bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of the polyurethane resin coating used in the control of area shrinkage of woolen fabrics
Authors: Beevers R. B.
Published: June 2010

Stress relaxation measurements are reported for the polyurethane resin Synthappret, which is used to prevent area shrinkage in woolen fabrics. The experimental data are in satisfactory agreement with computed stress decay assuming two independent first‐order rate equations with activation energies of 11 ± 6 and 29 ± 4 kcal/mole−1. It is considered that the decay process involving the lower activation energy arises from tearing of the resin, and this is supported by stereoscan electron microscope examination. The mechanism by which the resin controls fabric shrinkage is discussed.
Chemical transformation of polymers. XV. Poly(ethylene methacrylate arylsulfo‐nates) as alkylation agents
Authors: Peška J. , Štamberg J. , Schmidt P. , Beneš M. J.
Published: June 2010

Polymers of ethylene methacrylate, toluene‐, and benzenesulfonate are shown to be strongalkylating agents. Their polymer‐analogous reaction with most nucleophiles proceeds smoothly under conditions comparable to those of low molecular analogs. The nucleophiles used successfully were of the nitrogen type: amines, pyridine, phthalimidate, azide; or oxygen: alkoxide, phenolate, carboxylate; sulfur: thioacetate, thiocyanate, thiourea; and other types: iodide. Further reaction of some of these derivatives, e.g., hydrolysis to thiol or amine, proceeds as expected.
Investigation of thermal polycyclocon‐densation of polyhydrazides
Authors: Korshak V. V. , Berestneva G. L. , Bragina I. P. , Astafiev S. A.
Published: June 2010

This paper presents the results of investigations on thermal polycyclocondensation of polyhydrazides to corresponding poly‐1,3,4‐oxadiazoles. A limiting character of conversion is associated with the mobility of polymeric chains due to the fact that they become rigid by conversion of linear hydrazide fragments into cyclic 1,3,4‐oxadiazole ones, as well as to an increasing content of the latter in the course of conversion. Hence, the kinetics of the solid‐phase polycyclization of polyhydrazides is determined not only by the reactivity of groups participating in cyclization, but also by some factors indicating the effect of the structure on the starting polymeric compound and that of the structure order.
L‐asparaginase from Escherichia coli II and Erwinia carotovora bound to poly‐(methyl methacrylate)
Authors: Hersh L. S.
Published: June 2010

L‐asparaginase (ASNase) from Escherichia coli (EC) II and Erwinia carotovora (Erw. carot.) has been chemically coupled to poly(methyl methacrylate) (PMMA) via the bifunctional coupling agents γ‐aminopropyltriethoxysilane and glutaraldehyde.

The level of bound activity was about 2 and 6 IU/100 cm2, respectively. The immobilized asparaginases were successfully used in previously reported in vivo experiments. Certain kinetic characteristics such as pH profile and temperature dependence were unafected by the immobilization process Both bound asparaginase's apparent Km were greater than the native enzyme's value by approximately an order of magnitude. The apparent Km for the EC ASNase was approximately the same in buffer solutions and in pooled canine blood.
Investigation of the formation of strongly acid cation exchange resins based on slightly cross‐linked copolymers
Authors: Schwachula G. , Hauptmann R. , Kain I.
Published: June 2010

Our investigations of the cation exchange resins based on styrene‐divinylbenzene (DVB) have shown that because of its unfavorable reactivity towards styrene, the DVB causes great inhomogeneities in the copolymers formed with styrene. This affects, in a negative way, the mechanical stability of the strongly acid cation exchange resin produced. On the other hand, strongly acid cation exchange resins based on polystyrene may be produced by reacting polystyrene in two steps with chlorosulfonic acid in the presence of formaldehyde. Furthermore, it has been successfully tied to chloromethylate polystyrene in the presence of paraformaldehyde or methylal so that a cross‐linked chloromethylated product was formed.

It has been the aim of our investigations to make sure if, on the one hand, on the basis of polystyrene, it was possible by chloromethylation to get a cross‐linked product that could be subsequently worked into a strongly acid cation exchange resin or, on the other hand, to verify if one could, based on polystyrene in the presence of a formaldehyde‐releasing substance, sulfonate in one step so that the product is cross‐linked at the same time. The quality criterion of all experiments is to guarantee that the characteristics of the final product, i.e., a strongly acid cation exchange resin, are comparable to those of the well‐known resin types based on styrene‐DVB.
Investigation of the surface structure of polymers by chromatographic methods. I. Hydrophilized polyethylene capillaries for medical applications
Authors: Hradil J. , Stamberg J. , Kaganov A. L. , Synek P.
Published: June 2010

Polyethylene catheters being treated with chromosulphuric acid at room temperature became hydrophilic on the surface and readily accepted a hydrophilic polymer layer. Almost no differences in chemical composition between the original and the treated polymer samples were found by conventional methods. On the other hand, the method of inverse gas chromatography showed significant changes both in the physical and chemical surface structure. The Rohrschneider's polarity factors already attained the values for poly(2‐hydroxy‐ethyl methacrylate) after a short time of treatment. Hydrophilized polyethylene catheters coated with soluble poly(2‐hydroxyethyl methacrylate) were well tolerated by the patients and did not cause formation of thrombi or phlebitis.
Preparation and properties of heparin‐poly (methyl methacrylate) copolmers
Authors: Labarre D. , Boffa M. C. , Jozefowicz M.
Published: June 2010

A new technique of covalent bonding of poly(methyl methacrylate) (PMMA) onto heparin (HEP) is described. The reaction involved implicates radical polymerization of methyl methacrylate (MMA) initiated by a heparin radical resulting from reaction between cerium (Ce) (IV) ion and heparin in aqueous solution.

