bluuebunny/crossref_metadata_2025 huggingface dataset:
Entropy and melt fracture
Authors: Balmer R. T.
Published: April 2003

The onset of a well‐known flow instability commonly called “melt fracture” has remained one of the fundamental unsolved problems of polymer rheology. This work attempts to explain this phenomenon via a criterion based upon limitations to configurational entropy as dicated by the second law of thermodynamics. It is shown that the molecular orientation resulting from a sustained stress‐deformation rate field may be sufficient to affect the entropy balance of the system to the point of violation of the second law. The flow field then spontaneously changes, producing the condition called melt fracture, in a manner such as to prevent the violation of this law. Other theories on the mechanism of melt fracture are discussed in the context of the above criterion.
Thermal degradation of polyethylene in a nitrogen atmosphere of low oxygen content. III. Structural changes occurring in low‐density polyethylene at oxygen contents below 1.2%
Authors: Holmström Arne , Sörvik Erling
Published: April 2003

Samples of low‐density polyethylene, free from additives, were kept at temperatures between 284° and 355°C under nitrogen containing 1.16% oxygen or less. Changes in molecular weight distribution (MWD) and degree of long‐chain branching (LCB) were followed by gel chromatography (GPC) and viscosity measurements. Other structural changes were investigated by infrared spectroscopy and differential scanning calorimetry (DSC). Both chain scission and molecular enlargement occur simultaneously. Chain scission accounts for the formation of low molecular weight material and volatiles. Molecular enlargement reactions cause an increase in LCB and ultimately the formation of insoluble material. At lower temperatures (284°C) an increase in the high molecular weight end of the MWD is observed. The amount of olefinic unsaturation, carbonyl, and ether groups increase with degradation. Conjugated systems are formed. The formation of thin discolored and insoluble surface layers indicate that the attack of oxygen is diffusion controlled. The DSC thermograms undergo large changes at 3333° and 355°C, increasing with time and oxygen content. A reaction scheme for the thermo‐oxidative degradation of polyethylene is discussed. Both inter‐ and intramolecular hydrogen abstractions by peroxy radicals are suggested to occur. Thus, the formation of trans‐vinylene and ether groups results from intramolecular abstraction, while internal carbonyl groups are formed by intermolecular abstraction. Chain scission will be accomplished by both routes and together with “back‐biting” is suggested to account for the formation of volatiles. The formation of conjugated sequences causing discoloration is correlated with the formation of trans‐vinylene groups. Because of the restricted accessability of oxygen under our conditions, the reactions discussed previously for pure thermal degradation1 are also considered to be important. The molecular enlargement observed is thus proposed to be mainly due to the combination of alkyl radicals even when oxygen is present.
Gamma ray‐induced graft copolymerization of acrylamide and acrylic acid to nylon 6 fabric
Authors: Trivedi I. M. , Mehta P. C. , Rao K. N. , Rao M. H.
Published: April 2003

Kinetics of radiation‐induced grafting of acrylamide (Aam) and acrylic acid (Aa) to nylon 6 fabric were investigated employing a mutual radiation technique. Copper sulfate was used as the radical scavenger to reduce homopolymer formation. Formic acid was used for swelling, and its effect on grafting was studied. Maximum amount of grafting was doubled when formic acid was used for swelling nylon prior to, but not during, irradiation. The rate of grafting was not significantly affected if it was carried out in an atmosphere of air instead of nitrogen. The effect of monomer concentration, dose rate, and total dose on grafting has been studied. Rate of grafting was significantly higher when lower dose rates and monomer concentrations were used. Saturation grafting was proportional to monomer concentration up to 2.1M. Initial rate of grafting was proportional to monomer concentration. The rate of grafting of Aam was proportional to the dose rate to the power 0.25–1.0. A synergestic effect was noticed during grafting with mixtures of Aam and Aa (80:20; 20:80). Grafted fabrics showed considerable increase in moisture regain. Dyeability and tensile properties of the grafted fabrics were not significantly affected by grafting. Aa‐grafted fabrics did not melt up to 320°C, whereas untreated nylon melts at 215°C.
Physicochemical characterization of some fully aromatic polyamides
Authors: Gan L. H. , Blais P. , Carlsson D. J. , Suprunchuk T. , Wiles D. M.
Published: April 2003

The characterization of eight fully aromatic polyamides are described with the procedures required to yield film‐ and fiber‐forming materials. Solutions of these aromatic polyamides in dimethylacetamide were characterized by NMR and the effects of dissolved lithium chloride on these spectra investigated. The NMR resonances for specific protons in these polymers are assigned. The IR spectra of thin films and fibers of these polyamides are also reported, together with glass transition temperatures as measured by differential scanning calorimetry (DSC). The value of NMR and IR to identify specific polyamide homopolymers and copolymers is discussed.
Kinetics of vinyl chloride and vinyl acetate emulsion polymerization
Authors: Friis N. , Hamielec A. E.
Published: April 2003

