bluuebunny/crossref_metadata_2025 huggingface dataset:
Reverse osmosis separation of organic acids in aqueous solutions using porous cellulose acetate membranes
Authors: Matsuura Takeshi , Sourirajan S.
Published: April 2003

Reverse osmosis data obtained using porous cellulose acetate membranes and aqueous feed solutions involving one of 22 monocarboxylic acids, seven dicarboxylic acids, and four hydroxycarboxylic acids have been analyzed. The operating pressure used was 250 psig in all cases, and the solute concentration used was ∼100 ppm in most cases. The results yield the following physicochemical criteria for preferential sorption at the membrane–solution interface with respect to the un‐ionized acid. At pKa = 4.2 (for monocarboxylic acids), or Taft number (σ*) = 0.6 or Hammett number (σ) = 0, neither the un‐ionized acid nor water is preferentially sorbed at the membrane–solution interface; at pKa < 4.2 (for monocarboxylic acids) or σ* > 0.6 or σ > 0, the un‐ionized acid is preferentially sorbed at the membrane–solution interface. For practical purposes, preferential sorption of water at the membrane–solution interface may be considered negligible in the σ* region of 0 to 0.6. The results also show that the criterion of acidity of the molecule governing the extent of its repulsion or attraction at the membrane–solution interface is valid for both ionized and un‐ionized acid. Further, when the acid molecule contains three or more straight‐chain carbon atoms not associated with a COOH group, the nonpolar character of the molecule also affects its separation in reverse osmosis.
Estimation of molecular weight distribution parameters for free‐radical polymerization
Authors: Reich Leo , Stivala S. S.
Published: April 2003

A method is described which allows the precise estimation of molecular weight distribution parameters p and A which pertain to free‐radical polymerizations. Thus, expressions are developed which allow the estimation of (1 − p) by means of a programmable calculator using molecular weight distribution data derived from GPC. Values of A may subsequently be calculated by means of a plot of one of the expressions given. Values of (1 − p) and A obtained in this paper were checked using theoretical values as well as by a comparison between calculated and observed values. The agreement between calculated and theoretical or experimental values indicates that the method presented for the estimation of (1 − p) and A is both reliable and relatively rapid. Previously reported methods for the estimation of (1 − p) and A have involved curve‐fitting trial calculations as well as more precise interpolation procedures. However, the latter are based on single‐peak maximum values.
Viscosity–temperature relationships for cellulose acetate–acetone solutions
Authors: Johnston H. Krik , Sourirajan S.
Published: April 2003

Viscosity measurements were made for dilute solutions of three grades of cellulose acetate (acetyl content 39.8%, molecular weight M̄v30270 to 46250) in acetone in the temperaturetrange of 10° to 35°C. The data satisfied the Mark‐Houwink equation, [η] =KM̄, where [η] = limiting viscosity number andKand α are Mark‐Houwink constants. The values of [η] and α decreased with increase in temperature, and straight‐line correlations were obtained for −d[η]/dtversus M̄vand log η versus 1/T(absolute temperature). The results are discussed in terms of solution properties of cellulose acetate in acetone and their possible relevance to reverse osmosis membrane science.
Preparation of cellulose triacetate and cellulose tricarbanilate by nondegradative methods
Authors: Hall David M. , Horne James R.
Published: April 2003

A method for obtaining triacetate having a D.S. of 3.0 has been obtained by acetylating the cellulose with acetic anhydride–pyridine reagent containing a catalytic amount of acetyl chloride. The process is rapid and nondegradative. Cellulose tricarbanilate can be prepared without recourse to pyridine solutions by using dimethylformamide (DMF) as solvent and triethylenediamine (1,4‐diazobicyclo[2.2.2]octane) as catalyst. The DMF solution of the cellulose tricarbanilate can be cast directly into films or the polymer easily recovered owing to the solubility of the reaction solvent and impurities in water.
The mechanism of carrier dyeing
Authors: Ingamells W. , Peters R. H. , Thornton S. R.
Published: April 2003

The accelerated rate of diffusion of disperse dyes into synthetic fibers caused by various dyebath additives (“carriers”) has been correlated with their plasticizing action. The rate of change in length of Acrilan filaments with temperature under dyebath conditions enabled the effects of the carrier on the Tg of the filaments to be measured, and the results for different concentrations of carrier at one temperature could be superimposed on a common curve by employing suitable shift factors. The shift factors, as well as the variations of the diffusion coefficients of dyes with temperature and carrier concentration, both matched a WLF relationship, confirming that the dyeing process is controlled by the segmental mobility of the polymer. Indirect experimental evidence suggests that the same relation will describe the effect of carriers on the dyeing of poly(ethylene terephthalate) substrates with disperse dyes.
Shear degradation of water‐soluble polymers. I. Degradation of polyacrylamide in a high‐shear couette viscometer
Authors: Abdel‐Alim A. H. , Hamielec A. E.
Published: April 2003

