bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of liquid mixtures by using polymer membranes. III. Water–alcohol separation by pervaporation through modified PAN membrane
Authors: Hu Chun‐Min , Chiang Wen‐Yen 
Published: April 2003

AbstractThe modification of polyacrylonitrile membrane with ethanolamine was carried out, and the permeation characteristics in pervaporation were examined using the aqueous alcohol solutions. In pervaporation of a water/alcohol solution, preferential permeation of water was observed for all these membranes because of the hydrogen‐bonding interaction. The selectivity of the modified polyacrylonitrile (PAN) membrane depended on operating temperature, but was independent on the thickness of the membrane. Furthermore, it was found that the membrane with more ethanolamine content had a higher affinity to water. The effect of feed concentration and the molecular size of the permeating species on the separation factor and permeation flux was also investigated.
Gel permeation chromatography of isotactic polypropylene using the cyclohexane–decalin solvent system
Authors: Ibhadon A. O. 
Published: April 2003

AbstractThe molecular weight distribution of iPP and its copolymers with ethylene have been studied using cyclohexane/decalin as eluent at 333 K. The fractionation of the polymers using the same solvent system was also investigated. Reproducible and reliable molecular weight distribution and averages have been obtained.
New peracid‐type polymeric initiator for radical polymerization
Authors: Hsiue Ging‐Ho , Perng Tirng‐Lair , Yang Jen‐Ming 
Published: April 2003

AbstractIn this study, a radiation‐induced copolymer, namely polyethylene‐g‐acrylic acid powder, was used, whose carboxyl groups can be oxidized to form a highly reactive polymer initiator. The activation energy for its decomposition is 22.4 kcal/mol. It was found that the peracid‐type polymeric powder was effective as an initiator for radical polymerization. It had high reactivity toward 2‐hydroxyethyl methacrylate (HEMA), which could be easily grafted onto the polymeric powder; also, the homopolymer could be obtained. The kinetic investigation indicated that this polymerization proceeded by a radial mechanism, and the overall activation energy of homopolymerization was 18.67 kcal/mol and the overall activation energy of bigraft polymerization was 17.35 kcal/mol. By using the peracid‐type polymeric powder as initiator for the copolymerization of methyl methacrylate with styrene, it was confirmed that the polymerization initiated by the peracid‐type polymeric powder was a radical reaction.
Flow injection analysis estimation of diffusion coefficients of pauci‐ and polydisperse polymers such as polystyrene sulfonates
Authors: Boyle William A. , Buchholz Richard F. , Neal John A. , McCarthy Joseph L. 
Published: April 2003

AbstractFlow injection analysis, often used for determination of diffusion coefficients of nonpolymeric substances, has now been applied to the characterization of pauci‐ and polydisperse polymers in solution. A relative method was found useful for obtaining moderate quality evaluations of diffusion coefficients and related parameters of polymers. The width at half‐height W1/2 of the trace peak is found to be proportional to the number average molecular weight M̄n of pauci‐ and polydisperse polymers, allowing estimation of M̄r and diffusion coefficients. For sodium polystyrene sulfonates at substantially infinite dilution in 1.0 g L−1 Na2SO4, a linear relation has been observed between the logarithms of the molecular weight M̄n and the mean diffusion coefficient D in the M̄n range of 1000–90,000 g mol−1 or the D range of 30 × 10−7 to 2 × 10−7 cm2 s−1.
Thermal stability of nonionic polyoxyalkylene surfactants
Authors: Santacesaria E. , Gelosa D. , Di Serio M. , Tesser R. 
Published: April 2003

AbstractNonionic surfactants are largely employed in the pharmaceutical, cosmetic, and textile industry. The sensitivity of polyoxyethylene chains to autoxidation is studied because it is responsible for unpleasant effects such as discoloration, degradation of products, and unpleasant odors. In the present work, thermal stability of polyoxyethylene and polyoxyethylene/propylene nonionic surfactants has been studied by employing together differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). First of all, the thermal stability of three monodispersed surfactants (laurilic alcohol plus 4, 6, or 8 EO units) has been studied. Then, the behavior of these products has been compared with those of commercial surfactants containing the same alkyl chain coupled with idrophylic chains of different lengths, containing EO units alone or both EO and PO. The effect of the alkyl chains has also been examined in the same way. In all cases, autoxidation starts at about 100°C with a net heat production proportional to the number of adducts and equal to about (1.5–1.7) × 105 J/adduct. Heat evolution stopped at about the same temperature, independently of the hydrophylic chain length. A residual of 10–30% by weight decomposes, at higher temperatures, with a very small heat evolution. The interpretation of these and other phenomena observed conclude the paper.
High‐temperature continuous bulk copolymerization of styrene and acrylic acid: Thermal behavior of the reactants
Authors: Spychaj Tadeusz , Hamielec Archie E. 
Published: April 2003

