bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneous network polymers. VI. Effects of rate of solvent evaporation on residual PGA liquid crystal structure and its dynamic mechanical properties
Authors: Mori Tetsuo , Tanaka Ryuichi , Tanaka Takehide 
Published: April 2003

AbstractDomains of cholesteric liquid crystal structures exist in films of heterogeneous network polymers from poly(L‐glutamic acid) (PGA) and poly(oxyethylene glycol) (PEG M̄n = 302, 1003). The sizes and the amounts of the domains are dependent on the PGA content, the evaporation rate of the solvent, and the molecular weight of PEG. At the PGA content of 40% by weight, the sizes of the domains increase, the glass transition temperatures shift to higher temperatures, and the densities increase with increase in the rate of solvent evaporation. These observations suggest that the phase separation of PEG takes place at a PGA content of 40% when the evaporation rate is small. On the other hand, at a PGA content of 70% by weight, the sizes of the domains increase, the glass transition temperatures shift to higher temperatures, and the densities vary little with decrease in the rate of solvent evaporation. These observations suggest that PEG molecules are accommodated among α‐helices of PGA and that the cholesteric liquid crystal phase grows at a PGA content of 70% when the evaporation rate is small.
Thermal behavior of aryl‐aliphatic polyamides
Authors: Varma I. K. , Sundari V. S. , Varma D. S. 
Published: April 2003

AbstractLow molecular weight poly(p‐phenylene sebacamides) and (m‐phenylene sebacamides) were prepared by interfacial polycondensation by varying the concentration of p‐and m‐phenylenediamine in the initial feed. The polymers were characterized by intrinsic viscosity measurement and IR spectra. The relative thermal stability was evaluated by differential thermal analysis and dynamic thermogravimetry in air and nitrogen atmospheres. A systematic dependence of stability on intrinsic viscosity of poly(m‐phenylene sebacamide) was observed indicating an endgroup initiation of degradation. No such dependence was observed in poly(p‐phenylene sebacamide). A probable mechanism for the thermal degradation has been proposed.
Spectral studies on cellulose treated with sodium deuteroxide
Authors: Venkataraman A. , Subramanian D. R. , Ayare D. S. , Manjunath B. R. , Padhye M. R. 
Published: April 2003

AbstractCellulose II and cellulose I samples were treated respectively with a strong solution of sodium deuteroxide in D2O and a 99% solution of ethylenediamine. The complexes were washed with D2O and the nature of the OD bands were studied after rehydrogenating the sample. The infrared spectra of these rehydrogenated samples showed well‐resolved OD bands which are resistant to reexchange. The Characteristic bands are discussed and compared with the predicted OH‐OD frequency shifts.
Graft copolymerization onto starch. III. Grafting of acrylonitrile to gelatinized potato starch by manganic pyrophosphate initiation
Authors: Mehrotra Rakesh , Rånby Bengt 
Published: April 2003

AbstractRecent development of synthesis and applications in grafting of acrylonitrile (AN) to gelatinized starch by Ce4+ initiation have been briefly reviewed. Using the Mn3+ method, the effects of starch pretreatment temperature on grafting parameters in grafting of AN onto starch have been studied. Total conversion of AN to PAN and % add‐on were almost constant and showed only slight variation with increasing starch pretreatment temperature. Average molecular weight of grafts showed, however, an increase by a factor of nearly 10 (i.e., from 0.4 X 105 to 4 X 105) after swelling and gelatinization of the starch, and the grafting frequency (anhydroglucose units per grafted chain) increased in proportion. In grafting of AN onto gelatinized starch, increasing Mn3+ concentration increased the conversion of monomer and % add‐on, whereas the average molecular weight of grafts and the grafting frequency (AGU/chain) decreased. An increase in the amount of starch also increased the conversion of monomer and the grafting frequency (AGU/chain) but decreased the % add‐on and the average molecular weight of the grafts. Selective solution of PAN homopolymer by dimethylformamide indicated that grafting efficiencies were high in all cases. The results are interpreted in terms of slow termination rates due to high viscosity of gelatinized starch.
Notch sensitivity of polymers
Authors: Prabhakaran R. , Nair E. M. Somasekharan , Sinha Pramod Kumar 
Published: April 2003

