bluuebunny/crossref_metadata_2025 huggingface dataset:
Trimethylsilyl cellulose as precursor to regenerated cellulose fiber
Authors: Cooper Geoffrey K. , Sandberg Karen R. , Hinck John F.
Published: April 2003

Trimethylsilyl cellulose (TMSC) has been found to melt at 320–340°C in the absence of oxygen. When TMSC is prepared from chemical cellulose, using hexamethyldisilazane and a catalytic amount of chlorotrimethylsilane/pyridine in dimethylformamide, a thermoplastic material is obtained which may be melt spun into a fiber. This fiber, when treated with mild aqueous acid, yields regenerated cellulose plus hexamethyldisiloxane. The hexamethyldisiloxane can be converted back to hexamethyldisilazane by known chemistry. The fiber properties of the regenerated cellulose were found to be comparable to commercially available rayons. X‐Ray diffraction analyses of the cellulose suggest formation of an unusual polymorphic form.
Fluoroalkylene ether silicate/Viton GLT blends: An approach toward improved low temperature flexibility
Authors: Shaffer A. A. , Cochoy R. E.
Published: April 2003

Low molecular weight fluoroalkylene ether silicate (FES) polymers demonstrating glass transition temperatures of −82°C to −91°C were obtained from the condensation polymerization of fluoroether bisdimethyl carbinols and bis(dimethylamino)methyl vinyl and dimethyl silane derivatives. Peroxide cure reactivity through the pendant vinyl moieties was demonstrated. In an effort to improve the low temperature flexibility of a peroxide curable fluorocarbon elastomer (Viton GLT from Du‐Pont), blends were prepared using the FES material as an additive cocuring plasticizer. Temperature retraction tests demonstrated an optimum 5°C (9°F) improvement in low temperature flexibility. The optimum blend formulation employed FES polymers with vinyl cure site concentrations ranging from 2.35 to 2.70 mol %. The optimum blend formulation maintained the strength and low compression set properties of the Viton GLT standard. These properties reflect sufficient cocuring between the FES and Viton GLT components to provide physical properties adequate for o‐ring seal application. o‐Ring seal evaluations in Freon E6.5 fluid (rod and piston seal tests) demonstrated some seal enhancement and comparable durability to standard Viton GLT o‐rings.
Structure‐property relations of carboxylated nitrile rubber
Authors: Chakraborty S. K. , Bhowmick A. K. , De S. K.
Published: April 2003

The technical properties and the network structure of carboxylated nitrile rubber (XNBR) having a mixed crosslink system of sulfur and metal carboxylate have been studied. XNBR of different carboxyl contents (Krynac 221, Krynac 110C), yielding different concentrations of ionic crosslinks, have been used for this purpose. The amount of ionic crosslinks was also varied by varying the amount of crosslinking agent (zinc peroxide). It has been observed that ionic crosslinks impart high tensile strength, permanent set, and hardness, while sulfur crosslinks introduce high flex crack resistance, elongation at break, and tear strength in the vulcanizate. Heat buildup and resilience could be explained with the help of stress relaxation experiments. Stress decay is more when the amount of ionic crosslinks is higher. Higher stress relaxation gives higher hysteresis. The kinetics of the crosslinking of a mixed crosslink system has also been studied. At overcure times the amount of ionic crosslinks is greater than that of sulfur crosslinks which desulfurizes in this region. The technical properties could be explained on this basis.
Viscoelastic breakup in a high velocity airstream
Authors: Matta J. E. , Tytus R. P.
Published: April 2003

Viscoelastic fluids were injected into a high velocity airstream (200 m/s) to investigate how the addition of small polymer quantities to fluids significantly increase the resultant disseminated drop size. For each liquid tested several hundred resultant drops were sampled and measured using an automated image analyzer. The resultant mass median diameter (MMD) for a viscoelastic fluid was an order of magnitude larger than a comparable viscous Newtonian fluid. A relaxation time measured from a die swell experiment correlates the dissemination results suggesting, an elongational rather than shear breakup mechanism.
Photoinduced acrylamide graft polymerization onto extended hard elastic polypropylene
Authors: Nito Keiichi , Suzuki Shin‐Ichi , Miyasaka Keizo , Ishikawa Kinzo
Published: April 2003

Hard elastic PP films were graft polymerized with PAAm, using a photoinduction method derived by Tazuke. The graft yield (GY) was measured as a function of extension applied to the PP film during the polymerization. The GY increased stepwise when the extension increased above the yield point. This remarkable increase in GY is due to the fact that the surface of voids created by extension are involved in the graft polymerization. The GY obtained under extensions larger than the yield point was much larger than that ever achieved for the usual PP films. The residual strain after the graft polymerization increased with increase in GY, and the relationship between them changed at about 40% GY, suggesting that some change occurred in the location of grafted PAAm in PP films. The graft ratio, determined after complete extraction of PP and PAAm homopolymers, remained nearly constant with polymerization time, except at the early stage of the polymerization. The effect of extension on the graft ratio implied that the size of the voids may affect the degree of polymerization of graft PAAm when the size is comparatively small.
Further studies on cellulose III polymorphs. Transformations to cellulose IV lattices and subsequent reactions
Authors: Chidambareswaran P. K. , Sreenivasan S. , Patil N. B. , Lokhande H. T.
Published: April 2003

