bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water permeation through elastomer laminates. IV. NBR/EPDM
Authors: Aminabhavi Tejraj M. , Manjeshwar Lata S. , Cassidy Patrick E. 
Published: April 2003

AbstractThe recent considerable interest in the transport and solubility properties of low‐molecular weight penetrants in elastomers arises largely because a number of important practical applications depend wholly or in part on such phenomena. These applications include various protective coatings, packaging materials, selective barriers for the separation of gas and liquid mixtures, biomedical devices, marine applications, etc. The behavior of small molecules in elastomers is strongly dependent on elastomer structure and morphology and any additives to the polymer; therefore, small molecules can be used as very sensitive probes to explore a polymer matrix, especially to gain information about its end applications.
The effect of molecular structure on the gas transmission rates of aromatic polyimides
Authors: Sykes George F. , St. Clair Anne K. 
Published: April 2003

AbstractA series of high‐molecular weight condensation polyimides was evaluated to determine the effect of polymer molecular structure on the transmission rate of oxygen, carbon dioxide, and water vapor. The polyimide films were prepared from either 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) or pyromellitic dianhydride (PMDA) with various diamines. The study shows that molecular structure had a strong influence on gas transmission rates with results for some films varying three orders of magnitude from that of other polyimide films. In general, the BTDA series of polyimides had overall lower gas transmission rates than the PMDA‐derived series. Polymers prepared with meta‐oriented diamines characteristically displayed lower gas transmission than those prepared with para‐oriented diamines.
Semi‐ and fully interpenetrating polymer networks based on polyurethane‐polyacrylate systems. X. Polyurethane‐poly(ethyl acrylate) interpenetrating polymer networks
Authors: Hourston D. J. , Huson M. G. , McCluskey J. A. 
Published: April 2003

AbstractA series of polyurethane‐poly(ethyl acrylate) interpenetrating networks (IPNs) containing 40 wt% polyurethane were prepared, in which the cross‐link density of the polyurethane component was varied by altering the ratio of diol/triol. Decreasing the molecular weight between crosslinks from 9500 to 1200 g/mol brought about an increase in the tensile strength accompanied by a decrease in elongation at break. The tensile properties of the IPNs are, however, poorer than those of the equivalent polyurethane homopolymers. Electron microscopy showed that the polyurethane was present as distinct phases, connected by a cellular fine structure, in the poly(ethyl acrylate) matrix. Dynamic mechanical analysis as well as sonic velocity studies gave results which were consistent with this morphological picture.
Characterization of acidic groups in oxycelluloses IV. Effect of accelerated aging on yellowing as well as carboxyl groups and lactones in pulp
Authors: Achwal W. B. , Murali Radha 
Published: April 2003

AbstractBleached bamboo pulp as well as two oxypulps were subjected to accelerated aging by heating as well as steaming, and the yellowing or color reversion was studied. The yellowing is increased by the presence of free carboxyl and the reducing groups in oxycelluloses. The again treatments were found to cause an increase in free carboxyl groups accompanied by a reduction in copper number. A differentiation between free carboxyl and various lactone groups in oxidized and also aged samples was carried out based on the variation in their reaction rates with KI/KIO3 solution, and the characteristic acidic group spectrum showed that on steam again the fastreacting lactones are lost.
Distribution of end groups and comonomer of the acrylonitrile‐vinyl acetate copolymer
Authors: Ito Seiichi , Okada Chiharu , Kamada Kensuke 
Published: April 2003

AbstractThe number average molecular weight and strong acid end groups (SAG) of fractionated polymers were measured for the acrylonitrile‐vinyl acetate copolymers (93:7 in weight), which were prepared by continuous polymerization in aqueous medium with the persulfate‐bisulfiteion redox system. Average number of SAG per polymer molecule was nearly 1 for fractionated portions of the polymers prepared under the polymerization conditions of water/monomer ratio in the range 4.0–2.5 in weight. No marked difference existed in comonomer content in fractions of these polymers. For unfractionated polymers prepared under the conditions of water/monomer ratio varied from 4.0 to 1.75, average number of SAG was roughly 0.8–1. The proportion of sulfoxy end groups to SAG was estimated to be roughly from 0.5 to 0.6 and increased slightly with increased bisulfite/persulfate ratio. Based on the above results, disproportionation and transfer to bisulfite‐ion are considered to be the main processes of termination of polymer radicals in the studied range of polymerization conditions.
Mechanisms of antioxidant action: Tellurium dithiocarbamates as antioxidants for polypropylene
Authors: Abed‐Ali S. , Ahmed M. A. K. , McWhinnie W. R. , Scott G. 
Published: April 2003

