bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and polymerization of some iodine‐containing monomers for biomedical applications
Authors: Jayakrishnan A. , Thanoo B. Chithambara 
Published: April 2003

AbstractTriiodophenol and iothalamic acid (5‐acetamido‐2,4,6‐triio‐N‐methyl isophthalamic acid) were converted to their acrylic derivatives by esterfication with methacryloyl chloride and 2‐hydroxyethyl methacrylate (HEMA), respectively. The monomers due to presence of heavy iodine atoms were expected to be radiopaque in nature. The monomers were characterized using TLC, IR, and 1H‐NMR spectroscopy. Both monomers were highly resistant to homopolymerization and copolymerization with other acrylic monomers such as methyl methacrylate (MMA) or HEMA by initiators such as 2,2′‐azobis isobutyronitriie (AIBN) or benzoyl peroxide (BPO) yielding only polymers of low molecular weight. The polymers obtained were charactrized by gel permeation chromatography (GPC) and differential thermal analysis (DTA). The resistance to polymerization is presumably due to the presence of bulky iodine atoms in the monomers sterically hindering the propagation step. The decomposition temperatures of the homopolymers and copolymers were close to 300°. Copolymers of HEMA with both radiopaque monomers incorporated to the extent of 25 wt % in the feed, however, produced polymers with good radiopacity. Copolymers with HEMA were also prepared in the form of microspheres by a solvent evaporation method with the aim of using them as particles in therapeutic embolization. While the polymer based on triiodophenol was found to cause extensive blood haemolysis in in vitro tests, polymer based on iothalamic acid was found to be nonhemolytic in character suggesting that copolymers based on iothalamic acid would be suitable for implantation in the living tissue.
Longitudinal variation in the stress–strain properties of wool fibers
Authors: Dunn Linda A. , Weatherall Ian L. 
Published: April 2003

AbstractIn order to obtain information on possible end‐to‐end differences in the physical properties of wool caused by weathering of the more exposed portions, a comparison has been made of the stress–strain characteristics of the tip and root halves of fibers taken from the midback region of sheep reared outdoors over a 6‐month summer to winter period. The results were further compared with the tip and root halves of fibers taken from animals reared indoors under conditions of essentially continuous darkness. When 11 features of the stress–strain curves were compared, it was found that for the outdoor wools the tip halves had lower initial moduli, higher yield strains, and lower yield moduli than the root halves. In contrast, the dark grown wools showed no end‐to‐end differences. The greater ease of extension of the tip halves of outdoor wools may be attributed to light‐induced diminution in the levels of crosslinking within the keratin structure. The results show that normal environmental influences caused end‐to‐end differences and that longitudinal variations in physical properties may be a typical characteristic of all field grown wools at the time of harvesting.
Mechanisms of antioxidant action: Photoantioxidant activity of polymer‐bound hindered amines. II. Bis acrylates
Authors: Al‐Malaika S. , Ibrahim A. Q. , Rao M. J. , Scott G. 
Published: April 2003

Abstract1‐Acryloyl‐4‐acryloyloxy‐2,2,6,6‐tetramethylpiperidine (AATP) has been covalently attached to polypropylene under conditions of reactive processing to give substantial concentrations of essentially 100% grafted antioxidant (AATP‐B). Solution of the concentrates showed that at high concentration of grafted antioxidant some homopolymerized AATP was present and the polymer undergoes transient cross‐linking during processing. Concentrates of bound AATP (AATB‐B) when used as conventional additives for polypropylene are very effective photoantioxidants due to conversion to the related polymer‐bound nitroxyl radicals by photosensitized oxidation. A typical commercial hindered phenol, Irganox 1076, when used at low concentration in combination with ‐B also acts as a photosensitizer for nitroxyl formation. Unlike low molar mass‐hindered piperidinoxyl, polymer‐bound nitroxyls are effective thermal antioxidants that synergize very effectively with low concentrations of Irganox 1076.
The curing mechanism and properties of bismaleimide–biscyanamide resin
Authors: Suzuki Masao , Nagai Akira , Suzuki Masahiro , Takahashi Akio 
Published: April 2003

