bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of fluid motion on radiation‐induced polymerization of ethylene in a tubular reactor
Authors: Kawakami Waichiro , Wada Takeshi , Watanabe Terutaka , Machi Sueo , Kagiya Tsutomu
Published: April 2003

The influence of the turbulence of reactant on the radiation‐induced polymerization of ethylene in 40 mole‐% Freon‐114 (C2Cl2F4) was studied using a tubular reactor at 400 kg/cm2 and 25°C with a dose rate of 1.3 × 105 rad/hr. At constant linear velocity and tube diameter, the polymer concentration was shown to increase linearly with the reactor tube length. This indicates that the polymerization is in a stationary state. By changing the linear velocity from 3.5 to 42.7 cm/sec and the tube diameter from 5 to 14 mm, the space time yield and the molecular weight of polymer were found to vary between 0.21 and 0.46 mole ethylene/1.‐hr and from 5.0×103 to 10.5×103, respectively. The space time yield and molecular weight decreased sharply to about one half those in the static polymerization with increasing fluid turbulence and then slowly increased in the highly turbulent state. Similar effects were observed in a tank reactor when the stirring speed was changed.
Deuterium isotope effect on the refractive index of liquids and its application to permeation chromatography
Authors: Carignan Yvon P. , Turngren Edward V.
Published: April 2003

Differences in refractive index between deuterated and normal solvents have been determined using a conventional gel permeation chromatograph equipped with a differential refractometer detector. Three molecular systems have been studied, namely, water–deuterium oxide, acetone–acetone (d6), and tetrahydrofuran–tetrahydrofuran (d8). A plot of the signal intensity versus the concentration of the deuterated solvent in the normal solvent gave a linear relationship for all three systems studied. The effect of deuteration is found to result in a lowering of the refractive index which is at least three orders of magnitude larger than the sensitivity of the differential refractometer. Consequently, for permeation chromatographic studies, the addition of 1% or less of the deuterated solvent in the injection sample would be more than sufficient to produce a peak characteristic of the mobile phase.
Heat‐resistant polymers containing the low molecular weight closo‐carboranes. II. Thermal behavior of polycarboranesiloxane SiB‐1 elastomers from C2B5H7
Authors: Kesting R. E. , Jackson K. F. , Newman J. M.
Published: April 2003

Unmodified 5‐SiB‐1 polymers have been found to be virtually equivalent to their 10‐SiB‐1 counterparts with respect to thermal stability. The 5‐SiB‐1 polymers, however, are substantially more amenable to conversion into elastomers. The introduction of 15 to 20 mole‐% of m‐C2B10 into the 5‐SiB‐1 backbone results in elastomers whose thermal stability, although less than that of the parent homopolymer, is nevertheless substantially in excess of the published values for the higher SiB polymers. The crystallization of the 5‐SiB‐1 copolymer containing 15 mole‐% C2B10 was inhibited by irradiation with 50 megarads of 3 MeV betas. The 5‐SiB‐1 copolymer containing 20 mole‐% C2B10, on the other hand, remained a rubber at room temperature.
Diffusion in concentrated polystyrene solutions
Authors: Paul D. R. , Mavichak V. , Kemp D. R.
Published: April 2003

The wedge interferometer technique was used to measure the diffusion coefficients for concentrated solutions of polystyrene. A wide range of molecular weights, all monodisperse except for one, and 14 solvents were studied. Reproducibility of the data was demonstrated in the concentrated region, and good agreement with the sparse literature was observed. The experimental results are discussed and analyzed in terms of current knowledge and theories. In the concentrated region, the solvent type plays a significant role in determining the diffusion coefficient. Its effect cannot be explained simply in terms of hydrodynamics nor the molecular structure of the solvent. In cyclohexanone the diffusion coefficient was found to increase with polymer molecular weight up to 100,000 and to become independent thereafter.
The size analysis of polymer latices by electron microscopy using freeze‐etched preparations
Authors: Reed R. , Barlow J. R.
Published: April 2003

A range of styrene–butyl acrylate copolymer latices has been studied in the electron microscope, using the freeze‐etching method of specimen preparation. This involves the rapid freezing of a small specimen, fracture of the frozen block, followed by replication of the fracture surface. The process of freezing rapidly to liquid air temperatures minimizes deformation of “soft” latex particles and allows their size to be determined. Certain latices were also investigated using a conventional method of specimen preparation, involving size measurements on dried, deformed particles. The particles observed in freeze‐etched preparations appeared to have slightly smaller diameters.
Poly(ethylene sulfide). IV. A rheological method for determination of “apparent molecular weight”
Authors: Catsiff E. H.
Published: April 2003

By combining a number of theoretical relationships concerning the effect of molecular weight on melt rheology, an equation may be derived for conversion of melt indexer flow rate to “apparent molecular weight.” In spite of certain evident theoretical shortcomings of this derivation, the method was applied to the determination of the molecular weight of highly crystalline insoluble poly(ethylene sulfide), for which no other method appeared to be satisfactory. When applied to polymer specimens of presumably known molecular weight (e.g., certain ionically initiated specimens), reasonable agreement was found.
The production of rubber‐modified polystyrene. I. Rheological behavior of the polymerizing system
Authors: Freeguard G. F. , Karmarkar M.
Published: April 2003

