bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. III. The permselectivity of the neutralized chitosan membrane and the relationships between its permselectivity and solid state structure
Authors: Mochizuki Akira , Amiya Shigetoshi , Sato Yoshio , Ogawara Hisashi , Yamashita Shuzo 
Published: April 2003

AbstractThe separation of water/alcohol mixtures through chitosan membrane neutralized by various acids was investigated. The permselectivity of the neutralized chitosan membrane was affected by the species of acids and, only when neutralized by polybasic acids, was a marked increase of the selectivity observed and a high selectivity maintained for ion free mixtures. The marked increase of the selectivity could be explained by the contraction of the “holes” produced by the thermal motion of polymer chains due to the conformation change of chitosan molecule caused by the neutralization. The conformation change was confirmed by the analysis of the solid state structure of the neutralized chitosan using CP/MAS 13C‐NMR.
Permeation and diffusion of environmental pollutants through flexible polymers
Authors: Britton Larry N. , Ashman R. Brian , Aminabhavi Tejraj M. , Cassidy Patrick E. 
Published: April 2003

AbstractPermeation and diffusion characteristics of high density polyethylene (HDPE), elasticized polyolefin, and polychloroprene membranes have been determined for various organic pollutants at 22 and 50°C. A standard ASTM permeation cell method was used to measure the permeation rate while an immersion/weight gain method was used to obtain the diffusion coefficient. Thickness‐dependent permeation rates were determined for HDPE membranes. An equimolar mixture of various permeants was also used to see the possibility of synergistic effects by combination of permeants. The experimental results are discussed in relation to the suitability of HDPE membranes in severe environments.
Treated aramid fibers as reinforcement in nonpolar matrices
Authors: Petsalas H. J. , Andreopoulos A. G. 
Published: April 2003

AbstractCrosslinked polyethylene finds extensive use in applications where improved thermal resistance is required. Furthermore, reinforced and crosslinked polyethylene presents high strength at elevated temperatures, so that the field of applications of such materials is considerably enlarged. Aramid fibers seem to be a promising reinforcement for the above materials since they combine high modulus with thermal resistance and light weight. The development of an adequate adhesive bond between aramid fiber and polyethylene matrix is of course the main problem, taking into consideration that both polyethylene and aramid present reduced chemical affinity to other substances. Thus, fiber pretreatment was performed in order to insert unsaturated groups in the aramid chain. These groups could be, in turn, grafted in the polyethylene backbone during the crosslinking reaction. The aramid fibers were treated with methacryloyl chloride, and then dispersed under stirring in 2% aqueous sodium hydroxide containing 0.5% of a nonionic surfactant. After washing and drying, the fibers were dry blended with polyethylene powder containing 2 phr dicumyl peroxide. The mixture was melt‐blended in a Brabender plasticorder and tensile specimens were prepared. Tensile measurements and microscopy on the fracture surface were carried out in order to evaluate changes introduced in the fiber by surface treatment.
Kinetics of reaction of C21 cycloaliphatic dicarboxylic acid and ethylenediamine
Authors: Kale Vijay , Vijayalakshmi P. , Rao T. Chandrasekhara , Subbarao R. , Lakshminarayana G. , Rao M. Bhagwant 
Published: April 2003

AbstractKinetic studies were carried out on the reaction between ethylenediamine and C21 cycloaliphatic dicarboxylic acid, prepared from dehydrated castor oil fatty acids and acrylic acid, in melt phase. The reaction was performed at six different temperatures ranging from 210 to 260°C and followed by determining the acid value of the product. The polyamidation reaction was found to follow an overall third order kinetics with an activation energy of 15.5 kcal/g mol.
Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters
Authors: Datye Keshav V. , Palan Bharat H. 
Published: April 2003

AbstractThe alkali hydrolysis of poly(ethylene terephthalate), anionic copolymer of poly(ethylene terephthalate), and block copolymer of poly(ethylene terephthalate)–poly(ethylene glycol) is investigated under a variety of conditions of alkali concentration in aqueous bath, additives, time, and temperature. Measurements of loss in weight, linear density, breaking load, tenacity, elongation to break apart from intrinsic viscosity, fiber density, COOH‐end group content, diameter of filaments, and scanning electron micrographs have been analyzed to identify the differences in the action of alkali on these polymer materials.
Orientation in composite of polypropylene and talc
Authors: Rybnikář F. 
Published: April 2003