The kinetics of vinyl chloride and vinyl acetate emulsion polymerization are reexamined. The validity of Ugelstad's model for systems with high desorption rate is confirmed by simulating conversion histories for both systems at different initiator concentrations and particle numbers. On the basis of the model, it is shown that at ordinary initiation rates, termination reactions are unimportant with respect to molecular weight development in both systems, and as a consequence, molecular weight development is independent of number and size distribution of polymer particles and of initiator and emulsifier level. Based on this conclusion, it is shown that in accordance with experimental facts, the molecular weight distribution obtained in vinyl chloride emulsion polymerization is the most probable distribution, and it is concluded that the number of long‐chain branch points per repetition unit is less than 2 × 10−4 at high conversions. In vinyl acetate emulsion polymerization, an almost logarithmic normal distribution is obtained. The distribution is strongly broadened by branching reactions with the number of long‐chain branch points increasing rapidly with monomer conversion. The increase of Mn with increasing conversion is due to terminal double‐bond polymerization, while the increase in Mw is due mainly to transfer to polymer.
Analysis of cotton fiber maturity. I. x‐ray study of phase transformation in various cottons
Authors: Kulshreshtha A. K. , Chudasama V. P. , Dweltz N. E.
Published: April 2003

An x‐ray diffraction technique is described for the determination of the extent of conversion of cellulose I to cellulose II lattice in partly mercerized cottons. This technique has been applied to obtain the degree of phase transformation, after subjecting various cottons to swelling in 12% (w/w) NaOH at 65% R.H. and 27°C. For the various cottons studied, a direct relationship is found to exist between fiber maturity and the untransformed cellulose after swelling.
Flow‐induced crystallization from solution: The relative effects of extension and shearing flow fields
Authors: McHugh Anthony J.
Published: April 2003

Calculations have been performed to evaluate the relative effects of extensional and shearing flow fields on both the chain elongation and crystal nucleation rate enhancement for polyethylene crystallizing from xylene solutions. Rheological behavior was evaluated by means of the elastic dumbbell model modified for nonlinear effects at high elongations, and nucleation rate effects were considered from an essentially phenomenological view point. Molecular weight effects were also incorporated explicitly in the computations. Results show that chain elongation and nucleation rate enhancement is far greater for extensional than for shearing flows. Semiquantitative comparisons with experimental results reported in the literature for various aspects of the flow induced process, including the important fractionation effects, are discussed. Modification of the dumbbell model to account for shear rate effects on the intrinsic viscosity is also discussed.
Electrostatic charge acceptance and decay of powder coating particles
Authors: Cheever G. Dale
Published: April 2003

Techniques have been developed to measure the acceptance and decay of electrostatic charge on a wide variety of powder coatings. The measurement of the initial charge carried by the powder was affected by the amount of powder deposited. The decay of charge occurred within four time scales: (1) 1 sec, electron loss to air and to the metallic substrate; (2) 1 to 5 sec, electron flow to neutralize induced positive charge; (3) 5 to 100 sec, rapid decay from powder; and (4) 1,000 to 10,000 sec, very long term decay. Since the decay of charge was markedly affected by moisture and composition, the decay properties can be controlled by these parameters. A mathematical model was constructed describing the quantitative charge decay during the time period of 100 to 10,000 sec. There was considerable heterogeneity within the powders with regard to charge acceptance and interaction with moisture. These measurement techniques give information concerning electrostatic effects on particle transport, adhesion, and polymer electrostatic behavior which are very important variables in a powder coating process.
Phenol–formaldehyde wood adhesive characterization by proton magnetic resonance spectroscopy
Authors: Steiner P. R.
Published: April 2003

Acetylation of phenol–formaldehyde (PF) wood adhesives afforded derivatives which could be characterized by proton magnetic resonance (PMR) spectroscopy. Through use of the chemical shift and integral parameters, relative comparisons were made for the degree of polymerization of resins prepared with different molar ratios. Additionally, PMR studies of these acetylated derivatives provided a means of determining methylol content and number of aromatic protons remaining, and to some extent gave an estimate of molar formaldehyde‐to‐phenol ratio. Experiments conducted with Ca(OH)2 and NaOH as catalysts showed the latter to be the more effective catalyst for PF systems.
Flame‐retardant poly(ethylene terephthalate)
Authors: Koch P. J. , Pearce E. M. , Lapham J. A. , Shalaby S. W.
Published: April 2003

Poly(ethylene terephthalate) containing hexabromobenzene, tricresyl phosphate, or a combination of triphenyl phosphate and hexabromobenzene, pentabromotoluene, or octabromobiphenyl was extruded or spun at 280°C into monofilaments or low‐denier yarn, respectively. Only combinations of the phosphorus‐ and halogen‐containing compounds resulted in flame‐retardant poly(ethylene terephthalate) systems, without depreciating their degree of luster and color quality. The melting temperature, the reduced viscosity, and the thermal stability above 400°C of these flame‐retardant systems were in most cases comparable to those of poly(ethylene terephthalate) itself. Phosphorus‐bromine synergism was proposed with flame inhibition occurring mostly in the gas phase.
Stabilization of poly(vinyl chloride). I. Change in color of poly(vinyl chloride) compounded with some metal soaps
Authors: Iida Takeo , Nakanishi Motoharu , Gotō Kunio
Published: April 2003