The rheological behavior of the two‐phase systems consisting of a polystyrene‐in‐styrene phase distributed in a rubber‐in‐styrene phase is shown to exhibit increasing non‐Newtonian behavior up to the phase inversion point, as a consequence of its two phase nature. The equation

is recommended for the prediction of the viscosity of the polymerizing mass up to phase inversion during the production of HIPS by the in situ bulk polymerization of styrene in the presence of dissolved rubber.
The production of rubber‐modified polystyrene. II. The significance of shear in the phase inversion
Authors: Freeguard G. F. , Karmarkar M.
Published: April 2003

Phase inversion of the two‐phase system consisting of a polystyrene‐in‐styrene phase distributed in a rubber‐in‐styrene phase is shown only to occur above a minimum shear rate, which is experimentally determined for a range of rubber concentrations. The conditions for agitation of the system to give a smooth and nondelayed inversion point are separated into meeting two requirements, one of which is related to mass transfer to the discontinuous phase and the other, to meeting the shear requirement; these are discussed in terms of the known rheological behavior of the system.
Ionic reverse osmosis membranes of grafted polyethylene
Authors: Lamaze C. E. , Yasuda H.
Published: April 2003

Membranes of graft copolymers of polyethylene with poly(sodium styrene sulfonate), poly(4‐vinylpyridinium methyl bromide), and poly(sodium acrylate) were prepared by using the technique of peroxide grafting. The reverse osmosis characteristics of the membranes were examined as a function of grafting yield. In these membranes, the grafting can be considered as a process of introducing ionic sites, and it depends on the conditions of the grafting reaction, such as monomer concentration and temperature. However, the overall reverse osmosis characteristic is not only dependent on the number of ionic sites introduced but also on the swelling capability of the membrane. Consequently, the salt rejection of grafted membrane of a fixed graft yield depends on the conditions of the grafting reaction. All grafted membranes which have grafting yields above a certain value behave as normal ionic polymer membranes, and their interrelationship of salt rejection and water permeability follow the general dependence found for ionic polymer membranes.
Structure–concentration equivalence in carbon black reinforcement of elastomers. III. Application to tensile strength
Authors: Kraus Gerard
Published: April 2003

Using carbon blacks of constant specific surface area and surface chemical characteristics, but differing in degree of structure, it is shown that tensile strength, elongation at break and rupture energy are functions of the product av2, where v2 is the volume concentration of carbon black and a is a structure dependent factor. Moreover, reductions of failure data to a common effective filler concentration are accomplished with the identical structure factors used earlier in modulus reductions. The values of the structure factors are linearly related to the dibutyl phthalate (DBP) absorption of carbon black, when care is taken to equalize the packing density prior to conducting the DBP test.
Relative thermophysical properties of some polyimides
Authors: Jewell Robert A.
Published: April 2003

A comparative thermogravimetric study of ten polyimide films of varying composition revealed that thermal and thermo‐oxidative stability of the polymers increases directly with increasing imide content. Films degraded more rapidly in air than in vacuo; the insertion of connecting groups within the polymer repeat unit decreased stability in both environments. The effect of inserting “ladder‐like” segments in the polymer structure did not enhance resistance to oxidation; but under vacuum, those segments probably operated beneficially in promoting the retention of the carbon‐like residue. Infrared spectral measurements showed little loss of imide bands with progressive weight loss in air, indicating unit‐by‐unit degradation. Conversely, infrared spectra of films heated under vacuum conditions showed that progressive loss of imide bands occurred simultaneously with an increasing development of bands related to carbon–nitrogen double bonds. Dynamic heating under vacuum developed singularly uniform weight loss curves; however, concurrent mass‐spectrographic analyses indicated two distinct reactions. Gaseous carbon monoxide and carbon dioxide species accounted for the major weight change, and their periods of maximum evolution occurred at different temperatures for each film. A subsequent minor weight loss period was associated with the liberation of hydrogen cyanide which maximized at the same temperature for all ten films.
Thermal conductivity of polymer melts
Authors: Fuller T. R. , Fricke A. L.
Published: April 2003

A concentric cylinder conductivity cell with guard heaters was constructed and used to determine the thermal conductivity of polymer melts. Thermal conductivity was found to be a linear function of temperature for the melts studied, and the thermal conductivity decreased as the complexity of the polymer chain increased. The polymers studied were a linear polyethylene, branched polyethylene, polypropylene, polystyrene, nylon 6, and nylon 6,10. The measurements are precise to within ±6%.
Photochemical reactions of the substituent groups of cotton cinnamate fabric
Authors: Bertoniere Noelie R. , Franklin William E. , Rowland Stanley P.
Published: April 2003

The extents to which the substituents of cotton cinnamate fabrics dimerize and undergo cis–trans isomerization upon irradiation with 2537 Å light were determined. It was shown that these photochemical reactions occur primarily on the surface of the fabric. Simple crosslinking via the truxillic and/or truxinic acid residues, although directly related to the increases in conditioned wrinkle recovery angles, was sufficient to produce fabrics with only moderate levels of wrinkle recovery properties.
Modification of emulsion polymerization by multiple addition of modifier
Authors: Uraneck C. A. , Burleigh J. E.
Published: April 2003