AbstractThe influence of notches on the static tensile strenght, low‐cycle fatigue strength, and creep rupture strength was investigated for selected polymeric materials. This investigation was prompted by the unusual phenomena of necking and notch strengthening observed in some glass fiber reinforced plastic materials. Two types of epoxy resin, polymethyl methacrylate and polycarbonate, were studied under static tensile loading. Three sizes of semicircular symmetrical side notch on flat specimens were investigated. It was observed that one of the epoxies was very notch sensitive, while the other exhibited significant (and maximum, out of all the polymers tested) notch strengthening in tensile loading. Perspex and polycarbonate showed a small notch sensitivity for the smallest and intermediate notches but notch strengthening for the biggest notch. The epoxy resin which exhibited notch strengthening was also tested with different percentages of hardener; for the biggest and the intermediate notches, there was a notch strengthening effect and unnotched as well as notched tensile strength showed a peak around 14% hardener. The epoxy which exhibited notch strengthening in tensile loading was next tested in low‐cycle fatigue and creep loading. The behavior in low‐cycle fatigue and creep loading was remarkably similar: it was found that for this polymer, the notch sensitivity was small in the case of the smallest and intermediate notches, whereas there was a significant notch strengthening effect in the case of the biggest notch. It is recommended that notch‐strengthening behavior be added to the other criteria for the selection of matrices for composite materials.
Shear girdling phenomenon in polymers
Authors: Pae K. D. , Silano A. A. 
Published: April 2003

AbstractHollow and solid specimens of polypropylene and solid specimens of polyoxymethylene exhibited an effect under torsional shear which is analogous to the necking usually observed in tensile tests. After reaching some critical shear strain in the postyield region localized shear deformation developed on the gauge length. As twisting was continued a dramatic decrease in the diameter of the cross section was observed. This torsional shear induced phenomenon was named girdling. The superimposition of hydrostatic pressure up to 6 kbar has a significant influence on the extent of girdle formation. Stress whitening, observed on the solid polyoxymethylene specimens was suppressed by the application of pressures greater than 1 kbar. Very large shear strains produced a ratchet‐type fracture surface on the solid specimens which indicates the presence of axial, radial, and tangential strains. Qualitatively, these results are supported by the finite deformation theory of elasticity.
Flame‐retardant action of chlorine compounds and antimony trioxide on cellulose fabric
Authors: Inagaki Norihiro , Hamajima Keiji , Katsuura Kakuji 
Published: April 2003

AbstractChemical research on the flame‐retardant action of halogen compounds and antimony trioxide on cellulose fabric was carried out by thermogravimetry, infrared spectrum analysis, and x‐ray diffraction analysis. The following results and conclusion were drawn: (1) Independently of the type of chlorine atoms introduced, that is, whether chlorine atoms are chemically bonded with cellulose chains or not, the introduction of chlorine atoms alone has little flame‐retardant effect, while combination of chlorine atoms with antimony trioxide is more effective. (2) Addition of only antimony trioxide to samples obtained from the dechlorination of chlordeoxycellulose is as effective as the combination of chlorine compounds and antimony trioxide, in spite of a trace of chlorine in the DCDC samples. (3) Introduction of chlorine compounds yielded the formation of carbonyl and double bond groups in the cellulose chains. The formation of the latter groups was accelerated by the combination of antimony trioxide; that of the former groups was inhibited. Most of the introduced chlorine atoms were missing in the condensed phase even at 300°C while a large portion of the initially added antimony trioxide remained in the condensed phase at least up to 400°C. One mode of flame‐retardant action of the combination of chlorine compounds and antimony trioxide was assumed to be the catalytic effect on the dehydration of cellulose to yield a thermostable polyene structure in the cellulose chains.
Polymérisation des méthacrylates d'ethers glycériques par le peroxyde de benzoyle: Accélération de la polymérisation par les sulfinates d'amines tertiaries
Authors: Ades D. , Fontanille M. 
Published: April 2003

AbstractThe kinetic study of the radical polymerization of phenyl glyceric ether methacrylate, taken as model of the corresponding derivative of bisphenol A, initiated by the system benzoyl peroxide/dimethyl p‐toluidine p‐toluene sulfinic acid salt, was performed. The effect of hydroxylic groups of the monomer on the polymerizability was established. The system used as initiator allows rapid polymerization of the monomer in presence of stabilizers.
Organic polymeric coatings for silica fibers. I. UV‐curing epoxy acrylate (V1F)
Authors: Schonhorn H. , Torza S. , Albarino R. V. , Vazirani H. N. , Wang T. T. 
Published: April 2003

