bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydraulic permeation of liquids through swollen polymeric networks. II. Liquid mixtures
Authors: Paul D. R. , Paciotti J. D. , Ebra‐Lima O. M.
Published: April 2003

The hydraulic permeation of toluene–cyclohexanone and isooctane–CCl4 mixtures through a membrane, a rubber network, was studied. No separation of components occurred in this mode. The mixture flux data were successfully analyzed using a solution–diffusion theory by treating the mixture as if it were a single component with properties of the mixture. Diffusion coefficients determined in this way appear to be governed by frictional forces having a hydrodynamic origin. Slight separation of the components did occur when the pervaporation mode of operation was used. The significance of this is discussed.
Photophysical processes in poly(hexamethylene adipamide)–acid dye complexes: Energetics of nylon 66 phototendering
Authors: Koenig H. Steve , Roberts Carleton W.
Published: April 2003

The mechanism of dye‐sensitized photo‐oxidative degradation of nylon 66 was investigated. A known phototendering dye, C.I. Acid Blue 40 (1‐amino‐4‐(p‐aminoacetanilide)‐2‐anthraquinone sodium sulfonate), was used for this study. Excitation and emission spectra of the dyed and undyed nylons indicated that a ground‐state complex between the dye and the polyamide was formed upon dyeing. The energy level of the complex's electronic states favor triplet–triplet energy transfer from the nylon to the complex. Quenching studies show that the energy transfer occurs efficiently with a rate constant of 45.8 l. mole−1 sec−1. An additional energy transfer occurs between the excited free dye and the complex by either a singlet–triplet or a triplet–triplet mechanism. Kinetic analysis of the nylon‐complex energy transfer suggests that the triplet energy of nylon migrates 24 to 33 Å along the amide chromophores in an exciton fashion until an energy trapping complex is reached. Energy is then transferred by an exchange mechanism. Photo‐oxidative studies verify that the dye–nylon complex sensitizes the polyamide photo‐oxidative degradation at its own expense without dye photobleaching.
A study of coextrusion in a circular die
Authors: Han Chang Dae
Published: April 2003

An experimental study has been carried out of concentric and eccentric two‐phase flow of polymer melts in a circular die. For the study, a special die was constructed such that two separate streams of molten polymer could be supplied to the die inlet. Materials used for study were low‐density polyethylene, high‐density polyethylene, and polystyrene. In the experiment, two different capillary length‐to‐diameter (L/D) ratios were employed: 4 and 18. For a die having an L/D ratio of 18, wall normal stresses were measured, permitting the determination of the pressure gradient and hence the viscous property. For each set of extrusion conditions (L/D ratio, flow rate, component ratio), extrudate samples were collected. These were later carefully cross sectioned and photographed in order to examine the shape of the interface between the two components. It has been found that the lower‐viscosity components tends to wrap around the higher‐viscosity component, which is consistent with the previous observations reported in the literature.
Hydrogels of crosslinked poly(1‐glyceryl methacrylate) and poly(2‐hydroxypropyl methacrylamide)
Authors: Nierzwicki W. , Prins W.
Published: April 2003

Two hydrophilic polymer networks of different crosslinking density and varying reference degree of swelling were prepared from 2,3‐dihydroxypropyl methacrylate (glyceryl methacrylate) and N‐(2‐hydroxypropyl)methacrylamide. They were characterized by swelling and compression measurements, and the Flory‐Huggins interaction parameters were determined. The results reveal the importance of hydrophobic forces in the physical properties of poly(1‐glyceryl methacrylate). Poly(2‐hydroxypropyl methacrylamide) gels do not exhibit the presence of these specific effects.
Diffusion of deterrents into a nitrocellulose matrix. An example of diffusion with interaction
Authors: Brodman B. W. , Sipia J. A. , Schwartz S.
Published: April 2003

The diffusion of various concentrations of a deterrent (di‐n‐butyl phthalate) into a spherical, nitroglycerin‐containing nitrocellulose matrix was studied. It was concluded that the final concentration profile could best be explained by a diffusion with interaction mechanism. Based on this mechanism, a method for calculating the depth of deterrent penetration is presented.
A study of the performance and chemical characteristics of composite reverse osmosis membranes prepared by plasma polymerization of allylamine
Authors: Bell Alexis T. , Wydeven Theodore , Johnson Catherine C.
Published: April 2003

A study has been carried out of the performance and chemical characteristics of composite reverse osmosis membranes prepared by plasma polymerization of allylamine in a radio‐frequency electric discharge. It has been shown that membranes can be prepared which simultaneously exhibit a high rejection for sodium chloride and a high water flux. The primary factors influencing the quality of the membranes are the choice of substrate material, the deposition time, and the power supplied to the discharge. Variations in rejection and flux as a function of applied pressure indicate that water flows through the membrane by both diffusive and bulk flow. A reduction in rejection and an increase in flux are observed when membranes are operated for prolonged periods or at higher temperatures (up to 60°C). Elemental analysis of plasma‐polymerized allylamine shows that it can be represented by the stoichiometry C3H3.8N0.9O0.1. Infrared spectra show evidence for NH, CN, CN, and CH bond vibrations. ESCA spectra of the polymer surface show that the surface contains substantial amounts of both nitrogen and oxygen and that the nitrogen is present as either a nitrile or an imine group but not as an amine group. ESCA spectra of membranes used for reverse osmosis show that the surface loses nitrogen and gains oxygen with time and that this phenomenon is accelerated at higher operating temperatures. A decrease in rejection and an increase in flux accompanies these changes. It is postulated that most of the nitrogen in the polymer is present in the form of RR′CNH or RR′CNR″ type structures. The loss of nitrogen and gain in oxygen observed in the ESCA spectra of membranes run at elevated temperatures is explained by the hydrolysis of the proposed structures.
Block polymers from isocyanate‐terminated intermediates. III. Preparation and properties of cured diene–urea block polymers
Authors: Ambrose Richard J. , Hergenrother William L.
Published: April 2003

