bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of two polypentadienes of differing tacticity by physical methods
Authors: Fielding‐Russell G. S. , Smith G. H.
Published: April 2003

The preparation of isotactic and syndiotactic 1,4‐polypentadienes with a cis content of at least 70%–75% using i‐Bu2AlH/Ti(i‐OPr)4 and AlEtCl2/thiophene/Co(acetylacetonate)2 catalysts, respectively, is reported. Physical characterization of the vulcanizates, prepared by a common recipe, involving infrared analysis, DTA, simple stress–strain and swelling measurements, and dynamic mechanical measurements over a frequency range of 2 decades and temperature range of −60°C to +20°C indicated that no isomerization had taken place during vulcanization and that stereoregularity of the polymer chains affected the resultant cure: the isotactic form was found to have a greater crosslink density than the syndiotactic form. Master curves covering an extended frequency range were constructed from the reduced dynamic mechanical data and the calculated quantities—thermal expansion coefficients of free volume and the fractional free volumes at the glass transition temperatures—agree with the accepted values. Glass transition temperatures of the isotactic and syndiotactic polymers are −37°C and −42°C, respectively, and for their vulcanizates, −33°C and −40°C, respectively.
Stress–birefringence study of styrene–butadiene multiblock copolymer
Authors: Nishioka A. , Furukawa J. , Yamashita S. , Kotani T.
Published: April 2003

The styrene–butadiene block copolymers of SB, SBS, and SBSBS types were investigated by means of the stress–birefringence technique to elucidate the effects of the block multiplicity on the mechanical properties of copolymers. The SBS‐type and the SBSBS‐type block copolymers exhibit nonlinear stress–birefringence relations, which were classified into three regions. They are a low stress‐optical coefficient region (optical creep), an increasing coefficient region, and a region of retarded increase in coefficient, as pointed out by Henderson et al.8 It was found that optical creep is associated with the polystyrene continuum. The third region, however, originates not only from the phenyl groups of the polystyrene block but also from a form‐birefringence due to the orientation of the polystyrene domain. The multiblock copolymer of SBSBS type was found to be rheo‐optically similar to the SBS type, both being affected solely by the details of the terminal styrene block.

Pure gum vulcanizates of the SB‐type and SBS‐type block copolymers also exhibit optical creep. In a vulcanized block copolymer having both chemical and physical crosslinks, the latter seemed to disappear at elevated temperatures. At decreasing temperatures, the vulcanizates of block copolymers showed higher modulus of elasticity and lower stress‐optical coefficients.
Molecular weights of grafted polystyrene onto γ‐preirradiated cellulose diacetate
Authors: Munari Stelio , Tealdo G. Carlo , Canepa Giacomo , Rossi Corrado
Published: April 2003

The behavior of molecular weights of grafted polystyrene onto γ‐preirradiated cellulose diacetate was studied. The grafting of styrene onto cellulose diacetate was kinetically followed with particular attention paid to the polystyrene molecular weight behavior. The molecular weight was evaluated with the polymer fractions obtained by acid hydrolysis of the grafted copolymer. From the experimental results it appeared that the grafted chain molecular weight is completely controlled by the physical properties of the polymeric matrix either during a “bulk” or a “front” grafting.
Graft copolymerization to cellulose. Effect of sodium thiosulfate on hydrogen peroxide initiator system
Authors: Ogiwara Yoshitaka , Kubota Hitoshi
Published: April 2003

The effect of sodium thiosulfate on the graft copolymerization of methyl methacrylate to cellulose in the hydrogen peroxide initiator system was investigated. The addition of sodium thiosulfate in general was effective for decreasing the per cent grafting and the average molecular weight of grafts and increasing the formation of homopolymer, and the effects became pronounced with increasing hydrogen peroxide concentration. Moreover, the addition of sodium thiosulfate slightly suppressed the formation of grafts at a hydrogen peroxide concentration of 3 mmole/l., but greatly promoted it at 20 mmole/l. Traces of metallic ions present in cellulose could not be eliminated sufficiently by treatment with 3N hydrochloric acid. Such ions were found to interact with hydrogen peroxide and thus participate directly in the initiation and termination of the polymerization reaction. EDTA, the chelating agent, was highly effective for suppressing such participation of metallic ions. In the hydrogen peroxide initiator system applied to the EDTA‐treated samples, sodium thiosulfate caused an effective initiation of graft formation.
The determination of unsaturation in ethylene propylene terpolymers and butyl rubber with pyridinium bromide perbromide
Authors: Tunnicliffe Marjorie E.
Published: April 2003

The reagent pyridinium bromide perbromide (PBPB) has been investigated for the determination of unsaturation in model olefins and in polymers of low total unsaturation. Model olefins give 92%–100% reaction for a 1‐hr reaction period. Ethylene propylene terpolymers react quantitatively without substitution or elimination and without second addition reactions when the termonomer unit is 1,4 hexadiene, methylene norbornene, ethylidene norbornene, or cyclooctadiene. Dicyclopentadiene terpolymers react incompletely. These reactions take place in carbon tetrachloride/10% methanol solution, the reagent being added as a methanolic solution. Iodine chloride can also be used under specified conditions for the more reactive termonomer units in this solvent mixture. Under the same conditions the PBPB reagent reacts stoichiometrically with butyl rubber, without second addition or substitution reactions. The unsaturation results also agree with those obtained using bromine or iodine monochloride in carbon tetrachloride solution, but both of these reagents give slight substitution reactions.
The solubility parameter concept applied to disperse dyeing of polymers
Authors: Ibe E. Chianakwalam
Published: April 2003