Poly(vinyl chloride) (PVC) with one or more metal salts added was colored by the action of heat to investigate the stabilization mechanism. The coloration and the color difference of heated PVC compound films varied according to the metal salt added. The decoloration of the colored compound films was advanced markedly in THF, DMF, acetone, and ammonia. On the other hand, the heated achromatic PVC film containing Cd/Ba soaps underwent an opposite change, from colorless to yellow orange, in the above materials. This means that the coloration of heated compound films may result from the formation of some complex (for example, π complex of the polyene with the metal chloride). Furthermore, the colored film with cadmium stearate was decolored by roll mixing with the colored film containing barium stearate. These results indicate that the stabilization with metal soaps may be founded on a physical phenomenon such aa an effect of complementary color.
Constrained optimization of cellulose acetate membrane using two‐level factorial design
Authors: Chian Edward S. K. , Fang Herbert H. P.
Published: April 2003

This work presents a method, the SUMT algorithm, to optimize the performance of the cellulose acetate (CA) membrane by maximizing the permeate flux subject to an equality constraint of salt rejection and a pair of inequality constraints for each variable. Three variables, i.e., (1) the concentration of formamide in the casting solution, (2) the time of evaporation of the membrane prior to gelling, and (3) the annealing temperature of the membrane, were selected for this optimization study. Experiments based on the two‐level factorial design were conducted for the determination of regression equations for both premeate flux and salt rejection. At a level of 97.00% rejection of a 0.5% sodium chloride solution at 600 psig, the maximum permeate flux of the CA membrane was predicted to be 14.52 gallons per day per sq. ft (gfd). This was later confirmed by experiments. The effects of the casting variables on membrane performance concluded in this study were consistent with those reported by other researchers.
Mechanism of corona–induced self‐adhesion of polyethylene film
Authors: Owens D. K.
Published: April 2003

Corona‐treated polyethylene films have been reported to exhibit strong self‐adhesion when joined together under conditions of heat and pressure that give no adhesion with untreated films. The present study of this effect has shown that the adhesion is completely destroyed by the application of any hydrogen‐bonding liquid to the adhesive joint and that the effects of liquids is completely reversible. Joints allowed to dry recover full strength. These facts together with the results of chemical reactions conducted on the treated film surface have established that the adhesive bond is a hydrogen bond. Corona treatment forms keto groups on the polyethylene chain; these groups enolize and the enolic hydrogens bond with carbonyl groups in the adjacent sheet of film when two sheets are heated together under pressure.
Study on crystallization of nylon 6 (polycapramide). III. Effect of “crystalline memory” on crystallization kinetics
Authors: Turska E. , Gogolewski S.
Published: April 2003

The effect of the initial degree of crystallinity on the isothermal crystallization kinetics from the melt of nylon 6 has been examined. The investigations were carried out in the conditions which allow to maintain a “crystalline memory.” For the investigations, dilatometric and microscopic methods were used depending on the temperature range used. It has been found that for samples of initial crystallinity up to 15% there exists a possibility of the growth of spherulites either from the sporadic or simultaneous nucleation depending on the crystallization temperature. For samples with initial degree of crystallinity higher than 15% the growth of spherulites occurred always from the predetermined nuclei within the investigated range of the crystallization temperature. The crystallization rate of the samples increased with rise in initial degree of crystallinity of the samples.
Effect of high‐abrasion furnace carbon black on the course of thiuram‐accelerated sulfur vulcanization
Authors: Duchác̆ek Vratislav
Published: April 2003

The effect of high‐abrasion furnace (HAF) carbon black on the course of the tetra‐methylthiuram disulfide‐accelerated sulfur vulcanization of natural rubber has been investigated at temperatures from 100°C to 140°C. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Results now available show (1) HAF carbon black does not alter the mechanism of the thiuram‐accelerated sulfur cure; it also has no qualitative effect on the kinetics of the vulcanization reactions involved. (2) Quantitatively speaking, essential differences take place. The rate constants of vulcanization rise considerably when HAF carbon black is used; there is a dependence on the HAF carbon black content of the rubber compound. Yet the activation energies of vulcanizations are practically the same as in carbon black‐free mixture, amounting to about 31 kcal/mole. (3) Measurements of the course of vulcanizations prove the reinforcing effect of HAF carbon black.
Polymerization of 4‐chloroformylphthalic anhydride with 4,4′‐diaminodiphenylether
Authors: Alvino W. M.
Published: April 2003

The polymerization of 4‐chloroformylphthalic anhydride with 4,4′‐diaminodiphenyl ether was investigated under a variety of reaction conditions. Both interfacial and solution techniques were used, with the latter method yielding the highest molecular weight polymer. Synthesis of high molecular weight polyamide‐imides requires the use of pure monomers, exclusion of moisture, and proper stoichiometry. Molecular weight control can be achieved by the addition of either aniline or phthalic anhydride. Heating of the resin solution for 1 hr at temperatures ≥ 50°C results in a large decrease in inherent viscosity as well as in the polymer properties. Tertiary amines such as triethylamine, when added to the precursor solution, markedly influence the viscosity of the resin.
Properties of poly[N,N′‐(4,4′‐diphenyl ether) 4‐amidophthalimide] film
Authors: Alvino W. M.
Published: April 2003

