bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of irradiation and rolling on the tensile behavior of polyethylene
Authors: Tsunekawa Yoshinori , Oyane Moriya , Kojima Kohei
Published: April 2003

Tensile properties of low‐pressure polyethylene subjected to both irradiation and rolling have been studied. Co60 was used as the γ‐ray source. The anisotropic properties induced by rolling and irradiation were measured by testing the tensile behavior of specimens cut at 0°, 45°, and 90° to the direction of rolling. The yield strengths of specimens cut parallel to the direction of rolling increased with increasing reduction in thickness, but the yield strengths of those cut at 45° and 90° were scarcely affected. The yield strengths of specimens that were irradiated, or irradiated and rolled, increased doses, and then decreased with increasing irradiation, regardless of whether the specimens were irradiated after rolling or rolled after irradiation. The final elongations of the specimens that were irradiated after rolling and cut parallel to the direction of rolling decreased slowly with increasing irradiation, but those of the specimens cut at right angles to the direction of rolling decreased very rapidly. In contrast, the final elongations of all specimens that were rolled after irradiation decreased very slowly regardless of the cutting direction. It may be concluded from the experimental results that the tensile properties of polyethylene irradiated after rolling are more anisotropic than those of the polyethylene rolled after irradiation.
Formation of carboxyl endgroups in polymers and their detection by the dye partition test
Authors: Palit Santi R. , Mukherjee Barunanda N. , Konar Ranjit Singh
Published: April 2003

Carboxyl groups or endgroups have been introduced into polymers by use of the following four general methods: (1) use of a carboxyl‐bearing initiator, (2) copolymerization with a carboxyl‐bearing monomer, (3) chain transfer with a molecule containing an actual or potential COOH group, and (4) transformation of a reactive group already present in the polymer. The presence of the carboxyl endgroup in the polymer has been tested for a new technique called the “dye partition test,” developed in this laboratory. It has been demonstrated that all these methods can be used successfully to incorporate COOH groups in the polymer. Of particular interest is the fact that the incorporation of solvent fragments in polymers by chain transfer can be demonstrated very simply and conveniently by this method.
Differential thermal analysis of high polymers. II. Effects of diluents on melting behavior of polyethylenes
Authors: Ke Bacon
Published: April 2003

Studies of the nature and magnitude of the interaction between a polymer and a diluent are of both theoretical and practical importance. The effects of several liquid and solid diluents on the melting behavior of both high‐ and low‐density polyethylene have been studied by differential thermal analysis. The depression of melting point was related by a thermodynamic equation to the type and amount of the diluent. The thermodynamically derived true heat of fusion of polyethylene agrees well with the currently accepted value.
Crosslinking of copolymers of N‐methylolacrylamide and ethyl acrylate induced by heat treatment
Authors: Kamogawa Hiroyoshi , Sekiya Toshii
Published: April 2003

The effects of crosslinking by N‐methylolacrylamide in emulsion copolymers with ethyl acrylate under heat treatment in acid medium was investigated, and various methods for calculating the effective density of crosslinking were compared. It was found that stress‐strain relationships of copolymer films showed marked dependence both on the temperature of cure and on the methylolamide group content of the polymer; these dependences can be attributed to the formation of crosslinkages between polymer chains. The effective densities of crosslinking (ρ) of the cured copolymer films were calculated according to three methods: (1) stress‐strain measurement in dry state (ρe); (2) stress‐strain measurement in acetone (ρe′); (3) measurement of the degree of swelling in acetone (sρe). Values of ρe must be corrected with values for polymer with an infinite degree of swelling by use of the empirical equation of Mooney and Rivlin, in order to eliminate such steric factors as polymer chain entanglements; this method was found to be the most rational of the three, since ρe′ and sρe had their respective faults. The effective densities of crosslinking were found to be proportional to the squares of the methylolamide contents of the polymers, and there was a linear relationship with −5/3 slope between the logarithms of the stress and the degree of swelling, satisfying the theoretical expression.
The fractionation and molecular weight distribution of polypropylene
Authors: Davis Thomas E. , Tobias Robert L.
Published: April 2003

The application of the sand columm extraction, fractional coacervation, and coacervate extraction methods to the molecular weight fractionation of polypropylene is described. Extremely reproducible results are given by the sand column method, and ten fractions taken by this method are adequate for characterization of the usual polypropylene distribution. The variation between the molecular weight distributions derived from six fractionations of a test polypropylene by the three methods was small and indicates that fraction polydispersity probably contributes negligibly to any deviation of the experimental distributions from the true distribution. Polypropylenes made with aluminum triethyl‐transition metal trichloride catalysts contain relatively large amounts of low molecular weight polymer and have broad distributions similar to that of low‐pressure polyethylene. All such polypropylene samples had distributions which were described well by a logarithmic normal equation with a constant standard deviation. The distribution was not altered when the aluminum triethyl in the catalysts was replaced by aluminum triisobutyl. Catalysts containing vanadium as the transition metal, however, produced polypropylenes with distributions distinctively different from those made with titanium trichloride.
Gas and free radical measurements in irradiated polyvinyl chloride
Authors: Loy B. R.
Published: April 2003