This manuscript reports an experimental investigation of the mechanical degradation of polyacrylamide in aqueous solution using a high‐shear couette viscometer. Equilibrium molecular weight distributions (MWD) at various shear stresses were measured by gel permeation chromatography. Degradation data indicate that the MWD becomes narrower at higher shear stresses, in general agreement with Bueche's midpoint break theory. An empirical correlation of the critical molecular weight and degrading shear stress is presented. It has the form

where Mc is the critical molecular weight and τ is the degrading shear stress in dynes/cm2.
Poly(vinyl alcohol) hydrogels. Formation by electron beam irradiation of aqueous solutions and subsequent crystallization
Authors: Bray James C. , Merrill Edward W.
Published: April 2003

Aqueous solutions of poly(vinyl alcohol) were submitted to varying doses of electron beam irradiation. By modification of the classical Flory‐Huggins equations appropriate to the initial state of solution of the polymer, the molecular weight between crosslinks, Mc, was calculated as a function of radiation dose, initial polymer concentration, and temperature. Following crosslinking in the solution state, crystallization was induced by dehydrating the network at temperatures above 90°C. Following dehydration, the polymer network was reequilibrated with water and its tensile properties compared with identically prepared hydrogels not subjected to crystallization by dehydration. Greatly enhanced values of ultimate tensile strength and resistance to tear result from the treatment producing crystallization, compared with those of the crosslinked but not previously dehydrated gels.
The influence of carbon black on the extrusion characteristics and rheological properties of elastomers: Polybutadiene and butadiene–styrene copolymer
Authors: White James L. , Crowder Jerry W.
Published: April 2003

An experimental study of the influence of carbon black loading, particle size, and structure on the extrusion characteristics of polybutadiene and butadiene–styrene copolymer synthetic rubber is described. The development of extrudate distortion and its mechanisms are considered. The viscosity and die swell have been related to black loading, particle size, and structure. Generally, it is found that black surface area and structure acts to increase viscosity and decrease elastic memory. This situation is analyzed in terms of the theory of nonlinear viscoelasticity. Two mechanistic theories are described which may explain this behavior. One theory is based on the continuum mechanics analysis of suspensions of particles in viscoelastic media. The rheological behavior of the black compounds is explained in terms of the increased severity of deformation in the polymer matrix surrounding the particle agglomerates. The second theory is based on the view of an entanglement network containing black particles. Polymer chains may be adsorbed onto the surface giving rise to increased entanglement densities.
Microcapillary oxidation‐reduction polymers
Authors: Hamilton William J. , Krause Kenneth J. , Wagner Herman B.
Published: April 2003

“Replica gel” polymers, characterized by their extremely high specific surface area, have not previously been prepared in “redox” form. Some illustrative syntheses are described, and the capability of these materials to oxidize acetic acid and to epoxidize oleic acid and cyclohexene is demonstrated.
An empirical model for viscosity of filled and plasticized elastomer compounds
Authors: Derringer George C.
Published: April 2003

An empirical model is proposed for viscosity of elastomers containing one or more fillers and/or one or more plasticizers. Only one coefficient for each filler and plasticizer is required, and the coefficients themselves are viewed as basic filler and plasticizer characteristics. The model has found wide applicability to many elastomer systems.
Interaction of gases with ablative composites. II. Water
Authors: Honeycutt R. H. , Wightman J. P.
Published: April 2003

The sorption of water vapor on two heat shield composites SLA‐561 and SLA‐561V and the SLA components was measured over the pressure range of 10−3 to 10 torr and at 25°, 30°, and 35°C. The sorption of water vapor by both the composites and the components varied directly with pressure and equilibrium was attained typically within 30 min. The sorption of water by SLA‐561V, phenolic spheres, and silica fibers varied inversely with temperature. The mechanism proposed for the interaction of water vapor with the SLA composites was a combination of absorption and adsorption.
Structural analysis of phenolic resole resins
Authors: King P. W. , Mitchell R. H. , Westwood A. R.
Published: April 2003

The chemical structure and cure characteristics of a group of phenolic resole resins were studied by means of three major analytical techniques. In particular, the effects on structure and reactivity of formaldehyde/phenol ratio and the type of reaction catalyst used were studied. Gel permeation chromatography was used to determine resin molecular weight distributions, and NMR, to determine chemical structural features. In this connection a selective oxidation procedure, converting free methylol groups to adehydes, has allowed unambiguous determination of methylene ether bridge structures to be made from the NMR data. The F/P ratio in a resole largely determines the type of molecular structures which are formed. However, triethylamine as a catalysts tends to favor methylene ether bridge formation, whereas sodium hydroxide favors methylene bridges. The rate and direction of subsequent thermal cure of the resoles prepared is shown by differential scanning calorimetry to depend markedly on the type of catalyst present during the curing stage. The DSC curing curves are interpreted in the light of the structural information provided by NMR.
Rapid assessment of weathering stability from exposure of polymer films. II. The effectiveness of different regions of the solar spectrum in degrading an ABS terpolymer
Authors: Davis A. , Gordon D.
Published: April 2003