AbstractThe tetrakis (dialkyldithiocarbamato)tellurium(IV) complexes are highly effective thermal antioxidants and melt stabilizers for polypropylene and the evidence suggests that they are converted to the bis(dialkyldithiocarbamato)tellurium(II) complexes and the corresponding dithiocarbamoyl disulfides during processing. The Te(IV) complexes are also effective photoantioxidants and their activity increases with increasing processing time. The bischelates are in general less effective when used alone.
Hydrogels based on graft copolymers of collagen synthesis
Authors: Amudeswari S. , Reddy C. Rami , Joseph K. Thomas 
Published: April 2003

AbstractGraft copolymerization of 2‐hydroxyethyl methacrylate in combination with hydrophobic monomers onto soluble collagen was employed in the synthesis of hydrogels. The hydrogels were formed by simultaneous graft copolymerization and crosslinking. In order to study the effect of various crosslinking agents on the water retention character of the hydrogels, three different crosslinking agents, namely, N,N′‐methylene bis acrylamide, 1,4‐butanediol dimethacrylate, and hexamethylene urethanediacrylate were used. Hexamethylene urethanediacrylate crosslinked systems require a minimum amount of crosslinking agent to attain maximum water content in comparison to the other systems.
Adsorption behavior of heavy metal ions on cellulose graft copolymers
Authors: Okieimen Ebhodaghe F. , Ebhoaye Justus E. 
Published: April 2003

AbstractThe adsorption behavior of cadmium, copper and lead ions on holocellulosic materials containing various levels of polyacrylonitrile and poly(acrylic acid) grafts was examined. The amount of metal ions adsorbed per gram of the modified cellulosic substrate depended on the metal ion type, the nature and level of the incorporated graft polymer. In all cases grafting increased the metal ion‐binding capacity of the cellulosic materials (by up to 50% for Cu (II) ions). The influence of temperature and initial metal ions concentration on the sorption behavior of the metal ions on the composite materials was investigated.
The effect of processing conditions on structure evolution in melt spun poly(ethylene terephthalate) fibers
Authors: Napolitano M. J. , Moet A. 
Published: April 2003

AbstractAn investigation has been made into the structural evolution in poly(ethylene terephthalate) fibers as a function of wind‐up speed (WUS) and quench air temperature (QAT). Analysis of the mechanics and mechanisms of cold drawing reveals that the fiber structure is heterogeneous. Evidence from differential scanning calorimetry (DSC) and density measurements indicates the presence of crystallites which are imperfect according to wide‐angle diffraction (WAXD). Increased thread‐line stress (higher WUS and higher QAT) appears to induce larger and more oriented crystallites in a progressively oriented matrix. A radially layered structure is disclosed from high resolution scanning electron microscopy (SEM) micrographs.
Kinetic study of polymerization/curing of filament‐wound composite epoxy resin sytems with aromatic diamines
Authors: Golub M. A. , Lerner N. R. , Hsu M. S. 
Published: April 2003

AbstractThe kinetics of the polymerization/curing of an 80/20 blend of a diglycidyl ether of bisphenol A (DGEBA) and a diglycidyl ether of 1,4‐butanediol (DGEBD) with a commercial mixture of methylene dianiline and m‐phenylene diamine (Tonox 60/40) was studied, at amine/epoxy ratios ranging from 1.1 to 4.4. Fourier transform infrared (FT‐IR) measurements were used to follow the extent of epoxy conversion at 18–122°C, and bulk viscosity measurements were used to define the working range of the resin. For an amine/epoxy ratio of 1.1, the activation energy for the polymerization/curing reaction (based on time to 50% epoxy conversion in the S‐shaped conversion‐time plots) was 11.9 kcal/mole by FT‐IR. This value compared favorably with the corresponding value of 12.7 kcal/mole obtained by Moroni and co‐workers in a complementary differential scanning calorimetry (DSC) study of the same system. The FT‐IR conversion‐time plots were fitted to a kinetic expression that can be accommodated by an autocatalytic mechanism; the expression contains two rate constants with activation energies of 13.7 and 10.0 kcal/mole, respectively. The viscosity of the curing epoxy resin was found to obey the Williams‐Landel‐Ferry equation, with a Di Benedetto expression for the glass transition temperature.
Preparation of poly(p‐phenylene terephthalamide)/poly(vinyl chloride) molecular composite and its thermal and mechanical properties
Authors: Yamada Kenji , Uchida Masafumi , Takayanagi Motowo , Goto Kohei 
Published: April 2003

