bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal analysis of styrene–alkyl methacrylate polymers. I. Glass transition temperatures
Authors: Lin Jacob W. , Wen Walter Y.
Published: April 2003

The glass transition temperatures (Tg's) of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers were measured using thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). The polymers studied had number‐average molecular weights from 3000 to 250,000 g/mole. The results indicate that the composition dependence of the Tg's for the copolymers and terpolymers can be satisfactorily described by a general Fox equation. In general, the measured Tg's of the copolymer and terpolymer samples depend more on the steric effects of the constituent pendent groups than on their molecular weights. The chain flexibility rather than the size of the pendent group is the determining factor in the glass transition properties of the styrene polymers.
Thermal analysis of styrene–alkyl methacrylate polymers. II. Thermogravimetric kinetics
Authors: Wen Walter Y. , Lin Jacob W.
Published: April 2003

The thermal stability and degradation kinetics of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers with a number‐average molecular weight (M̄n) of 6000–250,000 g/mole have been studied using dynamic thermogravimetry (TG). The degradation kinetics of each polymer sample have been successfully attributed to a sample first‐order reaction expression. The results indicate that the thermal stability and degradation kinetics of the polymers are independent of the size of the molecules within the molecular weight range investigated. The steric hindrance effects of the pendent groups appear to be responsible for the improved thermal stability and resistance of CC bond scission in the styrene–alkyl methacrylate copolymers and terpolymers.
Wetting behavior of human hair fibers
Authors: Kamath Y. K. , Dansizer C. J. , Weigmann H.‐D.
Published: April 2003

The wetting behavior of human hair in water has been investigated using a technique based on the Wilhelmy balance principle. The experimental technique makes it possible to study the relaxation effects occurring at the solid–liquid–air interface. The results strongly suggest that interactions between the solid and the liquid make important contributions to wettability of the solid surface because of reversible reorientation of polar groups at the interface. The effects of scale structure, weathering, and mechanical damage on wettability of the fiber surface are discussed. Surface roughness of the fiber plays an important role in wetting hysteresis.
Permeation of water vapor through cellulose triacetate membranes in hollow fiber form
Authors: Pan C. Y. , Jensen C. D. , Bielech C. , Habgood H. W.
Published: April 2003

A modification of the carrier gas method for measuring permeability of a hollow fiber to a vapor is described with particular application to water vapor permeation through asymmetric cellulose triacetate in hollow fiber from. Conventional methods are inadequate because the high flux of permeation vapor combined with its low pressure on the permeate side and the small diameter of the fiber lead to an excessive buildup of pressure in the permeate stream—in some cases so great as to render much of the fiber length ineffective. The method described in this paper involves the permeation from the outside to the inside of the fiber of a binary mixture consisting of the water vapor and a fairly highly permeable carrier (helium). There is a significant pressure drop along the fiber, but a theoretical treatment is presented to take this into account and to permit a determination of the vapor permeability. Experiments at 35°C over a range of water vapor pressures up to 1.7 cm Hg gave a water flux of 9 × 10−3 cc(S.T.P.)/cm2‐sec‐cm Hg, with an apparent slight decrease with increasing pressure. Over the same range of water vapor pressure the helium flux decreased from 2.3 × 10−4 to 1.85 × 10−4 cc(S.T.P.)/cm2‐sec‐cm Hg.
X‐ray diffraction orientation studies on blown polyethylene films. II. Measurements on films from a commercial blowing unit
Authors: Maddams W. F. , Preedy J. E.
Published: April 2003

X‐Ray diffraction pole figure measurements have been made on a series of films, blown under various conditions from three high‐density polyethylenes. The results are interpreted in terms of two distinct types of orientation. The first, and probably the more normal, is the result of the type of stress crystallization process described by Keller and Machin and has the a and c axes inclined at an angle to the plane of the film. The second type of orientation is crystallographically analogous to that found in cold drawn polyethylene in having the c‐axis distribution substantially along the machine direction. This is termed high‐stress orientation. The type of orientation obtained is dependent both on the blowing conditions and the particular polyethylene. With an experimental Rigidex grade and with Shell LPPE 040 there are always substantially amounts of the conventional low‐stress orientation although certain combinations of machine conditions predispose towards the high‐stress form. This latter type forms readily in the case of Hostalen GM 9955F over a rather wide range of machine conditions and appears to be favored by slower cooling conditions.
Dielectric relaxation in epoxy‐polyglycol elastomers
Authors: Gilbert A. S. , Pethrick R. A.
Published: April 2003

Dielectric relaxation data is reported on a series of elastomers formed between bisphenol A and either polyethylene glycol or polypropylene glycol. The observed dispersion may be ascribed to relaxation of the “soft” block and is found to vary with both change in the glycol block length and with the ratio of bisphenol A to polyglycol. Elastomers prepared with a poly‐glycol component of mixed composition allowed the relaxation frequency at a particular temperature to be shifted over a frequency range of almost three decades. Activation parameters obtained from the temperature dependence of the mean relaxation frequency are used in evaluation of the factors influencing the molecular motion of the “soft” block.
Preparation and stress‐strain properties of aba block copolymers of α‐methylstyrene and butadiene
Authors: Cunningham Robert E.
Published: April 2003