The solubility parameter concept offers a logical link between the theory of solutions and of nonionic (disperse) dyeing. An attempt has been made to apply the concept to correlate the solubility of several disperse dyes in secondary cellulose acetate, cellulose triacetate, and polypropylene with the calculated solubility parameters of both the polymers and the dyes. When the dyes are applied on hydrophilic polymers from an aqueous dispersion, the correlation between the solubility parameter concept and the dye solubility is not close. One of the reasons for this may be the fact that dyeing of the fibers is, in fact, not a solution in the dry fibers, but consists essentially either in displacement of water molecules from the water swollen fibers and/or, perhaps, in additional swelling by the dye. Consideration of this fact and also correcting for the contribution of hydrogen bonding and dipole interactions to the cohesive energy density brings the disperse dye solubility data into a better agreement with the concept. The concept should be applicable without complications to the dyeing of nonpreswollen fibers, such as polypropylene from aqueous dispersion, or any fiber by the Thermosol process and particularly to dyeing from the vapor phase. The few data available appear to support this view.
Ultraviolet absorbers. The protective ability of aromatic nitro compounds in plasticized poly(vinyl chloride)
Authors: Raciszewski Zbigniew , Mullins D. H.
Published: April 2003

Investigated were three types of aromatic nitro compounds: (a) a derivative of o‐nitrophenol capable of forming an intramolecular hydrogen bond, (b) simple aromatic nitro compounds, and (c) the intramolecular charge transfer complexes, i.e., compounds incorporating in a single molecule the donor and the acceptor moieties, the latter substituted with the nitro groups. Samples of plasticized poly(vinyl chloride) were stabilized with these compounds and tested in an Atlas Weatherometer. The extent of degradation was determined by measuring the tensile strength, elongation, and the blue light reflectance before and after 270 and 500 hr of exposure. Samples without the stabilizers and samples containing 2,4‐dihydroxybenzophenone were used as standards for comparison. Little protection was provided by simple nitro compounds. The derivative of o‐nitrophenol and the donor‐acceptor compounds were either better or comparable to 2,4‐dihydroxybenzophenone in preserving the tensile strength and elongation. It appears that the protective ability of the derivative of o‐nitrophenol was associated with the hydrogen‐bonded six‐membered ring whereas the protection rendered by the donor‐acceptor compounds was determined by the extent of the contribution of the charge transfer states and the number of benzylic hydrogens capable of undergoing photochemical reactions. However, the mechanistic interpretation of the protective ability of the donor‐acceptor compounds was complicated by the color changes occurring during the exposure.
Gelation of poly(ethylene oxide) solutions by gamma radiation: Effects of molecular weight and irradiation conditions
Authors: Van Brederode R. A. , Rodriguez F.
Published: April 2003

Reticulation of a dilute aqueous solution of poly(ethylene oxide) in a 60Co gammaradiation field yields a weak gel which is characterized by its damped sinusoidal oscillation in a free‐swinging torsion pendulum. A storage and a loss modulus are calculated from the log decrement and frequency of oscillation, and the crosslink density is obtained from the storage modulus using the kinetic equation of rubber elasticity. The number of crosslinks added to the polymer per 100 eV of energy absorbed in the polymer above and below the gel point and the fraction of gamma energy absorbed directly by the polymer were determined from the dose‐to‐gel and modulus data. The effect of oxygen on the crosslinking reaction and the temperature on the gel's mechanical properties were experimentally observed.
The kinetics of thin film polyesterification
Authors: Campbell Gregory A. , Elton Edward F. , Bobalek Edward G.
Published: April 2003

The goal of this work was to investigate the increase in the rate of polyesterification that takes place as surface‐to‐volume ratio is increased. The polymer used in this reaction was derived from the esterification of adipic acid (hexanedioic acid) and propylene glycol (1,2‐propanediol). The effect of three variables—film thickness, water concentration of the nitrogen atmosphere, and temperature—was studied to determine their effect on the reaction rate. The water content of the atmosphere was found to severely retard the progress of the esterification and this fact reaffirms that the reverse reaction, hydrolysis, is much more important than was realized by earlier investigators. The reaction in the film was found to have an activation energy of 22,600 cal/mole compared to 12,600 cal/mole in the batch reaction, indicating a possible change in controlling rate from the batch to the film system. New evidence was found which illustrates the possible role of reactant mobility at high conversions. It is suggested that a possible explanation for the change in controlling rate may be due to a complex surface phenomenon such as the alignment of reactive groups at the surface or the orientation of water molecules at the gas–liquid interface.
Polyquinoxalines. I. Synthesis and preliminary mechanical properties as laminating and adhesive resins
Authors: Hergenorther P. M. , Levine H. H.
Published: April 2003

A study on polyquinoxaline synthesis was conducted which provided a method of obtaining processable, reproducible high molecular weight polymers as solutions in m‐cresol; these solutions had excellent storageability at ambient temperatures. Polyquinoxaline solutions in m‐cresol were readily used for prepreg and tape preparation. Laminate and adhesive data showed the excellent potential of the polyquinoxalines for high temperature applications.
Thermal decomposition of phenol formaldehyde resins modified with cyanuric acid
Authors: Alaminov H. , Andonova N.
Published: April 2003