Production of cellulose IV polymorphs, their characterization using X‐ray diffraction and infrared spectroscopy, as well as the effect of chemical treatments on these polymorphs have been investigated. Cellulose IIII and IIIII polymorphs, produced from celluloses I and II using EDA—MeOH treatments, were of particular interest as starting materials in the study. Celluloses IVI and IVII gave identical equatorial X‐ray patterns in the absence of other crystal lattices in the samples. Crystallinity as well as conformation were indicated to influence production and further reactions of the samples. The latter included boiling in water, acid hydrolysis, and treatments with EDA—water, EDA—MeOH, and NaOH solutions. Cellulose IVI → I, IVI → I → II, and cellulose IVII → II lattice conversions were demonstrated to occur with EDA—water treatments, thereby providing a new technique for observing these transformations. Conformational differences were apparent among celluloses I, II, IIII, and IIIII, each produced using different experimental procedures.
The effects of orientation and crystallinity on the solvent‐induced crystallization of poly(ethylene terephthalate). II. Physical structure and morphology
Authors: Jameel Hasan , Noether Herman D. , Rebenfeld Ludwig
Published: April 2003

This series of papers summarizes the results of an experimental research program designed to establish the effects of preexisting orientation and crystallinity on the solvent‐induced crystallization of poly(ethylene terephthalate) films. Dimethylformamide was used as a model for a strongly interacting solvent. This paper deals with the morphological and structural modifications induced by the solvent crystallization process. The effects on the structure and morphology of the solvent crystallization were dominated by surface cavitation, creation of voids, and by changes in the degree of crystallinity. The surface structure varied from a spherulitic cavitated structure for films of low orientations (low draw ratios) to a smooth surface at the higher draw ratios. In addition to the change in the surface morphology, an internal void structure was formed due to crystallization taking place in a swollen state. The formation of voids is dependent on the treatment temperature, draw ratio, and the method of solvent removal. The voids collapse upon annealing at high temperatures. Increases in the degree of crystallinity and changes in orientation were dependent on the treatment temperature. The crystallite size goes through a maximum at an intermediate degree of orientation. The crystalline orientation decreases with increasing treatment temperature. The structures formed during solvent treatments did not show any characteristic premelting endotherms at the low draw ratios. In the case of higher draw ratios, a small premelting endotherm was noticeable at a temperature 70°C greater than that of the solvent treatment.
Miscible binary blends containing the polyhydroxy ether of bisphenol‐a and various aliphatic polyesters
Authors: Harris J. E. , Goh S. H. , Paul D. R. , Barlow J. W.
Published: April 2003

Blends of the polyhydroxy ether of bisphenol‐A, Phenoxy, with the polyesters poly(1,4‐butylene adipate), poly(ethylene adipate), poly(2,2‐dimethyl‐1,3‐propylene succinate), poly(2,2‐dimethyl‐1, 3‐propylene adipate), poly(1,4‐cyclohexane‐dimethanol succinate), and poly(ϵ‐caprolactone), are found to exhibit the single, composition‐dependent glass transition temperatures characteristic of miscible systems. Phenoxy blends containing poly(ethylene succinate), poly(hexamethylene succinate), or poly(pivaloactone) were found to be immiscible. Blend interaction parameters, obtained from analysis of the melting‐point depressions observed for miscible blends containing crystallizable polyester components, are found to vary with polyester chemical structure so as to suggest an optimum density of ester groups in the polyester chain for achieving maximum interaction with Phenoxy. Too many or too few ester groups lead to immiscible polyester–Phenoxy blends.
Plastic zones at the tips of inclined cracks in glassy polymers under small scale yielding
Authors: Gdoutos E. E.
Published: April 2003

A thorough study of the shape and size of plastic zones developed around cracks subjected to combined opening‐mode and sliding‐mode loading conditions in glassy polymers under small scale yielding was undertaken. Two pressure‐modified von Mises yield criteria which take into account the characteristic behavior of glassy polymers expressed by the dependence of their yield locus on the hydrostatic stress component and the difference in their tensile and compressive yield stresses were used. The case of an infinite plate subjected to a uniaxial uniform stress at an arbitrary inclination with respect to the axis of the crack was considered. From the whole study useful results concerning the dependence of the shape and size of plastic zones on the crack inclination angle, the Poisson's ratio, and the ratio of the compressive to tensile yield stress of the plate were derived.
A study of poly(p‐xylylene)‐coated AsF5‐doped polyacetylene
Authors: Osterholm J. E. , Yasuda H. K. , Levenson L. L.
Published: April 2003

Electrical conductivity measurements and scanning electron microscopy have been used to study uncoated and poly(p‐xylylene)‐coated samples of polyacetylene doped with AsF5. These initial results indicate a considerable reduction in the decay rate of conductivity in the presence of oxygen as well as a decreased rate of thermal decomposition of the dopant when heated between 50°C and 115°C in vacuum by the coating.
Crosslinking cotton cellulose with aldehydes
Authors: Frick J. G. , Harper Robert J.
Published: April 2003

The relative effectiveness of several aldehydes in crosslinking cellulose of cotton fabric was determined using a pad‐dry‐cure treatment and a treatment by immersion in a solution at room temperature. Aldehydes ranked in the same order of ability to crosslink in both treatments. Factors related to crosslinking ability are discussed. The aldehydes crosslinking to the greater extent hydrated readily in water because the aldehyde group was activated or because cyclic hydrates could be formed.
Grafting of polymeric side chains to gelatin
Authors: Joseph Anne , Radhakrishnan Ganga , Joseph K. T. , Santappa M.
Published: April 2003