AbstractThermoset networks consisting of N, N‐bismaleimidediphenylmethane (BMI) and bis [4‐(4‐cyanamide‐3‐methylphenyl)] methane (BCMM) were investigated with the aim of correlating macroscopic behavior and structure as network composition was varied. The glass transition temperatures of these cured resins obtained from the dynamic mechanical data and thermal expansion data had a distinct minimum at the 50/50 molar ratio of BMI/BCMM. Also, at this molar ratio, the decomposition temperature at a 5% weight loss in helium atmosphere for cured resins was the lowest. These results provided a rough idea of the thermoset network structure.
Peroxide‐initiated grafting of acrylamide on to polyethylene surfaces
Authors: Kildal K. , Olafsen K. , Stori A. 
Published: April 2003

AbstractAcrylamide has been grafted onto the surface of a polyethlene film with the aid of a peroxide initiator (tert‐butyl peroxyneodecanoate). The peroxide was first swollen into the film from cyclohexane solution; the film was then dried under reduced pressure at room temperature. Excess initiator, adsorbed on the surface, was washed off with acetone. The grafting reaction was carried out by placing the film in a boiling solution of the monomer in water. After grafting, the film was extracted with water to remove monomers and homopolymer. The grafted films were characterized by infrared spectroscopy, X‐ray photoelectron spectroscopy (XPS), gravimetric measurements, and contact angle measurements. The graft yield was found to increase with reaction time up to about 5–15 min and thereafter level off. The presence of air was found to retard the grafting reaction. Increase in monomer concentration gave an almost continuous increase in graft yield, but high concentrations were not necessary to cover the surface of the film with polyacrylamide. This grafting has been found to function, but the process requires further development to reduce the total grafting time before it can be used commercially.
Stress relaxation studies on wool fibers
Authors: Gupta V. B. , Rao D. Rama 
Published: April 2003

AbstractStress relaxation studies were made on single fibers of Lincoln, Chokla, and Merino wool in water in the temperature range 2–80°C. Differences in the viscoelasticity of the three wool types were related to differences in their fine structure and morphology. Of the three wools, Merino fibers have the lowest crystalline content and the poorest fibril orientation and packing. This results in greater viscoelastic effects in this wool. Stress relaxation studies have been made in the Hookean, yield, and postyield regions, and the molecular mechanisms of stress relaxation have been discussed.
The color of absorbing scattering fibers having skin‐core structure
Authors: Sokkar T. Z. N. , Kabeel M. A. , Ramadan W. A. 
Published: April 2003

AbstractA treatment of the color of fabrics is proposed that is an extension of the Allen and Goldfinger approach to the prediction of the color of absorbing scattering substrates. Here, a model of isotropic cylindrical fibers of a skin–core structure in a parallel array is assumed. Using the proposed model, the spectral reflectance curves of ring dye and uniform dye samples are calculated. Their tristimulas values and the color difference between them are calculated to study the effect of ring distribution of dye in the fiber on color of fabric. Refractive indices of undyed and dyed polyester fibers are measured using the Pluta polarizing interference microscope. Illustration are given by microinterferograms.
Dimensionless groups for the sorption of dye and other ions by polymers. II. Hydrochloric acid, C.I. acid blue 25, and polyamides with an excess of basic groups
Authors: McGregor Ralph , Iijima Toshiro 
Published: April 2003

AbstractThe equations of a generalized Donnan model have been used in dimensionless form to describe and analyze the sorption of hydrochloric acid and of C.I. Acid Blue 25 by polyamide fibers containing an excess of basic groups. The method is applicable to a wide variety of ionic sorption systems, and removes some of the restrictions of earlier treatments of the problem. Acid–base reactions, ion exchange processes, electrolyte sorption, and both ion binding and zwitterion formation have been considered.
Impact toughening of polypropylene by ethylene vinyl acetate copolymer
Authors: Gupta A. K. , Ratnam B. K. , Srinivasan K. R. 
Published: April 2003

AbstractIn this article we studied the potential of ethylene vinyl acetate copolymer (EVA) as an impact modifier for isotactic polypropylene (PP). PP/EVA blend in the range 0–40 wt % EVA content is studied by using three grades of EVA containing 9, 12, and 19 wt % VA. Izod impact strength measurements were made at temperatures ranging from liquid nitrogen temperature to 60°C to explore the impact‐toughening effect as a function of blending ratio both at low and above ambient temperatures. The results are compared with various reported blends of PP with other elastomers. Morphological studies through scanning electron microscopy on etched impact‐fractured surfaces are carried out and a correlation of morphology and impact properties at various blending ratios is presented. Finally, a mathematical analysis of the data is performed in terms of second‐degree polynomial to express impact strength as a simultaneous function of two variables, and an equation is proposed that shows the best fit with the experimental data. Relevant contour diagrams, based on the proposed equation, for optimization of properties are also presented.
Thermal properties of wool‐g‐poly(methyl methacrylate) copolymers
Authors: Elangovan V. J. , Saccubai S. 
Published: April 2003