A high molecular weight polyamide–imide polymer derived from the reaction of TMAC–DAPE has been prepared and its film properties have been evaluated. Poly‐[N,N′‐(4,4′‐diphenyl ether) 4‐amidophthalimide] film has an excellent combination of mechanical, electrical, and chemical properties at room temperature and at 200°C. A comparison of the film properties of this material with those of a commercial polyimide film, Teflon, FEP, Nomex paper, and Mylar films is also presented.
Porous polymer carbons. I. Preparation and properties of porous poly(vinylidene chloride) precursor copolymers
Authors: Howard G. J. , Knutton S.
Published: April 2003

A series of porous solids has been prepared by the suspension polymerization of mixtures of vinylidene chloride and ethylene glycol dimethacrylate with a nonsolvating diluent. Alteration of the monomer composition and concentration leads to marked variations in the total porosity and pore sizes of the solid polymers. Scanning electron microscopy shows that the suspension‐polymerized beads consist of a microglobular interior encapsulated in a more coherent outer skin. This surface material affects the apparent density of the polymers and their behavior in mercury intrusion porosimetry and low‐temperature nitrogen adsorption.
Porous polymer carbons. II. Preparation and properties of porous poly(vinylidene chloride) carbons
Authors: Howard G. J. , Knutton S.
Published: April 2003

Suspension–polymerized copolymers of vinylidene chloride and ethylene glycol dimethacrylate have been converted into carbons by heating to 900°C. Poly(vinylidene chloride) homopolymer may melt on a first‐stage heating at ca. 200°C and consequently yields a fused 900°C carbon; restraining the first‐stage heating to slightly lower temperatures permits the retention of the polymer morphology which is then retained on subsequent carbonization at 900°C. The crosslinked copolymers do not fuse at 200°C and lose the dimethacrylate component, apparently cleanly, in the temperature range of 350–450°C and give 900°C carbons which are shrunken pseudomorphs of the parent polymer; all structural features are retained, including the characteristic skin of the polymer particles. Thus, the macroporous character of the carbons is controlled by both the crosslinker and diluent contents of the original polymerization recipe. The 900°C carbons are also microporous; hysteresis in nitrogen (77°K) isotherms is attributed to activated diffusion since carbon dioxide (196°K) isotherms are reversible. The microporosity of these dual‐porosity carbons depends on the content of crosslinking comonomer in the parent polymer, and possible reasons for this dependence are discussed.
Polymeric ultraviolet absorber
Authors: Mizutani Yukio , Kusumoto Koshi
Published: April 2003

Polymeric fine powder, prepared by polymerization of glycidylmethacrylate–divinylbenzene, was reacted with 2,4‐dihydroxylbenzophenone. The resultant polymer was effective as a polymeric ultraviolet absorber, and no migration was observed in polypropylene.
Rheological phenomena during the polymerization of styrene in a stirred tank
Authors: Ide Yoshiaki , White James L.
Published: April 2003

An experimental study of the bulk polymerization of styrene has been carried out. The rate of polymerization, molecular weight, and flow patterns around agitators as a function of conversion have been observed. The rate data are interpreted in terms of free‐radical polymerization kinetics. Duerksen and Hamielec's modified termination rate constant and initiator efficiency relations are generally consistent with our data. The flow patterns were interpreted in terms of the mechanics of viscoelastic liquids and observations for nonreacting systems. Specifically, at low conversions for spheres and similar agitators, the flow patterns are dominated by centrifugal forces with fluid drawn in at the poles and expelled at the equator for spherical agitators. At higher conversions, normal stresses interact with the centrifugal forces causing segregated secondary flow regions adjacent to the sphere. At very high concentrations, normal stresses dominate, yielding Weissenberg effects.
Some observations on the concept of the degree of crystallinity in cellulose fibers with reference to moisture effects
Authors: Ray P. K. , Bandyopadhyay S. B.
Published: April 2003

A conceptual effort has been made here to reconcile two approaches of defining the degree of crystallinity by the x‐ray diffraction method, (a) one as proportion of x‐ray diffracting matter in the entire fibrous material, and (b) another as the extent of qualitative perfection of the crystalline region only, since these two approaches often lead to opposite conclusions from the same set of observations.
Reaction during cure of a blocked isocyanate–epoxy resin adhesive
Authors: Hartz Roy E.
Published: April 2003

Model compound reactions of isocyanate sources with alcohols and an epoxy resin indicated that the major reaction product from the phenol‐blocked methylenebisphenylene diisocyanate and epoxy resin‐based adhesive dip for poly(ethylene terephthalate) cord was a polyurethane. A significant portion of the hydroxyl groups required for the reaction were formed by ring opening of the epoxide groups of the resin. The reaction rate for the unblocking of the isocyanate source was inhibited in the presence of polyester yarn finishes containing sulfated esters of fatty acids. Also, compounds containing carboxylic acid groups and sulfonic acid groups inhibited the unblocking step. Amines and their salts catalyzed the unblocking step. A mechanism for the polyurethane adhesive–polyester bond based upon physical interaction is postulated. The presence of certain nonsulfated ester finishes permitted good wetting of the polyester surface and penetration of the adhesive into the polyester. By contrast, sulfated ester finishes result in poor wetting and penetration by the adhesive on the polyester. By contrast, sulfated ester finishes result in poor wetting and penetration by the adhesive on the polyester. The latter finishes resulted in a weak boundary layer between the adhesive and the cord.
The kinetics of two‐phase bulk polymerization. I. Monomer and initiator distribution
Authors: Ludwico W. A. , Rosen S. L.
Published: April 2003

