bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of thermal and mechanical histories on the viscoelastic behavior of drawn polyethylene
Authors: Pereña J. M. , Benavente R. , Fatou J. M. G. 
Published: April 2003

AbstractStorage and loss elasticity complex moduli E′ and E″ and temperatures at which the α relaxation takes place are studied with respect to thermal history, deformation speed, and molecular weight distribution of drawn linear polyethylene. Maximum values of E′ and E″ increase with draw ratio of the hot‐drawn samples, and the α relaxation temperatures increase by around 10°C when the polyethylene filaments are annealed at 110°C. The activation energy of the process, considered as a single one because the symmetrical shape of the maxima, increases with draw ratio, and this increase is less pronounced when the filaments are annealed. Annealing of the filaments produces a decrease in their E′ values, but this decrease is almost negligible for filaments obtained from polyethylene with a broad molecular weight distribution. The final crystallinity of the filaments drawn at room temperature and subsequently annealed is higher for the filaments obtained at lower drawing speed.
Gas diffusion in polymer solutions: A double‐cone flow technique
Authors: Mashelkar R. A. , Soylu M. 
Published: April 2003

AbstractA new double‐cone flow technique for an experimental investigation of gas diffusion in polymer solutions is described. A theoretical development of the pertinent convective diffusion problem for the flow of a non‐Newtonian fluid over the double cone is presented. Experimental investigation of diffusion of carbon dioxide in aqueous solutions of certain polymers was carried out. The diffusion coefficient deduced from this work shows a marginal enhancement over its value in pure solvent. Possible mechanistic explanations for this phenomenon are explored.
Synthesis of transparent fluorocarbon elastomers: Effect of crosslinker type and electron beam irradiation level on physical and mechanical behavior
Authors: Kaiser R. J. , Miller G. A. , Thomas D. A. , Sperling L. H. 
Published: April 2003

AbstractSaturated fluorocarbon elastomers are very resistant to chemical reactions, including those of a crosslinking nature. In order to study proper methods of preparing these materials, Viton GLT was mixed with various levels of trimethylol propane trimethacrylate, TMPTM, and triallyl isocyanurate, Diak #7. After molding, the materials were subjected to electron beam irradiation. The glass transition, rubbery modulus, viscoelastic behavior, and equilibrium swelling were used to characterize the materials as a function of crosslinker and irradiation level. In general, the modulus and gel fraction increased with both crosslinker content and irradiation level. Mixtures of both crosslinking monomers produced an unexpected synergism, yielding higher tensile strength, and earlier onset of gelation.
Evaluation of the types of emission systems observed in aqueous media with controlled‐release formulations
Authors: Sherman Larry R. 
Published: April 2003

AbstractThree types of release systems have been observed for controlled release formulations (CRF) of biocides in aqueous media. A type I system, which is concentration dependent, can be divided into a IA system whose concentration maximum is dependent upon sample size and degradation, and a IB system whose concentration is dependent upon the solubility of the biocide in the solvent. A type II system, which is time dependent, can be divided into a IIA system whose release rate is dependent upon t1/2 and a IIB system whose emission is zero order or dependent only upon time. A type III system, which is a failure system, can be divided into a IIIA system whose concentration decreases to a nondetectable range as a function of t1/2 and a IIIB system whose decreasing concentration is first order. Equations relating the theoretical life of the CRF to its bioactive life are also presented.
Graft copolymerization of vinyl monomers on cellulose using peroxyacetic acid–ferrous ion redox initiator system
Authors: Hirose Shigeo , Hatakeyama Hyoe 
Published: April 2003

AbstractGraft copolymerization of vinyl monomers such as methacrylate, acrylamide, and acrylic acid on cellulose using the peroxyacetic acid–ferrous ion redox initiator system was studied. Filter paper was chosen as cellulosic material. The effect of the experimental conditions on grafting ratio, grafting efficiency, total conersion and number of branches, and other factors was studied by varying the concentration ratio of peroxyacetic acid to ferrous salt, reaction time, reaction temperature, the addition of disodium ethylenediaminetetraacetate (EDTA), pH, and so on. It was found that there is an optimum range of initiator concentration, that at a higher temperature the copolymerization proceeds more rapidly and more efficiently, and that the addition of EDTA enables the copolymerization to proceed at a higher pH.
Effect of reactant ratio and temperature on the characteristics of phenol–formaldehyde foams
Authors: Singh Daljit , Ohri Suneeta 
Published: April 2003

