bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mechanism of the thermal degradation of aromatic amine‐cured glycidyl ether‐type epoxide resins
Authors: Paterson‐Jones J. C. 
Published: April 2003

AbstractA mechanism is proposed for the thermal degradation of aromatic amine‐cured glycidyl ether‐type epoxide resins which is based on the results of previous work in this field. The significance of the degradation mechanism to the thermal stability of aliphatic amine‐cured epoxides and aromatic amine‐cured cycloaliphatic epoxides is discussed.
The mechanical properties of single wood pulp fibers. III. The effect of drying stress on strength
Authors: Kim C. Y. , Page D. H. , El‐Hosseiny F. , Lancaster A. P. S. 
Published: April 2003

AbstractAn experimental study has been made of the effect of drying tension on the tensile strength of single fibers from several wood species pulped in various ways. Some pulps are strengthened by drying stress, whereas others show no response. These apparently contradictory results are explained in terms of the effect of drying stress on the morphologic features responsible for strength. In part I of this series, it was shown that fiber strength is controlled by the fibril angle of the S2 layer and the extent and severity of defects. These defects are mostly the local disturbances of fibril alignment termed “dislocations”, “slip‐planes”, or “microcompressions”. It appears that drying stress strengthens fibers both by reducing the fibril angle and by aligning the fibrils in the dislocated regions. This is only possible, however, if the matrix between the fibrils can flow in shear under the applied stress. Thus, strengthening is possible for fibers of high hemicellulose content, the matrix of which flows readily in the water swollen state. Strengthening does not occur, however, for predried kraft fibers or alkali‐extracted holocellulose, for which the matrix is well bonded and insufficiently swollen.
The xanthate method of grafting. III. Effect of lignin content on the graftability of wood pulp
Authors: Hornof V. , Kokta B. V. , Valade J. L. 
Published: April 2003

AbstractSeveral commercial wood pulps of different chemical origin and with various lignin content were copolymerized with acrylonitrile using the xanthate grafting process. A number of experiments were carried out to evaluate the effects exerted by the residual lignin and by other wood components on the grafting reaction. The results obtained show that graft copolymers can be prepared in good yields with pulps containing as much as 23% lignin. With the aim to investigate the effect of lignin in more detail, two series of pulps were prepared by delignification of a crude sulfite pulp and a crude Kraft pulp to different levels of lignin content. Sodium chlorite was used as a bleaching agent. Copolymerization results obtained with these pulps indicate some fundamental differences in behavior between sulfite and Kraft pulps. In both cases, the copolymerization is afflicted by a short inhibition period whose duration, however, does not depend on the lignin content in the pulp.
The coupling of deformations in a class of viscoelastic solids to temperature changes
Authors: Rigbi Zvi 
Published: April 2003

AbstractA class of viscoelastic materials is defined by the parametric constitutive equations σ = σ(ε,t) and T = T(ε,t). It is shown that the creep rates and relaxation rates of such materials are determined by their thermal properties and the ambient temperature, and that the assumptions of constant stress of strain respectively and constant temperature are incompatible.
Morphologic changes on processing of polyblends of saturated rubber‐reinforced plastics
Authors: Koiwa Seiji 
Published: April 2003

AbstractLaminar peeling is often observed on the injection‐molded surface of the saturated rubbermodified plastics (EVASTAN), which are prepared by copolymerizing styrene and acrylonitrile in the presence of ethylene–vinylacetate copolymer (EVA). However, the delamination rarely occurs upon higher grafting and crosslinking EVASTAN with preactivated EVA, which has pendent unsaturation. The microstructure of these EVASTAN resins was observed by electron microscopy at the end of polymerization and after processing. It was found that the delamination is caused by the agglomeration and deformation of the EVA particles and is prevented by increasing the stability of the particles by grafting and crosslinking.
Protein ultrafiltration: an experimental study
Authors: Bellucci Francesco , Drioli Enrico , Scardi Vincenzo 
Published: April 2003

AbstractAn experimental study was carried out on the ultrafiltration (UF) of protein‐containing solutions under different conditions, as compared with a solution of a linear synthetic polymer. Three different fluidynamic regimes were investigated, namely, unstirred batch system, stirred batch system, and recirculating system. The results obtained substantially agree with the predictions of the gel polarization model. A significant effect of the electrolytes on the UF flux has been observed, which can be attributed to solute–solute interaction. The influence of different UF membranes has also been investigated.
Azobisisobutyronitrile‐induced vinyl graft polymerization onto nylon 66
Authors: El‐Rafie M. H. , Khalil M. I. , Hebeish A. 
Published: April 2003

