bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroplating on crystalline polypropylene. I. Compression molding and adhesion
Authors: Fitchmun D. R. , Newman S. , Wiggle R. 
Published: April 2003

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractIt 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

AbstractCation 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

AbstractUsing 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

AbstractA 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

AbstractA 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 reaction of chlorinated polyethylenes and amines
Authors: Kriston P. , Kocskina A. , Dimitrov M. 
Published: April 2003

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractCotton 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractBy 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.