bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal behavior of cast polyurethane elastomers
Authors: Pandya M. V. , Deshpande D. D. , Hundiwale D. G. 
Published: April 2003

AbstractThermal properties like glass transition temperature (Tg), initial decomposition temperature (idt), integral procedural decomposition temperature (ipdt), and temperature at various % weight loss of a number of polyurethane systems are reported in this paper. Glass transition temperature was determined on TMA, and other thermal properties were determined by thermogravimetry. The experiments were designed to understand various factors such as length of chain extender moiety, flexibility of chain extender units by substitution of ether link in the diol chain, nature of bonds (unsaturation) in the extender unit, and nature of diisocyanates.
Grafting of vinyl acetate onto poly(vinyl chloride) in solution
Authors: Vigo Fernando , Uliana Claudio 
Published: April 2003

AbstractRadiation‐induced grafting of vinyl acetate (VAc) onto poly(vinyl chloride) (PVC) was performed in solution with dimethylformamide (DMF). Grafting was studied as a function of dose, dose rate, and VAc/PVC ratio. The amount of grafting was measured by IR spectroscopy on the graft copolymer fraction insoluble in hot methanol. The homopolymerization of VAc was also studied in the same conditions, in order to check the influence of the solvent on radiochemical reactions leading to graft copolymers. The results show that the grafting can be easily obtained and the graft copolymer will be tested for the preparation of ultrafiltration membranes.
Effect of impurities on emulsion polymerization: Case I kinetics
Authors: Penlidis A. , MacGregor J. F. , Hamielec A. E. 
Published: April 2003

AbstractThe effect of water‐ and monomer‐soluble impurities on the kinetics of emulsion polymerization for Case I systems (e.g., vinyl acetate and vinyl choride) was investigated. Model predictions on the effect of these impurities on polymer particle nucleation and growth rate are shown to be in satisfactory agreement with experimental results. The effect of monomer‐soluble impurities is shown to be quite different from that observed in Case II emulsion polymerization systems.
Bonding of untreated cellulose fibers to natural rubber
Authors: Flink Per , Westerlind Bo , Rigdahl Mikael , Stenberg Bengt 
Published: April 2003

AbstractSulfur‐ and peroxide‐cured natural rubbers (NR) reinforced with short fibers of cellulose and carbon black have been studied with respect to water absorption, crosslink density, tensile strength, and the dependence of the dynamic storage modulus on strain amplitude. The results indicate that there is bonding between fiber and matrix even in the absence of a specific bonding system.
Studies of temperature and atmosphere composition influence on thermal degradation products of polyurethane foam
Authors: Włodarczak Daniela 
Published: April 2003

AbstractThe paper presents studies on the influence of temperature and atmosphere composition on the thermal degradation products evolved from flexible polyurethane foam. The experiments have been carried on within the temperature range 200–700°C in air atmosphere and oxygen–nitrogen–helium mixtures. The main volatile toxic products and weight losses during thermal degradation of the polyurethane foam have been determined. The test results have been presented graphically.
Surface energy of untreated and surface‐modified cellulose fibers
Authors: Westerlind Bo S. , Berg John C. 
Published: April 2003

AbstractAverage advancing and receding contact angles made against cotton and glass fibers by a set of probe liquids are determined using the Wilhelmy technique. The dispersive and polar components of the surface energy are calculated from the measured contact angles using both the geometric and the harmonic mean methods. It is found that these components are similar for untreated cellulose and glass fibers, and that they both have a high polar component, corresponding to a hydrophilic surface. Changes in surface energy caused by treatment of the cellulose fiber surfaces with melamine, polyethyleneimine (PEI), and a silane coupling agent are reported. It is found in particular that polyethyleneimine treatment of cellulose significantly reduces the polar component of its surface energy. While treatment of glass fibers with a silane coupling agent reduces the polar component and increases the dispersive component of the surface energy it shows little effect on the surface energy of cellulose.
Effect of inorganic salt on adsorption of sodium alkyl sulfates and fatty acid sodium salts from aqueous solution onto ion exchange resins
Authors: Ihara Yasuji 
Published: April 2003