AbstractThe presence of nylon 66 during polymerization of methyl methacrylate (MMA) under the influence of azobisisobutyronitrile (AIBN) produces a nylon‐PMMA graft copolymer. The copolymerization reaction is greatly influenced by the reaction medium, temperature and time of the reaction, concentration of MMA, and addition of metallic ions. Polymerization in pure organic solvents brings about little or no grafting. Incorporation of water into the polymerization system enhances grafting significantly. A reaction medium of a water/solvent mixture in a ratio of 75:25 constitutes the most favorable medium for the grafting reaction in question. Of the solvents examined, methanol, ethanol, propanol, isopropanol, and acetone work extremely well. Increase in reaction time is accompanied by an increase in the graft yield. The same holds true for the reaction temperature; the graft yield is much higher at 70 than at 50°C and follows the order 70°C > 60°C > 50°C. Increasing MMA concentration also causes considerable enhancement of the graft yield. The presence of 0.01M cupric sulfate in the polymerization system brings about an eightfold increase in the graft yield, whereas the presence of ferric sulfate at the same concentration causes a sixfold increase. The mode of initiation of grafting seems to be different in the presence of metallic ions than in their absence. A mechanism for the reactions involved in the both cases has been proposed.
The effect of skin‐core morphology on the impact fracture of poly(butyline terephthalate)
Authors: Hobbs S. Y. , Pratt C. F. 
Published: April 2003

AbstractVariations in the skin‐core morphologies of injection‐molded poly(butylene terephthalate) samples have been characterized as a function of molding conditions by optical microscopy, x‐ray diffraction, and density measurments. Samples molded from 450 and 510°F melts at mold temperatures ranging from 70 to 250°F were found to have nonspherulitic skins whose thicknesses varied inversely with processing temperature. Very little orientation was observed in the skin or core regions of the molded bars. Density profiles are presented.Impact data obtained on bars with molded‐in notches demonstrate that significant increases in impact strength are observed with increasing skin thickness, although the maximum skin thickness remains less than a few hundred microns. This behavior persists through the ductile brittle transition which is centered at ∼50°C.Fracture surface micrographs and high‐speed stress‐strain curves are presented and used to give a qualitative description of the fracture process. At room temperature the samples appear to deform elastically up to the point of fracture, while at higher temperatures extensive shear deformation is observed. In each case failure ultimately occurs via a craze–crack mechanism.
Use of solubility parameters for the preparation of hemodialysis membrances
Authors: Chawala A. S. , Chang T. M. S. 
Published: April 2003

AbstractThe Solvent mixtures of acetone and ethanol (swelling agent) were selected for the preparation of cellulose acetate dialysis membranes using the solubility parameter concept. Increased concentration of ethanol or decreased concentration of cellulose acetate in the formulation resulted in membranes with higher dialysis rate constants but with decreased tensile strengths. The membranes prepared from 20 g of cellulose acetate per 100 ml of mixed solvent of 59.9 mole‐% acetone and 40.1 mole‐% ethanol were comparable to Cuprophane membrane but were better than those prepared by using formamide as a swelling agent.
Noise and vibration damping with latex interpenetrating polymer networks
Authors: Grates J. A. , Thomas D. A. , Hickey E. C. , Sperling L. H. 
Published: April 2003