Kinetics of grafting of poly(butyl acrylate) onto gelatin was studied with H2O2—ascorbic acid redox systm. Percent grafting, grafting efficiency, Rg, and Rh were determined as a function of time, temperature, initiator, monomer, and backbone concentration. It was found that Rg depends on first power of monomer concentration and 0.5 power to the initiator concentrations. A detailed kinetic scheme is proposed to explain these results.
The evolution of thermosetting polymers in a conversion–temperature phase diagram
Authors: Adabbo Humberto E. , Williams Roberto J. J.
Published: April 2003

A conversion–temperature phase diagram for thermosetting polymers is analyzed. The curing under different external conditions—isothermal, at a constant heating rate, adiabatic, and in a mold at constant wall temperature—is represented by definite trajectories in the phase diagram. Conditions related to incomplete curing or falsification of kinetic parameters are stated.
Effect of heat treatment on the structure and mechanical properties of polyacrylonitrile fibers
Authors: Gupta A. K. , Maiti A. K.
Published: April 2003

Strucure and mechanical properties of untreated and thermally treated (at 110°C and 150°C) drawn polyacrylonitrile (PAN) fiber have been studied through IR spectroscopy, wide angle X‐ray diffraction, and tensile and dynamic mechanical properties measurements. The results are interpreted in terms of the change in the degree of bound nitrile group pairs on heat treatment. The heat treatment at both the temperatures resulted in higher degree of bound nitrile groups (through their dipolar interactions) in the heat‐treated PAN than that of the untreated PAN, as evidenced by IR spectroscopy, X‐ray diffraction, and the mechancal properties. The difference between the results for the two heat‐treatment temperatures are not sufficiently large, although the changes produced by heat treatment at 110°C seems somewhat more prominent than those produced by heat treatment at 150°C.
Investigation of the cellulose/LiCl/dimethylacetamide and cellulose/LiCl/N‐methyl‐2‐pyrrolidinone solutions by 13C NMR spectroscopy
Authors: El‐Kafrawy Adel
Published: April 2003

The cellulose/lithium chloride/dimethylacetamide (DMAc) and cellulose/lithium chloride/N‐methyl‐2‐pyrroilidinone (NMP) solutions were investigated by 13C NMR spectroscopy. Well‐resolved spectra were obtained for both solutions and indicated that cellulose was present in these systems in the form of underivatized cellulose. The change in 13C chemical shifts of DMAc and NMP in the presence of LiCl and LiBr was compared with that of several salt/aprotic solvents, and the results point to the existence of a cellulose–LiCl–DMAc (or NMP) complex in which the lithium cation is strongly bound to the amide carbonyl oxygen and the chloride anion involved in the dissociation of the cellulose hydrogen bonds. Spin–lattice relaxation times (T1 of the 13C carbons of the solvent molecules, DMAc and NMP, show a large decrease in T1 for all solvent carbons upon addition of LiCl. Further decrease in T1 is observed when cellulose is introduced to the LiCl/NMP but not to the LiCl/DMAc systems. These observations are attributed to slower molecular motions of DMAc and NMP in the presence of LiCl, and, in the case of NMP, in the presence of cellulose.
The effect of ultraviolet light on the mechanical properties of polyethylene and polypropylene films
Authors: Raab M. , Kotulák L. , Kolařík J. , Pospíšil J.
Published: April 2003

Measurements were made of dynamic mechanical response spectra and stress–strain properties at room temperature on films of isotactic polypropylene and low‐density polyethylene prior and after ultraviolet irradiation in a Xenotest 450 apparatus. The period of irradiation that caused a deep deterioration of ultimate mechanical properties influenced the dynamic mechanical properties only insignificantly. This is attributed to the heterogeneous nature of the photo‐oxidative degradation process which is concentrated in a finite number of sites, thus forming crack precursors rather than changing the material properties in bulk. For a biaxially oriented tubular film of low‐density polyethylene, anisotropic embrittlement after exposure in Xenotest 450 was observed. This even reversed the order of strain‐at‐break values in the two main directions of the film. This is remarkably similar to the effect of artificial incisions introduced into the specimens.
Nylon 6 polymerization in the solid state
Authors: Gaymans Reinoud J. , Amirtharaj John , Kamp Henk
Published: April 2003

The postcondensation of nylon 6 in the solid state was studied. The reactions were carried out on fine powder in a fluidized bed reactor in a stream of dry nitrogen in the temperature range 110–205°C and during 1–24 h. The solid‐state polymerization (SSP) did not follow melt kinetics, but was found to be limited by the diffusion of the autocatalyzing acid chain end group. Factors thought to influence SSP were studied, e.g., heat treatment, starting molecular weight, and remelting. Surprisningly, heat treatment had little effect, but the starting molecular weight had a strong effect on the reaction rate. The higher the starting molecular weight, the faster the reaction. This could be explained as a changing concentration distribution of the reactive groups in the solid state on SSP. The kinetics of the SSP had more than one region, and the rate of reaction for conversions of over 30% could be expressed as − dc/dt = k(c/t), where k is a dimensionless constant independent of temperature with a value of 0.28. The integrated form has the form − In(c/co) = k In(t/τ), where co is the acid end‐group concentration at the start, t is the reaction time, and τ is the induction time. The value of τ is both dependent on the starting concentration co and the reaction temperature and has an activation energy of 105 kJ/mol.
Kinetic aspects of dyeing processes
Authors: Sada Eizo , Kumazawa Hidehiro , Ando Testuo
Published: April 2003