Model equations were used to determine approximately the optimum conditionneeded to obtain the lowest molecular weight, P̄v, with a fixed molar amount of modifier by the addition in three portions of modifiers with different regulating indexes. Simulated calculations were also conducted to determine the effect two‐ and three‐portion additions of a modifier had on the P̄v/P̄n ratio. The simulated calculations served as guides for two‐, three‐, and manyfold incremental modifier addition experiments. The calculations and experiments establish the need for matching the portioning of the modifier to the regulating index in order to obtain efficient use of the modifier.
Graft polymerization of some vinyl monomers onto acrylic rubber. II. Mechanical properties of graft polymers
Authors: Ide Fumio , Sasaki Isao , Deguchi Seiji
Published: April 2003

Some mechanical properties of styrene and acrylonitrile copolymers grafted onto acrylic rubber are investigated. The impact strength of graft polymers depended upon the nature and the concentration of the catalyst, the composition and the intrinsic viscosity of the rubber, and the acrylonitrile content in the rigid matrix. The most desirable result was obtained when benzoyl peroxide as the catalyst, n‐butyl acrylate–acrylonitrile copolymer of 7–10% acrylonitrile content, and about 0–5% acrylonitrile in the rigid matrix were used. Dynamic mechanical tests show the increase in efficiency of rubber modification by the grafted chains. The better weathering resistance of these graft polymers, as compared with commercial ABS plastics, was confirmed.
Change of mixing state of polybutadiene rubber–polyolefin resin blend by remilling and heat treatment
Authors: Satake Kunio
Published: April 2003

The change of the mixing state of polybutadiene rubber–polyolefin resin blend resulting from remilling and heat treatment was studied. Polyolfin resins studied here were high‐pressure polyethylene, low‐pressure polyethylene, and polypropylene. As in case of polybutadiene rubber–general purpose polystyrene resin blend, we made use of the results obtained through hardness and compression modulus measurement and microscopic observation. Even in case of polybutadiene rubber–polyolefin resin blend, the change of mixing state and the softening phenomenon by remilling were observed. The hardening phenomenon by heat treatment of the sample softened by remilling was also observed at high polyolefin resin content. But at low polyolefin resin content, the hardness which had increased once often decreased as the heat treating time increased, and in some cases the nonremilled sample was observed to soften with heat treatment. These phenomena attendant on heat treatment show that the intrinsic nature of a heterogeneous blend system also appears in a microheterogeneous polymer blend system.
The influence of chemical structure on the dynamic properties of sulfur‐vulcanized, carbon black‐reinforced natural rubber
Authors: Doyle G. M. , Humphreys R. E. , Russell R. M.
Published: April 2003

A comparison is made of the composition and properties of the different rubber vulcanizate networks obtained by varying the ratio of sulfur to sulfenamide accelerator and by the thermal aging of vulcanizates containing predominantly polysulfide crosslinks. It is concluded that the changes in network structure which can take place, for example, during the service life of natural rubber tires are not the direct cause of failures of the type associated with rubber fatigue at high temperatures. However, a reduction in the total number of crosslinks can accelerate failure by increasing the amount of heat generated during flexing. More stable networks giving improved resistance to fatigue at high operating temperatures are obtained by the use of higher ratios of accelerator to sulfur than are conventionally employed.
Bead‐spring model of dilute polymer solutions: Continuum modifications and an explicit constitutive equation
Authors: Gordon R. J. , Everage A. E.
Published: April 2003

A continuum modification of the bead‐spring (elastic dumbbell) theory of dilute solutions of linear macromolecules, recently introduced by Gordon and Schowalter, is used to obtain explicit constitutive equations for the stress and polarizability tensors. The stress constitutive equation, closely related to a semiempirical result obtained earlier by Spriggs, is superior in predictive capability to the constitutive equation obtained from the elastic dumbbell theory. Results are presented for steady shearing flow, large‐amplitude oscillatory shearing, and stress relaxation following cessation of steady shearing and are compared with the results of the elastic and rigid dumbbell theories. In general, predictions are similar to those of the rigid dumbbell and thus are in qualitative agreement with experiment.
Graft copolymerization of vinyl monomers on modified cotton. IV. Ceric‐induced grafting on vinyl monomers on cellulose bearing different substituents
Authors: Hebeish A. , Kantouch A. , El‐Rafie M. H.
Published: April 2003