A simple and rapid method has been developed to determine the relative effectiveness of the different regions of the solar spectrum in weathering a polymer. The method is based on measuring the rate of degradation of the polymer in film form, exposed outdoors under a range of materials which transmit different amounts of solar UV. The stability of an unpigmented ABS terpolymer has been examined using this method. It has been shown that the relatively small amount of solar radiation in the range of 295–340 nm accounts for 41% of the total degradation process. Longer wavelengths are shown to be progressively less effective; wavelengths greater than 450 nm (which account for nearly 90% of the total energy of the solar spectrum) contribute less than 5% to the degradation process.
Some analogies in the mechanical behavior of filled polymers
Authors: Lipatov Yu. S. , Babich V. F. , Rosovizky V. F.
Published: April 2003

The temperature and frequency dependences of complex shear modulus and mechanical losses were studied for expoxy resin composition in the presence of different amounts of quartz and polystyrene fillers. The data obtained were analyzed by the use of the Williams‐Landell‐Ferry method. It was shown that in the mechanical behavior of filled polymers, except for the well‐known temperature‐time analogy there exist some lows connected with the presence of filler. The change in filler concentration leads to the same change in the real part of complex modulus as change in frequency (concentration–time analogy), and change in temperature is equivalent to concentration change (temperature–concentration analogy). The existence of these analogies is explained by a change in deformation conditions for polymeric matrix in the presence of different amount of filler, by the existence of surface layers of polymer at the interface with solid filler, and by peculiarities of the mechanical behavior of filler. It is also established that the thickness of surface layer which was determined from experimental data depends on temperature and has an extremum in the temperature region of the α‐transition.
Triplet‐state quenching by photostabilizers of polyolefins
Authors: Adamczyk A. , Wilkinson F.
Published: April 2003

Paramagnetic nickel(II) complexes which are used as commercial photostabilizers of polyolefins are shown in laser photolysis studies to quench the triplet state of benzophenone in dilute benzene solution. The efficiency of quenching observed is less than that of diamagnetic square‐planar nickel(II) complexes which are more effective photostabilizers of polypropylene in “Xenotest” experiments. The observed rate constants for quenching of triplet benzophenone are compared with those observed by other workers for quenching of singlet oxygen, O2*(1Δg), in dilute solution. The relevance of these studies to the understanding of photodegradation in polyolefins is discussed.
An experimental study of threadline dynamics with emphasis on the effect of molecular weight on the elongational viscosity of melt‐spun poly(ethylene terephthalate)
Authors: Hill Jack W. , Cuculo John A.
Published: April 2003

A study of a melt‐spun threadline has been carried out to determine the effect of molecular weight on the elongational viscosity of the polymer being spun. Polymer chosen for this study was poly(ethylene terephthalate) having different molecular weights. Conventional nonisothermal spinning of the polymers was carried out with cooling by free convection. Threadline surface temperatures were measured by a null‐balance technique. Threadline tension at the take‐up device was measured, and samples of the threadline were taken to obtain linear density profiles. Nonlinear least‐squares fits were applied to the linear density data to obtain equations for velocity and elongation rate. These measurements were then used to determine the threadline elongational viscosity. Least‐squares fits were made to a polynomial relating absolute temperature and elongation rate to the elengational viscosity. These results were then used to determine an activation energy of elongational flow which was found to decrease with elongation rate. Elongational viscosity was found to increase with molecular weight.
A new method of moisture penetration measurement in protective coatings
Authors: Rybicky J. , Marton J. P.
Published: April 2003

Various methods are used by the paint and coating technologists to evaluate the resistance of protective coatings to penetration of water through them. This article intends to introduce a new, simple method for the moisture resistance evaluation. The method uses thin metal films as the sensor and is not absolute. However, it may be very useful for comparative experiments when the paint formulator seeks an optimum performance of coating developed for moisture protection.
Some peculiarities of mechanical breakdown of components in mechanical dispersion of polymer mixtures
Authors: Baramboim N. K.
Published: April 2003

This paper deals with the results of the experimental investigations of mechanical breakdown of individual polymers in mixtures with other polymers depending on different factors of mechanical treatment, polymer and mixture properties.
Strain behavior of particulate‐filled composites
Authors: Leidner J. , Woodhams R. T.
Published: April 2003

A theoretical expression has been derived to describe the strain behavior of rigid plastic composites containing spherical filler particles. By combining the predicted ultimate strength values with the appropriate modulus relationship, the complete stress–strain history and corresponding fracture energy may be estimated. The theoretical predictions were compared with experimental values obtained for a general‐purpose polyester resin containing spherical glass beads. The influence of silane coupling agents and filler adhesion was also evaluated. Although the experimental values showed considerable scatter, the general trend agreed fairly well with the theoretical predictions.
Kinetic study of the thermal decomposition of poly(oxypropylene) glycols by differential scanning calorimetry
Authors: Van Kim Vo , Malhotra Shadi L. , Blanchard Louis‐P.
Published: April 2003

The thermal decomposition of poly(oxypropylene) glycols was studied under nitrogen and dynamic operating conditions over the temperature range of 320° to 700°K by means of a differential scanning calorimeter. The differential energy losses due to changes in emissivity of the reference and sample pans were computed by modifying the baseline of the thermograms. Kinetic parameters obtained with the help of the Borchardt and Daniels theory indicate that the reaction is zero order and that the activation energy increases with molecular weight of the polymer. The rate of heating of the sample, the rate of flow of nitrogen, and the initial mass of the sample do not have significant effects on the kinetics of the decomposition.
Electron spin resonance studies on graft copolymerization of gaseous styrene onto preirradiated polypropylene. II. Preirradiation under vacuum
Authors: Nunome Keichi , Eda Bunzo , Iwasaki Machio
Published: April 2003