The dyeing of textiles was classified into two main categories: reactive and adsorptive dyeing. A mathematical model for each case was developed on the basis of a pore model concept. The validity of the proposed models was confirmed by comparison with existing experimental data on dyeing of reactive dyes in cellulose and acid dyes in nylon. It was further desired that the proposed models be checked by experimental results in high fixation regimes. The overdyeing phenomenon may be simulated by intrafiber diffusion with simultaneous multimodal adsorption.
Tensile and impact behavior of drawn polystyrene and high‐impact polystyrene
Authors: Yokouchi Mitsuru , Yokota Akitoshi , Kobayashi Yasuji
Published: April 2003

The tensile behaviors of drawn polystyrene (PS) and high‐impact polystyrene (HIPS) were examined systematically in the wide range of strain rate, 1.7 × 10−4–13.1 m/s, without changing the mode of deformation and the shape of the test pieces. It was found for both PS and HIPS that the flexion points of birefringence with increase of draw ratio are intimately correlated with the tensile properties. Especially, the breaking strain and energy of undrawn and drawn HIPS were assigned to the contributions of the following three toughening mechanisms: (a) the generation of large numbers of microcrazes from the equatorial zone of the dispersed rubber particles; (b) the extension of interfacial rubber phase around the circumpolar zone of the dispersed rubber particles and its disintegration from the matrix component; and (c) the shear band formation of the matrix component followed by cold drawing. These mechanisms were discussed in connection with the factors of stress concentration to the rubber particles, hydrostatic pressure effect arising from the difference in Poisson's ratio of rubber and matrix components, and heat generation due to the adiabatic deformation.
Adsorption of dyes on chitin. I. Equilibrium studies
Authors: McKay G. , Blair H. S. , Gardner J. R.
Published: April 2003

Equilibrium isotherms have been studied for the adsorption of four dyestuffs, namely, Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 84, onto chitin. Langmuir and Freundlich constants have been determined and the effects of chitin particle size and solution temperature have been investigated. Theoretical isotherms have been compared with experimental data and good agreement was obtained using a composite isotherm of the general form: Ye = iCe/(1 + jCem), where i,j, and m are constants.
Simulation of three‐stage nylon 6 reactors with intermediate mass transfer at finite rates
Authors: Gupta Santosh K. , Kumar Anil , Agrawal K. K.
Published: April 2003

A three‐stage isothermal nylon 6 reactor with a kinetic scheme incorporating ring opening, polycondensation, polyaddition, cyclic dimer formation, and reaction with monofunctional acids has been modeled. In the first and third stages, removal of the condensation by‐product, water, is prevented. The second stage of this sequence, however, involves finite rates of diffusion of water to cocurrently flowing inert gas bubbles. the number‐average chain length of the polymer obtained in this reactor differs substantially from that obtained assuming instantaneous water removal and is a function of the various design variables. It is observed that several choices of these design variables can be made to obtain the same product, thus emphasizing the need for more comprehensive optimization studies than hitherto carried out.
Preparation of functional polymer‐microspheres by suspension copolymerization of ethylene glycol dimethacrylate with hydrophilic monomers
Authors: Ohtsuka Yasuji , Kawaguchi Haruma , Yamamoto Takuya
Published: April 2003

A study was made of suspension copolymerization of ethylene glycol dimethacrylate (EDMA) with some hydrophilic monomers (M2) to prepare gel particles having a large number and various kind of functional groups on their surface. Delayed charge of M2 to partially prepolymerized EDMA suspension resulted in the formation of favorable particles. The polymerization leveled off despite an appreciable amount of remaining M2 in the aqueous phase, and the amount of copolymerized M2 and the fraction of on‐surface M2 units depended significantly on the kind of M2 as well as the mode of M2 charge. These dependences were explained in terms of the partition coefficient of M2 between EDMA and water and the monomer reactivity ratio.
Studies on effect of irradiation on semipermeable membranes
Authors: Ramachandhran V. , Misra B. M.
Published: April 2003

The effect of γ irradiation on reverse osmosis (RO) semipermeable membranes has been studied in order to evaluate their performance under the radiation environment arising in the processing of various streams in nuclear industry by reverse osmosis process. Both cellulosic and noncellulosic membranes in dry as well as wet conditions were used. A Co60 source was used for γ doses from kilorads to megarads. The transport properties, namely, salt retention and water flux of membranes determined before and after irradiation, suggested deterioration in the membrane properties due to irradiation. The tensile strength and viscosity of membrane polymer also suggested membrane degradation. Differential scanning calorimetry was taken to look into any structural changes in the membrane polymer as a result of irradiation. IR spectra and X‐ray of membrane polymer was also undertaken to understand the changes on the molecular level.
Chemical factors affecting soiling and soil release from cotton‐containing durable press fabric. VI. Effect of introduction of carboxymethyl groups in the cotton component of polyester/cotton blend
Authors: Hebeish A. , El‐Rafie M. H. , El‐Aref A. T. , Khalil M. I. , Abdel‐Thalouth I. , El‐Kashouti M. , Kamel M. M.
Published: April 2003

