bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscoelastic and engineering properties of poly(vinyl chloride) plasticized with polycaprolactone‐based polyurethanes
Authors: Bandyopadhyay P. K. , Shaw M. T. 
Published: April 2003

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractSpecially 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractDehydrochlorinated 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

AbstractA 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

AbstractDielectric 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractThree 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

AbstractSeveral 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

AbstractThe 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

AbstractPoly(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

AbstractIn 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

AbstractCarbon 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

AbstractPostpolymerization 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.