bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of resin components on the degradation of guayule rubber
Authors: Bhowmick A. K. , Rampalli S. , McIntyre D. 
Published: April 2003

AbstractAll natural rubbers are likely to contain some long chain fatty acids or their esters. The individual effect of the four C18 fatty acids (stearic, oleic, linoleic, and linolenic acid) present in the guayule resin on the degradation of guayule rubber has been investigated concurrently by stress–relaxation of radiation cured rubber networks and by gel permeation chromatography studies on the raw rubber in the temperature zone 70–125°C. C18 unsaturated fatty acids enhance the degradation of rubber several fold. The rate of degradation follows the order: rubber ≤ rubber + stearic acid < rubber + oleic acid < rubber + linoleic acid < rubber + linolenic acid. The thermal degradation is slower than the thermooxidative. The rate of degradation monotonically increased with the number of conjugated double bonds and is first order with respect to acid concentration. The activation energy for the chain scission for both thermal and thermooxidative degradation has been found to be 95 ± 10 kJ/mol. The mechanism of degradation of guayule rubber in the presence of fatty acids is discussed.
Surface modification of cellulose fibers. I. Spectroscopic characterization of surface‐modified cellulose fibers and their copolymerization with styrene
Authors: Zadorecki Pawel , Flodin Per 
Published: April 2003

AbstractTwo coupling agents based on trichloro‐s‐triazine with different terminal unsaturated groups were synthesized in order to improve the bonding between cellulose fibers and an unsaturated polyester matrix. The products of the reactions between hydroxyl groups of cellulose and reactive species of coupling agents were analysed by Fourier‐transform infrared spectroscopy (FTIR) and by elemental microanalyses. ESCA was used for surface characterization of treated fibers. The coupling agents were found to be concentrated on the fiber surface. Polymerization of styrene was carried out in the presence of treated fibers. That the unsaturated groups of the treated fibers were able to copolymrize with styrene was shown by FTIR. Further evidence of the presence of grafted polystyrene on the surfaces of the cellulose fibers was provided by ESCA measurements.
Stress–relaxation and stress–strain behavior of poly(ethylene‐co‐vinylacetate) at varying crosslink density
Authors: Fedors R. F. , Chung S. Y. , Hong S. D. 
Published: April 2003

AbstractThe stress–relaxation modulus of an unfilled ethylene vinyl acetate polymer at three different degrees of crosslinking was measured at 15 temperatures over a temperature span of about 160°C. At each temperature, the time response was measured for at least 3 decades of time. From these data it was possible to construct a master curve for each degree of crosslinking. The time–temperature shift factors, aT, were found to be related to temperature by the relation log aT = −A(T–273), where the parameter A has an average value of 0.234 for the three materials.
Graft copolymerization onto rubber. VII. Graft copolymerization of methyl methacrylate onto rubber using potassium peroxydisulfate catalyzed by silver ion
Authors: Lenka Subasini , Nayak Padma L. , Das Anil P. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate onto natural rubber (NR) was carried out varying the concentration of monomer, initiator, thiourea, and silver nitrate over a wide range. The grafting reaction was temperature‐dependent. From the Arrhenius plot, the overall energy of activation was computed. A suitable reaction scheme and rate expression for the rate of polymerization was suggested.
Aromatic ionomer membranes: II. Evaluation as separators for advanced alkaline water electrolyzers
Authors: Steck A. E. , Yeager H. L. , Harris F. W. , Gupta R. K. , Eisenberg A. , Besso E. 
Published: April 2003

AbstractThe sorption and transport properties of newly developed aromatic carboxylate polymers have been investigated in the context of their application as membrane separators for water electrolyzers. Conductance measurements of aromatic carboxylates of various equivalent weights have been performed as a function of current density, temperature, and electrolyte environment. Results have been compared with those for Nafion 117. The sorption results in dilute and concentrated solution show large water and electrolyte uptake for the aromatic carboxylate films. Furthermore, relatively large sodium ion self‐diffusion coefficients have been found in both dilute and concentrated solution environments. The results of these measurements are characteristic of microporous films. The de conductance behavior of the aromatic carboxylate ionomers is quite different from that found for nonporous 1150 equivalent weight Nafion membranes. This difference is caused primarily by the microporous structure of the aromatic carboxylates, which results in large membrane specific conductances.
Radiation‐induced grafting of methacrylic acid onto polyurethane in the presence of solvents
Authors: Omichi H. , Stannett V. T. 
Published: April 2003