The characteristics of the grafting reaction and of the resulting polymers have been studied. The blood compatibility of powders or films of the polymers are actually studied. The preliminary results show that these copolymers might be interesting for medical applications.
Fixation de microchainons carbonyles sur des polyisoprenes et polybutadienes par hydroboration. reaction sur modeles macromoleculaires
Authors: Pinazzi C. P. , Guillaume P. , Reyx D.
Published: June 2010

1,4 Addition of trialkylboranes on unsatured carbonyl compounds allows the fast synthesis of aldehydes and ketones. The application of this reaction to macromolecular trialkylborane microstructures derived from polyisoprenes and polybutadienes has been considered. The reaction involves the homolytic scission of one of the three C‐B bonds leading to the fixation of the oxoalkyl group on the considered carbon. In the macromolecular trialkylborane structures, fixation of the carbonyl microchain on the polymer is only realized by scission of the macromolecular carbon‐boron bond; the two other possible scissions lead to macromolecular borinic structures.

Polydiene macromolecular models have been used to study the application of this hydroboration‐addition coupled reaction to the corresponding polymers. They have allowed the synthesis of modified microstructure models by use of diborane as hydroborating agent. Moreover, they have been used to measure the selectivity of the fixation γ‐oxoalkyl group on the modelized macromolecular carbon. Using bis‐boracyclanes as hydroborating agents, a quasi‐selective conversion of 1,4‐polydienes to carbonylated structures can be obtained; on the contrary, with 1,2 and 3,4 polydienes, the selectivity never exceeds 50%.
Chemical transformations of polymers. XIII. Effect of supermolecular structure on the transformation of polyethylene with chlorosulphonic acid
Authors: Baldrian J. , Hradil J. , Štamberg J.
Published: June 2010

The degree of transformation of polyethylene with chlorosulphonic acid depends on the number of branches. It is increased not only by using better swelling agents, but also—and prevailingly—by an increase in the amorphous portion of the starting polymer. Chlorosulphonation takes place in amorphous regions, because they are accessible to low‐molecular‐weight components and contain reactive parts of the polymer chains with tertiary carbon atoms. As the transformation proceeds, crystallinity falls down and dimensions of crystallites run low by oxidation splitting of chains.
Swelling of cellulosic gels
Authors: Chitumbo K. , Brown W. , De Ruvo A.
Published: June 2010

The swelling behavior of a tightly cross‐linked cellulose gel has been studied in various polar solvents as a function of temperature. Pronounced second‐order transitions were observed at about 25 and 60°C, which may correspond to those previously reported in the literature dealing with cellulosic fibers. The transitions are attributed to changes in hydrogen bonding in the system.

With the carboxymethyl and dicarboxymethyl derivatives of the cellulose gel, sharp second‐order transitions were found at about 25 and 50°C, characterizing interactions involving carboxyl groups. The solvent dependence of the swelling behavior is pronounced.

No temperature dependence of swelling was observed with acetylated, methylated, and trimethylsilylated forms of the gel, in which systems hydrogen bonding has been effectively eliminated.
Complex formation between poly(vinyl alcohol) and metallic ions in aqueous solution
Authors: Hojo Nobumasa , Shirai Hirofusa , Hayashi Sadao
Published: June 2010

As the basic research for the study of complex reactions in polymers, the complex formation of poly(vinyl alcohol) (PVA) with copper and other metals was tried. Spectroscopy, pH titration, and elementary analysis were employed in the reaction of PVA and Cu(II) ions in aqueous solution. The complexing protonation was found in the higher pH region (above 7.0), and the maximum absorptions at 640 and 260 nm were observed. These ϵmax were proportional to the concentrations of Cu(II) ions bound to the hydroxyl groups of PVA. Formation constants of the PVA–Cu(II) complexes were measured by applying a modified Bjerrum's method. The effects of the ratio Tcu2+/THL, the anions in copper salts, and the degree of polymerization on the formation constants were studied. Four hydroxyl groups combined with one Cu(II) ion in the pH range above 7.0. The stability constants for the complexes of PVA with bivalent transition metallic ions were in agreement with the Irving‐William's series. The changes in viscosity, solubility, tacticity, mechanochemical phenomenon, and the other properties based on the complex formation are discussed.
The use of NMR techniques in the study of protein hydration
Authors: Lynch L. J. , Webster D. S.
Published: June 2010

An attempt is made to outline the role of nuclear magnetic resonance (NMR) in the study of the hydration of proteins. NMR techniques are very effective in these studies because of the sensitivity of the magnetic resonance of isotopes of the water molecule (usually 1H, 2H, and 17O) to the changes in the molecular state and environment that are brought about by the water‐protein interaction. The NMR techniques which are effective in characterizing specific properties of the hydration water such as mobility, anisotropy, and heterogeneity are discussed. Methods of interpreting the data so obtained in terms of these molecular properties as applied to particular protein‐water systems are outlined.
Determination of the sequence of peptides using paramagnetic probes with NMR spectroscopy
Authors: Warren Brian , Bradbury J. H.
Published: June 2010

The paramagnetic ion Gd3+ binds to the α‐carboxyl group of a peptide and broadens the resonances from the 13C and 1H nuclei of the backbone sequentially along the chain. The sequential broadening of both carbonyl and Cα nuclei of PheAspAlaSerVal have been observed in 6 M guanidine hydrochloride at pH 4.0. Sequential broadening from the N‐terminus is also possible using Cu2+ at pH ≥ 8.

