bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of polyelectrolyte complex for immobilization of microorganisms
Authors: Kokufuta Etsuo , Matsumoto Wataru , Nakamura Isei
Published: April 2003

Cells from Escherichia coli (IAM 12119) were immobilized with the polyion complex of trimethylammonium glycol chitosan iodide (TGCI) and potassium poly(vinyl alcohol) sulfate (KPVS). The immobilization was carried out at pH 8 by mixing TGCI with the cell suspension, followed by addition of KPVS. The immobilized cells were characterized by investigating the glucose oxidizing activity. The results obtained indicated that the glucose consumption with immobilized cells is due not only to the cells released from the complex support but also to the entrapped cells which are grown in the complex; therefore, the cells entrapped in the complex have the glucose oxidizing activity. The physicochemical studies on the immobilization mechanism showed that cells are immobilized via two stages: the aggregation of cells with TGCI and the entrapment of the aggregates in the TGCI–KPVS complex. In the aggregation process, a part of TGCI which is added to cell suspension adsorbs on the cells and the other remains in the suspension. In the entrapment process, the remainder forms the polyion complex with KPVS added and the aggregated cells are coprecipitated with the complex.
Calibration of size‐exclusion chromatography columns with polydisperse polymer standards. I. Theory
Authors: Kubín M.
Published: April 2003

Relationships have been derived between the spreading factor and the respective slopes of actual and effective linear calibrations in size‐exclusion chromatography. On this basis a new calibration procedure has been developed for determining simultaneously the dependences of sample molecular weight and of the spreading factor on elution volume from chromatograms of polydisperse polymer samples with known values of number‐and weight‐average molecular weight. No assumptions about the shape of sample molecular weight distribution are required. If necessary, the calibration dependences may be further improved by an iteration procedure described.
Exactly alternating silarylene–siloxane polymers. V. Evaluation of the mechanical properties of crosslinked elastomers
Authors: Livingston Mary E. , Dvornic Peter R. , Lenz Robert W.
Published: April 2003

The search for technologically useful elastomers with good thermal stability at elevated temperatures combined with low temperature flexibility has led us and others to the preparation of a series of linear alternating silarylene–siloxane polymers. Because of the very favorable thermal stabilities of these polymers, a detailed study was made of methods for their vulcanization and for the evaluation of their mechanical properties. The results of these investigations are described, including mechanical properties of the vulcanizates both before and after heat aging and before and after immersion in different solvents, as well as their characteristics after prolonged and repeated extension.
Kinetic model of cure reaction and filler effect
Authors: Hsich Henry S.‐Y.
Published: April 2003

A new kinetic model for cure reactios has been developed from the concept of nonequilibrium thermodynamic fluctuation theory in which a distribution function relaxation spectrum is used for explaining cure kinetics of polymer–filler systems. It is found that an increase in filler loading reduces the relaxation time but broadens the relaxation spectrum of the cure reaction. The model is used to explain the cure curves which are obtained both from the Monsanto Rheometer 100 and the Rheometric Mechanical Spectrometer. Not only can the model predict scorch time, cure time, and activation energy of the cure reaction, but it can also take into account polymer–filler interaction and predict physical and mechanical properties of polymer systems during cure.
A comparative study of semi‐2 and full interpenetrating polymer networks based on poly(n‐butyl acrylate)/polystyrene
Authors: Widmaier J. M. , Sperling L. H.
Published: April 2003

Sequential poly(n‐butyl acrylate)/polystyrene (PnBA/PS) semi‐2 and full IPN's of various compositions were made by UV photopolymerization. Acrylic acid anhydride and divinylbenzene were used as labile and permanent crosslinkers, respectively, for the rubbery phase and the plastic phase. After IPN formation, network I was selectively decrosslinked. After extracton of polymer I, the remaining PS network II was characterized by swelling measurements and examined by scanning electron microscopy. It was found that crosslinked PnBA affects the formation of the second network more than uncrosslinked PnBA does. A porous phase formed by an aggregate of spherical polystyrene domains was observed. The experimental domain diameter was in good agreement with previous theoretical values. The dynamic mechanical properties of full IPN's, decrosslinked IPN's, and semi‐2 IPN's were also studied. A significant level of molecular mixing was found for full IPN's of midrange compositions. The major difference between the full IPN's and the decrosslinked IPN's is that the glass transitions of the respective polymers become more pronounced in the latter case, with a deeper valley between them. With the destruction of the crosslink sites, there is no longer a forced miscibility of the interlocked phases, which are, in fact, thermodynamically incompatible.
Fractography of human hair
Authors: Kamath Y. K. , Weigmann H.‐D.
Published: April 2003