The thermal decomposition of cured cyanurophenol—formaldehyde oligomers (CPFR) was studied by derivatography, IR, spectra and EPR spectra. During the heating of CPFR, processes of restructuring and decomposition take place. Up to 330°C the weight losses of CPFR are smaller compared to those of phenol–formaldehyde oligomers (PFR), while above 330°C the opposite is true. Under these conditions the isocyanuric ring is destroyed. The carbonyl absorption sharply decreases at 400°C, and at 500°C there is practically no absorption. This reduction is probably a result of rearrangement of the isocyanuric rings to a secondary polymer in which nitrogen is combined in the form of cyanic links. The energy of decomposition as determined from the thermogravimetric curve is 17 to 24 kcal/mole. On the basis of the EPR sepctra and the low activation energy of destruction, we propose that radical processes play an important part during the process of curing and thermal decomposition of CPFR.
Effects of monomer impurities on the emulsion polymerization of chloroprene and properties of polychloroprene. II. Effect of monovinylacetylene
Authors: Sufčák Miloslav
Published: April 2003

The free‐radical emulsion polymerization of chloroprene containing monovinylacetylene in concentrations from 0% to 10% has been studied. It was found that in the presence of monovinylacetylene, a polymer with a great gel content, increased values of plasticity, and deteriorated physical and mechanical properties is formed. Monovinylacetylene has been proved to copolymerize with chloroprene under the conditions used. Acetylenic groups remain unchanged in the copolymer; they cause the crosslinking of polychloroprene macromolecules and corresponding changes in polymer properties. Copolymerization reactions of monovinylacetylene with chloroprene together with the crosslinking effect of monovinylacetylene cause a substantial lowering of the crystallization rate of polychloroprene.
Predicting joint sealant performance of elastomers by computer simulation. I. Justification of method
Authors: Catsiff E. H. , Hoffman R. F. , Kowalewski R. T.
Published: April 2003

A computerized method has been developed for the analysis of the behavior of a sealed joint. The method is based upon the use of fundamental time‐dependent mechanical properties of a polymeric sealant, which can be easily determined in the laboratory, to feed a digital computer program that performs internal force balances within a given joint seal configuration by dividing the joint seal into a large number of “finite elements” in which the sealant properties are invariant. The computational method is an outgrowth of stress analysis programs that have been developed for use in the study of stress distributions within solid rocket propellant “grains.” Output from the computer program consists of a prediction of the overall geometric deformation of the sealant and the distribution of stresses and strains within the joint seal. Essential to the ideologic development of this method is the “separability” of time‐dependent and strain‐dependent aspects of the behavior of the material properties. However, the method should be operable even when this “separability” is only approximately maintained, as in many real materials. Fundamental properties have been determined on several typical sealant materials. A description is given of the mode of operation of the computational method, but detailed results are given in a companion article.
Predicting joint sealant performance of elastomers by computer simulation. II. Results in simple extension and compression
Authors: Catsiff E. H. , Hoffman R. F. , Kowalewski R. T.
Published: April 2003

Stress computations have been performed by a technique based on the subdivision of a body into many quasi‐homogeneous elements of a material having separable time‐dependent and strain‐dependent mechanical properties. For several sealant materials and joint seal shapes, under simple tension and/or compression movements, results are compared to experimental data on model sealed joints. There is reasonable agreement between the predicted and experimental total stress in joint seals of all the sealants tested up to nominal joint deformations of about 20%–40%. Furthermore it has been shown that the strain distribution in the outer layer of the sealant is nonuniform and the deformed shape is nonparabolic, which disagrees with the assumptions of the joint seal analysis proposed by E. Tons. The nonparabolic deformations have been experimentally confirmed using a resin‐casting technique to “freeze” the deformed joint seal to permit measurement of its shape. The computed stress and strain distributions show that the stresses are highest near the corners of the joint seal and are directed at an acute angle to the substrate, indicating that the peel strength of the sealant plays a major role in determining the overall joint strength. It has been shown how the computational technique can be applied to alternate compression and tension cycles to predict some effects of polymer stress relaxation characteristics on the stress distributions. Although the computational method has only been applied to a few representative isothermal sealed‐joint systems under relatively simple loading conditions, the technique certainly has been shown to be feasible for predicting stresses within a seal over a reasonable range of nominal joint deformations. It is expected that the technique can be extended to more complex joint motions by modification of the computer programs and the input of additional data on actual joint movements. Work is in progress to extend the method in this direction and should lead to a more rational approach to sealant specifications and selection as well as improvements in joint seal designs.
Copolymerization of ethylene oxide and propylene oxide by anhydrous potassium hydroxide
Authors: Rastogi Anil K. , St. Pierre Leon E.
Published: April 2003

Ethylene oxide and propylene oxide have been copolymerized at low temperatures in the presence of anhydrous potassium hydroxide. The monomer reactivity ratios were found to be r(ethylene oxide) = 6.5 and r(propylene oxide) = 0.5.
The stress birefringence of vulcanizates of polyisoprene–polyethylene blends
Authors: Nishioka A. , Furukawa J. , Yamashita S. , Kotani T.
Published: April 2003