Isoprene–urea and butadiene–urea block polymers have been prepared by reaction of isocyanate‐terminated prepolymers with diamines and diisocyanates. It was found that the per cent of blocked urea in these copolymers is dependent on the isocyanate–diamine stoichiometry. Stress–strain data were obtained on sulfur‐cured copolymers. Stress levels at any given extension were directly dependent on the urea content, however, ultimate strength was maximized at about 35 wt‐% urea. Slight variations in urea structure produced rather dramatic changes in the modulus of these cured elastomers. Diamine–diisocyanate stoichiometry did not affect the physical properties of these cured copolymers at equal or excessive diamine concentrations. However, at excess diisocyanate levels, elastomeric properties deteriorated rapidly. Finally, stress–strain properties were affected by polymerization solvent. Copolymers prepared in hexane gave higher values of stress at low strains than corresponding elastomers prepared in toluene. These latter results are explained in terms of the nonaqueous emulsion in which the urea blocks form.
Radiation yield of hydrogen chloride in the poly(vinyl chloride) foils irradiated by accelerated electrons
Authors: Szymański W. , S̀mietańska G.
Published: April 2003

TheGHClvalues of PVC foils, containing 18% of dioctylphthalate, irradiated with accelerated electrons were studied after addition of various amounts of the stabilizers: (I) ethylene glycol bis‐β‐aminocrotonate, (II) calcium/zinc laurate + epoxy compounds, (III) calcium/zinc stearate, (IV) dioctyltin bis(octylthioglycolate). The effect of stabilization turned out to be very good, especially when stabilizer I was used. In the case of soft PVC foils in contact with water, elution of hydrogen chloride occurs. This creates difficulties in preparing PVC foils sterilized radiatively for medical purposes, especially if the foils are expected to be in contact with water.
Physical state of radiation‐polymerized polyethylene blends
Authors: Yamaguchi Kouichi , Yagi Toshiaki , Machi Sueo , Takehisa Masaaki
Published: April 2003

The physical state of the blends of radiation‐polymerized polyethylene with high‐density polyethylene was studied. Only one peak was observed in DSC heating curves of the blends quenched from the melt regardless of the each polymer content. In addition, transparency of the high‐density polyethylene was improved by melt blending with radiation‐polymerized polyethylene. This is a characteristic of high‐density polyethylene and radiation‐polymerized polyethylene blends different from high‐density and low‐density polyethylene blends. A new peak and/or a new shoulder, however, appeared in DSC heating curves of the blends with heat treatment at 110°, 120°, and 125°C. These results suggest that the physical state of the blends quenched from the melt is one where the crystallization of the radiation‐polymerized polyethylene is high hindered by the presence of high‐density polyethylene. The radiation‐polymerized polyethylene may remain mainly in a physical state similar to the melt. The haze value of the blends increased with heat treatment. The increase in the haze is caused by change in physical states, such as growth of spherulites and formation of microcrystals and microvoids, by the heat treatment.
Anionic graft copolymers. II. Extension of techniques of preparation and characterization
Authors: Lechermeier G. , Revillon A. , Pillot C.
Published: April 2003

Graft copolymers with poly(vinyl chloride) backbones and controlled amounts of polystyrene, poly(1,2‐butadiene), or poly(1,2‐butadiene–styrene) are prepared by carbanionic deactivation. Synthesis is by two methods: a classical step‐by‐step anionic polymerization technique and a new one‐apparatus technique. The reaction products are characterized by osmometry, selective extraction, and gel permeation chromatography to test the consistency of the three methods. A few words are said about the yields of grafting compared with temperature, size, and nature of carbanions.
Viscoelastic properties of tire cords
Authors: Willett P. R.
Published: April 2003

The viscoelastic properties of commercial rayon, nylon 66, and poly(ethylene terephthalate) tire cords have been investigated by dynamic mechanical techniques using the Vibron viscoelastomer DDV‐II. The effect of temperature, humidity, and geometric structure on the viscoelastic response has been determined for the tire cord assemblies. Subsequently, the underlying mechanisms and the polymer and fiber structural factors which influence them are discussed. Also, the consequences of the cord properties on tire hysteretic characteristics are discussed. This enables tires to be designed to meet specific service requirements. Characterization of materials in this way is becoming more important, particularly as the performance demands on tires become more stringent.
Audio‐frequency mechanical spectra of a butadiene terpolymer
Authors: Fitzgerald Edwin R.
Published: April 2003