The fracture behavior of human hair has been investigated with a view toward delineating fracture mechanisms that lead to different types of fracture under tensile loading. Principally, three types of fracture are encountered—smooth fractures, step fractures, and fractures involving undefined fibrillated ends. The moisture content of the fiber plays an important role in determining the type of fracture that occurs. Fiber conditioned at either low (∼0%) or high (90%) relative humidity give predominantly smooth fractures, whereas those conditioned at intermediate relative humidities given predominantly step fractures. Surface treatments with polymers or surfactants do not seem to have any effect on the strength or the fracture behavior of fibers. At low moisture contents, fracture initiation occurs more often in the cortex, whereas, at high moisture contents, fracture almost always initiates at the surface of the fiber, suggesting that the swelling pressure of the cortex plays a significant role in fracture initiation. Fibers with larger cross‐sectional areas tend to split along the axis because of the higher probability of encountering flaws or medullary cells which direct cracks along the fiber axis. Unlike synthetic polymeric fibers, hair fibers seem to follow the Griffith criterion of brittle fracture. This may be coincidental since electron microscopic evidence suggests that fracture propagation occurs by secondary cracks generated as a result of stress concentrations building up at the periphery of the primary crack. The rate of stress transfer to adjacent cortical cells via intercellular cement probably plays an important role in the fracture mechanism.
Diffusion of cyclic hydrocarbons in benzene‐swollen, divinylbenzene‐crosslinked polystyrene beads
Authors: Roucis John B. , Ekerdt John G.
Published: April 2003

Diffusion of cyclic hydrocarbons within benzene‐swollen, polystyrene‐divinylbenzene gel‐type beads were studied at 25°C. Solute concentrations less than 6.3 × 10−2M and volume fractions of polymer less than 0.6 were used. Diffusion coefficients were calculated assuming Fick's law diffusion, and were found to depend upon the volume fraction of polymer. The dependence suggests that the swollen polymer network acts as a physical obstruction to diffusion. Studies indicated that the solute–solvent interactions affecting diffusion were the same in the solvent‐swollen polymer as in the pure benzene solvent.
Viscoelastic and engineering properties of poly(vinyl chloride) plasticized with polycaprolactone‐based polyurethanes
Authors: Bandyopadhyay P. K. , Shaw M. T.
Published: April 2003

The plasticization of poly(vinyl chloride) (PVC) by polyurethanes made from polycaprolactone (PCL) diol and p.p′‐diphenylmethane diisocyanate (MDI) was investigated. By varying the PCL chain length and substituting with polyether chains such as poly(tetramethylene ether) (PTME) or poly(ethylene oxide) (PEO), also of various chain lengths, the efficiency of plasticization was changed. High urethane content, such as obtained with PCL‐530/MDI, decreased the miscibility of the polyurethane and PVC. Plasticizing efficiency of the polyurethanes, as indicated by transparency, flexibility, and engineering properties of the blend, increased on increasing the initial PCL chain length. However, polyurethanes containing very high‐molecular‐weight PCL (e.g., PCL‐3000) slowly crystallized from a 50:50 blend with PVC. PVC/polyurethane ratio also had a significant effect on crystallization, as indicated by the rapid crystallization of PCL‐2000/MDI polyurethane when it exceeded 50 wt % in the blend. The transparency and flexiblity of 50:50 blends were lowered by systematically replacing PVC‐miscible PCL‐2000 segments in the polyurethane with PTME‐2000, PEO‐200, and PEO‐1500 segments. The polyurethanes became highly immiscible in PVC beyond the limiting mole fraction replacements of 0.6 for PTME‐2000, 0.8 for PEO‐200, and 0.4 for PEO‐1500. Such chemical modification gave controlled and temperature‐dependent miscibility in PVC and consequently blends with broadened glass transitions and high damping properties over a wide temperature range. Decreased miscibility in the blend gradually decreased elongation at break and tensile strength, but increased the modulus. A general correlation of the viscoelastic and tensile properties of the 50:50 blends with the weight fraction, rather than mole fraction, of the PCL content in the polyurethane composition was found; replacement of PCL beyond a limiting weight fraction by polyethers and MDI produced PVC‐immiscible polyurethane. These limiting weight fractions are 0.6, 0.5, and 0.4 with PTME‐2000, PEO‐200, and PEO‐1500, respectively, which denotes the order of decreasing miscibility of these polyurethanes in PVC. Viscoelastic and engineering properties of the blend with a particular polyurethane could also be controlled by varying the PVC/polyurethane ratio. Many of these semimiscible blends showed evidence by lower critical solution temperature (LCST) behavior at about −30°C, but complete cloud and point curves were not constructed.
Slow decomposition of silicone rubber
Authors: Vondráček P. , Gent A. N.
Published: April 2003

The sol content of previously extracted samples of lightly crosslinked silicone rubber has been found to increase during prolonged storage under relatively mild conditions. Simultaneously, the tensile stress slowly decreases in samples held stretched, and the equilibrium degree of swelling increases somewhat. Thus, the polymer network appears to undergo slow decomposition. This process is accelerated by moisture, by ammonia vapor, and by raising the temperature of storage. It is slowed down by prior treatment of the polymer with a silazane reagent which reduces the number of residual OH groups. It is therefore attributed to hydrolytic decomposition of the poly(dimethylsiloxane) molecules initiated by OH groups.
Temperature effect on the permeation through poly(2‐hydroxyethyl methacrylate) membrane
Authors: Yoon Sung Chul , Jhon Mu Shik
Published: April 2003

The temperature dependence of permeability through highly syndiotactic poly(2‐hydroxyethyl methacrylate) [P(HEMA)] membrane is reported for highly polar organic solutes such as ureas, methyl substituted ureas and amides, and for NaCl and Na2SO4. The membranes used were equilibrated in distilled water at each temperature before measurements. From the linear correlationship between the excess heat capacities, ϕCpo(excess) in aqueous solution at infinite dilution and the permeability parameter PM1/3, it is found that the water structure perturbing capability of the polar organic solutes is a controlling factor in the permeation mechanism at relatively low temperature, where P(HEMA) membrane has higher water content and more structured water. In addition, it is found that the poor separation for urea of cellulose acetate membrane in the reverse osmosis practice is due to the higher water structure‐breaking capability of urea.
A surface acoustic wave (SAW) probe for the thermomechanical characterization of selected polymers
Authors: Groetsch John A. , Dessy Raymond E.
Published: April 2003