Simultaneous gas and electron‐spin resonance measurements of HCl evolution and free radical decay in irradiated PVC support Atchison's conclusion that three species of radicals are trapped. In accordance with first‐order rates, each radical decays to yield a different but constant ratio of [HCl] to [R.] over its respective reaction period. Optical measurements indicate that each species yield a constant distribution of conjugated chain lengths. An explanation is offered whereby the dehydrochlorination process is restricted to isolated radical‐pair systems. By this mechanism the average chain lengths are 26, 51, and 126 units for the short‐, medium‐ and long‐lived radicals, respectively.
High polymer chelates. I. Structure and stability of polymethacroylacetone chelates
Authors: Teyssié M. T. , Teyssié P.
Published: April 2003

The chelates formed by polymethacroylactone (PMA) with several divalent cations were studied by spectrophotometric and potentiometric methods, and their behavior was compared to that of chelates formed by a low molecular weight diketone of similar structure, pivaloylacetone. The structure of the chelates formed by both types of diketones is identical, as indicated by the elementary analyses as well as the absorption spectra in crystalline state and in solution (these spectra are further indicative of resonance phenomena and orbital distribution in the chelate rings). The stability of these chelates was also investigated. A calculation based on the usual two‐step chelation process seems to indicate a higher stability of the high polymeric chelates over the low molecular weight ones, but the values of the constants become identical when taking in account the specific structure of the polymeric ligand: the metal ion, when fixed on a diketo group of the chain, is practically always in the nearest vicinity of a second chelating group, reacting immediately with it to form the chelate species MA2. The process will accordingly be dependent on the molar concentrations in the ligand only for the first step, but not for the second one as for monofunctional diketones. Finally, a linear relationship was found between the logarithms of the stability constants of the various chelates and the electronegativities of the corresponding metals. The behavior of both types of diketones is again identical. On the basis of this parallel in the behavior of low and high molecular weigh ligands of similar structure, a method is proposed to predict the selectivity of synthetic selective ion exchangers, and its validity is confirmed by absorption experiments in aqueous media.
The use of high‐energy irradiation in an investigation of the mechanism and kinetics of emulsion polymerization
Authors: Vanderhoff J. W. , Bradford E. B. , Tarkowski H. L. , Wilkinson B. W.
Published: April 2003

The emulsion polymerization of styrene initiated by γ‐rays was studied using competitive particle growth and conventional techniques. With γ‐rays, the rate of free‐radical generation is independent of temperature, and the absorption of energy is uniform throughout the system. From the competitive growth experiments, the particle growth rates were similar to those of persulfate ion‐initiated systems and quite different from those of benzoyl peroxide‐initiated systems. From the conventional experiments, the number of particles increased approximately as the square of the emulsifier concentration for both γ‐ray and persulfate ion‐initiated polymerizations. With γ‐rays, the number of particles decreased with increasing temperature; the opposite was observed for persulfate. This may be explained by the relative rates of free‐radical generation of each system; for γ‐rays this rate is independent of temperature, while for persulfate, the activation energy for initiator decomposition is greater than that for polymerization propagation. For the γ‐ray system, the calculated values of kp increased with increasing particle size; the activation energy was 7.2 (σ = 0.59) kcal./mole. The calculated values of kt at 50°C. were 104–105 l./mole/sec.
Crosslinking efficiency in the reaction of dicumyl peroxide with dimethyloctadiene
Authors: Parks C. R. , Lorenz O.
Published: April 2003

The crosslinking efficiency of dicumyl peroxide was investigated with the use of 2,6‐dimethyl‐2,6‐octadiene as a model polyisoprene. High‐temperature gas chromatography was used to determine quantitatively the amount of crosslinked products as well as the decomposition products of the peroxide, α,α‐dimethylbenzyl alcohol and acetophenone. The crosslinked products were found to be almost exclusively a mixture of isomeric dimers when the molar ratio of dimethyloctadiene to dicumyl peroxide was 40:1 or higher. When larger amounts of peroxide were used, higher molecular weight crosslinked products were also formed. The dimethylbenzyl alcohol and acetophenone formed accounted for 90–95% of the peroxide decomposed. The results are consistent with a mechanism according to which the radicals formed by decomposition of the peroxide react exclusively with polyisoprenes by hydrogen abstraction. The polyisoprenyl radicals formed are then used up exclusively by combination. One molecule of decomposed dicumyl peroxide should then form one crosslink, and this was confirmed by experiment. Kinetic data showed that the crosslinking reaction followed a first‐order law. The activation energy was found to be 32 kcal./mole.
The crosslinking efficiency of some vulcanizing agents in natural rubber
Authors: Lorenz O. , Parks C. R.
Published: April 2003

The crosslinking efficiencies of several curing agents have been determined from swelling measurements. The results indicate that dicumyl peroxide is a quantitative crosslinking agent for natural rubber, as was previously found to be true of dimethyloctadiene. As one molecule of dicumyl peroxide is able to form one crosslink, 3.2 to 4.0 molecules of tetramethylthiuram disulfide or 9–10 sulfur atoms in a sulfur‐sulfeneamide system are needed for the same purpose. A comparison is made between the number of chemically introduced crosslinks and a corresponding value obtained from swelling measurements with the help of the Flory‐Rehner equation. It was found that a filler can effect the properties of a vulcanizate through a filler‐curing agent interaction as well as through a filler‐rubber interaction. When a filler‐curing agent interaction takes place, a certain amount of curing agent or accelerator becomes unavailable for cure. This lowers the number of crosslinks introduced by the curing agent. If the filler‐curing agent interaction is insignificant and can be neglected, the swelling value Q for a filled stock can be related to that of an unfilled, analogous gum vulcanizate, Qgum, by the simple equation Q = kQgum; k is a function of the nature and amount of the filler and the elastomer, but is independent of the curing agent.
Electron spin resonance studies of the radicals produced in high polymers by γ‐irradiation and their reaction with sulfur dioxide
Authors: Kuri Zenichiro , Ueda Hisashi
Published: April 2003