ABA‐type “tapered” block copolymers of α‐methylstyrene (monomer A) and butadiene were prepared using four commercially available dilithio initiators. Polymerizations were run at 25°C in benzene solvent, or at 40°C with butadiene dissolved in neat α‐methylstyrene. Although α‐methylstyrene has a rather low ceiling temperature, triblock copolymers could be made at these temperatures by using α‐methylstyrene concentrations well in excess of the [M]evalues at the respective temperatures. Its concentration was such that molecular weights of at least 15,000–20,000 for the A blocks could be attained. The course of the copolymerization at 40°C was followed, showing that copolymers containing about 40% α‐methylstyrene could be formed in 4–8 hr, depending on the initiator used. They showed the usual behavior of triblock thermoplastic elastomers, with tensile strengths > 3000 lb/in.2at 24°C. However, because of the highTgof poly(α‐methylstyrene) (172°C), they also had tensiles of several hundred lb/in.2at 100°C, unlike comparable polymers with polystyrene end blocks, which have practically no strength at this temperature. Microstructures of polybutadienes made with these initiators are also given.
Expansion of aromatic heterocyclic polymers in salt solution
Authors: Hanley Thomas R. , Helminiak Thaddeus E. , Benner Charles L.
Published: April 2003

The addition of lithium chloride to solutions of poly(5,5′‐bibenzimidazole‐2,2′‐diyl‐1,3‐phenylene) (PBI) and N,N‐dimethylacetamide (DMAC) resulted in the elongation of the PBI molecule in solution. This elongation is due to the association of lithium and/or chloride ions in the region of the nitrogen atoms on the polymer chain. The presence of these ions expands the polymer chain by means of electrostatic repulsion. This effect was reflected in the results of the conductivity and viscosity studies. In general, LiCl can be used for both increased solubility and increased viscosity for this system. A ratio of 0.125 g LiCl/gram PBI was determined to be the optimum amount of LiCl to be added. This amount corresponds to mole of LiCl for every mole of PBI repeat unit. The PBI molecule was determined to have entanglements in concentrated solution at every 27 or 28 molecules along the polymer chain. This length between the entanglements is very low in comparison to other polymers indicating a strongly matrixed system. The chain length between entanglements was approximately the same for both PBI‐DMAC and PBI‐LiCl solutions.
Graft copolymerization onto starch. IV. Grafting of methyl methacrylate to granular native potato starch by manganic pyrophosphate initiation
Authors: Mehrotra Rakesh , Rånby Bengt
Published: April 2003

A study has been made of graft copolymerization of methyl methacrylate onto native potato starch in aqueous slurry at 30°C. As Mn3+ concentration was increased from 0.15 X 10‐3M to 1.0 X 10‐3M, conversion of monomer to polymer and add‐on of polymer to starch increased and frequency of grafts (anhydroglucose units per grafted chain) decreased sharply. The average molecular weights of the PMMA grafts also decreased in this range. At Mn3+ concentrations from 1.0 X 10‐3M to 3.0 X 10‐3M, only minor changes in grafting parameters were observed. When the amount of starch charged per batch was increased threefold, the add‐on decreased sharply, the molecular weight increased slightly, and the conversion of MMA monomer to polymer remained almost constant. The increase in frequency of grafts (AGU/chain) was almost directly proportional to the increase in the amount of starch charged. In all cases the average molecular weights of grafts were of the order of 106 and the grafting efficiencies high, normally greater than 85%. These results were compared with those previously obtained for grafting of acrylonitrile onto starch. They were interpreted in terms of initial (Mn3+)/(AGU) ratio, total number of radicals initiating grafting, and compatibility of methyl methacrylate monomer with poly(methyl methacrylate) chains.
Relaxation properties of styrene–butadiene block copolymers. A comparative study of thermally stimulated currents and thermoluminescence
Authors: Linkens A. , Vanderschueren J.
Published: April 2003

The thermoluminescence (TL) and thermally stimulated current (TSC) curves observed in styrene—butadiene block copolymers, undoped and doped with different dyes, have been compared in order to test to what extent the thermoluminescence phenomenon can be correlated with intrinsic relaxation properties of the macromolecular chains. Generally, good agreement has been found between the two types of curves. However, the observance of a significant shifting of TL peaks as a function of the nature of the added dye shows that strict correspondence between the kinetics of the two phenomena is unlikely. Consequently, it seems actually dangerous to deduce the characteristic relaxation parameters of the polymer from TL curves.
On semicontinuous polymerization of vinyl acetate
Authors: Bataille P. , Van B. T. , Pham Q. B.
Published: April 2003

A semicontinuous emulsion process was used to polymerize vinyl acetate. The parameters studied were the rate of addition of the various ingredients. The polymerization evolution was followed as samples were taken at regular intervals. These emulsion samples were analyzed for monomer conversion, rate of polymerization as well as for the size and the size distribution of the particles. The molecular weight and molecular weight distribution were obtained by gel permeation chromatography (GPC). Our study showed that the total surface of the particles is an important factor, that the reaction mechanism follows Krackeler's and Wessling's theory, and that the Smith‐Ewart ideal case does not apply here.
Swelling and diffusion properties from elongation of two‐phase polymer membranes
Authors: Penati Amabile , Pegoraro Mario
Published: April 2003