Specially designed surface acoustic wave devices may be used to examine the physical characteristics of the surfaces of thin polymer samples. Both cast films and thin film samples may be employed. The devices uniquely offer an opportunity to study: (1) very thin films, (2) surface‐segregated materials, (3) the effect of diffusion of vapor into the surface region, and (4) simultaneous measurements of exterior surfaces of laminates. No special sample preparation is required. The Tg, Tm, T(alpha‐c), and beta transitions observed agree with values taken with more complex, time‐consuming apparatus.
The low pressure pyrolysis of newsprint
Authors: Agrawal Ravindra K. , McCluskey Richard J.
Published: April 2003

The isothermal pyrolysis of 100 mg samples of shredded newsprint, both untreated and 1% HCI washed, at pressures below 1 torr has been examined between 260°C and 340°C. Pyrolysis occurs via a rapid initial reaction followed by a slower degradation that can be modeled as first order in remaining newsprint. The effect of a 1% HCI wash pretreatment is to increase the fractional tar yield by 40%, to decrease the gas yield by an equivalent amount, and to increase the extent of initial reaction. Arrhenius parameters have been obtained for rate constants describing both the initial and the slower degradation reactions for both untreated and acid washed newsprint.
Stabilization of gamma‐irradiated poly(vinyl chloride) by epoxy compounds. II. Production of hydroperoxides in gamma‐irradiated PVC–stabilizer mixtures
Authors: Lerke I. , Szymański W.
Published: April 2003

The concentration of hydroperoxides, produced in the process of radiolysis, was studied in γ‐irradiated PVC samples with 4% admixture of four epoxy stabilizers: diglycidyl ether of 2,2‐bis(4‐hydroxy‐3‐methyl phenyl)propane (I), styrene oxide (1,2‐epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8.) (VII). The results indicate that the process of radiation oxidation occurs in two stages. Only the stabilizers with benzene ring demonstrate the antioxidative action. The stabilizers VI and VII do not act as the antioxidants, and, moreover, as a consequence of their plasticizing properties, they facilitate the penetration of the oxygen to polymer. The epoxy groups have no influence upon the oxidation process, in the case of compounds VI and VII.
Radiation‐induced crystallinity changes in linear polyethylene: Influence of aging
Authors: Bhateja S. K.
Published: April 2003

A previous paper described an unusual crystallinity effect observed in ultrahigh molecular weight linear polyethylene (UHMW PE) and conventional high density polyethylene (HDPE). It was discovered that upon exposure to high energy radiation, these polymers experience a significant increase in the degree of crystallinity. The present paper describes another equally unexpected and surprising phenomenon observed in irradiated UHMW PE and HDPE. It was accidentally found that the irradiated polyethylenes exhibit an aging effect; their heat of fusion and hence their degree of crystallinity increases monotonically with the aging time (since initial irradiation) at ambient conditions. Surprisingly, the aging process in irradiated polyethylenes was observed to persist even after 31 months. The magnitude of the aging effect is a strong function of the initial molecular weight of the unirradiated polymers and the irradiation dose. The aging phenomenon could not be accelerated by thermal annealing. The exact mechanisms causing the aging phenomenon remain rather elusive at the present time, but possible reasons are explored.
Asphalts as inhibitors of radical polymerization
Authors: Bukowski Andrzej , Milczarska Teresa
Published: April 2003

The results of investigations concerning the effect of asphalts on radical polymerization of a monomer for model systems composed of styrene and two petroleum asphalts originated from two different crude oils: low sulphur nonparaffinic crude oil and medium sulphur paraffinic crude oil. Based on determination of styrene conversion in the radical polymerization process in the presence of asphalts, it was found that both asphalts act as inhibitors of this reaction. The inhibiting effect of asphalts is weakened by using higher temperatures and prolongation of polymerization time or application of greater initiator rates. On the basis of the analysis of group and elementary chemical composition of both asphalts as well as electron paramagnetic resonance, it was found that the inhibiting effect to radical polymerization is caused mainly by the presence of structures which are stable free radicals in character. The probability of inhibiting effect by sulphur compounds present in asphalts is also discussed.
Dehydrochlorinated poly(vinyl chloride‐g‐styrene). I. Effect of synthesis conditions
Authors: Mukherjee A. K. , Gupta Achla
Published: April 2003

Dehydrochlorinated poly(vinyl chloride) (DHPVC) was graft copolymerized with styrene monomer using benzoyl peroxide (Bz2O2) as free radical initiator, in vacuum. The effect of synthesis conditions such as time, initiator concentration, the ratio of monomer to polymer, and temperature on various grafting parameters was studied. On the whole, a maximum of 47 wt % polystyrene (PSt) in the graft (DHPVC‐g‐PSt) was obtained. PSt contents of graft copolymers determined by gravimetry, chlorine analysis, and UV spectroscopy have been compared. A “grafting from” mechanism has been proposed for the graft copolymerization.
Fibrous support for immobilization of enzymes. II
Authors: Ichijo Hisao
Published: April 2003