Partial carboxymethylation of the cotton component of polyester/cotton blend prior to durable press finishing with dimethyloldihydroxyethylene urea in presence of MgCl2·6H2O was carried out under different conditions to control the carboxyl content as well as alteration of the blend components accompanying the chemical modification. The susceptibility of these modified blend samples before and after crosslinking to aqueous and nonaqueous oily soiling and their ability to release the soil was examined. The general indications are that introduction of carboxymethyl groups in the molecular structure of the cotton component of the blend imparts soil release characteristics of the blend provided that (a) the condition of partial carboxymethylation is not accompanied by profound changes in neither the microstructure of the cotton component nor in the polyester content of the blend and (b) the carboxymethyl content should not be so high. It is proposed that the anionic nature of the modified cotton component of the blend during washing helps in repelling the negatively charged soil particles from the blend surface. In addition, a reduction in the interfacial tension at the soil–water interface assists in rolling up the soil and subsequent removal. This can be turned to the opposite if the electrostatic repulsion is masked through creation of soft swollen environment by significantly increasing the carboxymethyl content, decreasing the polyester content, and/or increasing the swellability of cotton component of the blend.
Preparation of silicon carbide–silicon nitride fibers by the controlled pyrolysis of polycarbosilazane precursors
Authors: Penn B. G. , Ledbetter F. E. , Clemons J. M. , Daniels J. G.
Published: April 2003

Experiments to produce polycarbosilazane resin and high‐strength silicon carbide–silicon nitride (SixNyCz) fibers as well as resin/fiber characteristics are reported. Polycarbosilazane resin was drawn into fibers from the melt and subsequently treated and pyrolyzed into SixNyCz fibers. These materials are characterized by high tensile modulus (29 × 106 psi for 0.4‐mil diameter) and high electrical resistivity (6.9 × 108 Ω·cm for 0.6‐mil diameter).
Estimation of heat evolution during viscoelastic crack propagation by liquid crystal film technique
Authors: Kobayashi Akira , Munemura Masayuki , Ohtani Nobuo , Suemasu Hiroshi
Published: April 2003

Heat generated during dynamic crack propagation in viscoelastic solids was investigated by visible liquid crystal film technique to observe the thermal boundary front emanating from a running crack tip. The crack propagation velocity was also measured by the velocity gauge method. The heat so estimated is correlated with the crack propagation velocity.
Effect of large dosage irradiation in air on polyethylene
Authors: Fujimura Takashi , Hayakawa Naohiro , Kuriyama Isamu
Published: April 2003

The large dosage irradiation effect on polyethylene in air was examined by the method of double irradition. Polyethylene was first irradiated with γ‐rays to a dosage of a few hundred Mrad in air at 298°K. The formed radicals were destroyed, and the polymer, changed chemically and morphologically, was irradiated again in vacuo at 77°K with a dose of 12.7 Mrad. The thermal decay of radicals produced in polyethylene by the second irrdiation was investigated. The results were compared with the sample not exposed to the first irradiation. The results were also compared with previous data of polyethylene irradiated in vacuo to a great extent and then treated in the same manner as that in the present experiment. The results show that scission of the polymer chain by oxidation makes the radical decay faster. Simultaneously, crosslinks formed in polyethylene irradiated in air to a great extent slow down the radical decay. Almost the same number of double bonds was formed in polyethylene irradiated in air as in polyethylene irradiated in vacuo. These double bonds react with alkyl radicals to form allyl radicals.
Adsorption of dyestuffs onto chitin. External mass transfer processes
Authors: McKay G. , Blair H. S. , Gardner J.
Published: April 2003

The effect of several variables on the adsorption rate of four dyestuffs onto chitin was studied. A model is proposed enabling the film mass transfer coefficients to be determined. The coefficients were independent of initial dye concentration, chitin mass, chitin particle size, and temperature; a slight dependence with agitation was obtained. The film mass transfer coefficients at 400 rpm were 2.8×10−3, 2.9×10−3, 3.9×10−3, and 0.9×10−3 cm/s for Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 85, respectively.
Rheograms of cellulosic polymers from the melt flow index
Authors: Shenoy A. V. , Saini D. R. , Nadkarni V. M.
Published: April 2003

Data on the variation of melt viscosity over a wide range of shear rates and temperatures are necessary in the processing of cellulosic polymers. An effective method has been proposed to estimate the viscosity vs. shear rate flow curves of a cellulosic resin at temperatures relevant to the processing conditions, from its melt flow index and glass transition temperature. The method involves the use of a master curve obtained by coalescing the rheograms of various grades in terms of a modified viscosity, η˙MFI, and a modified shear rate, γ˙/MFI. Master curves have been reported for cellulose esters and ethers.
Highly reactive wood pulps for cellulose acetate production
Authors: Sears K. D. , Hinck J. F. , Sewell C. G.
Published: April 2003

Wood pulps highly reactive in both high‐ and low‐catalyst cellulose acetate processes can be prepared by mercerization and then treatment with alkylene oxides; only trace levels of substitution are required. The fiber inactivating effects of mercerization after drying are overcome, and several acetate properties are improved by this process. The reactivity characteristics cannot be duplicated by similar modifications of nonmercerized fibers; in low catalyst processes such pulps actually show reduced reactivity.
Solution behavior of ionomers. III. Sulfo‐EPDM‐modified hydrocarbon solutions
Authors: Lundberg Robert D.
Published: April 2003