Experimental results were presented dealing with the water permeance and diffusion rate in two‐phase membranes consisting of hydrophilic domains of polyacrylic acid chemically bound by grafting to hydrophobic matrices: these are either rigid crystalline (polypropylene) or elastomeric amorphous (EPDM). Permeance is higher in rigid matrices: this is attributed to the wide net of microfractures originated from swelling of the hydrophilic domains whose formation is only possible in the case of a rigid matrix. A calculation method was proposed, which allows the evaluation of the apparent diffusion coefficient of both water and salt, starting from dilatometric measurements of membranes contacted with water and salt water. The apparent diffusion coefficient of water in rigid membranes is of the order of 10‐8 cm2 sec‐1, whereas in elastomeric membranes it appeared about 100 times lower. The apparent diffusion coefficient of salt is of the order of 10‐12 cm2 sec‐1 for both rigid‐matrix and elastomeric membranes when previously swollen.
Studies in chemically modified celluloses. XI. Hypochlorite oxidation of cellulose in the presence of chromium oxide
Authors: Shenai V. A. , Patil A. S.
Published: April 2003

In the dyeing of mineral Khaki on cotton fabrics, which are mainly used for military uniforms in India, a mixture of Fe2O3 and Cr2O3 is deposited in the fabric. When these garments are laundered using bleaching powder solution, the chromium oxide is likely to accelerate the oxidation of cotton cellulose. This aspect has been studied by oxidizing cotton yarn with sodium hypochlorite solution in the presence of chromium oxide, varying the chromium content, the pH of the oxidizing medium, and the concentration of the oxidizing agent. The properties of these chemically modified celluloses indicate that chromium oxide does accelerate the hypochlorite oxidation of cellulose and that the maximum extent of acceleration takes place when the oxidation is carried out at pH 7. The oxidized products were further modified separately by treatment with chlorous acid and sodium borohydride, and the effects of these agents on the properties of the oxidized products were studied.
Diffusion of gases through polyurethane block polymers
Authors: McBride John S. , Massaro Thomas A. , Cooper Stuart L.
Published: April 2003

The diffusivities of simple gases through a series of polyurethane block copolymers of differing aromatic urethane content and type of soft segment were measured using a quadrapole mass spectrometer as a detecting device. Although an Arrhenius expression generally described the temperature dependence of diffusion in this system, a discontinuity was observed in the Arrhenius plots for some materials, and the discontinuity was found to be related to the onset of the glass transition in the hard domains. Increasing the hard segment content of the materials decreased the diffusivity due to the increase in the activation energy of diffusion. Increasing the soft segment length brought about a decrease in the activation energy with an increase in diffusivity. Polyster urethanes had lower activation energies for diffusion than polyether urethanes of similar hard segment composition. Finally, as the penetrant diameter was increased, a decrease in the diffusivity and an increase in the activation energy was noted.
Structure of cellulose II
Authors: Hunter Regulus E. , Dweltz Neville E.
Published: April 2003

A reduced unit cell derived from the presently accepted unit cell and a new parallel chain arrangement is proposed for cellulose II (regenerated cellulose). In the present structure, all the cellulose chains are identical and there is only one chain passing through each unit cell. The intensity data for all reflections with d spacings greater than 1.747 Å have been calculated and were found to be in good agreement with the corresponding observed x‐ray intensities. The calculated agreement factor is R = 0.50. Two intrachain hydrogen bonds parallel to the fiber axis and one interchain hydrogen bond perpendicular to the fiber axis stabilize the structure. The hydrogen bonding network is in fair agreement with infrared dichroic data, and the chain arrangement conforms to stereo‐chemical criteria. No short contacts are observed. The parallel chain is also compatible with the structure of cellotetraose and the accepted hypothesis of cellulose biosynthesis, as well as the latest parallel structure for Valonia.
Effects of density and structure on load bearing and permeability characteristics of a family of shock mitigating phenolic foams
Authors: Mendelsohn M. A. , Meier J. F. , Rudd G. E. , Rosenblatt G. B.
Published: April 2003

The effects of reaction rate and density on the properties of the phenolic foam described in the first paper were studied. Process and formulation variables were examined through altering the basic chemical composition described below, in which all parts are by weight; phenolic resin two component intermediate, 200 parts; hydrophilic surfactant, 0.25 parts; lipophilic surfactant, 0.50 parts; fluorocarbon blowing agent, 12 parts; 47.5 wt % sulfuric acid, 25 parts; and 80 wt % phosphoric acid, 15 parts. Compressive stress values at 20% deflection were utilized for comparing the effects of the studied parameters on the load bearing cabability of the foam. Pressure drop of air flowing through the foam was employed as a measure of the permeability or breathability. Permeability load bearing functions were identified as a potential means for optimizing the relationship between breathability and compression‐deflection characteristics. The overall effects of cell structure on the relationship between load bearing and density have been related in a qualitative manner.
The effects of weathering and atmospheric pollutants on cotton fabric and cotton fabric treated with selected flame retardants. II. Spectroscopic studies
Authors: Slaten B. L. , Smith B. F.
Published: April 2003