A series of adsorption experiments was conducted with varying initial enzyme concentrations. The observed values are compared with the results calculated from the adsorption equations based on Langmuir adsorption mechanism. The values of three parameters, adsorption equilibrium constant Ka, maximum value of adsorbed enzyme per unit mass of SFF, N, and forward adsorption rate constant ka, were determined from Langmuir adsorption equations and experimental data. In the initial enzyme concentration range below 100 (mg enz./dL), the simulated enzyme concentration vs. time curve agreed well with observed values. However, it was found that the adsorption in the higher concentration range was slow, and the corrected forward adsorption rate constant should be employed.
Dielectric studies of water in epoxy resins
Authors: Maxwell Ian D. , Pethrick Richard A.
Published: April 2003

Dielectric measurements are reported on amine‐cured epoxy resin samples over a frequency range from 200 Hz to 200 kHz and a temperature range from −60°C to 70°C as a function of molecular weight of the diglycidyl ether and water content. The effects of change of the molecular weight of the diglycidyl ether on the dielectric relaxation are small in comparison with the changes observed on the introduction of water into the matrix. Analysis of the data indicates the presence of cluster—free and bound—molecularly dispersed water. The former are presumed to be found in voids and cavities which arise in curing powder samples. The conductivity of the water‐doped samples reflects the mobility of the water and is compared with the predictions of theories for amorphous materials.
The use of a densitometer as a detector for gel permeation chromatography
Authors: Boyd Darcy , Narasimhan Venkataraman , Huang Robert Y. M. , Burns Charles M.
Published: April 2003

A commercially available densitometer, DMA 60 (Anton Paar, Austria), in combination with a Model DMA 602‐W flow cell was used as a detector in a Waters Model 200 GPC equipped with differential refractive index and ultraviolet absorbance detectors. The density measuring cell was thermostatted to ±0.004°C and the sample injection concentration was 1.5 mg/mL. Polystyrene samples of molecular weights ranging from 9000 to 860,000 were used. The optimum period was found to be 10,000 oscillations, a setting which gave good resolution and a sufficient number of data points to define the chromatogram. The molecular weight averages calculated using the density outputs compared well with those obtained through the conventional UV detector. A sliding average technique was applied to the densitometer data for reducing the baseline noise. It was found that concentrations as low as 1.0 mg/mL (≈0.114%) could be used to obtain densitometer chromatograms that yield molecular weight averages comparable to those obtained from the ultraviolet detector. This densitometer thus appears suitable to be used as an additional GPC detector for routine analyses.
The reaction of glass fiber with diisocyanate and its application
Authors: Yosomiya Ryutoku , Morimoto Kiyotake , Suzuki Toshio
Published: April 2003

The synthesis of reactive glass fiber having isocyanate groups were tried by reacting silanol groups on the surface of glass fiber with diisocyanate compounds. The effect of solvent, influence of the structure of diisocyanate, and effect of amine catalyst were examined, and results that the reactivity increased with increasing the polarity of solvent, when aromatic diisocyanate was used, and with increasing the basicity of amine catalyst were obtained. Further, glass fiber having isocyanate groups was addition‐reacted with diol, and diol added glass fiber was synthesized.
Determination of the absolute molecular weight of a styrene–butyl acrylate emulsion copolymer by low‐angle laser light scattering (LALLS) and GPC/LALLS
Authors: Malihi Farrokh B. , Kuo Cheng‐Yih , Provder Theodore
Published: April 2003

The application of low‐angle laser light scattering (LALLS) and combined GPC/LALLS for the measurement of absolute molecular weight distribution of a styrene–butylacrylate (30/70) emulsion copolymer is discussed. From the static light scattering measurements in four different solvents, i.e., toluene, tetrahydrofuran (THF), methyl ethyl ketone (MEK), and dimethylformamide (DMF), the true weight average molecular weight (Mw) and heterogeneity parameters are determined. The apparent Mw obtained from the static measurement in THF was in good agreement with the Mw determined from the multiple solvent analysis, suggesting the validity of using THF as the mobile phase in the combined GPC/LALLS analysis.
Influence of tacticity on the thermal degradation of PVC. VI. New advances in the degradation process through the behavior of modified PVC samples
Authors: Martínez G. , Mijangos C. , Millán J.
Published: April 2003

Three PVC samples having different tacticities, as well as the products resulting from their reaction with sodium thiophenate, which was previously found to occur selectively by some definite isotactic conformations, were degraded at 180°C in solid state up to 0.3%. In agreement with prior works, the stability of the substituted polymers was shown to be higher as the substitution extent increased up to a definite value, which depends on the overall isotactic content of the starting materials. On the other hand, the found changes in polyene distribution for the degraded samples with the substitution extent, as followed by UV‐visible spectroscopy, demonstrate that the specific bands at 393, 416, and 437 nm, which are known to be characteristic for the most unstable PVCs, arise from the lability of some chlorine atoms located at GTTG′ (or TTTG) conformations, as prior results suggested. On the basis of the so‐obtained correlation between the content of some isotactic triads (especially the GTTG′) and both the thermal instability and the formation of the above‐indicated specific polyenes, new advances in the degradation mechanism are proposed.
Engineering plastics from lignin II. Characterization of hydroxyalkyl lignin derivatives
Authors: Glasser Wolfgang G. , Barnett Charlotte A. , Rials Timothy G. , Saraf Vasudev P.
Published: April 2003

