bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of rubber oxidation by thermoanalysis
Authors: Lye P. H. , Toh H. K. 
Published: April 2003

AbstractA method using the DSC was utilized whereby the oxidation of natural rubber was studied by adapting the procedures developed by Kissinger, Doyle, and Ozawa for thermoanalysis. Thus oxidative induction time of several hours for a particular rubber sample can be estimated in a relatively short time. Some of the results of this method are compared with those from other established methods, the estimated oxidative induction time showing a good correlation with some of the systems tested. The validity and limitations of this method are discussed.
Resorbable materials of poly(L‐lactide). V. Influence of secondary structure on the mechanical properties and hydrolyzability of poly(L‐lactide) fibers produced by a dry‐spinning method
Authors: Leenslag J. W. , Gogolewski S. , Pennings A. J. 
Published: April 2003

AbstractFibers of poly(L‐lactide) (PLLA) with a loosened fibrillar structure were produced by solution spinning from a good solvent (chloroform) in the presence of various additives (camphor, polyurethanes). No decrease in mechanical properties was observed as compared with PLLA fibers spun from a good solvent only. In vitro degradation studies showed that the rate of degradation of PLLA fibers with the loosened fibrillar structure was increased approaching that found for fibers composed of the homopolymer of glycolide or copolymers of glycolide and L‐lactide. Helices on the fiber surface caused by melt fracture during spinning of the fibers leads to higher knot strengths of the hot‐drawn PLLA fiber up to 70% of the tensile strength.
Grafting of poly(methyl methacrylate) in aqueous slurries of wood pulp
Authors: De Carvalho Laura Hecker , Rudin Alfred 
Published: April 2003

AbstractMethods for initiating the free radical graft polymerization of methyl methacrylate onto wood pulp were investigated. Processes considered were all carried out in water slurries of the cellulose, for simplicity and low cost. Of the methods studied only three provided high conversions of monomer to polymer and reasonably good grafting efficiencies. These are ceric ion initiation, a redox reaction with ferrous ion and hydrogen peroxide, and initiation by potassium permanganate/nitric acid mixtures. The ferrous ion/peroxide redox system appears to be the best procedure overall, since it is inexpensive and environmentally innocuous. The best grafting frequency obtained was about one graft per 800 anhydroglucose units in the cellulose. High molecular weight poly(methyl methacrylate) polymers were made, with the grafted species larger than the corresponding homopolymers.
Electrokinetic properties of acrylic acid‐ and methacrylic acid‐grafted polypropylene during chemically initiated graft copolymerization
Authors: Lokhande H. T. , Thakar V. S. , Shukla S. R. 
Published: April 2003

AbstractElectrokinetic properties such as zeta potential (ζ), surface charge density (σ) and surface conductivity (Ks) of polypropylene fibers and those grafted with acrylic acid and methacrylic acid have been studied using the streaming potential method. At pH 7, the zeta potential of −58.5 mV for control fibers reduced with increase in the amount of acrylic acid (16.2%) and methacrylic acid (28.2%) grafts to −38.15 mV and −38.30 mV, respectively. The drop in the negative zeta potential value is attributed to rendering polypropylene hydrophilic. The acrylic acid graft was found to be more effective than the equivalent amount of methacrylic acid graft in this respect due to the different chemical characters of the two graft copolymers. The negative zeta potential was also reduced to a considerable extent when cationic dye solution was streamed through the grafted polypropylene fibers, which is attributed to the deposition of dye cations on the negatively charged surface of the grafted fibers. The results on surface charge density and surface conductivity also indicated the hydrophilic character of grafted polypropylene.
Impregnation of mortars with monomers and their radiolytic polymerization
Authors: Gadalla Ahmed M. , El‐Derini Mohamed E. 
Published: April 2003