Rubber‐reinforced thermoplastics are produced commercially by dissolving a rubber in the monomer of a glassy polymer and commencing polymerization with a free‐radical initiator. Beyond a few per cent conversion, the incompatibility of the two polymers causes a phase separation, with each phase containing one nearly pure polymer. Subsequent polymerization occurs in each phase. The heterogeneous nature of the reaction can influence both the kinetics of the reaction and the amount of grafting in the product. The fact that only monomer which polymerizes in the rubber phase can possibly graft establishes an upper limit to the amount of grafting and hence influences the mechanical properties of the product. It is shown theoretically how unequal partitioning of monomer and initiator between the phases can influence the extent of grafting, and can also explain the kinetic rate reductions which have been observed in such systems. The distributions of monomer and benzoyl peroxide and azobisisobutyronitrile initiators between the phases have been determined experimentally for a styrene–polystyrene–polybutadiene system. They cannot account for the rate reduction observed in such systems.
Variability of ultimate properties of elastomers
Authors: Fedors R. F.
Published: April 2003

The measurement of the ultimate properties of elastomers is characterized by variability in the data. For example, when a sufficient number of specimens is tested, distributions in the values of the stress‐at‐break, strain‐at‐break, and time‐to‐break are commonly obtained. It is pointed out that such variability can be rationalized on the basis of variations in both the degree of crosslinking and in the size of naturally occurring flows present in the elastomer.
A computer implementation of frequency–temperature superposition for dynamic mechanical transformations
Authors: Engel P. A. , Sacher E.
Published: April 2003

The usual procedure for shifting dynamic mechanical data, involving the construction of a master plot, was compared with a simpler, computer‐implemented double shift procedure, which obviates the need for such a construction. Data reproducibility indicates that the double shift may successfully be shifted to frequencies greater than one decade to either side of the experimental range.
Analysis of a living polymer mixture by use of small‐molecule gel permeation chromatography
Authors: Cox James H. , Anthony Rayford G.
Published: April 2003

A procedure is presented for determining the concentration of polymer lithium, alkyllithium, and monomer by use of small‐molecule GPC. The system poly(styryllithium), butyllithium, styrene, and benzene are used to illustrate the method. The method as presented has a lower limit on the direct measurement of butyllithium concentration of 0.00005 molar. If the total carbon‐bound lithium is to be determined, the limit can be appreciably lowered. The styrenebenzene separation was obtained for concentration ratios of 1:5 or greater. Several suggestions are presented for improving these analyses.
Anomalous behavior of electrical conductivity and thermal noise in carbon black‐containing polymers at Tg and Tm
Authors: Klason Carl , Kubát Josef
Published: April 2003

Pronounced maxima in resistivity–temperature curves have been found at or above Tg for a number of amorphous polymers (PS, PMMA, PVC) containing a small percentage of carbon black. The maxima appeared only after a certain period of storage at T < Tg or at heating rates substantially higher than those used in cooling the samples prior to the measurement. For this reason, no maxima were observed during cooling. In crystalline polymers (PE, PP), maxima at Tm appeared both on heating and cooling. Marked relaxation effects (time‐dependent resistivity) were recorded in the Tg and Tm regions. Good agreement was found between resistivity and thermal noise data.
Factors affecting the photo‐induced graft copolymerization of methyl methacrylate onto fibrous polymer
Authors: Ogiwara Yoshitaka , Kubota Hitoshi , Yasunaga Toshio
Published: April 2003

The effects of sample swelling, photosensitizer, and solvent on the photo‐induced graft copolymerization of methyl methacrylate onto fibrous polymers such as Vinylon, nylon 6, and polyester were examined. Each separate factor, sample swelling, or solvent, or their combination, increased activity of polymerization. Only some sensitizer were effective. Studying the ESR spectra of photo‐irradiated polymers also showed that either the sample swelling, the photosensitizer, or the organic solvent is very effective for the formation of polymer radicals under irradiation.
The near infrared spectra of some polyamic acid resins
Authors: Crandall E. W. , Johnson E. L. , Smith C. H.
Published: April 2003

The absorption spectra of a series of polyamic acids prepared using various reaction conditions were studied using the ultraviolet (UV), visible, and near‐infrared (IR) ranges. The near‐IR proved most valuable; the amidization and imidization processes could be followed by observing the change of intensities of the 1950‐nm combination amine band and a band at 2300 nm assumed to be a function of the amide group.
A new rheological constitutive equation for the network model of polymer melts
Authors: Ronca G. , Conti W.
Published: April 2003

A new network model is suggested and a constitutive equation is developed on the basis of the assumed validity of Boltzmann's superposition principle for the shear stress. The predictions of the model concerning the relaxation behavior of polymer melts after steady shear or instantaneous deformation are compared to Lodge's theoretical results and to experimental data from the literature.
Formation of 2,4‐dinitrophenylhydrazones in high‐density polyethylene film irradiated with ultraviolet light
Authors: Kato Koichiro
Published: April 2003