The solution viscosity of polymer thickened hydrocarbons normally decreases markedly as temperature is increased. It has been observed that metal sulfonate ionomers, such as sulfonated ethylene propylene terpolymer, or sulfo‐EPDM, when dissolved in a mixed solvent behave much differently. Specifically, sulfonated ionomers, dissolved in xylene or paraffinic oils with low levels of a polar cosolvent, can provide solutions whose viscosities are either relatively constant or can actually increase with increasing temperature. This isoviscosity effect can be manifested over broad temperature ranges and is mechanistically different from the behavior of conventional polymer solutions. This unusual behavior is explained on the basis of a simple equilibrium involving solvated ion pairs and is shown to be a specific example of a general phenomenon.
Boiling water aging of a miscible blend of polycarbonate and a copolyester
Authors: Joseph E. A. , Paul D. R. , Barlow J. W.
Published: April 2003

Extruded films and injection molded bars of a copolyester based on 1,4‐cyclohexanedimethanol condensed with a mixture of isophthalic and terephthalic acids, of a bisphenol‐A based polycarbonate, PC, and of the miscible blends of these compounds were exposed to boiling water for up to 15 days. The ductility and strengths of film specimens rich in PC were found to degrade as a result of PC hydrolysis. These properties of specimens rich in copolyester were found to decline as a result of crystallization of the copolyester. Best overall performance was obtained for 50/50 blends of PC and copolyester. All amorphous materials showed a transition from ductile to brittle behavior at the same weight average molecular weight as previously observed for pure PC. This feature plus the observation that PC hydrolyzes in the blend at the same rate as it does in the pure state allows most of the superior performance of the 50/50 blends to be explained in terms of blend molecular weight.
Interaction of heavy metals with chitin and chitosan. III. Chromium
Authors: Maruca R. , Suder Billie Jo , Wightman J. P.
Published: April 2003

The interaction of the natural marine polymer chitin and its deacetylated derivative chitosan with chromium has been investigated. The uptake of chromium from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The uptake of Cr(III) on chitosan was significantly greater than that on chitin. The smaller the size fraction of the chitin/chitosan, the greater the uptake of Cr(III). The Cr(III) uptake increased with increasing solution pH. Minimal desorption of chromium was observed on washing previously chromium‐equilibrated chitosan with distilled water. The uptake of Cr(III) by chitosan was enhanced in the presence of phosphate, whereas the converse was not observed. Minimal uptake of Cr(VI) as dichromate by chitin and chitosan was measured. Cr‐containing nodules were noted in the SEM/EDAX analysis for Cr(III)‐equilibrated chitosan. Cr‐containing clusters were detected for Cr(III)‐ plus phosphate‐equilibrated chitosan. XPS results supported the conclusions drawn from the isotherm studies.
Mechanochemical process in cotton cellulose fiber
Authors: Hon David N.‐S. , Srinivasan K. S. V.
Published: April 2003

Mechanical processing of cotton cellulose by means of a fiber cutter resulted in the disaggregation and defiberation of fiber bundles, shortening of fiber length, and loss of degree of polymerization. It is evident that the mechanical energy supplied by shear forces is sufficient to cause homolytic scission of cellulose main chains. Mechanoradicals formed in the interim were verified by ESR studies. The crystallinity of cellulose was not influenced by mechanical treatments, but accessibility of the polymer was substantially increased due to the creation of new surfaces. The mechanically treated fiber inclined to proceeded oxidative chain reaction during aging. Regardless of their treatment conditions, cellulose fiber reached its limiting lower molecular weight after 100 days of aging.
Permeation of methyl chloride and benzene through FEP Teflon
Authors: Duncan T. , Koros W. J. , Felder R. M.
Published: April 2003

Permeabilities and diffusivities of methyl chloride and benzene vapors at low activities in FEP Teflon membranes were measured in a continuous‐flow permeation cell, at temperatures ranging from 47°C to 150°C. In all cases investigated, the permeabilities and diffusivities were independent of the penetrant partial pressure, and the permeation process was well described by a Henry's law sorption–Fickian diffusion model. The activation energies for permeation and diffusion and the sorption enthalpy were respectively 34.8 kJ/mol, 50.1 kJ/mol, and −15.3 kJ/mol for methyl chloride and 49.5 kJ/mol, 69.1 kJ/mol, and −19.6 kJ/mol for benzene. The diffusional activation energies for these two substances and other low molecular weight hydrocarbons correlate reasonably well with the Lennard–Jones collision diameters of the penetrant molecules. The solubilities correlate approximately with the penetrant boiling points, but the highly polar nature of methyl chloride and the aromaticity of benzene lead to deviations between the solubilities of these substances and those of nonpolar aliphatics with the same tendency to condense from the vapor phase.
Glass transition temperature predictions in some epoxy polymers
Authors: Lee Gilbert , Hartmann Bruce
Published: April 2003

The glass transition temperature as an additive property was studied on a series of epoxy/amine crosslinked polymers. Various methods from the literature of analyzing the glass transition temperature in terms of components are presented and then judged to determine which of these methods gives the best agreement between calculated and measured glass transition temperature. It was found that predictions agree on the average with the measurements to within the accuracy of the measurements, approximately 3%.
An approach in modeling the tubular polymer reactor
Authors: Nigam K. M. , Nigam K. D. P.
Published: April 2003