AbstractThis study presents experimental results on the preparation and characteristics of high‐density phenol–formaldehyde foams and compares their characteristics with the available patent literature. An extrapolation of the data has been used to identify the relevant process parameters used for the preparation of lower‐density foams. The effect of catalyst combination and phenol formaldehyde molar ratio on the ease of foaming and its ultimate strength has been investigated. A total solids refractive index correlation has been developed for following the reaction. The effect of foaming temperature on the density and strength of the foam was also studied.
Use of a dynamic mechanical analyzer to study supported polymers
Authors: Starkweather Howard W. , Giri Mylar R. 
Published: April 2003

AbstractThe real and imaginary parts of the complex modulus of polymers which must be supported can be determined with the Du Pont Dynamic Mechanical Analyzer. Polymer coatings of equal thickness are laminated on both sides of a thin metal sheet. The flexural modulus of the laminate is given by E = E1X3 + E2(1 − x3) where E1 and E2 are the moduli of the metal and the polymer, respectively, and x is the thickness fraction of metal. Under some conditions, the dynamic viscosity of the polymer can also be determined.
Behavior of cellulose graft copolymer towards persulphate oxidation. III. Poly(acrylonitrile) graft copolymers
Authors: Khalil M. I. , Aglan O. I. , Hebeish A. 
Published: April 2003

AbstractCotton cellulose was graft copolymerized with poly(acrylonitrile) to different levels. The copolymers so obtained together with the nongrafted cellulose were oxidized at different pH's (4–10) and temperatures (50–70°C) with potassium persulphate. The oxidation reaction was studied with respect to oxygen consumption, mass loss, and changes in copper number and carboxyl content of the cellulosic materials. It was found that the rates of oxidation at pH 4 for the copolymers are substantially higher than that of the nongrafted cellulose and the rate of oxidation is higher the higher the level of grafting. The reverse is the case at pH 10. The mass loss increases as the oxygen consumption increases irrespective of the substrate used and the pH employed. The magnitude of the mass loss is substantially lower in the case of grafted cellulose than in the case of nongrafted cellulose. The cellulosic copolymers with higher graft levels show lower mass loss than those having lower graft levels. However, the copper number and carboxyl content of the oxidized grafted cellulose are higher than those of the nongrafted cellulose at the same oxygen consumption. It is believed that the presence of poly(acrylonitrile) graft in the molecular structure of cellulose impedes cellulosic chain scission without necessarily preventing oxidation of cellulose hydroxyls.
Grafting onto wool. XVI. Graft copolymerization of vinyl monomers by use of TBHP–FAS as redox initiator
Authors: Misra B. N. , Sood D. S. 
Published: April 2003

AbstractMethyl acrylate (MA), methyl methacrylate (MMA), and n‐butyl vinyl ether (n‐BVE) have been graft‐copolymerized onto Himachali wool in an aqueous medium by using tertiary butyl hydroperoxide ferrous ammonium sulfate (TBHP‐FAS) redox system at 40°C, 50°C, 60°C, and 70°C for various reaction periods. Percentage of grafting and percent efficiency have been determined as functions of concentration of monomers, molar ratios of [TBHP]/[FAS], time and temperture. Molar ratios of [TBHP]/[FAS] were found to influence grafting of different monomers studied. Chemical evidence indicates that a covalent bond formation occurs between grafted polymeric chain and backbone polymer. The rate of grafting (Rp) and induction period (Ip) of different monomers towards graft copolymerization were determined as function of total initial monomer concentrations. Rp and Ip of n‐BVE are independent of total initial monomer concentrations while Rp and Ip of both MA and MMA were found to depend on the total initial monomer concentrations. MA, MMA, and n‐BVE were found to differ in reactivity towards grafting onto wool in the presence of (TBHP‐FAS) redox system; the following reactivity order was observed: MMA > MA > n‐BVE.
Interlaminar shear properties of some glass‐fiber‐reinforced phenolic and polyester laminates
Authors: Kaminski A. 
Published: April 2003