AbstractMortars were cured for a sufficient period to give sufficient strength and were then dried to remove the free water without dehydrating the compounds formed. Dried specimens were evacuated and impregnated with a mixture of styrene and acrylonitrile monomers which gives high mechanical properties after polymerization. Positive pressure was then applied, and polymerization was done radiolytically. The effect of degree and period of evacuation, the positive pressure and the irradiation dose on monomer loading, tensile and compressive strength were studied, and the optimum operating conditions were established. The achieved strength was correlated with the fraction of open pores impregnated. The composites investigated have the same volume fraction of mortar, and the polymer is added at the expense of the open porosity causing nearly an exponential increase in strength. Only 80% of the open pores were filled with polymers due to the difference in density between the polymer and the monomer, loss of monomer, and the presence of entrapped gas consisting of residual air and residual water vapor and monomer vapor, as well as due to the inability to fill all the micropores with monomer. A compressive strength four times that of plain mortar and a tensile strength eight times that of plain mortar were achieved.
Hydrolysis of dextrin in the presence of 12‐tungstosilicic acid
Authors: Arai Kenichiro , Ogiwara Yoshitaka 
Published: April 2003

AbstractHydrolysis of dextrin in the presence of 12‐Tungstosilicic acid was investigated, and the acid was found to show an approximately two times higher catalytic activity than did hydrochloric acid. From the comparison of degree of dissociation of 12‐tungstosilicic acid with that of hydrochloric acid, examination of the influence of the ionic strength on the reaction rates, analysis of the reaction products, and evaluation of activation parameters of the reaction, it was assumed in conclusion that the higher catalytic activity of 12‐tungstosilicic acid resulted from a “concentration effect” due to the complex formation of the heteropolyanions with dextrin molecules, and from the effect of its higher ionic strength, but not from the effect of direct participation of the heteropolyanion to the elementary reaction process.
Durability of adhesive bonds between glass or metal substrates and a polybutadiene–polyurethane
Authors: Liang Fasi , Dreyfuss P. 
Published: April 2003

AbstractThe durability of polybutadiene–polyurethane joints to glass or metals in water at elevated temperatures was studied. The effects of silane pretreatment of the surface and of surface morphology on adhesion were examined. The durability of the joint was related to the number of chemical bonds that could form between the polyurethane and the surface and to the type of surface treatment given to the surface. Proper treatment led to significant enhancement of durability of the joints.
Epoxy resin cure. II. FTIR analysis
Authors: Smith Robert E. , Larsen Fred N. , Long Charles L. 
Published: April 2003

AbstractFourier transform infrared (FTIR) spectroscopy is used to determine the cure rate of an epoxy resin consisting of Tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) and diaminodiphenylsulfone (DDS). Cure rates at 120 and 160°C are shown to increase noticeably when 1% BF3–MEA is added to either TGDDM to TGDDM plus DDS. Fluoroboric acid is shown to increase the cure rates even more than the BF3–MEA. These Results combined with the NMR results in the accompanying article indicate that BF3–MEA is not a catalyst for epoxy resin cure. Instead it is rapidly hydrolyzed to fluoroboric acid which acts as the catalyst.
Resins containing extractants: Morphology of polymers prepared by polymerization of vinyl monomers in the presence of uranium‐selective extractants
Authors: Belfer S. , Egozy Y. , Korngold E. 
Published: April 2003

AbstractThe effect of a selective organophosphours extractant on the structure and properties of crosslinked polymers was studied. The extractant, incorporated in the polymerization mixture, affected the formation of the polymer. The uranium capacity of the resin was directly proportional to the amount of extractant. The use of scanning electron microscopy showed that the polymers are macroporous and that the porosity depends on the amounts of extractant and crosslinking agent.
Dependence of electrical breakdown on spherulite size in isotactic polypropylene
Authors: Ceres B. V. , Schultz J. M. 
Published: April 2003

AbstractA self‐seeding technique, coupled with isothermal crystallization, was used to prepare isotactic polypropylene specimens of varying spherulite size, but of constant crystallinity and lamellar thickness. The latter quantities were also varied by changing the isothermal crystallization temperature. The electrical lifetime at constant applied voltage, in a point‐plane geometry, was measured. It was found that the electrical lifetime decreased with increasing spherulite size and, more weakly, with decreasing crystallinity (at a given spherulite size).
The effect of coatings on the surface precipitation of oilgomeric crystals in poly(ethylene terephthalate) films
Authors: Perovic A. , Murti D. K. 
Published: April 2003