AbstractX‐ray diffraction and microscopical investigation of test samples prepared by injection molding from composites of isotactic polypropylene with talc revealed a preferred orientation of the talc and polypropylene matrix. Contrary to the situation in polypropylene alone, the preferred orientation in polypropylene–talc composites survived melting and a new crystallization. Crystallization rate measurements confirmed the nucleation activity of talc for polypropylene crystallization.
Solvent‐ and glow‐discharge‐induced surface wetting and morphological changes of poly(ethylene terephthalate) (PET)
Authors: Hsieh You‐Lo , Timm Debra A. , Wu Meiping 
Published: April 2003

AbstractThe effects of argon glow discharge and selected organic solvents on the surface wettability of poly(ethylene terephthalate) (PET) and on the wettability decay of glow discharged PET films were studied. Glow discharge in argon (30 W/1 min) drastically reduced the initial water contact angle (CA) measurement of PET from 67.0 to 26.2°. The glow‐discharge‐induced wetting, however, decayed during the first 7 days and stabilized at 33.1°. Treatments in dimethyl sulfoxide, dimethyl formamide, pyrdine, and water at 80°C caused some improvement in surface wettability as shown by decreases of water CAs in the range of 53–56°. When the solvent and glow discharge treatments were applied consecutively on PET, additive effects on improving surface wettability were observed. The stabilized water CAs of the solvent‐and‐glow‐discharged films ranged from 25.0 to 32.1° depending upon the solvent type. The solvent treatments prior to glow discharge either reduced the extent of CA decay or the time taken to reach stabilization on PET films. Scanning electron microscopic evaluation showed no difference between the solventtreated and the untreated PET surfaces, but a finely etched surface was observed on the glow discharged PET at a 40,000 magnification and above. The distinctly different surface of the DMSO‐and‐glow‐discharged PET indicated that morphological changes on PET surface were induced by the solvent.
A comparison of chemorheological models for thermoset cure
Authors: Mijović Jovan , Lee Chee Hung 
Published: April 2003

AbstractA chemorheological study of a thermoset system consisting of diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin and a mixture of two armoatic amine curing agents; 4,4′ methylenedianiline (MDA) and m‐phenylene diamine (m‐PDA), was conducted. Experimentally obtained viscosity data were checked against the predictions of two different viscosity models; one based on a phenomenological equation obtained by modification of the classical Williams–Landel–Ferry (WLF) equation and the other based on an extension of the branching theory originally proposed by Flory. In general, the predictions of both models were in excellent agreement with experimentally obtained isothermal and dynamic viscosity data. The branching theory model was found to have a slight advantage over the phenomenological equation model in describing the viscosity prior to gelation in a fast heating cure cycle.
Cure behavior of very thin epoxy resin films on steel
Authors: Nigro John , Ishida Hatsuo 
Published: April 2003

AbstractFT‐IR reflection absorption spectroscopy has been used to investigate the effect of a steel surface on epoxide cure. BF3 · MEA catalyzed epoxy resin films ranging in thickness from 10 to 1000 nm are cast on low carbon automotive steel and subjected to a 100°C heat treatment. The resulting epoxide conversion and aliphatic ether formation are found to be sensitive functions of film thickness, with the thinnest films exhibiting the most conversion and ether formation. Uncatalyzed epoxy resin films (5–80 nm) were subjected to an identical analysis. Prior to receiving heat treatment, some of these very thin films (up to 10 nm) exhibit a strong aliphatic ether absorption. Upon exposing these samples to the heating regimen, a strong relationship between epoxide conversion and thickness is again apparent, with thinnest films experiencing the most conversion and ether formation.
A mechanism for flame retardation of poly(ethylene terephthalate)
Authors: Chang Po‐Hui , Wilkie Charles A. 
Published: April 2003