The influence of introducing various functional groups into the cellulose molecule on its susceptibility toward grafting with vinyl monomers such as acrylonitrile and methyl methacrylate using the Ce(IV)–cellulose redox system was studied. While cellulose bearing either cyanoethyl or carboxymethyl groups showed higher graft yields, cellulose bearing both groups showed lower yields. Presence of acrylamidomethyl groups in the cellulose molecule reduced its reactivity to grafting. The same holds true for cellulose bearing acrylamidomethyl groups along with carboxymethyl groups. On the other hand, introducing carbamoylethyl groups in the cellulose molecule enhances significantly the susceptibility of cellulose toward grafting. This is also observed with cellulose bearing cyanoethyl and carboxyethyl groups. Treating cellulose with N‐methylolacrylamide in alkaline medium seems to produce a crosslinked cellulose with lower reactivity to grafting. The results obtained with the different substrates were discussed on the basis of the change in the physical and/or chemical structure of cellulose brought about during its modification as well as on the nature of the substituent groups introduced. The mode of Ce(IV) attack on cellulose was also clarified.
The development of the velocity field in polymer melts in a reservoir approaching a capillary die
Authors: Ballenger Timothy F. , White James L.
Published: April 2003

Color motion pictures have been made of the flow of low‐density polyethylene, polystyrene, and isotactic polypropylene at 180°C in the reservoir approach to a capillary extrusion rheometer. Detailed observations of the variation of flow patterns with extrusion rate were made. At low flow rates, essentially radial flow into the capillary entrance was observed in all polymers. With increasing flow rate, the included entrance angle α for the polyethylene and polystyrene decreased from 180°C and a “wine glass” structured velocity field was observed with stagnant circulating regions in the corners and the melt channeling in through the wine glass to the capillary entrance. The angle α was related to entrance pressure drop Δpe and capillary wall shear stress σw data through the semilogarithmic equation

where α is in degrees; Δpe/σw is interpreted as a Weissenberg number. The breakdown of stable laminar flow of the melts in the reservoir and the distortion of extrudates was observed. These phenomena seemed to be initiated by the formation of a spiralling motion in the reservoir.
Viscous behavior of some liquid rubber resins
Authors: Peyser Y. , Dealy J. M. , Kamal M. R.
Published: April 2003

The flow behavior of several low molecular weight polymers has been studied as a function of shear rate and temperature. These polymers, which had terminating hydroxyl or bromine groups, included homopolymers of polybutadiene and acrylonitrile–butadiene and styrene–butadiene copolymers. Viscosity was measured as a function of shear rate for the temperature range 25°–35°C, and the limiting zero shear viscosities were obtained for the range 25°–60°C. A cone plate viscometer was employed to measure the effect of shear rate on viscosity, and a Brookfield viscometer was used to verify the zero‐shear rate values. A tendency of the fluid to flow out of the cone‐plate gap was observed for some of the materials studied. From the viscosity data, characteristic times were estimated, and the data were compared with two constitutive equations. A modified Arrhenius equation was fitted to the zero‐shear viscosity data. In the case of one material, it was possible to test the Nakajima relationship between viscosity and molecular weight distribution. The dependence of material parameters on temperature is discussed in detail.
An automatic dilatometer for radiation polymerizations
Authors: Niezette J. , Desreux V.
Published: April 2003

An automatic dilatometer particularly suitable for radiation polymerizations is described. The volume contraction may be followed outside the irradiation room by two methods with great accuracy.
Microelectrophoresis and electron‐microscope studies with polymeric flocculants
Authors: Ries Herman E. , Meyers Bernard L.
Published: April 2003

Mechanisms for the stabilization and flocculation of colloids have been indicated by microelectrophoresis measurements and electron‐microscope observations with model colloids and polymeric flocculants. Zeta‐potential (ζ) changes and details of floc structure were observed with silica and polystyrene latex colloids. Bridging fibers of polyamine‐type flocculants appear to extend radially from the colloidal particles and vary in thickness from 20 to 300 Å. Charge neutralization and bridging may function simultaneously. Incremental additions of cationic flocculants produce gradual reduction in the negative ζ, and maximum flocculation is observed near zero ζ. Subsequent addition of flocculant reverses the potential and finally effects redispersion of the colloid. If incipient charge reversal is produced with a relatively low molecular weight cationic polymer, large flocs may then be formed on the addition of a high molecular weight anionic flocculant. Direct addition of an anionic polymeric flocculant to a negatively charged colloid may raise the negative ζ to a surprisingly high value and may thus effect stabilization instead of flocculation of the colloid.
Formation of 2,4‐dinitrophenylhydrazone on surface zone of polystyrene film irradiated by ultraviolet light. I. Effects on formation of 2,4‐dinitrophenylhydrazone
Authors: Kato Koichiro
Published: April 2003

The hydrazones of the acetophenone‐type 2,4‐dinitrophenyihydrazone, formed by the reaction between 2,4‐dinitrophenylhydrazine and carbonyl groups, was formed on the surface zone of irradiated polystyrene film. The changes in the amount of hydrazones formed on the films were inferred by comparing the absorptions in the ultraviolet and infrared spectra. The amounts of hydrazones formed increased with increase in irradiation time within about 3 hr and approached an asymptote with increase in irradiation time upward of about 4 hr. For the samples irradiated for 6 1/2 hr, the changes in the absorptions of the hydrazones stopped in about 3 min after the films were immersed in the 2,4‐dinitrophenylhydrazine solution, the amounts of hydrazones formed increased with increase in the amount of benzene in the 2,4‐dinitrophenylhydrazine solutions, the amounts of hydrazones formed slightly increased with rising temperature below 60°C in the solutions, and the rate of increase slightly increased with rise in temperature above 60°C in the solutions.
Melting of drawn polyethylene films
Authors: Clough S. B.
Published: April 2003