AbstractCrystalline particles of cyclic oligomers are formed on the surface of poly(ethylene terephthalate) (PET) films during heat treatment or exposure to solvent vapor. The formation of crystals of oligomers due to heat treatment can be prevented by depositing onto the PET films morphologically continuous coatings of various elements. The critical thickness of the coating which effectively stops nucleation of these crystals depends on the element deposited under given experimental conditions. In the case of solvent (methylene chloride) exposure, the most important factor preventing oligomer crystallization was the chemical nature of the element used as a coating.
Crystalline morphology of polypropylene and rubber‐modified polypropylene
Authors: Jang B. Z. , Uhlmann D. R. , Sande J. B. Vander 
Published: April 2003

AbstractThe crystalline morphology of injection‐molded polypropylene (PP), its relationship with crazing, and the effects of various impact modifiers on the morphology, crystallization, and fusion of PP have been studied. The highly oriented skin layer of an injection‐molded tensile bar after deformation was found to be free from crazing in contrast to the heavy craze density in the randomly oriented spherulitic core zone. Reasons for the difficulty in craze nucleation in a preoriented zone are given in light of Argon's theory of craze initiation. Addition of a rubbery phase results in an irregular texture of spherulite, smaller spherulitic diameter, and decrease in the degree of undercooling, but no appreciable change in heats of fusion and crystallization other than a trivial volume effect. The rubbery phase is not pushed by the melt–solid interface to relocate to the interspherulitic boundaries. Rather, it is engulfed by the growing melt–solid interface, leaving behind a random spatial distribution of rubber particles in the PP matrix.
Radiation‐induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. V. Studies on thermal behavior
Authors: Bhattacharyya S. N. , Maldas D. 
Published: April 2003

AbstractThe thermal behaviors of cellulose acetate, either grafted or ungrafted, were studied. A thermogram of cellulose acetate when grafted with acrylamide is characterized by an endothermic peak at 340°C. If, however, styrene is grafted, the thermogram shows two characteristic exothermic peaks at 330 and 420°C. A thermogram of the mixed graft comprising both acrylamide and styrene, on the other hand, is characterized by only one exothermic peak at 420°C. A consideration of various thermal data indicates that cellulose acetate when grafted is comparatively more stable than when not grafted. Again, styrene is found to be more effective than acrylamide in increasing the stability.
Mechanical properties of blends of nylon 6 with a chemically modified polyolefin
Authors: Chuang Hsiao‐Ken , Han Chang Dae 
Published: April 2003

AbstractBoth tensile and impact properties were measured of a heterogeneous polymer blend system, consisting of nylon 6 and a chemically modified polyolefin, DuPont CXA3095, which is an ethylene‐based multifunctional polymer. It was found, from the tensile testing, that the blends exhibited no signs of necking, and the addition of a soft resin (CXA3095) reduced the modulus and the tensile strength of nylon 6, whereas the percent elongation at break went through a minimum. When 20 wt % of CXA3095 was added to nylon 6, the impact strength was increased approximately three times. When the factors describing the interfacial adhesion were incorporated, the existing models for predicting the tensile modulus of blends were found to describe the experimental data rather well. In order to help explain the mechanical behavior observed, photomicrographs were taken of the fracture surfaces, using a scanning electron microscope.
Differential scanning calorimetry studies of the cure of carbon fiber–epoxy composite prepregs
Authors: Morgan Roger J. , Walkup Connie M. , Hoheisel Tom H. 
Published: April 2003

AbstractDiaminodiphenyl sulfone (DDS) cured tetraglycidyl‐4,4'‐diaminodiphenyl methane (TGDDM) epoxies, whose cure reactions are accelerated by BF3:amine catalysts, are the most common composite matrices utilized in aerospace high performance, fibrous composites. To process reproducible composites requires an understanding of the cure reactions and how these reactions are modified by the BF3:amine catalysts. In this article we report systematic differential scanning calorimetry (DSC) studies of (i) the constituents of BF3:NH2C2H5‐catalyzed TGDDM–DDS epoxies and their mixtures, (ii) the effect of BF3:NH2C2H5 concentration on the cure reactions, (iii) the nature of the catalyzed cure reactions, and (iv) the environmental sensitivity of the catalyst. DSC studies are also reported on the cure reaction characteristics and environmental sensitivity of commercial C fiber–TGDDM–DDS epoxy prepregs.
Oxidative skeleton breaking in epoxy–amine networks
Authors: Bellenger V. , Verdu J. 
Published: April 2003