AbstractThe radiation‐induced grafting of methacrylic acid onto polyurethane has been carried out in the presence of solvents. The swelling of polyurethane was highest when the solubility parameter of the monomer solution was 11.0. The molecular weight of polyurethane did not change with the irradiation dose up to 30 Mrad in the absence of solvent. The irradiation in the presence of solvent, on the other hand, decreased the molecular weight. The grafting yield in CCl4, benzene, and n‐hexane decreased monotonously with the decrease in monomer concentration. The large decrease of the grafting yield in CCl4 was proved to be due to the high possibility of chain transfer to CCl4. When such solvents as water, methanol, and DMF were used, on the other hand, a maximum grafting yield was obtained when the monomer concentration was ca. 75%. The hydrogen bonding among polyurethane, methacrylic acid, and solvent was found to affect both the swelling and the grafting yield.
Dynamic mechanical properties of polymer–leather composites
Authors: Kronick Paul L. , Buechler Peter , Scholnick Frank , Artymyshyn Bohdan 
Published: April 2003

AbstractThe effects of polymer impregnation, moisture, and lubricant oils on the complex modulus of the grain layer of leather have been studied. The impregnated materials were prepared by introducing a mixture of polyurethane oligomer and vinyl monomers into the grain layer and polymerizing by electron‐beam irradiation. Synergism was observed in the interaction of the components of the system and analyzed in terms of the adhesion of the polymer to the collagen fibers.
Diffusion of toluene sulfonic acid in nylon film
Authors: Wirbrant Anita , Sundelöf Lars‐Olof 
Published: April 2003

AbstractThe permeation of p‐toluene sulfonic acid through nylon 66 film has been studied at different concentrations of sulfonic acid. The ordinary diffusion coefficient in the membrane was found to increase with increasing concentration in nylon, moderately at low concentration but very rapidly when approaching the Langmuir saturation concentration.
Further studies on polyamides from bisacid a2
Authors: Maguire J. J. , Lenk R. S. 
Published: April 2003

AbstractEarlier work on the low temperature solution polyamidation of bisacid A2 has raised a number of structural problems. Work carried out more recently showed that the problem of apparent nonisostoichiometry could be reasonably satisfactorily explained. The present paper reports the synthesis and investigates the properties of a further series of polyamides based upon Bisacid A2. More importantly, however, a detailed characterization and evaluation of the new polymers with respect to their structures is presented. This enabled us to compare the various structures in the light of the experimental evidence provided by a number of analytical and spectroscopic techniques, solution behavior, molecular weight, and thermal, morphological, and mechanical properties. Some work was also done on the effect of incorporating a small amount of a trifunctional monomer into the polyamide system.
Some aspects of autoignition delays and flammability limits of polyurethane based on diphenyl methane diisocyanate (MDI) and propoxylated trimethylol propane
Authors: Gaboriaud F. , Vantelon J. P. , Breillat C. 
Published: April 2003

AbstractThe main purpose of this work is a better understanding of the physicochemical phenomena involved during an unpiloted ignition. We intend to characterize the step corresponding to the degradation of the material, the production of combustible gases, and their combustion with the surrounding oxidizing gas, leading to the flame. The degradation gases which are essentially alkanes, alkenes, and aldehydes undergo oxidation by degenerate chain branching mechanism. The initiating chain propagates very quickly and creates intermediate species of increased stability which initiate new active centers leading to secondary chains. Then, ignition can occur after a relatively large induction period. We suggest that this period may be defined as the time to reach a critical rate of production of the intermediate species. A study of the active center distribution near the surface as a function of time and of the distance to the surface allows us to explain the experimental variation of ignition delays vs. oxidant pressure. The ignition limits of this polyurethane, i.e., temperature–pressure curves in air and in oxygen, have also been determined. It has been possible to correlate pressure and temperature and to specify the influence of nitrogen on the ignition process.
Reduction and hydroboration with borane and haloborane complexes of poly(propylene sulfide) grafted on crosslinked polystyrene
Authors: Domb Abraham , Avny Yair 
Published: April 2003