Spectroscopic studies of weathered flame retardant cotton fabrics were conducted. The weathering conditions included combined and independent exposure to xenon arc light and low concentrations of SO2, NO2, and O3 gases. Multiple internal reflectance infrared analysis of weathered Pyrovatex 3805‐treated fabric showed that the finish removed after 150 hr of weathering exposure had the same structure as the original finish. Interferometer spectra of Pyrovatex 3805 and THPOH‐NH3 finishes on the fabric indicated no significant changes in the structure for both finishes after exposure to the various weathering conditions.
Reaction variables and a proposed mechanism of open‐pore urea/formaldehyde structure formation
Authors: Salyer Ival O. , Usmani Arthur M.
Published: April 2003

Formation of open‐pore urea/formaldehyde structures from nonetherified urea/formaldehyde resins involves reaction of one or more methylol groups with other methylol or amino groups. The structure formation proceeds through particle formation and growth until all the resin is consumed. A strong acid is preferred for achieving a porous structure in urea/formaldehyde resins; weakly ionized acids produce structures with low yield. Colloidal instability is an asset in porous structure formation. An 80:20 polyethylene oxide/polypropylene oxide block copolymer of approximate molecular weight 8500 has been found to be an entropic‐type destabilizer in the formation of porous structures.
Aqueous gel permeation chromatography: The effect of solvent ionic strength
Authors: Cooper Anthony R. , Matzinger David P.
Published: April 2003

Porous glass packing materials have been used for gel permeation chromatography using an aqueous phosphate buffer. Elution volumes were determined for polystyrene sulfonates, dextrans, and small neutral and charged molecules at three different ionic strengths, viz., 0.01M, 0.1M, and 1.0M phosphate, pH 7.0. The pore diameters of the glasses studied were 75, 240, 700, and 2000 Å. Elution volumes of nonionic species were unaffected by changing the solvent ionic strength. Elution volumes of charged species were markedly affected by the ionic strength of the solvent. This was attributed to a combination of decreased polymer dimensions and decreased ionic exclusion with increasing buffer concentration. The use of low ionic strength solvents may be exploited to tailor the separating range for polyelectrolytes with porous glass packings. This is particularly useful in the low molecular weight range where the lowest pore size available is 75 Å.
The effect of low molecular weight additives on the properties of aromatic polyamide membranes
Authors: Kraus M. A. , Nemas M. , Frommer M. A.
Published: April 2003

Salts contained in aromatic polyamide solutions were found to have a considerable effect on the performance and structure of reverse osmosis membrannes cast from these solutions. As in cellulose acetate membranes, certain salts greatly increase membrane fluxes without a detrimental effect on rejection. Highly dissociated salts such as LiClO4 or Mg(ClO4)2 exert a stronger influence than the commonly used LiCl. With mixtures of different salts, stronger effects may be obtained than with a single additive. Many experimental facts indicate that the “salt effect” in aromatic polyamide membranes is due to a general effect on solvent activity and thus on the kinetics and equilibria associated with evaporation and coagulation process.
Process and fiber spinning studies for the cellulose/paraformaldehyde/dimethyl sulfoxide system
Authors: Hammer R. B. , O'Shaughnessy M. E. , Strauch E. R. , Turbak A. F.
Published: April 2003

A cellulose pulp of about 550 D.P. was readily dissolved in a combination of (CH2O)x/DMSO to afford an initial 6/6/88 cellulose/(CH2O)x/DMSO composition solution. The concentration of formaldehyde was found to be a function of solution heating time and temperature. The solutions were microscopically free of gels and undissolved cellulose fibers. Cellulosic articles such as fibers and films are easily regenerated from these cellulose solutions in the presence of coagulants such as methanol or water. Fibers with high wet modulus, intermediate tenacity, and low elongations were produced from these regenerations systems. Fibers have been spun with conditioned and wet tenacities as high as 2.9 and 2.1 g/d, respectively, with wet modulus (at 5% elongation) as high as 1.3 g/d and solubility in 6.5% NaOH in the low range of 3.0%–15%. In many respects, these fibers are comparable to those produced in the viscose process. However, the low elongations of these fibers probably would not permit normal textile processing. The cellulose/(CH2O)x/DMSO solutions were modified with compounds containing reactive NH functional groups which are known to react with excess formaldehyde to yield the corresponding N‐methylol derivatives. However, the resulting fiber physical properties were not significantly improved compared to those obtained from unmodified cellulose solutions. Addition of acrylic acid derivatives such as methyl acrylate, butyl methacrylate, or acrylonitrile to the cellulose solutions did not result in the formation of the expected 1,4‐type adducts.
Chemical transformations of polymers. XI. Mercuration of polystyrene
Authors: Štamberg J. , Petrus V. , Gregor H. P.
Published: April 2003

The mercuration of soluble polystyrene was investigated, and it was found that an addition of perchoric acid to the reaction mixture significantly accelerated the polymer transformation. The mercuration proceeds as a polymer analogous reaction, i.e., without any change in the degree of the polymerization. The mercurated product could be converted back to the original polystyrene by hydrolysis or to the corresponding bromopolystyrene by bromination. Ultracentrifuge measurements show that even at low conversion rates all macromolecules were mercurated and unreacted polystyrene could not be identified in the product. Calorimetry indicated the presence of styrene–mercuric acetate blocks in copolymers with high mercury contents.
Cationic latex interaction with pulp fibers. II. Modification of sheet properties by styrene butadiene latex with quaternized amino groups
Authors: Alince B.
Published: April 2003