AbstractThe behavior of the monomers: styrene (St) and acrylic acid (AA) during the process of thermally initiated bulk copolymerization realized in a continuous stirred tank reactor (CSTR) is discussed in this work, on the basis of results obtained from experimental work carried out by the authors and data available from literature. GPC, GC, IR, and NMR techniques were used to examine the volatile oligomers released from the raw St–AA polymers. The mechanism of the thermal initiation of polymerization in the system under investigation is also discussed. Polymer degradation reactions in the vicinity of the ceiling temperature Tc, chain transfer reactions, and secondary reactions of carboxylic groups in high temperatures have also been considered. The behavior of the St–AA polymers during derivatographic tests in the temperature range: ambient−400°C, conducted in atmospheric air, was also evaluated. Experimental conditions, in which deep destruction of the product during the copolymerization process could be avoided, were established.Knowledge of these conditions is important from a practical point of view.
Spectroscopic study on poly(methyl methacrylate) doped with metal dithizonates
Authors: Moharram M. A. , Shabaka A. A. , Khafagi M. G. 
Published: April 2003

AbstractThe IR and UV spectra of poly(methyl methacrylate) (PMMA) doped with metal dithizonate were investigated. Films of the doped samples were heated in air at various temperatures from 25 to 140°C for 2 h. Other films were also exposed to UV irradiation. The doped samples were treated with iodine. The experimental results provided strong evidence that certain weak reaction occurs between the dopants and the polymer, and the rate of reaction depends on the concentration of the dopant and the nature of the metal ions. It was found that heat treatment of the doped films induces considerable changes in the intensities of their IR bands. The magnitude of these changes depends also on the concentration and the nature of the metal ion. Moreover, the results proved that exposure of the doped films to UV irradiation has no effect on their absorption spectra. Furthermore, the treatment of the doped samples with iodine causes considerable changes in their UV absorption spectra.
The use of aqueous alkaline hydrolysis to reveal the fine structure of poly(ethylene terephthalate) fibers
Authors: Collins Martha J. , Zeronian S. Haig , Semmelmeyer Mary 
Published: April 2003

AbstractThe fine structure and physical properties of bright and semidull poly(ethylene terephthalate) (PET) fibers were investigated as successive layers of the polymer were removed by hydrolysis using aqueous solutions of sodium hydroxide up to weight losses of 90 and 68%, respectively. For both types large changes in molecular weight distribution did not occur, although as weight loss increased, the density of the remaining fiber increased. Alterations in fine structure with weight loss were also observed by thermal analysis. Greater strength loss with decreasing weight occurred for the semidull fiber than for the bright sample. Larger pits formed on the surface of the hydrolyzed semidull fibers than on the surface of the bright products. This observation is attributed to the titanium oxide present in the semidull fibers. It was also noted that as the density of the bright PET samples was increased by heatsetting, the rate of hydrolysis decreased.
Arylidene polymers. VI. Gamma irradiation effects on the electrical conductivity behavior, IR absorption spectra, and DSC measurements of some new synthesized poly(arylidenecycloalkanones)
Authors: Abd‐Alla M. A. , Mahfouz R. M. 
Published: April 2003