AbstractThe thermal properties of wool fibers can be improved by graft copolymerization with vinyl monomers. Using TGA, DTG, and DSC techniques, the thermal behavior of methyl methacrylate grafted wool fibers was studied. Graft copolymerization was carried out using KBrO3 and substrates such as Fe(II), Co(II), cysteine, cystine, tyrosine, and urea. Of all the systems studied the grafted fibers which involve Fe(II), Co(II), and cystine gave improvement in the thermal stability.
Improvements of the physical properties of fibroin membranes with sodium alginate
Authors: Liang Chuan Xin , Hirabayashi Kiyoshi 
Published: April 2003

AbstractThe effects of sodium alginate on the physical properties of fibroin membranes, such as rupture elongation, rupture strength, water absorption, and thermal properties, were investigated. The experimental results showed the β‐form crystal and β‐form molecular conformation increased due to the increase of intermolecular hydrogen bonds, such as CO‐‐‐HN and CO‐‐‐HO. The kind of intermolecular interaction and β‐form molecular conformation of polymer blends were clarified by 13C–NMR and infrared spectroscopy. The increase in β‐form crystal was examined by X‐ray analysis. Further, membranes were characterized by thermogravimetric analysis (TGA) and by determining their water contents and tensile properties.
Mechanical stability of trimethylolpropane trimethacrylate‐based polymers
Authors: Schmid Andrea , Walenius Maria , Flodin Per 
Published: April 2003

AbstractTrimethylolpropane trimethacrylate (TRIM) was homopolymerized and copolymerized with methyl methacrylate (MMA), glycidyl methacrylate (GMA), and acrylamide (AA), respectively, in various solvents and at various temperatures. For comparison, poly(styrene‐co‐divinyl benzene) [poly(S‐co‐DVB)] gels were selected. The mechanical stability was measured by compression of the swollen gels. The porogen served as swelling agent. The compression moduli increased with increasing TRIM concentration in the polymerization. The compression moduli of poly(TRIM) could be increased by copolymerization with low concentrations of comonomer. Low polymerization temperature decreased the mechanical strength of poly(TRIM). A good solvent increased the compression modulus. TRIM‐based gels were at least as mechanically stable as were poly(S‐co‐DVB) gels.
New approach for the estimation of kinetic parameters in emulsion polymerization systems. II. Homopolymerization under conditions where n̄ > 0.5
Authors: Barandiaran María J. , Adams Mary E. , Cal José C. De La , Sudol E. David , Asua José M. 
Published: April 2003

AbstractA new approach for the estimation of kinetic parameters in emulsion polymerization systems in which the average number of radicals per particle exceeds 0.5 is presented. The approach uses the time evolution of the conversion in chemically initiated systems and is based on a model that includes fundamental parameters such as the propagation rate constant, kp, the termination rate constant in the polymer particles, kt, the rate coefficient for initiator decomposition, kI, and the entry, ka, and exit, kd, rate coefficients. It was found that kp, kt, kI, ka, and, under some circumstances, kd can be accurately estimated provided that termination in the aqueous phase is significant. When the extent of the aqueous phase termination is negligible, only kp, kt, and kI can be estimated. The effect of both the experimental noise level and the run‐to‐run irreproducibility on the accuracy of the estimates was studied. In addition, it was found that significant inaccuracies resulted from the poor determination of the exact time when polymerization begins. A method to circumvent this problem was proposed.
Influence of polymer characteristics and melt‐spinning conditions on the production of fine denier poly(ethylene terephtalate) fibers. Part II. Melt spinning dynamics
Authors: Kiang Chang T. , Cuculo John A. 
Published: April 2003