Graft copolymerization of gaseous styrene was carried out at 40°C onto polypropylene preirradiated under vacuum. In order to investigate the origin of graft initiation activity, ESR spectra of irradiated polymers were measured and discussed. Although there are about three times as many radicals trapped in the sample irradiated at −78°C as in the sample irradiated at room temperature, both the samples showed nearly same degree of grafting. This is due to the ineffectiveness of radicals trapped in the amorphous region for grafting. The samples irradiated under vacuum showed more grafting than those irradiated in an oxygen atmosphere. This is compatible with the conclusion in the previous paper that in grafting of polypropylene irradiated in an oxygen atmosphere the carbon radicals produced by hydrogen abstraction by trapped peroxy radicals are the effective active centers.
Electron spin resonance studies on graft copolymerization of gaseous styrene onto preirradiated polypropylene. III. Preirradiation under vacuum followed by exposure to oxygen at −78°C
Authors: Nunome Keichi , Eda Bunzo , Iwasaki Machio
Published: April 2003

Grafting of styrene vapor was carried out onto polypropylene γ‐irradiated under vacuum followed by exposure to oxygen at −78°C. A comparison with the results on polypropylene irradiated in an oxygen atmosphere leads to an interesting result. Two samples were irradiated at room temperature under vacuum and in an oxygen atmosphere, respectively, the former being followed by exposure to oxygen. Although irradiation was carried out at room temperature for either sample and nearly the same amounts of the peroxy radicals are trapped, the former showed more grafting than the latter. The origin of this difference was investigated by means of electron spin resonance. Significant differences were observed in ESR spectra as well as in isothermal decays of the trapped peroxy radicals. In the former sample, the trapped peroxy radicals had a higher mobility, and consequently a significant hydrogen abstraction by the peroxy radicals was observed during storage at 40°C. This result supports the conclusion of the previous paper that the radicals effective in the grafting reaction of polypropylene preirradiated in an oxygen atmosphere are the carbon radicals which are produced by hydrogen abstraction by the peroxy radicals.
Morphologic accessibility of wood adhesives
Authors: Chow S.
Published: April 2003

Accessibility of wood adhesives was determined using a potassium bromide‐embedding technique during resin cure. Cured resin was then extracted with water, followed by x‐ray analysis of residual potassium bromide retention in the adhesive matrix. Cured urea–formaldehyde (UF), phenol–formaldehyde resol (PF), and phenol–resorcinol formaldehyde (PRF) accommodated large quantities of potassium bromide. However, only PRF adhesive showed crystallization of trapped potassium bromide, suggesting the presence of large pore sizes in the polymer lattices. Both UF and PRF adhesives, after room‐temperature soaking, were equally resistant to water access. At higher temperature, water accessibility of UF increased greatly which may be attributed to thermal softening of the adhesive, while the accessibility of water to the PRF adhesive matrix was mainly a surface phenomenon and was not very temperature dependent. PF was highly accessible to water, even at room temperature, as a result of swelling from the presence of sodium hydroxide (catalyst). Accessibility of PRF adhesive was greatly increased by base (NaOH) solutions but not by acid (H2SO4) solutions. The UF resin showed slight increase of accessibility with increase in acidity and basicity of the water solution, but the accessibility increase of this adhesive in base solution was substantially less than that of PRF. The acid hydrolysis influence on accessibility increase of UF adhesive was far less severe than that of temperature.
Photostabilizing effect of Ni(II) chelates in polymers. II. Effect of diamagnetic chelates on polypropylene phosphorescence
Authors: Harper D. J. , McKellar J. F. , Turner P. H.
Published: April 2003

Examination of the phosphorescence emission form polypropylene shows the lifetime of the emission to be unaffected by a hydroxybenzophenone light stabilizer but significantly shorted by a diamagnetic Ni(II) chelate stabilizer.
The distribution of olefinic linkages in elastomers
Authors: Anderson J. N.
Published: April 2003

A method for determining the distribution of olefinic bonds in elastomers has been developed using dual detector GPC analysis of the polymer after derivatization with 2,4‐dinitrobenzenesulfenyl chloride. The method is particularly useful for determining the distribution of olefinic bonds in hydrocarbon copolymers having small levels of unsaturation.
Polar and steric effects in reverse osmosis
Authors: Matsuura Takeshi , Bednas M. E. , Dickson J. M. , Sourirajan S.
Published: April 2003

The effects of polar parameter Σσ* and steric parameter ΣEs on reverse osmosis separations of alcohols, aldehydes, ketones, and ethers (noncyclic) in aqueous solutions involving single solute systems and porous cellulose acetate membranes are discussed. The least‐squares and multiple‐regression analyses of solute transport parameter data show that the separation of aldehydes, just as that of alcohols, is predominantly a function of Σσ*, and that of ethers is predominantly a function of ΣEs, whereas that of ketones is best represented as a function of both Σσ* and ΣEs. The results also indicate that even where water is preferentially sorbed at the membrane solution interface, solute separation in reverse osmosis is affected by the nonpolar character of the solute molecule. A general expression for solute transport parameter in reverse osmosis is presented for further study.
Cellophane for kidney dialysis
Authors: Monk D. W. , Wellisch E.
Published: April 2003