AbstractThe thermolysis of vinyl methylterephthalate has been studied as a model of poly(ethylene terephthalate) (PET) thermolysis. Based upon this reaction, a potential mechanism for PET flame retardation is proposed. The assumption is made, based upon firm experimental evidence, that the initial step in PET degradation is formation of a vinyl ester and a carboxylic acid. The essentials of the mechanism are that this vinyl ester participates in a vinyl polymerization reaction and produces a linear polymer. This linear polymer then is involved in a chain‐stripping reaction with the loss of methylterephthalate and the concomitant formation of a polyene. In the last step, this polyene undergoes a cyclization reaction and yields a crosslinked product. There are two stages at which PET undergoes crosslinking: In the second step the linear vinyl polymer is produced; in the last step ultimate crosslinking with the formation of cyclic structure is observed.
Weathering of polyethylene (LDPE) and enhanced photodegradable polyethylene in the marine environment
Authors: Andrady Anthony L. 
Published: April 2003

AbstractThe outdoor weathering of polyethylene homopolymer under exposure in air and in sea water was studied. Rate of deterioration as indicated by the loss in mean ultimate extension was found to be slower when the material was weathered in sea water compared to that in air. The difference in rates is explained in terms of the lack of heat buildup in plastic material floating in sea water. A similar study on a commercially available ethylene–carbon monooxide copolymer indicated rapid photodegradation under both exposure conditions.
Sodium cellulose formation by activation process
Authors: Laszkiewicz B. , Wcislo P. 
Published: April 2003

AbstractThe formation of sodium cellulose is the first reaction step in some large scale derivatization process of cellulose, e.g., xantation or carboxymethylation, as well as in the mercerization of cotton. It was found that the sodium cellulose formation depends on some activators present in the steeping lye, as well as on the press ratio, steeping temperature, and steeping ley concentration. IR data and X‐ray scattering showed that the initial native cellulose was converted into an unoriented cellulose II in the lower concentration of steeping ley with presence of urea, thiourea, and sodium aluminate or zincate as activators. The sodium cellulose formed with activators was more reactive to xanthation than the cellulose from unactivated process.
Dynamics and structure development during high speed melt spinning of nylon 6. I. On‐line experimental measurements
Authors: Bheda Jayendra H. , Spruiell Joseph E. 
Published: April 2003

AbstractOn‐line experimental measurements of filament diameter, temperature, and birefringence as a function of distance from the spinneret were carried out during melt spinning of two nylon 6 resins of differing molecular weight. Filament tension was also measured. A rapid diameter attenuation or “necking” was observed in the spinline for both resins at take‐up velocities above 6000 m/min. Evidence of crystallization in the spinline was also observed at these high spinning speeds. An analytical technique was used to extract apparent elongational viscosity for each resin and heat transfer coefficient for the melt spinning process from the experimental results.
Bulk polymerization of polyurethane under high pressure
Authors: Park Kang Choo , Kim Sung Chul 
Published: April 2003

AbstractThe pressure effect on the reaction kinetics, molecular weight, and the microphase separation of the soft and hard segment of the polyurethane, synthesized under high pressure, was studied. The polymerization rate increased with increasing synthesis pressure and the activation energy of polymerization decreased with increasing synthesis pressure from 22.4 kcal/mol at 1 kg/cm2 to 19.4 kcal/mol at 3000 kg/cm2. The volume of activation of the polyurethane polymerization was −19.8 cm3/mol at 60°C. Microphase separation between soft and hard segment decreased with increasing synthesis pressure and increased with increasing synthesis temperature. Molecular weight and molecular weight distribution were not influenced by the synthesis pressure.
In situ reactive compatibilization in polymer blends: Effects of functional group concentrations
Authors: Saleem M. , Baker W. E. 
Published: April 2003

AbstractPolystyrene (PS) and polyethylene (PE), along with their reactive counterparts, i.e., polystyrene having oxazoline reactive groups (OPS) and polyethylene with carboxylic acid groups (CPE), were melt blended in a Rheomix mixer. These blends were prepared by mixing these polymers in various proportions under a variety of conditions. In an alternate procedure the OPS, CPE graft polymer (OPS‐g‐CPE) was prepared by melt blending these two polymers beforehand, and subsequently this grafted polymer was used as a compatibilizer for PS–PE blends. The effects of the addition of OPS and CPE, on the one hand, and OPS‐g‐CPE, on the other hand, on the compatibility of PS–PE blends were investigated. The morphology of these blends was examined with a scanning electron microscope (SEM) and related to their tensile properties. The PS–PE blends are found to have the typical coarse morphology of incompatible blends and poor tensile properties while their reactive counterparts, OPS‐CPE blends, have fine grain microstructure and show improved tensile strength throughout the range and improved elongation in the PE‐rich blends. Relatively low concentrations of the reactive pair, oxazoline and carboxylic acid, are shown to be necessary to produce improved compatibility. The preblended graft copolymer OPS‐g‐CPE imparts compatibility to PS–PE blends also but not as effectively. This suggests that the addition of OPS and CPE during melt mixing of PS and PE forms OPS‐g‐CPE polymer at the interface and that these ingredients act as “in situ reactive compatibilizers” which improve physical properties.
Analysis of the cure kinetics of epoxy/imidazole resin systems
Authors: Heise M. S. , Martin G. C. 
Published: April 2003