AbstractThe effect of poly(ethylene terephtalate) (PET) polymers with different rheological properties as well as the effect of different spinning conditions on the minimum attainable takeup denier were determined. The spinning conditions were modified by the use of heating devices, insulation plate, and convergence guides tested in the range of take‐up speeds from 2000 to 6000 m/min. It is postulated that the important parameter in the production of fine denier PET fiber is the spinline tension level, which must be kept low in order to obtain finer denier fibers. The increase of take‐up velocity and the threadline length increase the spinline stress level, and therefore the minimum denier attainable increases. The effect of the apparent elongational viscosity of the polymer and the threadline cooling profile can be thought as affecting the draw‐down tension and therefore the minimum take‐up denier. Higher apparent elongational viscosity level or faster cooling generates higher spinline tension resulting in higher minimum denier. The effects of the apparent elongational viscosity is more significant at a speed of 5000 m/min. This is in part due to the already very small denier obtained at speeds up to 4000 m/min, where the conditions of uniformity of polymer flow seem to be more important.
Studies of the solid‐state thermal degradation of PVC. I. Autocatalysis by hydrogen chloride
Authors: Patel K. , Velazquez A. , Calderon H. S. , Brown G. R. 
Published: April 2003

AbstractThe thermal degradation of virgin and HCI‐treated PVC in powder form, as well as of PVC films of different thicknesses, has been studied as a function of time and temperature. The rate of dehydrochlorination was determined conductimetrically and from the polyene sequence distributions as obtained by UV spectroscopy. Increases in the rate of dehydrochlorination, ranging between 30 and 45%, were observed at all temperatures for the samples pretreated with HCI, while the corresponding activation energies were found to be lower by about 20%. For the PVC films, the rate increased with thickness, i.e., with longer residence time of evolved HCI within the sample. The results offer insight regarding the autocatalytic role of evolved HCI.
An FTIR–ATR investigation of in vivo poly(ether urethane) degradation
Authors: Wu Y. , Sellitti C. , Anderson J. M. , Hiltner A. , Lodoen G. A. , Payet C. R. 
Published: April 2003

AbstractSurface degradation of implanted poly(ether urethane)s was studied quantitatively with a micro‐ATR–FTIR technique. Substantial degradation was observed particularly in the soft segment at the α‐carbon adjacent to the ether linkage. The degradation caused changes in the concentration profiles of the soft‐segment groups in the depth direction, and the affected depth was up to 10 microns after implantation for 10 weeks. Inhibition of degradation by antioxidants indicated the oxidative nature of degradation. An in vivo poly(ether urethane) degradation mechanism was proposed.
Determination of the kinetic parameters for the polymerization of a polyurethane using an improved method of differential scanning calorimetry
Authors: Hernández‐Sánchez F. , Vera‐Graziano R. 
Published: April 2003

AbstractThe kinetic parameters for the polymerization reactions of two polyurethane systems were determined by using an improved method of differential scanning calorymetry (DSC). The calculated activation energy, reaction order, and Arrhenius prefactor show good correlation with the experimental results. The method used here shows several improvements as respects to other DSC methods: the three kinetic parameters can be calculated directly; it is more accurate than other DSC methods; and it requires only one heating rate, during the calorimetric experiments, to determine the activation energy.
Study on PVA hydrogel crosslinked by epichlorohydrin
Authors: Bo Jiang 
Published: April 2003

AbstractPoly(vinyl alcohol) hydrogel was prepared by using epichlorohydrin as a crosslinking agent. The molecular weight between crosslinks was calculated. The swelling behavior, as well as mechanical properties, of the hydrogels were examined by weighing and tensile testing, respectively. Values of equilibrium water content of more than 95% were reached while Young's modulus and tensile strength of the hydrogels were about 105 dyn/cm2. Crystallization was introduced by drying the hydrogels at 90°C. The dried hydrogel samples were used for swelling kinetic study, then reequilibrated with water and subjected again to tensile testing. Due to the formation of microcrystalline domains in the PVA hydrogel network after annealing, hydrogels with greatly enhanced Young's modulus, tensile strength, and elongation at break were obtained and their equilibrium water content values remained still high, i.e., 87 and 93%. © 1992 John Wiley & Sons, Inc.
Transesterification reaction of poly(ethylene‐co‐vinyl acetate) with alcohols: A kinetic study in solution and in the bulk
Authors: Hu G. H. , Lindt J. T. , Lambla M. 
Published: April 2003