AbstractCoated optical fibers (∼100 μm) were prepared exhibiting fracture strengths in excess of 750 ksi (5.3 GN/m2) for lengths up to 100 meters. To achieve this we have developed a novel coating and coating application process. The coating is an epoxy acrylate, cured by UV irradiation, which may contain a multifunctional silane coupling agent. The coating liquid was applied to the fiber prior to solidification by an applicator, which facilitates centering of the fiber in the coating. Our coating system offers advantages in that there is no solvent to remove, thereby avoiding possible surface “corrosion” of the glass fiber. The reasonably low viscosity of the coating formulation allows for the extensive wetting of the fiber surface irregularities prior to solidification.
Investigation of the composite molecular structure of LDPE by using temperature rising elution fractionation
Authors: Bergström Christer , Avela Eero 
Published: April 2003

AbstractIn the synthesis of low‐density polyethylene there is a direct relationship between the synthesis conditions, molecular structure, and technical properties of the product. The evaluation of the molecular structure of the polymer is therefore important. The most important structure parameters in low‐density polyethylene are molecular weight distribution (MWD), degree of long‐chain branching (LCB), and short‐chain branching distribution (SCBD). Through chain transfer to polymer it is possible to get composite molecules made up of chains with different amounts of short‐chain branching. By using temperature rising elution fractionation (TREF) and plotting the methyl contents or the DTA melt temperature of the fractions as functions of the elution temperature, the SCBD within composite molecules can be evaluated. The deviations from linear relationships are caused by such SCBD within composite molecules. In order to demonstrate the buildup of composite molecules, samples from different parts of a reactor were investigated.
Decomposition of peroxide on carboxymethyl cellulose and its ability to initiate graft copolymerization
Authors: Kubota Hitoshi , Ogiwara Yoshitaka 
Published: April 2003

AbstractThe decomposition of the peroxide group on fibrous carboxymethyl cellulose (CMC) and its ability to initiate graft copolymerization were investigated. The peroxide on CMC liberated hydrogen peroxide when the sample was heated in an aqueous medium. The decomposition of the peroxide was markedly increased by the use of ferrous salt and the irradiation with light of λ > 300 nm. The grafting of methyl methacrylate on CMC peroxide was initiated by heating or irradiating with light, where the rate of grafting and the reciprocal of the average molecular weight of grafts in general were proportional to the square root of the peroxide content of the sample. The peroxide content of the sample was related closely to the number of grafts in initiation. The number was estimated as 17 times for thermal initiation and 6 times for photoinitiation at the maximum values. The CMC peroxide showed a marked activity toward photografting of acrylamide, acrylic acid, acrylonitrile, and vinyl acetate on the substrate.
Influence of shearing history on the rheological properties and processability of branched polymers. I
Authors: Rokudai Minoru 
Published: April 2003

AbstractThe influence of shearing history on the viscoelastic properties of low‐density polyethylene (LDPE) is investigated. Swelling of extrudates from a melt indexer is measured for monitoring the variation in viscoelasticity. Continuous shearing of molten LDPE reduces the swelling ratio. The reduction is not due to molecular degradation, as evidenced by constancy of intrinsic viscosity. The rate of the reduction in the swelling ratio depends on the shearing conditions and characteristics of LDPE, but the swelling ratio finally attain a steady value. The swelling ratio reduced by the continuous shearing is completely recovered by solvent or heat treatment. The ratio of the completely reduced swelling ratio to the completely recovered one is defined as a new index representing the viscoelastic variation, the processing index (PI), and the relationship between PI and the primary molecular parameters of LDPE is investigated. It is concluded that the variation in the viscoelastic properties becomes more remarkable with increase in the weight‐average molecular weight. The cause of the viscoelastic variation is also discussed from the rheological and thermodynamic points of view.
Studies on chitin. VI. Binding of metal cations
Authors: Kurita Keisuke , Sannan Takanori , Iwakura Yoshio 
Published: April 2003