Broadening experiments using triglycine and either Gd3+ or Cu2+ show that it is more difficult to broaden 13C than 1H resonances on the same amino acid residue. The ratio of [Gd3+]CMR/[Gd3+]PMR is 12 ± 5, which agrees reasonably well with the theoretical value of 16. The ratio [Cu2+]CMR/[Cu2+]PMR is 3 ± 2.

The relative advantages of proton magnetic resonance (PMR) and carbon‐13 magnetic resonance (CMR) spectroscopy for this application are discussed. It is concluded that sequence determinations of 20 mg samples of peptides, ranging in size up to 7–9 residues, should be possible using CMR spectroscopy. The main advantage of PMR spectroscopy is the much smaller amounts of material required, but other problems preclude its use at this time except for very simple peptides.
Mechanical degradation of gluten proteins during high‐speed mixing of doughs
Authors: Macritchie F.
Published: June 2010

Bueche's theory of the mechanical degradation of polymers in shear is applied to try to account for the changes in flour proteins following high‐speed mixing of doughs. Because of the high viscosity of dough (∼ 108 poise), shear strain rates on the order of 102 sec−1, which are encountered in standard dough mixers, are sufficient to cause scission of covalent bonds. The limiting amount of protein, extractable after mixing, increased with mixing speed, in agreement with the predicted effect of strain rate on breakdown. Agents which crosslinked protein chains through strong covalent bonds increased the mixing stability of doughs, while those which crosslinked by formation of SS bonds greatly accelerated breakdown, reflecting the more labile nature of the SS bond. Some predictions about the rheclogical effectiveness of different SS bonds follow from the theory. Predicted changes in molecular weight distribution of protein following mixing are in agreement with experimental results obtained by other workers.
The insolubilization of trypsin by attachment to radiation graft copolymers of polypropylene
Authors: Liddy Michael J. , Garnett John L. , Kenyon Robert S.
Published: June 2010

Novel methods have been developed for the preparation of polymers suitable for the attachment of enzymes, or other biochemical macromolecules, to render them water insoluble. By a new irradiation process, p‐nitrostyrene has been graft copolymerized to trunk polymers, such as polypropylene. Reduction of the nitro group in the graft copolymer gives the amino derivative, which may be converted to other functional groups (isothiocyanato or diazo) or used in conjunction with bifunctional reagents in order to covalently bind enzymes to produce active, water‐insoluble conjugates. The properties of one such conjugate, in which trypsin was immobilized by covalent attachment to poly(p‐isothiocyanatostyrene‐g‐propylene) are discussed. The advantages of the present radiation grafting technique are compared with conventional methods for insolubilizing enzymes.
Gel permeation chromatography of polymers
Authors: Hammond J. M. , Hooper J. F. , Stutchbury J. E.
Published: June 2010

The literature on gel permeation chromatography (GPC) is surveyed and briefly reviewed to provide a guide to some of the more important references, particularly those dealing with equipment and polymer molecular weight determination. A number of applications of GPC in the authors' laboratories are discussed in order to illustrate use of the GPC technique, with particular regard to its value in estimating low molecular weight substances present in polymers.
Pulse radiolysis of styrene and acrylate monomers
Authors: Sangster David F. , Davison Alan
Published: June 2010

Pulse radiolysis has been used to investigate the transient species formed in aqueous and methanolic solutions of styrene, α‐methyl styrene, methyl methacrylate, and butyl acrylate. The reaction rate constants for formation and disappearance of these species and their activation energies are reported.

In aqueous solutions, the primary radical products of the radiolysis of water react with styrene. About 20% of the ·OH radicals and about 45% of the reducing radicals, eaq and ·H, give the benzyl radicals C6H5CHCH2OH and C6H5CHCH3, respectively. The remaining 80% and 55% give the cyclohexadienyl radicals HOC6H5CHCH2 and C6H6 CHCH2, respectively. In methanol solutions, the cyclohexadienyl radical C6H6 CHCH2 is the only one detected.

The kinetic parameters for radical‐radical dimerization of methyl methacrylate and of butyl acrylate are similar, showing that the differences in termination rates observed for the conventional polymerization of these monomers are due not to electronic, but to viscosity‐structural factors.
Electroinitiated ionic polymerization
Authors: Giusti Paolo
Published: June 2010

A classification of the electroinitiation processes which takes into account the nature of the electrodic processes undergone by the different substances present in the reaction mixture is proposed.

Some of the most recent results obtained in the author's laboratories on both electroinitiated and electroinfluenced polymerizations are briefly described and discussed.