Polyethylene films were irradiated in air by ultraviolet light. 2,4‐Dinitrophenylhydrazine was reacted on the irradiated films. The changes in amounts of carbonyl groups and 2,4‐dinitrophenynlhydrazones formed in the films were inferred by comparing their absorptions in the infrared and ultraviolet spectra, respectively. It seems that the contents of carbonyl groups formed in the amorphous regions in the high‐density polyethylene films by the irradiation were larger than the contents of carbonyl groups formed in the amorphous regions in the low‐density polyethylene films. The decreases in contact angles of water on the high‐density polyethylene films by the irradiation were larger than the decreases in the contact angles on the low‐density polyethylene films. The amounts of 2,4‐dinitrophenylhydrazones formed in the irradiated high‐density polyethylene films were less than the amounts of 2,4‐dinitrophenylhydrazones formed in the irradiated low‐density polyethylene films.
The structural color in the polymer blend of poly(methyl methacrylate) and polystyrene
Authors: Uemura Yukikazu , Aoyagi Masaya
Published: April 2003

Morphologic and optical studies were performed on the coloring of poly(methyl methacrylate) (PMMA) and polystyrene (PS) opal sheet. It was concluded that the origin of color is the polymer structure itself. There exist three structures in the colored polymer blend: small PS spheres are dispersed in the PMMA matrix, and each PS sphere contains smaller PMMA spheres within it. The dimension of the smaller PMMA spheres is of the same order as the wavelength of visible or near‐infrared light. The coloring measured by a spectrometer is well interpreted by the equation of structural color derived by Clewell qualitatively.
High‐density polyethylene melt elasticity—some anomalous observations on the effects of molecular structure
Authors: Mendelson R. A. , Finger F. L.
Published: April 2003

The die swell behavior of polymeric melts is a manifestation of melt elasticity of these materials and is of considerable commercial as well as fundamental importance. Hence, knowledge of the effect of such molecular variables as molecular weight (MW) and molecular weight distribution (MWD) on melt elasticity is important from both commercial and basic rheological points of view. The effect of these variables on melt elasticity of broad‐distribution polymers in the shear rate region of commercial interest is not unambiguously known, with most published theory and experiment being applicable to the low‐shear behavior of narrow‐distribution polymers and blends thereof. There is indication that die swell increases with increasing MW and broadening MWD. However, the current investigation of carefully characterized broad‐distribution HDPE materials prepared specifically to examine the effects of various molecular variables on melt elasticity does not support this contention and, in fact, provides consistent evidence for the opposite result, i.e., decreasing die swell with increasing MW or broadening distribution. The various samples studies were prepared by fractionation removal or addition of component molecular species or by polymerization designed to provide systematic variation of molecular species or by polymerization designed to provide systematic variation of molecular parameters. Overall MWD's of the samples were characterized, and die swell behavior was determined at 200°C over a wide shear rate region in a high L/D capillary both with and without annealing of extrudates. The results are presented showing effects of specific molecular variables.
Apparatus for torsional braid analysis by a digital data analyzer
Authors: Yano Shoichiro
Published: April 2003

As apparatus for torsional braid analysis (TBA), which is a variant of the torsional pendulum technique, a new method for recording the damped wave electrically, using an electric mater as a transducer, is described. In order to process a large volume of data, an instrument to print out digitally the amplitude and period of oscillation has been developed. The thermomechanical behavior of poly(vinyl chloride) is presented so as to demonstrate the use of the present TBA apparatus.
Fundamental studies on solvent dyeing with tetrachloroethylene. I. Diffusion of disperse dyes in poly(ethylene terephthalate)
Authors: Morita Zenzo , Kobayashi Ritsuko , Uchimura Koji , Motomura Hiromi
Published: April 2003

The diffusion of C.I. disperse Violet 1 and Violet 8 in poly(ethylene terephthalate) (PET) was investigated by the method of cylindrical film roll. The effect of tetrachloroethylene (TCE) on the properties of PET was also studied. The treatment of PET with TCE brought about a strong effect on the thermal properties without degradation of PET. The diffusion of disperse dyes in PET from the TCE dyebath was faster than that from the aqueous dyebath. The activation energies of diffusion in the temperature range of 60° to 95°C from the TCE dyebath were smaller than those from the aqueous dyebath. Some break points were observed in the Arrhenius plots of diffusion coefficients in PET from the TCE dyebath. They were lower than those observed at dry and water‐swollen states.
The influence of extent of polymerization on the thermal behavior of an epoxy‐based polyether resin
Authors: Lopata Eugene S. , Riccitiello Salvatore R.
Published: April 2003

A number of studies have been reported in the literature on the polymerization and thermal decomposition of epoxide resins. Lee1 and Anderson2 have both studied the thermal decomposition of epoxy resins, and they concluded that the characteristic exothermic peak (which can occur anywhere between 300° and 400°C) is caused at least partially by some reaction of the epoxide group. We have been investigating the thermal decomposition of an aromatic polyether resin which is produced by curing the diglycidyl ether of bisphenol A (Epon 825) with the catalytic agent trimethoxyboroxine (Fig. 1). DTA studies of the polyether in an inert atmosphere of N2 showed exothermic peaks at approximately 390°, 430°, and 470°C, with the major exotherm being the one at 430°C. Our investigation has shown the important role played by low molecular weight epoxides in these exothermic reactions.
Determination of diffusion coefficients of water in cellulose acetate membranes
Authors: Palin Michael J. , Gittens Gerald J. , Porter G. Brian
Published: April 2003