Unbeaten kraft fibers covered with experimental cationic latexes were formed into sheets in which direct fiber‐fiber bonds are replaced by polymeric bonds. The effect on sheet properties—breaking length, elongation at break, folding endurance, opacity, and light scattering—was evaluated as a function of latex composition. The composition was altered by either the ratios of styrene to butadiene in the polymer or by mixing soft film‐forming and hard nonfilming latex. It is shown that, regardless of latex composition and mechanical properties of the polymeric film, all the latexes can modify the sheet properties to a similar extent, providing that the sheets are heated above the polymer's glass transition temperature. An improvement of tensile strength is accompanied by increased elongation. As a probable mechanism of reinforcement, it is suggested that the polymer acts as a filler of the fiber's surface irregularities, thus providing a larger contact area between fibers and an improved stress transfer between them.
Photolysis of poly(p‐tert‐‐butylstyrene)
Authors: Weir N. A. , Milkie T. H. , Nicholas D.
Published: April 2003

The photodegradation of thin films of poly(p‐tert‐butylstyrene) with 254‐nm radiation under high vacuum has been studied. The principal gaseous product is hydrogen, but smaller amounts (in decreasing order of yield) of methane, ethane, and isobutane are also formed, indicating that fission of bonds in the tert‐butyl group is also involved. Ultraviolet and visible spectra of degraded films indicate the presence of unsaturated groups, initial rates of formation of these being considerably higher than those for polystyrene films. Solubility data indicate that crosslinking apparently occurs less readily than in the case of polystyrene, and this is interpreted in terms of the enhanced stability (due to the +I effect of the tert‐butyl group) of the radicals formed by chain scission and also of the inhibiting steric effect of the tert‐butyl group, particularly on crosslinking reactions involving the benzene rings. Quantum yields for the gaseous products and for chain scission and crosslinking were determined, and the mechanism of the various reactions are discussed.
Thermal ignition phenomena in chain‐addition copolymerizations
Authors: Sebastian D. H. , Biesenberger J. A.
Published: April 2003

Thermal ignition theory has been extended to include free‐radical copolymerizations resulting in dimensionless criteria for runaway and ignition. These criteria were verified by computer simulation and preliminary experimentation. Approximate, but greatly simplified, material and energy balances describing nonisothermal copolymerizations were developed which are similar in form to those describing nonisothermal homopolymerizations. Regions of close agreement, as well as disagreement, between conversion and temperature histories from these approximations and those from the exact balances are described.
Environmental influence on the fracture strength of coated glass fibers
Authors: Schonhorn H.
Published: April 2003

The effect of the environment on the fracture strength of coated glass fibers is described. Simple expressions relating the thermodynamic work of adhesion, in the presence and absence of stress to the permanence of the composite, are derived. The need for interactions other than dispersion‐type interactions between silica and coating systems is emphasized. A prognosis is offered for achieving a permanently bonded structure, provided that reasonable wetting can be facilitated at the oxide–coating interface or that there is generated a strongly bound species to the silica, shifting the potential locus of failure.
Wear mechanisms for ultrahigh molecular weight polyethylene in the total hip prosthesis
Authors: Nusbaum Henry J. , Rose Robert M. , Paul Igor L. , Crugnola Aldo M. , Radin Eric L.
Published: April 2003

Ultrahigh molecular weight polyethylene is now extensively used in total joint replacements, and there is ample clinical evidence that this material wears at a significant rate in such applications. Six commercially available total hip replacements were subjected to an accurate simulation of clinical mechanical and chemical conditions, and the wear behavior of the polyethylene components was analyzed by friction coefficient measurements and scanning electron micrography of the wear surfaces. The results indicate that all of the proposed wear mechanisms excepting adhesive and abrasive wear may be eliminated. It is highly likely that abrasion fatigue and related phenomena are central to the wear process in many prostheses, but the wear process may be ultimately determined in many cases by the type of defects present in the manufactured material.
Fundamental studies on solvent dyeing with tetrachloroethylene. III. Effect of water added to the solvent dyebath on the diffusion of disperse dyes in poly(ethylene terephthalate)
Authors: Morita Zenzo , Kuchiki Kanesada , Kobayashi Ritsuko , Motomura Hiromi
Published: April 2003

The diffusion and adsorption of disperse dyes on poly(ethylene terephthalate) (PET) from the tetrachloroethylene (TCE) dyebath were investigated by the method of cylindrical film roll when water was added to the TCE dyebath. The diffusion coefficients of three disperse dyes were increased with an increase in the addition of water to the TCE dyebath, and that of C.I. Disperse Violet 8 showed a peak. The solubilities of water in TCE in the absence and presence of disperse dye were measured at 90°C by Karl Fischer titration. The solubilities in TCE were 0.040 in the absence of dye and 0.041–0.045 g H2O/100 g TCE in the presence of disperse dye. In the presence of Violet 8, the solubilities showed a peak with increasing addition of water. The effect of water addition on the diffusion coefficients was attributed to the dissolution of water in the TCE dyebath. The water dissolved in TCE brought about an additional swelling of PET swollen previously by TCE. No marked influence on the surface concentration of dye was observed by the water addition to TCE.
Prediction of dynamic and transient rheological properties of polystyrene and high‐density polyethylene melts from the molecular weight distribution
Authors: Bersted B. H.
Published: April 2003