An algebraic treatment is also illustrated, which stresses the importance of the diffusion phenomena thus far neglected by most researchers. The theoretical results of this treatment are shown to closely agree with the experimental results.
Plastic film technology
Authors: Alfrey T.
Published: June 2010

Polymer films represent an important part of polymer science and technology. With regard to geometry, orientation, and mechanics, films are 2‐dimensional analogues of fine fibers. The use of different polymers in multilayer composite films broadens the scope of achievable film properties.
Copolymérisation Radiochimique Des Mélanges Acide Acrylique‐N‐Vinylcarbazole en Solution
Authors: Chapiro Adolphe , Mankowski Zbigniew
Published: June 2010

L'acide acrylique forme avec le vinylcarbazole un complexe moléculaire qui a été caractérisé par une discontinuité sur la courbe des indices de réfraction des mélanges et par l'apparition d'une nouvelle bande d'absorption dans l'infra‐rouge à 1180 cm−1. Ce complexe est d'autant plus stable que la concentration des monomères est plus élevée et que la température est plus basse. La cinétique de la copolymérisation des deux monomères a été étudiée dans différents solvants et à différentes températures. La variation des vitesses en fonction de la composition du mélange des monomères est complexe. En solution dans le chloroforme et dans le méthanol la vitesse est maximale pour le mélange équimoléculaire ce qui indique que la réaction de propagation est favorisée dans le complexe moléculaire; cependant, dans le dioxanne et le n‐hexane la vitesse décroit régulièrement avec la teneur de vinylcarbazole dans le mélange et dans le toluène on observe un maximum des vitesses pour une fraction molaire de vinylcarbazole de 0,30. Les copolyméres formés dans les diffèrents solvants possèdent souvent une composition 50‐50 constante dans un domaine de compositions plus ou moins vaste du mélange initial. Ce résultat suggère que ces copolymères ont une structure régulièrement alternée. La tendance à l'alternance augmente avec la concentration des deux monomères dans la solution et elle diminue lorsque la température de la réaction s'élève. Dans le dioxanne on n'a pas obtenu de copolymère alterné. On discute l'ensemble de ces résultats dans le cadre des associations moléculaires qui existent dans les différents milieux. On a étudié les caractères de solubilité du copolymère alterné et on les a comparés avec celles d'un copolymère de měme composition 50‐50 mais dont la distribution des motifs est plus statistique.
Properties and methods of synthesis of several optically active polyoxiranes and polythiiranes
Authors: Spassky Nicolas , Dumas Philippe , Sepulchre Maurice , Sigwalt Pierre
Published: June 2010

Optically active oxiranes and thiiranes are prepared from the corresponding asymmetric 1,2‐diols or by means of stereoelective polymerization.

The properties of polymers prepared from chiral monomers by polymerization with anionic, cationic, and stereospecific initiators are compared. In the latter case, the stereospecificity depends not only on the nature of the monomer but also on its enantiomeric distribution. The direction of ring opening could be easily followed when using optically active monomers and there are satisfactory correlations with other methods such as ozonolysis or NMR spectroscopy. In some cases properties of optically active and racemic polymers are different, this enables their separation by physical methods. Chiroptical properties of monomers and polymers having thioether chromophores are given. The stereoregularity of the polymers determined by NMR spectroscopy may be correlated and substantiated by calculations of enantiomeric distribution from optical activity. Optical activity is, therefore, a useful tool for studying the mechanistic aspects of polymerization and the properties of the obtained products.
Crosslinking with s2ci2 of some epdm rubbers and their stress‐strain behaviors
Authors: Penati Amabile , Pegoraro Mario
Published: June 2010

Crosslinking of swollen terpolymers of ethylene‐propylene‐diene (EPDM) with S2CI2 dissolved in n‐butylacetate was carried out at room temperature.

Small, low thickness EPDM specimens, characterized by different amounts of double bonds (3,5, 4, 6, 10 weight‐% of 5‐ethylidene‐2‐norbornene), were crosslinked; the kinetic reaction was followed by measuring the degree of swelling in benzene, and calculating the elastically effective chain density according to the Flory‐Rehner theory. Using an excess of S2CI2 solution to operate at an almost constant S2CI2 concentration, we observed that the crosslinking rate depends on the double bond percentage only at the beginning of the reaction; after some hours the reaction rate decreases. This demonstrates the importance of the S2CI2 diffusion rate inside the samples.

Stress‐strain curves of four different EPDM were obtained before and after crosslinking. Before crosslinking the EPDM behavior depends principally on the ethylene content: the 5‐ethylidene‐2‐norbornene decreases the values of the maximum initial stress, which is attributed to the ethylenic unit distribution in the chains. After crosslinking the EPDM behavior depends, instead, on the crosslinking density.
Effect of steric obstructions in networks on equilibrium properties of crosslinked polymers
Authors: Priss L. S.
Published: June 2010

According to the statistical theory of polymer chains in Gaussian approximation, their transversal dimensions, characterized by the root‐mean‐square distances between the chain segments and the straight line connecting the ends of the chain (r2 1/2 = r), do not depend on the end‐to‐end distance (h). Therefore, the classical rubber‐like elasticity theory takes into account only the entropy change (δSh) related to the variation of h. Upon instantaneous deformation, all linear dimensions of the chains are changed, and the establishment of equilibrium involves, in particular, the recovery of initial r. In the real network, the chains, having drawn together after deformation, hinder the completion of the process since they cannot pass through each other. Thus, in an equilibrium deformed network, r does not reach its actual equilibrium value, thus causing the additional entropy change (δSr). δSr and δSh depend on elongation ratios λi in different ways, for h and r change at deformation in a dissimilar manner.