The determination of the diffusion coefficient for water in various porosity cellulose acetate membranes by a gravimetric method, using a humidified carrier gas, is described. It was found to be impossible to obtain meaningful results for very porous membranes, although dense membranes gave limiting values of diffusion coefficient at high carrier gas velocities. This phenomenon is explained in terms of the dissipation of the heat of sorption by the forced convection provided by the carrier gas. The variation of diffusion coefficient with concentration of water in dense cellulose acetate is explained in terms of clustering of water molecules in the polymer at high concentration.
The structural causes of the dyeing variations of nylon 66 yarn subjected to the false‐twist texturing process
Authors: Warwicker J. O.
Published: April 2003

The structural variations in nylon 66 caused by heat and the mechanical action of the false‐twist texturing process have been studied by measuring dyeing rates with Durazol Blue 2R, the determination of density, x‐ray orientation, and lateral order, and also by consideration of x‐ray small‐angle scattering data. It is concluded that the morphologic units are probably shish‐kebabs with straight‐chain cores between which the dye penetrates.
The determination of solubility parameters of solvents and polymers by means of correlations with other physical quantities
Authors: Koenhen D. M. , Smolders C. A.
Published: April 2003

Correlations of solvent solubility parameters with molar attraction constants and with properties like surface tension, dipole moment, and index of refraction have been explored. From relations found to be valid for solvents, it is possible to calculate the solubility parameters for polymers. A relation between the dispersion contribution to the surface energy of polymers (a measurable quantity) and the dispersion solubility parameter of polymers has been found which is similar to a relation established for low molecular weight substances.
The extensional flow of poly(methyl methacrylate) and high‐impact polystyrene at thermoforming temperatures
Authors: Lai M. O. , Holt D. L.
Published: April 2003

The work described in the present paper was performed to establish stress–strain–time relationships at plastic sheet thermoforming temperatures. The relationships are correlated with sheet‐forming “formability”. Specimens of poly(methyl methacrylate) at 165°C and high‐impact polystyrene at 122°C were extended to large strains at constant cross‐head velocities. Initial strain rates were between 4.2 × 10−3/sec and 1.6 × 10−1/sec. It was found that the flow stress σ was related to the true strain ε and the elapsed time t by a relation σ = Ktm′εn, where K is a constant and n and m′ are indices. The value of n for both materials was approximately one. The value of m′ was −0.052 and −0.33 for poly(methyl methacrylate) and high‐impact polystyrene, respectively. Tests were also performed in which the cross‐head velocity was increased in steps. It was found that the flow stress in these tests followed the same relationship as in the constant cross‐head velocity tests.
Siloxane zwitterions: Synthesis and surface properties of crosslinked polymers
Authors: Litt Morton , Matsuda Takehisa
Published: April 2003

The aminoalkoxysilanes, γ‐aminopropyltriethoxysilane and N‐aminoethyl‐γ‐ainopropyl‐trimethoxysilane, were chemically modified by ring‐opening addition of γ‐propanesultone. Surfaces coated with polymers from these new monomers have, at the surface, zwitterionic functions of sulfobetaines which are attached to the polymeric siloxane backbone. They showed good wettability, with critical surface tensions as high as 50 dynes/cm.
Nuclear magnetic resonance and stereoregularity of PVC
Authors: Abdel‐Alim Ahmed H.
Published: April 2003

The decoupled α‐proton spectrum of PVC was examined using a 220 MHz NMR spectrometer. All of the ten possible pentads were detected and an assignment is given based on Bernoullian statistics. This assignment is in general agreement with conclusions reached by previous workers except for some modifications in the heterotatic resonances. Triad tacticity data were obtained from the pentads and were used to estimate the differential enthalpy and entropy changes for bulk PVC polymerized in the temperature range 70°C to −50°C.
Grafting acrylonitrile onto wood pulp: Influence of process variables
Authors: Lepoutre P. , Hui S. H.
Published: April 2003

Graft polymerization of acrylonitrile onto a never‐dried bleached kraft pulp by the ceric ion process was not affected by the presence of air, nor by the use of technical‐grade ceric salt and unpurified monomer. The initial polymerization rate and final degree of conversion to grafted polymer increased with monomer and pulp concentration. An increase in the catalyst concentration also increased the initial rate and final conversion up to a maximum value, after which they leveled off. The amount of catalyst required for a given degree of conversion was minimized when operating at high concentration of pulp and monomer and when the catalyst was added last. Attainable graft level decreased when the pulp was dried but could be brought back to its normal level after the dried pulp was beaten. The molecular weight of the polymer increased with monomer concentration but was independent of ceric salt concentration when the latter was low. The number of grafted sites increased with ceric salt concentration.
Effect of microgels on the viscoelastic properties of poly(dimethylvinylsiloxanes)
Authors: Członkowska‐Kohutnicka Zofia , Raszczuk Alina
Published: April 2003

The course of dynamic viscosity η′ and modulus of elasticity G′ curves versus frequency of oscillations f was compared for poly(dimethylvinylsiloxanes) (PDMVS) samples of similar weight‐average molecular weights containing 0.1–0.2% by weight of microgels and free of microgels. It was found that the presence of microgels considerably changes the viscoelastic properties of PDMVS, particularly in the low‐frequency range. Only for samples with microgels a linear course of the above‐mentioned curves is observed. The content of microgels was determined by the light scattering method, whereas the η′ and G′ versus f values were obtained with the use of the Weissenberg rheogoniometer.
On the modeling of bulk poly(vinyl chloride) reactors
Authors: Ray W. H. , Jain S. K. , Salovey R.
Published: April 2003