Reactivities of free radicals formed in irradiated polymers were investigated. Procedures utilizing the electron spin resonance technique showed the behavior of free radicals with sulfur dioxide. Radicals from polymers containing an intramolecular having hydrogen bond in themselves, such as cellulose, starch, polyvinyl alcohol, etc., showed no reactivity following either irradiation in a sulfur dioxide atmosphere or irradiation in vacuo with subsequent introduction of sulfur dioxide. Other polymer radicals were classified into three groups according to the effects of sulfur dioxide on them.
Flow of gases through polyethylene
Authors: Michaels Alan S. , Bixler Harris J.
Published: April 2003

Diffusion and permeability constants for twelve permanent gases have been measured in a linear and a branched polyethylene, hydrogenated polybutadiene, and natural rubber over the temperature range 5–55°C. The Barrer time lag apparatus has been used in these determinations. For all gas–polymer pairs investigated, a linear plot of the logarithm of the diffusion or permeability constants versus the reciprocal absolute temperature is observed, indicating activated diffusion is occurring. Arguments have been presented supporting the hypothesis that natural rubber is a completely amorphous analog of polyethylene with respect to the diffusion process. It has been possible, as a result, to quantitatively express the reduction in diffusion constants in going from natural rubber to hydrogenated polybutadiene (29% crystalline), to the branched polyethylene (43% crystalline), and to the linear polyethylene (77% crystalline). These reductions were strongly dependent on gas molecular size, increasing as the molecular size increases. A geometric impedance factor and a chain immobilization factor have been introduced to account for the effect of crystallinity. The former is assumed to be independent of molecular size and accounts for the necessity of the diffusing molecule to by‐pass crystallites which have been shown to be impenetrable. The latter size‐dependent factor reflects the reduction in amorphous chain segment mobility brought about through the proximity of crystallites. Analysis of the geometric impedance factor supports the existence of thin, highly anisometric sheets of crystalline polymer in polyethylene. The anisometry of the crystallites was observed to increase with increasing crystallinity consistent with the chain folding mechanism for crystal growth in polyethylene. Nucleation and growth kinetics also qualitatively accounted for the variation in crystal anisometry observed in polymers prepared by different methods of polymerization. The apparent activation energies for diffusion determined in polyethylene include not only the energy required for chain segment separation but also the effect of thermal expansion and crystalline melting. Correlations have been presented which permit the estimation of gas diffusion constants in a wide variety of polyethylenes.
Studies of the ethylenediamine–cellulose complex. III. Some factors in the formation of the complex
Authors: Segal Leon , Creely J. J.
Published: April 2003

Complete conversion of the cellulose crystal lattice to that of the ethylenediamine‐cellulose complex can be attained with aqueous ethylenediamine solutions of 60% and greater. Cellulose in the form of loose cotton yarn or woven fabric immersed in 98% ethylenediamine solution for as little as 1 minute is as completely complexed as that immersed 4 hours. Removal of ethylenediamine in excess to that required by the diamine‐cellulose complex is accomplished as effectively by hexane extraction as by evaporation under reduced pressure (8 mm. Hg at 95–100°C.). Using the latter procedure, a period of 2 hr. is sufficient to reduce the diamine content to that which has been obtained after longer periods, i.e., about 20%. The x‐ray diffractograms of the complexes prepared from celluloses I, II, and III suggest that the starting material influences the interplanar spacings of the crystal lattice of the complex. They also show that water‐extraction of the complex prepared from cellulose II restored the cellulose II lattice, while cellulose I is obtained when cellulose III is used. The infrared absorption spectra of the complexes prepared from celluloses II and III are similar and show slight differences from that of the cellulose I complex. After water extraction of the diamine, the spectrum of the material from the cellulose III complex closely resembles that of the cellulose I material.
Optically active polymers. I. Polymerization of 4‐methyl‐7‐isopropyl‐2‐oxohexamethyleneimine
Authors: Imoto Minoru , Sakurai Hideki , Kono Tadao
Published: April 2003

Polymerization of 4‐methyl‐7‐isopropyl‐2‐oxohexamethylèneimine (I) initiated by K ou Li was carried out at 150°C. in the presence of benzoyl chloride or the N‐benzoyl derivative of I (II). The yield of the polymer was 11–25% over the course of 8–70 hr. The values of [η] in formic acid were 0.047–0.075. Optical activities of I, II, the polymers and the open chain monomer (III) were measured in formic acid.
The nature of acid‐sensitive linkages in cellulose
Authors: Michie R. I. C. , Sharples A. , Walter A. A.
Published: April 2003