A model relating the steady‐shear melt viscosity and elasticity to the molecular weight distribution in HDPE and polystyrene melts has been extended to predict the dynamic viscosity, modulus, and loss modulus. Limitations in the model as applied to the dynamic properties are discussed. The model is also applied to the transient response of stress growth during steady shearing. This application is considered useful because it may help describe nonsteady‐state flow of polymer melts in short dies and cyclic operations as employed in commercial molding equipment.
Purification of polymeric dyes by ultrafiltration
Authors: Cooper Anthony R. , Booth Robin G.
Published: April 2003

Ultrafiltration has been evaluated as a method for the purification of of polymeric dyes. Transport data for solvent and solutes were obtained for several polymer‐impurity mixtures and different membrane types. Relatively low molecular weight impurities were found to be significantly rejected by these membranes. A critical concentration of sodium chloride or sodium hydroxide was found to be necessary to effect efficient transport of these species. Gel permeation chromatography was used to monitor these separations and characterize the purity of the polymeric dyes produced. Impurity concentrations in the final product were typically less than 500 ppm.
Bulk polymerization of acrylonitrile. II. Model development
Authors: Garcia‐Rubio L. H. , Hamielec A. E. , MacGregor J. F.
Published: April 2003

A model for bulk polymerization of AN is developed. It adequately predicts conversion‐time histories and molecular weight development in the temperature range of 40°–80°C with AIBN as initiator. It is shown that this model has predictive powers by simulating nonisothermal conversion–time histories.
Acrylonitrile copolymer films: Influence of modification by reaction with ethylene oxide on biological degradation
Authors: Courtney J. M. , Hood R. G. , Ewart J. M.
Published: April 2003

The biological degradation of acrylonitrile–dimethylaminoethyl methacrylate and acrylonitrile–acrylic acid copolymers has been studied by evaluating copolymer films in a continuous in vitro rumen system. The copolymer films were examined before and after modification by reaction with ethylene oxide gas. The degradation of the acrylonitrile–dimethylaminoethyl methacrylate copolymer followed a pattern similar to that occurring on thermal degradation. Modification by reaction with ethylene oxide gas, which induces CN conjugation, did not improve the resistance to degradation. The acrylonitrile–acrylic acid copolymer films disintegrated, but on prior modification by reaction with ethylene oxide they remained virtually unaltered. Modification of the acrylonitrile–acrylic acid copolymer results in crosslinking with an absence of CN conjugation, leading to improved resistance to biological degradation.
Formation and behavior of mechanoradicals in pulp cellulose
Authors: Hon David N.‐S.
Published: April 2003

The mechanical degradation of pulp cellulose fiber was studied at ambient temperature and at 77°K. ESR findings reveal that mechanical degradation occurs via free‐radical routes. Three types of mechanoradicals contributing singlet, doublet, and triplet ESR signals are identified. The singlet signals are derived from the alkoxy radicals at C4positions as a consequence of the cleavage of glucosidic bonds, the radical pairs generated at C1positions contributing the doublet signals. Triplet signals are derived from the C2and C3positions due to the cleavage of C2and C3bonds. Of these radicals, alkoxy radicals are the most stable at ambient temperature. Carbon radicals are capable of interacting rapidly with oxygen molecules to produce peroxy radical intermediates, where alkoxy radicals are inert toward oxygen molecules. ESR study also reveals that cellulose mechanoradicals are capable of initiating vinyl polymerization. MMA propagating radicals are identified when the monomers are in contact with cellulose mechanoradicals. The ability of mechanoradicals to initiate graft copolymerization from cellulose fiber is discussed.
Temperature dependence of reinforcement in the composites polyurethane rubber–crosslinked polymeric filler
Authors: Kolařík J. , Hudeček S. , Lednický F. , Nicolais L.
Published: April 2003

The temperature dependence of the components of the complex tensile and shear modulus of composites thermoplastic polyurethane rubber (Estan 5707)–crosslinked polymeric filler has been determined using torsional pendulum and Rheovibron viscoelastometer techniques. For comparison, dynamic mechanical properties of the system Estan 5707–glass beads were determined. The temperature dependence of the relative modulus (modulus of composite/modulus of matrix) of the former composites exhibited a pronounced maximum at about 50°C above the glass transition temperature of the matrix. This maximum of reinforcement was discussed in terms of (a) immobilized interfacial layer, (b) broadening of the spectrum of relaxation times, and (c) increase in the glass transition temperature of the matrix. From the excess reinforcement, i.e., the discrepancy between experimental data and theoretical prediction, an apparent thickness of the immobilized layer was calculated.
Elucidation of the fine structure of poly(vinyl chloride) by hydrogenation and 13C‐NMR analysis of low molecular weight fractions
Authors: Schwenk Ulrich , Cavagna Friedrich , Lömker Franz , König Inge , Streitberger Horst
Published: April 2003