Measurements of complex shear compliance (J* = J′ − iJ″) as functions of frequency and temperature for an unvulcanized sample of a butadiene terpolymer are presented. The measurements reveal the existence of a broad retardation dispersion at audio frequencies and temperatures between −30° and +35°C; but at temperatures below 0° and above 24°C, there are superimposed several series of sharp resonance dispersions. The appearance of these fine spectra below 0° and above 24°C correlates well with observed transitions in specific volume–temperature curves for the material at 1° and 24.5°C. Analyses of the spectra at 35.7°C reveal four separate series each with mode frequencies increasing as 1, 4, 9, 16, …, etc. in agreement with predictions of the momentum‐wave description of nonelastic deformation. Further, the ratios of frequencies for a common mode are in good agreement with the inverse atomic mass ratios of the atoms or atomic group to which each series is assigned. Thus, for the first mode of each series at 35.7°C, the frequency ratios are 1.000:1.142:1.220:1.335 for modes assigned to oxygen, nitrogen, the CH group, and carbon. These ratios, in turn, are in good agreement with the inverse atomic mass ratios, 1.000:1.142:1.230:1.333, as expected from momentum‐wave deformation theory. Examination of the microstructural and stress requirements for observation of nonelastic resonances in vibration experiments suggests that some type of one‐dimensional order extending over about 6 micrometers is present in the terpolymer below 0° and above 24°C, but is absent between these temperatures. The successful explanation of the dynamic mechanical behavior of this terpolymer, together with previous results cited for other materials, indicates the usefulness of the momentum‐wave theory of mechanical deformation in correlating microstructure and macroscopic mechanical response.
Changes in the CN group infrared absorption of dicyandiamide in the presence of moisture
Authors: Fountain Roger , Haas Thomas W.
Published: April 2003

A correlation between lap shear bond strength and an infrared absorbance ratio of reactive groups in a commercial dicyandiamide (dicy.)‐cured epoxy adhesive was explained by the presence of a hidden factor in the nitrile absorbance measurement of the dicyandiamide. The absorbance at 2210 cm−1 due to the CN of the dicy. was the denominator of the absorbance ratio in the correlation. Water present in the adhesive changed the two infrared absorptions in the 2200 cm−1 region of the spectrum resulting in a lower 2210 cm−1 absorbance than expected stoichiometrically for high (0.4%) water concentrations in the adhesive.
Styrene–divinylbenzene copolymers. II. The conservation of porosity in styrene–divinylbenzene copolymer matrices and derived ion‐exchange resins
Authors: Hilgen H. , De Jong G. J. , Sederel W. L.
Published: April 2003

The collapse of pores in styrene–divinylbenzene copolymers and corresponding ion‐exchange resins was studied during the removal of solvating liquids. The process can be followed in a most simple way by measuring the volume of the bead‐shaped copolymers upon drying. Other parameters observed during drying were the apparent density and incidently the internal surface. The collapse of pores is considered to be a result of cohesional forces when solvated polymer chains are approaching each other by loss of solvent. The effect will thus be more pronounced in gel‐type networks than in porous ones. In porous networks, the effect will be stronger in smaller pores than in larger ones. It is shown that crosslinks, increasing the rigidity of the structures, will favor the conservation of porosity. In ion‐exchange resins the pore stability is best when the material is in its lowest state of hydration. Generally, the collapse of pores is a reversible process. The collapsed material can in most cases be reswollen by the proper choice of solvent.
Method for correcting molecular weight from gel‐permeation chromatography. I. Skewing and concentration corrections
Authors: Nakano Seikou , Goto Yukitaka
Published: April 2003

The purpose of this paper is to present a metod to calculate real molecular weight averages of polymer samples from GPC chromatograms where the instrumental spreading functions are skewed and the concentration effect exists. In this method, it is assumed that (1) the skewed chromatograms of monodisperse polymer samples can be represented as resultant of halves of two different Gaussians, (2) the resolution factors are regarded as constant in the case of low sample loading, and (3) the peak elution volume is independent of the presence of other components in the case of low sample loading. Adequate monodisperse polystyrenes and the mixtures (binary, seven and ten components) were examined for this purpose; and the molecular weight averages calculated by this method were compared with the ones obtained by Rosen and Provder's method. From the results in our study, it is found that this method can be available for correcting molecular weight from GPC chromatograms except for very narrow high molecular weight samples.
Manganese(IV)‐initiated graft polymerization of vinyl monomers on polyamide fibers
Authors: Khalil M. I. , Abdel‐Fattah S. H. , Kantouch A.
Published: April 2003

The feasibility of potassium permanganate to induce graft polymerization of vinyl monomers onto nylon 6 was investigated. The graft yield is greatly enhanced by increasing the monomer concentration, reaction time, and temperature. The addition of metallic ions as promoters to the grafting medium accelerates the graft polymerization. A mechanism for grafting was proposed. The activation energy of initiation Ei for methyl methacrylate was calculated and found to be 5 kcal/mole. The overall rate of graft polymerization Rp depends on the monomer concentration.
Relationship between maximum extensibility of networks and the degree of crosslinking and primary molecular weight
Authors: Fedors R. F. , Landel R. F.
Published: April 2003