AbstractPoly(p‐phenylene terephthalamide) (PPTA) was blended with poly(vinyl chloride) (PVC) by solution‐blending method. PPTA was metalated for dissolving in dimethyl sulfoxide. Dimethyl sulfoxide was used as a common solvent. In PPTA/PVC composite, PPTA accelerated the thermal degradation of PVC. PPTA molecules are aggregated as microfibrillar form in PVC matrix. Such microfibrils are dispersed homogeneously in PVC matrix, according to polarizing microscopic observation. The average diameter of the microfibrils becomes smaller in the composite with lower content of PPTA. In the surface region of PPTA microfibrils the intermolecular hydrogen bonds between CCl of PVC and NH of PPTA are formed. Young's modulus and the yield stress at room temperature were higher in the composites than those in PVC. The modulus of the composites was higher, especially at the high temperatures above their glass transition temperatures, than that in PVC. The temperature dependence of modulus can be calculated by using the mechanical model equivalent to the quasi‐3‐dimensional microfibrillar model which will be approximately applied to the composite structure. It becomes apparent that the modulus of the PPTA microfibrils evaluated by using the mechanical model is higher in the higher molecular weight PPTA.
Phase behavior of binary mixtures of styrene/acrylonitrile copolymers and aliphatic polyesters
Authors: Fernandes A. C. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractThe phase behavior of binary mixtures of copolymers containing varying amounts of styrene and acrylonitrile (SAN) with a large range of aliphatic polyesters was examined. Miscibility was observed over a limited range of AN contents of the SANs, for each polyester, while similarly for each SAN, miscibility was only observed over a limited range of polyester molecular structures. Thermodynamic interaction parameters for the miscible blends were obtained by analysis of the depression of the polyester melting point. A binary interaction model was used to correlate the data and six group interaction parameters were deduced by subdividing the polyester and SAN copolymer repeating units in three different ways. It is concluded that there is a strong repulsion between the segmental units within the polyesters and within the SAN copolymers, which is an important factor in the observed phase behavior.
New linear polyurethaneureas based on polyoxytetramethylene, aliphatic diisocyanates, and aromatic diamines
Authors: Knaub P. , Camberlin Y. 
Published: April 2003

AbstractNew polyurethaneureas have been synthesized with α‐ω hydroxylated polyoxytetramethylene, aliphatic diisocyanates and nonhalogenated aromatic diamines. Four series of PUR have been studied by varying the PTMO molecular weight, the stoichiometry, the nature of the aliphatic diisocyanate, and the steric hindrance of the aromatic diamine. Quantitative evaluation of the degree of phase separation was obtained by DSC. An estimation of the dispersed soft segments outside the soft phase could thus be made. In addition to DSC, dynamic mechanical properties, were obtained for the four series of PUR over a wide temperature range. The hard segments in the PUR chains are amorphous and their high temperature behavior depends only on the strength of interactions in the amorphous state. Finally, stress‐strain measurements were carried out on a few samples, and a wide range of tensile properties has been observed.
Ternary polymer mixtures: Polyarylate/phenoxy/poly(butylene terephthalate)
Authors: Eguiazabal J. I. , Iruin J. J. , Cortazar M. , Guzman G. M. 
Published: April 2003

AbstractThe intended objective of this work was to bring together two immiscible polymers, polyarylate (PAr) and Phenoxy [poly(hydroxy ether of bisphenol‐A)], preparing ternary mixtures with a third component, poly(butylene terephthalate) (PBT). Experimental results showed that ternary mixtures containing 30% or more PBT gave single glass transition temperatures by DSC. Moreover, the PBT melting point depended on the composition of the mixtures. These results, which could be indicative of the existence of a single amorphous phase in these blends, have been discussed. Nevertheless, results must be considered with caution, given the peculiarities of the Tg–composition diagrams for the miscible pairs PAr/PBT and Phenoxy/PBT. Hypothetic interchange reactions during melting have been found to be unimportant.
Electron diffraction study of enzyme‐hydrolyzed cotton samples
Authors: Paralikar K. M. , Bhatawdekar S. P. 
Published: April 2003