AbstractThe chemical kinetics of the transesterification reaction of poly(ethylene‐co‐vinyl acetate) (EVA) with aliphatic alcohols were investigated, both in solution and in bulk, in the presence of dibutyl tin dilaurate (DBTDL) as the catalyst. A Fourier Transform infrared spectrometer (FTIR) was utilized for the measurement of the extent of the reaction. Experimental results showed that the reaction carried out in solution and in the bulk follows the same mechanism, namely, a reversible second order reaction of which the equilibrium only slightly increases with temperature. Additionally, the overall forward and reverse rate constants are proportional to the square root of the concentration of the catalyst. This study has also revealed that the intrinsic rate constants in solution and in the bulk are the same, regardless of the differences in the physical conditions encountered in the bulk and solution media, in particular, the reactant concentrations and viscosity of the reacting mixture. The effects of mechanical mixing are unimportant, since the reaction rate is relatively slow as compared with the rate of diffusion.
Annealing of commercial block polypropylene. II. Behavior of poly(ethylene‐co‐propylene) component
Authors: Ito Jun‐Ichi , Mitani Katsuo , Mizutani Yukio 
Published: April 2003

AbstractMoldings of ethylene–propylene block copolymer (block PP) are improved by annealing in their tensile impact strength (TIS) and brittle temperature (Tb). To elucidate the mechanism, the role of the poly(ethylene‐co‐propylene) (PEP) component was studied, and the component extracted with n‐heptane from annealed test pieces was subjected to characterization by a fractionation technique. It is found that recrystallization takes place by annealing in the PP matrix and results in segregation of atactic PP and high molecular weight amorphous PEP from the crystal region to the amorphous region. Furthermore, crystalline PEP also undergoes recrystallization by annealing, increasing the miscibility in the interface of PP and PEP. These phenomena in the solid phase are discussed in connection with the annealing effect related to impact strength. © 1992 John Wiley & Sons, Inc.
Syntheses of polyethylene glycol (PEG) with different functional groups at each end. I. Preparation of monotrityl PEG using polyvinyl alcohol (PVA) matrix
Authors: Huang Junlian 
Published: April 2003

AbstractThe syntheses and separation of monotrityl PEGs with molecular weights in the range of 400–6000 were successful using PVA as matrix. The yield of monotrityl PEG is strongly dependent on the initial mole ratio of PEG—trityl chloride. It is observed that satisfactory results can only be obtained in the range of 1 : 1.7 to 1 : 2.4 (mole number of PEG/mole number of trityl chloride). The effect of reaction conditions on monosubstitution is discussed. © 1992 John Wiley & Sons, Inc.
Grafting of acrylic acid onto corona‐treated polyethylene surfaces
Authors: Olafsen K. , Stori A. , Tellefsen D. A. 
Published: April 2003

AbstractPeroxides formed on the surface by corona treatment of low‐density polyethylene film can be used to initiate grafting of polar vinyl monomers such as acrylic acid. Different types of peroxides are probably formed on the surface, but at least hydroperoxides could be detected by XPS analysis. The grafting reaction was carried out directly after corona treatment, by placing the corona‐treated film above a solution of acrylic acid heated to 100°C. The grafting reaction takes place in a vapor phase of the monomer. After extracting the reacted films with hot methanol and drying, surface analysis by XPS, IR, and contact angle measurements were carried out. Effect of degree of corona treatment and reaction time have been studied. The conclusion from this work is that acrylic acid in vapor phase can successfully be grafted onto corona‐treated polyethylene film by this method. © 1992 John Wiley & Sons, Inc.
Effect of cardinyl acrylate on thermal behavior of methyl methacrylate copolymers
Authors: Agarwal Seema , Choudhary V. , Varma I. K. 
Published: April 2003

AbstractCardinyl acrylate (CA), prepared by the reaction of acryloyl chloride and cardinol, was copolymerized with methyl methacrylate (MMA) in bulk at 80°C using 2% benzoyl peroxide as an initiator. The copolymer composition was determined by 1H‐NMR spectroscopy. Three copolymer samples containing 0.0048–0.0838 mol fraction of cardinyl acrylate were obtained. A significant improvement in the thermal stability of MMA was observed by incorporating 0.0048–0.0838 mol fraction of CA in the backbone. The activation energy for decomposition in the temperature range 350–480°C for copolymers was higher than PMMA. © 1992 John Wiley & Sons, Inc.