bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of relative humidity on the mechanical properties of poly(1,4‐butylene terephthalate)
Authors: Gardner R. J. , Martin J. R. 
Published: April 2003

AbstractThree grades of poly(1,4‐butylene terephthalate) (PBT) were aged up to three years at 100, 75, 50, and 11% relative humidity and temperatures of 66–93°C. The decrease in mechanical properties, caused by hydrolysis, occurs rapidly at the higher temperatures and relative humidities and progressively slows as the temperature and/or humidity are decreased. Equations for making life‐cycle predictions at any combination of temperature and humidity were derived from Arrhenius plots. If a 50% loss in tensile strength constitutes failure, then the PBT examined should be expected to last only three to four years at 50°C and 100% relative humidity. Reducing the humidity level to 50% extends the useful life at this temperature to 10–20 years. Predictions based on the tensile strength half‐life should not be used where toughness or impact properties are important because PBT embrittles long before the tensile strength half‐life is reached.
Reinforcement of siloxane elastomers by silica. Chemical interactions between an oligomer of poly(dimethylsiloxane) and a fumed silica
Authors: Berrod G. , Vidal A. , Papirer E. , Donnet J. B. 
Published: April 2003

AbstractThe study of the interactions between an organosiloxane and a fumed silica was undertaken in order to improve our knowledge of the reinforcement of silicon rubbers by silica. IR spectroscopy, gravimetry, and chromatography techniques were used to characterize the chemical interactions taking place above 150°C between octamethylcyclotetrasiloxane and a fumed silica which yield silicas modified by grafted siloxanes. Reaction mechanisms were proposed for the interpretation of the grafting processes. They were checked by the study of the reaction of water with octamethylcyclotetrasiloxane. The results obtained suggest that the reactions proceed through an attack of the siloxane by the surface free silanol groups of silica, causing an opening of the siloxane cycle and the grafting of the subsequent material on the surface of the filler. It was shown that the siloxane‐modified silicas exhibit a high thermal stability.
Rubber‐modified epoxies. I. Transitions and morphology
Authors: Manzione L. T. , Gillham J. K. , McPherson C. A. 
Published: April 2003

AbstractA variety of different morphologies, and therefore mechanical properties, can be obtained from a single rubber‐modified epoxy formulation. The volume fraction, domain size, and the number of particles of phase‐separated rubber are determined by the competing effects of incompatibility, rate of nucleation and domain growth, and the quenching of morphological development by gelation. These factors can be varied by the butadience/acrylonitrile ratio of the reactive rubber, the temperature of cure, and the gelation time. These ideas have been exploited to control the development of morphology of these amorphous systems. Phase separation was investigated by electron microscopy, viscometry, and dynamic mechanical analysis.
Infrared study of the effect of heat on wool
Authors: Moharram M. A. , Abdel‐Rehim T. Z. , Rabie S. M. 
Published: April 2003

AbstractThe infrared spectra of wool heated in vacuum and in air to different temperatures ranging from 120 to 250°C were investigated. It was found that certain absorption bands disappear when wool is heated in vacuum to 180°C and in air to 120°C for 2 hr. Also, the results showed that the intensities of the C=O stretching band at 1660 cm−1, N–H stretching band at 3325 cm−1 and the C–H stretching band at 2940 cm−1 decrease when wool is heated in vacuum to 180°C and in air to 120°C. The spectra of the samples heated in vacuum to 250°C and in air to 225°C exhibited strong absorption bands belonging to the carboxyl and sulfonate groups.
Poly(methyl methacrylate)–cellulose nitrate copolymers. II. Physical and mechanical properties
Authors: Badran B. M. , Sherif Sayed , El‐Sheltawi Sh. T. , Abu‐Sedira A. A. 
Published: April 2003