The theory based on these premises describes well the regularities of various types of deformation. In particular, for the nominal stress f at uniaxial tension one gets the formula which is close to the Mooney‐Rivlin equation for 0.2 < λ−1 < 0.9. Here C1 is expressed through molecular parameters in the usual way, and K is a constant determined by arrangement of steric obstructions. The same ideas allow us to propose a qualitative explanation for a wide range of regularities found for the equilibrium properties of rubbers.
Swelling equilibrium in the system ethyl‐benzene‐1,3 diphenylbutane‐crosslinked polystyrene
Authors: Máša Z. , Pouchlý J. , Přibilová J. , Biroš J.
Published: June 2010

The equations for total and preferential sorptions in a ternary mixture liquid(1)‐liquid(2)‐polymer network(3) were derived for systems obeying the Flory‐Huggins equation with the concentration dependent interaction parameters. The equilibrium degree of swelling of the three styrene‐divinylbenzene copolymers in toluene, ethylbenzene, 2,2′‐ditolyl, 3,3′‐ditolyl, and 1,3‐diphenylbutane was measured along with the total swelling and the preferential sorption in the system of the three members of one homologous series ethylbenzene‐1,3‐diphenylbutane‐crosslinked polystyrene. The difference in molar volumes of components is revealed in two ways: via the combinatorial entropy and the interaction parameters (through the Prigogine‐Patterson structural effect). Both these counteractive influences are more fully compensated in the case of the total swelling than in the preferential sorption. The positive value of χ12 parameter increases the degree of swelling of the polymer in a binary mixture of components 1 and 2, but the increase is lower than that according to the Flory‐Huggins theory; this fact justifies the introduction of a ternary parameter χT as an empirical correction. Similar results were obtained by Bristow in a study of benzene‐cyclohexane‐polymer network systems.
Low‐frequency dynamic mechanical behavior of polyacrylate networks
Authors: Janáček J. , Hrouz J.
Published: June 2010

A low‐frequency vibration apparatus was used for measurements of the dynamic mechanical behavior of poly (methyl acrylate), poly (ethyl acrylate), and poly(octyl acrylate) networks in the frequency range of 0.001 to 0.5 Hz, and with temperatures from –40 to 100°C. The polymers were prepared by radical polymerization in the absence of crosslinking agent, and in the presence of 0.1 and 0.2 × 10−4 mole cm−3 ethylene dimethacrylate. The complex dynamic compliance values were determined in the rubber‐like region starting from log J'p = –7.5 and higher; the data obtained were reduced to a reference temperature of 25°C.

The contribution of long retardation times of untrapped entanglements to the compliance in the rubber‐like region, according to Ferry (Je – JeN), was compared with the values obtained earlier for networks of poly (butyl methacrylate), poly (butyl acrylate), natural, butadiene‐styrene, and polybutadiene rubber. It was found that this contribution, at the same equilibrium compliance, is highest for rubbers, and higher for methacrylates compared to acrylates. The increasing length of side chains of polyacrylates leads to an increase in the difference (Je – JeN).
Differences in the mechanical and optical behavior of the physical network of amorphous poly(ethylene terephthalate) as a result of annealing
Authors: Vaníček J. , Janáček J.
Published: June 2010

The properties of undrawn amorphous poly(ethylene terephthalate) fibers where the optical anisotropy had a of magnitude of 10−3 were investigated. The fibers behave as a deformed frozen network of entanglements formed in the process of spinning. The shrinking of the fibers is observed when heating them to a temperature above Tg. It was found that the annealing of fibers at a constant length at temperatures near Tg results in a decrease of their birefringence, but that shrinking and the retractive force changed only negligibly. The results obtained can be explained by means of Yeh's model of amorphous polymers. It can be assumed that annealing leads to conformational changes inside the nodules, with a predominantly parallel order of the chains, probably without involving any changes in the network of entanglements. As a consequence, annealing results in a decrease in the stress‐optical coefficient. Annealing does not produce any changes in the natural drawing ratio of the fibers which seems to indicate that its value is not directly related with the birefringence, as has been assumed up to now but that it has a relation to the network of entanglements.
Molecular weight determinations by vapor‐pressure osmometry
Authors: Morris C. E. M.
Published: June 2010

Some of the factors which affect the accuracy of number‐average molecular weight determinations by vapor‐pressure osmometry are discussed. It is shown that care is required in the selection of compounds for calibration purposes to ensure that solute volatility effects do not lead to erroneous results. It is also demonstrated that, in certain systems at least, the calibration factor has a small but important dependence on the solute molecular weight over the molecular weight range examined (128–883).
Atmospheric heat aging of carboxyl‐terminated polybutadiene
Authors: Cowan J. R. , Hammond J. M. , Hooper J. F.
Published: June 2010

Thiokol HC 434 carboxyl‐terminated polybutadiene on hot storage in air increases in viscosity and molecular weight until, finally, gelation occurs. It was found that rate of aging can vary greatly from lot to lot. The difference in aging between lots is thought to be caused by a decrease in the catalytic activity of metal ion impurities due to chelation by varying amounts of glutaric acid remaining in HC 434 after manufacture. Stability of poorer‐aging HC 434 is improved by adding glutaric acid or other chelating agents.
The influence of molecular characteristics of synthetic rubbers on mixing and extrusion behavior
Authors: Giurco Flavio , Mills Wayne
Published: June 2010

This paper presents results which indicate that nonuniformities in the mixing and extrusion behavior of nominally standard grades of emulsion‐ and solution‐polymerized oil‐extended SBR are associated with variations in molecular weight distribution, which are not reflected by Mooney viscosity values.