AbstractPreparation of borane and haloborane complexes of poly(propylene sulfide) grafted on crosslinked polystyrene was investigated. Graft polymer–borane was prepared by reaction of graft polymer with B2H6 and BH3–THF. Graft polymer–haloborane was prepared by reaction with haloborane–tetrahydrofuran and by reaction of borane‐bound graft polymer with halogen. Graft polymers with high borane (2.44 mmol/g) and haloborane (163 mmol/g) content were reached. The use of these graft polymers as polymeric reagents for reduction of carbonyl compounds and hydroboration was investigated. Aldehydes, ketones, carboxylic acids, and esters were reduced in high yields to the corresponding alcohols by borane‐bound graft polymer. The graft polymer showed good chemoselectivity in competative reduction of cyclohexanone and other ketones and aldehydes, as well as in competative reduction of acetophenone and benzaldehyde. Reactivity of graft and homopolymer–borane was similar to that of borane–methyl sulfide. Hydroboration of alkenes with these graft polymers, followed by alkaline oxidation, led to the formation of the corresponding alcohols in high yields. Hydroboration was highly regioselective. Stability of the graft polymer–borane and recycling of that graft polymer were investigated. Cleavage of the poly(propylene sulfide) by the borane bound polymer took place to some extent. At 0°C no borane loss was found over a 5‐week period. When recycled, 85% of the original borane content could be regenerated at the end of the fourth cycle.
Control of free‐radical emulsion polymerization of methyl methacrylate by oxygen injection. II. Experimental study
Authors: Louie Brian M. , Franaszek Thomas , Pho Tina , Chiu Wen Yen , Soong David S. 
Published: April 2003

AbstractOxygen injection has been proposed and experimentally demonstrated as an effective control measure for limiting the rate of heat release and altering the rate of polymerization in emulsion processes. A detailed mathematical model has been previously developed to describe the system behavior with and without oxygen injection. A simple lab scale apparatus was constructed and run extensively. Only trace quantities of oxygen are needed to inhibit the reaction completely. The facile response makes this method attractive for fast temperature control. However, because of the rapid penetration of dissolved oxygen into the polymer particles, growing radical chains are terminated prematurely, lowering product molecular weights. To minimize this detrimental effect, pulsed oxygen control is used and extensive experimental work was performed to determine the effects of controller set points on molecular weight. Moderate oxygen flows and moderate set point temperatures are found to give the optimal response without significant lowering of the final molecular weight. Injected quantities agree well with the order‐of‐magnitude sparging calculations needed to completely stop initiation. However, complete agreement between model simulations and experimental results was not reached due to an unmeasured loss of monomer from the reactor. Chain transfer to monomer is found to be important in modeling the polymer molecular weight. It has, however, a negligible effect on the reaction rate.
The chemistry of a polyamide–epichlorohydrin resin (hercosett 125) used to shrink‐resist wool
Authors: Guise G. B. , Smith G. C. 
Published: April 2003

AbstractA polyamide–epichlorohydrin resin used to shrink‐resist wool [Hercosett 125 (Hercules Inc.)] was separated by ultrafiltration into fractions A, B, and C (in the approximate proportions 60, 40, and 2 by weight), which correspond to the three peaks in size exclusion chromatograms (SEC). Viscosity, spectra, and SEC results as well as results of experiments on the reaction of the parent polyamino–polyamide (PAA) with epichlorohydrin indicated that fraction A was high‐molecular‐weight crosslinked material whereas fraction B was essentially uncrosslinked. Fraction C was minor impurity, possibly a mixture containing a triazine, and it was also found in the PAA from which the original resin was prepared. High‐resolution proton NMR spectra of the Hercosett 125 indicated that chlorohydrin or epoxy groups were absent, and thus confirmed an earlier 13C‐NMR study that only azetidinium reactive groups were present. Two reactions are believed to occur in Hercosett 125 on storage: hydrolysis of azetidinium to dihydroxypropyl groups and hydrolysis of backbone amides. The small differences in the properties of wool treated with either A or B fractions, and those of wool treated with unfractionated Hercosett 125, were related to the extent of crosslinking before and after curing. As the extent of crosslinking increased, the amount of staining by an anionic dye decreased, and the shrink resistance improved slightly.
Investigation of the action of flame retardants in cellulose. I. Investigation of the flame retardant action of 2,2′‐oxybis(5,5‐dimethyl‐1,3,2‐dioxaphosphorinane‐2,2′‐disulfide) in cellulose
Authors: Choudhary Marjeet S. , Fink Johannes K. , Lederer Klaus 
Published: April 2003

