bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoplastic elastomers via radical polymerization. I
Authors: Zaganiaris Emmanuel , Tobolsky Arthur
Published: April 2003

Thermoplastic elastomers were synthesized using a method for preparation of block copolymers introduced by Tobolsky and Rembaum. A hydroxy‐terminated polyester or polyether was chain extended with tolylene diisocyanate and capped with cumene hydroperoxide. The high molecular weight peroxycarbamate was used as initiator for polymerization of styrene, methyl methacrylate, or acrylonitrile monomer. Their physical properties were investigated by modulus–temperature curves. The effect of composition on modulus was also examined.
Studies on tack of pressure–sensitive adhesive tapes
Authors: Toyama M. , Ito T. , Moriguchi H.
Published: April 2003

It has been found that tack values of pressure‐sensitive adhesives are dependent on the surface energies for adherends. The parabolic curves with maxima are obtained from the plots of tack values versus critical surface tensions for the substrates. The maximum occurs at the region where the two surface tensions are almost similar. On the other hand, tack is measured as a dynamic value indicated as the force necessary to deform the adhesive mass. To explain why the tack values is controlled by the surface character of the adherend, a mechanism is proposed for adhesive bond breaking. Primarily, bonding occurs by wetting the surface with adhesive. When the adhesive bond breaks by external force, unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on the surface of the adherend. As the total area of wetted spots is determined by surface energy, the tack value is dependent on the critical surface tension of the adherend.
Study of sintering of poly(methyl methacrylate)
Authors: Kuczynski G. C. , Neuville B. , Toner H. P.
Published: April 2003

Sintering of poly(methyl metacrylate) spheres to the blocks of the same material was studied at temperatures ranging from 127° to 207°C. The analysis of the data based on the empirical Ostwald relation indicates that the predominant mechanism responsible for this process is non‐Newtonian viscous flow. The type of the flow changes with temperature of sintering, being pseudo‐plastic at lower temperatures and tending to dilatancy at higher ones.
Light emission due to peeling of polymer films from various substrates
Authors: Ohara Keiji , Hata Toshio
Published: April 2003

The intensity of the light which is emitted when polymer films are peeled mechanically from various substrates under varying conditions of vacuum was measured by a photomultiplier, amplifier, and pen‐writing oscillograph combination. The wavelength of the emitted light depends upon the sign of static charge generated on the surfaces of the film and the substrate by peeling. In the PVC‐glass sample system, the radiation consists of two bands of light, namely a shorter band (∼4900 Å) and a longer one (5200–5900 Å), but in other sample systems (e.g., PVC–copper, PVAc–glass), only the shorter band was observed. The latter band appeared at the higher degree of vacuum. Comparing these bands with discharge spectra of nitrogen gas and using various substrates, it was proved that the light of the shorter band can be attributed to the light of gas discharge and that of the longer one, to the light of glass luminescence. Generally speaking, the intensity of the light of the longer band is weaker than that of the shorter one. Total intensity of light changes with peeling speed and reaches a saturated value. This type of saturation may be interpretable if the streamer process is taken into consideration as a mechanism of electrostatic discharge. Total intensity of light depends also upon the pressure in the peeling chamber. At pressures of 10−2–10−3 mm Hg, the total intensity of light becomes minimum. This phenomenon is interpreted as a change of discharge potential according to Paschen's law under the condition of constant width of discharge gap.
On the explanation and correlation of turbulent drag reduction in dilute macromolecular solutions
Authors: Gordon R. J.
Published: April 2003

A simple mechanistic picture of turbulent drag reduction is proposed, based on the recent work of Corino and Brodkey for Newtonian fluids. Possible explanations are then considered from a phenomenological viewpoint, and the applicability of the well‐known dumbbell model toward this end is discussed. It is seen that the predictions of the “molecular” dumbbell model are surprisingly similar to those of the “continuum” convected Maxwell model utilized by Seyer and Metzner. Furthermore, the significance of the fluid relaxation time θ in characterizing the drag‐reducing effectiveness of a polymer solution is shown to follow from a number of qualitative arguments. A correlation is proposed, closely related to the recent correlations advanced by Rodriguez, Zakin, and Patterson, and Astarita, Greco, and Nicodemo. Some new aspects of this correlation are discussed.
Estimation of crosslinking of diallyl phthalate prepolymer. An investigation by infrared spectroscopy
Authors: Yoshida Katsunari , Kamada Harunori , Kumanotani Ju
Published: April 2003

The cure of the dially phthalate prepolymer was studied by means of infrared spectroscopy. It was found that the CC stretching band of the allyl group, which appears at 1647 cm−1 in diallyl phthalate monomer, splits into two bands at 1645 and 1651 cm−1 in both of the prepolymers and cured resins derived therefrom, the split band being found to be mostly useful to investigate the highly cured resin system of diallyl phthalate. On the basis of the split band, α is defined as a new parameter expressing a degree of residual unsaturation of diallyl phthalate prepolymers as well as highly crosslinked polymers, as revealed experimentally. Further, α proved to correlate closely with other parameters such as the iodine value measured for the prepolymers, and swelling weight ratio or Barcoal hardness (hot) measured for the cured resins, it becoming evidently a convenient parameter to examine the degree of crosslinking of diallyl phthalate resin system. The effect of metal molds employed upon cure of prepolymers was also elucidated from the measured α values.
Rates of crystallization of copolyamides. II. Random copolymers of nylons 66 and 6
Authors: Harvey E. D. , Hybart F. J.
Published: April 2003