Generally, copolymers with broader molecular weight distribution have higher compound die swell, and lower rates of carbon black dispersion during mixing. Delta Mooney values and torque rheometer t' point tests were found to be of utility in predicting extrusion die swell and carbon black dispersion characteristics of oil‐extended SBR.
Variable‐composition polysulfones by free‐radical copolymerization of vinyl chloride with sulfur dioxide
Authors: Cais R. E. , O'Donnell J. H.
Published: June 2010

The relationship between copolymer composition and comonomer composition for the freeradical copolymerization of vinyl chloride with sulfur dioxide, initiated by γ‐irradiation and by tert‐butyl hydroperoxide/methanol at low temperatures, is compared with the relationships calculated from various possible copolymerization mechanisms using a range of reactivity ratios and equilibrium constants. The copolymerization approaches Lewis‐Mayo behavior at low temperatures (–78°C), but this model is inapplicable at higher temperatures. Copolymerization models involving (i) a 1:1 comonomer complex as a third monomer, or (ii) a penultimate effect of SO2 on SO2 addition to the propagating chain, are satisfactory at – 78°C, when they are indistinguishable from Lewis‐Mayo behavior, and also at 0°C, but not at other temperatures. A depropagation model involving reversibility of three propagation reactions with different temperature dependences will, however, satisfactorily explain the observed behavior at all temperatures.
New composite ion‐exchange resins made from neutral precursors
Authors: Bolto B. A. , Jackson M. B. , Siudak R. V. , Battaerd H. A. J. , Shah P. G. S.
Published: June 2010

The preparation of composite ion‐exchange or “no‐matrix” resins by polymerizing a mixture of basic and acidic monomers is a practical proposition only if some means can be found to minimize interaction between the monomers, so that the sites in the final polymer are not rendered inactive by internal salt formation. This paper reports one method of avoiding the strong interaction between the oppositely charged monomers by employing one or both of the monomers as an electrically neutral precursor. After carrying out the polymerization, the groups may be converted to a usable form by hydrolysis. The effect of solvent, the acid to base ratio, the degree of crosslinking, and the effect of the nature of the initiator on the preparation and properties of no‐matrix resins prepared using neutral acid precursors was studied; it was found that no‐matrix resins may be obtained with thermally regenerable capacities comparable to “plum pudding” resins.
Application of surface physics techniques to surface coatings
Authors: Paterson P. J. K. , Moon A. R. , Aubert R. , Brooker K. , Kottek P. , Starbuck P. , Viglione G. , Willmott M. , Dean M. , Coates R. , Lubbock F. J.
Published: June 2010

This paper presents a review of aspects of surface coatings investigated at the Applied Physics Department, Royal Melbourne Institute of Technology, in consultation with Dulux (Australia). The major aim for Applied Physics is the application of surface physics techniques to the development of surface coatings. The principal techniques include scanning and transmission electron microscopy, optical microscopy, microprobe analysis, spectrophotometry, depthcomposition profiling by Auger spectroscopy, and ion‐beam erosion. The major surface‐coating projects have been: (a) development of white paint without pigment in which water emulsions were used to provide air bubbles to replace pigment as light‐scattering centers with the aim of finding the system with best optical and physical properties; (b) surface defects in paint films: a number of defects have been investigated, including overspray cratering, loss of gloss by microcracking, and change of color by the action of Benard Cells in high solids paint films; (c) the mechanism of marking of flat plastic interior paints when wiped; and (d) adhesion between coating and substrate: several surface coating‐substrate combinations are being examined by Auger spectroscopy and ion‐beam erosion.
1,3‐asymmetric induction in stereoregular radical reactions
Authors: Englin B.
Published: June 2010

The radical telomerization reactions of vinyl chloride or propylene with halomethanes were chosen as stereochemical models for studying the mechanism of stereoregular polymerization of the monomers.

Conformational 1H‐NMR analysis was used to assign the relative configurations of the racemic diad and triad telomer forms. The assignment was based on comparisons of the CH2‐proton geminal shifts in molecular fragments ‐CHX‐CH2‐CHX‐ and rotational equilibria of the racemic forms measured by NMR spectroscopy over a wide temperature range in solvents with different dielectric and magneto‐anisotropic properties. Complete iterative analysis of 1H‐NMR spectra at 60 and 90 MHz was carried out by using the INDOR technique and the 1H‐{D} spectra of partially deuterated model compounds, synthesized from various mono‐ and dideuterosubstituted vinyl chlorides.

Statistical treatment of the distribution of the diad and triad forms allowed the stereochemical course of the propagating reactions of the 1,3‐substituted vinylic radicals to be determined at temperatures ranging from 55 to 200°C and pressures up to 8000 kg/cm2. From these statistical data and the conformational equilibria of the racemic diastereomeric forms, it was revealed that the stereoregularity of the studied and probably similar reactions with 1,3‐substituted vinylic radicals may be ascribed predominantly to the effect of the γ‐substituent. A dynamic model of a 1,3‐asymmetric induction and the mechanism of conformational control in stereoregular free‐radical polymerization is discussed.
Copolymerization of styrene and methyl methacrylate photosensitized by a methyl methacrylate‐triethylaluminium complex
Authors: Allen P. E. M. , Chiaramonte P. , Hunter L. J. , Mair C. , Williams E. H.
Published: June 2010