AbstractDamping systems based on interpenetrating polymer networks (IPN's) provide noise and vibration attenuation over broad temperature and frequency ranges. Semicompatible latex IPN's are employed in both extensional and constrained layer configurations. The damping behavior of IPN's of compositions poly(ethyl methacrylate)/poly(n‐butyl acrylate) [PEMA/PnBA], poly(ethyl methacrylate–co–ethyl acrylate)/poly(n‐butyl acrylate–co–ethyl acrylate) [P(EMA–co–EA)/P(nBA–co–EA)], and poly(vinyl chloride)/poly(butadiene–co–acrylonitrile) [PVC/P(B–co–AN)] were investigated and compared to both commercially available materials and to theory. The damping of both the PEMA/PnBA and the P(EMA–co–EA)/P(nBA–co–EA) IPN's in a constrained layer configuration was significantly better, over a broad temperature range of −10° to 60°C, than the commercial materials. In addition, the P(EMA–co–EA)/P(nBA–co–EA) IPN was found to be effective in damping phenolic‐impregnated Kevlar cloth laminates. A reduction of 10 dB in impact noise resulted with a 6–8% by weight layer inserted between the Kevlar‐phenolic panels. The relationship between the peak damping temperature of a constrained layer system to maximum tan δ along with that of an extensional damping system to maximum E″ was also demonstrated. Although the amount of damping predicted by the theory approached that found experimentally, sufficient differences existed such that the exact detail of the damping curve was not described.
Diffusion of stabilizers in polymers. II. 2‐hydroxy‐4‐octoxybenzophenone in polyolefins
Authors: Johnson M. , Westlake J. F. 
Published: April 2003

AbstractThe migration of radioactively labeled 2‐hydroxy‐4‐octoxybenzophenone in a number of polyolefins was investigated over the temperature range 36–75°C. The rates of diffusion in the polymers studied were found to decrease in the order low‐density polyethylene > high‐density polyethylene ∼ isotactic polypropylene, the activation energies being approximately 17, 36, and 24 kcal/mole, respectively. The results of the present study were found to be in qualitative agreement with those previously determined for the same stabilizer/polymer systems, quantitative differences being attributed to the different methods of sample preparation and the resulting differences in the morphological structures of the test specimens. The calculated solubilities of the substituted 2‐hydroxybenzophenone in the various polymers were substantially higher, at a particular temperature, than the corresponding values previously determined for 2,4‐dihydroxybenzophenone, being 1.4, 0.4, and 0.8 wt‐% for low‐density polyethylene, high‐density polyethylene, and polypropylene, respectively at 75°C. Studies to determine the rate of loss of the stabilizer from polymer samples immersed in water resulted in extremely low rates of extraction, in contrast to those found for 2,4‐dihydroxybenzophenone, as a result of the octoxy substituent and the resulting increase in compatibility between the stabilizer and polymer.
Graft copolymerization of nylon 6 with methyl methacrylate using dimethylaniline/Cu2+ ion system
Authors: El‐Rafie M. H. , Hebeish A. 
Published: April 2003

AbstractThe ability of dimethylaniline (DMA)/Cu2+ ion initiator to induce grafting of methyl methacrylate (MMA) onto nylon 6 was investigated under a variety of conditions. It was found that the graft yield is dependent on the concentration of the Cu2+ ion, of DMA, and of MMA. While the graft yield increases as the monomer concentration increases, there are optimal concentrations of DMA and Cu2+ ion. Below or above these concentrations, lower grafting occurred. The type of cupric salt also affects grafting to varying degrees. While the presence of CuSO4 and Cu(NO3)2 accelerates grafting, the presence of CuCl2 offsets the reaction. Increasing the reaction temperature and reaction time favorably influences grafting. Addition of acetic acid enhances grafting, whereas formic acid decreases grafting. Preswelling of nylon with formic acid leaves the susceptibility of nylon toward grafting practically unaltered. Studies of the copolymerization reaction was not confined to the graft yield but was extended to homopolymer formation and total conversion.
Permeability of polymer films to sulfur dioxide at low concentration
Authors: Davis E. G. , Rooney M. L. , Larkins P. L. 
Published: April 2003

AbstractA new apparatus is described for measuring the permeability of polymer films to sulfur dioxide at partial pressures down to 2 Pa. It employs a permeation tube technique for establishing the partial pressure gradient and a detection system based on the absorption of light at 213.8 nm. Data on the permeability to sulfur dioxide of a range of polymer films are presented and discussed.
Hydraulic permeation of liquids through swollen polymeric networks. II. Liquid mixtures
Authors: Paul D. R. , Paciotti J. D. , Ebra‐Lima O. M. 
Published: April 2003