Rates of crystallization of copolyamides of nylons 66 and 6 have been measured by a photometric technique using a hot‐stage microscope. The copolymers all show some crystallinity, but the temperatures of crystallization are reduced as more comonomer is introduced. A close correlation between melting and crystallization behavior is observed. The copolymerized component is acting as a diluent rather than entering the homopolymer crystal.
Shear degradation of polymer solutions
Authors: Ram A. , Kadim A.
Published: April 2003

Shear degradation of polyisobutylene solutions was studied in laminar flow through capillaries. A special apparatus was designed with a view to a controlled shear history. The various effects of initial molecular weight, concentration, temperature, and shear stress at the wall on the final degradation product are combined in a single parameter representing the minimum force required for degrading a polymer sample to its final state.

This work is based on the M.Sc. Thesis of A. Kadim, submitted at the Department of Chemical Engineering, Technion—Israel Institute of Technolog, Haifa, Israel.
The γ‐radiolysis of zeocarb 225 cation‐exchange resins
Authors: Clay P. G. , Hall G. R. , Rahman M. K. , Rashid M.
Published: April 2003

Irradiation of Zeocarb 225 cation‐exchange resin leads to a loss of exchange capacity and the formation of SO42− ions. G(SO42−) is dependent upon the relative amount of water associated with the resin and may be reduced by the addition of scavengers, reactive towards hydroxyl radicals. The results suggest that both direct and indirect radiolyses are able to bring about desulphonation and that hydroxyl radicals are responsible for the indirect radiolysis.
Pressure‐induced diffusion of organic liquids through highly swollen polymer membranes
Authors: Paul D. R. , Ebra‐Lima O. M.
Published: April 2003

The transport of twelve organic liquids through a highly swollen rubbery membrane has been studied. The transport was caused by a pressure applied to the liquid above the membrane (reverse osmosis). The flux was found to be a highly nonlinear function of the driving pressure. Detailed thermodynamic and diffusion theories are proposed to describe the transport in terms of the concentration gradient of the swelling liquid within the membrane induced by the applied pressure. The data and the theory appear to be in very good agreement. The diffusion coefficients deduced from the data are explained in terms of a hydrodynamic mechanism of diffusion. Highly swollen membranes can yield very high liquid fluxes at moderate pressure and consequently may have applications for performing certain separations.
The brittle fracture of amorphous thermoplastic polymers
Authors: DiBenedetto A. T. , Trachte K. L.
Published: April 2003

The brittle fracture properties of polyphenylene oxide, polysulfone, polycarbonate, and poly(methyl methacrylate) thermoplastic polymers were investigated over a wide range of temperatures. Fracture energy measurements were made using double edge‐notched tensile samples. Tensile strength, tensile strain, and initial elastic modulus were measured for calculation of the fracture energy and further analysis of the polymer behavior. It was found that mechanical transitions in the tensile properties corresponded reasonably well with transitions in the fracture energy in the temperature range investigated. Fracture surface photographs permitted visual analysis of the fracture process. It was found that the roughest fracture surface corresponded to the maximum in the fracture energy for a given polymer. A theory for prediction of polymer tensile yield strain is presented, based on the volume dilation concept. The implications of this theory are discussed in terms of the crack tip flow process leading to brittle fracture.
The properties of polyethylene crystallized under the orientation and pressure effects of a pressure capillary viscometer
Authors: Southern John H. , Porter Roger S.
Published: April 2003

High‐density commercial polyethylenes have been crystallized under the combined orientation and pressure effects available in the Instron capillary rheometer. The samples so formed were found to have a high degree of crystal perfection and crystal orientation in combination with the unusual property of transmitting visible light. The procedure for forming the crystal structure is elucidated. X‐Ray and differential scanning calorimetry techniques were utilized to initiate a study of the structure. Evidence is presented that is consistent with the presence of an extended chain component in the crystal structure.
The synthesis of selenium condensation polymers using bis(2‐hydroxyethyl) selenide and bis(2‐aminoethyl) selenide
Authors: Kroll Harry , Bolton Edward F.
Published: April 2003

Procedures were developed for the large‐scale synthesis of bis(2‐hydroxyethyl) selenide and bis(2‐aminoethyl) selenide. These bifunctional selenides were converted into a series of polyesters, polyureas, and polyurethanes. Methods of syntheses and properties of these condensation polymers are described.
A determination of crosslink density from compression modulus data
Authors: Melley R. E. , Stuckey J. E.
Published: April 2003

A comparison of the crosslink densities calculated from compression modulus and stress–strain measurements is made for a series of natural rubber vulcanizates. Errors resulting from the use of accepted approximations and the effect of sample dimensions are also investigated.
Network formation in poly(ethylene terephthalate) by thermooxidative degradation
Authors: Yoda Kentaro , Tsuboi Akio , Wada Minoru , Yamadera Reizo
Published: April 2003