If drawn, crosslinked, high molecular weight polyethylene films are restrained during melting, two endothermic peaks may be noted on a scanning calorimeter. In x‐ray diffraction experiments, the appearance of a single new peak accompanies the disappearance of the orthorhombic pattern. The new peak is thought to be due to hexagonal chain packing above the melting temperature. The results are interpreted in terms of a small amount of fibrillar crystals in the drawn films.
Flammability characteristics of cotton and polyester fibers
Authors: Stepniczka H. , Dipietro J.
Published: April 2003

This study was undertaken to measure quantitatively the flammability characteristics of cotton and polyester fibers. The smoke density generated during the burning of these fabrics was also studied at various temperature conditions. A mathematical relationship was established between the results obtained in an oxygen‐depleted atmosphere chamber and those obtained in a chamber in which there was constant replenishing of an oxygen and nitrogen atmosphere. Three commercially available flame‐retardant treatments were utilized in this study. The effect of temperature as well as the influence of fabric weight on the flammability behavior and the smoke density of these fabrics were investigated. A novel instrument built according to ASTM standards was employed throughout this study; it was found to be versatile, convenient, and highly reproducible in the generation of the data. It was found that polyester fabrics generate far more smoke than cotton fabrics without the phenomenon of afterglow. It was found also that as the temperature increases, the smoke density of cotton fabrics increases as well, but in the case of polyester fabrics the opposite relationship was obtained.
The iron salt‐catalyzed autoxidation of atactic polypropylene
Authors: Stivala S. S. , Jadrnicek B. R. , Reich L.
Published: April 2003

The iron‐catalyzed autoxidation of atactic polypropylene has been studied in the solid phase using infrared spectroscopy. The reaction temperature ranged from 110° to 130°C, the ferric acetylacetonate concentration varied from 0.3 × 10−7 to 90.0 × 10−7 mole per 7.5 mg atactic polypropylene, and the oxygen concentration varied from 5 to 100 vol‐%. In the region of relatively low catalyst concentrations, the maximum steady rate varied approximately first order in respect to the catalyst concentration and about zero order at relatively high values of the catalyst concentration. Linear relationships between the maximum steady rate and the oxygen concentration, for both low and high concentrations, were obtained. A general scheme and kinetic expressions derived there‐from previously reported for the uncatalyzed autoxidation of polyolefins and recently modified to account for cobalt‐catalyzed autoxidation of actactic polypropylene has been successfully applied to the experimental results.
Bisacid A2 (2,2‐diphenylolpropane dioxyacetic acid) as a constituent of crosslinked polyesters
Authors: Lenk R. S.
Published: April 2003

The preparation of polyester resins using Bisacid A2 as the modifying acid in systems containing maleic unsaturation is briefly described. The detailed compositions of the various resins, the yields, final acid values, and capillary melting ranges are tabulated. The preparation of resin solutions in reactive monomers (principally styrene) and the viscosities of the resulting liquid resins at various monomer contents are given. The casting of unfilled standard sheet for subsequent testing is described. The range of Barcol hardnesses of the cast cured sheets is reported.
Preparation and characterization of phosphorus‐nitrogen polymers for flameproofing cellulose. I. Polymers of THPC and amines
Authors: Kasem M. A. , Richards H. R. , Walker C. C.
Published: April 2003

Polymers from tetrakis(hydroxymethyl)phosphonium chloride (THPC) or tris(hydroxymethyl)phosphine (THP) with ammonia show similar thermal degradation, but appear to be of different chemical structure. Solution reaction of THPC with urea or melamine or by solid‐phase reaction with urea gives products ranging from water‐soluble liquids to hard, brittle, insoluble polymers. Reaction of THPC with piperazine yields products of low thermal stability.
Crystalline character of native and chemically treated Egyptian cottons. I. Computation of crystallinity, disorder parameter, orientation factor, and spiral angle
Authors: Shenouda S. G. , Viswanathan A.
Published: April 2003

Computer data processing and electronic monochromatization of x‐rays were employed for determining crystallinity, disorder parameter, Hermans' orientation factor, as well as DeLuca and Orr spiral angle of native, mercerized and urea‐treated cottons. The results indicate the values for the degree of crystallinity to vary significantly between ecttons. Increase in disorder on mercerization is confirmed. The effect of urea treatment is not so well defined. The differences in Hermans' x‐ray orientation factor are significant at the 1% level between cottons and at the 10% level between treatments. Besides, from a critical analysis of the values obtained, it is shown that the spiral angle φt in the method of DeLuca and Orr is probably a direct estimate of the mean inclination of the crystallites to the fiber axis, while Hermans' orientation angle β is a complex function of other parameters as well. The computer programs which could be applied to other polymers are included.
Polymerization of styrene in an electrodeless glow discharge
Authors: Yasuda H. , Lamaze C. E.
Published: April 2003