Experiments with s:tmples of cellulose regenerated in various ways confirm the earlier observation that their initially high rate of acidic hydrolysis under heterogeneous conditions is considerably greater than that calculated for the normal glucosidic bonds. The presence of such weak bonds appears to be a general phenomenon, and the process by which they are formed does not seem to be associated with any specific chemical reaction. It is thus suggested that the enhanced rate a t which these bonds degrade may be a physical effect, resulting either from strains set up in the chain molecules in the amorphous regions or from local variations in the normal state of hydrogen bonding.
On the acetalization of regenerated cellulose with dialdehydes
Authors: Fujimura Toshikazu , Okamoto Shin'Ichi
Published: April 2003

The effects of acetalization with the divalent aldehydes glyoxal and glutaraldehyde on rayon staples of various structures were studied. The swelling in aqueous 25% sodium hydroxide was measured after centrifuging. The knot strength was taken as a measure of the fiber brittleness. The acetalized glyoxal was determined by Head's method, and the amount of glutaraldehyde liberated by hydrolysis of the acetalized fiber with acid was determined polarographically. The results were as follows: (1) The amounts of acetalized glyoxal formed increased with increasing steeping liquor concentration, curing temperature, and curing time, but the percentage of glyoxal reacted did not exceed 65% of that applied. (2) For a constant amount of aldehyde applied to the fibers, more acetalized glyoxal was obtained (a) with lower moisture in the fiber after predrying, (b) by treatment with a higher concentration of aldehyde in a single step rather than at lower concentrations in many steps, and (c) with lower pickup at higher concentration. Therefore, the aldehyde concentration in the fiber at the final stage of curing may determine the acetalization reaction equilibrium. (3) The amounts of free and semiacetals formed increased initially and then decreased with higher total amounts of acetalized glyoxal. (4) The fine structure of all‐skin rayon may be favorable to the reduction of water imbibition and also to the prevention of brittleness at the same degree of acetalization. (5) Glutaraldehyde was more reactive than glyoxal and more favorable to prevention of brittleness in the fiber. (6) Super rayon crosslinked with glutaraldehyde had relatively high strength, including knot strength, and resistance to alkali, so that blending it with cotton, which benefits from mercerization, is a possibility.
The cellulose–butadiene diepoxide reaction and its effect on the crease resistance of cotton
Authors: McKelvey John B. , Benerito Ruth R. , Webre Beverly G. , Berni Ralph J.
Published: April 2003

Butadiene diepoxide (BDE), the meso‐1,2,3,4‐diepoxybutane, may be added to cotton cellulose with a variety of catalysts and conditions at room temperature. A slow addition of BDE from nonpolar solvents to yarns pretreated with alkali resulted in weight gains which were proportional to the activity of hydroxyl ions used in pretreatment. For a given hydroxyl ion activity, percentage weight gains of BDE varied directly with time of reaction. Add‐on of BDE has been shown to be proportional to the product of hydrolyzed BDE and molarity of the hydroxyl ion in the dilute alkali. It has been shown that slow addition of epoxide from carbon tetrachloride solution to cotton fabric impregnated with dilute alkali, natural salts, or alkaline salt solutions produces a fabric of good dry and wet crease recovery. Rapid addition of epoxide to fabric by the use of more concentrated alkali or elevated temperature showed excellent wet, but no dry, crease recovery. Hydrogen ion catalysis of the BDE–cotton reaction is very slow and, in the case of acetic acid, is without effect. With sulfuric acid, only mediocre wet crease recovery is produced a t room temperature. Catalysis with zinc fluoborate, methanolic solutions of BDE, and curing temperatures of 75–125° resulted in excellent wet and dry crease resistance a t weight gains of less than 2%. All methods of BDE addition to cotton fabric that produce good dry crease recovery cause a lowering of tearing and breaking strengths. There is little change in tensile properties when only wet. crease resistance is imparted. This suggests that profound physical changes in the fine structure of cellulose result from mild chemical action with a water‐soluble diepoxide. Recovery from deformation of cotton fibers in the wet and dry states (crease recovery) has been attributed to intermolecular covalent crosslinking of anhydroglucose unit hydroxyls by the diepoxide and, in particular, to crosslinking of hydroxyls on carbons 2 or 6, with a resultant diminution of interchain slippage. Fibers that exhibit only wet crease recovery are believed to have a minimum of covalent crosslinks and to be hydroxy cellulose monoethers of the epoxide or graft polymers of the same, which prevent slippage of chains only when wet and swollen (possibly by entanglement).
Crystallization of cellulose and cellulose derivatives from dilute solution. I. Growth of single crystals
Authors: Rånby B. G. , Noe R. W.
Published: April 2003