Several types of hydroxyalkyl lignin derivatives were synthesized from milled wood, organosolv, steam explosion, acid (H2SO4) hydrolysis, and kraft lignin with ethylene oxide, propylene oxide, and butylene oxide by either batch reaction in toluene at 180°C using KOH as catalyst, or in aqueous alkali at room temperature. The isolated derivatives were characterized in terms of their chemical structures by H‐NMR and FT‐IR spectroscopy. Thermal properties were determined by differential scanning calorimetry. Molecular weights were measured by gel permeation chromatography on polystyrene/lignin model compound calibrated high pressure μ‐spherogel columns. Solubilities in various organic solvents spanning a solubility parameter (δ) range from 9.3 to 14.5 and a hydrogen bonding index (γ) range from 1.5 to 18.7 were tested using UV280 absorption of solutions of up to with degrees of substitution of between 1 and 2.6 (except for ethylene oxide derivatives which were higher) and with lignin contents of around 60%. The drastic reduction of glass transition temperature of between 50° and 100° is explained with increased free volume of the copolymer and with disruption of hydrogen bonds involving especially phenolic hydroxy groups. The greatly enhanced solubility in organic solvents indicates absence of the gel structure typical of network polymers. No molecular breakdown was observed as a consequence of oxyalkylation. The derivatives had molecular weights (Mw) of between 2000 and 50,000 at dispersity factors of between 2.5 and 25. The derivatives seem to constitute useful prepolymers for thermosetting engineering plastics.
Preparation of macroreticular chelating resins containing dihydroxyphosphino and/or phosphono groups and their adsorption ability for uranium
Authors: Egawa Hiroaki , Nonaka Takamasa , Ikari Masanori
Published: April 2003

The macroreticular chelating resins (RSP, RSPO, RCSP, and RCSPO) containing dihydroxy‐phosphino and/or phosphono groups were prepared and their adsorption capacity for UO22+ and the recovery of uranium from sea water were investigated. RSP and RCSP were prepared by phosphorylation of macroreticular styrene–divinylbenzene copolymer beads and the chloromethylated copolymer beads, respectively. RSPO and RCSPO were prepared by oxidation of RSP and RCSP, respectively. The order of recovery of uranium from sea water with these four resins is as follows: RCSPO ⋍ RCSP > RSPO > RSP. The adsorption of uranium in sea water was not only affected by the chemical structure, but also by physical structure of the resins. Uranium absorbed on the resins was eluted with 0.25 ∼ 1 mol·dm−3 Na2CO3 or NaHCO3 solution by batch and column methods. The average recovery ratios of uranium from sea water with Na‐form and H‐form RCSP on 10 recycles were 84.9% and 90.5%, respectively, when 20 dm3 of sea water was passed through the column (resin 4 cm3, 10 mm ϕ × 50 mm) at the space velocity of 60 h−1. RCSP has a high physical stability and resistance against acid and alkali solution.
Accelerated degradation of poly(vinyl chloride) (PVC) monitored by photoacoustic spectroscopy
Authors: Abu‐Zeid M. E. , Nofal E. E. , Marafi M. A. , Tahseen L. A. , Rasoul F. A. Abdul , Ledwith A.
Published: April 2003

Poly(vinyl chloride) film shows substantial changes in its photoacoustic absorption spectra (PAS) on either irradiation or heating in the presence of O2 or N2. These spectral changes are due to the conjugation structures and carbonyl (group formation), formed during photo and thermal degradation. In this paper interpretations of the PAS and of the decomposition mechanism of PVC are presented.
Commercial antioxidants as photostabilizers for butadiene rubber
Authors: De Paoli Marco‐A. , Schultz G. W. , Furlan Luiz T.
Published: April 2003

In this work we have studied the stabilizing effect of several commercially available antioxidants on the free‐radical photooxidation of butadiene rubber. Two kinds of stabilizers were investigated; hindered phenols: 2,4‐di‐t‐butyl‐p‐hydroxytoluene, octadecyl‐3‐(3,5‐di‐t‐butyl‐4‐hydroxyphenyl)‐propionate and 2,4‐bis(octylthio)‐6‐(4‐hydroxy‐3,5‐di‐t‐butylanilino)‐1,3,5‐triazine; and amine stabilizers: N‐isopropyl‐N′‐phenyl‐p‐phenylenediamine and N‐(1,3‐dimethylbutyl)‐N′‐phenyl‐p‐phenylenediamine. Their stabilizing effect is mostly produced by scavenging the peroxy radicals formed during the initial steps of the photodegradation process. We also tested tri(nonylphenyl)phosphite associated with the phenoltriazine stabilizer. Of the additives studied in this work, octadecyl‐3‐(3,5‐di‐t‐butyl‐4‐hydroxyphenyl)propionate was the most effective photostabilizer for butadiene rubber.
Preparation of carbon fibers from syndiotactic 1,2‐polybutadiene
Authors: Ashitaka Hidetomo , Kusuki Yoshihiro , Yamamoto Shuji , Ogata Yoshiaki , Nagasaka Akira
Published: April 2003