AbstractPoly(methyl methacrylate)–cellulose nitrate copolymers were prepared by bulk polymerization using benzoyl peroxide as initiator. Cellulose nitrates of two different nitrogen contents (11.4 and 12.2%) were used. The prepared copolymers were γ‐irradiated for specified periods of up to 11.83 Mrad. Their physical and mechanical properties were measured before and after irradiation. The title copolymers showed lower modulus, tensile strength, and elongation at break than poly(methyl methacrylate) itself, but they showed better hardness and abrasion. Irradiation to up to 6.57 Mrad improved the modulus of the copolymers. Hardness and abrasion were improved by increasing cellulose nitrate content. The prepared copolymers that contained cellulose nitrate of 11.4% nitrogen showed secondary transition points. The increase of cellulose nitrate concentration shifted both first and second transition points to relatively higher values.
Graft polymerization of methyl methacrylate onto chemically modified wools using LiBr–K2S2O8 redox system as initiator
Authors: Niezette J. , Geurts R. , Erilli R. 
Published: April 2003

AbstractGraft polymerizations of methyl methacrylate onto natural, reduced, S‐carboxymethylated, S‐aminoethylated, sulfated, acetylated, and oxidized wools were performed at 30°C using a LiBr–K2S2O8 redox system as initiator. The extent of grafting was found to be dependent on the thiol and amino contents of wool fibers; carboxylic, sulfated groups, and oxidation intermediates had no significative influence on graft yields. The polymethacrylic chains obtained after hydrolysis of the natural part of the copolymer and analyzed by infrared and NMR spectroscopies were characterized by an atactic structure quite comparable to that found for a corresponding homopolymer. There was no stereoregulating effect on methyl methacrylate polymerization due to the crystalline components of the wool structure. A quantitative determination of the number of amino acid residues linked to the end of polymethacrylic chains after hydrolysis indicated that chain termination occurs both by disproportionation and recombination of macroradicals for natural, sulfated, S‐carboxymethylated, and S‐aminoethylated wools; for reduced and oxidized wools, only a recombination by disproportionation was observed in accordance with the open structure of these wool fibers. The chain lengths of the isolated poly(methyl methacrylates) were also found to be consistent with the participation of thiol and amino groups in grafting. It seems, however, that amino groups do not themselves act as initiating sites.
Corrosion of polymer–concrete composites in hydrochloric acid at elevated temperature
Authors: Yeo R. S. , Zeldin A. N. , Kukacka L. E. 
Published: April 2003

AbstractA series of polymer–concrete (PC) materials were evaluated in 30% hydrochloric acid at 90°C. It was shown that a polymer aggregated with quartz sand is a potential candidate for use in coating or construction materials for hydrogen–chlorine energy storage systems. The results have shown that the corrosion rate of PC in this solution is a diffusion‐;controlled process. The major weight loss can be attributed to the presence of cement in the PC samples. The influence of the sand/cement ratio, and the crosslinking agent content on the corrosion of PC samples is also discussed.
Photochemistry of polymeric systems. III. Photocrosslinking of polymers and copolymers including cyanocinnamylydene–pyridinium groups
Authors: Roucoux Colette , Loucheux Claude , Lablache‐;Combier Alain 
Published: April 2003

AbstractPhotocrosslinkable polymers were obtained by reacting esters of cinnamic acid or cyanocinnamylideneacetic acid onto pyridine units of a homopolymer or onto a suitable copolymer. These photosensitive polymers were characterized by conventional analysis and spectrometry. The photocrosslinking was studied on thin films measuring the threshold of insolubilization together with UV and IR spectrometry.
Photochemistry of polymeric systems. IV. Photocrosslinking of copolymers including pyridinium dicyanomethylide groups
Authors: Cottart Jean‐;Jacques , Loucheux Claude , Lablache‐;Combier Alain 
Published: April 2003

AbstractPhotocrosslinkable polymers were obtained by reacting tetracyanoethylene oxide with pyridine units of suitable copolymer. Copolymers of styrene and 4‐;vinylpyridine dicyanomethylide were synthetized and studied. The methods used for characterization of photocrosslinked films were a “photoresist test” or the measurement of the insolubilization ratio. The reaction is favored by triplet‐;state sensitizers such as Michler's ketone. The photosensitivity of the copolymers was determined as a function of the wavelength of the radiation used.
Studies on thermal degradation of synthetic polymers. XV. Estimation of the product yield on the basis of intensity function for thermal gasification of isotactic and atactic polypropylenes
Authors: Sawaguchi Takashi , Suzuki Kazumasa , Kuroki Takeshi , Ikemura Takashi 
Published: April 2003