A new cellophane has been developed for use as a membrane in artificial kidney dialysis. Modification of the standard viscose casting and regeneration conditions produced films having permeabilities highly competitive with the cellulosic membranes presently employed in kidney dialysis. These modified cellophanes have permeabilities superior to the European cuprammonium films for all molecular species investigated. The greater permeabilities were found to be due to a much increased sweiling of these films resulting in a very small amount of cellulose which forms the barrier to molecular diffusion. These new cellophane structures also exhibit reasonable wet strength characteristics. The cellophane membranes offer the potential for obtaining a domestic membrane supply. This study indicates that although additional development work is required to produce a highly competitive membrane, these early results look extremely promising.
Studies in chemically modified celluloses. VII. Periodate oxidation of cellulose dyed with reactive dyes
Authors: Shenai V. A. , Wagh S. P.
Published: April 2003

Periodate oxidation of cellulose and cellulose dyed with reactive dyes at 32°C in the presence and absence of various concentrations of alkali metal chlorides and sulfates has been studied. The extent of oxidative degradation undergone by cellulose and assessed in terms of copper number and cuprammonium fluidity of the oxidized dyeing, the oxygen consumption during the oxidation, and the rate constant were shown to be markedly increased by the presence of the salts in the oxidizing solution. Borohydride and chlorous acid treatment were used to further modify the periodate oxycelluloses, and the effect of these treatments on the properties was studied.
Dynamic mechanical properties of deformed rubber‐modified acrylics
Authors: Krause S. , Broutman L. J.
Published: April 2003

Rubber‐modified acrylic polymers with rubber contents of 0, 1, 4, 7, 10, 13, and 16% were investigated to determine the effects of cold deformations on their mechanical and dynamic mechanical properties. A Rheovibron was used to determine damping as a function of temperature at four frequencies. A cold‐rolled film and a cold‐drawn film, stretched until fully crazed, were investigated. It was shown that cold deformation produces a small shift in the glass transition temperature of the rubber phase while the activation energy remains nearly unchanged. Also, the nature of the damping curve of the glassy matrix near the glass transition temperature of the matrix is altered by the appearance of a shoulder in the curve.
New static and dynamic stiffness testers
Authors: Jellinek H. H. G. , Kachi H.
Published: April 2003

Instruments have been developed for the testing of stiffness of polymers in various gaseous environmental “atmospheres” over a large range of temperatures. They are based on the cantilever principle, where a small strip of a specimen is deflected statically or periodically. Changes in stiffness are measured as function of the bending force or power input, respectively. The dynamic instrument responds very sensitively to the onset of cracking in specimens due to ozone exposure. The static instrument is well suited for measuring the onset of rapidly increasing stiffness as temperatures are lowered.
Newer intermediates for plastics and coatings. III. Polyesters based on methylene‐di‐β‐oxynaphthoic acid
Authors: Kondekar Ninad , Potnis S. P.
Published: April 2003

A tetrafunctional dibasic acid, methylene‐di‐β‐oxynaphthoic acid (MDNA), has been used for preparation of unsaturated polyester resins. The films obtained from these products have excellent chemical and physical properties comparable to epoxy resins and to a large extent balance some of their shortcomings such as darker color, higher viscosities, and higher cooking temperatures. The possible applications of these resins are coatings where acid, corrosion, and thermal resistance are of primary importance.
DSC study on recrystallization of amorphous cellulose with water
Authors: Kimura Minoru , Hatakeyama Tatsuko , Nakano Junzo
Published: April 2003

The recrystallization of amorphous cellulose at various relative humidities was studied to clarify the relation between the amount of adsorbed water in cellulose and the molecular motion by the DSC method. The initial recrystallization kinetics of amorphous cellulose at various relative humidities were observed on the basis of the exothermic peak between 380° and 470°K in a DSC curve. The recrystallization occurred easily by conditioning at higher than 80% R.H., but hardly by conditioning at lower than 65% R.H. These facts suggest that the conformation of cellulose seems to be easily changeable if cellulose has a moisture regain which is approximately comparable to capillary water. When the Avrami equation was applied to the slope of calorific value versus conditioning time at higher than 80% R. H., it also appeared that the mode of recrystallization growth of amorphous cellulose exposed to water vapor is one‐dimensional.
Electroinitiated polymerization of trioxane dispersed in n‐hexane and n‐heptane
Authors: Mengoli Giuliano , Vidotto Graziano
Published: April 2003