AbstractThe hydraulic permeation of toluene–cyclohexanone and isooctane–CCl4 mixtures through a membrane, a rubber network, was studied. No separation of components occurred in this mode. The mixture flux data were successfully analyzed using a solution–diffusion theory by treating the mixture as if it were a single component with properties of the mixture. Diffusion coefficients determined in this way appear to be governed by frictional forces having a hydrodynamic origin. Slight separation of the components did occur when the pervaporation mode of operation was used. The significance of this is discussed.
Photophysical processes in poly(hexamethylene adipamide)–acid dye complexes: Energetics of nylon 66 phototendering
Authors: Koenig H. Steve , Roberts Carleton W. 
Published: April 2003

AbstractThe mechanism of dye‐sensitized photo‐oxidative degradation of nylon 66 was investigated. A known phototendering dye, C.I. Acid Blue 40 (1‐amino‐4‐(p‐aminoacetanilide)‐2‐anthraquinone sodium sulfonate), was used for this study. Excitation and emission spectra of the dyed and undyed nylons indicated that a ground‐state complex between the dye and the polyamide was formed upon dyeing. The energy level of the complex's electronic states favor triplet–triplet energy transfer from the nylon to the complex. Quenching studies show that the energy transfer occurs efficiently with a rate constant of 45.8 l. mole−1 sec−1. An additional energy transfer occurs between the excited free dye and the complex by either a singlet–triplet or a triplet–triplet mechanism. Kinetic analysis of the nylon‐complex energy transfer suggests that the triplet energy of nylon migrates 24 to 33 Å along the amide chromophores in an exciton fashion until an energy trapping complex is reached. Energy is then transferred by an exchange mechanism. Photo‐oxidative studies verify that the dye–nylon complex sensitizes the polyamide photo‐oxidative degradation at its own expense without dye photobleaching.
A study of coextrusion in a circular die
Authors: Han Chang Dae 
Published: April 2003

AbstractAn experimental study has been carried out of concentric and eccentric two‐phase flow of polymer melts in a circular die. For the study, a special die was constructed such that two separate streams of molten polymer could be supplied to the die inlet. Materials used for study were low‐density polyethylene, high‐density polyethylene, and polystyrene. In the experiment, two different capillary length‐to‐diameter (L/D) ratios were employed: 4 and 18. For a die having an L/D ratio of 18, wall normal stresses were measured, permitting the determination of the pressure gradient and hence the viscous property. For each set of extrusion conditions (L/D ratio, flow rate, component ratio), extrudate samples were collected. These were later carefully cross sectioned and photographed in order to examine the shape of the interface between the two components. It has been found that the lower‐viscosity components tends to wrap around the higher‐viscosity component, which is consistent with the previous observations reported in the literature.
Hydrogels of crosslinked poly(1‐glyceryl methacrylate) and poly(2‐hydroxypropyl methacrylamide)
Authors: Nierzwicki W. , Prins W. 
Published: April 2003

AbstractTwo hydrophilic polymer networks of different crosslinking density and varying reference degree of swelling were prepared from 2,3‐dihydroxypropyl methacrylate (glyceryl methacrylate) and N‐(2‐hydroxypropyl)methacrylamide. They were characterized by swelling and compression measurements, and the Flory‐Huggins interaction parameters were determined. The results reveal the importance of hydrophobic forces in the physical properties of poly(1‐glyceryl methacrylate). Poly(2‐hydroxypropyl methacrylamide) gels do not exhibit the presence of these specific effects.
Diffusion of deterrents into a nitrocellulose matrix. An example of diffusion with interaction
Authors: Brodman B. W. , Sipia J. A. , Schwartz S. 
Published: April 2003

AbstractThe diffusion of various concentrations of a deterrent (di‐n‐butyl phthalate) into a spherical, nitroglycerin‐containing nitrocellulose matrix was studied. It was concluded that the final concentration profile could best be explained by a diffusion with interaction mechanism. Based on this mechanism, a method for calculating the depth of deterrent penetration is presented.
A study of the performance and chemical characteristics of composite reverse osmosis membranes prepared by plasma polymerization of allylamine
Authors: Bell Alexis T. , Wydeven Theodore , Johnson Catherine C. 
Published: April 2003

