bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue‐resistant nylon alloys
Authors: Wyzgoski M. G. , Novak G. E. 
Published: April 2003

AbstractCrystalline nylon 66 was modified by blending with both an amorphous nylon and a rubbermodified amorphous nylon. The ternary blends exhibit a 50–100‐fold decrease in fatigue crack propagation rates, even at rubber concentrations of only 1 or 2%. These same blends do not necessarily exhibit improved impact strength and the examination of a variety of alloys and blends demonstrates that fatigue and impact fracture mechanisms are distinctly different. The fracture surface morphologies indicate that the basic fatigue fracture mechanism of craze coalescence for nylon 66 is not changed by alloying. However, the presence of the rubbery phase leads to cavitation and ductile drawing that retard the craze breakdown and coalescence processes without evidence of crack tip blunting. Surprisingly, the addition of rubber‐modified nylon 66 to a nylon 66 matrix does not impart as great an improvement in fatigue resistance as does the miscible amorphous nylon. Also, alloys having improved impact strength are observed to exhibit inferior fatigue resistance. These results demonstrate that the excellent fatigue resistance of crystalline polymers can be improved even further by judicious selection of alloying ingredients optimized specifically for fatigue fracture. © 1994 John Wiley & Sons, Inc.
Miscibilization of telechelic fluoroalkeneoxide oligomers in epoxy resins and effects on morphology and physical properties
Authors: Mascia L. , Zitouni F. , Tonelli C. 
Published: April 2003

AbstractHydroxyterminated fluoroalkene oxide oligomers were reacted with chlorendic anhydride and subsequently with ϵ‐caprolactone to produce carboxyterminated perfluoroethers prepolymers that were totally miscible with diglycidylether of bisphenol A. Curing the epoxy resin mixtures with hexahydrophthalic anhydride hardener and benzyl dimethylamine catalyst produced transparent products exhibiting a two‐phase co‐continuous morphology. Prereacting the fluoroalkeneoxide prepolymers with an excess of epoxy resin prior to the addition of hardener and catalyst, resulted in opaque products displaying a two‐phase dispersed particles morphology. The dynamic mechanical spectra of the cured products confirmed the absence of any significant short‐range network miscibility and revealed substantial enhancements in β‐relaxations in all cases, which are normally associated with microdispersed morphologies. Both systems exhibited much higher flexural strength and ductility than the equivalent unmodified epoxy resins even at very low levels of addition. 3.5–5.0%. The surface energy was found to be much lower than that exhibited by the unmodified resin system, and the reduction in water absorption was relatively small. The above effects were much more pronounced for products exhibiting a particulate morphology than for systems that exhibited a co‐continuous morphology. © 1994 John Wiley & Sons, Inc.
Mechanical properties of acrylate networks formed by visible laser‐induced polymerization. I. Dependence on photopolymerization parameters
Authors: Torres‐Filho A. , Neckers D. C. 
Published: April 2003

AbstractThe mechanical properties of network molecular systems, prepared through visible (Ar+) laser‐induced polymerization of multifunctional acrylates, were studied as a function of some of the photopolymerization parameters. The properties investigated were the Young's modulus of elasticity and the stress‐at‐break, both derived from the stress versus strain test of dogbone‐shaped photopolymerized samples. The parameters studied included the dye and co‐initiator concentrations, and the laser power. We also compared the mechanical properties of samples made using different types of fluorone dyes and using two different amines as co‐initiator. Better polymers are formed by the dyes with low fluorescence quantum yield. The three photopolymerization parameters modify the mechanical properties in a very similar way: they initially tend to increase both the Young's modulus and the stress‐at‐break but have a deleterious effect on the material strength if used in excess. N‐phenylglycine, NPG, was shown to form stronger polymers (higher Young's modulus) than if N,N‐dimethyl‐2,6‐diisopropylaniline, DIDMA, was used as co‐initiator. We discuss the possible molecular mechanisms for such observations. © 1994 John Wiley & Sons, Inc.
Hydrogel capsules for sustained drug release
Authors: Ramaraj B. , Radhakrishnan Ganga 
Published: April 2003