AbstractThe adsorption abilities of chitin and its congeners with two series of degrees of deacetylation prepared by two different deacetylation procedures were compared. Among the polysaccharides obtained by the heterogeneous method, those with higher amino group content had higher adsorption ability. Plots of collection percentages versus amino group content, however, did not give straight lines. The plot for the chelation on the congeners that were prepared by homogeneous hydrolysis had a maximum at about 50% amino group content, and the value was higher than that for the sample with the highest amino group content, which was prepared by heterogeneous hydrolysis. These results suggest that the polysaccharides with about 50% amino group content obtained by the homogeneous procedure are potentially useful for the removal of metals.
A rheological study of long branching in polyethylene by blending
Authors: Jaćović Mihailo S. , Pollock Dorothy , Porter Roger S. 
Published: April 2003

AbstractSteady shear viscosities, dynamic viscosities and moduli, and the corresponding activation energies for flow were examined for a branched polyethylene, a linear polyethylene, and three of their blends at 150° and 190°C. The polyethylenes were chosen to have closely matched molecular weights and distributions. An R‐17 Weissenberg rheogoniometer and an Instron capillary rheometer were used. At lower stress, the branched polymer had a higher viscosity than the linear one, possibly because of the contribution of long branches to entanglements. At high stress, this contribution is reduced and the inherently smaller coil dimensions likely become responsible for the lower viscosity of the branched polymer. The activation energy for the branched polymer is high and decreases with stress, in contrast to the low and almost‐constant value for the linear polymer. The effects here of pressure on compression are considered. The entanglements of long branches may also decrease with increasing temperature. With decreasing stress, the activation energy for branched polymer tends to become constant, corresponding to an absence of pressure effects and an equilibrium entanglement of long branches for a given temperature range. The linear relationship between activation energy and blend composition problably means that any compressional effects, like free volume, are additive and that long‐branch entanglements rearrange with added linear molecules. The linearity may be the result, in part, of a broad distribution for the lengths of long branches.
Synergistic effect in gamma‐irradiated poly(vinyl chloride) hard foils stabilized by plasticizer–stabilizer systems
Authors: Szymański W. , Śmietańska G. 
Published: April 2003

AbstractChanges in transparency and color as well as GHCl values of hard PVC foils exposed to gamma radiation were investigated while using different amounts of the stabilizers ethylene glycol bis‐β‐aminocrotonate (I), calcium/zinc laurate + epoxy compounds (II), and magnesium/zinc stearate + sorbitol + epoxy compounds (III), and plasticizers dioctyl phthalate (DOP) (IV), dioctyl sebacate (V), propylene glycol polyadipate + octyl alcohol composition (VI), and diisotridecyl phthalate (VII). A strong synergistic effect was observed in systems containing both plasticizer and stabilizer. Best results were obtained for the I + II + IV, I + II + V, and I + III + V systems.
Composite cation exchangers
Authors: Vasudevan Padma , Sarma N. L. N. 
Published: April 2003

AbstractSulfonated phenol formaldehyde resins containing different amounts of sulfonated sawdust were prepared. The thermal and chemical stabilities, scientific weight capacity, and apparent capacities for the exchange of Na+, Ca2+, and Mg2+ at different concentrations were detemined for both H+ and Na+ forms of resins. Composites containing up to 30%–50% of sawdust, while being very much cheaper, are comparable in their properties to the pure polymeric resin. Thus, cheaper exchangers can be prepared by substituting part of the polymer by sawdust.
Extrusion die swell of carbon black‐filled natural rubber
Authors: Bagchi Anoop K. , Sirkar Kamalesh K. 
Published: April 2003

AbstractExtrusion die swell of natural rubber compounded with a wide variety of carbon blacks has been determined in a capillary rheometer using a long circular die. The range of variation of carbon black loading, surface area, and structure are, respectively, 10 to 60 phr, 44 to 124 m2/g, and 78 to 120 cc/100 g. The effective carbon black volume fraction φe not participating in the strain recovery leading to die swell is assumed to be the sum of the actual filler volume fraction and the fraction of unextractable rubber determined experimentally for each compound. Bagley and Duffey's analysis of extrusion die swell of unfilled polymers as unconstrained elastic recovery was adopted for a filled elastomeric system whose relative shear modulus (G/G0) is assumed to vary as (1 − φe)−N. The matrix shear modulus G0, originally introduced by Nakazima and Shida on the basis of a linearized approximation, will depend on the shear stress level because of nonlinear deformation. The power N will vary with shear stress which changes the orientation of carbon black aggregates. Except for these features, die swell data for a wide range of carbon black compounds fall on a single curve when plotted in the manner of the predicted relation between the wall shear stress, die swell, and φe. Replacing φe by Medalia's φ′ based on an equivalent sphere concept introduces a larger scatter around the mean curve.
Mechanochemistry and permeability of polyelectrolyte complex membranes composed of poly(vinyl alcohol) derivatives
Authors: Sato Hiroko , Maeda Makoto , Nakajima Akio 
Published: April 2003