AbstractThe adsorption isotherms of sodium salts of alkyl sulfonic acid and fatty acid with various carbon numbers onto ion exchange resins were measured in the absence and in the presence of sodium chloride in aqueous solutions. In the absence of the inorganic salt, the amount of adsorption remarkably increased with an increase in the length of alkyl groups in the adsorbates. Furthermore, the amount of adsorption apparently decreased with addition of sodium chloride into the solutions and almost reached a constant value at high concentrations of NaCl. This behavior strongly suggested that the electrostatic interaction on the adsorption decreased with increasing salt concentration and that the effect of hydrophobic interaction seems to play an important role on adsorption.
Kinetics of reaction of ethylenediamine and dimeric fatty acids
Authors: Kale Vijay , Vedanayagam H. Sumathi , Devi K. Sita , Rao S. Venkob , Lakshminarayana G. , Rao M. Bhagwant 
Published: April 2003

AbstractKinetic studies were carried out on the reaction between ethylenediamine and dimeric fatty acids in melt phase. The reaction was performed at 124, 130, 145, 160, 174, and 190°C and followed by determining the acid value of the product. The polyamidation reaction was found to be of overall second order with an activation energy of 18.2 kcal/g mol up to 90% conversion and of overall third order with an activation energy of 16.4 kcal/g mol above 90% conversion.
Studies on irradiation of agar–agar in the solid state: On the changes of water holding capacity of agar–agar hydrogel produced by irradiation
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractSolid agar–agar was irradiated with 60Co gamma‐rays, and effects of radiation on the water‐holding capacity of agar–agar molecules were studied by measuring the water content of the agar–agar hydrogel. The effects of postirradiation were also studied. Empirical equations of changes of water holding capacity were obtained.
A model for service life of polyethylene pipe exhibiting ductile–brittle transition in failure mode
Authors: Derringer George C. 
Published: April 2003

AbstractThis article proposes a model for predicting failure time of stressed polyethylene pipe materials that exhibit a failure mode transition from brittle to ductile as stress is increased. The model is based on data obtained using the constant tensile load (CTL) test and takes into account stress‐versus‐failure‐time behavior in both brittle and ductile regimes, as well as in the transition regime. The model permits quantification of the ductile–brittle transition behavior not only from the standpoint of the location of the transition but also its breadth. It is illustrated that knowledge of these two separate parameters opens new avenues for understanding the molecular basis of the transition process. This research was conducted under the sponsorship of the Gas Research Institute.
Mixing characteristics of urethane based materials and polyurea in RIM
Authors: Nelson M. , Lee L. James 
Published: April 2003

AbstractTo facilitate the study of new reaction injection molding (RIM) materials on a practical scale, a lab‐scale mini‐RIM machine was constructed. This machine is capable of delivering up to approximately 250 cc of material at rates of up to 125 cc/s. The RIM machine was first tested with conventional materials such as crosslinked and linear polyurethanes. The effect of varying the nozzle Reynolds number upon the adiabatic temperature rise corresponded to the results reported in previous works. Following this verification, two developmental materials, a polyurethane/polyester interpenetrating polymer network and a polyurea, were examined. The polyurea material showed a very strong dependency on mixing up to a Reynolds number above 400. The 75/25 PU/PEster reaction exotherms also showed a dependency upon mixing. However, this dependency is noticeable only in the polyester portion of the reaction, which can be attributed to the mixing sensitivity of the redox‐type initiators used.
Application and development of synthetic polymer membranes. II. Separation of aqueous ethanol solution through poly(tert‐butyl methacrylate‐co‐styrene) membranes
Authors: Yoshikawa Masakazu , Ohsawa Tomoki , Tanigaki Masataka , Eguchi Wataru 
Published: April 2003

AbstractSeparation of aqueous ethanol solution was carried out by pervaporation using a membrane which consisted of common polymer membranes. A membrane obtained from poly(tert‐butyl methacrylate‐co‐styrene) was effective for a selective separation of ethanol from aqueous ethanol solution by pervaporation technique. The pervaporation ethanol–water mixture through the present membranes was analyzed as a solution–diffusion process, on the assumption that the both diffusion coefficients of each component are an exponential function of ethanol concentration.
Bulk functionalization of ethylene–propylene copolymers. III. Structural and superreticular order investigations
Authors: Greco Roberto , Musto Pellegrino , Riva Fernando , Maglio Giovanni 
Published: April 2003