Gelation of poly(ethylene terephthalate) by heating at 263°–300°C was investigated. Under nitrogen flow, crosslinks were scarcely formed. However in air, degradation and crosslinking were common, and these were accelerated by purging gaseous and sublimable degradation products out of the system with a stream of air. The main component of the sublimate was terephthalic acid. Infusible and insoluble gel was treated with methanol at 260°C, and then the methanolysis products were separated into two parts. The methanol‐insoluble part exhibited a polyene structure with ester groups, and the methanol‐soluble part contained dimethyl terephthalate, ethylene glycol, and some 1,2,4‐butanetriol. To clarify the relation between the crosslinking and the formation of vinyl ester groups, the degradation of vinyl methyl terephthalate was studied. Thermoxidative degradation of linear polyesters other than poly(ethylene terephthalate) was also studied. Poly(ethylene isophthalate) and poly(ethylene sebacate) were easily gelated. However, poly(trimethylene terephthalate) and poly(neopentyl terephthalate) were scarcely gelated. The primary reaction leading to crosslinking is assumed as follows. At first, the random scission of polyester chain may take place forming carboxylic acids, vinyl esters, aldehydes, etc. After accumulation of vinyl esters to some extent, vinyl polymerization of the esters takes place and network structures are formed.
Preparation and properties of imide–pyrrone copolymers
Authors: Bell Vernon L.
Published: April 2003

Two series of copolymers containing imidazopyrrolone (pyrrone) and imide groups were prepared by solution polymerization. Thin films of the copolymers showed a general increase in the tangent modulus and a decrease in elongation with increasing pyrrone content. The copolymers were more resistant to degradation by strong acids and bases than the corresponding polyimides. The thermal stabilities of the copolymers in air improved with increasing imide content, while the thermal stabilities in a vacuum improved with increasing pyrrone content. These copolymers represent a way to combine the desirable properties of both classes of homopolymers.
Electroplating on crystalline polypropylene. I. Compression molding and adhesion
Authors: Fitchmun D. R. , Newman S. , Wiggle R.
Published: April 2003

A direct relationship between polymer processing and metal adhesion is evident from studies of compression‐molded isotactic polypropylene (PP). Cooling rate, nature of the mold surface, and after‐plated annealing are shown to affect the peel adhesion of the plated components. This report described (1) the relation of compression molding variables to polymer surface morphology, (2) the oxidative cracking behavior of the surface due to pretreatment with chromic–sulfuric acid in terms of crystallite orientation and crystallinity, and (3) the effect of surface crack patterns on adhesion.

The nature of the mold surface is the single most important variable for controlling the surface morphology of PP. Compression molding PP against oxidized aluminum or copper produces a spherulitic surface, whereas molding the polymer against Mylar or Teflon produces a transcrystalline surface. Surface etching of PP homopolymer produces sponge‐like crack patterns characteristic of the morphology. Radial patterns are observed on spherulitic surfaces and random patterns, on transcrystalline ones. The various surface patterns are developed in the oxidative process by swelling of amorphous material followed by oxidative stress cracking and dissolution.

Metal‐to‐polymer adhesion, as measured by the peel test, may involve failure at the interface or within the polymer. Three factors are shown to be important: (a) the geometry of the interface, (b) the diminished strength of the polymer surface arising from attack by the oxidizing acid, and (c) the crystallinity of the fissured polymer surface. The highest peel values are associated with conditions that lead to deep and frequent fissuring of the polymer surface and minimum oxidative damage.
Temperature and microstructure dependence of the Rheo‐optical properties of polybutadienes
Authors: Kalfoglou N. K. , Williams H. Leverne
Published: April 2003

The present investigation covers the isothermal stress–strain–birefringence behavior of various polybutadienes between −30°C and 110°C. Birefringence measurements were also made under constant stress as a function of temperature in the low temperature region between −30°C and −120°C. The polybutadienes studied were two high cis‐1,4 (prepared by different catalysts), a linear medium cis, and an emulsion polybutadiene. At temperatures at which the photoelasticity theory could be applied, the segmental polarizability anisotropy, its temperature dependence, and other parameters associated with an elastic polymeric network were determined. The influence of the degree of crosslinking was examined. At the low temperatures, microstructure was shown to have a pronounced effect on the photoelastic properties, the crystallization phenomena, and the glass–rubber transitions.
Hydroxylation of polymethylsiloxane surfaces by oxidizing plasmas
Authors: Hollahan John R. , Carlson George L.
Published: April 2003

The reaction of a radiofrequency‐excited oxygen plasma with the surfaces of cured and uncured polymethylsiloxane produces intense hydroxylation of the surface region as followed by FMIR spectroscopy. Characteristic infrared features indicative of intraor intermolecular hydrogen bonding are evident. Plasma oxidation differs markedly from thermal oxidation processes. Reactions of polymethylsiloxane with nitrogen and air plasmas were also investigated and compared to corona reactions of oxygen, nitrogen, and air. In air corona, nitrogen moieties appear to be introduced. The behavior of polymethylsiloxane surfaces in oxidizing acids is also described.
The introduction of elastomeric behavior into polycarboranylenesiloxane SiB‐1 polymers from the closo‐carborane C2B5H7
Authors: Kesting R. E. , Jackson K. F. , Klusmann E. B. , Gerhart F. J.
Published: April 2003