Cellulose triacetate and triethyl cellulose have been crystallized from dilute solution into regular compact lamellar crystals of microscopic size (10–20 μ) and of the same type as the single crystals previously obtained from linear synthetic polymers The shape of the cellulose acetate crystals (pyramids with square base) conforms with the crystal lattice of cellulose triacetate II (pseudo‐orthorhombic unit cell) when the chains are at right angle to the base planes. Compact platelike crystals of pure cellulose containing the lattice of cellulose II (mercerized cellulose) have been prepared from aqueous solutions by slow saponification of water‐soluble cellulose acetates. At 90°C. the crystals can be grown to a regular diamond (lozenge) shape (15 × 30 μ in cross section) with a lattice order as good as or better than that of purified dried native cotton fiber or bacterial cellulose. The shape of the crystals conforms with the crystal lattice of cellulose II (monoclinic unit cell with the angle 60°) if the chains are a t right angle to the base planes. It is concluded that the crystals of cellulose and cellulose derivatives are single crystals of a structure analogous to that of synthetic polymers. This would require chain folding also for the cellulose molecules. From studies of molecular models of cellulose chains, a 180° fold is considered possible with about four glucose residues‐provided the consecutive units are rotated around the glycosidic bonds.
Crosslinking of cellulosics by high energy radiation. II
Authors: Leavitt Frederick C.
Published: April 2003

Nonionic water‐soluble cellulose ethers have been crosslinked by irradiation with high energy electrons in aqueous solution. This unexpected behavior of cellulosics toward radiation is reproducible. Crosslinking and chain scission are competitive reactions; nevertheless, conditions are described for obtaining one or the other as the predominant reaction. It is proposed that the mechanism is free radical in nature. High beta radiation dose rates (Van de Graaff generator) are necessary to crosslink substantial amounts of polymer. Low dose rates, such as usually administered with gamma radiation, fail to yield crosslinked products. Degradation, oxidation, and cleavage of substituent groups occur over a wide range of radiation dose rates. The viscosity of the medium also plays a major role in determining whether crosslinking will take place. Highly viscous solutions with limited freedom of chain motion are degraded until the viscosity is sufficiently low to allow free bimolecular coupling reactions; then a gelled system forms immediately. Carboxylated cellulosics have not been crosslinked by this method. Samples examined were degraded at all levels of radiation. The crosslinked cellulose derivatives included methyl cellulose, hydroxyethyl cellulose, methyl hydroxypropyl cellulose, and methyl hydroxybutyl cellulose.
Grafting onto cellulosic macromolecules through chain transfer to mercaptoethyl side chains. II. Mechanism of the process
Authors: Chaudhuri D. K. Ray , Hermans J. J.
Published: April 2003

The data that were presented in Part I are compared with theory. It is found that the weight increase of a mercaptoethylated cellulose acetate film during polymerization of styrene in the presence of this film is proportional to the initial monomer content and to 1 − exp {−bt} where t is the time and b a constant proportional to (catalyst concentration)1/2 times (initiation efficiency)1/2. This equation is in accordance with the theory of grafting developed by Fox and co‐workers, when the monomer conversion is low, but it is found experimentally that its validity extends well beyond values of the monomer conversion for which the equation should no longer represent a good approximation. (1) The composition of the film and therefore the monomer concentration and the rate constants change during grafting. (2) When grafting is high it becomes impossible quantitatively to remove the homopolymer by extraction of the film. (3) Chain transfer takes place not only to SH groups but also to nonmercaptoethylated parts of the cellulose acetate, It is believed that three causes are responsible for this result.
Peroxidation of isotactic polybutene
Authors: Beati E. , Severini F. , Toffano S.
Published: April 2003

The reaction of direct peroxidation at 75–90°C. and the simultaneous or successive ones of degradation of the isotactic poly‐α‐olefins are followed through analytical measurements of the total peroxide oxygen content (dialkyl peroxides + alkyl hydroperoxides) and intrinsic viscosity measurements. The results obtained from the autocatalytic oxidation and those from operating in the presence of a volatile initiator (tert‐butyl hydroperoxide), either containing labelled carbon or not, are described and compared.
Isotactic trans‐1,4 polymers of 1,3‐pentadiene
Authors: Natta G. , Porri L. , Corradini P. , Zanini G. , Ciampelli F.
Published: April 2003

Crystalline polymers of 1,3‐pentadiene, which are composed of trans‐1,4 units and show an isotactic configuration of the tertiary carbon atoms, have been obtained with the use of the heterogeneous Al(C2H5)3VCl3 catalytic system. The cis or trans isomer of pentadiene yields polymers that are more stereoregular than those obtained from mixtures of the two isomers. Isotactic trans‐1,4‐poIypentadiene may exist in two modifications: crystalline and paracrystalline (unidimensionally regular). The two modifications are characterized by different x‐ray spectra and different densities. trans‐1,4 Isotactic polypentadienes contain tertiary carbon atoms which are actually asymmetric. This permitted obtaining optically active polypentadienes by using polymerization catalysts prepared from optically active aluminum trialkyls.
cis‐Tactic polybutadiene: Solubility, [η]–M relations in different solvents, and molecular conformation
Authors: Danusso Ferdinando , Moraglio Giovanni , Gianotti Giuseppe
Published: April 2003

Several samples of cis‐tactic polybutadiene prepared by stereospecific catalysis and having a cis unit content of about 98%, were fractionated by fractional precipitation techniques. Some of the central fractions obtained were examined by viscometric, osmotic, and sedimentation methods in dilute solution. [η]–M relations were determined for benzene and toluene at 30°, and for isobutyl acetate at 20.5°C., the latter solvent being at ϑ conditions. Configurational parameters of unperturbed molecules and interaction affinity in good solvent were calculated and are compared with those of known hydrocarbon polymers.
Structure of isotactic polyaldehydes
Authors: Natta G. , Corradini P. , Bassi I. W.
Published: April 2003