The relationship between network chain concentration and the maximum value of the extension ratio at break is discussed. Experimental data obtained from the literature are then used to test the theoretically derived dependence.
Autographic impact testing with increased efficiency and accuracy
Authors: Gonzalez H.
Published: April 2003

The objective of this work was to test modifications of an autographic impact device which would make autographic impact testing more suitable for routine work. Autographic impact devices allow the force transmitted to a specimen during impact to be recorded and displayed; thus, a detailed analysis of the impact process is possible. In addition to the measurement of the breaking energy, information on the load at which yielding begins and how the impact energy is absorbed by the specimen during impact can be obtained. Through the use of autographic impact devices, the impact resistance of plastics during an impact test has been shown to be composed of three basic areas of contribution: (1) an elastic deformation stage, (2) a plastic deformation stage, and (3) a tearing stage. The autographic method is not practical for routine evaluations because of the excessive time and effort necessary to set up, calibrate, and interpret each test. The following modifications of the autographic device were made to improve the efficiency of the method: (1) improved triggering technique, (2) improved calibration procedure, (3) elimination of the preloading force, and (4) a computer program to analyze the data much more efficiently. It is expected that these modifications will allow autographic tests to be performed efficiently.
Effect of short‐chain polymer on scission of long‐chain polymer in solution by high‐speed stirring
Authors: Nakano Akihiko , Minoura Yuji
Published: April 2003

The effect of short‐chain poly(methyl methacrylate) (PMMA) (P̄v = 950) on scission of longchain PMMA (P̄v = 6150) in solution by high‐speed stirring was investigated by measuring changes in [η] and GPC, stirring at 30,000 ± 500 rpm at 30° ± 5°C benzene solutions containing the above two polymers at several concentrations and at various mixing ratios. It was found that the scission of long‐chain PMMA was small or a little suppressed by addition of short‐chain PMMA. The scission‐suppressing effect of the coexisting polymers depended on the chain length. The longer the chain, the larger the effect. It was also found that the rate constant of scission, k, in Ovenall's equation had a certain significance in polymer systems with the same MWD but no significance in those with different MWDs.
Hydraulic permeation of liquids through swollen polymeric networks. III. A generalized correlation
Authors: Paul D. R. , Ebra‐Lima O. M.
Published: April 2003

An approximate equation was developed that permits calculation of the solvent tracer diffusion coefficient in a homogeneous swollen membrane from the measured hydraulic permeability coefficient. This relation was applied to data for 28 polymer–solvent systems that included 15 different organic solvents and 5 hydrocarbon polymer networks whose equilibrium swellings ranged from 16.1 to 91.5% polymer on a volume basis. The calculated tracer diffusion coefficient divided by the pure solvent self‐diffusion coefficient for these systems formed a unique correlation when plotted versus the polymer volume fraction in the membrane. This relation agreed well with tracer diffusion coefficient data in the literature for the benzene–natural rubber system measured by radioactive tagging. Discussion centers on the evidence for the validity of the equation developed and the role of hydrodynamics on diffusion in swollen membranes.
Molecular weight changes in polyacrylates on ultraviolet irradiation
Authors: McGill W. J. , Ackerman L.
Published: April 2003

Films of poly(methyl acrylate), poly(ethyl acrylate), and poly(n‐butyl acrylate) were irradiated by means of a high‐pressure mercury lamp in oxygen and nitrogen atmospheres, and the molecular weight changes accompanying degradation were studied as a function of radiation dose. Crosslinked material was formed in all cases though less crosslinking occurred in oxygen than in nitrogen atmospheres. Scission was the major reaction in the photo‐oxidation of poly(ethyl acrylate), and this was explained in terms of acetal formation. In a nitrogen atmosphere, the proportion of units fractured to the proportion of units crosslinked per unit radiation dose was constant for the three polymers. Gel permeation chromatographic studies showed the accumulation of low molecular weight fragments on prolonged photolysis, and this was explained in terms of a chain reaction mechanism.
Formation of free radicals in photo‐irradiated cellulose. IV. Effect of ferric ions
Authors: Hon Nyok‐Sai
Published: April 2003

The effects of wavelength and concentration of ferric‐ion photosensitizer on radical formation in cellulose irradiated with ultraviolet light were studied by means of electron spin resonance spectroscopy. Irradiations were carried out at 77°K. The absorption spectra of ferric complexes with cellulose model compounds, namely, glucose, lactose, and cellobiose, indicate that light absorption of iron–cellulose complex takes place at 365 nm, to initiate free‐radical formation. A three‐line electron spin resonance spectrum with a relative signal intensity 1:1:1 was observed when the sample was treated with 0.1‐mmole/l. ferric ion and irradiated with light λ > 3400 Å. Five‐line spectra with different signal intensities were observed when the sample was irradiated with light λ > 2800 Å and λ > 2537 Å, respectively. Further, the 1:1:1 three‐line spectrum was immediately changed to a five‐line spectrum when the sample was re‐irradiated with light λ > 2537 Å. The concentration of ferric ion strikingly affected the radical formation in cellulose and caused changes of the line‐shape and of the relative signal intensities of the spectra. The sample with 0.1‐mmole/l. ferric ion exhibited the 1:1:1 three‐line spectrum; however, when the concentration was increased to 20 mmoles/l., a prominent five‐line spectrum with relative signal intensity 1:2:0.8:2:1 was observed, when the sample was irradiated with light λ > 3400 Å. On the basis of these findings, it is apparent that several kinds of radical species can be formed by employing suitable wavelengths and varying concentrations of ferric ion.
Thermoplastic behavior of lignin with various synthetic plasticizers
Authors: Sakata Isao , Senju Ryoichi
Published: April 2003