Carbon fibers having good mechanical properties were produced from syndiotactic 1,2‐polybutadiene (s‐PB). Melt‐spun s‐PB fibers were made infusible by oxidation, irradiation, or treatments with Lewis acids, protonic acids, or peroxides. The infusibilized fibers were dehydrogenated with oxygen, chloranil, or sulfur and then carbonized. The preparative method by the AlBr3–sulfur–heat treatment process gave carbon fibers with good mechanical strength in a high yield. A filaments bundle was immersed in a benzene solution of AlBr3 (2g/100mL) at 42°C for 78 min under tension, washed with methanol, and then immersed in molten sulfur at 275°C for 14 min. After the adhering sulfur was purged with nitrogen at 290°C for 7 min, the bundle was heated up to a temperature of 700–3000°C under tension in a flow of nitrogen or argon for a few minutes. Carbon fibers heated to 1400°C were obtained with the tensile strength of 16.6 t/cm2 and the modulus of 1420 t/cm2 in a carbon yield of 82% and strain‐graphitized fibers at 3000°C with 20 t/cm2 and 4010 t/cm2 in 70%.
Chemical kinetics and diffusion in poly(butylene terephthalate) solid‐state polycondensation: Experiments and theory
Authors: Gostoli C. , Pilati F. , Sarti G. C. , Di Giacomo B.
Published: April 2003

Postpolymerization was obtained in solid PBT sheets, by annealing in a dry nitrogen stream at 214°C. After different reaction times, the samples were cut into thin slices. The Mw profile within the sample was obtained through intrinsic viscosity measurements in a phenol–TCE mixture. At each location inside the sample, the [η] vs. time curve typically shows a maximum, which is rather broad at the midplane and much sharper at the external surface. The phenomenon was mathematically described by accounting for both diffusion and chemical reactions within the slab; five simultaneous chemical reactions have been considered. The observed behavior is found to be essentially due to two competing processes, i.e., the diffusion of the low molecular weight species generated during the polycondensation and the thermal degradation reaction. The model predictions are compared with the experimental data showing a satisfactory agreement.
Mark–Houwink equation and GPC calibration for linear short‐chain branched polyolefines, including polypropylene and ethylene–propylene copolymers
Authors: Scholte Th. G. , Meijerink N. L. J. , Schoffeleers H. M. , Brands A. M. G.
Published: April 2003

The reduction in molecular dimensions due to the presence of short side chains in otherwise linear polyolefins can very simply by calculated by assuming that the configuration of the main chain is not influenced by the side chains. This enables us to express the intrinsic viscosity–molar mass relationship as a function of the mass fraction of side chains (S): [η] = (1 − S)α+1KPEMνα and, with use of the universal calibration principle, to convert the GPC calibration for purely linear polymers samples into the calibration for short‐chain branched polymers: M* = (1 − S)M. Experimental data from literature on short‐chain branched poly‐ethylenes, and our own data on ethylene–propylene copolymers are used to verify the above assumption. It appears that the experimentally found relations between [η], Mw and M*w (GPC) within the usual accuracy justify this approach.
Transport and related properties of paint films. II. Dynamic mechanical properties and humidity effects
Authors: Wedgewood Alan R. , Seferis James C. , Beck Theodore R.
Published: April 2003

A systematic four‐stage investigation of eight unpigmented coating formulations, including three vinyl, two polyurethanes, and three epoxy systems was done to provide baseline structural information upon which an improved understanding and an optimization of protective coatings can be founded. First, the results from dynamic mechanical measurements are provided and discussed for the base polymer component in each coating system. Second, the effects of humidity on the dynamic mechanical properties of these base polymers were determined at room temperature. The extent of property degradation was monitored by calculating the Tg depression with increased humidity, assuming a temperature–humidity superposition. The extent of degradation, as monitored by the Tg, was found to correlate directly with the level of hydrogen bonding in these coatings. Third, the influence of typical coating additives (a TCP plasticizer and a rosin hardener) on the properties of two of the vinyl coating systems was investigated. In the final stage, the synergistic effects of absorbed moisture and these additives on the coatings properties were investigated at room temperature. Increases in the concentration of these additives was found to magnify the degradation effect of increased humidity. This magnified degradation has been assigned to increased water absorption with increases in the concentration of either of these additives.
Mechanisms of antioxidant action: C–nitroso compounds as UV stabilizers for polypropylene
Authors: Chakroborty K. B. , Scott G. , Yaghmour H.
Published: April 2003

It is shown that nitroso‐tert‐alkanes are highly active UV stabilizers which become at least partially chemically attached to polypropylene during processing. The aromatic nitroso compounds are less effective as light stabilizers but are more effective than their alkyl analogues as thermal oxidative stabilizers. Mechanisms are proposed to account for the antioxidant activity of the nitroso compounds and their ability to cause crosslinking of the polymer during processing.
Kinetics of transesterification of dimethylene terephthalate with ethylene glycol
Authors: Datye Keshav V. , Raje Hemant M.
Published: April 2003

There is a disagreement about the order of reaction of transesterification of DMT with EG. The reactivity of the two ester groups is not compared yet. The transesterification of DMT and MHET is studied to establish the kinetics of the process. Attempts are made to treat the kinetic data on a mathematical model for third‐order reaction.
Investigation of amino acid composition in the crystalline region of silk fibroin
Authors: Nadiger G. S. , Bhat N. V. , Padhye M. R.
Published: April 2003