AbstractAn ethylene‐propylene copolymer (EPR) has been functionalized with dibutyl maleate (DBM) by means of a radical‐initiated bulk process. Different degrees of grafting have been obtained by varying the overall composition of the reaction mixture as well as the processing procedures. The influence of the grafting degree on the structural and superreticular (or “long range”) order has been investigated by differential scanning calorimetry (DSC), Fourier transform infrared analysis (FTIR), and wide (WAXS) and small angle X‐ray scattering (SAXS) techniques. The functionalization leads to a decrease of the “residual crystallinity” present in the parent copolymer. Linear relationships between the grafting degree and the crystallinity degree Xc evaluated by both DSC and WAXS have been obtained. The results of the structural investigations, in agreement with previously reported ones, suggest that the grafting preferentially occurs onto the longer or more perfect methylene sequences. SAXS investigations showed that the significant degree of structuration, i.e., crystalline and paracrystalline order, present in the parent elastomer, gradually disappears by increasing the degree of grafting.
Graft copolymerization of acrylonitrile onto acetylated jute fibers
Authors: Mohanty Amar K. , Patnaik S. , Singh B. C. , Misra M. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile (AN) onto acetylated chemically modified jute was carried out in the temperature range 40–60°C using V5+‐cyclohexanone redox initiator system. The effects of temperature, time, concentrations of metal ion (V5+), monomer (AN), cyclohexanone, some inorganic salts, and organic solvents on percent grafting have been studied. IR spectra of acetylated chemically modified jute and grafted jute have been taken, and their characteristic bands have been identified. Grafting has improved the thermal stability and also the lightfastness rating of jute fibers dyed with basic dyes.
Studies in the graft copolymerization of vinyl monomers on cellulosic materials
Authors: Okieimen F. E. , Idehen K. I. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile, methyl methacrylate, and vinyl acetate on bleached holocellulose initiated by ceric ions in aqueous medium was studied at 29°C. The extent of graft copolymer formation was poly(methyl methacrylate) > polyacrylonitrile > poly(vinyl acetate), indicating the influence of polarity of monomer on graft copolymerization. It was found that, although the molecular weights of the grafted polyacrylonitrile copolymer were lower than the values obtained for poly(methyl methacrylate), the latter was less frequently incorporated on the cellulosic backbone polymer than the polyacrylonitrile grafts. The marked reductions in graft level associated with thiolation of the cellulosic material suggest that hydrogen abstraction reactions from carbon atom carrying hydroxyl groups may not be important in graft copolymer formation.
Adhesion between aluminum and copolymers of ethylene and vinyltrimethoxysilane
Authors: Ulrén L. , Hjertberg T. 
Published: April 2003

AbstractThe adhension between aluminum and poly(ethylene‐co‐vinyltrimethoxysilane) (EVS) and poly(ethylene‐co‐butylacrylate‐co‐vinyltrimethoxysilane) (EVSBA), respectively, have been studied. For comparison an ordinary low density polyethylene (LDPE), a poly(ethylene‐co‐butylacrylate) (EBA), and an ionomer regarded as a bonding polymer were studied as well. The peel strength of laminates obtained by pressing were measured by a T‐peel test. The structure of the fracture surfaces were investigated by reflection‐IR, ESCA, and SEM. The peel strength of the LDPE and the EBA samples were 100 and 700 N/m, respectively. Although the amount of vinylsilane was low, about 0.2–0.3 mol %, its presence had a pronounced influence on the adhesion: 1800 and 3000 N/m for EVS and EVSBA, respectively. This is even higher than the value observed for the ionomer, 1560 N/m. Although there was a marked difference in surface topology, the SEM and ESCA analysis showed that the fracture was cohesive for both EVS and EVSBA. Immersion in water at 85°C increased the peel strength even more, especially in the case of EVSBA (up to 9000 N/m), in contrast to what is normally observed with aluminum polyethylene laminates. The results suggest that strong and nonhydrolyzable bonds, e.g., covalent bonds, have been formed across the polymer‐metal interface for the ethylene copolymers containing vinylsilane.
Effect of extension rate on the stress–strain characteristics of grafted casein film
Authors: Somanathan N. , Arumugam V. , Naresh M. D. , Sanjeevi R. 
Published: April 2003