The thermoplasticization of thiolignin (TL) and dioxane lignin (DL) with various synthetic plasticizers has been investigated. The thermal softening temperatures Ts of the lignin–plasticizer systems were measured applying the flow tester technique which is useful for investigating the thermal properties of polymers. It was found that the Ts of the lignins were lowered considerably as the solubility parameters (after Hildebrand) of the plasticizers approach close to that of lignin, namely, around 11. The lowering in the Ts of the lignins with the plasticizers was described by a linear equation with respect to the plasticizer concentration which ranged up to 20 wt‐%. The sorption of the limited amounts (< 5%) of water to the lignins also considerably decreased the Ts, however, the extent of lowering in the Ts by water sorption is less than that by the plasticizer addition at their contents over about 15%. The relationship of Ts to water content (up to about 30%) was curved, not linear. It was clearly shown that a combined use of the plasticizer and water brought about the most effective plasticizing for the lignins compared with the use of either of those alone.
Flow of polymer melts through a well‐lubricated, conical die
Authors: Shaw M. T.
Published: April 2003

The concept of gross melt fracture of polymer melts as a tensile failure in the die entry region was supported in this work by the observation of a dramatic increase in the melt fracture of poly‐ethylene extrudates upon lubricating thoroughly a conical, converging extrusion die. This flow, according to an analysis using a Fromm viscoelastic model, was found capable of producing axial tensile stresses in the extrudate in excess of 106 dynes/cm2 at the very moderate exit shear rate (no lubricant) of 100 sec−1. A calculated stress level of about 5 × 106 dynes/cm2 caused sharp, deep transverse cuts to appear in the extrudate. The ability of tensile stresses of this magnitude to fracture melts was demonstrated by separate experiments run in simple tension on molten rods, using similar rates and total deformations. A large qualitative difference between high and low‐density polyethylene in both these experiments was noted.
The effect of mixing on the modes of dispersion and rheological properties of two‐phase polymer blends in extrusion
Authors: Han Chang Dae , Kim Young Woo , Chen S. J.
Published: April 2003

An experimental study was carried out to investigate the effect of mixing on the state of dispersion and rheological properties in the two‐phase flow of polymer blends. For the study, blends of polystyrene and polypropylene were used, and two mixing devices were employed: a single‐screw extruder combined with a “static mixer,” and a twin‐screw compounding machine. Materials of various blending ratios were extruded at a constant temperature (200°C) through a capillary die having an L/D ratio of 20 (D = 0.125 in.). The state of dispersion in the two‐phase system was investigated from pictures taken of the microstructure of the extrudate samples. It was found that different mixing devices have a profound influence on the state of dispersion of one polymer in another. Also determined were the rheological properties of the two‐phase system investigated, from wall normal stress measurements. Our results show that, when shear stress is used as a parameter, the melt viscosity goes through a minimum, whereas the melt elasticity goes through a maximum. This is regardless of the type of mixing device employed, although the shapes of the curves are affected by the type employed. It is suggested that shear stress, instead of shear rate, be used in correlating the viscoelastic properties of two‐phase polymer systems.
Polymerization of organic compounds in an electrodeless glow discharge. VI. Acetylene with unusual comonomers
Authors: Yasuda H. , Marsh H. C. , Bumgarner M. O. , Morosoff N.
Published: April 2003

Polymerizations of acetylene with nonpolymerizing gases and vapors such as H2O, N2, and CO in a plasma generated by inductive coupling of 13.5 MHz radio frequency are investigated. It is found that acetylene copolymerizes with those comonomers and that properties of copolymers are distinctly different from that of plasma polymer of acetylene. The copolymerization with H2O has a significant effect in reducing the trapped free radicals in the plasma polymer (to a nonexistent level). Infrared and electron spin resonance (ESR) spectroscopies and elemental analysis of polymers are used to investigate the incorporation of H2O, N2, and CO into the plasma polymers.
Evaporation of solvent in mixed polymer systems of limited miscibility
Authors: Lloyd Douglas R. , Burns Charles M.
Published: April 2003

The evaporation of the solvent 1,2,3,4‐tetrahydronaphthalene from the ternary system polystyrene/polybutadiene/tetrahydronaphthalene was studied. Ternary solutions of precisely known weight concentrations were prepared and then dried under vacuum and elevated temperatures. When the solution was assumed completely dried to a solid, the solvent content was calculated by difference. The deviation between the two solvent contents, namely, that known by exact weighing of components and that calculated after drying, was found to be significant, the reason for this discrepancy resting in the fact that solvent is assumed entrapped in the polystyrene fraction of the polymer residue. The possibility of the formation of interpenetrating networks causing this solvent entrapment is discussed as is a possible means of achieving more efficient solvent evaporation.
Study of the degradation of polyurethanes. I. The effect of various metal acetylacetonates on the photodegradation of polyurethanes
Authors: Cheu Eng‐Liang , Osawa Zenjiro
Published: April 2003