A detailed mechanism and corresponding mathematical model is suggested for bulk PVC production. The model is more detailed and general than earlier models and is consistent with reported experimental data as well as new experimental evidence presented here. Equations are presented and computations performed showing the evolution of the particle size distribution of the polymer beads. The predicted particle size distributions are in reasonable agreement with the limited experimental data available.
A study of the combination of unsaturated perfluorocarbon binder and perfluoroammonium salt
Authors: Toy M. S. , Stringham R. S. , Rewick R. T. , Lubowitz H. R.
Published: April 2003

A composite of poly(perfluorobutadiene) and perfluoroammonium hexafluoroarsenate has been developed that can be used as an efficient source of fluorine atoms because the salt does not react with the polymer. This point has been demonstrated by showing that no more than trace amounts of NF3, which is formed in most reactions of perfluoroammonium salts, are formed by heating the composite to 120°C or by maintaining the composite at 80°C for four days. The small amount of NF3 that is formed can be explained as resulting from reactions with trace impurities.
Characterization of linear polyethylene fractions obtained by preparative GPC
Authors: Peyrouset A. , Prechner R. , Panaris R. , Benoit H.
Published: April 2003

A new preparative liquid‐phase chromatograph, operating at a high temperature (160°C), allowed us to fractionate a linear polyethylene sample in narrow fractions (polydispersity about 1.1). These fractions, characterized by viscosity, light scattering, osmometry, and GPC measurements, can be used to calibrate any analytical GPC, i.e., to determine the variation of molecular weight and axial dispersion versus the elution volume.
Hydraulic permeation of liquids through swollen polymeric networks. I. Poly(vinyl alcohol)–water
Authors: Ebra‐Lima O. M. , Paul D. R.
Published: April 2003

Poly(vinyl alcohol) membranes were prepared by crosslinking with terephthalaldehyde. Hydraulic permeation of water through this network structure was measured as a function of pressure for temperatures ranging from 18° to 35.8°C. The data were analyzed via a previously developed solution–diffusion theory for hydraulic permeation to give mutual diffusion coefficients. The activation energy for diffusion was found to be 6.5 kcal/mole which compared to the value of 4.3 kcal/mole for viscous flow of water indicates an influence of polymer–liquid interaction on the energetics of the diffusion process.
Biconstituent fibers from segmented polyurethanes and nylon 6
Authors: Saunders J. H. , Burroughs J. A. , Williams L. P. , Martin D. H. , Southern J. H. , Ballman R. L. , Lea K. R.
Published: April 2003

The characteristics of Monvelle, a new biconstituent fiber from nylon 6 and a segmented polyurethane, are reviewed briefly, and some of the technical problems inherent in producing such a fiber are discussed. The characterization of two series of polyurethanes which can be melt spun is given in detail. The chemical composition of the hard segment was maintained constant, being derived from 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol, in all polymers. In one series using poly(butylene adipate) of MW 2000 as the soft segment, the average hard segment content was varied from 33% to 54%. In the other series, the hard segment content was held at 43%, and three additional soft segments, each at MW 2000, were used: poly(ethylene adipate), polycaprolactone and poly‐1,4‐oxybutylene glycol (PBG). Characterizations include molecular weight distributions, thermal analysis, rheological studies, and selected small‐angle and wide‐angle x‐ray diffraction and polarized light microscopy. Crystallinity, melt viscosity, and activation energy of flow increased with increasing hardsegment content. Changes in the polyester soft segments had little effect on the properties studied, but with PBG the crystalline melting point of the polymer, without annealing, was higher and the melt viscosity was slightly higher than corresponding polyester‐based samples, in agreement with previous reports of sharper phase separation in polyether urethanes, compared to polyester urethanes.
A relation between toughness and the dynamic mechanical properties of polymer films
Authors: Sacher E.
Published: April 2003

A relation is shown to exist between toughness and the dynamic mechanical dissipation factor when both are evaluated under the same conditions. In addition to exploring why this relation exists, its limitations are considered.
Cellulose acetate ultrafiltration membranes
Authors: Kutowy O. , Sourirajan S.
Published: April 2003

Twenty‐three different casting solution compositions involving cellulose acetate E‐938‐3 (polymer, P), acetone (solvent, S), and aqueous magnesium perchlorate (Mg(ClO4)2:H2O = 1:8.5) (nonsolvent, N) were studied for making ultrafiltration membranes. These compositions (expressed in weight units) involved N/P ratios of 0.817 to 1.3 and S/P ratios of 3.5 to 5.33. It was found that by adjusting the values of S/P and N/P ratios in the casting solution composition, temperature of the casting solution, temperature of the casting atmosphere, and solvent evaporation period during film formation, a wide variety of cellulose acetate membranes useful for both ultrafiltration and reverse osmosis applications could be obtained. The results of a continuous test run at 50 psig for a period of 250 hr with a typical set of membranes, and their separation characterstics for a group of solutes ranging in molecular weight from 58 to 160,000, are presented.