We have re‐examined the copolymerization of methyl methacrylate (MMA) and styrene in the presence of triethylaluminium at 273°K under visible light following recent claims that it was an alternating system. We applied gel‐permeation chromatography to establish that the polymers had monomodal distributions and could be regarded as coherent samples for analysis. Proton and 13C‐NMR spectroscopy were used to determine the composition and structure of the copolymers and investigate the presence of complexes in the comonomer solutions. We found that the polymers produced are not strictly alternating. In the absence of excess, uncomplexed MMA, the system is a radical copolymerization of styrene and a 1:1 MMA‐AlEt3 complex with reactivity ratios such that there is a strong tendency for styrene (S) and MMA (M) units to alternate. The alternating SMS triads were predominantly isotactic. Significant proportions of SSS, MMM and MMS triads could be detected.
ESR studies of degradation in polymers. I. γ‐irradiation of poly(styrene‐co‐methyl methacrylate) at 77°k
Authors: O'Donnell J. H. , Pomery P. J.
Published: June 2010

The ESR spectra, due to trapped radicals produced by γ‐irradiation at 77°K, of random copolymers of styrene and methyl methacrylate of known composition and of the two parent homopolymers have been studied at 77°K. The yields of trapped radicals in the polymers were measured at several doses by double integration of the ESR spectra, and the G values for the production of radicals were calculated. The G(R) value for poly(methyl methacrylate) was calculated as 0.58 ± 0.2 and that for polystyrene as 0.05 ± 0.02. The variation of G(R) is not linear with polymer composition and is explained by a protective effect of the aromatic component resulting from energy transfer. Other chemical reactions and scavenging effects can be eliminated by consideration of the results from the analysis of the ESR spectra of the copolymers in terms of the homopolymers. It appears that different transfer mechanisms become operable as the copolymers are warmed up after irradiation at 77°K.
Use of mono‐ and multifunctional oxocarbenium salts in the polymerization of tetrahydrofuran
Authors: Franta E. , Reibel L. , Lehmann J. , Penczek S.
Published: June 2010

Oxocarbenium ions associated to a stable counterion SbF6− were used to initiate the polymerization of tetrahydrofuran; mono‐, di‐, and trifunctional initiators were prepared. They proceed by addition onto the monomer with formation of an ester group and react quantitatively; initiation by the mono‐ and di‐functional salts is rapid. This kind of derivative was used in order to prepare block and graft copolymers of controlled structure.
New catalyst systems for the polymerization of isobutylene at “high” temperature based on dialkylaluminum halides and electron‐acceptor molecules
Authors: Cesca S. , Priola A. , Ferraris G. , Busetto C. , Bruzzone M.
Published: June 2010

Catalyst systems based on dialkylaluminum halides and electron acceptors, e.g., chloranil (CA), 1,3,5‐trinitrobenzene, 2,4,5,7‐tetranitrofluoren‐9‐one, etc., succeed in polymerizing isobutylene and co‐polymerizing it with isoprene to very high molecular weight products. The system Et2AlCl–CA was investigated in detail by studying the products resulting from the interaction of the components in the presence of monomer or of its model compounds, e.g., 2,4,4‐trimethyl‐1‐pentene or 1,1‐diphenylethylene, and also in their absence. The carbonyl group is the preferred site of attack by R2AlCl leading to hydroquinone derivatives, but the chlorine atoms of CA are not reactive under the conditions adopted. No relevant interactions between isobutylene and CA were evident by ultraviolet spectroscopy, whereas ESR investigations succeeded in detecting a clear signal at g = 2.005 lacking hyperfine structure and assigned to a semiquinone radical of CA. This paramagnetic species is quenched in the presence of isobutylene which is believed to be transformed into a radical‐cation species. A bicationic propagation mechanism, resulting from the coupling of the olefin radical‐cation, seems supported by the identification of 1,1,4,4‐tetraphenylbutadiene among the dimers of a model compound obtained under polymerization conditions.
Radiation‐ and photoinduced ionic polymerization
Authors: Hayashi Koichiro , Irie Masahiro , Yamamoto Yukio
Published: June 2010

Photoinduced polymerizations of α‐methylstyrene and styrene were carried out in the presence of electron acceptors. These polymerizations are proved to be initiated by radical, ion‐pair, or free ion formed through the photoexcited electron donor‐acceptor complex.

Radiation‐induced cationic polymerizations of styrene and α‐methylstyrene were found to proceed by free cationic propagation. The effect of added electron acceptors in these polymerizations was investigated. The role of ion‐pair in radiation‐induced cationic polymerization is investigated by the use of optical absorption method at 77°K and pulse‐radiolysis technique at room temperature.
The relation between thermal decomposition of polymers and free radical formation under high vacuum pyrolysis
Authors: Tkáč A.
Published: June 2010

The fragments of the thermal decomposition of polymers (240–350°C) are hot free radicals and biradicals that after volatilization under vacuum can be trapped on the surface of a rotating cryostat (−195°C). The reactivity of these radicals is studied in the temperature range of −170 to 0°C by means of electron spin resonance. The rate of reactive radicals formation seems to be the primary process on which the burning and inflammation properties of the polymers depend.
Influence of polymer structures on the rate constants of ultrasonic degradation in diluted solutions
Authors: Lueb H. A. , Schoon Th. G. F.
Published: June 2010