AbstractA study has been carried out of the performance and chemical characteristics of composite reverse osmosis membranes prepared by plasma polymerization of allylamine in a radio‐frequency electric discharge. It has been shown that membranes can be prepared which simultaneously exhibit a high rejection for sodium chloride and a high water flux. The primary factors influencing the quality of the membranes are the choice of substrate material, the deposition time, and the power supplied to the discharge. Variations in rejection and flux as a function of applied pressure indicate that water flows through the membrane by both diffusive and bulk flow. A reduction in rejection and an increase in flux are observed when membranes are operated for prolonged periods or at higher temperatures (up to 60°C). Elemental analysis of plasma‐polymerized allylamine shows that it can be represented by the stoichiometry C3H3.8N0.9O0.1. Infrared spectra show evidence for NH, CN, CN, and CH bond vibrations. ESCA spectra of the polymer surface show that the surface contains substantial amounts of both nitrogen and oxygen and that the nitrogen is present as either a nitrile or an imine group but not as an amine group. ESCA spectra of membranes used for reverse osmosis show that the surface loses nitrogen and gains oxygen with time and that this phenomenon is accelerated at higher operating temperatures. A decrease in rejection and an increase in flux accompanies these changes. It is postulated that most of the nitrogen in the polymer is present in the form of RR′CNH or RR′CNR″ type structures. The loss of nitrogen and gain in oxygen observed in the ESCA spectra of membranes run at elevated temperatures is explained by the hydrolysis of the proposed structures.
Block polymers from isocyanate‐terminated intermediates. III. Preparation and properties of cured diene–urea block polymers
Authors: Ambrose Richard J. , Hergenrother William L. 
Published: April 2003

AbstractIsoprene–urea and butadiene–urea block polymers have been prepared by reaction of isocyanate‐terminated prepolymers with diamines and diisocyanates. It was found that the per cent of blocked urea in these copolymers is dependent on the isocyanate–diamine stoichiometry. Stress–strain data were obtained on sulfur‐cured copolymers. Stress levels at any given extension were directly dependent on the urea content, however, ultimate strength was maximized at about 35 wt‐% urea. Slight variations in urea structure produced rather dramatic changes in the modulus of these cured elastomers. Diamine–diisocyanate stoichiometry did not affect the physical properties of these cured copolymers at equal or excessive diamine concentrations. However, at excess diisocyanate levels, elastomeric properties deteriorated rapidly. Finally, stress–strain properties were affected by polymerization solvent. Copolymers prepared in hexane gave higher values of stress at low strains than corresponding elastomers prepared in toluene. These latter results are explained in terms of the nonaqueous emulsion in which the urea blocks form.
Radiation yield of hydrogen chloride in the poly(vinyl chloride) foils irradiated by accelerated electrons
Authors: Szymański W. , S̀mietańska G. 
Published: April 2003

AbstractTheGHClvalues of PVC foils, containing 18% of dioctylphthalate, irradiated with accelerated electrons were studied after addition of various amounts of the stabilizers: (I) ethylene glycol bis‐β‐aminocrotonate, (II) calcium/zinc laurate + epoxy compounds, (III) calcium/zinc stearate, (IV) dioctyltin bis(octylthioglycolate). The effect of stabilization turned out to be very good, especially when stabilizer I was used. In the case of soft PVC foils in contact with water, elution of hydrogen chloride occurs. This creates difficulties in preparing PVC foils sterilized radiatively for medical purposes, especially if the foils are expected to be in contact with water.
Physical state of radiation‐polymerized polyethylene blends
Authors: Yamaguchi Kouichi , Yagi Toshiaki , Machi Sueo , Takehisa Masaaki 
Published: April 2003

AbstractThe physical state of the blends of radiation‐polymerized polyethylene with high‐density polyethylene was studied. Only one peak was observed in DSC heating curves of the blends quenched from the melt regardless of the each polymer content. In addition, transparency of the high‐density polyethylene was improved by melt blending with radiation‐polymerized polyethylene. This is a characteristic of high‐density polyethylene and radiation‐polymerized polyethylene blends different from high‐density and low‐density polyethylene blends. A new peak and/or a new shoulder, however, appeared in DSC heating curves of the blends with heat treatment at 110°, 120°, and 125°C. These results suggest that the physical state of the blends quenched from the melt is one where the crystallization of the radiation‐polymerized polyethylene is high hindered by the presence of high‐density polyethylene. The radiation‐polymerized polyethylene may remain mainly in a physical state similar to the melt. The haze value of the blends increased with heat treatment. The increase in the haze is caused by change in physical states, such as growth of spherulites and formation of microcrystals and microvoids, by the heat treatment.