The copolymerization of a small amount of the larger (C2B8 and C2B10) carboranes with the smaller C2B5 carborane resulted in the formation of an elastomeric SiB‐1 carboranesiloxane, a polymer hitherto prepared only in crystalline form. Although the elastomeric behavior of the uncured SiB‐1 copolymer decreased with time, curing stabilized the rubber by inhibiting crystallization.
Development and performance of some porous cellulose acetate membranes for reverse osmosis desalination
Authors: Kunst B. , Sourirajan S.
Published: April 2003

The effects of casting solution composition and evaporation period on the performance of resulting porous cellulose acetate membranes have been studied, and the results are discussed in terms of casting solution structure, solvent evaporation rate during film formation, and the film shrinkage temperature profile. The development of Batch 316‐type porous cellulose acetate membranes is reported. At 90% level of solute separation and feed flow conditions corresponding to a mass transfer coefficient of 45 × 10−4 cm/sec, the productivities of the above membranes are 21.5 gallons/day/ft2 at 250 psig using 3500 ppm of NaCl in the feed, and 53.9 gallons/day/ft2 at 600 psig using 5000 ppm of NaCl in the feed.
Sorption of poly(vinyl acetate) on cellulose. II. The role of the porous structure
Authors: Alince B. , Robertson A. A.
Published: April 2003

The adsorption of poly(vinyl acetate) from benzene solution onto cellulosic materials having various porous structures was measured in an attempt to investigate the role of the pore size distribution in the sorption process. The variety of cellulose porous structures was obtained by combinations of different swelling agents—water, ethylenediamine, sodium hydroxide solution—with different subsequent drying treatments. The pore structure analysis was based on benzene desorption isotherms. The porosity of cellulose is responsible for selective adsorption of the smaller macromolecules from an unfractionated polymer solution. The amount of sorbed polymer increases when the polymer solution contains a greater fraction of lower molecular weight polymer. Only the pores above a certain size are accessible to the polymer. The amount of polymer sorbed is proportional to the area of such pores but is otherwise independent of the effects produced by swelling pretreatments.
Graft copolymerization onto cellulose by ceric ion initiator system: Effects of kind of acid and irradiation with ultraviolet light
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

The effects of kind of acid and irradiation of ultraviolet light on the graft copolymerization of methyl methacrylate onto cellulose with adsorbed ceric ion were investigated. Irrespective of ultraviolet light irradiation, the amount of reduced ceric ion in the reaction systems was increased in the order HCl > HClO4 > HNO3 > H2SO4, and the number of grafts formed was increased in the order HClO4 > HNO3 > HCl > H2SO4. Thus, it was definitely observed that the graft copolymerization is affected by the kind of acid. Ultraviolet light remarkably accelerated the reduction of ceric ion adsorbed on cellulose in the various acid mediums, but decreased the efficiency of graft formation. The most favorable results for the formation of grafts were obtained in the system in which HClO4 and ultraviolet irradiation was employed. A combination of H2SO4 and ultraviolet irradiation resulted in the lowest per cent grafting and average molecular weight of grafts. It was found that H2SO4 characteristically dissolves out ceric ion adsorbed into an aqueous solution and accelerates the formation of homopolymer.
Structural changes in glassy polymers
Authors: Ali M. S. , Sheldon R. P.
Published: April 2003

It has previously been shown that glassy poly(ethylene terephthalate) gives rise to endothermal peaks in DTA when annealed at temperatures near to the glass temperature. The present work describes results obtained from DTA and DSC on annealing a number of glassy polymers which have been rapidly cooled from above the glass temperature and on slowly cooled samples of the same polymers. The polymers which have been studied are: poly(ethylene terephthalate), poly(methyl methacrylate), atactic and isotactic polystyrene, bisphenol‐A polycarbonate, poly(ethyl methacrylate) and poly(vinyl acetate). In every case, evidence of structural reorganization is observed, and the rate at which this takes place is reported. Separate studies on poly(ethylene terephthalate) reflect density changes which also take place upon annealing. These results are discussed in the context of the calorimetric observations.
Activity measurements of bivalent cations singly and in mixture with resin membrane electrodes in aquo‐organic media
Authors: Adhikari M. , Pal M.
Published: April 2003

Cation exchange resin membranes were used as electrodes for activity measurements in aquo‐propanolic media for bivalent ions, e.g., Ca, Mg, Cu, Zn, either singly or in a mixture of two. From the results it may be concluded that ion exchange resin membranes can be satisfactorily utilized for measurement of these ion in such media when present singly or in a mixture.
Multiple steady states, viscosity, and high conversion in continuous free‐radical polymerization
Authors: Knorr R. S. , O'Driscoll K. F.
Published: April 2003