AbstractGamma irradiation effects on the electrical conductivity behavior of some new synthesized poly(2,5‐arylidenecyclopentanone) 1, poly(2,6‐arylidenecyclohexanone) 2, and their co‐polymers 3, have been investigated. Thermal studies over the temperature range 300‐500 K showed that the conductivity behavior follows a two‐term Arrhenius‐type equation. The first term has a small activation energy and predominates at lower temperature (extrinsic region), and the second term with higher activation energy predominates at higher temperatures (intrinsic region). Change in the activation parameters with the change in the γ‐ray dose and the nature of the polymers are discussed. The IR absorption spectra showed a decrease in the intensity of most bands of the γ‐irradiated samples. A mechanism based on the formation of trapped free radicals and their recombination has been suggested. DSC measurements indicated that the crystallization and the melting temperature transitions decreased in size considerably with the increase in the γ‐ray dose until they nearly disappeared at higher γ‐ray dose.
Surface and interfacial FTIR spectroscopic studies of latexes. III. The effects of substrate surface tension and elongation on exudation of surfactants
Authors: Evanson Kevin W. , Urban Marek W. 
Published: April 2003

AbstractThis paper focuses on the effect of the substrate surface tension and mechanical elongation of EA/MAA latex films on the ionic and nonionic surfactant mobility. Although the mobility of anionic surfactants is inherently sensitive to the substrate surface tension, nonionic surfactants appear to remain uniformly distributed across the latex film. This behavior is attributed to the enhanced compatibility with the copolymer latex. Mechanical elongation of the latex films enhances surfactant exudation to the surface due to the increased surface energy of the film forcing surfactants to the latex surface.
Influence of glycine on the kinetics of the graft copolymerization of acrylonitrile onto jute fibers initiated by ceric ion
Authors: Nayak N. C. , Das H. K. , Singh B. C. 
Published: April 2003

AbstractA study of the influence of glycine on the graft copolymerization of acrylonitrile (AN) onto jute fiber using ceric ion has been made. The effect of concentrations of monomer, Ce (IV), and glycine on graft yield have been studied. In addition, the effect of time, temperature, acid, and the amount of jute fiber on graft yield has been investigated. On the basis of experimental findings, a qualitative reaction mechanism has been proposed and the optimum condition for effective grafting has been suggested.
Permeability of silicone polymers to hydrogen
Authors: Bhide B. D. , Stern S. A. 
Published: April 2003

AbstractPermeability coefficients, P̄, for H2 in 10 different types of silicone polymer membranes were measured in the temperature range of 10.0–55.0°C and at pressures up to 100 psig (∼6.8 atm). The values of P̄ decrease slightly with increasing Δp, the pressure difference across the membranes. The permeability of silicone polymers to H2 increases with an increase in temperature; the values of the energy of activation for permeation are in the range of 1.4–4.3 kcal/mol. The substitution of different functional groups in the backbone and side chains of silicone polymers has similar effects on the permeability of the polymers to H2 as observed in earlier studies with other light gases. P̄ for H2 decreases with an increase in the bulkiness of the substituted functional groups. The substitution of SiO bonds with stiffer SiC bonds in the backbone chains also results in a considerable decrease in permeability.
Plasma surface treatments on carbon fibers. II. Mechanical property and interfacial shear strength
Authors: Yuan L. Y. , Shyu S. S. , Lai J. Y. 
Published: April 2003

AbstractCarbon fiber are surface treated by oxygen, argon, and styrene plasma to study the effects on fiber strength and interfacial shear strength with PPS resin. Interfacial shear strength between carbon fiber and high melting temperature thermoplastic resins is successfully measured with the microbond pull‐out test with the help of scanning CO2 laser beam which solved the difficulties in preparing PPS microspheres. Tensile tests show that etching by oxygen plasma and deposition with plasma–PS increase strength of the fibers in some cases. ESCA spectra deconvolutions demonstrate that the improved interfacial strength is strongly related to the hydroxyl, ether, or aromatic groups on the surface. On the other hand, hydrocarbon segments are detrimental to the interface. Surface area and roughness have little influences on the interfacial strength of carbon fiber/PPS composites.
A DSC study of curative interactions. IV. The interaction of tetramethylthiuram disulfide with ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractThe interaction of combinations of sulfur, tetramethylthiuram disulfide (TMTD), ZnO, and stearic acid were investigated by differential scanning calorimetry in the absence of rubber. TMTD decomposed partially to tetramethylthiuram monosulphide on liquefaction. Sulfur and TMTD reacted at vulcanization temperatures, and although the exact composition of all the products was not established, several features involving DSC and HPLC analysis were interpreted in terms of the formation of tetramethylthiuram polysulfides (TMTP). TMTD decomposed much faster to volatile products such as Me2NH, CS2, and CS when heated in the presence of stearic acid. Contrary to literature reports on the facile reaction of TMTD and ZnO to yield zinc perthiomercaptides (or zinc dimethyldithiocarbamate), the TMTD/ZnO reaction was found to be extremely sluggish under a variety of conditions. In the presence of sulfur, too, the TMTD/ZnO reaction was of negligible importance. It was inferred that several reactions occurred concurrently on heating a TMTD/stearic acid/ZnO system. These reactions were not observed for the sulfur/TMTD/stearic acid/ZnO mixture per se, but, instead, the stearic acid/ZnO reaction was very prominent. The formation of zinc stearate occurred at temperatures as low as 77°C in the quadruple system. TMTD and zinc stearate were virtually unreactive at vulcanization temperatures. None of the reactions involving ZnO could be attributed to the formation of a zinc perthiomercaptide, generally accepted to be a precursor in thiuram vulcanization.
Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. I. Structure–property relationships
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo 
Published: April 2003

