The results obtained from the use of such terpolymers for the production of elastomers have demonstrated that the elastic, dynamic, and aging properties remain essentially the same as those for the ethylene–propylene copolymers when the degree of unsaturation does not exceed 2–3%, expressed as number of double bonds per hundred monomeric units.
Studies on grafting glycidyl methacrylate on polyvinyl chloride backbones
Authors: Ravve A. , Khamis J. T. 
Published: April 2003

AbstractGraft copolymers of glycidyl methacrylate on polyvinyl chloride backbones were prepared by the free radical technique. Three types of backbones were used: (1) vinyl chloride homopolymer; (2) copolymer of vinyl chloride–vinyl acetate, 87:13; (3) copolymer of vinyl chloride–vinylidene chloride, 89:11. The grafting reactions resulted in products with lower intrinsic viscosities than the unreacted backbones. The graft copolymers were fractionated with the separation of glycidyl methacrylate homopolymers from the rest of the graft products. Unreacted backbones were separated through gelation of all the epirane‐bearing chains. Structure proof was conducted by chemical cleavage of the grafted side chains by reduction with LiAlH4 and through acid hydrolysis.
The hypochlorite oxidation of polyvinylacetophenone
Authors: Merrill Stewart H. 
Published: April 2003

AbstractPolyvinylacetophenone can be oxidized by a special two‐step technique to poly(vinylbenzoic acid). The product is soluble in alkali and in many common organic solvents. Analytical studies on the product indicate that extra oxygenated functions and some scission occur along the chain. An explanation is offered for the crosslinking reaction which occurs when strong alkalinity is not maintained during the oxidation. A portion of the carboxyl groups can be converted to acid chloride for preparation of derivatives.
The role of symmetry in crystallization and polymerization phenomena
Authors: Ham George E. 
Published: April 2003

AbstractCrystallization mechanisms are interpreted as processes in superimposition of molecules from random positioning in space. It is shown that at the melting point there are substantial restrictions on the number of configurations (i.e., ordering) available to molecules, and that this preordering is an important factor in crystallization, influencing melting point, entropy of fusion, and heat of fusion. The interpretation of the melting behavior of nylon 6, nylon 66, polypropylene, and linear polyethylene proceeds from these considerations. The polynuclear hydrocarbons are also considered in detail as prototypes for preordering effects in the melt.
Electron spin resonance studies of irradiated acrylamide and methacrylamide
Authors: Ueda Hisashi , Kuri Zenichiro 
Published: April 2003

AbstractElectron spin resonance spectra of the irradiated monomers and polymers of both acrylamide and methacrylamide were studied. On thermal treatment, the spectra are changed both in their patterns and in intensity. The polymerization yield of these monomers after irradiation followed by the same thermal treatment as with that used for ESR samples was also studied. The radicals existing in the irradiated acrylamide are concluded to be a mixture of two kinds of radicals, one at the ends and the other in the middle of the polymer chain.
Investigation of the protective ultraviolet absorbers in a space environment. II. Photochemical studies
Authors: Schmitt Richard G. , Hirt Robert C. 
Published: April 2003

AbstractCompounds which are effective in protecting materials from terrestrial ultraviolet radiation may, in the high vacuum of space, suffer loss both by evaporation and by photochemical degradation. The photochemical stability of the protective ultraviolet absorbers has been studied under extraterrestrial and terrestrial conditions using an AH‐6 high‐pressure mercury are to simulate sunlight above the earth's atmosphere. It was determined that the ultraviolet absorbers are considerably less stable in a space environment and that the loss in stability is due primarily to a higher quantum yield for the short wavelength ultraviolet radiation (below 3000 A.).
Proposed structures and models for polymers crystallized in bulk
Authors: Gruenwald G. 
Published: April 2003

AbstractSince many publications have been concerned with polymers which have been crystalized in single crystals where chain‐folding represents the only way for explaining the arrangement of the long chain molecules, there are appearing increasingly more publications referring to chain‐folding also on polymers crystallized in bulk. Assuming that a polymer molecule is randomly coiled whether in solution or in bulk where actually sister molecules represent the “solvent,” then on crystallization of polymers in bulk, like chain sections will aggregate whether belonging to the same molecule or to a nearby sister molecule. In the latter case, regular chain‐folding should be very unlikely to occur. Using woolen yarn as a model substance which simulates both covalent and van der Waals binding forces (the latter by means of the fuzzy fibers), it is illustrated how bulk crystallization may be nicely imitated by parallel combing of randomly arranged yarn. This concept is also applied to explain changes in long‐period as occurring on annealing and the formation of macrostructures, mainly spherulites.
Theories for the flow of dilute solutions of polymers and of nondiluted liquid polymers
Authors: Pao Yoh‐Han 
Published: April 2003

AbstractThe formulation of two theories for the flow of polymeric systems and some of the principal results are presented in this paper. The theory for the flow properties of dilute solutions of polymers is related to the work of Kirkwood and Riseman, and Rouse, Bueche, and Zimm. The combined effects of long‐range excluded volume, hydrodynamic shielding and branching are considered in computations for intrinsic viscosity. The dependencies of solution viscosity on velocity gradient and frequency of oscillation are derived. The continuum theory is adequate for describing the combined effects of finite deformation and viscoelastic flow of molten polymers.
Study of the treatment of polymer fractionation data
Authors: Tung L. H. 
Published: April 2003

AbstractThe fractionations of a hypothetical 250‐component system and an actual polymer were simulated by computations on a digital computer. The results indicated that Schulz's method of treating polymer fractionation data is acceptable if the fractions obtained are reasonably sharp. When extremely low molecular weight materials are present in the polymer, the computation shows that one must be very careful in computing the M̄u/M̄n ratio. A comparison of the computation result with the experimental result of a linear polyethylene fractionation indicates that the Flory‐Huggins' theory describes the liquid‐liquid phase separation of polymer solutions well.