The possibility of electroinitiating the polymerization of melted trioxane dispersed in nhexane and n‐heptane has been investigated. It was found that the addition under stirring of an electrolyte to these dispersions added a satisfactory electrolytic conductivity: this fact allows, by a fast current pulse, the anode transfer of a charge suitable to initiate the polymerization process. The kinetics of the polymerization do not exhibit substantial induction periods and depend both on the charge initially transferred to the system and on the diluent‐to‐monomer ratio. The molecular weights of the products, which are generally high, are controlled by the same parameters and by the extent of the monomer‐to‐polymer conversion. The effect on the process of the background electrolytes perchlorate and tetrafluoborate of tetrabutylammonium has been investigated, and the possible initiation mechanism has been discussed. The conditions also for obtaining thermally stabilized products by trioxane–1,3‐dioxolane copolymerization in the same systems have been shortly investigated.
A radial cell model for a tubular polymerization reactor
Authors: Schrenk L. , Kuester J. L.
Published: April 2003

A cell model for the prediction of temperature and concentration gradients in a nonisothermal tubular polymerization reactor at steady state is presented. Both radial and longitudinal gradients are considered. The complete molecular weight distribution is calculated as well as the leading moments of the distribution. The model is easily reduced to predict the performance of a plug‐flow tubular reactor, batch reactor, and continuous stirred tank reactor (CSTR). The specific polymerization mechanism application consists of free‐radical initiation, propagation, and combination termination.
Modified bead spring theory of dilute polymer solutions. III. Inclusion of multiple relaxation times
Authors: Everage A. E. , Gordon R. J.
Published: April 2003

A previously derived constitutive equation, representing a blending of the molecular dumbbell theory and a continuum theory of anisotropic fluids, has been extended to the multidumbbell (Rouse‐Zimm) case. The equation thus derived yields predictions equivalent to the Rouse‐Zimm theory in small‐amplitude dynamic shearing, with the exception that the introduction of an “effective molecular weight” as the concentration of polymer is increased is no longer required. In simple shearing flow, the theory predictions are far superior to those of the Rouse‐Zimm model, yielding realistic non‐Newtonian viscosity behavior, a positive primary normal stress difference, and a negative secondary normal stress difference. In stress relaxation following the cessation of steady shearing flow, the rate of relaxation is found to depend to the initial velocity gradient, but the effect is predicted to be too small to be observed experimentally in typical dilute polymer solutions. The effects of molecular weight, molecular weight distribution, and polymer–solvent interaction are explicitly accounted for, and in all cases the theory predictions are in excellent qualitative agreement with accepted experimental behavior.
Photosensitized degradation of polyolefins
Authors: Cernia E. , Mantovani E. , Marconi W. , Mazzei M. , Palladino N. , Zanobi A.
Published: April 2003

The effect of aromatically substituted dienes such as 1,1,4,4‐tetraphenylbutadiene (TPB) as sensitizers of the accelerated oxidative photodegradation of polyethylene has been studied. The mechanism of photosensitization has been investigated by ESR and IR spectroscopy, while the degradation rate has been monitored by following the change of the mechanical properties during accelerated indoor and outdoor weathering tests. It was found that TPB is an efficient sensitizer for the oxidative degradation of polyethylene. The degradation of the polymer takes place via 1O2 formation, and it was interpreted on the basis of two simultaneous processes. In the first, excited singlet oxygen (1O2) is produced by TPB itself or by ketonic impurities present in the polymer. In the second, 1O2 reacts with TPB giving benzophenone, peroxides, and other oxygenated products which in turn can promote the degradation of polyethylene. Irradiation carried out in the absence of air seems to rule out the possibility of a photodegradation mechanism via excitation of TPB to an upper excited state capable of hydrogen abstraction from the polymer.
Grafting of formaldehyde‐crosslinked and cyanoethylated cotton cellulose with acrylate monomers
Authors: Varma D. S. , Narasimhan Veena
Published: April 2003

Formaldehyde‐crosslinked cotton and cyanoethylated cotton were grafted with methyl, ethyl, and n‐butyl acrylates and methyl methacrylate using ceric ion as initiator. It was observed that the graft yields for formaldehyde‐crosslinked cotton were significantly higher than those for native cotton. An increase in the bound formaldehyde resulted initially in a decrease in molecular weight of grafts; but later on, an increase was observed. In the case of cyanoethylated cottons, increasing the degree of substitution resulted in increase in graft yields. Molecular weights of the grafts increase up to a D.S. of 0.3, after which they decrease. These results are interpreted in terms of rates of initiation and termination being influenced by production of additional sites due to swelling of cellulose fibers.
The effects of branching and other physical properties of anionic polyacrylamides on the flocculation of domestic sewage
Authors: Anthony Alan J. , King Paul H. , Randall Clifford W.
Published: April 2003

This investigation was undertaken to evaluate the effect of long‐chain branching of anionic polyacrylamides on the flocculation of domestic sewage. The polyelectrolytes were polymerized using a redox couple, selectively hydrolyzed, and then characterized by means of light‐scattering photometry. Coagulation tests were then employed to evaluate the synthesized polymers. The optimum polymer dose for suspended solids removal was used as the basis for evaluating each anionic polyacrylamide fraction with respect to its ability to flocculate domestic sewage. The results of this investigation indicated that as the weight‐average molecular weight increased, the optimum polymer dose decreased. For polymers of similar molecular weights and differing radii of gyration, as the radius of gyration increased, the optimum polymer dose decreased, indicating that the “linear” polymers were more efficient in removing suspended solids than the “branched” polymers.
Induced anisotropy of thermal conductivity of polymer solids under large strains
Authors: Peng Stevens T. J. , Landel Robert F.
Published: April 2003