As a model for the vulcanizates of block copolymers, mixtures of polyisoprene and polyethylene vulcanized both with a peroxide and with sulfur were investigated by stress birefringence. It was found that the polyethylene dispersion showed a reinforcing effect only in the peroxide vulcanizates. On the other hand, the stress birefringence was decreased with increased polyethylene content except at high polyethylene content. In the latter case, the slope of the line in the birefringence–stress plot was almost equal to that for the pure polyisoprene vulcanizate at high stress levels. However, at lower stresses significant optical creep was observed, i.e., the stress increased without bire‐fringence. Such an optical creep as this exists also in styrene–butadiene block copolymer. These facts are interpreted by the assumption that polyethylene dispersion, when it is linked chemically with polyisoprene matrix, acts as a reinforcing agent by forming physical crosslinks similar to the hard domains in block copolymers. Such physical crosslinks can slip during elongation, resulting in the observed optical creep. These phenomena disappear at the elevated temperature.
Multiple peak resolution in gel permeation chromatography
Authors: Schrager M. , Ward A. L.
Published: April 2003

A new, graphic method of the resolution of a chromatogram into its component peaks is presented. From a mathematical description of the chromatogram of a monodispersed sample, a practical method of peak resolution of a multicomponent sample is derived. From this, the constituents may be characterized as to size and their weight fractions determined. As an example the final product in the synthesis of N,N‐diglycidyl tribromoaniline is analyzed graphically and compared with results obtained using the du Pont 310 Curve Resolver. The agreement appears to be quite satisfactory.
Yielding processes in glassy polymers
Authors: Zitek P. , Zelinger J.
Published: April 2003

Our contribution deals with a description of yield in glassy polymers, being treated as an activated process. For description the Eyring equation in simplified form has been selected:

where σy = yield stress, T = absolute temperature, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon = {\rm deformation (strain) rate,}$\end{document} and A, B, C = equation parameters. In the first part the applicability of this equation has been verified by applying data of our own as well as those published elsewhere. For a more comprehensive representation of the results the data were processed in the form of generalized master curves by using the appropriate shift factors derived from eq. (1).
Aminothiol polyalkylene sulfide oligomers
Authors: Woodhams R. T. , Adamek S.
Published: April 2003

The carbonates and oxides of zinc and cadmium polymerize propylene sulfide to elastomeric materials, but with the addition of ammonia low molecular weight polymers are produced. The effect of the ammonia is to react with some of the propylene sulfide to give aminopropanethiol, which will itself polymerize monomer by a stepwise reaction or, after reaction with the metal carbonate, form a metal bis(aminopropanethiolate) which is an active initiator. Chemical and spectroscopic examination of these polymers shows them to be essentially bifunctional, with one NH2 and one SH terminal group. There is, however, evidence to suggest that further reaction of monomer occurs with the terminal amine groupings to give polyfunctional compounds. From the relative proportions of ammonia, zinc carbonate, and monomer, the rate of polymerization, molecular weight, and degree of endgroup coordination with catalyst residue can be controlled as desired. Due to the highly reactive endgroups, the polymers are readily crosslinked with epoxy resins, aziridinyl compounds, and hexamethoxymethylene melamine to give useful products exhibiting high solvent resistance.
Etude par résonance magnétique nucléaire des polychlorures de vinyle polymérisés par les systémes titanate de butyle–alcoyles‐aluminium
Authors: Pham Q. T. , Rocaniere P. , Guyot A.
Published: April 2003

NMR analysis of the chain ends of samples of poly(vinyl chloride) prepared using a Ti(OBu)4–alkylaluminum system in CCl4 reveals that the mechanism of the formation of free radicals depends on whether the alkylaluminum used is chlorinated or not. In the first case, some of the radicals are reactive in the initiation step of the polymerization, while in the latter case theses radicals first undergo transfer to CCl4, then the CCl3· formed initiates the polymerization of vinyl chloride. The poly(vinyl chloride) radicals are chiefly stopped by transfer to CCl4 (chlorine abstraction) or to alkylaluminum (hydrogen abstraction). In transfer reactions between growing radicals and alkylaluminum, the radicals formed have to react with CCl4 before reinitiating the polymerization of vinyl chloride.
High flux freeze‐dried cellulose acetate reverse osmosis membranes as microporous barriers in gas permeation and separation
Authors: Agrawal J. P. , Sourirajan S.
Published: April 2003

The permeations of helium, hydrogen, methane, ethylene, nitrogen, and argon, and helium–methane, nitrogen–ethylene, oxygen–nitrogen, and sulfur dioxide–nitrogen mixtures have been studied using freeze‐dried porous cellulose acetate reverse osmosis membranes. The results illustrate the existence of mobile and immobile sorbed layers and the governing influence of surface flow in gas‐phase reverse osmosis separations. Preshrunk freeze‐dried porous cellulose acetate membranes seem to offer a practical means of utilizing the reverse osmosis process for recovering helium from natural gas and separating sulfur dioxide from flue gases.
Crosslinked poly(hydroxyethyl methacrylate) membranes for desalination by reverse osmosis
Authors: Jadwin T. A. , Hoffman A. S. , Vieth W. R.
Published: April 2003