AbstractFlexural test specimens were injection‐molded from polypropylenes added with 0.5 wt % of calcium carbonate, talc, p‐tert‐ dibutyl‐benzoic acid monohydroxy aluminum, or p‐di‐methyl‐benzylidene sorbitol under cylinder temperatures of 200–;320°C. Properties such as flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, hardness, and mold shrinkage and higher‐order structures such as crystalline texture, crystallinity, a*‐axis‐oriented component fraction, and degree of crystalline orientation were measured and structure–property relationships were studied. By the addition of crystallization nucleators, the flexural modulus, flexural strength, heat distortion temperature, hardness, and mold shrinkage were increased and Izod impact strength was decreased. The degrees of crystalline orientation such as the orientation fraction OF and c‐axis orientation function fc were increased by the addition of nucleators. The degree of the increase was higher as the crystallization temperature was higher. Close relationships were observed between some properties and the degrees of crystalline orientation.
IR and X‐ray diffraction studies of raw and chemically treated pineapple leaf fiber (PALF)
Authors: Saha S. C. , Ray P. K. , Pandey S. N. , Goswami K. 
Published: April 2003

AbstractIR and X‐ray diffraction studies have been carried out on raw and chemically treated pineapple leaf fiber (PALF). The degree of crystallinity, as found by X‐ray diffraction and the crystallinity index as found by infrared methods, decreases on treatment with NaOH and NaClO2 solutions. The decrease of crystallinity with lower concentration of NaOH is attributed to the conversion of intermediate or semicrystalline regions to amorphous ones and with higher concentration to structural changes and with NaClO2 solution to the disorientation caused due to removal of cementing material lignin.
Graft copolymerization of vinyl monomers onto chitin with cerium (IV) ion
Authors: Kurita Keisuke , Kawata Mitsuo , Koyama Yoshiyuki , Nishimura Shin‐Ichiro 
Published: April 2003

AbstractGraft copolymerization of vinyl compounds onto chitin was studied, and an efficient and reproducible procedure has been established, cerium (IV) being used as the initiator. The reactions with acrylamide and acrylic acid onto powdery chitin were carried out under various conditions to elucidate the polymerization behavior in terms of grafting percentage. The amount of cerium (IV) affected the polymerization most strikingly, and grafting percentages showed maxima with suitable amounts of initiator for both the monomers. As a solvent water proved to be superior to aqueous nitric acid except the reaction with a small amount of initiator. Under appropriate conditions, around 240 and 200% grafting percentages were achieved for acrylamide and acrylic acid, respectively. The resulting graft copolymers showed much improved affinity for solvents and hygroscopicity compared to the original chitin.
Streaming potential of microporous membranes made from homogeneously functionalized polysulfone
Authors: Hinke Ekkehard , Staude Eberhard 
Published: April 2003