Photodegradation of polyurethanes based on polyester diol‐diphenylmethane‐p,′p‐diisocyanate in the absence and presence of various metal acetylacetonates (Ti, V, Cr, Mn, Co(II), Co(III), Fe, Ni, Cu, Zn, Mg, Al, and Sn) was carried out; and the effect of these metal compounds on the degradation was examined by investigating the changes in the stress–strain properties and infrared‐ and ultraviolet‐visible spectra of the polymer. The results obtained were as follows: Co(III), Co(II), Cu, Ti, and Sn acetylacetonates substantially enhanced the photo‐oxidation of the polyurethane; and Al, Ni, and Zn acetylacetonates scarcely affected, or slightly retarded, it. The other metal acetylacetonates accelerated more or less the photo‐oxidation of the polymer. Co(III), Co(II), and Cu acetylacetonates extremely degradation. Wavelength of the irradiated light was responsive to photochemical reactions of functional groups in the polymer. CN and CO bonds of urethane groups were very accessible to the photo‐irradiation both without and with a glass filter, while methylene groups were rather stable to the irradiated light longer than 300 nm, through a glass filter. The effect of the metal compounds on the coloration of the polymer was also consistent with that of mechanical strength and infrared spectral changes.
Viscoelastic properties of plasticized amylose triacetate films
Authors: Chang Yung Ho , Murakami Kenkichi
Published: April 2003

The viscoelastic properties of amylose triacetate films plasticized with diisobutyl phthalate were studied. The modulus–temperature curves of diisobutyl‐phthalate‐plasticized amylose triacetate are typical for amorphous polymers with the decrease of amylose triacetate content. The glassy modulus is not affected by the incorporation of diisobutyl phthalate, but the rubbery modulus and glass transition temperature are depressed with increased diisobutyl phthalate. The rubbery modulus appears at first to maintain for a wide temperature range, then disappears with increased diisobutyl phthalate. From the results of modulus–time measurements and x‐ray diffraction patterns: in a system of amylose triacetate–diisobutyl phthalate, amylose triacetate exists as an amorphous polymer at all concentrations of amylose triacetate and it acts intermediately between semicrystalline and amorphous polymers at lower concentrations below about 90%.
Specific resistances of hydrophilic membranes containing ionogenic groups
Authors: Vacík J. , Kopeček J.
Published: April 2003

This paper deals with an investigation of the dependence of specific resistances on pH for hydrophilic membranes containing ionogenic groups. Membranes based on poly(2‐hydroxyethyl methacrylate) crosslinked with ethylene dimethacrylate were investigated. This basic structure was modified by copolymerization with ionogenic comonomers, i.e., methacrylic acid and/or diethylaminoethyl methacrylate. It is shown that the dependence of the specific resistance on pH passes through a maximum for cation‐active membranes at pH ∼ 3.5, for anion‐active membranes at pH ∼ 10, and for ampholytic membranes at pH ∼ 6. The effect of the content of ionogenic groups, network density, and the degree of neutralization of membranes on the above dependence is discussed. In the final part of the paper the results are compared with more hydrophilic systems based on poly(2‐hydroxyethyl acrylate) and it is shown that maxima in the dependence of specific resistances on pH can be suppressed by increasing the hydrophilicity of polymers.
Hydrophilic gels based on copolymers of 2‐hydroxyethyl methacrylate with methacrylamide and acrylamide
Authors: Dušek K. , Janáček J.
Published: April 2003

Copolymerization of 2‐hydroxyethyl methacrylate with methacrylamide or acrylamide and a crosslinking agent in the presence of water or other diluents yielded transparent hydrogels with a varying degree of swelling and varying sorption properties. The equilibrium degree of swelling increases with increasing content of amide groups and exhibits a maximum at ca. 60 wt‐% methacrylamide. The temperature dependence of swelling at 25–50°C changes from negative to positive with growing content of methacrylamide in the copolymer. The effect of the introduction of the amide groups can be interpreted by a weakening of the extent of hydrophobic interactions and by an increase in the role played by the hydrogen bonds. At the same time, the swelling‐in effect of the salting‐in anions decreases and the sensitivity to the sorption of metal cations increases. The increasing content of methacrylamide is reflected in an increase in the modulus, tensile strength, and elongation‐at‐break in gels swollen to the same degree. In gels swollen in water to equilibrium, the positive effect of methacrylamide units is compensated for by the negative effect of the increasing degree of swelling, so that the mechanical properties of these gels do not depend too much on the composition of the copolymer. The increasing content of acrylamide in the copolymer strongly raises the degree of swelling, which is reflected in poorer mechanical properties compared to poly(2‐hydroxyethyl methacrylate).
Experiments with soap‐free polymerization of styrene in the presence of alcohols
Authors: Homola A. M. , Inoue M. , Robertson A. A.
Published: April 2003

Polystyrene latexes have been synthesized by a method based on that Kotera et al.4 The polymerization rates and yields have been improved by the addition of an alcohol (methanol) to the reactants. The effects of varying the methanol content and other process variables on the polymerization and on the properties of the latex are reported.
Time lag and permeation rate in liquid/liquid dialysis
Authors: Lee Cheng H.
Published: April 2003