AbstractChopped strand mat and glass‐fabric‐reinforced thin and thick laminates were made from phenolic and polyester laminating resins using three modifications of a hand lay‐up method. Short‐beam interlaminar shear strengths were determined in three‐point bending at a span‐to‐depth ratio 3:1. Plane and perpendicular specimens were used. It was found that the perpendicular specimens were more useful. Interlaminar delamination energies were determined statically and dynamically. It was found that the results for the phenolic and polyester laminates cannot be simply compared because of differences in the fracture mechanism.
Comparison of dynamic and static degradation of poly(vinyl chloride)
Authors: Pukánszky Béla , Nagy Tibor T. , Kelen Tibor , Tüdõs Ferenc 
Published: April 2003

AbstractThe thermal degradation of PVC was measured under dynamic and static conditions. The UV and IR spectra, as well as the molecular weight distribution of the PVC samples, taken after different time intervals were measured. It was established that during the dynamic PVC degradation, performed in a mixing chamber, two stages with different degradation rates can be distinguished both in extinction and torque vs. time curves. While oxygen does not, dissolved HCl does play an important role in the dynamic degradation: HCl steps into reaction with the formed polyenes and has a catalytic action. The chemical degradation, particularly the crosslinking, produces the changes in the rheological behavior of the material. Results were compared with those obtained under static conditions in argon, air, and HCl atmosphere.
Physical properties of oriented poly(butylene terephthalate)
Authors: Leung W. P. , Choy C. L. 
Published: April 2003

AbstractThe effect of orientation on the low‐strain mechanical properties, dielectric relaxation, and thermal expansivity of poly(butylene terephthalate) has been studied. The α relaxation at 50°C (1 Hz), which involves large‐scale chain motion in the amorphous regions, is reduced in magnitude and shifted to higher temperature after drawing. In contrast, the localized motions of the carbonyl and glycol groups associated with the β process at −90°C (1 Hz) is not much affected by orientation. At low temperature, a large difference along and normal to the draw direction is observed for both Young's modulus and thermal expansivity. The anisotropy, however, diminishes with increasing temperature and becomes nearly zero above the α relaxation. This feature can be understood on the basis of the Takayanagi model.
Sorption of diethyl phthalate by nitrocellulose fibers
Authors: Lewis T. J. , Roberts G. M. 
Published: April 2003

AbstractThe manner in which diethyl phthalate (DEP) is absorbed into nitrocellulose (NC) fibers has been observed microscopically. The movement of pure DEP into dry fibers proceeds by capillary motion up the central canal (lumen) and through microcracks between fibrils. Attack, measured by a large change in birefringence, spreads from these foci, and within the time scale of the experiment there is little interaction with the primary (outer) wall of the fiber. If, however, the lumen and other capillary passages are blocked by water or other liquid, then attack proceeds evenly from the outer wall and a sharp boundary between swollen and unswollen material moves at a uniform speed towards the center of the fiber and appears to be unaffected by the fibrillar structure (Case II swelling). If the supply of DEP to the surface is interrupted, this boundary becomes immobile, and the concentration of DEP in the swollen layer is that which is just sufficient to saturate residual un‐nitrated hydroxyl groups on the NC. Reducing the activity of the DEP by admixture with benzene results in similar sharp boundaries, presumably because capillaries become blocked with spent diluent. Apart from capillary action, movement is always perpendicular to the fiber axis.
Formation of cracks on photodegraded nylon 6 filaments
Authors: Fujiwara Y. , Zeronian S. H. 
Published: April 2003

AbstractCracks were found on the surface of drawn nylon 6 filaments irradiated with ultraviolet (UV) light from a mercury lamp under various humidities at room temperature. The cracks were formed perpendicular to the fiber axis and were of varying sizes. No cracks were observed on undrawn filaments or drawn filaments exposed to UV light in a dry atmosphere. Considerable shrinkage was found in drawn samples by thermomechanical analysis indicating the presence of residual stress in the material. The cracking is explained in terms of the residual stress and plasticization by moisture.
An unusual visual microcracking/healing phenomenon in polycarbonate at room temperature
Authors: Narkis M. , Bell J. P. 
Published: April 2003