Using existing literature data on the rate of a bulk polymerization of styrene in a batch reaction carried to high conversion, it is mathematically demonstrated that there is a clear possibility of the existence of multiple steady states induced by viscosity effects in isothermal continuous stirred tank reactors. In solutions of high viscosity, the rate of free‐radical polymerization increases with conversion, reaching a peak at very high viscosity, then falling off rapidly. Given this sort of behavior, it is demonstrated mathematically that steady‐state mass balance solutions are possible at three levels of conversion. The lower and higher steady states are stable while the middle steady‐state condition is shown to be necessarily unstable. This multiplicity of steady states with its particular problems of stability is analogous to the much studied phenomena of temperature stability. It is closely related to the problems of concentration stability characteristic of autocatalytic and heterogeneous catalytic reactions. This multiple steady‐state problem is qualitatively discussed in relation to reactor stability, control, and optimization.
Theoretical analysis and critique of the chromatographic separation of macromolecules using porous adsorbents
Authors: White James L. , Kingry Gary W.
Published: April 2003

A theoretical analysis of the separation of a mixture of macromolecules by a chromatographic column packed with porous adsorbents is given. Fractionation may take place by either exclusion of large molecules from the pores in the column packing or by selective adsorption. A model for packing structure is developed which is used as the basis of a theory of chromatographic separation.
The permeation of gases through modified polymer films. II. Gas permeability and separation characteristics of gamma ray‐irradiated polyethylene
Authors: Kanitz Peter J. F. , Huang Robert Y. M.
Published: April 2003

A study has been made of the diffusion, solubility, and separation of nitrogen and methane gases in a series of air‐and vacuum‐irradiated polyethylene films in the temperature range of 15° to 50°C. Samples were air irradiated to 90 Mrads and vacuum irradiated to 80 Mrads. The major structural differences between the modified films were the presence of oxygenated species in the air‐irradiated samples. The oxidation of these samples reduced the amount of crosslinking normally found in vacuum‐irradiated samples. Diffusion and permeability coefficients for both gases decreased with irradiation dose. The solubility coefficients for the air‐irradiated samples increased with increasing irradiation dose while little change was observed for vacuum‐irradiated film. The gas mixture permeabilities could be predicted from the pure component permeabilities, and the methane–nitrogen separation factor decreased with increasing irradiation dose.
The dynamic viscosity of polypropylene melt
Authors: Dunlop A. N. , Williams H. Leverne
Published: April 2003

The dynamic viscosity of polypropylene melt was determined as a function of frequency and temperature. The temperature‐shift Arrhenius energy was calculated in several ways. The influence of temperature on the elastic and viscous components was quantitatively discussed.
The reaction of chlorinated polyethylenes and amines
Authors: Kriston P. , Kocskina A. , Dimitrov M.
Published: April 2003

The reaction of chlorinated polyethylene and amines, the chemical changes accompanying the heat treatment of the aminated product, and the changes of some practically important properties of the resulting product have been studied. It was found that during amination nitrogen is incorporated in the macromolecules; during the applied heat treatment this nitrogen is eliminated from the polymer and the product becomes practically insoluble. The anticorrosive properties of the resulting product are significantly better than those of chlorinated polyethylene, and this is a very important result from the practical point of view.
An environmental instrument for measuring creep and stress relaxation in polymers
Authors: Machin D. , Rogers C. E.
Published: April 2003

The construction and operation of an instrument for measuring tensile stress relaxation and creep, particularly of polymers, is described. The instrument is comparatively inexpensive to build and enables measurements to be carried out in vacuo or in a controlled atmosphere of gas or vapor. The design is based on principles used for some earlier stress relaxometers modified to enable characterization of samples having a very wide range of moduli either as stress relaxation or, additionally, as creep measurements. The instrument can therefore be used to evaluate material properties of hard plastics or of soft rubbers when exposed to selected environments.
Isobaric measurement of gas permeability of polymers
Authors: Yasuda H. , Rosengren Kj.
Published: April 2003

The principles and design of a gas permeability measuring instrument based on thermal conductivity measurement are described. Since the thermal conductivity of a gas mixture is dependent upon the partial pressure fraction rather than absolute partial pressure of sample gas, and the permeation rate of reference and sample gases through polymer films differe considerably, a pressure‐equalizing device is necessary for the accurate measurement of gas permeability. The three types of measurements—integral, differential (flow method), and decay rate measurements—can be used with the instrument. The results of permeability constants and diffusion constants obtained with the methods showed good agreement with the conventional vacuum‐type method. With proper selection of methods, the instrument can measure the gas flux through the range of 10−10 to 10−3 cm3 (STP)/cm2 sec cm Hg. Some advantages of the methods are discussed.
Crazing and the stress dependence of creep in two glassy polymers: Polystyrene and a poly(styrene–acrylonitrile) copolymer
Authors: Moore R. S. , Gieniewski C.
Published: April 2003