AbstractAn electron diffraction study on continuously and repeatedly enzyme‐hydrolyzed cotton samples was carried out. The electron diffraction pattern on repeatedly enzyme‐treated sample reveals a cellulose I pattern with the absence of the 101 plane. This confirms that enzymatic hydrolysis of cotton fibers proceeds preferentially along the 101 plane, being a clevage plane.
Influence of cure conditions on glass transition temperature and density of an epoxy resin
Authors: Cizmecioglu M. , Gupta A. , Fedors R. F. 
Published: April 2003

AbstractThe glass transition temperature Tg and density of a TGDDM‐DDS epoxy resin system were studied as a function of cure times at various cure temperatures. Both Tg and density asymptotically increased toward a maximum value with increasing cure time. The Tg and density measurements were related to the extent of cure, and the relationship in both cases was found to be independent of cure temperature.
Some aspects on the synthesis and characterization of dodecenyl succinic anhydride (DDSA)—a curing agent for epoxy resins
Authors: Ramaswamy R. , Achary P. Sasidharan , Shine K. G. 
Published: April 2003

AbstractDodecenyl succinic anhydride (DDSA), a liquid anhydride curing agent for epoxy resins, was synthesised from C12 olefin and maleic anhydride by the “ene synthesis” reaction. C12 olefin was prepared by the dehydration of lauryl alcohol using Al2O3 (acidic) catalyst. The dehydration was carried out in a flow type reactor. The olefin collected was found to be a mixture of positional isomers of C12 olefin. Systematic studies were carried out by varying the dehydration temperature, mode of feeding and flow rate of lauryl alcohol, and the C12 olefin collected were converted into DDSA and mechanical properties of an epoxy resin–DDSA system were evaluated. The C12 olefins and DDSA were characterized, and the properties correlated with structure and composition. It was found that DDSA derived from C12 olefin with double bond near to the center of the chain gave better tensile strength than the DDSA derived from C12 olefin with terminal double bond.
Structure of fibrous cellulose acetate: X‐ray diffraction, positron annihilation and electron microscopy investigations
Authors: Doyle Stephen E. , Pethrick Richard A. 
Published: April 2003

AbstractX‐ray diffraction, positron annihilation, electron microscopy and bulk density measurements are reported as a function of the degree of acetylation for a linters cotton. Heterogeneous reaction proceeds with a retention of ordered structure in the fibers. Substitution does increase the extent of disorder but is not sufficiently extensive to disrupt completely order at the fiber, fibril, micro fibril, and crystallite levels. The generation of disorder is associated with an increase in the interfibrillar distance, a breakup of the microfibrillar structure without a total disruption of the microcrystalline structure.
Measurement of polydispersity of ultra‐narrow polymer fractions by thermal field‐flow fractionation
Authors: Schimpf Martin E. , Myers Marcus N. , Giddings J. Calvin 
Published: April 2003

AbstractIn this paper we demonstrate that the polydispersity µ = M̄w/M̄N of narrow polymer fractions can be readily obtained by measuring band broadening and its velocity dependence in a thermal field–flow fractionation (thermal FFF) system. The thermal FFF method is shown to be more accurate than size exclusion chromatography for the determination of polymer polydispersities due to the simpler band dispersion function and the higher selectivity inherent to the technique. The polydispersities of a series of four narrow polystyrene samples prepared by anionic polymerization were consequently determined by thermal FFF and found to be much smaller (1.003–1.006) than the ceiling values (1.06) suggested by the suppliers. As part of this investigation, an experimental study of band dispersion in thermal FFF is used to examine current theory. The data show nonequilibrium to be the dominant factor, whereas relaxation effects are insignificant at lower flow rates and can be subdued at higher flow rates. A high correlation between nonequilibrium theory and experiment allows for the estimation of diffusion coefficients from plate height–velocity data.
The acid‐catalyzed degradation of cellulose linters in distinct ranges of degree of polymerization
Authors: Marx‐Figini M. 
Published: April 2003