A simple analytical form of induced anisotropy of heat conductivitykij(λ1,λ2λ3,T) of initially isotropic polymer solids results from employing the simplified theory of the three‐chain model of the non‐Gaussian network. The analytical form appears to be valid up to a stretch ratio of λ = 2.65, which is the limit of existing experimental data. The effect of induced anisotropy on the temperature distribution, due to the large deformations, is illustrated for a highly expanded spherical shell and a cylindrical tube under a steady‐state heat flow using the derived analytical form of the strain‐dependent heat conductivity.
Theory of reverse osmosis and some other membrane permeation operations
Authors: Lee Cheng H.
Published: April 2003

The general permeation equations for various transport operations using membranes were correlated according to the solution‐diffusion theory. It was shown that for some important conditions, the permeation properties for reverse osmosis can be generated from those of pervaporation. The use of reverse osmosis with pressure smaller than 2000 psi is calculated to be of limited use for the purification of water with small amounts of organic compounds.
Polymer composites through in situ matrix formation
Authors: Bless P. , Semen J. , Lando J. B.
Published: April 2003

Nylon 66 graphite composites have been prepared by the in situ polymerization of the monomer epitaxially crystallized onto the fiber surface. Nylon 66 monomer, whether oriented (crystallized from solution) or unoriented (deposited from an aqueous slurry) was found to polymerize to an oriented composite by a variety of techniques (spark discharge, resistance heating, and furnace heating). X‐ray diffraction has demonstrated that the matrix orientation corresponds to the polymer chains aligning themselves with the graphite crystal edges along the fiber axis. Scanning electron microscopy of fracture surfaces has shown excellent adherence between the fiber and matrix with fracture occurring mostly in the matrix material.
A mathematical model for polymerization of isoprene with n‐butyllithium in benzene
Authors: Magott Raymond J. , Ahmad Abu , Anthony Rayford G.
Published: April 2003

Isoprene was polymerized in batch reactors by use of bottle polymerization techniques at 20°, 30°, and 40°C at concentrations from 1 to 5 molar. Isoprene and n‐butyllithium conversions and molecular weight distributions were determined for different reaction times. Rate equations for the initiation and propagation reactions are presented. The importance of the association reactions in obtaining a narrow molecular weight distribution is illustrated.
Reverse osmosis separation of inorganic solutes in aqueous solutions using porous cellulose acetate membranes
Authors: Matsuura Takeshi , Pageau Lucien , Sourirajan S.
Published: April 2003

Using a modified form of the Born expression for the free energy of ion‐solvent interaction, to both the bulk solution phase and the membrane–solution interface, a parameter is obtained to express the repulsion of the ion at the interface. This parameter, called the free energy parameter for ions, is then related to solute transport parameter obtained from reverse osmosis experiments. Numerical values of this free energy parameter have been obtained for six monovalent and four divalent cations and for 12 monovalent anions. Using the experimental data for the reverse osmosis separation of sodium chloride as reference, the utility of the above parameter for predicting solute separation in reverse osmosis is illustrated for 32 other inorganic salts.
Thixotropic behavior of gel‐like systems
Authors: Lin O. C. C.
Published: April 2003

The changes of shear stress with time under constant shear rate and temperature of several pigmented acrylic polymer gels were examined. This behavior, known as thixotropy, was interpreted based on a model which separates the stress into two regions. Region I covers the growth of the stress up to the yield point, represented by a peak stress, F0. Region II covers the decay of the stress from the peak to the point it attains an asymptotic value, F∞. The material in region I is assumed to be elastic and in region II is represented by a dynamic equilibrium between structure A, which is non‐Newtonian and structure B, which is Newtonian. The transitions between A and B represent structure degradation and structure recovery. The concentrations of A and B are solved explicitly. The total shear stress is then evaluated following a theory proposed by Ree and Eyring and is shown to give relationship between shear stress–shear rate–shearing time in good qualitative agreement with experimental observations. The ratio (F0 − F∞)/F∞, defined as the coefficient of thixotropy, is sensitive to the fundamental physical chemical parameters of the system and is easy to measure. It is shown to be useful in the characterization of thixotropic materials such as gels. Methods for evaluating the elastic modulus and yield stress of the material in the gel state are also illustrated.
Stabilization of poly(vinyl chloride). II. Stabilization mechanism through metal soaps by complementary color action
Authors: Iida Takeo , Nakanishi Motoharu , Gotō Kunio
Published: April 2003

In a previous paper, it was pointed out that the stabilization mechanism through metal soaps might be affected by an effect of complementary color. In this work, the colors of heated poly(vinyl chloride) (PVC) films mixed with various metal soaps were investigated by using a differential colorimeter and a spectrophotometer. Monochromatic coloration was observed with PVC, PVC–Ca stearate, and PVC–Ba stearate systems. On the other hand, the phenomenon of color mixing was observed with PVC–Zn stearate, PVC–Cd stearate, PVC–Zn/Ca stearate, and PVC–Cd/Ba stearate systems. In particular, achromatic color remained with PVC–Zn/Ca stearate and Cd/Ba stearate systems for longer heating periods. This means that the stabilization mechanism for PVC compounded with metal soaps should be effected finally by subtractive complementary colors situated between polyene color and the color effected with the metal complex, in addition to being subject to the usual chemical stabilization mechanisms.
A continuum of molecular weight distributions applicable to linear homopolymers
Authors: Gloor Walter E.
Published: April 2003