Accurate estimation of amino acids composition has been carried out for hydrolysates of four varieties of Indian silks, viz., Mulberry, Tasar, Eri, and Muga. These studies have revealed that the hydrolysate (hydrofibroin or crystalline region) in the case of Mulberry consists of glycine, alanine, and serine, whereas in the case of Tasar, Eri, and Muga, it is found to be mainly alanine. Other amino acids were also found to be present in the hydrolysate of these silks. But, the quantities present in each case were found to be negligible when compared to those amino acids cited above. Furthermore, these results are in conformity with the structure elucidation made by infrared spectral studies and x‐ray diffraction.
Effect of degree of crosslinking on water transport in polymer microparticles
Authors: Robert Christian C. R. , Buri Pierre A. , Peppas Nikolaos A.
Published: April 2003

The water transport in microparticles of poly(2‐hydroxyethyl methacrylate) crosslinked with small amounts of ethylene glycol dimethacrylate was investigated as a function of time. Dynamic swelling curves were obtained and analyzed with a simple, empirical, exponential expression, where the exponent n indicates the mechanism of water transport. It was determined that the mechanism changed from Fickian to non‐Fickian transport as the nominal crosslinking ratio increased from X = 0.007 to X = 0.124 mol EGDMA/mol HEMA. Smaller particles attained their equilibrium swelling value faster. The velocity of the penetrant front was determined with optical microscopy, and it was found to decrease from 22.2 to 11.2 μm/min as the crosslinking ratio increased.
Double exposure stabilization of positive photoresist
Authors: Yanazawa Hiroshi , Hasegawa Norio , Douta Kikuo , Hashimoto Norikazu
Published: April 2003

Positive photoresists appeared to be the most promising material in VLSI microfabrication for ten or more years from now. Thus, processing know‐how needs to be accumulated continuously. This work deals with thermal characteristics of positive photoresist. The following facts were declared experimentally. The quinone diazide, photosensitizer, was thermally decomposed at around 140°C to release N2. Simultaneously the surface layer of resist film was changed into innert state, called as ‘husk’, with low gas permeability and high chemical resistance. These thermal changes in resist film affect the photoresist to SiO2 adhesion. In this work a noble process, named double exposure stabilization, is developed to get sufficient chemical resistance and good adhesion simultaneously.
Stabilization of nigeria natural (havea) rubber with bound antioxidant added as masterbatch
Authors: Kolawole E. G. , Ebi Godwin
Published: April 2003

Nigeria natural rubber concentrates in a newly synthesized antioxidant were added as conventional additives for normal natural rubber. The natural weathering, thermal and photooxidative protective performance of the adduct were examined by measurement of the carbonyl index and induction periods. From the results obtained, it is concluded that the addition of this new antioxidant in the form of masterbatch appears to be a better practical way of incorporating it into natural rubber simply by dilution of natural rubber. The bound stabilizers were found to be resistant to leaching.
Synthesis of statistical networks from liquid polybutadiene. V. Synthesis and adhesive properties of 1,2‐polybutadiene networks
Authors: Friedmann G. , Brossas J. , Widmaier J. M.
Published: April 2003

A series of 1,2‐polybutadiene networks was prepared either by endlinking reaction of telechelic liquid precursors or/and by crosslinking with disilyl compounds. Transparent materials were obtained and used as adhesives in glass assembly mainly. The shear resistance at break was found to be higher compared to conventional vulcanized elastomers.
The viscoelastic properties of rubber–resin blends. II. The effect of resin molecular weight
Authors: Class J. B. , Chu S. G.
Published: April 2003

In blends of rubber and low molecular weight resins, the compatibility of the system controls the viscoelastic properties and ultimately the performance of the composition as a pressure sensitive adhesive. The effect of the resin molecular weight on compatibility was examined by studying rubber–resin blends prepared from resins which represent a range of molecular weights. Viscoelastic properties were measured using a mechanical spectrometer on 1:1 blends of rubber and a series of polystyrene resins and poly(vinylcyclohexane) resins. Based on plots of G′ and tan δ vs. temperature, blends of natural rubber and polystyrene resin show incompatibility at resin Mw of about 600 and above. Blends of natural rubber and poly(vinyl cyclohexane) are incompatible at resin Mw of about 1800, but are compatible at Mw of about 650. Blends of styrene–butadiene rubber and polystyrene resins are compatible at resin Mw of about 650 but appear to contain a low volume incompatible phase at Mw of about 900. Therefore, the compatibility of a rubber–resin blend depends upon the molecular weight of the resin. Even systems expected to be compatible will show evidence of incompatibility as the molecular weight of the resin is raised above some limiting value.
Solvent permeation in plasma‐fluorinated polyethylene
Authors: Corbin G. A. , Cohen R. E. , Baddour R. F.
Published: April 2003

Liquid‐phase sorption data are reported for the toluene–polyethylene system. The effects of fluorine plasma and inert‐gas plasma treatments of the polymer surface were investigated. The presence of a fluorinated surface layer reduces initial solvent permeation rates, but the enhanced barrier property is lost when irreversible morphological changes occur during polymer swelling. A combination of chemical and morphological factors appears to be responsible for the observed temporary reduction in permeability; crosslinking of surface macromolecules was not a significant factor for the particular cases investigated in this work.
Carbon‐13 NMR characterization of DGEBPA epoxy resins
Authors: Fleming William W.
Published: April 2003