The polymerization (polymer deposition) rate of styrene in an electrodeless glow discharge from styrene vapor and a mixture of styrene vapor and gas (H2, He, A, and N2) was investigated. The rate of polymerization, R, was found to be independent of the discharge power. The rate of polymerization of the pure monomer was found to be proportional to the square of monomer pressure pM. The addition of gas increased the rate of polymerization depending upon the partial pressure of the gas, px, and R can be generally expressed by R = a[pM]2{1 + b[px]}. The value of b is dependent of the type of gas and follows the order of N2, > A > He > H2. The distribution of polymer deposition was found to be nearly independent of the partial pressure of the gas and of the discharge power with N2 and H2 as plasma gas; however, with He and A, the distribution is highly dependent on the partial pressure of the gas and on the discharge power. The study strongly suggests that polymerization occurs in the vapor phase and that the growing polymer radicals deposit on the surface of the discharge vessel, yielding highly crosslinked polymer deposition.
Shock pulse mitigation in various organic foams
Authors: Wasley Richard J. , Nidick Ernest J. , Valentine Robert H. , Hoge Kenneth G.
Published: April 2003

The mechanical behavior of three kinds of organic foams, each at two different densities, was experimentally investigated under conditions of pulsed one‐dimensional strain shock loading. The input pulse width in each experiment was nominally 0.1 μsec, and the input stress level (as referenced to quartz) was varied between 10 and 23 kbar. The materials studied were polyurethane foam at bulk densities of 0.33 and 0.21 g/cc, syntactic foam (phenolic microballoons dispersed in a resin binder) at 0.66 and 0.23 g/cc, and polystyrene bead foam at 0.091 and 0.049 g/cc. Specimen thicknesses varied between 1.0 and 6.5 mm. It was found that the pulse duration was greatly lengthened and that the peak stress was decreased (accounting for both impedance mismatch and attenuation effects) by factors of between about 8 and 500, depending upon the type of foam, its thickness, and its density.
GPC calibration for polymers of unknown composition and structure using a real‐time computer
Authors: Braun Gérard
Published: April 2003

A computer technique ultimately yielding, from GPC data, both differential and integral molecular weight distributions of macromolecular products with unknown composition and structure has been worked out, based on a “universal” calibration method previously proposed by other authors to calculate average molecular weights. The technique involves as sole assumption the validity of the “universal” calibration for the kind of sample under investigation. The GPC output data are handled through a realtime computer program and punched on paper tape. Together with two experimental parameters of the polymer (average molecular weights, limiting flow number) and the “universal” calibration of the columns set, the tape is used as input for the off‐line programming. Examples are presented, showing the accuracy which can be expected.
Thermal analyses of polymers. VII. Calorimetric and dilatometric aspects of the glass transition
Authors: Miller Gerald W.
Published: April 2003

For the determination of Tg by DTA with the use of small samples, slow heating rates, and extrasensitive amplification, it can be shown that the previously reported basel ne changes for polystyrene, polychloroprene, poly(methyl methacrylate), and polycarbonate can be resolved as endotherms. Measurements with small samples more accurately determine the calorimetric changes than with large samples, even at slow heating rates. The use of large samples for DSC or DTA measurements may be the reason for apparent heating rate dependence. The measurements of this study indicate little heating rate dependence if very small samples are used. Moreover, the slower the cooling from the melt, the sharper the endotherms, indicating the importance of thermal history. The data raise the question about the validity of assuming that a baseline or abrupt change in Cp via a DTA measurement is necessarily that of a real second‐order change or Tg. Preliminary dilatometric results tend to show that the changes for polystyrene, polychloroprene, poly(methyl methacrylate), and polycarbonate may be first order at 94°C, 32°, 114°, and 156°C, respectively. Only the change at 75°C for polystyrene appears second order by volume—temperature data.
Some aspects of PVC paste rheology
Authors: Butters G. , Roberts Gillian
Published: April 2003

Using the Weissenberg rheogoniometer, a technique has been developed which facilitates the measurement of shear stress data and which substantially overcomes the problem of sample loss that normally occurs at high shear rates. Using this technique, the apparent viscosities of PVC pastes based upon four different PVC paste polymers plasticized with dialphyl phthalate have been determined at a number of shear rates up to 9000 sec−1 and the viscosity aging characteristics of these paste polymers have been compared. The effect of several common plasticizers upon PVC paste viscosity and viscosity aging have been studied at shear rates of the order of 10 sec−1 and 1000 sec−1.
Rheological and heat transfer aspects of the melt spinning of monofilament fibers of polyethylene and polystyrene
Authors: Acierno Domenico , Dalton J. Nelson , Rodriguez Jorge M. , White James L.
Published: April 2003

Two experimental studies of the melt spinning of fibers have been carried out using low‐density polyethylene and polystyrene. First, isothermal spinning experiments were carried out and the relationship between the fiber kinematics and drawdown force was studied. The data were correlated by using the following two methods: (1) the concept of a non‐Newtonian elongational viscosity and (2) a nonlinear integral theory of viscoelastic fluids. In the second experiment, the spinline temperature profile of a monofilament fiber being pulled down from a spinneret through stagnant air was measured and the heat transfer coefficient computed. A correlation between the local Nusselt number and a fiber Reynolds number was obtained. An integral boundary layer analysis of forced convection heat transfer from a descending fiber was carried out.
Properties of poly(alkylene oxide) elastomers
Authors: Hsieh H. L. , Wright R. F.
Published: April 2003