An array or continuum of molecular weight distributions was set up, based upon the numerical solutions found for the theoretical log‐normal (LN) and generalized exponential (Gex) distribution functions, for a range of Mw/Mn = H ratios. For the Gex distributions, m > 0 in the continuum, and the theoretical Schulz–Zimm and Tung–Weibull distributions, in which m ≥ 1 for H ≤ 31, are located within the continuum. The LN distribution is the broadest, and the Gex‐related distributions become narrower as the numerical value of m increases. From literature data for polystyrene, poly(vinyl chloride), linear polyethylene, and polypropylene, one can assign to these polymers specific molecular weight distributions that fall within the continuum.
Surface impregnation of concrete bridge decks with polymers
Authors: Paul D. R. , Fowler D. W.
Published: April 2003

Polymer‐impregnated concrete has proven to be a strong and environmentally resistant material with many potential uses. One such application is to impregnate the surface of highway bridge decks to improve their durability. This paper reports on various aspects of research directed toward the objective of developing a practical and economical process for surface treating bridge decks with liquid monomers which subsequently are polymerized. This work has included (1) selection and tailoring the monomer–initiator system, (2) development of application and curing systems, and (3) evaluation of the resulting treatments by many different testing procedures. Considerable progress has been made toward increasing the durability of concrete slabs as shown by laboratory and small‐scale field tests and toward developing a practical method of application. Selected aspects of the fundamentals of surface treatments of highway bridge decks and details of the process and product as they have been developed to date will be presented here.
Studies on the biaxial stretching of polypropylene film. XI. Type II orientation during [2‐2FI]‐type stretching and its change by subsequent thermal contraction
Authors: Iwato Noboru , Tanaka Hiroshi , Okajima Saburo
Published: April 2003

In order to study the deformation mechanism of type II stretching, the change in orientation during the restretching and subsequent thermal contraction was investigated by x‐ray diffraction method. When a uniaxially oriented film is restretched, the lamellae which are stacked in the stretching direction by the stretching rotate as a whole toward the restretching axis. They rotate backward nearly reversibly during the thermal contraction, unless the restretching exceeds a balancing state, where the orientation in the film plane are equal in all directions. However, when the restretching degree is so high and the film orientation exceeds the balancing state, the lamellar rotation is accompanied by a complex phenomenon. It is considered from the wide‐angle and small‐angle x‐ray diffraction patterns that the lamellar surface becomes indented because of slippage between microfibrils composing the lamellae, and the microfibrils themselves bend at the boundary between the amorphous and crystalline regions within which the tilting of c‐axis also occurs. Upon contracting of the film; these changes recover, but even in the last stage of contraction the orientation approaches the symmetrical biaxial orientation but not the uniaxial orientation from which the biaxial orientation is started. These orientation and disorientation behaviors are not affected basically by a slight change in the restretching temperature and the degree of stretching.
Thermal properties of poly[N,N′‐(4,4′‐diphenyl ether) 4‐amidophthalimide] film
Authors: Alvino W. M.
Published: April 2003

The aging behavior of a polyamide–imide film was investigated. Film samples have been exposed to temperatures from 225° to 350°C for various times and the mechanical and electrical properties measured. This information was used to construct log life plots to gain an insight into the service life of this material. TGA and DTA results coupled with the information from the aging tests indicate that this film can be used at temperatures of 180° to 200°C for extended periods of time. Mechanical properties, especially elongation, of the film deteriorate faster than the electrical properties.
The effect of precompression on the load‐deflection relations of long rubber bush mountings
Authors: Hill James M.
Published: April 2003

For bonded cylindrical precompressed rubber bush mountings theoretical load–deflection relations are summarized for the four principal deformation modes of bushes which are sufficiently long so that end effects can be ignored. The relations are illustrated graphically for two types of initial compression.
The preparation and physical properties of polyester–poly(methyl methacrylates) triblock copolymers
Authors: Grezlak J. H. , Wilkes G. L.
Published: April 2003

Block copolymers having the basic structure of PMMA–PE–PMMA were prepared by the reaction of diisocyanate‐terminated polyesters with hydroxyl‐terminated poly(methyl methacrylate). The molecular weights of these copolymers varied from 7,500 to 47,000. The formation of block copolymers by this method was confirmed by infrared and molecular weight analyses as well as by the physical behavior of these materials. Block copolymers of molecular weight less than 21,000 were extremely brittle in nature. The stronger copolymers of molecular weight greater than 29,000 were examined as to their dynamic modulus and stress–strain behavior. This included the effect of added homopolymer on the stress‐strain behavior of such materials. To better understand their physical properties, the micelle theory of Inoue et al. was applied to these copolymers to help elucidate their morphologies.