AbstractThe kinetic equation for the pyrolysis gasification reaction of isotactic and atactic polypropylenes has been established. The difference in tacticity of the samples does not much affect the kinetic parameters. The exponent a of the intensity function IF = Tδa (K·seca), concerning the severity of decomposition conditions, has been approximated as 0.039 (isotactic) and 0.040 (atactic), respectively from the kinetic parameters in this experiment. The calculated values of the product yield from Arrhenius equations, k = 2.0 × 1010 exp(−40.9 × 103/RIF) (isotactic) and k = 1.2 × 1010 exp(–41.4 × 103/RIF) (atactic), for the IF standard agree with the experimental values.
Radiation‐induced oxidative degradation of isotactic polypropylene
Authors: Hegazy El‐Sayed A. , Seguchi Tadao , Arakawa Kazuo , Machi Sueo 
Published: April 2003

AbstractGas evolution, oxygen consumption, and change of mechanical properties were studied for the γ‐ray irradiation of isotactic polypropylene from 60Co under various conditions, such as vacuum, air, and oxygen at room temperature. For irradiation under vacuum, G(H2) = 2.9 and G (CH4) = 0.09; the G values for other gases were very small. In the presence of oxygen, G(H2) was the same, and the G values for other hydrocarbons were two times those under vacuum. The G values of oxidative products and oxygen consumption were G(CO2) = 2.5, G(CO) = 1.1, and G(O2) = 50 at oxygen pressure of 500 torr and were dependent on oxygen pressure. With irradiation under vacuum at 2–3 Mrad, mechanical properties scarcely changes immediately after irradiation but degrade gradually with storage time in air at room temperature.
Application of refractive index measurements to polymer analysis
Authors: Samuels Robert Joel 
Published: April 2003

AbstractThe availability of a simple experimental technique for determining the three principal refractive indices of an anisotropic film (here defined as the trirefringence technique) makes possible a wide range of optical criteria for evaluating property and processing variables. The present study considers different applications of the refractive index information in order to show the versatility and practical utility of the technique. For example, a normalization procedure is developed which determines equivalent optical anisotropic states of films. This allows films produced by different multiaxial fabrication processes to be compared. Similarly, procedures are described for characterizing the crystallinity, the angular optical distribution in the plane of the film, and other interesting applications of the refractive index information.
Measuring diffusion coefficients by hygroelasticity
Authors: Marom G. , Broutman L. J. 
Published: April 2003

AbstractA new method for obtaining diffusion coefficients of polymers and composites by measuring relative length changes is proposed. The method is based on interrelating diffusivity and hygroelasticity, and it is applicable to materials whose dynamic and equilibrium stage coefficients of hygroelasticity are equal.
Polymer solutions from latexes
Authors: Wong Chi Shing , Rodriguez Ferdinand 
Published: April 2003

AbstractIn order to characterize a polymer by its reduced viscosity, it is necessary to put it into solution. For polymer made by emulsion polymerization, this usually involves coagulating the latex, washing and drying the coagulum, and then dissolving the residue in an organic solvent. The method fails when the polymer crosslinks on drying, as is the case with some adhesive resins. The method proposed here uses mixtures of N‐methylpyrrolidone (NMP) and tetrahydrofuran (THF) to put the polymer directly into solution without removing the water. The technique is applicable to many polymers and copolymers of ethyl acrylate and vinyl acetate.
Effect of oven aging on polypropylene
Authors: Wyzgoski M. G. 
Published: April 2003

AbstractInjection‐molded tensile bars of unstabilized polypropylene were oven aged at 90°C. After an induction period, tensile elongation decreased catastrophically. During the induction period no evidence of oxidation was observed by infrared reflectance; however, a definite surface etching was noted by electron microscopy. Differential scanning calorimetry measurements indicated that, for samples aged beyond the induction time, oxidative degradation caused a decrease in the melting temperature of polypropylene. Toluene immersion was used to remove selectively material from the surface of tensile bars aged for various times. Using this technique, changes in melting behavior were observed for partially aged polypropylene even prior to the catastrophic decrease in tensile elongation. Similarly, oxidation products and a reduction in molecular weight were detected for the dissolved surface layer during the apparent induction time. Results indicate that molecular weight measurement is the most sensitive indicator of oxidative degradation during the induction period.
Hydrolytic degradation of polyglycolic acid: Tensile strength and crystallinity study
Authors: Chu C. C. 
Published: April 2003