AbstractPolycarbonate samples show no visible changes upon removal from boiling water. However, during a subsequent storage stage at room temperature they begin to develop visible disc‐shaped microcracks whose number and size increase with time. At a certain time during the room temperature storage period a healing process begins leading in many cases to a complete visual disappearance of the microcracks. The cracking/healing phenomenon is explained in terms of water‐supersaturated systems undergoing water phase‐separation creating water filled microcracks. These thin water filled microcracks then lose their water to the environment during drying at room temperature, close, and visually heal.
Activating pulp toward acetylation by chemical or mechanical means
Authors: Heikal Salwa O. , El‐Kalyoubi Samira F. 
Published: April 2003

AbstractActivation of pulps during acetylation, by prior mechanical or chemical treatment, has been investigated. The effect of degree of beating on the acetylation rate of wood and bagasse pulps has been studied. It is found that the acetylation rate of pulps increases when the degree of beating of pulps is increased to a definite degree, after which it slows down. The maximum reactivity of bagasse pulp is obtained at 50°SR, while that of wood pulp is observed at 30°SR. The effect of grafting of acrylonitrile onto bagasse and wood pulps on their reactivity during acetylation has been also studied. The results indicate that grafting of acrylonitrile onto pulps has a favorable effect on their acetylation rate. This is dependent on the degree of grafting as well as the origin of pulp fibers. The most suitable method of activation during acetylation reaction is dependent on the origin of the pulp. The reactivity of bagasse pulp during acetylation is influenced more by beating of pulp, prior to the reaction, than by the grafting of acrylonitrile onto pulp. On the other hand, the acetylation reaction of wood pulp is activated by grafting rather than by beating. Also the effect of the activation process, mechanical or chemical, on the strength properties of the paper sheets produced from acetylated pulps has been investigated. Chemical activation of wood pulp prior to acetylation resulted in pulp with slightly higher strength properties than that activated by mechanical means. But, in the case of bagasse pulp, mechanical activation resulted in a pulp with strength superior to that produced by chemical activation.
Process for the formation of biaxially oriented films of poly(p‐phenylene terephthalamide) from liquid crystalline solutions
Authors: Flood John E. , White James L. , Fellers John F. 
Published: April 2003

AbstractA new process for making equal biaxially oriented films from liquid crystalline solutions of poly(p‐phenylene terephthalamide) (PPD‐T) is described. The process involves extruding solutions of PPD‐T/H2SO4 through an annular die and over an oil‐coated mandrel into a coagulation bath. The films were studied using wide angle X‐ray diffraction (WAXS) and scanning electron microscopy (SEM). Tensile stress–strain properties were obtained on samples cut at various directions in the plane of the film. Biaxially oriented films which possess equal properties in the various directions in the plane of the film were produced. Moduli of 2.3 × 109 Pa and tensile strengths of 9.6 × 107 Pa were obtained in the plane of the film. Films with unequal biaxial orientation were also produced. These tend to have higher modulus/tensile strength in the direction of major orientation, the machine direction (up to 8.3 × 109 Pa/2.5 × 108 Pa), but become brittle in the transverse direction.
Vapor–liquid equilibria for benzene/polybutadiene and cyclohexane/polybutadiene systems at 333, 355, and 373 K using gas chromatography
Authors: Lau W. Robbie , Glover Charles J. , Holste James C. 
Published: April 2003

AbstractA perturbation chromatography apparatus has been designed and constructed for determining the vapor–liquid equilibrium between a two‐component (solvent/helium) vapor phase and a two‐component (polymer/solvent) liquid phase. The apparatus performed very well, giving reproducible and reliable results that agree with independent, previously reported studies. All tests of the equipment indicated that it was successful in meeting the conditions of low column pressure drop, small perturbations, and slow flow rate that are required for perturbation chromatography. Binary polymer/solvent data were obtained for polybutadiene (PBD)/benzene or polybutadiene/cyclohexane systems at solvent partial pressures to 40 kPa and for n‐hexane at infinite dilution, all at the three temperatures of 333.15, 355.00, and 373.15 K. The experimental data for each system can be represented within experimental error by the Flory–Huggins polymer solution theory using a single binary interaction parameter that is independent of temperature and concentration.
Rheological and solid wall boundary condition characterization of unvulcanized elastomers and their compounds
Authors: Toki Shigeyuki , White James L. 
Published: April 2003