AbstractCellulose linters with starting degrees of polymerization between 100 < DPn < 6000 had been hydrolytically degraded (0.5 M aqueous solution of KHSO4, degradation temperature 40°C and 60°C) and the results compared with those obtained in a former study on pure cotton cellulose using the same degradation conditions. A complete coincidence in the degradation characteristics of both is shown, distinguishing the latter one by the following features: (1) different kinetic behavior according to the molecular weight range in which degradation takes place; (2) those corresponding to the very high as well as to the very low range of DP reveal a notable decrease of reaction rate; (3) a simultaneous systematic decrease of derivatization capacity occurs in the low molecular weight range; (4) There is no systematic increase of soluble material in the acidic medium with degradation time; (5) in the low molecular weight range, the polidispersity index derived from the molecular weight distributions remains near DPw/DPn = 2.0, except when the hydrolysis had been carried out on already technologically digested materials, causing in these cases a certain increase. The possible reasons for the distinct features of degradation behavior are discussed.
Degradation and cross‐linking of ethylene‐propylene copolymer rubber on reaction with maleic anhydride and/or peroxides
Authors: Gaylord Norman G. , Mehta Mahendra , Mehta Rajendra 
Published: April 2003

AbstractThe reaction of EPR with dicumyl peroxide at 180°C ort‐butyl perbenzoate at 140°C resulted in the formation of a fraction insoluble in cyclohexane at 22°C. The presence of maleic anhydride (MAH) in the EPR‐peroxide reaction mixture increased the amount of insoluble polymer, whose concentration decreased as the peroxide concentration increased. The [η] of the cyclohexane‐soluble polymer decreased and the MAH content increased as the peroxide concentration increased at constant MAH concentration. The [η] and the MAH content of the soluble polymer increased as the MAH concentration increased at constant peroxide concentration. The EPR‐peroxide and EPR‐MAH‐peroxide reaction products were soluble in refluxing xylene and could be fractionated by precipitation with acetone. The presence of stearamide in the EPR‐MAH‐peroxide reaction mixture decreased the amount of cyclohexane‐insoluble polymer, indicative of decreased cross‐linking, but the [η] of the soluble EPR‐g‐MAH increased, indicative of decreased degradation, analogous to the effect of stearamide in the MAH‐peroxide reactions with LDPE and PP, respectively.
Effect of surface treatment of a polymeric filler on its interaction with a plasticizer
Authors: Mikeŝová J. , Hudeĉek S. , Ĉefelín P. 
Published: April 2003

AbstractThe interfacial behavior of a filler–plasticizer system was investigated using the pair poly(sodium methacrylate‐co‐divinylbenzene) beads–diisooctyl phthalate. The effect of various surface treatments of the filler was studied. These consist of a selective extraction of surfactant used in its preparation by emulsion copolymerization and in the adsorption of other types of surfactants. Changes in the compatibility between the two basic components were determined from measurements of the rate of penetration of the plasticizer through the filler bed, from the rheological behavior of concentrated suspensions and from the extractability of the filler from the plasticized PVC matrix.
The phase behavior of ternary blends containing polycarbonate, phenoxy, and polycaprolactone
Authors: Christiansen W. H. , Paul D. R. , Barlow J. W. 
Published: April 2003

AbstractTernary blends comprising bisphenol‐A polycarbonate (PC), the polyhydroxyether of bisphenol‐A (Phenoxy), and poly(ε‐caprolactone) (PCL) were found to be generally miscible at PCL levels greater than 60% by weight and to show multiple amorphous phases at lower PCL levels. The melting point depression of PCL in the miscible region of the ternary and in the miscible binary blends with PC and Phenoxy was examined to obtain the enthalpic interaction parameters, Bij, for each of the three binary interactions. The parameters associated with the miscible binary blends were negative, as expected, and indicated that PCL interacts more exothermically with Phenoxy than with PC. The parameter associated with Phenoxy/PC interaction was strongly positive as expected from the complete immiscibility shown by these materials. The interaction parameters were used to calculate the locus of compositions for which the heat of mixing is zero. The locus was found to agree well with the observed boundary between miscible and multiphase behavior in the ternary. This suggests that the phase behavior of ternary blends is largely determined by the same enthalpic considerations known to govern the phase behavior of binary blends.