An analytical solution for diffusion with a homogeneous first‐order reaction in the bulk and a heterogeneous reaction at the reactor wall in a non‐Newtonian laminar flow tubular reactor is presented by using the Galerkin technique. The effect of reaction rate constants on dispersion is studied under isothermal conditions. It is found that, for the same mean velocity of the flow, the effective dispersion coefficient decreases with increase in the chemical reaction rate constants.
Role of micellar equilibria on modelling of batch emulsion polymerization reactors
Authors: Morbidelli Massimo , Storti Giuseppe , Carrà Sergio
Published: April 2003

A comprehensive model of emulsion polymerization batch reactors is presented. The nucleation mechanism via micelles is examined in detail through the introduction of a micellar equilibria model. This allows to predict the influence on the process of the emulsifier amount and type and of the solution ionic strength. A comparison with experimental data of styrene and butadiene polymerization is performed.
Coordination copolymerization of butadiene and isoprene with rare earth chloride–alcohol–aluminum trialkyl catalytic systems
Authors: Zhiquan Shen , Xiangyu Song , Shuxiu Xiao , Jipo Yang , Xianglan Kan
Published: April 2003

Butadiene and isoprene were copolymerized with LnCl3–ROH–AIR3 catalytic system. The products obtained were confirmed to be copolymers by their glass transition temperatures and characteristic pyrolytic chromatograms, etc. The equation for copolymerization rate may be expressed as Rp = Kp(M)2(cat). The rate constants of copolymerization, activation energy, and monomer reactivity ratios for catalytic systems containing various rare earth elements in III‐B family and different solvents were determined. It was found that the reactivity ratio of butadiene was greater than that of isoprene and r1r2 near 1, and the composition and microstructure of copolymers were not much affected by variation of polymerization conditions. Both monomer repeat units in the copolymers had cis‐1,4 contents above 95%, which is a distinguishing feature of coordination polymerization with the lanthanide catalyst system.
Studies on syntheses and permeabilities of special polymer membranes. XLVII. Active transport and selective transport of metal ions through membranes from poly(isobutylene‐alternative co‐maleic anhydride) and poly(vinyl alcohol)
Authors: Uragami Tadashi , Watanabe Shizuharu , Nakamura Reiichi , Yoshida Fumihiko , Sugihara Mizuho
Published: April 2003

When a cation exchange membrane having carboxyl groups, made of poly(isobutylene‐alternative co‐maleic anhydride) and poly(vinyl alcohol), was set in a diaphragm type cell, in which one side of the solution was adjusted to be acidic and the other side alkaline, metal ions were actively transported from the alkaline side to the acidic side across the membrane against the concentration gradient of metal ions between both sides. The driving force of the transport of metal ions was the difference in H+ ion concentration between both sides. It was presumed that the active transport was carried out chemically and physically. In the selective transport of metal ions, the selectivity was dependent on both the hydrated ionic radius for the metal ions and the affinity between the carrier fixed to the membrane, the carboxyl group, and the metal ions.
The adsorption of dyes in chitin. III. Intraparticle diffusion processes
Authors: McKay G. , Blair H. S. , Gardner J.
Published: April 2003

Intraparticle diffusion processes for the adsorption of dyestuffs onto chitin have been studied. The amount of dye adsorbed per gram of chitin has been plotted against the square root of time. The slope of this plot is linear and has been defined as a rate parameter k. This rate parameter has been determined for a number of process variables, including initial dye concentration, agitation, chitin particle size, chitin mass, temperature, and solution pH. However, sometimes two and even three linear regions are apparent on the root time plots indicating a possible branched pore mechanism. The controlling mechanisms are due to macropores and micropores in the chitin particle creating rapidly and slowly diffusing regions.
Improved processing of thermotropic liquid crystalline polyesters
Authors: Demartino Ronald N.
Published: April 2003

A series of thermotropic liquid crystalline polyesters based onp‐hydroxybenzoic acid, terephthalic acid, 2,6‐dihydroxynaphthalene and containing small amounts of either Bisphenol A, 2,7‐dihydroxynaphthalene, or polyethylene terephthalate (PET) as comonomers were prepared. The latter three materials were investigated as a means of lowering the spinning temperature of the base polymer without sacrificing properties. Samples containing 1–2.5% Bisphenol A or 2.5–5% 2,7‐dihydroxynaphthalene retained most of the properties (modulus fell slightly), but spinning temperature reduction was minimal. Polymers containing 2.5–5% PET retained full properties at spinning temperatures 60–80°C below the control.
Dynamic mechanical properties of elastomers for use in circulatory assist devices
Authors: Murayama T. , McMillin C. R.
Published: April 2003