The following experiment was performed based on the assumption that the characteristic structural features of high molecular weight poly(vinyl chloride) (PVC) should be present to the same extent in its low molecular weight fractions. Two PVC fractions of molecular weight, 1500 and 800, respectively, (0.14% of total polymer) were isolated from bulk PVC (Mn 32,000) by extraction with methanol. This extract was transformed into paraffins by a new hydrogenation method using an excess of Raney nickel in order to facilitate identification. 13C‐NMR spectral data of the paraffins showed that almost 2 out of 1000 carbon atoms were linked to a side chain with more than five carbon atoms, and 5 out of 1000 carbon atoms were methyl branched. Gas chromatography‐mass spectrometry (GC–MS) analyses confirmed that the low molecular weight paraffins consisted of a sequence of even‐numbered homologs. These findings suggest indirectly that the surprisingly low degradation temperature of PVC is due to the arrangement of the chlorine atoms rather than to the branching of the alkyl chain.
Copolymers of 3,3′,4,4′‐tetraaminobiphenyl and 1,2,4,5‐tetraaminobenzene with 1,1′‐bis(glyoxalyl)‐ferrocene and 1,1′‐bis(phenylglyoxalyl)ferrocene
Authors: Vernois Michel , Williams H. Leverne
Published: April 2003

Four monomers were synthesized and four copolymers prepared. The polymers were dark‐colored, poorly soluble, crystalline products. The x‐ray photographs were typical of triclinic crystals. The polymers degraded at temperatures lower than those characteristic of the analogous homopolymers. The recovered polymers were ferromagnetic.
The measurement of dynamic flexile properties of fibers with a rheovibron viscoelastometer
Authors: Murayama Takayuki
Published: April 2003

A new method for measurement of dynamic flexile mechanical properties was developed by a modification of the Rheovibron viscoelastometer. The Rheovibron instrument is useful for obtaining dynamic tensile mechanical properties of films and fibers over a wide temperature range. A new flexile grip and procedure were used for measuring dynamic mechanical properties of material in the flexile mode using the Rheovibron instrument. The dynamic flexile properties on polyester, nylon 66, and acrylic fiber are presented.
PVC powder extrusion. Melting properties and particle morphology
Authors: Kulås Finn Ragnar , Thorshaug Niels Peter
Published: April 2003

The extrusion of unplasticized PVC powder has been studied. Powder blends with low amounts of lubricants have been used in order to observe differences between structurally different PVC powders. Experiments with varying screw speeds indicate that resins consisting of agglomerated, small, globular primary particles are more sensitive to shear and deformation in the extruder channel than more compact particles. Frictional heat seems to be dissipated inside loosely agglomerated resin particles, possibly because of a larger internal surface. This additional heat, which depends on the shear rate, influences the melting behavior considerably. Scanning electron microscopy shows that PVC particles seem to melt without first breaking into smaller particles. A comparison between bulk‐polymerized and suspension‐polymerized PVC with nearly the same particle structure reveals a close similrity in melting properties. The results obtained in this work indicate that structural differences may explain the differences in melting behavior often observed when rigid PVC blends are extruded.
Diffusivity and solubility of organic vapors in modified polyethylene films. III. Solubility studies
Authors: Aboul‐Nasr Osman T. , Huang Robert Y. M.
Published: April 2003

A dynamic absorption technique was employed to determine the solubility of benzene, hexane, and heptane in modified polyethylene films. Films were modified by solvent annealing, crosslinking, and combinations thereof. Solvent annealing was found to increase the solubility while crosslinking led to its diminution. The effect of combined treatment on the solubility was found to be dependent on the sequence of treatment, the swelling power of the conditioning agent, and the irradiation dose. A slight effect of the solvent‐diffusant pair was also observed. The solubility of the various vapors in crosslinked films was found to vary linearly with temperature. Solubility of some vapors in some of the conditioned films showed maxima with respect to temperature. The changes in solubility were explained in terms of the relative changes in the molecular volume of the diffusant and of the segmental mobility of the network chains with the various experimental conditions.
Solvent barrier property for fluorinated polyethylene
Authors: Hayes L. J. , Dixon D. D.
Published: April 2003

Solvent barrier studies for fluorinated polyethylene have shown that the fluorinated surfaces reduce the rate of permeation for many solvents. The barrier property has been related to physical and chemical properties of the solvent. For instance, solvents having a dielectric constant between 7 and 10 were not retained as well as solvents with a dielectric constant less than 7.
Partially dehydrochlorinated PVC. II. Reactions with dienophiles and hydroxylating agents
Authors: Wirsén Anders , Flodin Per
Published: April 2003