The crystalline polymers having a polyacetalic chemical structure, as obtained by us by polymerization at low temperature of aldehydes in the presence of stereospecific catalysts formed by metalloorganic compounds, show an isotactic structure. The chain conformations of different isotactic polyaldehydes are discussed, and in particular the crystalline structures of polyacetaldehyde, of poly‐n‐butyraldehyde and of polypropionaldehyde are described. The polymeric chains of these polyaldehydes have a fourfold helix conformation with a repetition period of 4.8 A., and the packing of the macromolecules corresponds to that of the tetragonal I41/a space group. Around each fourfold screw axis present in the unit cell, isomorphous anticlined macromolecules can statistically vicariate.
Morphology of dendritic polyethylene crystals
Authors: Geil P. H. , Reneker D. H.
Published: April 2003

The dendritic crystals of polyethylene described in this paper illustrate many details of the morphology of polyethylene crystals including the development of spiral growths, delineation of fold domains, the attachments between adjacent lamellae, and fracture behavior of single lamellae. Definitions of terms useful in the description of lamellar crystals of polymer molecules are also given.
The synthesis of silico‐organic polymers on the complex catalyst (C2H5)3Al+TiCl4
Authors: Nametkin N. S. , Topchiev A. V. , Durgar'Yan S. G.
Published: April 2003

Organosilicon polymers with silico‐carbon units in the main chain are of considerable interest. The initial monomers for the synthesis of the polymers may be alkenylsilanes. In the present work it is shown that polymerization of alkenylsilanes may take place on a complex (C2H5)3AlTiCl4 catalyst. The polymerization was carried out at 50–70°C. with n‐heptane as solvent. The effect of the triethylaluminum:titanium tetrachloride ratio on the yield and properties of the polymers obtained was also investigated. Highest yields were obtained at (C2H5)3Al:TiCl4 molar ratios of 1:2, 1:3, and 1:4. Both crystalline and liquid polymers are formed. On polymerization of methylphenyldiallylsilane about 30% solid polymer is produced. The isotactic portion of this solid polymer (after extraction with ether) has a melting point of 400–410°C. The copolymerization of dimethylphenyldiallysilane and methylphenyldiallylsilane with propylene in the liquid phase was also studied. A number of physicochemical properties of the polymers were investigated.
Polymers containing germanium
Authors: Kolesnikov H. S. , Davydova S. L. , Klimentova N. V.
Published: April 2003

Methacrylyltriethylgermanium was synthesized and shown to be capable of polymerization and of copolymerization with other unsaturated compounds. The polymers and copolymers were studied in order to determine the effect of incorporation of the tri‐alkylgermanium group R3Ge on properties of the polymers.
Polymerization reactions on insoluble molecularly disperse substances
Authors: Kargin V. A. , Kabanov V. A.
Published: April 2003

Atomic and molecular dispersions of inorganic solids in monomer media has been found capable of giving rise to highly active polymerization centers effective at low tempera‐ tures It was shown, using BeCl ZnClz, LiC1, TiC1, and RloOj, that salts and oxides which in the form of perfect crystals are not polymerization catalysts, in the molecular disperse state or with highly defective structures may cause the polymerization of a number of monomers (styrene, a‐methylstyrene, isoprene) at their melting points. A study was made of the initiating capacity of some metals in molecular mixtures with monomers. It was shown that with suchamixtures of Mg and acrylonitrile, methyl methacrylate, or methyl acrylate rapid low‐temperature polymerization in the solid state takes place. The polymerization is induced by radicals formed on reaction of Mg with the monomers. Similar conversions may occur in the presence of other metals (Hg, Zn, Cd). The methyl methacrylate produced in this way was found to have an isotactic structure. Hence the part played by preliminary ordering of the monomer on the formation of the polymer microstructure has been demonstrated. Studies with the crystalline salts of acrylic and methacrylic acids show that it is possible to initiate poly‐ merization in the solid phase by the formation of defective crystal structures in the system. This may be arcomplished by heterogeneous chemical reactions and intensive mechanical dispersion of the solid monomers.
Radical decomposition of various peranhydrides and peresters
Authors: Razuvaev G. A. , Terman L. M. , Likhterov V. R. , Etlis V. S.
Published: April 2003

We have studied the kinetics and the products of the thermal degradation of acetylcyclohexylsulfonyl (I), dibenzyl (II) and dicyclohexyl peroxide carbonate (III) in various solvents. The kinetic data show that the degradation is first‐order with respect to the peroxide. The activation energies for the reaction in benzene, isopropyl alcohol and carbon tetrachloride have been calculated. It is suggested that the primary process is decomposition of the peroxide to free radicals according to the scheme:
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In solvents which easily give up hydrogen, such as isopropyl alcohol, hydrogen is removed with the formation of sulfonic acids from I and the corresponding alcohols from II and III:
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In benzene and carbon tetrachloride the ensuing free radicals disproportionate, forming chiefly unsaturated sulfonic acids on degradation of I, and carbonyl compounds and alcohol on degradation of II and III.
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It should be mentioned that no products of interaction with the solvent were found on degradation of peroxydicarbonates in benzene. In the degradation of (I), a resin was isolated, of which the nature was determined by decomposition in C14‐labeled benzene. Also in the degradation of I, methyl sulfonate was detected in amounts which underwent almost no change on variation in concentration of I. This indicates that the methyl sulfonate was formed by the molecular decomposition of the initial peroxide:
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Synthesis of crystalline polyvinylcyclohexane
Authors: Mushina E. A. , Perel'Man A. I. , Topchiev A. V. , Krentsel B. A.
Published: April 2003