Carbon‐13 nuclear magnetic resonance (NMR) has been used to investigate the structure and character of diglycidyl ether of bisphenol A (DGEBPA) epoxy resins more thoroughly than previously reported in the literature. It is shown that spectra, when run under quantitative conditions, can detect the loss of epoxides at the end groups by reactions such as hydrolysis. The products of acid hydrolysis of a DGEBPA resin are observed and assigned. It is further shown that the possibility of epoxide hydrolysis and impurities or structural irregularities can lead to inaccuracies in epoxy equivalent weight (EEW) calculations using a previously reported methodolgy. A new method is employed which can take into account loss of end group epoxides. Part of this new method consists of a measure of the epoxide to end group ratio (EER) which sheds light on the final possible quality of the cured resin. The EER value is shown to be in many ways more informative than the EEW measure which has the built‐in assumption that there is an epoxide group for each end group.
Pulsed NMR study on the silica‐filled rubber systems
Authors: Ito Masayoshi , Nakamura Takehusa , Tanaka Koji
Published: April 2003

Proton spin–spin relaxation time has been measured by the pulsed NMR technique for the bound rubbers extracted from both silica‐filled polyisoprene and polybutadiene composites. Two relaxation times T2t (short) and T2l (long) are observed for all samples. They are ascribed, respectively, to the relaxation of the tightly and loosely bound rubber components. When the silica filled polybutadiene composite is heat treated at 120°C, loosely bound rubber is preferentially formed, which leads to the increase in the total bound rubber fraction in the composite. During the heat treatment of silica‐filled polyisoprene composite, a part of the loosely bound rubber phase is transformed into tightly one, and simultaneously the chain mobilities of both phases become more constrained state. These changes are accompanied by the degradation of polyisoprene molecules probably due to the strong chemical interaction of silanol group and rubber molecules. At a prolonged heat treatment, the fraction of total bound rubber in the composite decreases as a result of the degradation of the loosely bound rubber molecules.
An investigation of the kinematics of stretch blow molding poly(ethylene terephthalate) bottles
Authors: Cakmak Mukerrem , White James L. , Spruiell Joseph E.
Published: April 2003

An experimental study of the kinematics of inflation of poly(ethylene terephthalate) (PET) parisons in a Corpoplast stretch blow molding process is reported. LVDT displacement transducers have been placed at various positions along the length and at the top of a specially designed and built mold. A six‐channel LVDT demodular circuit was built and attached to a minicomputer. Studies were conducted at 90 and 100°C at various pressures. Kinematic models were developed for the parison inflation, and stress fields along the deforming surface of the parison were computed using membrane theory.
Engineering plastics from lignin. VII. Structure property relationships of poly(butadiene glycol)‐containing polyurethane networks
Authors: Saraf Vasudev P. , Glasser Wolfgang G. , Wilkes Garth L.
Published: April 2003

Hydroxypropyl lignin‐based thermosetting polyurethanes containing polybutadiene (PBD) glycol soft segments (Mn of 2800 g M−1) were synthesized with excess hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI) by solution casting. Miscibility of the glycol with the lignin derivative was found to be poor as expected, and phase separation between the two polyol components in polyurethanes was detected by thermal and mechanical analysis, and by electron microscopy. This study examines the effect of concentration of polybutadiene glycol on the thermal and mechanical properties of the polyurethanes. The two‐phase network system displayed significantly different properties than either the poly(ethylene glycol)‐containing polyurethanes or their soft segment‐free counterparts described previously. Macrophase separation was observed at nearly all degrees of mixing and was found to affect thermal and mechanical properties. The glass transition temperature (Tg) of the lignin phase in the TDI‐based networks increased with poly(butadiene glycol) content rising from 3.6 to 71.4% of polyurethane, and this was attributed to the employment of a constant diisocyanate weight fraction which gave rise to a variable NCO/OH ratio and crosslink density. Distinct phase separation was evidenced by scanning electron microscopy (SEM) at above 3.6 and 7.1% glycol content for HDI‐ and TDI‐based films, respectively. The polyurethane films behaved like rubber‐toughened lignin networks when PBD was the discrete phase, and like lignin‐reinforced rubber when the lignin derivative was discrete. This behavior was evidenced by the Young's modulus decreasing from 2000 to 50 MPa and ultimate strain rising from 6 to greater than 150%, with soft segment content increasing from 0 to 71.4%.
Gas and vapor sorption in polymers just below Tg
Authors: Chiou J. S. , Maeda Y. , Paul D. R.
Published: April 2003

Generally, sorption isotherms for gases like CO2 in glassy polymers are concave to the pressure axis, whereas in the rubbery state these isotherms are linear for gases or sometimes convex to the pressure axis for more condensable vapors. Examples of CO2 isotherms are reported here that show at low pressure the curvature characteristic of glasses and then become linear at higher pressures. This is observed when the glass transition temperature Tg is not much greater than the observation temperature T, and plasticization of the polymer by sorbed CO2 causes Tg to become equal to T within the range of pressures employed in the isotherm measurement. For the sorption of vapors in glassy polymers, this can lead to sigmoidal isotherms, as discussed using an illustration from the literature.