It was shown that polymers with a lower activation energy for thermal degradation (polystyrenes) are degraded faster by progressive periods of irradiation than those with higher activation energies (polybutadienes). Furthermore a connection is assumed between the degradation velocity and the effective rheological diameter of the tertiary units or the limiting molecular weights achieved with the standard mechanical degradation process. In addition, the value of the second virial coefficient, determined by the slope mo of the straight line in the graph ζ/c related to c, is relevant for the degradation velocity. The polymers with the largest second virial coefficient show the fastest degradation velocity constant K1, according to which it could be assumed that with the increase in interactions between solvent and soluted polymer, the degradation is accelerated.
Study of the effect of 2,4,6‐trisubstituted phenols on the theromoxidative stability of polypropylene by the chemiluminescence method
Authors: Matisová‐Rychlá L. , Ambrovič P. , Kulíčková N. , Rychlý J. , Holčík J.
Published: June 2010

The chemiluminescence method was used for the study of thermooxidation of polypropylene. An attempt was made to interpret the time‐reaction relationship of chemiluminescence. The influence of 2,4,6‐trisubstituted phenols containing different substituents on the course of polypropylene thermooxidation is also discussed.
Antioxidative properties of phenyl‐substituted phenols. III. Model studies of synergistic actions between primary and secondary antioxidants
Authors: De Jonge C. R. H. I. , Van Der Maeden F. P. B. , Biemond M. E. F. , Huysmans W. G. B. , Mijs W. J.
Published: June 2010

Products originating from the action of primary and secondary antioxidants can account, after interaction, for the synergistic effects observed in some polymers, e.g., polypropylene. Marked synergistic actions were observed between 4‐alkoxy‐2,6‐diphenylphenols and β,β′‐disubstituted diethyl sulfides. Using the corresponding phenoxyl radicals and sulfoxides as the model compounds, several products arise and disappear.

In the case of 4‐methoxy‐2,6‐diphenylphenoxyl and β,β′‐diphenyldiethyl sulfoxide, 4‐methoxy‐2,6‐diphenylphenol (the primary antioxidant) and the formation of a variety of sulfur compounds, capable of acting as peroxide decomposers, were detected, isolated, and identified using high‐pressure liquid chromatography (HPLC) as a separation technique followed by semipreparative isolation.
Intramolecular proton transfer in ortho hydroxybenzophenones
Authors: Klöpffer Walter
Published: June 2010

The photostability of UV stabilizers of the ortho hydroxybenzophenone type is discussed in terms of excited state proton transfer and radiationless transitions in the “phenol” and “quinone” tautomers. The first triplet state of the phenol form derived by quenching experiments is located between 22,000 and 20,090 cm−1. These limits of T1, together with published acidity data, suggest a deactivation cascade involving the triplet states. Nevertheless, very fast internal conversion cannot yet be ruled out as an alternative explanation for the high photostability of these materials.
Antioxidants and stabilizers. LXIII. Sensitized photooxidation of 2,2′‐methylenebis(4‐methyl‐6‐tert‐butylphenol)
Authors: Taimr L. , Pospišil J.
Published: June 2010

The photooxidation of 2,2′‐methylenebis (4‐methyl‐6‐tert‐butylphenol) (II) sensitized with methylene blue in methanol was investigated. The course of reaction is strongly influenced by the concentration of sensitizer and substrate. At a low concentration of methylene blue, bisphenol II is oxidized with singlet oxygen with the formation of hydroperoxide III, which is further oxidized to yield a mixture of diastereomeric hydroperoxides IVa and IVb. By raising the concentration of methylene blue this reaction is suppressed and bisphenol II is oxidized via the respective aryloxyl radicals gradually to methoxy derivatives VI, VII, and other products. Bisphenol II used in high concentration inhibits both the oxidation of bisphenol itself and that of other substrates. The effect can be compared with that of 1,4‐diazabicyclo(2,2,2)octane. The thermal decomposition of hydroperoxides III, IVa, and IVb leads to the regeneration of bisphenol II. The results provide a deeper insight into the knowledge of the formation of transformation products of antioxidants under the conditions of aging of polymers.
Antioxidants and stabilizers. LXI. Photochemical behavior of transformation products of phenolic antioxidants: 4‐tert‐butylperoxy‐2,5‐cyclohexadienone
Authors: Lerchová J. , Kotulák L. , Rotschová J. , Pilař J. , Pospíšil J.
Published: June 2010

The decomposition of 2,6‐di‐tert‐butyl‐4‐methyl‐4tert‐butylperoxy‐2,5‐cyclohexadienone (I) in n‐heptane solution irradiated with light having wavelengths of 333 nm and 436 nm and in the solid phase irradiated with solar light was investigated. The composition of the reaction mixture was studied by UV and IR spectrometry and chromatographically (gel permeation, thin layer). The radical species was recorded using the electron pulse resonance (EPR) method.
Specificity of the soled phase oxidation of polyolefins
Authors: Buchachenko A. L.
Published: June 2010

The kinetics and mechanism of elementary chemical reactions in solid polymers are reviewed. The activation energies and pre‐exponential factors of propagation and recombination rate constants are analyzed. The mechanism of hydroperoxide decomposition and chain branching are critically considered and the influence of oxygen on the chain branching probability is discussed. Some other problems of solid polymer oxidation are also discussed.
Morphology and mutual dependence of lamellas in bulk and oriented linear high polymer samples
Authors: Point J. J.
Published: June 2010

This paper discusses the morphology of individual lamellar crystals of semicrystalline linear high polymers in the bulk or oriented states. We discuss the simple two‐phase model, the model where the folds are level, and intermediate models. We also discuss the dependence of lamellas upon each other caused by the chains and fibrils which connect the crystals and the coalescence of the disordered parts of the lamellas.