The least known field of stereospecific polymerization is the polymerization of vinylcycloalkanes. At the same time polyvinylalkanes and especially polyvinylcycloalkanes may be of considerable interest as a new class of crystalline polyvinyl compounds. With this in mind the synthesis of polyvinylcyclohexane has been carried out and its properties have been investigated. Polymerization of vinylcyclohexane takes place in the presence of titanium tetrachloride and isobutylaluminum or of chromium oxides on aluminum silicate. The polymer obtained with different catalysts and under varying conditions (temperature, solvent, catalyst concentration, etc.) according to x‐ray data has a high degree of crystallinity. The melting point is 325° and the intrinsic viscosity from 0.5 to 1.5. A characteristic feature is its good solubility in naphthenic and aromatic hydrocarbons. The structure of the polymer has been established and thermomechanical curves have been determined for polymers obtained on various catalysts.
Some problems of polycondensation in suspensions
Authors: Lesek F. , Khromeček R.
Published: April 2003

From a hydrodynamic standpoint an anology exists between suspension polycondensation and suspension polymerization. The hydrodynamics of polycondensation have been less thoroughly investigated for water/oil than oil/water systems. From a physicochemical standpoint suspension polycondensation differs from suspension polymerization in a number of features. In the presence of excess surface‐active agent an emulsion is formed only in exceptional cases. The amount of surface‐active agents in suspension polycondensation exceeds that employed in polymerization. In the latter case, traces of surface‐active substances are used; with increase in their concentration a tendency towards block polymerization appears. The course of the reaction depends to a large extent upon the nature of the stabilizer. A stabilizer similar in character to the condensation system is advantageous. It may be assumed that in some cases an acid stabilizer enhances concentration of the reaction catalyst at the interfacial boundary. The nature of the components of the system has a considerable effect on the polycondensation. In the future the effect of the disperse phase on the course of the reaction will be investigated. Despite the close values of density and interfacial tension the use of such hydrocarbons as xylene and tetrachloroethane is more suitable than the use of chlorobenzene or tetrachloroethylene. The opinion exists that suspension polymerization is mainly block polymerization. This hypothesis does not seem to hold in the case of the surface layer of globules. In suspension polycondensation the degree of homogeneity of the initial components plays an important part, particularly on a commercial scale.
The catalytic action of some metal compounds on the preparation of polyurethans
Authors: Blagonravova A. A. , Levkovich G. A. , Pronina I. A.
Published: April 2003

A study has been made of the catalytic effectof various salts on the formation of poly‐ urethans. The main attention was paid to the catalytic action of zinc compounds (zinc oxide, zinc acetate, and basic zinc chromate) in the reaction of 2,4toluene diisocyanate with hydroxyl‐containing compounds (β‐hydroxyethyl adipate and ethylene glycol). The experiments showed that the rate of change of isocyanate group content during poly‐ urethan formation greatly depends upon the cwntent of the zinc compounds. A neces‐ sary condition for the appearance of a catalytic effwt was found to be preliminary contact (before isocyanatc addition) of the zinc compound u ith β‐hydroxyethyl adipate. It was also found that after contact with the zinc compound the ester alone wiII react with the isocyanate at the same rate as in the presence of the catalyst. The same relation were also found for the system ethylene glycol‐toluene diisocyanate. The reaction is also ac‐ celerated by the zinc compounds, separation of the glycol after contact not lowering the velocity. Acids like anthranilic, o‐phthalic and acetic have been found to lower the rate of change of isocyanate groups in the systems containing catalysts. The strongest inhibit‐ ing effect is exerted by anthranilic acid. The catalytic activity of zinc acetate has been shown to exceed that of zinc oxide. The effect of the time of preliminary contact on the magnitude of the catalytic action in zinc acetate‐ester systems is much less expressed then in zinc oxide‐ster systems. Catalysts of the reaction between isocyanate and hydroxyl‐ containing compounds may be divided into two groups. To one group belong the oxides and salts of some metals: typical representatives of the other group are organic bases. A comparison of the catalytic activities of zinc oxide and pyridine showed the latter to be of considerably lower activity. Ways have been found for the stabilization of pigmented polyurethan systems, making it possible to greatly increase the variety of pigments rec‐ ommended for use in polyurethan paints.
On the polymerization of polyfunctional compounds
Authors: Arbuzova I. A. , Rostovskiĭ E. N.
Published: April 2003