A series of crosslinked hydroxyethyl methacrylate (HEMA) membranes for reverse osmosis desalination has been prepared. The crosslinkers used were trimethylol propane trimethacrylate (TPT) or ethylene glycol dimethacrylate (EGD). Membranes were synthesized by polymerizing the monomers as a thin homogeneous film. In addition to reverse osmosis tests, the membranes were also characterized by osmosis experiments and sorption measurements. The reverse osmosis water flux (1500 psi applied pressure, 4% NaCl brine, pH = 5) for these membranes decreases from 0.6 gallonmil/ft2‐day (GMFD) to 0.055 GMFD and salt rejection increase from 78% to a maximum of 94% as the amount of TPT is increased from 0 to 11 mole‐%. Water contents decrease from 42% to 15% over the same range of crosslinker, but the preferential sorption of water to salt does not vary. Thus, rises in reverse‐osmosis semipermeability were found to result from changes in water–salt diffusivity ratios. The mechanism of permselectivity has been interpreted in terms of parallel diffusive fluxes across the membrane of primary H‐bonded water and secondary water plus salt ions.
The dependence of the rate of emulsion polymerization of methyl methacrylate on the soap concentration
Authors: Lee P. I. , Longbottom H. M.
Published: April 2003

The dependence of the rate of emulsion polymerization of methyl methacrylate on the concentration of sodium dodecyl sulfate has been studied using the Mx+–N2H5OH system as initiator (where Mx+ is Cu2+, Fe3+, and Mn3+). It was found that the rate dependence on soap concentration was different for each initiator. The extent of this variation was:

The variation is large enough to show that the dependence of the rate of emulsion polymerization on soap concentration is not simply a function of the solubility of the monomer in water, as had been suggested by Gershberg.
Environmental stress relaxation studies of polymers: Effect of temperature on polyethylene–xylene and polyethylene–toluene systems
Authors: Nisizawa Mizuho
Published: April 2003

The method of stress relaxation has been used to study the effect of temperature on the stress decay behavior in the systems of polyethylene–xylene and polyethylene–toluene. The behavior of stress decay in the polyethylene under xylene or toluene at various temperatures was observed and the activation energies of polyethylene–xylene and polyethylene–toluene were obtained.
Structural characterization of vulcanizates. XI. Network‐bound accelerator residues
Authors: Campbell D. S.
Published: April 2003

Radiotracer techniques have been used to determine amounts of accelerator which become bound to the vulcanizate networks during the vulcanization of NR with sulfur and CBS. Three different vulcanization systems have been studied, having different proportions of accelerator to sulfur. The vulcanizates have also been characterized in terms of the numbers and types of chemical crosslinks present and the results of the bound accelerator analyses have been considered in relation to the crosslink levels and distribution.
Dynamic mechanical properties of particulate‐filled composites
Authors: Lewis T. B. , Nielsen L. E.
Published: April 2003

The relative shear moduli of composites containing glass spheres in a rubbery matrix obey the Mooney equation, analogous to the relative viscosity of similar suspensions in Newtonian liquids. However, when the matrix is a rigid epoxy, the relative shear moduli are less than what the Mooney equation predicts but greater than what the Kerner equation predicts. Relative moduli are less for rigid matrices than for rubbery matrices because (1) the modulus of the filler is not extremely greater compared to that of the rigid matrix; (2) Poisson's ratio is less than 0.5 for a rigid matrix; (3) thermal stresses in the matrix surrounding the particles reduce the apparent modulus of the polymer matrix because of the nonlinear stress—strain behavior of the matrix. This latter effect gives rise to a temperature dependence of the relative modulus below the glass transition temperature of the polymer matrix. Formation of strong aggregates increases the shear modulus the same as viscosity is increased by aggregation. Torsion or flexure tests on specimens made by casting or by molding give incorrect low values of moduli because of a surface layer containing an excess of matrix material; this gives rise to a fictitious increase in apparent modulus as particle size decreases. The mechanical damping can be markedly changed by surface treatment of the filler particles without noticeable changes in the modulus. The Kerner equation, which is a lower bound to the shear modulus, is modified and brought into closer aggrement with the experimental data by taking into account the maximum packing fraction of the filler particles.
Combined stress failure tests for a glassy plastic
Authors: Broutman L. J. , Krishnakumar S. M. , Mallick P. K.
Published: April 2003

The development of a unique test method for biaxial stress experiments on brittle material is discussed. Results of biaxial tension‐tension and tension‐compression experiments on poly‐methylmethacrylate (plexiglas) are presented. The strength results compare reasonably well with modified distortion energy theory in the tension‐compression stress quadrant.
Copolymerization of styrene. IV. Copolymerization with esters of benzylidenecyanoacetic acid
Authors: Gilath Arie , Ronel Samuel H. , Shmueli Mirjam , Kohn David H.
Published: April 2003

Styrene was copolymerized in bulk with a number of esters of benzylidenecyanoacetic acid. The kinetic scheme of all pairs fitted the improved scheme of copolymerization, taking into account the effect of the penultimate unit. The Alfrey‐Price Q and e values were calculated. Using the modified Taft equation, log (1/r1) = ρ*σ* + δEs, it was found that the relative reactivities of the ester monomers toward the polystyryl radical were correlated by the polar substituent constants σ* of the ester alkyl groups (ρ* = 0.14) and not by their steric substituent constants Es (δ = 0.008).
A dilatometer for measuring compressibilities of polymers in their melting range
Authors: Waldman N. , Beyer G. H. , Griskey R. G.
Published: April 2003

A dilatometer was developed for studying the compressibility of polymers in their melting range at pressures to 8500 atm and temperatures to 370°C. Temperature was controlled to ±0.01°C and pressures were maintained and controlled by means of a hydraulic deadweight gauge system. The device was sensitive to volume changes of 1 part in 30,000.
An analytical solution to Tung's axial dispersion equation. Applications in gel permeation chromatography
Authors: Hamielec A. E.
Published: April 2003

Equations developed for correcting Mn, Mw, and [μ] for imperfect resolution are generally satisfactory. Choosing the appropriate instrumental spreading function is however a very difcult task. There is need for further research on this problem, in particular with polymer standards for which the DMWD or even Mz is known (in addition to Mn and Mw).