AbstractPyrolysis experiments were performed in high vacuum and under reduced air pressure (100 Pa). The volatile products of pure cellulose and cellulose containing various amounts of flame retardant 2,2′‐oxybis (5,5‐dimethyl‐1,3,2‐dioxaphosphorinane‐2,2′‐disulfide), i.e., Sandoflam 5060 of Sandoz AG, were studied by means of gas chromatography in combination with mass spectroscopy. The volatile products were characterized with infrared spectroscopy. The studied revealed that the incorporation of the flame retardant enhanced the water release and shifted the onset of this reaction to lower temperature. On the basis of these findings an explanation for the mechanism of flame retardancy in generated cellulose fibers modified with this particular flame retardant is attempted. From experiments with different residual air pressure the influence of oxygen on the primary processes of the pyrolytic degradation of cellulose is being discussed.
Structure‐property relationships in thermoplastic elastomers III. Segmented polyacetal‐polyurethanes
Authors: Xu Baobei , Khanna D. N. , Lillya C. Peter , Chien James C. W. 
Published: April 2003

AbstractDihydroxy‐terminated polyacetals had been synthesized from aldehydes and glycols and used as soft segments to obtain segmented polyurethane block copolymers. For soft segment ≥ 1700Mn, the Tg ranges from–48 to −58°C and is insensitive to the structures of diisocyanate and chain extender. The Tg of PacPU with 1350 Mn polyacetals is raised to −38°C, and none was observed for shorter polyacetal chains. The copolymers can be synthesized to have a broad range of mechanical properties, such as modulus from 0.5 to 130 MPa, stress at break from 0.7 to 21 MPa, and elongation at break from 66 to 1300% through the variation of the constituents and composition. The rheologic properties are only slightly dependent on temperature for symmetrical diisocyanates but quite temperature sensitive with asymmetric diisocyanate copolymers. The polyacetals are selected to build in acid‐catalyzed thermal decomposition of the thermoplastic elastomers. The extreme acid sensitivity of the polyacetal block is buffered in the coplymers.
Graft copolymerization of methyl methacrylate (MMA) on hydrazine treated oxycellulose in limited aqueous system
Authors: Ghosh Premamoy , Dalal Jagadish Chandra 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate (MMA) on oxycellulose modified with hydrazine treatment was studied in a limited aqueous system using K2S2O2 as the initiator. Hydrazine modified oxycellulose prepared from oxycellulose corresponding to low degrees of oxidation (copper nos. 2–6) produced the best grafting effects. Grafting parameters under different sets of conditions were studied and compared and the mechanism of graft copolymerization discussed.
Oxidative susceptibility of partially carboxymethylated cotton to gamma radiation
Authors: Hebeish A. , Zahran A. H. , El‐Naggar A. M. K. 
Published: April 2003

AbstractPartially carboxymethylated cotton with a DS of about 0.05–0.15 retains its original fibrous nature and exhibits a number of potentially valuable properties, such as a crisp hand with a slightly starched feel, increased moisture regain, water absorbancy, water permeability, changed dyeing characteristics, increased resistance to soiling from aqueous dispersions, and greater ease of soil removal.5–8 Furthermore, detailed studies have been reported on the behavior of partially carboxymethylated cotton toward oxidation and hydrolysis,9 vinyl graft polymerization,10 transfer printing,11,12 cross‐linking,13 and thermal treatments.14
Preparation of high‐modulus and high‐strength poly(ethylene terephthalate) film by zone‐annealing method
Authors: Kunugi Toshio , Ichinose Chie , Suzuki Akihiro 
Published: April 2003