The present investigation is a two‐sided approach to polyfunctional compounds, namely: (1) polymerization of unsaturated monomers containing reactive groups, in particular, methylol derivatives of unsaturated acids; (2) cyclopolymerization of diolefinic monomers. In the first method of attack conditions have been investigated under which soluble, linear polymers are formed. Our studies have thrown light on the mechanism of reactions facilitating the formation of crosslinks. From a study of the polymerization of methylolacrylamide monomers (in collaboration with L. M. Novichkova) it became possible to direct the reaction towards the formation of soluble, linear polymers. The possibility of further conversions such as transformation of the linear polymers to three‐dimensional ones leads to the polymerization‐condensation concept of polymer formation. This is of particular interest, since it provides the basis for predetermined modification of polymer properties (for example, elimination of flow, increase of strength, chemical resistance, etc.). The reactivity of the methylolamide group allows the use of the compounds in question for these purposes, for instance as copolymer with acrylonitrile. The second method of attack is the cyclic polymerization of symmetrical and unsymmetrical diolefine monomers and of compounds arising in the process of polymerization of 1–6 unsaturated systems. Earlier, Butler, Marvel, Jones and others pointed out the formation of linear cyclic polymers in the polymerization of symmetric divinyl and diallyl monomers unsaturated in the 1,5‐ and 1,6‐positions. The authors of the present work have synthesized a number of acetals of vinyl alcohol and ascertained the conditions for the formation of linear polymers consisting of six‐membered cyclic repeating units connected by methylene groups. Polymerization of asymmetric diene monomers was investigated using as examples vinyl crotonate, bulk polymerization of equimolecular quantities of allyl alcohol and maleic anhydride, and copolymerization of maleic anhydride with dibenzalactone. The establishment of the possibility of divinylacetal polymerization according to a cyclic mechanism makes it possible to outline new ways of synthesis of the acetals of polyvinyl alcohol. It has also been found that in the polymerization of the asymmetric diene monomers vinylcrotonate and monoallyl maleate, soluble, linear polymers are formed, of which the properties indicate that cyclization takes place in the course of the reaction.
A new redox system for vinyl polymerization in aqueous medium
Authors: Menon C. C. , Kapur S. L.
Published: April 2003

A new redox system for vinyl polymerization comprising hydrazine, cupric ions and molecular oxygen is described. The influece of the pH of the medium, the monomer concentration, and the concentration of cupric ions on the rate of polymerization and the rate of hydrazine disappearance is studied. The results are explained in terms of a mechanism involving one‐electron oxidation of hydrazine by a cupric ion to produce the hydrazyl radical, the conversion of cuprous ions to cupric ions by atmospheric oxygen which involves radical intermediates capable of initiation of polymerization and a termination reaction involving the polymeric radical, cuprous ion and oxygen.
Communication on oligomers. XXIII. Synthesis of amino alcohols by the action of lithium aluminum hydride on oligamides of ε‐aminocaproic acid
Authors: Zahn H. , Gleissner A.
Published: April 2003

The synthesis of the homologous series of (I) amino alcohols H[NH(CH2)6]nOH, wheren= 1–9, and (II) their methylated products CH3[NH(CH2)6]nOH, wheren= 1–9, is described. These compounds are easily prepared by lithium aluminum hydride reduction of oligamides of ϵ‐aminocaproic acid. Nylon 6, the crystalline part of silk, and the tetrapeptide Gly‐Ala‐Gly‐Ala were also to their corresponding amino alcohols.
Coordination compounds of p‐(1,3‐butanedione)‐N‐phenylglycine
Authors: Mattison Louis E. , Phipps Martha S. , Kazan John , Alfred Lillian
Published: April 2003

A new chelating agent containing two different chelating systems in the same molecule was synthesized: p‐(1,3‐butanedione)‐N‐phenylglycine. Simultaneous coordination of this molecule with divalent lead and uranyl ions resulted in a bimetallic chelate polymer. Also prepared were coordination polymers of the chelating agent with the following divalent metal ions: beryllium, copper, magnesium, nickel, uranyl, and zinc. Thermal analysis data show that the beryllium, zinc, and uranyl polymers are exceptionally stable, with from 0.39–0.65% weight loss per hour at 200° in air. Four monomeric chelates were also investigated.
Radiation‐induced ionic polymerization at low temperature
Authors: Tsuda Yoshizo
Published: April 2003

The copolymerization, by means of ionizing radiation, of acrylonitrile with styrene or methyl methacrylate was investigated at ‐78°C. in bulk and in various solvents. The copolymerization proceeds by a cationic mechanism in methylene chloride solution, by a free radical mechanism in bulk, and by both an anionic mechanism and a free radical mechanism in dimethyl formamide, diethylamine, toluene, and ethyl bromide solutions. The rate of anionic polymerization of acrylonitrile increases with dilution of monomer. The cationic polymerization in methylene chloride solution was shown to be caused by the catalytic action of hydrogen chloride which is formed from the irradiation of chlorinated hydrocarbon. It was concluded that the main factor in the induction of an anionic polymerization of acrylonitrile is the large reactivity of the monomer in anionic polymerization.
Suspension polymerization of vinyl chloride at low temperature with the use of monomer‐soluble redox initiators
Authors: Konishi Akio , Nambu Keiichi
Published: April 2003

Suspension polymerization of vinyl chloride was carried out at temperatures of ‐30° to +30°C. with the use of a monomer‐soluble oxidation‐reduction initiator system. A typical initiator system was composed of lauroyl peroxide and ferrous n‐caproate. The effects of temperature, molar ratio of peroxide to reducing agent, and total concentration of initiator upon the rate and degree of polymerization were observed. The activation energy of the overall rate of polymerization was 6.5 kcal./mole. Experimental evidence which may serve to elucidate the mechanism of the redox reaction in the nonemulsified system is discussed.