A criterion for resolution in GPC which is based on a solution of Tung's axial dispersion equation has been proposed.

The operation of GPC in recycle mode appears very promising. Equations have been developed to interpret data obtained in this operational mode. It is probable that a great deal of work will be done in this area in the very near future.
The solubility of poly(vinylidene chloride)
Authors: Wessling Ritchie A.
Published: April 2003

The relative abilities of various solvents to dissolve crystalline polyvinylidene chloride were judged by comparing temperatures at which dilute suspensions became homogeneous. PVDC is not soluble in common solvents at ambient temperatures. It dissolves in solvents of matching solubility parameter only above ∼130°C. An analysis of the data suggests that δ = 10.1 for PVDC. Five classes of specific solvents were observed that could dissolve PVDC at much lower temperatures. These include sulfoxides, dialkyl amides, alkyl lactams, cyclic sulfides, and cyclic ketones. PVDC acts as a weak Lewis acid in these solutions. The best solvents found, in order of decreasing activity, are: hexamethylphosphoramide, tetramethylene sulfoxide, N‐acetylpiperidine, N‐methylpyrrolidone, N‐formylhexamethyleneimine, and trimethylene sulfide.
The diffusion of nonionic penetrants in polyamide
Authors: Shibusawa Takao , Iijima Toshiro
Published: April 2003

The diffusion behavior of nonionic penetrants in aqueous solution into nylon 6 was examined in the temperature range 5°–95°C. The Arrhenius plot of the diffusion coefficients is linear and its slope changes at 30–40°C higher than the glass transition temperature in water, as determined by dilatometry and viscoelastic measurements. The results are discussed in relation to the molecular size of the penetrant and the segmental motion of polymer chains.
ESR study of intramolecular energy transfer in the radiolysis of cellulose furoates
Authors: Singh Sujan , Hinojosa Oscar , Arthur Jett C.
Published: April 2003

The substitution of 2‐furoyl, 5‐methyl‐2‐furoyl, 2‐furanacryloyl, or 5‐bromo‐2‐furoyl groups on fibrous cotton cellulose increased the radiation rsistance of cellulose, as indicated by the retention of strength of the modified fibrous cellulose at high dosages of γ‐radiation compared with that of irradiated, unmodified fibrous cellulose. The presence of electropositive or electronegative substituents on the furan groups did not significantly change their radioprotective effects for cellulose. Electron spin resonance (ESR) spectra of irradiated celluloses indicated that the long‐lived free radical sites were similar, if not the same, in both irradiated, unmodified, and modified celluloses. The radio protective effects of furan groups for cellulose were attributed to absorption of energy from the secondary radiations, primarily the secondary electrons, by the groups due to their π‐electron‐type structures. The absorption of energy by the groups apparently decreased the localization of energy on carbon C1 or C4 on the cellulose molecule which would result in depolymerization and loss in breaking strength of the fibrous cellulose. The radioprotective effects of furan groups for cellulose were similar to those of benzenoid groups.
Studies on melt spinning of nylon 6. I. Cooling and deformation behavior and orientation of nylon 6 threadline
Authors: Ishibashi Tohru , Aoki Kiyoshi , Ishii Tsuneo
Published: April 2003

The melt spinning of nylon 6 filament yarns was studied by measuring the filament tensions at the takeup roll, the filament temperatures θ(x), filament diameters d(x), and birefringence Δn(x) as functions of distance x from the spinneret, and by observing how the molecular orientation was affected by these differences in cooling and thinning. Results were as follows: The thinning of the filament line, d(x), is affected little by the spinning temperature or by the degree of polymerization of the yarns taken up; it however depends heavily on the takeup speed VTu and the rate Q of production. Trouton viscosity β(T) as a temperature function derived from these experiments on nylon 6 is expressed consistently by the equation β ≑ 0.34 exp (3250/T), where T is absolute temperature. Nylon 6 filaments exhibit higher Trouton viscosity values than polyester or polypropylene filaments under the same spinning temperature. Filament temperature θ(x) versus distance x agreed well with theoretical values. The speed of molecular orientation was highest in the temperature range from 120°C to 40°C (the latter being the glass transition temperature of nylon 6). Furthermore, the larger the time rate of polymer deformation and the longer the residence time of polymer in the above temperature range, the higher was the orientation of the filament yarns taken up.
A comparison of some imidazole catalysts as epoxy curing agents
Authors: Dearlove Thomas J.
Published: April 2003