AbstractTwo polyanions and two polycations were prepared by the esterification of poly(vinyl alcohol). Properties of their neutral polyelectrolyte complex membranes were compared with those of polyelectrolyte membranes. The charged state on the membranes was related closely to the mechanochemical reaction, the salt rejection, and the solution permeability. Both the salt rejection and the water flux of neutral polyelectrolyte complex memberanes were lower than those of the corresponding acidic or basic complex membranes.
The interaction of hydrogen sulfide with lead‐ and barium–cadmium–zinc‐stabilized poly(vinyl chloride)
Authors: Graedel T. E. , Franey J. P. , Starnes W. H. , Hische D. C. , Warren P. C. 
Published: April 2003

AbstractPoly(vinyl chloride) polymers stabilized with tribasic lead sulfate discolor upon exposure to hydrogen sulfide gas as a result of lead sulfide formation. The discoloration occurs for samples in both cord and sheet forms and is shown to be a function of total H2S exposure, reaching a limiting value that is determined by the amount of lead stabilizer used in the polymer formulation. The permeation and diffusion constants for H2S through PVC stabilized with tribasic lead sulfate and with a liquid Ba–Cd–Zn formulation are found to be PPb = (6.0 ± 0.2) × 10−9, PBaCdZn = (5.2 ± 0.2) × 10−9 (both in cm3 gasċcm film/cm2 areaċsecċcm Hg), DPb = (1.3 ± 0.2) × 10−7 cm2/sec, and DBaCdZn = (6.4 ± 0.6) × 10−8 cm2/sec, all measured at 21°C. The stabilizing efficiencies of the formulations were assessed by HCl evolution measurements, which show that exposure to H2S decreases the initial polymer stability for both Pb‐stabilized and Ba–Ca–Zn‐stabilized formulations. Protection of stabilized PVC formulations from diffusing hydrogen sulfide is thus advisable for long‐term stability as well as for color integrity.
Novolacs from paraformaldehyde
Authors: Rojas A. J. , Williams R. J. J. 
Published: April 2003

AbstractNovolacs were prepared from phenol, paraformaldehyde, and variable amounts of water and methanol using oxalic acid as a catalyst. The retarding effect of water and methanol is clearly shown. Diffusion of reactants in the two‐phase system does not seem to have a bearing on the measurements of reaction kinetics. A correlation between viscosity and refractive index of the polymer phase is shown. The advantages of using paraformaldehyde instead of aqueous formaldehyde solutions are summarized.
The effect of thermal history and strain rate on the mechanical properties of diethylenetriamine‐cured bisphenol‐A‐diglycidyl ether epoxies
Authors: Morgan Roger J. 
Published: April 2003

AbstractThe tensile mechanical properties of diethylenetriamine (DETA)‐cured bisphenol‐A‐diglycidyl ether (DGEBA) epoxies prepared from 9, 11 and 13 phr DETA are reported as a function of thermal history, strain‐rate and test temperature. These epoxies exhibit macroscopic yield stresses and >10% ultimate elongations. The mechanical properties of these epoxies exhibit a free‐volume dependence as a function of thermal history. Annealing below Tg causes an increase in the macroscopic yield stress and a decrease in the ultimate elongation, whereas quenching from above Tg lowers the yield stress and increases the elongation. These mechanical property modifications are shown to be reversible with reversible thermal–anneal cycles. The activation volumes associated with Eyring's theory for stress‐activated viscous flow for the DGEBA‐DETA epoxies are within the range of values (9–12 nm3) reported for noncrosslinked polymers. These observations suggest that the DGEBA‐DETA epoxies are not as highly crosslinked as would be expected from normal addition reactions of epoxide groups with primary and secondary amines. The formation of lower crosslink density networks is discussed in terms of potential chemical reactions.