AbstractThe photo and thermal oxidation of various epoxide–amine tridimensional polycondensates is studied by IR spectrophotometry and DSC. The network degradation results in a decrease of the glass transition temperature (Tg), which is correlated with the quantity of amide groups formed. For each system, the relative yield in skeleton breaks increases with the intensity of internal stresses. A mechanism involving the β scission of α amino alkoxy macroradicals resulting from oxidation of constrained segments of the network is proposed.
Mechanical properties of clay coating films containing styrene–butadiene copolymers
Authors: Parpaillon M. , Engström G. , Pettersson I. , Fineman I. , Svanson S. E. , Dellenfalk B. , Rigdahl M. 
Published: April 2003

AbstractThe mechanical properties of clay‐based pigmented coating films bonded with a series of carboxylated styrene–butadiene latex binders have been investigated. The in‐plane tensile strength and the elongation at rupture increased with increasing amount of polymeric binder. It is suggested that this is due to an improvement in stress transfer through the structure. The mechanical behavior of the films was furthermore found to be strongly related to the properties of the polymeric binder at the usage temperature. In torsional pendulum experiments an increase in the glass transition temperature of the polymeric binder was observed when it was incorporated in the coating film. This is interpreted as being the result of a decrease in the segmental mobility of the polymer molecules due to the presence of the clay particles, i.e., due to the interaction between the clay pigments and the binder. The interaction was, however, less noticeable in experiments using an NMR (nuclear magnetic resonance) technique. If the clay was replaced by calcium carbonate, a strong interaction, as measured using NMR, was observed between CaCO3 and the styrene–butadiene polymer, although the in‐plane mechanical strength and ductility were reduced. A structural model accounting for some of the observed differences in mechanical behavior between clay‐based and CaCO3‐based coating films is suggested.
Overall NCO/OH ratio and microphase separation in urethane elastomers
Authors: Nierzwicki W. 
Published: April 2003

AbstractSeveral polyurethanes were prepared from poly(ethylene adipate) glycol, 4,4′‐diphenylmethane diisocyanate (MDI), and 1,4‐butanediol. The overall NCO/OH ratio was allowed to vary from 0.94 to 1.21. Thus, the obtained elastomers differed in the amount of allophanate groups and perfection of microphase separation. These effects were studied by dielectric and pulsed NMR techniques. The results show that quite subtle effects concerning molecular mobility and its restriction due to interfacial region, perfection of the separation, and inadequacy of thermomechanical measurements can be investigated in the presented way.
Water permeation in polymer films. VII. Polyimide/Teflon FEP laminates
Authors: Sacher E. , Susko J. R. 
Published: April 2003

AbstractPermeation parameters were obtained for various commercial polyimide/Teflon FEP laminates. Permeation coefficients, predicted from data obtained separately on each component of the laminate, match closely those found experimentally. The diffusion and solubility coefficient values, which are not amenable to such predictions, demonstrate that closely similar permeation coefficient values may be obtained from widely different diffusion and solubility coefficient values.
Behavior of polymers containing spiroorthoester or bicycloorthoester structure under EB and X‐ray irradiation conditions
Authors: Tanigaki Katsumi , Saigo Kazuhide , Ohnishi Yoshitake , Kato Hitoshi , Mizutani Kiyokazu , Ogasawara Takahisa , Endo Takeshi 
Published: April 2003

AbstractReaction behavior of spiroorthoester and bicycloorthoester to EB and X‐ray irradiations has been studied on the basis of infrared spectroscopic analysis. The polymers containing these functional groups showed markedly high sensitivity to EB and X‐ray. The formations of CO and OH after exposure indicate that these functional groups react through ring opening even in the absence of any cationic catalyst. In the high energy‐induced reaction, sensitivity and post‐irradiation polymerization effect were found to be greatly influenced by the polymer structure, different from those observed in the cation‐induced reaction.
Mechanical behavior of poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends
Authors: Rim P. B. , Runt J. 
Published: April 2003