Some physical properties of epoxy resins cured with 2‐substituted imidazoles, e.g., 2‐ethyl‐4‐methylimidazole (EMI‐24), and 1‐substituted imidazoles, e.g., 1‐methylimidazole (MI‐1), were studied in order to determine the effect of additional crosslinking that has been proposed to occur with EMI‐24. While these catalysts were found to yield identical physical properties in that system, they were found to behave differently when the epoxy resin was flexibilized with a polysulfide rubber. Evidence from infrared (IR) and nuclear magnetic resonance (NMR) spectra proved that imidazoles unsubstituted in the 2‐position were being deactivated through their conversion to a dihydroimidazole compound in a proportion related to the amount of polysulfide rubber present. Hence, only imidazoles substituted in the 2‐position will cure epoxy–polysulfide rubber systems.
Radiation‐convertible polymers from norbornenyl derivatives. Crosslinking with ionizing radiation
Authors: Colomb H. O. , Trecker D. J. , Osterholtz F. D.
Published: April 2003

Vinyl polymers with pendant norbornenyl (bicyclo[2.2.1]heptenyl) groups crosslink rapidly on exposure to ionizing radiation. Analysis (according to Charlesby‐Pinner theory) of extraction data from an ethylene–vinyl acetate copolymer and the corresponding ethylene–vinyl norbornenecarboxylate copolymer shows that the unsaturated polymer crosslinks by a chain reaction. At low doses, the kinetic chain length is about 4. Pendant norbornenyl groups accelerate crosslinking of a vinyl alcohol–vinyl acetate–vinyl chloride copolymer and convert poly(vinyl alcohols) and cellulose acetate from degrading to crosslinking polymers. A novel application of the Charlesby‐Pinner plot strongly suggests linear dependence of the extent of crosslinking on the norbornenyl group concentration in a series of modified poly(vinyl alcohols). The greater effectiveness of pendant norbornenyl groups, compared to cyclohexenyl groups, demonstrates the importance of the reactivity of the double bond.
The preparation of some block copolymers
Authors: Black P. E. , Worsfold D. J.
Published: April 2003

The reactivity of the double bonds in p‐divinylbenzene toward anionic reagents is much greater than is the residual double bond in the divinylbenzene unit incorporated in a polymer chain. Thus it is possible to add to a “living” polymer a few divinylbenzene units before appreciable crosslinking occurs. Each of these units will have a vinyl group conjugated with a phenyl ring and will be comparable in reactivity to styrene. If the reaction is stopped at this point by the addition of methanol, the molecular weight of the product is essentially that of the original living polymer. These polymers may then be copolymerized through these active double bonds with any monomer with which styrene may be copolymerized, to form block or graft‐like copolymers. The copolymerizations may be effected by any of the methods applicable to styrene, i.e., free radical, cationic, or anionic. Such copolymerizations have been attempted with methyl methacrylate, butyl acrylate, vinyl chloride, vinylidene chloride, vinyl acetate, butadiene, isobutene, and propene, usually successfully.
Pyrolysis and combustion of cellulose. I. Effects of triphenyl phosphate in the presence of nitrogenous bases
Authors: Hendrix James E. , Bostic James E. , Olson Edward S. , Barker Robert H.
Published: April 2003

The ability of selected phosphorus‐containing compounds and nitrogen‐containing compounds to act as flame retardants for cotton cellulose was investigated using flame tests, thermal gravimetric analysis (TGA), and differential thermal analysis (DTA). The effectiveness of the organophosphorus compounds was found to correlate with the changes which they induced in the pyrolytic degradation of the cellulose as indicated by DTA. Many of the samples containing nitrogen were found to exhibit DTA curves having pronounced exotherms. The presence of nitrogen‐containing compounds in conjunction with the organophosphorus systems enhanced their ability to retard flame propagation but did not produce significant changes in the pyrolytic endotherm as observed by DTA. More conclusive evidence for a chemically based phosphorus‐nitrogen synergism was obtained by the use of TGA. These data can be interpreted in terms of the phosphorus‐nitrogen synergistic effects and flame retardance mechanisms which have been proposed in the literature.
Procedure for calculating the crystallinity of ethylene–vinyl acetate copolymers and low‐density polyethylene as a function of temperature
Authors: Barlow A. , Young M.
Published: April 2003

A method is described for determining the x‐ray crystallinity of ethylene–vinyl acetate copolymers at differing temperatures. An equation is derived for the symmetrical curves of crystallinity versus temperature thus obtained, from which the crystallinity at any temperature can be calculated. In order to determine the constants of the equation for a particular polymer, it is only necessary to determine the melting point and per cent crystallinity of the resin at a known temperature. The equation can also be applied to conventional polyethylenes, but not to linear polyethylenes. It is suggested that this is due to the former resins having a broad crystallite size distribution compared with the narrow distribution present in high‐density polyethylene.
Degradation of poly(vinyl chloride). I. Kinetics of thermal and radiation‐induced dehydrochlorination reactions at low temperatures
Authors: Palma G. , Carenza M.
Published: April 2003

The dehydrochlorination reaction arising thermally and from exposure to γ‐radiation has been followed, under vacuum, in the temperature range from 80° to 130°C by measuring the pressure of the evolved volatiles. The catalytic action of HCl, which was recently established, has been observed also at these low temperatures. In agreement with previous data, a free‐radical mechanism has been accepted to be operating in the radiation‐induced reaction, which has been found to be linearly dependent on dose rate and essentially independent of temperature. Assuming the thermal dehydrochlorination to proceed according to the same mechanism, its activation energy, lying within the range of values reported in the literature, represents the activation energy for the thermal process of radical formation by dissociation of normal and anomalous structures in PVC macromolecular chains. Since this value appears to be substantially constant in the temperature range from 90° to 240°C, it can be established whether the dissociation reactions of all the PVC structures are regulated by the same activation energy or, more simply, only one of these structures is concerned.
Thermal analysis of polyacrylonitrile. Part I. The melting of polyacrylonitrile
Authors: Dunn P. , Ennis B. C.
Published: April 2003