AbstractThe zone‐annealing method was attempted to prepare high‐modulus and high‐strength poly(ethylene terephthalate) (PET) film. The film having Young′s modulus of 14.5 × 1010 dyn/cm2 and a tensile strength of 86.9 kg/mm2 in the drawing direction was obtained. These values correspond to four times those of a biaxial‐stretched PET film available commercially. The dyanmic viscoelastic properties also were measured. The dynamic storage modulus was 15.4 × 1010 dyn/cm2 at room temperature, and a high value of 3.6 × 1010 dyn/cm2 even at 200°C. The latter value is slightly higher than the room temperature modulus of the commercially available film. From the intensity and temperature position of α‐dispersion E″ peak, it was suggested that the amorphous chains in the zone‐annealed film was densely packed in a highly oriented state. Furthermore, the crystallinity, orientation, especially double orientation, and molecular chain conformation of the films in the zone‐annealing process are discussed in the present paper.
Swelling properties of copolymeric hydrogels prepared by gamma irradiation
Authors: Huglin Malcolm B. , Zakaria Mat B. 
Published: April 2003

AbstractCrosslinked xerogels in the form of rods have been prepared to > 99.9% conversion by the γ‐ray initiated copolymerization in vacuo ob n‐butyl acrylate (BA) with N‐vinyl‐2‐pyrrolidone (VP) in the presence and absence of a crosslinking agent. Thin (about 0.5 mm) disks were swollen in water at 21°C, the final equilibrium swelling being the true water content only for copolymers of high BA content. At low‐medium BA content, swelling was accompanied by the release of a small water‐soluble fraction, leading to a slightly reduced apparent value for the water content. True water contents could be obtained more rapidly by prior Soxhlet extraction with boiling water. For xerogels containing > about 75% VP by weight, the resultant hydrogels had water contents > about 80%. The influences of dose, dose rate copolymer composition, and concentration of crosslinker on the water content, sol fraction, and extension ratio were investigated. A high level of reproducibility in properties of the hydrogels was obtained by numerous replicate experiments. The feasibility of scaling up the preparation to produce long (60 cm) xerogel rods of uniform properties has been demonstrated. For these copolymers, swelling in several common organic solvents generally exceeds that in water.
Synthesis of N,N′‐bis [(dialkoxyphosphinyl) methyl]‐1,4‐benzenediamines and the corresponding polymers
Authors: Kallitsis J. K. , Tsolis A. K. 
Published: April 2003

AbstractThe title diamines were synthesized by condensation of 1,4‐phenylenediamine with paraformaldehyde and a suitable phosphorus acid triester. The N,N′‐dibenzoyl derivatives of the above compounds were also prepared. New flame‐retardant polyamides were synthesized under various experimental conditions by condensation of these diamines with terephthaloyl dichloride. The polyamides produced have low viscosities. Blends with polystyrene (PS) have been made and their flammabilities determined.
Semi‐ and fully interpenetrating polymer networks based on polyurethane‐polyacrylate systems. VIII. The influence of the degree of crosslinking of the second formed network on the morphology and properties of polyurethane polymethylacrylate interpenetrating polymer networks
Authors: Hourston D. J. , McCluskey J. A. 
Published: April 2003

AbstractA series of polyurethane–polymethylacrylate sequential interpenetrating polymer networks containing 40% by weight of polyurethane were prepared in which the levels of crosslinking in the second formed network—polymethylacrylate—was systematically altered over a wide range. The polymethylacrylate networks and the interpenetrating polymer networks were investigated using dynamic mechanical analysis, sonic velocity measurements, and tensile testing. In addition, the interpenetrating polymer networkds were studied using transmission electron microscopy. The interpenetrating polymer networks showed high values of the Oberst damping factor. It was concluded that tightening the second formed network does not produce the dramatic effects associated with decreasing the average molecular weight between crosslinks of the first formed network.
Copolymers of ethylene with butene‐1 and long chain α‐olefins. II. Dodecene‐1 as long chain α‐olefin
Authors: Seppälä Jukka Veli , Oy Neste 
Published: April 2003

AbstractEthylene/dodecene‐1 and ethylene/butene‐1/dodecene‐1 copolymers were prepared and their polymerization reaction in heptane slurry was studied. The Ziegler–Natta catalyst was aluminium‐activated TiCl3, and the cocatalyst was triethylaluminium. The dodecene‐1 contents in the ethylene/dodecene‐1 copolymers were less than 3 wt %. The dodecene‐1 contents in terpolymers of ethylene, butene‐1, and dodecene‐1 ranged up to 10 wt %. The dependence of basic properties on composition of terpolymers was investigated.