AbstractThe reaction kinetics for the cure of epoxy resins with imidazoles were determined from Fourier transform infrared spectroscopy and differential scanning calorimetry studies. The diglycidyl ether of bisphenol A and phenyl glycidyl ether were cured with various concentrations of 2‐ethyl‐4‐methyl‐imidazole ranging from 4.0 to 100.0 mol %. The first step in the curing process is the formation of epoxide/imidazole adducts. These adducts initiate the etherification reaction which crosslinks the resin. The kinetics were determined and confirmed for both the adduct and the etherification reactions as a function of the imidazole concentration. A model was developed and used to predict the concentrations of the unreacted epoxide groups and the reaction products for a wide range of imidazole concentrations and cure temperatures.
Dynamic viscoelasticity of isoprene rubber reinforced with short cellulose fibers
Authors: Yano Shoichiro , Hirose Shigeo , Hatakeyama Hyoe , Westerlind Bo , Rigdahl Mikael 
Published: April 2003

AbstractThe dynamic viscoelasticity was investigated for isoprene rubber (IR) composites filled with untreated and chemically treated cellulose fibers. Mercerization and benzylation were employed as chemical treatments. Bleached kraft pulp and cellulose powder were used as cellulose fillers. By mixing cellulose fillers, the dynamic modulus E′ of IR composites was improved, especially above the glass transition temperature. Benzylation of cellulose fibers reduced E′ of IR composite, while mercerization increased it. A tan δ peak was observed at about −33°C at 110 Hz along with a shoulder peak at about −16°C for the IR composites. The intensity of the tan δ peak decreased when mixed with cellulose fillers. The shoulder peak next to the main peak could be separated assuming a Gaussian type equation; log E″ = D exp { −C[(1sol;T) − (1/T0)]2} where D is the maximum value of log E″ vs. 1/T curve, T0 is the maximum temperature, and C is a parameter to determine the width of the Gaussian function. From the Arrhenius plot of the frequencies against 1/T0, the apparent activation energies were calculated as 220–235 kJ/mol for the shoulder peak (α1 process) and ca. 180 kJ/mol for the main peak (α2 process). The α2 process is caused by the glass transition of the rubber matrix. The α1 process is assigned as the molecular motion of the rubber matrix strongly restricted by the fiber element.
Preparation of high modulus poly(vinyl alcohol) by drawing
Authors: Yamaura Kazuo , Tanigami Tetsuya , Hayashi Naoki , Kosuda Ken‐Ichi , Okuda Shigeyasu , Takemura Yumiko , Itok Masayasu , Matsuzawa Shuji 
Published: April 2003

AbstractThe preparation of PVA films and fibers with high modulus and high strength was examined. The high drawing was attained when both the drawing just before melting and the relaxation at room temperature were repeated. The maximum draw ratio was 40 for the films prepared from the gels of high molecular weight (HMW) a‐PVA (DP ‐ 12000)/water/dimethyl sulfoxide (DMSO) system (water/DMSO = 20/80). The degree of crystallinity of tthe dried gels prepared from the PVA/ethylene glycol (EG) system was high, 40–50%, and independent on the tacticity of PVA. The modulus of the fibers, prepared from the gels of HMW s‐PVA (DP = 15300)/EG system, drawn 15 times to its original length was the highest (120 GPa).
The dependence of properties of cellulose acetate propionate on molecular weight and the level of plasticizer
Authors: Sand I. Daniel 
Published: April 2003