Time lag and permeation rate in liquid/liquid dialysis in general are found different from those in pervaporation. Theoretical treatments of time lag in liquid/liquid dialysis indicate that time lag, in certain cases, may be correlated to the “relaxation time” of the membrane, defined as the time required for the membrane to relax, or as the change of the permeation flux of diffusable species from initial flux to steady state due to the long time required for the dialysis solvent to reach steady state in the membrane. The permeation of dichlorobenzene in a Teflon‐FEP membrane for both the operations of liquid/liquid dialysis and pervaporation was measured as an example. It was found that the time lag in liquid/liquid dialysis is much longer than that calculated from a diffusion constant calculated from pervaporation. Permeation rate and activation energy are also different in both operations.
A comparison of methods for assessing the degree of interaction between plasticizers and poly(vinyl chloride)
Authors: Bigg D. C. H.
Published: April 2003

The Hildebrand solubility parameter δ, the Flory‐Huggins interaction parameter χ, dilute‐solution viscosities, apparent melting temperatures, and the equilibrium swelling of poly(vinyl chloride) (PVC) granules in plasticizer are compared as methods for assessing the degree of PVC–plasticizer interaction. Results from the empirical methods agree well with each other, but not with δ or χ. A quantitative activity parameter α, derived from χ, correlates well with all results other than δ values. A relative order of plasticizer solvent power has been established for nine plasticizers of widely differing structures and activities.
Préparation et etude de copolymères triséquencés isoprène et méthacrylate de méthyle
Authors: Guyon‐Gellin J. M. , Golé J. , Pascault J. P.
Published: April 2003

A convenient method is described for the synthesis of ABA triblock copolymers having a high vinyl polyisoprene as center block and poly(methyl methacrylate) as end blocks. Dynamic mechanical properties of these copolymers as a function of temperature are compared for different compositions (100%, 85%, 70%, 60%, 50%, and 30% of rubber) using solvent‐casting methods. Since the morphology is dependent on the method of preparation of the samples, five solvents of different solubility parameters were tested for the same copolymer (i.e., 70% polyisoprene by weight) to show their influence on mechanical behavior.
Thermoplastic urethane elastomers. III. Effects of variations in isocyanate structure
Authors: Seefried C. G. , Koleske J. V. , Critchfield F. E.
Published: April 2003

The dynamic mechanical properties of thermoplastic urethane elastomers have been compared for materials based on different diisocyanate structures, either 4,4′‐diphenylmethane diisocyanate (MDI) or an isomeric ratio of tolylene diisocyanate (TDI). Two comparable series of polymers were prepared with a polycaprolactone diol as the soft segment and varying concentrations of hard segments based on the respective diisocyanates and 1,4‐butanediol. Over the composition range studied, the polymer glass transition temperatures increased for the TDI‐based polyurethanes, but remained relatively constant for the series containing MDI. Differences in the degree of macroscopic order within the hard segments, due to variations in the symmetry of the diisocyanate structures, are suggested as an explanation of these dynamic mechanical properties.
A method for the dynamic measurement of diffusivities of gases in polymers
Authors: Felder R. M. , Spence R. D. , Ferrell J. K.
Published: April 2003

A method is presented for determining the diffusivity of a gas in a polymer from the response to a step concentration change in a continuous‐flow permeation chamber. The outlined procedure has several advantages over techniques currently in use: it requires simple numerical integration rather than curve fitting; it utilizes the complete response, rather than a portion of the response which falls within the region of validity of a short‐time asympotic solution of the diffusion equation; and it is applicable both to flat membranes and cylindrical tubes. An illustration of the method is provided by the measurement of the diffusivity of sulfur dioxide in a PTFE tube at several temperatures.
Quantitative explanation of the mechanism of corrosion of poly(tetrafluoroethylene) caused by active alkali metals
Authors: Jansta J. , Dousek F. P. , Řiha J.
Published: April 2003

The known method of surface treatment of poly(tetrafluoroethylene) (Teflon) by alkali metals was studied quantitatively. It was shown that the reaction proceeds by an electrochemical mechanism in solid phase. The alkali metal acts as anode and Teflon as a cathodic active material of a typical galvanic corrosion cell. A relation describing the rate of the penetration of this reaction into the depth of Teflon was derived.
Mono‐ and diquaternary ammonium cellulose cottons prepared in nonaqueous media
Authors: Perrier Dorothy M. , Benerito Ruth R.
Published: April 2003

Mono‐ and diquaternary ammonium cellulose anion exchangers in fabric form were prepared in nonaqueous media by reacting diethylaminoethyl (DEAE)‐cotton with an alkyl halide, RX, or a dihaloalkane, X(CH2)nX, respectively. The alkyl group was varied from CH3 to C18H35, and n varied from 5 to 10 in the dihaloalkanes. Electron emission spectroscopy for chemical analyses (ESCA) showed that approximately 70% of the amino groups in the original DEAE‐cotton were free amines. ESCA data showed that highest degree of quaternization of the free amine groups was obtained with CH3I but that diiodo and dibromo pentanes and decanes were also effective. Diquaternary ammonium cellulose exchangers of high nitrogen content had high wet and conditioned wrinkle recoveries, whereas the monoquaternary ammonium cellulose exchangers showed no improvement in wet or conditioned wrinkle recoveries. The monoquaternaries, like unmodified cottons and DEAE‐cottons, were soluble in cupriethylenediamine hydroxide (cuene), and cross sections of their fibers expanded when subjected to layer expansion techniques. All diquaternaries were insoluble in cuene, and their cross sections did not layer.
A new method for the measurement of dynamic shear mechanical properties of materials with a rheovibron viscoelastometer
Authors: Murayama Takayuki
Published: April 2003