AbstractCasein was grafted with a binary mixture of acrylonitrile and n‐butyl methacrylate. The mechanical properties of the grafted casein films were studied at various extension rates. The fractured surfaces were analyzed using scanning electron microscopy. With the increase in extension rate, the strain at yield increases to a maximum value and then decreases to a limiting value. The stress at yield and the energy at break steadily increase with the increase in the rate of extension.
Polyisobutylene‐based urethane foams. II. Synthesis and properties of novel polyisobutylene‐based flexible polyurethane foams
Authors: Ako Masayuki , Kennedy Joseph P. 
Published: April 2003

AbstractNovel polyisobutylene‐based flexible polyurethane foams (PIB–PUF) have been prepared manually by the prepolymer method using three‐arm star hydroxyl‐terminated polyisobutylenes (PIB–triols) and toluene diisocyanate (TDI). Solvent extraction and IR spectroscopy of PIB–PUFs indicated essentially complete crosslinking. Conventional polyether‐based polyrethane foams (PE–PUFs) and polybutadiene‐based polyurethane foams (PBD–PUFs) have also been prepared by the same method and select physical‐mechanical properties of all these urethane foams, such as tensile strength, elongation, resilience, water permeability, hot air stability, and hydrolytic stability, have been examined and compared. Although the density of PIB–PUF is lower than that of PE–PUF, its tensile strength is superior to the latter. Elongation of PIB–PUF is almost the same as those of the other foams. The PIB–PUF exhibits low resilience which indicates good damping properties. Due to the hydrophobicity of the soft segment, PIB–PUF exhibits very low water permeability. The hydrolytic and hot air stability of PIB–PUFs are outstanding. Attempts have been made to determine gas permeabilities; however, due to the open‐cell nature of the foams, these studies could not be completed. The new PIB‐based urethane foams combine excellent thermal, environmental, barrier, and mechanical properties, unmatched by conventional PUFs.
The heterogeneous character of the dilute acid hydrolysis of crystalline cellulose
Authors: Wood Barry F. , Conner Anthony H. , Hill Charles G. 
Published: April 2003

AbstractThe end‐attack model proposed by Sharples [Trans. Faraday Soc., 53, 1003 (1957)] for the dilute acid hydrolysis of crystalline cellulose was tested using the results from the size‐exclusion chromatographic analysis of samples of crystalline cellulose I and cellulose II hydrolyzed in 6.1N HCl at 107°C. The differential number distribution of the molecular weight of hydrolyzed cellulose was found to be approximately exponential, a result which is consistent with the end‐attack model. Differences in the rates of hydrolysis of cellulosic materials appear to arise from differences in both the degree of polymerization and the microstructure of hydrolyzed cellulose. Evidence is also presented which suggests that the recrystallization upon hydrolysis results in part from the lateral accretion of chains which are cleaved during the hydrolysis of amorphous regions in the cellulose microfibrils.
Matrix relaxations in rubber‐toughened thermoplastics
Authors: Starkweather Howard W. 
Published: April 2003

AbstractIn several systems involving a rubber dispersed in a higher modulus polymer, we have found that both the storage modulus are temperatures below the major softening process and the maximum value of the loss modulus are proportional to the square of the volume fraction of the matrix. This agrees with a relationship for foams derived theoretically by Termonia using a finite‐difference approach. Similar relationships have been found for the glass transition in polymethyl methacrylate and for crystalline relaxations in polyethylene, polyoxymethylene, and polytetrafluoroethylene which involve large decreases in modulus.
Effect of diluents and/or fortifier on the glass fiber–epoxy composites
Authors: Thakkar Jatin , Patel Ravji , Patel Ranjan , Patel Vithal 
Published: April 2003

AbstractThe glass fiber‐epoxy composites were fabricated with the E‐type glass cloth and diglycidyl ether of bisphenol A (DGEBA) using 12% diethylenetriamine (DETA) as catalyst on the basis of DGEBA. The properties were modified by incorporating diluents such as epoxidized 2,2,6,6‐tetramethylolcyclohexanol (ETMC) and 1,4‐butandioldiglycidyl ether (BDDE) with/without 20 parts per 100 g of a condensation product of phenyglycidylether and 4‐hydroxyacetanilide (PGEHA) employed as fortifier. The characterization of these epoxy laminates includes resistance to chemical reagents, dynamic mechanical analysis, and mechanical properties like flexural strength, impact strength, and hardness. The dielectrical properties such as breakdown strength, dielectric constant (ε′), dielectric loss (ε″), and loss tangent (tan δ) were estimated.
Thermotropic mesomorphic polyesters. I. Copolyesters of terephthalic acid, hydroquinone, and flexible diols
Authors: Ghadage Ramesh S. , Ponrathnam Surendra , Nadkarni Vikas M. 
Published: April 2003