AbstractMicroporous membranes were prepared from chemically modified polysulfone. The substitution of the polysulfone was performed in solution using reactions known from polymer modification such as halomethylation, aminomethylation, and lithiation. Membranes can be prepared directly from halomethylated polysulfones which are consecutively converted heterogeneously in a second step to the final functionalized form. Sometimes, two‐step reactions are necessary to yield the polymers from which the membranes were cast. In those cases where the reactions change the charge of the polymer, the success of the reaction can be demonstrated by streaming potential measurements. The advantage of this analytical method lies in the fact that the intact membrane is investigated.
The effect of molecular weight on the cross section and properties of polyacrylonitrile precursor and resulting carbon fiber
Authors: Tsai Jin‐Shy , Lin Chung‐Hua 
Published: April 2003

AbstractIn this study, we investigated the effect of molecular weight in the range 1.65−4.29 × 105 (Mw) on the cross section, surface, thermal, and mechanical properties of polyacrylonitrile (PAN) precursor and its resulting carbon fiber. From the results, it can be seen that the molecular weight, with the same solid content of polymer, changes from 1.65 × 105 to 4.29 × 105 and the cross section of PAN precursor changes from a circular shape with no notable grooves surface to a been shape with a surface containing deep and straight grooves. PAN precursor with higher molecular weight has a higher onset of exothermic temperature and a higher peak temperature, but has a higher aromatization index (AI value) due to its thin and flat cross section, which causes rapid cyclization during oxidation. An increase in molecular weight results in an increase in crystal size and preferred orientation and a decrease in average pore diameter. This decrease can improve the mechanical properties of PAN precursor and its resulting carbon fiber.
Dynamic mechanical properties of polystyrene–polyurethane blends
Authors: Theocaris P. S. , Kefalas V. 
Published: April 2003

AbstractFour polystyrene–polyurethane mechanical blends were prepared with 5, 10, 20, and 40% thermoplastic polyurethane, respectively. Their impact properties were compared with pure polystyrene and commerical types of impact polystyrene. The rheological properties of the blends were studied with DSC and dynamic mechanical spectroscopy. It was found that addition of softer polyurethane conglomerates embedded inside the polystyrene matrix, although increasing the toughness of the blend as expected from addition of the softer particulate, also increased the glassy region of the blends by shifting their Tgs to higher temperatures. A theory based on the interaction of phases was propounded explaining this phenomenon.
Fibers spun from blends of different molecular weights of polypropylene
Authors: Mahajan S. J. , Bhaumik K. , Deopura B. L. 
Published: April 2003

AbstractFibers spun from blends of small percentage of plastic grade polypropylene (HMPP) with fiber grade polypropylene (PP) are studied for drawing behavior. A factorial design of experiment is used for a two‐stage drawing process with variables, such as percent of HMPP component, first stage draw ratio and temperature, and second stage temperature. Optimization is carried out for breaking stress and modulus of drawn filaments. Breaking stress of up to 0.74 GPa and initial modulus of 7.34 GPa is possible by such an optimization process. These properties are observed for 6% HMPP blend composition. Heat setting of drawn filaments show little changes up to 140°C heat‐setting temperature. Large scale structural changes with rapid drop in mechanical properties is observed for 150‐160°C heat‐set samples.
The effect of additives, solvent type, and polymer concentration on macromolecule dimensions
Authors: Wood Hal , Sourirajan S. 
Published: April 2003

AbstractAn equation is derived to estimate the hydrodynamic volume occupied by a typical linear polymer molecule, knowing only the polymer molecular weight and concentration of polymer in the solution. This equation may be applied to solutions above a minimum polymer concentration. Accuracy of the equation is determined by comparing it to an established method of calculating macromolecule dimensions.Above dilute solution conditions, the volume pervaded by a macromolecule is affected mainly by the polymer molecular weight and concentration of polymer in the solution. Chain dimensions are generally unaffected by the type of polymer, solvent, or additive in the solution.
Effect of plasma treatments on wettability of polysulfone and polyetherimide
Authors: Asfardjani K. , Segui Y. , Aurelle Y. , Abidine N. 
Published: April 2003

AbstractExperimental results on plasma treatments of polysulfone and polyetherimide to improve the wettability of these polymers are presented. The plasma is characterized by optical emission spectroscopy. The wettability of the polymer surfaces were checked by contact angle measurements and ESCA is used to compare the surfaces before and after plasma treatment. Correlations between contact angle, concentration of oxygen at the surface, and optical emission intensity of the OH radical have been established. Optimization of operational plasma parameters leading to the best wettability of the treated samples is reported.