The dynamic mechanical properties of several polyurethane and polyolefinic elastomers for use in circulatory assist devices have been studied. This work was a part of a project on the characterization of elastomers suitable for cardiovascular application. In this paper, changes in the dynamic modulus and internal friction of these elastomers (Avcothane‐51®, Biomer®, butyl rubber, Pellethane®, and Hexsyn®) are described as a function of long‐term static and dynamic exposure to whole human blood. The dynamic moduli of control of Pellethane and Hexsyn are higher than that of Avcothane, NBS butyl rubber, and Biomer at human body temperature (at 37°C). The dynamic moduli of Biomer specimen fatigued in whole human blood at 37°C are least affected in temperature range of 25°C to 140°C as compared with the control. The loss tangents are decreased slightly. It indicates small structural changes after fatigue in whole human blood. These five materials should be considered for use in most or some cardiovascular applications because their mechanical properties do not change appreciably. Biomer performs well under a variety of experimental conditions, long‐term exposure to blood, uniaxial and biaxial fatigue test, and dynamic mechanical properties of specimen fatigued in whole human blood.
Sequential nature of the exothermic reactions leading to the formation of flexible polyurethane foams
Authors: Van Gheluwe P. , Leroux J.
Published: April 2003

The exotherms of the reactions leading to the formation of polyurethane foams were measured. The inflection points of the exotherm curves were made evident by continuous differentiation with respect to time. The position and magnitude of the inflection points demonstrated the sequential nature of the reactions. The effects of the functionality of the polyol, the concentrations of the tin and amine catalysts, and the silicone surfactant are discussed.
Compatibility of low‐density polyethylene–poly(ε‐caprolactone) blends
Authors: Kalfoglou Nikos K.
Published: April 2003

The compatibility of low‐density polyethylene (LDPE)–poly(ε‐caprolactone) (PCL) was examined using the microscopic, the dynamic mechanical, and the DSC techniques. Morphological examination revealed that at low PCL concentrations, when specimens are severaly quenched, a uniform microspherulitic structure is formed. The dynamic mechanical spectra, at isochronous conditions (110 Hz), indicate very limited mixing of the amorphous phase of the two components at the intermediate compositions. More drastic relaxation shifts were observed at the extremes of the composition range. Ultimate strength and elongation at break are characteristic of a mechanically compatible system at high and low PCL contents. In the intermediate composition range their low value indicates phase separation. DSC measurements showed a nonlinear dependence of bulk crystallinity on blend composition; also, that the presence of PE enhances the degree of PCL crystallinity. Thermal history strongly affects bulk crystallinity. At elevated temperatures, near the mp of PE, thermal treatment affects considerably the melting point of the PE crystals.
Effect of a filler on the dielectric properties of an epoxy resin
Authors: La Mantia F. P. , Schifani R. , Acierno D.
Published: April 2003

The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
Isothermal degradation of cis‐1,4‐polyisoprene vulcanizates
Authors: Tamura Saburo , Murakami Kenkichi , Kuwazoe Hironori
Published: April 2003

The isothermal degradation of high cis‐1,4‐polyisoprene vulcanizates having different crosslinking structures was investigated by a measurement of weight loss of sample, IR and NMR, gel permeation chromatography (GPC), and gas chromatography (GC). The degradation behavior of dicumy peroxide‐cured sample is similar to that of the uncrosslinked one. On the other hand, a sulfur‐cured sample is very different from the other samples. At the initial stage of the degradation, weight loss in this sample is faster than that in an uncrosslinked one. Furthermore, a microstructural change in this polymer occurring by thermal degradation is also very much larger than microstructural changes in the others. This will be attributed to polythiyl radicals produced by the scission of polysulfide crosslinkages. Although the polyisoprene chain undergoes random scission along the main chain above 473 K under inert gas or in vacuo, a molecular weight distribution of the residue after thermal degradation was broadened as the degradation proceeded. That is to say, the fragments having enormous molecular weight increase together with the production of lower molecular weight compounds. This indicates the occurrence of crosslinking reaction and the addition of polymer radicals to carbon–carbon double bonds in another polymer molecule in the thermal degradation process. Such reactions are thought to take place in the crosslinked polymers, in particular the sulfur‐cured polymer, in larger quantities. Thermal degradation mechanisms were discussed in some detail.
Coupling of polystyrene to a silane‐treated mica
Authors: Favis B. D. , Leclerc M. , Prud'Homme R. E.
Published: April 2003

This paper deals with the coupling of polystyrene to a closely packed and highly ordered cationic vinylbenzyl silane (CVBS) on mica. It is shown that a thermal treatment is required for maximum retention of polystyrene on treated mica. Moreover, a thermal treatment at 250°C is much more effective than one at 170°C. The effect of the number of silane monolayers on mica was investigated. In general, one monolayer of CVBS gave optimum retention of polystyrene. The addition of peroxides further improved this retention and at the same time allowed the use of lower treatment temperatures. Some data are presented which consider the importance of the silane solution concentration and silane functional groups.
Partially imidized, water‐soluble polymeric amides. I. Partially imidized polyacrylamide and polymethacrylamide
Authors: Shepitka J. S. , Case C. E. , Donaruma L. G. , Hatch M. J. , Kilmer N. H. , Khune G. D. , Martin F. D. , Ward J. S. , Wilson K. V.
Published: April 2003

Five to six million molecular weight polyacrylamide and polymethacrylamides of comparable post‐alkaline hydrolysis viscosities were imidized by dissolution and heating in 6N HCl. After alkaline hydrolysis, the imidized polymers demonstrated significantly better retention of viscosity to 2% NaCl than did similar partially hydrolyzed polymers. Viscosities in 0.01% NaCl and resistance to shear were not markedly affected by this modification. It is assumed that this improved performance in brine is the result of chain stiffening due to intrachain imide rings.