AbstractThermal and mechanical properties were measured for solvent‐cast films of cellulose acetate propionate plasticized with triphenyl phosphate. Probabilistic models for the glass transition temperature, tensile heat deflection temperature, tensile modulus, break stress, and initial tear strength as functions of weight‐average molecular weight and level of plasticizer were developed. The glass transition temperature and the tensile heat deflection temperature were modeled well by functions of the level of plasticizer as the only variable, whereas models for the tensile modulus, break stress, and inital tear strength included molecular weight. Only the break stress showed a statistically significant term of interaction between molecular weight and level of plasticizer. This term was such that, for unplasticized films, increasing the molecular weight increased the break stress, whereas, for films formulated with 20 pph plasticizer, increasing the molecular weight decreased the break stress. Physical explanations for this interaction term are discussed.
Antisoiling of polyester (PET) by a novel method of plasma treatments and its evaluation by color measurement
Authors: Jahagirdar C. J. , Venkatakrishnan S. 
Published: April 2003

AbstractDirect current and radiofrequency plasma treatment of different durations were given to polyester fabric to impart soil resistance. The soil repellency increased with increasing time of treatment. The possible mechanism of soil repellency is outlined. The evaluation of soiling has been made from CIE brightness variable Y with source D65 using Minolta Chromameter Reflectance II. This was well in agreement with the conventional reflectance measurement method using spectrophotometer. The plasma treatment system has the advantage of energy and floor space savings and pollution‐free atmosphere
Analysis of the formation and curing reactions of resole phenolics
Authors: So Solomon , Rudin Alfred 
Published: April 2003

AbstractThe chemical composition and molecular size distributions of a series of soluble resole phenolics was studied by high resolution 13C NMR, IR, GPC, and viscosity techniques. The curing reactions were then followed by IR and solid state 13C NMR techniques. The ultimate degree of cure increases with curing time and temperature. The molecular weight of the precursor resole can be increased with increasing formaldehyde/phenol mole ratio and increased condensation reaction time and temperature. The degree of cure achieved under given conditions is directly proportional to the molecular weight of the precursor resole. The condensation catalyst has a great effect on resole composition and molecular size. It also influences preferential methylolation at the para position to the phenolic OH group in the following increasing order Ba(OH)2, NaOH, Na2CO3. The curing pH affects the degree of cure as well as the type of linkages formed. Methylene bridges are almost exclusive at high or very low pH's, while dibenzyl ether bridges predominate at neutral pH. High resolution 13C NMR spectroscopy is the most powerful tool to study soluble resoles. Infrared spectroscopy supplies qualitative results. Solid state 13C NMR is useful to study polymers during the curing process but there are inherent limitations and potential errors in this method.
Heat resistant styrene/α‐methylstyrene copolymers made via continuous anionic polymerization at high temperature
Authors: Priddy Duane B. , Traugott T. D. , Seiss R. H. 
Published: April 2003

AbstractStyrene/α‐methylstyrene (SAMS) copolymers were produced containing up to 67 weight % AMS. The polymerizations were carried out using anionic polymerization at high temperature (100°C) in a CSTR type reactor. The reactivity ratios for the anionic copolymerization of styrene (M1) and AMS (M2) were estimated to be r1 = 60 and r2 = 0.01. Thermal degradation of a SAMS copolymer containing 50 weight % AMS was studied and compared with free radical polystyrene (FRPS) and anionic polystyrene (APS). The relative rate of styrene monomer generation for the three polymers followed the order SAMS > FRPS > APS. The relative rate of loss of molecular weight for the three polymers was FRPS > APS > SAMS. This indicates that the main mechanism of thermal degradation of SAMS copolymers is depolymerization rather than chain scission.
Formation and characterization of cellulose films from a liquid crystalline solution of cellulose in ammonia/ammonium thiocyanate
Authors: Chen Yue‐Shen , Yang Kap Seung , Cuculo John A. 
Published: April 2003

AbstractFilms were cast from liquid crystalline solutions of cellulose in an ammonia (NH3)/ammonium thiocyanate (NH4SCN) solvent. Microscopic examination of the cellulose liquid crystalline solutions used for the film formation exhibited the so‐called conjugated phase. It displayed a fingerprint and a uniformly dispersed highly birefringent pattern. Without additives, the films made from these liquid crystalline solutions are clear, flexible, and have high strength comparable to commercial Cellophone® films. The infrared crystallinity index of the film was somewhat higher than that of other cellulose II materials.