AbstractAn extensive fundamental investigation of the rheological properties and solid wall boundary condition shear stress of elastomers and elastomer–carbon black compounds has been carried out. The elastomers were an emulsion butadiene–styrene copolymer (SBR 1500) and a polybutadiene. Shear flow rheological properties were measured using a newly designed sandwich rheometer, in both constant shear rate and creep modes as well as in a capillary rheometer. A constant elongation rate rheometer for elastomers was developed. Stress relaxation measurements were also carried out in the sandwich rheometer. The shear viscosity of the gum elastomers exhibits a constant very high shear zero viscosity (8 × 108 Pa.s for SBR 1500 at 100°C) and decreases with increasing shear rate. The compounds exhibit yield values of similar magnitude to carbon black compounds of molten plastics. Only the SBR 1500 and its compounds were studied in the elongational flow mode. It was not possible to achieve a steady state in these experiments. An apparatus for measurement of shear stress as a function of velocity (shear rate) at a specified pressure was developed. The instrument, which we call a friction tester, was used not only to determine wall shear stress but to investigate the regime of flow and potentially determine conditions for the onset of slip. Evidence of changing flow regimes were found, and the implications discussed.
Identification of two pass regimes for nylon‐66 based rods in the critical oxygen index test
Authors: Wharton R. K. 
Published: April 2003

AbstractCritical Oxygen Index (COI) values for rods of a nylon‐66 based material of various diameters have been determined at 40°C. The existence of two discrete COI values has been identified for many sizes above a critical diameter: the two indexes correspond to clean burning and to burning with melting and dripping. The difference between the two indexes is dependent on rod diameter and can be greater than five units.
Synthesis of brominated acenaphthylenes and their flame‐retardant effects on ethylene–propylene–diene terpolymer
Authors: Morita Yohsuke , Hagiwara Miyuki 
Published: April 2003

AbstractBromoacenaphthylenes and their condensates as flame‐retardant reagents were synthesized by bromination of acenaphthylene using ZnCl2CF3COOH or FeCl3 as catalysts and subsequent dehydrobromination. The chief components were identified as bromoacenaphthylene monomers when ZnCl2CF3COOH were used, and as their condensates (mostly trimers) in the case of FeCl3. Their performance as flame‐retardant reagents for ethylene–propylene–diene terpolymer (EPDM) was evaluated by measuring the oxygen index of finished compounds, and flammability by a vertical flammability test based on UL‐94‐VO. Both the monomers and the condensates demonstrated high flame‐retardant effectiveness. The high efficiency was attributed to their excellent dispersity in the base polymer and their characteristic thermal decomposition behavior. In TGA, they decomposed in a very wide range of temprature (ca.200–560°C), which covers the decomposition range of EPDM. This was attributed to the existence of bromines of different thermal stabilities in one molecule.
Prediction of sedimentation coefficients of random coil polymers
Authors: Kok C. M. , Rudin Alfred 
Published: April 2003

AbstractThe concentration dependence of the radius of gyration and the equivalent hydrodynamic radius of polymers in solution is described well by a model developed in earlier work. The calculated hydrodynamic volumes of solvated polymers are combined with the statistical mechanical calculations of Burgers for hard spheres to predict sedimentation coefficients at finite concentrations. The predicted values are in good agreement with experimental results.
Smoke suppression by ammonium polyphosphate in poly(acrylonitrile) combustion
Authors: Ballistreri Alberto , Montaudo Giorgio , Puglisi Concetto , Scamporrino Emilio , Vitalini Daniele 
Published: April 2003

AbstractThe influence of ammonium polyphosphate (APP) on the smoke emission of poly(acrylonitrile) (PAN) has been examined, and its mechanism of action as a smoke suppressant agent has been investigated. Smoke density and corresponding residual char data, as a function of temperature, were obtained in order to characterize the smoke propensity of PAN. The amount of generated smoke, both in smoldering and flaming conditions, was considerably lowered by the presence of APP, and higher char yields were obtained. Beside the smoke suppression, flame inhibition effect of APP on PAN was evidenced. Thermogravimetry (TG), oxygen index (OI), and nitrous oxide index (NOI) experiments were also performed. On the basis of our data, APP appears to act as a char‐forming agent in PAN combustion. Both smoke suppression and flame inhibition effects can be considered a consequence of this action.