The catalyst comprised of triisobutylaluminum, zinc acetylacetonate, and water was used to prepare homopolymer of epichlorohydrin; copolymers of epichlorohydrin with propylene oxide, ethylene oxide, and allyl glycidyl ether; and terpolymers of epichlorohydrin, propylene oxide, and allyl glycidyl ether and of epichlorohydrin, ethylene oxide, and allyl glycidyl ether. The vulcanizates of these rubbers provide variations of stressstrain and dynamic properties, freeze point, hardness, and solvent resistance depending on the type and amount of comonomer. In general, these rubbers have excellent heat, ozone, and oxidation resistance as well as oil and solvent resistance.
Polymerization of alkylene oxides with trialkylaluminum, metal acetylacetonates, and water
Authors: Hsieh H. L.
Published: April 2003

Trialkylaluminum and acetylacetonates of Groups II and III metals are very effective polymerization catalysts for alkylene oxides. Addition of water increased both polymerization rate and yield. Among many combinations examined, a combination of triisobutylaluminum, zinc acetylacetonate, and water is outstanding. It gives high rate, high yield, and high degree of polymerization. The mole ratio of these three components was extensively studied and shown to be less critical than for other systems. Order of addition was not important. Elastomeric products based on propylene oxide, ethylene oxide, epichlorohydrin, and allyl glycidyl ether were prepared in high yield in relatively short reaction times. Copolymerization rates for epichlorohydrin–ethylene oxide and epichlorohydrin–propylene oxide were determined and indicated that this catalyst is anionic in character. It is concluded that the bimetallic nature of this catalyst is responsible for its high reactivity, versatility and stereochemistry.
An approach to a simplified universal calibration for gel permeation chromatography
Authors: Funt B. L. , Hornof V.
Published: April 2003

Criteria for establishing a universal GPC calibration for poly‐1,2‐butadiene on the basis of polystyrene standards are considered. The number‐average molecular weights of the two polymers are related by a linear expression on the assumption that their respective Mark‐Houwink exponents are equal. The coefficient Cn of this expression, determined from GPC and viscosity measurements, remained constant for a considerable range of molecular weights and polydispersities. The applicability of Cn beyond the interval of present measurements is considered on the basis of results in the literature. The results are comparable to those obtained from a universal calibration based on the unperturbed dimension of polymer chains, but do not agree with those obtained from a model based on extended length.
The secondary relaxation process of poly(vinyl chloride) and its derivatives
Authors: Heidingsfeld Vikter , Zelinger Jiří , Kuška Vladimír
Published: April 2003

The temperature dependence of the shear modulus G′ and of the damping tan δ of poly‐(vinyl chloride), poly(vinylidene chloride), copolymers of vinyl chloride–vinylidene chloride, PVC chlorinated in solution and suspension, and chlorinated polyethylene was measured. Secondary relaxation process of PVC and its derivatives are being explained as vibration of methylene groups polarized by neighboring CCl dipoles. This process, being suppressed by lowering the concentration of the methylene groups in the PVC chain (e.g., by chlorination), remains, however, unaffected by the growth of crystalline content. The achieved results show that in the α‐transition region there occurs, in accordance with Andrews' theory, a loosening of the bonds between the CCl dipoles, whereas in the β‐transition region a loosening of the weaker bonds among the dipoles of the polarized methylene.
Chemorheological study of vulcanized rubbers under mechanical stress
Authors: Kusano Takae , Suzuki Yukizi , Murakami Kenkichi
Published: April 2003

At lower than the glass transition temperature, the cleavage of the molecular chains of extended vulcanized rubbers will occur. The crosslinking density of vulcanized rubbers, which were placed at room temperature for about 4 hr in nitrogen atmosphere, increased about 17% after extension of 200% at −76°C. This may be due to the recombination of cleft chains, and this can be shown by the Maxwellian type of curves between crosslinking density and forced strain. Considering the decreasing proportion of crosslinking density by the radical acceptors included in the rubbers and the fact that crosslinking density increases because of recombination of cleft chains, this was attributed to the recombination of unstable chains produced by the added mechanical stimulus.
Unidirectional fiber–polymer composites: Swelling and modulus anisotropy
Authors: Coran A. Y. , Boustany K. , Hamed P.
Published: April 2003