AbstractThe hydrolytic degradation of polyglycolic acid (PGA) was studied by examining the changes of tensile strength and the level of crystallinity of the suture material. It was found that the breaking stress decreased from 6.369 × 10−1at 0 day to 3.97 × 10−3Newton/Tex at 49 days. The sigmodial shape of the stress–strain curves gradually disappeared with increase in the duration ofin vitradegradation. The endpoint titration method used to assess the degree of degradation beyond the period of measurable tensile strength showed that the percent of PGA degraded were 42, 56, and 70% at 49, 60, and 90 days, respectively. The level of crystallinity of PGA at various durations of degradation exhibited an initial increase in the degree of crystallinity from 40% at 0 day to an upper limit of 52% at 21 days, then gradual decrease to 23% at 90 days. This observation is essentially parallel to hydrolysis of cellulose and polyethylene terephthalate. The concept of microfibrillar structure of fibers provides the basis for the proposed degradation mechanism of PGAin vitro.It is believed that degradation proceeds through two main stages which are different in rate of degradation.
The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. II. The elastic modulus and its dependence on structure
Authors: Gupta V. B. , Kumar Satish 
Published: April 2003

AbstractThe effects of temperature, time of heat setting, and rate of cooling on the elastic modulus of free‐and taut‐annealed poly(ethylene terephthalate) (PET) fibers were determined at different time scales using Instron, Rheovibron, and pulse propagation meter. The correlation of the elastic modulus with structure is critically examined in terms of the widely used simple one‐phase and two‐phase models for fiber modulus. It is concluded that these simple models are not universally applicable.
Crack‐tip plastic zones in glassy polymers under small‐scale yielding
Authors: Gdoutos E. E. 
Published: April 2003

AbstractTwo pressure‐modified von Mises yield criteria were used for the determination of the plastic zones developed around cracks subjected to opening‐mode loading conditions in glassy polymers. These criteria take into account the particular behavior of glassy polymers expressed by the dependence of their yield locus on the hydrostatic stress component and the difference in their tensile and compressive yield stresses. It was found that both criteria predict larger plastic zones than those obtained by the von Mises criterion which increase as the ratio of the compressive to tensile yield stress also increases. Furthermore, it was established that the differences in the predictions of plastic zones between the two criteria and the von Mises criterion increase with the Poisson's ratio of the material of the cracked plate.
Characterization of cured polystyrylpyridine by model compounds
Authors: Hsu Ming‐Ta S. , Rosenberg Mark L. , Parker John A. , Heimbuch Alvin H. 
Published: April 2003

AbstractThe crosslinking or curing reaction of polystyrylpyridine (PSP) has been studied by means of thermal reactions of its model compounds. Compounds 2,6‐distyrylpyridine, 4‐stilbazole (4‐styrylpyridine), and deuterated 4‐stilbazole were pyrolyzed at 200–325°C both in air and under vacuum in a sealed tube. The major pyrolysis products were diarylethane and stilbene, and were characterized by gas chromatography‐mass spectrometry. Major dimeric products were naphthalene or quinoline derivatives. Mechanisms for the pyrolysis are suggested, and a crosslinked structure for cured PSP is proposed based on the thermal reaction products of model compounds.
Compatibility in a blend of poly(2,3‐dichloro‐1‐propyl acrylate) and poly(glycidyl methacrylate–co–ethyl acrylate)
Authors: Davis D. D. , Taylor G. N. , Kwei T. K. 
Published: April 2003

AbstractThe compatibility of mixtures of poly(2,3‐dichloro‐1‐propyl acrylate) and poly(glycidyl methacrylate–co–ethyl acrylate) has been investigated by measurement of the following properties: density, light transmission, glass transition temperature, vapor absorption, and NMR relaxation times. To varying degrees, all results provided evidence supporting the contention that these mixtures are compatible.
Preparation of amphoteric latex by modification of styrene–acrylamide copolymer latex
Authors: Kawaguchi Haruma , Hoshino Hirotomo , Ohtsuka Yasuji 
Published: April 2003