The stress dependences of crazing and of tensile creep were studied at 30.5° and 80°C in polystyrene (Mv = 2.7×105) and in a poly(styrene–acrylonitrile) copolymer (73.5% styrene, Mv = 2.35×105) at four stresses in the interval from 0.6 to 1.5×108 dynes/cm2. Material failure was observed in all cases for the polystyrene and in no cases for the copolymer. Crazing was found to occur at all stresses for polystyrene, the spacing between craze lines decreasing with increasing stress and temperature. A much higher stress level for the onset of crazing was found for the copolymer. An inverse stress dependence of the compliance was observed for polystyrene at 30.5°C, i.e., the compliance decreased with increasing stress. This behavior was partially reversed at 80°C below 102 sec and became a positive stress dependence at long times. The stress dependence of the compliance for the SAN copolymer was partially reversed at 30.5°C. At 80°C, the stress dependence was positive for stresses ≥0.9×108 dynes/cm2. The present results suggest that in the copolymer there may exist an enhanced local mobility which alters the stress dependence observed in pure polystyrene and which enhances the ability of the material to deform without failure. This concept is discussed further in light of the stress dependence of the compliance and of crazing in these materials and appears to be consistent with our previous studies of the stress dependence of creep and of the stress dependence of whitening in ABS systems.
Physical and fine structure properties of cotton fibers swollen with trimethylbenzylammonium hydroxide
Authors: Betrabet Shridhar M. , Muller Linda L. , Tripp Verne W. , Rollins Mary L.
Published: April 2003

Cotton fiber was treated with aqueous trimethylbenzylammonium hydroxide (Triton B) at concentrations over the range 25%–40%. After complete removal of the swelling agent, the samples were evaluated for the extent of swelling, strength and elongation, birefringence, moisture regain, density, crystallinity, x‐ray diffraction patterns, and microfibrillar morphology. Electron‐microscopical examination and other evaluation of fine structure properties revealed that the nature of swelling is intercrystalline up to 30% concentration of Triton B, and intracrystalline beyond that. Although the swelling as measured by propanol‐2 retention after treatment with 30% Triton B is about twice as much as that of the control, the original structure remains almost unchanged except for some gain in strength and elongation and increase in moisture regain. At 32% Triton B concentration and beyond, rapid decrystallization takes place, accompanied by a fall in birefringence, density, and crystallinity index. X‐Ray analysis showed significant loss of lateral order and partial conversion of cellulose I to cellulose II at 35% and 40% Triton B concentrations. The results indicate that, used at the critical concentration of 30%, Triton B can be a useful swelling agent for cotton fibers as it opens up the fine structure of cellulose considerably without impairing any important physical properties.
A one‐point intrinsic viscosity method for polyethylene and polypropylene
Authors: Elliott J. H. , Horowitz K. H. , Hoodock T.
Published: April 2003

A statistical analysis of dilute solution viscosity data for a wide range of polyethylene and polypropylene samples in Decalin at 135°C has shown that the Martin equation

fits the experimental data better than the Huggins equation

at higher values of [η]c. A grand average k of 0.139 is applicable to both polymers. Based upon this, tables have been calculated permitting the ready determination of [η] from a single relative viscosity measurement at a known concentration. The Martin equation has been put into a universal form, permitting [η] to be calculated from a measured ηsp if k and c are known. Graphs relating ηsp to [η] are included for use of the Martin equation over wide ranges of both k and c. It was found that the Solomon and Ciuta equation

fits the experimental polyethylene and polypropylene data, and the reasons for this are discussed.
The synthesis and characterization of monomeric etherified methylolated melamines using gel permeation chromatography and proton magnetic resonance spectroscopy
Authors: Anderson Dennis G. , Netzel Daniel A. , Tessari Domenic J.
Published: April 2003

A series of monomeric etherified methylolated melamines were prepared and characterized by proton magnetic resonance spectroscopy and gel permeation chromatography. Gel permeation chromatographic analysis permits a rapid and accurate determination of the monomer and polymer content of the products. Proton magnetic resonance spectroscopy permits the qualitative identification of the etherifying alcohols and a quantitative estimation of the alkoxy groups present. The molar ratios of alcohols necessary to produce products having specific alkoxy contents are presented graphically.
The formation in wool of copolymers of butadiene with acrylonitrile and methyl acrylate by iron salt‐hydrogen peroxide initiation
Authors: McKinnon A. J.
Published: April 2003

The formation in wool of graft copolymers of butadiene with acrylonitrile and methyl acrylate has been studied, using the ferrous ion–hydrogen peroxide system as initiator and a heterogeneous liquid phase consisting of a dilute hydrogen peroxide solution and a monomer mixture. The effects of time and temperature, and the pH and concentrations of the ferrous ion and peroxide solutions, on the polymer add‐on are discussed. The dependence of the composition of the graft copolymer on that of the monomer mixture has been determined. Certain features of the kinetics of the reaction are discussed.
Computation of near‐optimal control policies for free‐radical polymerization reactors
Authors: Osakada K. , Fan L. T.
Published: April 2003

A polymer is characterized by the average degree of polymerization and the molecular weight distribution. Approximate optimization of temperature control, or catalyst feed rate control, or both are performed to attain not only the desired average degree of polymerization but also the desired molecular weight distribution. This near‐optimal policy, which is a function of time only for a batch polymerization reactor, is first expressed by a polynomial, and the coefficients of the polynomial are estimated by a pattern search technique. This coefficient's estimation method coupled with a nonlinear search technique was found to be suitable for solving this type of our optimization problem involving complex chemical kinetics.
The effect of heterogeneity on the flow behavior on high density polyethylene
Authors: Shida M. , Cancio L. V.
Published: April 2003