The solvent swelling of unidirectional rubber–fiber composites was studied. The amount of matrix swelling was constrained to the extent that would be predicted from the thermodynamic theories of elasticity and polymer–solvent interaction. The geometry of swelling was found to be orthotropic in nature. A simple trigonometric function was derived to relate linear deformation due to swelling to the angle which the direction of its measurement makes with the fiber direction. The validity of the derivation was demonstrated experimentally. Considering swelling to be the imposition of tensile forces of equal magnitude in all directions, and considering a swelling‐induced linear deformation to be analogous to a tensile compliance, a simple set of relationships between elastic parameters and their direction of measurement was derived:

where Eθ, Gθ, vθ, and ηθ are Young's modulus, shear modulus, Poisson's ratio, and the shear coupling ratio measured in a longitudinal transverse plane at an angle with the fiber direction, respectively, and EL, GLT, and θLT are the longitudinal Young's modulus, the longitudinal transverse shear modulus, and the longitudinal transverse Poisson ratio, respectively. Further simplifying the case of combined transverse isotropy and special orthotropy was the conclusion that 1/GLT = 1/ET + (1 + 2vLT)/EL. The relationships for G and E were experimentally demonstrated.
Relationships between mechanical properties and relaxation processes in polymers. Nylon 6
Authors: Garbuglio C. , Ajroldi G. , Casiraghi T. , Vittadini G.
Published: April 2003

The dynamic‐mechanical properties as a function of temperature and frequency were measured for five samples of polycaprolactam (nylon 6) containing different amounts of hydrosoluble products. Low‐ and high‐speed tensile properties and Izod impact strength were determined between −190° and 100°C for the same samples by using autographic methods. The influence of the mechanical relaxation processes on moduli, yield strength σy, yield strain εy, tough‐brittle transition temperature, elongation at break εR, and tensile and Izod fracture energies was investigated. It has been found that some mechanical properties, such as modulus and yield properties, can be directly related to specific relaxation phenomena, whereas as far as other properties, such as the ultimate properties, are concerned, the existing correlation can be concealed by the interference of purely mechanical phenomena which depend on the testing technique used, the testing conditions, and the previous history of the material.
Aging behavior of polyarylsulfone films
Authors: Alvino William M.
Published: April 2003

The aging behavior of two experimental polyarylsulfone films is discussed. The mechanical and electrical properties of the films were measured as a function of time at temperatures of 300°, 275°, and 250°C. The effect of “reprocessing” the material is also reported. DTA and TGA analysis, coupled with other aging test results, point out the excellent thermal stability of the polyarylsulfones. However, some peculiar behavior is exhibited by the unrefined polymer. Free film aging of this material showed no signs of discoloration or deterioration in properties after 1000 hr at 300°C. Film aged wrapped on metal and glass rods discolors badly, is subject to stress cracking, and embrittles. The reprocessed'' film is superior to its predecessor and exhibits none of the disadvantages that characterize the unrefined polymer. Solubility studies, coupled with the other aging tests, provided some insight into the degradation phenomenon of this polymer. Resistance to ultraviolet light is extremely poor. Reprocessing of the material provided for a much superior film material with a higher level of mechanical, electrical, optical, and thermal properties.
Effects of monomer impurities on the emulsion polymerization of chloroprene and properties of polychloroprene. III. Effect of divinylacetylene
Authors: Sufčák Miloslav
Published: April 2003

The presence of small amounts of divinylacetylene in the monomer during the emulsion polymerization of chloroprene results in substantial increase of the molecular weight, gel formation, and in corresponding changes of physical and mechanical properties of vulcanizates. These changes appear at concentrations of divinylacetylene as low as 0.05% in chloroprene. The polymerization kinetics of chloroprene are influenced to a relatively small extent.
Measurement of the rheological properties of polymer melts with slit rheometer. I. Homopolymer systems
Authors: Han Chang Dae
Published: April 2003

Two slit dies have been designed, having aspect ratios of 10 and 20. Three melt pressure transducers were flush‐mounted on the long side of the rectangular slot, along the longitudinal centerline of each die. The dies were then used to measure wall normal stresses along the longitudinal direction of polymer melts flowing through the thin slit. The polymeric materials investigated were high‐density polyethylene, low‐density polyethylene, polypropylene, and polystyrene. The measurement of wall normal stresses were used to determine the rheological properties of melts, namely, the melt viscosity from the slope of axial pressure profiles and the melt elasticity from exit pressures. The present study shows that the rheological properties determined from the slit rheometer are in good agreement with those from the capillary rheometer reported in the author's earlier papers. Therefore it may be concluded that a slit die also may be used as a means of characterizing polymeric materials by their viscous and elastic properties in the molten state.
Aminimides. XI. Modified polystyrenes containing pendent aminimide or isocyanate residues
Authors: Culbertson B. M. , Randen N. A.
Published: April 2003

The hydrochloride salt of 1,1‐dimethyl‐1‐(2‐hydroxypropyl)amine methacrylimide (DHA) was synthesized and shown to readily homo‐ and copolymerize with styrene to produce soluble polymers containing pendent quaternary ammonium groups. These polymers may be treated with base to provide modified polystyrenes containing pendent aminimide residues. The latter polymers may be thermolyzed in solution or in the solid phase to produce modified polystyrenes containing pendent isocyanate groups. If the thermolysis is carried out in the presence of “isocyanate reactive” moieties, high molecular weight, crosslinked polymers may be synthesized. The reactivity ratios of DHA · HCl with styrene were determined: r1 = 0.33 and r2 = 0.35. The Alfrey‐Price Q and e values were also calculated: Q = 0.88 and e = 0.67.