AbstractStyrene–acrylamide copolymer latex prepared from the polymerization in an emulsifier‐free aqueous medium was treated with hypochlorite and sodium hydroxide. The resulting latex indicated amphoteric property due to amino and carboxyl groups formed by the Hofmann reaction and competitive hydrolysis of amide groups, respectively. Amphoteric latices with the same particle size but different charge density (1.0–3.0 ionic groups/100 Å2) and different isoelectric points (6.4–9.2) have been prepared by changing the reaction conditions.
Surface characterization of polyester fibers
Authors: Gillberg Gunilla , Kemp David 
Published: April 2003

AbstractFibers made from poly(ethylene terephthalate) (PET) are characterized by a hydrophobic surface with low reactivity. Modifications of the PET surface to render a higher degree of hydrophilicity and reactivity are therefore common. The modification often involves a surface layer of only a few nanometers thickness. The relatively low fraction of the modified surface layer and the fact that it is generally an organic modification on a thin curved organic substrate presents difficulties in surface analyses. Surface characterization is, however, of high importance in the evaluation of the degree and durability of a given surface modification. The paper will discuss the possibilities and the limits of using wettability studies according to the Wilhelmy method to evaluate the degree of surface modification and its permanence. Comparison between internal and external reflection Fourier‐transform infrared spectroscopy will be made. The use of electron spectroscopy for chemical analysis, secondary ion mass spectrometry, laser microprobe mass analysis, and microprobe molecular optics laser examiner will be illustrated. Data will be presented from studies of model yarns and films coated with D‐417 dip.
Grafting of methyl methacrylate on EPR and EPDR: Impact properties of polyvinyl chloride grafted polymer blends
Authors: Beati E. , Pegoraro M. , Briano M. 
Published: April 2003

AbstractEPDM rubber can be brought into water suspension after swelling in n‐heptane containing proper emulsifiers and in shear stress; particles reach dimensions as low as 150 Å. Methyl methacrylate in emulsion can be grafted easily with Bz2O2 on the rubber. Grafting yields depend particularly on the monomer/rubber ratio. The grafted polymer can be recovered by precipitating the emulsion with acetone, which eliminates the homopolymer. The grafting mechanism is discussed in terms of different initiators (AIBN and Bz2O2) and unsaturated (EPDM) and saturated rubber (EPR); AIBN and PMMA radicals were inactive in abstracting hydrogen atoms from rubber chains. Mechanical properties of the blends with PVC of the raw graft product are discussed on the basis of the grafted polymer composition and synthesis conditions. Very high impact strength can be reached at 15% rubber content in the blend for a grafted polymer obtained from a monomer/rubber ratio equal to 0.75.
Trivalent manganese chelate‐initiated graft copolymerization of methyl methacrylate onto silk fibers
Authors: Samal R. K. , Suryanarayana G. V. , Dash P. C. , Panda G. , Das D. P. , Nayak M. C. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate onto silk fibers was investigated in aqueous solution using Mn3+ acetyl acetonate [Mn(acac)3] as initiator. The rate of grafting was determined by varying monomer, acidity of medium, temperature, and reaction medium. The graft yield increases significantly with increase of [Mn(acac)3] concentration up to 0.01M, and with further increase of [Mn(acac)3] the graft yield decreases. The effect of the increase of monomer concentration brings about a significant enhancement in the graft yield, and with further increase the graft yield decreases. The rate of reaction is temperature dependent; with increasing temperature, the graft yield increases. Among the solvent composition studied, a water/solvent mixture containing 10% of the solvent seems to constitute the most favorable medium for grafting, and, with further increase of solvent composition, the graft yield decreases. The effect of some inorganic salts, organic solvents, and complexing agents has been investigated.
Rubber‐modified polystyrene impact as a function of flame‐retardant additive solubilization
Authors: Sprenkle W. E. , Southern J. H. 
Published: April 2003

AbstractThermal optical analysis (TOA) is employed to study the solubilization of organic flame‐retardant additives in high‐impact polystyrene. The TOA approach (1) indicates the minimum temperature at which solubilization will occur; (2) yields information on how the composite will process; and (3) can be used to generate an equation that describes the kinetics of solubilization. Multiaxial impact strength increases proportionally as additive solubilization increases. The fundamental significance of the kinetic equation is discussed. Other applications of TOA are suggested.