The melting point of polyacrylonitrile can be determined directly by differential thermal analysis, provided that a sufficiently fast heating rate is used. The experimental value of 326°C agrees well with predicted values of the melting point. The disparity between oxidative and thermal decomposition of the polymer is noted.
The stress cracking of polyamides by metal salts. Part IV. Metal nitrates
Authors: Dunn P. , Sansom G. F.
Published: April 2003

The stress cracking of polyamide (nylon 6) by a number of metal nitrates in aqueous and nonaqueous solution has been investigated. Copper and zinc nitrates were the most active. Stress cracking parameters were determined and the sorption of the nitrates into nylon 6 film was studied using infrared techniques. Evidence of coordination of some metal nitrates when sorbed into nylon 6 was obtained.
Studies on ion‐exchange membranes. XXXII. Heterogeneity in ion‐exchange membranes
Authors: Mizutani Yukio , Nishimura Masakatsu
Published: April 2003

Twelve kinds of cation‐exchange membranes were treated with hydrogen peroxide. Some of them (Selemion CMV, Nepton CR‐61, Scrion C‐100, SAM‐1) were completely destroyed. Heterogeneity is believed to be present in that part of their chemical structures that is decomposable by the treatment. The other membranes were converted into porous membranes by the decomposition of the resinous part. Water permeabilities and electric resistances of the porous membranes were examined to evaluate the pore radius. It was concluded that the “paste method” membranes have a heterogeneity or localized distribution of the resinous part under 50 mμ. The “paste method” membranes seemed to resemble the “graft method” membranes in chemical structure and to be much different from the mosaic‐type membranes such as Permaplex and MC‐3142. These results were also supported by extraction of the membranes with appropriate solvents and observation by electron microscopy.
Studies on dry spinning. II. Numerical solutions for some polymer–solvent systems based on the assumption that drying is controlled by boundary‐layer mass transfer
Authors: Ohzawa Yoshiyuki , Nagano Yutaka
Published: April 2003

Numerical solutions of the fundamental equations for dry spinning are obtained by assuming that the rate of the drying of solvent is controlled by the transfer of the solvent vapor at the boundary layer formed outside the filament surface. The polymer–solvent systems for the calculation cover acetate–acetone, poly(vinyl alcohol)–water, polyacrylonitrile–dimethylformamide, and polyurethane–dimethylformamide systems. Quantities necessary for the calculation are summarized. They are material properties (vapor pressures of the solvents, viscosities of the polymer and solvent systems, and so forth) and heat‐ and mass‐transfer coefficients. Mass‐transfer coefficients for acetone and dimethylformamide are evaluated by measuring the ratio of heat‐transfer coefficients to mass‐transfer coefficient based on the method of measuring wet‐ and dry‐bulb temperatures. The variation of the phenomenologic quantities such as solvent content, cross‐sectional area, and temperature of the filament along the spinning path is shown in Figure 4.
The diffusion of gases and water vapor through grafted polyoxymethylene
Authors: Williams J. L. , Stannett V.
Published: April 2003

Polyoxymethylene was successfully grafted with styrene, butadiene, and acrylonitrile by the mutual irradiation method in the monomer containing 18% of dimethyl formamide. The CO2 and water vapor permeabilities and diffusivities were determined in the case of the butadiene‐ and acrylonitrile‐grafted products. The former grafts had higher permeabilities than the ungrafted materials. However, the acrylonitrile grafts showed considerably reduced water vapor permeability and diffusivity compared to the ungrafted polyoxymethylene. Films made by grafting to polymer powder and compression molding showed lower permeabilities compared to those made by direct grafting to polyoxymethylene films.
The thermal degradation in vacuo of an amine‐cured epoxide resin
Authors: Leisegang E. C. , Stephen A. M. , Paterson‐Jones J. C.
Published: April 2003

The degradation in vacuo of the cured resin from stoichiometric amounts of the diglycidyl ether of bisphenol A and p,p′‐diaminodiphenylmethane was studied at temperatures of 303.7 and 304.0 ± 0.2°C. The condensible products of the degradation at these temperatures were collected and the major components were isolated as pure compounds. These were identified as water, bisphenol A, 2‐(benzofur‐5‐yl)‐2‐(p‐hydroxyphenyl)propane, N,N,N′,N′‐tetramethyl‐p,p′‐diaminodiphenylmethane, phenol, p‐isopropylphenol, p‐isopropenylphenol, N,N‐dimethylaniline, N‐methylaniline, N,N‐dimethyl‐p‐toluidine, benzofuran, and N‐methyl‐p‐toluidine. The presence of 2,2‐bis(benzofur‐5‐yl)propane was suspected. The gaseous degradation products were identified as acetaldehyde, chloromethane, carbon dioxide, carbon monoxide, methane, ethane, ethene, and nitrogen. Tentative reaction mechanisms are proposed to account for the formation of the products identified. The possible nature of some of the minor degradation products is discussed. The results are related to those of previous studies of the degradation of the same and similar resin–hardener systems.