The Rheovibron viscoelastometer is useful for obtaining dynamic tensile mechanical properties of films and fibers over a wide temperature range. Numerous studies of dynamic tensile mechanical properties have been made in the temperature range of −160°C to 250°C in an atmosphere at 0% relative humidity. However, no studies exist which show the measurement of dynamic shear mechanical properties of materials using the Vibron instrument. A new shear grip and procedure was developed for measuring dynamic mechanical properties of material in the shear mode using the Rheovibron instrument. The dynamic shear properties on a polyurethane elastomer and polyester film are presented. This technique will be useful in studies on the dynamic shear characterization of materials in conjunction with end use performance.
Ultrasonic properties of phenolic and poly(phenylquinoxaline) polymers
Authors: Hartmann Bruce
Published: April 2003

Longitudinal and shear sound speeds and absorptions were measured for a phenolic polymer and a poly(phenylquinoxaline) (PPQ) polymer, from room temperature to 70°C, at a frequency of 1.8 MHz. Phenolic specimens were cured at a maximum temperature of either 120°C, 135°C, or 180°C. The specimens varied in density from 1.217 to 1.229 g/cm3 with no correlation to curing temperature. Longitudinal sound speed in phenolic was found to depend only on density (or specific volume) and not directly on temperature or degree of crosslinking. Sound speeds and elastic constants, in phenolic, are not sensitive to cure temperature but sound a bsorption is: the higher the cure temperature, the lower the absorption. Hence ultrasonic absorption is a possible way to monitor or measure degree of crosslinking. Sound absorption is higher in phenolic than in PPQ, contrary to what is expected for a polymer with high sound speed. This high absorption indicates an additional mechanism of absorption in phenolic not found in PPQ. Also, the sound absorption increases with temperature in phenolic but is constant in PPQ. The Gruneisen parameter of phenolic appears high and that of PPQ about right when compared with other polymers. All of these results suggest there is a molecular transition in phenolic, but not PPQ. Further evidence for a transition comes from specific volume measurements as a function of temperature. The exact temperature of the transition and the molecular process responsible cannot, however, be determined from the measurements reported here.
Studies on blown film extrusion. I. Experimental determination of elongational viscosity
Authors: Han Chang Dae , Park Jong Yoo
Published: April 2003

Blown‐film extrusion experiments were carried out to investigate the elongational flow behavior of viscoelastic polymer melts at different melt temperatures. Materials chosen for study were high‐density polyethylene, lowdensity polyethylene, and polypropylene. In the study, isothermal blown‐film extrusion experiments were carried out in which the molten blown film traveled upward through a heated chamber of about 13 in. in length maintained at the same temperature as the melt. Axial tension was measured at the take‐up roller, the axial profiles of bubble diameter were determined by a photographic technique, and, from the samples collected, the variation in the film thickness along the axial direction was found. These measurements were used later to determine the elongational viscosity, using the force balance equations. It was found, in the experiment, that a careful control of the pressure difference across the thin film permitted one to maintain the bubble diameter constant, and, therefore, depending on the choice of the extrusion conditions, either a uniaxial or biaxial elongational flow was made possible. The experimental results show that, depending on the materials, elongation rate, and melt temperature tested, the elongational viscosity may decrease or increase with elongation rate, and may also stay constant independent of elongation rate. It was observed that the data of elongational viscosity obtained under uniaxial stretching in blown film extrusion is consistent with the data of elongational viscosity obtained earlier by use of the melt‐spinning operation.
Studies on blown film extrusion. II. Analysis of the deformation and heat transfer processes
Authors: Han Chang Dae , Park Jong Yoo
Published: April 2003

Having investigated the elongational flow behavior of polymer melts (part I of this series), we have carried out both theoretical and experimental studies in order to better understand the deformation and heat transfer processes involved in blown film extrusion. For the experimental study, nonisothermal experiments were carried out, using high‐density and low‐density polyethylenes. Measurements were taken of the axial tension, bubble diameter, and film thickness at a series of extrusion conditions (i.e., flow rate, pressure difference across the film, and take‐up speed). For the theoretical study, an analysis was carried out to simulate the blown‐film extrusion process, by setting up the force‐ and energy‐balance equations on the blown bubble moving upward. The approach taken in the theoretical study may be considered as an extension of the earlier work by Pearson and Petrie who considered the isothermal operation of Newtonian fluids. In the present study, However, we have considered the nonisothermal operation of power law fluids, whose rheological parameters were determined by an independent experimental study an described in part I of this series. Four highly nonlinear differential equations were solved numerically with the aid of the CDC 360 digital computer, using the fourth‐order Runge‐Kutta method. The mathematical model predicts the bubble shape, temperature profile, and film thickness as a function of the distance along the machine axis. Comparison is made of the experimentally observed bubble shapes with the theoretically predicted ones, showing a reasonable agreement.