AbstractThe mechanical properties of compatible poly(ε‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends were studied for samples prepared from both the melt and solution. The mechanical response was observed to be primarily dependent upon the variation of the glass transition temperature with blend composition. For certain compositions, varying the sample preparation scheme resulted in specimens of different modulus. This behavior was associated with differences in the degree of crystallinity.
Analysis of the theoretical methods of calculations of ideal fiber birefringences
Authors: Włochowicz Andrzej , Janicki Jarosław , Rabiej Stanisław 
Published: April 2003

AbstractBased on the equation carried out previously, theoretical birefringence has been calculated for selected synthetic fibers, taking into account intermolecular interactions. The calculation has been carried out using bond polarizabilities given by Denbigh [Trans. Faraday Soc., 36, 936 (1940)] and Pietralla [J. Polym. Sci., Polym. Phys. Ed., 18, 1117 (1984); 20, 1193 (1982)]. Large discrepancies of Δnid for polyamides between theoretical and experimental values have been found. The necessity for elaborating a new method of birefringence calculations has been pointed out.
Dye leveling in PET fibers. II. Mathematical model
Authors: Simal Abigail Lisbão , Bell James P. 
Published: April 2003

AbstractA mathematical model is developed for the dye leveling process. Good agreement between experimental and theoretical data supports the validity of the proposed model. Also, the applicability of the proposed model is shown through its effectiveness in predicting leveling times, when the working temperature is above the Tg of the fibers. The results demonstrate that chain mobility is a prerequisite for rapid leveling, and that morphological changes in the fiber during the migration process are important and must be considered.
Effect of aggregation states on some properties of PVC solids and melts
Authors: Ajji A. , Jérémie G. , Rudin Alfred , Schreiber H. P. 
Published: April 2003

AbstractPlasticized compounds of poly(vinyl chloride) (PVC) have been prepared using PVC polymer as supplied and as recovered from solutions in tetrahydrofuran. Mechanical properties and melt elasticity measurements were found to vary significantly among these compounds. It is proposed that the solid‐state characteristics and melt elasticity parameters in these compounds depend on the state of chain entanglement and that the entanglement state can be modified significantly by procedures such as used here. Annealing experiments have shown that the rates of attaining property equilibria—symptomatic of equilibrium entanglement states—are dependent on diffusion processes. Neither solution‐modified nor control PVC compounds are in steady states when first tested; consequently, time‐dependent property variations may be expected as morphological steady states are attained at conventional use temperatures for PVC compounds. The present study extends to PVC the principles of entanglement network modification through solution, or shearing processes, as a means of selecting preferred property balances in melt processing and mechanical properties. That principle had earlier been shown to apply to polyethylenes.
Surface characterization of a titanate coupling agents modified sepiolite
Authors: Arroyo M. , Iglesias A. , Perez F. 
Published: April 2003

AbstractThe surface treatment of a sepiolite with two different titanate coupling agents has been studied. The results obtained from several chemical and physical analytical methods used for the organophylized surface characterization have shown a monolayer reaction has taken place. An attempt to relate the degree of organophylization to the specific surface decrease of filler has been made.
Radiation‐induced graft copolymerization of methacrylic acid onto polypropylene fibers. I. Effect of synthesis conditions
Authors: Mukherjee A. K. , Gupta B. D. 
Published: April 2003

AbstractThe gamma radiation‐induced graft copolymerization of methacrylic acid onto polypropylene fibers was investigated by simultaneous—irradiation technique. The effect of various synthesis conditions on the graft content was studied. At a constant dose, the percent grafting was found to be higher at low dose rate. For all the dose rates, a linear increase in the grafting was observed up to 0.25 Mrad, beyond which the grafting levelled off. Percent grafting also increased continuously with increasing monomer concentration up to 4.0 mol/L, but a linear increase in grafting was observed only up to 2.0 mol/L. The initial rate of grafting increased with the increase in dose rate and monomer concentration. The dependence of rate of grafting on dose rate and monomer concentration was found to be 0.70 and 1.71, respectively. The effect of liquor ratio upon grafting was also studied.