AbstractA new series of copolyesters has been synthesized by low‐temperature solution polycondensation of terephthaloyl dichloride hydroquinone and flexible diols such as 1,2‐propane diol, 1,4‐butanediol, diethylene glycol, (cis) 1,4‐cyclohexanediol and (cis + trans) 1,4‐bis(hydroxymethyl) cyclohexane. The copolyesters are all insoluble and display thermotropic mesophases at relatively lower transitions than other commercially important systems. The transition temperatures, the crystallinity, and thermal characterization are reported.
Propylene polymerization in a semibatch slurry reactor over supported TiCl4/MgCl2/ethyl benzoate/triethyl aluminum catalyst. I. Catalytic behavior
Authors: Dumas Constantine , Hsu Cheng C. 
Published: April 2003

AbstractHigh activity TiCl4/MgCl2/ethyl benzoate (EB)/triethyl aluminum (TEA) catalysts for the polymerization of propylene were synthesized and characterized for particle size distribution and crystallinity. Polymerization was carried out in a semibatch, constant pressure slurry reactor. A correction for interfacial mass transfer was found to be necessary to relate the monomer feed rate to the instantaneous rate of polymerization. Without such a correction serious misinterpretation of rate data could result. Optimum productivity was observed with respect to the Al/Ti ratio. Similar behavior was observed with polymerization temperature. Isotacticity increased with polymerization tamperature and decreased with Al/Ti ratio. The addition of a small amount of 2,2,6,6‐tetramethylpiperidine increased the percentage of isotactic polypropylene to 98% without significantly affecting productivity.
Electron beam effects on polymers. III. Mechanical and thermal properties of electron beam‐irradiated poly(phenylene sulfide)
Authors: El‐Naggar A. M. , Kim H. C. , López L. C. , Wilkes G. L. 
Published: April 2003

AbstractThe effect of electron beam (EB) irradiation on the mechanical and thermal properties of initially amorphous and semicrystalline poly(phenylene sulfide) (PPS) films has been investigated. Irradiations were carried out either in a nitrogen or air atmosphere. Subsequent mechanical testing carried out at 23°C suggested that oxidative degradation occurs in air for high radiation dosages. However, modulus and tensile strength were not greatly affected by irradiation level. Moreover, it was found that elongation by yielding no longer occurs at doses higher than 1000 Mrad for initially amorphous materials and above 500 Mrad for the initially semicrystalline materials. Differential scanning calorimetry (DSC) measurements utilized to determine crystallinity and melting behavior suggest the likely occurrence of some crosslinking with high irradiation levels. Scanning electron microscopy (SEM) of the irradiated PPS surface suggest the possible occurrence of gas evolution—at least for high dosage levels.
Thermal stability and degradation studies of polyester resins
Authors: Bansal Raj K. , Mittal Jagjiwan , Singh Prakash 
Published: April 2003

AbstractThermal behavior and degradation mechanisms of three polyester resins, namely bisphenol A based, isophthalic acid based, and general purpose were studied. These resins were cured with styrene in the presence of benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP) as initiators. The cured resins were studied by thermogravimetric analysis and mass spectrometry. From the thermogravimetric data it was observed that the cured bisphenol‐A‐based polyester resin was thermally more stable than the cured isophthalic acid‐based and general purpose polyester resins. It was also observed that polyester resins cured with MEKP are thermally more stable than benzoyl peroxide‐cured products. Thermogravimetric analysis data shows that there are two first‐order degradation reactions during thermal degradation in nitrogen atmosphere. The first degradation step involves the scission of cross‐links/weak links with the liberation of free linear chains. The second step involves a random scission of the free linear chains into smaller fragments. The framentation patterns of the polyester resins were identified by mass spectrometery. Possible mechanisms for the degradation of the cured polyesters accounting for the experimental observations are discussed.