The effect of heterogeneity on the flow behavior of high density polyethylene (HDPE) has been studied by systematically homogenizing heterogeneous blends and observing the effect on the basic rheological parameters and on the extrudate surface appearance. Ample evidence is presented to show that heterogeneity causes substantial changes in the flow behavior although molecular parameters obtained through solution studies are unchanged. A simplified mathematical model which clearly illustrates the effects of the size of these flow units on the flow behavior is presented.
Radiation‐initiated graft copolymerization of binary monomer mixtures containing acrylonitrile with cotton cellulose
Authors: Harris James A. , Arthur Jett C.
Published: April 2003

By the use of the cobalt 60 postirradiation grafting technique, purified cotton cellulose fibers were graft‐copolymerized with binary mixtures of acrylonitrile and other monomers, including styrene, 1,3‐butylene dimethacrylate, vinylpyrrolidone, vinylidene chloride, and methyl, butyl, lauryl, glycidyl, and allyl methacrylates. The irradiated cotton fibers were immersed in solutions of the monomers at 25°C to initiate graft copolymerization. Solvents were water, methanol, dimethyl sulfoxide, and methyl ethyl ketone, alone or in several combinations. The extent of graft copolymerization and the composition of the grafted copolymer depended on the composition of the binary mixtures of monomers and on the solvent or mixtures of solvents used. For example, addition of styrene, 1,3‐butylene dimethacrylate, or vinylpyrrolidone to acrylonitrile increased the extent of graft copolymerization to a maximum value; addition of vinylidene chloride or allyl methacrylate to acrylonitrile did not greatly affect the extent of graft copolymerization; and addition of methyl or glycidyl methacrylate to acrylonitrile increased the extent of graft copolymerization without passing through a maximum value. The proportion of acrylonitrile in the grafted copolymer was generally less than that in the binary mixtures. As the reaction time was increased, the extent of graft copolymerization increased to a maximum value; however, the composition of the grafted copolymer did not change significantly. Generally, the addition of water to the solutions increased the extent of graft copolymerization. The mechanisms of these graft copolymerization reactions are discussed.
Graft copolymerization of vinyl monomers with modified cotton. II. Grafting of acrylonitrile and methyl methacrylate on acetylated cotton
Authors: Hebeish A. , Kantouch A. , El‐Rafie M. H.
Published: April 2003

Ce(IV)‐induced polymerization of acrylonitrile and methyl methacrylate with acetylated cotton having different acetyl contents was investigated. The extent of interaction between the cotton and monomer is dependent upon the acetyl content of the former as well as on the reaction conditions. Increasing the acetyl content caused a significant decrease in the graft yield. Increasing the acrylonitrile concentration was accompanied by a substantial increase in the graft yields. The same effect was found with the initiator up to a certain concentration, but beyond it there was a reversal. The rate of grafting increased by rising the temperature and follow the order 60° > 40° > 30°C. The Ce(IV) consumption during grafting is greater than that consumed during oxidation. The consumption of Ce(IV) by the cellulosic materials was favorably influenced by the concentrations of monomer and initiator, time, and temperature. Rates of grafting and Ce(IV) consumption during oxidation of acetylated cottons having different acetyl contents strongly support the postulated mechanism of grafting using the Ce(IV)–cellulose redox system. Ce(IV) oxidation had practically no effect on the acetyl groups (expressed as per cent combined acetic acid) of the modified cotton.
The thermal analysis of polymers. V. Effects of crosslinking and hard block crystallinity on the mechanical behavior of polyurethane elastomers
Authors: Miller Gerald W.
Published: April 2003

Linear expansion measurements have been used to correlated the degree of molecular ordering of a polyurethane elastomer with the increase in hard block content. The lower the value of the linear coefficient of expansion, αL, the higher the degree of molecular fit. The soft block exerts the major influence on the coefficient of expansion below its fusion temperature (45°C), and the value usually decreases as the hard block content increases. Extenstion with aromatic diols causes the αL to decreases at 100°C as the hard block content increases. Crosslinking a urethane prepolymer with triol increases the expansivity over the diol‐extended elastomer. Keeping the NCO/OH ratio in the range 0.975 to 1.06 causes the lowest coefficient of expansion. For elastomers of low crystallinity, no correlation can be made between hard block content and enthalpy.
Concept of secondary heterogeneous structure of long‐chain branched polyethylene
Authors: Fujiki Tokio
Published: April 2003

The mechanism of formation of surface roughness and extrusion swelling of the extrudate and the steady‐shear viscous flow behavior in the region of high shear rate for branched polymers were investigated using two low‐density polyethylenes and their sheared samples. These two polyethylenes varied in their degree of branching, molecular weight, and molecular weight distribution but were similar in their melt flow index. The effect of molecular parameters, especially long‐chain branching, on viscoelastic properties in the molten state was also considered. Samples of various degree of shearing level were prepared by passing them repeatedly through an extruder. Results of intrinsic viscometry, gel permeation chromatography, and infrared spectroscopy of the original and the sheared samples indicate that no appreciable variation between them takes place in the molecular parameters during the process of extrusion shearing. Both surface roughness and extrusion swelling of the extrudate diminish with increase in the extent of shear. The extrusion shearing affects the surface roughness and extrusion swelling of the extrudate as well as the capillary entrance effect more markedly for the highly branched polymers with considerably higher molecular weight than for the less branched species with bell‐type molecular weight distribution. These results demonstrate that heterogeneity becomes more conspicuous with the degree of long‐chain branching level, and therefore the role of long‐chain branching in the development of the heterogeneity is particularly important. It is suggested that the secondary heterogeneous structure arises through phase separation or from the heterogeneous formation of strongly entangled network at the branching point of the long‐chain branching in the manufacturing process of the low‐density polyethylene and that its presence causes the distinctive viscoelastic properties of long‐chain branched polymer melts.
Film formation from polymer dispersions
Authors: Bertha S. L. , Ikeda R. M.
Published: April 2003