Samples of poly(vinylchloride) containing polyene sequences were made by partial dehydrochlorination by alkali in tetrahydrofuran solution, by alkali in dioxane, and thermally in dimethyl‐formamide. The reactions of polyene PVC were followed by UV spectrophotometry. Dienophiles were found to have relative reactivities similar to those found in reactions with low molecular‐weight dienes. The reaction with maleic anhydride yielded polymers which after hydrolysis contained carboxyl groups. Hydroxylation was made with osmium tetraoxide and performic acid. With the latter reagent the reaction proceeded to complete disappearance of the UV‐absorption peaks from trienes and higher polyenes: Gel permeation chromatography analysis showed that hydroxylation could be made with only minor changes in molecular‐weight distribution. The formation of gel upon thermal dehydrochlorination in DMF was shown to be due to physical cross linking probably arising by crystallization of polyene segments. The adhesion of the hydroxylated and carboxylated polymers to glass and stainless‐steel surfaces was investigated. Films adhered stronger as the degree of dehydrochlorination of the polyene PVC used to make the derivative increased. Samples with long sequences adhered much stronger than those containing short sequences of corresponding degrees of total substitution.
The manganic hydroxide–hydrazine system as an initiator of vinyl polymerization. III. The emulsion polymerization of methyl methacrylate
Authors: Rahman A. , Brown C. W.
Published: April 2003

Emulsion polymerization of methyl methacrylate with the manganic hydroxide–hydrazine system has been studied. An attempt was made to corroborate earlier evidence that the initiation may involve a surface reaction on an insoluble manganese compound. The surface area of the manganic hydroxide was varied, and the effect of this variation on the rate of decomposition of hydrazine was examined. A correlation was found between the polymerization rate and the surface area of the precipitate.
Flame‐retardant effect of tris(2,3‐dibromopropyl) phosphate on polystyrene
Authors: Inagaki Norihiro , Sakurai Shiro , Katsuura Kakuji
Published: April 2003

The flame‐retardant effect of tris(2,3‐dibromopropyl) phosphate (TBPP) on polystyrene was investigated using thermogravimetry, infrared spectroscopy, gel permeation chromatography, and electron spectroscopy for chemical analysis (ESCA). The following results and conclusions were obtained: (1) The addition of TBPP (about 3 wt%) to polystyrene had flame‐retardant properties. (2) The addition of TBPP resulted in lowering the temperature of the burning surface and the amount of volatile products. TBPP increased the thermal stability of polystyrene. (3) TBPP inhibited oxidative attack on polystyrene. In the presence of TBPP the formation of peroxide groups at the burning surface was inhibited. It is inferred that this inhibition decreases the evolution of flammable fuels from the burning surface and contributes flame‐retardant properties. There is a lesser possibility that TBPP acts as a physical barrier that limits oxygen access. At present there is no idea of why TBPP inhibits thermoxidative reactions of polystyrene.
Complexes of tetramethylthiuram disulfide with zinc dialkyldithiocarbamates and their role in the sulfur vulcanization of natural rubber
Authors: Ducháček V. , Frenkel R.
Published: April 2003

Tetramethyl thiuram disulfide, which functions as an inhibitor of the zinc dialkyldithiocarbamate‐accelerated sulfur vulcanization, has been investigated by Mooney scorch measurements at 120°C and continuous measurements in a Vuremo curometer at temperatures from 100 to 140°C. The inhibition effect is due to the formation of a complex with zinc dialkyldithiocarbamate. The stability of the complex was calculated using the Hückel method which includes charge self‐consistency on the central atom. The calculations are in a good agreement with the experimental results which illustrate that tetramethylthiuram disulfide, unlike an actual prevulcanization inhibitor, plays a significant role in all the stages of vulcanization. It decreases the crosslinking rate and increases the ultimate extent of vulcanization and its activation energy.
Deformational, swelling, and potentiometric behavior of ionized gels of 2‐hydroxyethyl methacrylate–methacrylic acid copolymers
Authors: Ilavský M. , Dušek K. , Vacík J. , Kopěek J.
Published: April 2003

The deformational, swelling, and potentiometric behavior of ionized water‐swollen gels of 2‐hydroxyethyl methacrylate (HEMA)–methacrylic acid (MA) copolymers used in biomedical and separation applications was investigated. With increasing degrees of neutralization α, the swelling degree strongly increases and the modulus Gs decreases. For the copolymers with MA content ⩾ 30 mole‐%, the dependence of Gs on α passes through a minimum. Comparison of the results with the modified theory of rubber elasticity shows that the decrease in Gs at low concentrations of charges on the chain is controlled mainly by the degree of swelling. At higher α, both the finite extensibility of network chains, caused by a high degree of swelling, and electrostatic interactions contribute to Gs. The dependence of the interaction parameter χ on the volume fraction of polymer in the gel, v2, is independent of α and closely resembles the dependence obtained for other hydrophilic polymers.
Polymerization of acrylamide compounds onto Fe plates: An alternative route for applying polymer coatings
Authors: Mengoli Giuliano , Daolio Sergio , Giulio Ugo , Folonari Carlo
Published: April 2003

Acrylamide and some of its derivatives were polymerized onto the surface of Fe plates by causing a slight corrosion of Fe to Fe2+ in the presence of perdioxy compounds. In water within a suitable pH range, the acrylamide monomers are likely to store at the metal–solution interface and to absorb on the iron surface. Thus, the polymerization takes place in situ, leading to the formation of uniform film coatings; the presence in the solution of a radical inhibitor imparts considerable stability to the bulk of the system. The dependence of the polymerization kinetics on several variables such as pH, monomer concentration, and peroxide concentration has been determined, and some characteristics of the resulting coatings were investigated.