The coalescence of a poly(vinylidene chloride/methyl acrylate/acrylic acid) latex was found to occur only above the Tg. The various theories of film formation from polymer dispersions attribute latex coalescence to three types of forces: the pressure due to the polymer–air interface, the pressure due to a polymer–water interface, and the pressure due to capillary action. Analysis of the forces indicates that none are sufficient to cause coalescence below Tg while any, or all, may cause coalescence above Tg.
Characterization of ethylene–propylene rubber and ethylene–propylene–diene rubber networks
Authors: Hassan A. M. , Ray L. N.
Published: April 2003

The stress–strain (S/S) and the swelling equilibrium behavior in a series of ethylene propylene rubber (EPR) and ethylene propylene diene monomer (EPDM) networks were investigated and the results were employed to evaluate the effects of varying the cure conditions on the crosslinking efficiency in these networks. The S/S curve of completely swollen vulcanizates is in agreement with the predictions of rubber elasticity theory, while that of dry or partially swollen vulcanizates is fully described by the Mooney‐Rivlin equation. ϰ values determined in benzene were found to vary linearly with vr (vr = equilibrium volume fraction of rubber in swollen sample). Crosslinking efficiency, moles of crosslinks produced per moles of crosslinking agent used, ranges from 3.7 in peroxide‐cured EPDM (55% wt ethylene and 2.6% unsaturation) to 0.15 in similarly cured EPR (43% ethylene). Efficiency in the latter system improves to 0.6 by addition of a coagent (sulfur) to the cure formula. Crosslinking efficiency in EPDM (55% ethylene) was found to increase in the order: peroxide‐ > resin‐ > sulfur‐cured. In the EPDM sulfur vulcanizates, changing the terpolymer in the cure formula resulted in significant changes in the crosslinking efficiency.
Cavity formation on elongation in filled elastomers
Authors: Sekhar N. , Van Der Hoff B. M. E.
Published: April 2003

Experiments were conducted on samples of crosslinked rubbers filled with poly(tetrafluoroethylene) powder or small glass beads. Volume changes on elongation were measured in a dilatometer. Slow deformation cycles showed considerable hysteresis, the volume on elongation being smaller than on contraction. There is much less hysteresis if the sample is degassed before the experiment. These observations suggest that, to a large extent, the volume of the cavities is determined by the availability of gases dissolved in the elastomer matrix. When the samples were saturated with carbon dioxide, nitrogen, and helium, it was indeed found that the degree of cavitation increased in order with the solubility of these gases.

The initial rate of cavitation is high. After about 1 min, dilatation is proportional to the logarithm of time. This rate is inversely related to the solubility of the gas present.

When a sample is subjected to a constant tensile stress under vacuum and the external pressure is suddenly brought to atmospheric, the elongation at first decreases due to compression of the cavities and then increases slowly as gas diffuses into them. Even unfilled compounds mixed mechanically contain submicroscopic holes. These enlarge on deformation thus causing dilatation. Only for samples prepared by evaporation from solution is there no pressure dependence of the apparent modulus.

It is demonstrated that the relation between the volume of vacuum cavities and the external pressure resembles that of volume and inflation pressure of a spherical hole in an infinite elastic medium.
Necking of high‐density polyethylene
Authors: Wada Yasaku , Nakayama Akira
Published: April 2003

Necking draw of high‐density polyethylene is studied at draw rates of 2.5 × 10−2 to 25 mm/min and at temperatures of −40° to 80°C. Effect of temperature and draw rate on necking stress is interpreted in terms of viscoelastic flow of amorphous phase accompanying orientation of crystallites. It is proved that reducibility of draw rate and temperature holds and that the reduction factor obeys approximately the Williams‐Landel‐Ferry equation. Necking stress at an extremely low draw rate, critical necking stress, is discussed in terms of the phase equilibrium under stress between two states before and after microfracture of crystallites. The theory, with some approximations, leads to the equation by Iida in which the critical necking stress is expressed by fusion parameters. The thermodynamic behavior of isothermal necking is discussed and a phenomenologic criterion for necking is presented.
The preparation and stability of snake cage membranes
Authors: Jerome R. , Desreux V.
Published: April 2003

Linear chains of poly(methacrylic acid) have been successfully trapped in different polymeric materices of variable degree of reticulation. The length of the linear chains and the porosity of the cages are the two fundamental parameters which control the stability of the snake cage systems. The physical character of trapping in the membranes which are described in this paper is qualitatively demonstrated. The snake cage effect seems to be a very general principle of insolubilization. By this method, systems with specific exchange or absorption characteristics may be prepared.