AbstractInterpenetrating polymer networks (IPNs) based on polyacrylamide and polyvinyl alcohol for hydrogel capsules were synthesized. These polymer networks were evaluated as drug‐delivery devices using Crystal Violet and Bromothymol Blue as model drugs. The observed drug release is higher for semi‐II‐IPN than full‐IPN. The drug‐release behaviors from these capsules were analyzed by the exponent relation Mt/Mα = Ktn, where “K” and “n” are constants and Mt/Mα is the fraction of the drug released until time “t.” The constant “n” was found to be above 0.5, which suggests that the release of drug from the capsules follows the non‐Fickian diffusional model. The mechanical behavior of hydrogel disks were also analyzed. © 1994 John Wiley & Sons, Inc.
Role of functionality in MDI‐based elastomer preparation
Authors: Chang Wally L. , Baranowski Tom , Karalis Tom 
Published: April 2003

AbstractIn our study of functionality, a control 4,4′‐diphenylmethane diisocyanate (MDI)‐based elastomer prepared from a linear polyester and a linear chain extender was compared to (1) those having functionality synthesized into the backbone of the polyester and (2) those having the functionality added as part of the chain extender package. A wide range of physical and mechanical properties of the finished elastomers were compared. The resultant information offers a strong basic understanding of the role of functionality in an MDI‐based polyester elastomer and also provides the complex chemical relationships involved in formulating a desired elastomer. This information will better enable the urethane researcher and manufacturer to pick and choose those attributes of elastomeric functionality that are necessary to fulfill their needs. © 1994 John Wiley & Sons, Inc.
UV curing of composites based on modified unsaturated polyester
Authors: Shi Wenfang , Rånby Bengt 
Published: April 2003

AbstractSynthesis and photocrosslinking of glass fiber‐reinforced composites, based on epoxy acrylate‐modified unsaturated polyester, have been investigated. The efficiency of the photocrosslinking process for glass fiber laminates of the polyesters that contain different comonomers has been evaluated by measuring mechanical properties. The data show (i) that 2 mm thick laminates, containing 30–40% glass fiber mats, are cured with UV irradiation for 15 sec at room temperature in air; (ii) that multifunctional acrylate or acrylether monomers added to the polyester resin improve the tensile and flexural properties of the photocured product to a greater extent than do added allylic monomers, due to the different photocrosslinking mechanisms; (iii) that the physical properties of the photocrosslinked laminates are well correlated with the molecular weight of the polyester, the amount of multifunctional monomer added, and the glass fiber content. © 1994 John Wiley & Sons, Inc.
Morphological studies on extruded films and filaments of polypropylene
Authors: Janarthanan R. , Garg S. N. , Misra A. 
Published: April 2003

AbstractIn the present work, an attempt has been made to study the development of morphology during extrusion and uniaxial stretching of polypropylene (PP) films and filaments at corresponding conditions. Dies for extrusion of films and filaments were designed to achieve similar extrusion velocity and shear rates. Orientation in films and fibers of PP produced from these dies was determined by birefringence and wide‐angle X‐ray diffraction (WAXD). The degree of crystallinity was determined by density and WAXD. The superstructure developed during extrusion was studied in films by small‐angle light scattering. It was inferred that films and fibers prepared under similar conditions would produce similar morphology. Hence, films can be characterized by optical techniques when it is difficult to study fibers. © 1994 John Wiley & Sons, Inc.
Compatibilization of semicrystalline polymeric alloys through sepiolite addition
Authors: Herrero Consuelo R. , Morales Enrique , Acosta Jose Luis 
Published: April 2003

AbstractThis study was conducted to examine the possibilities offered by sepiolite as a compatibilizing agent in the incompatible blend consisting of poly(vinylidene fluoride) and polystyrene. The effect of sepiolite on the crystalline microstructure and morphology was determined through isothermal crystallization and spherulite growth of the system under study. The effect of sepiolite on the compatibility of the system was also studied. The glass‐transition temperature was determined, as well as the Flory–Huggins thermodynamic interaction parameter through two different routes: differential scanning calorimetry and inverse gas chromatography. A parallel study was conducted for the compatible system poly(vinylidene fluoride)/poly(methyl methacrylate). © 1994 John Wiley & Sons, Inc.
Biodegradable natural composites. II. Synergistic effects of processing cellulose with PHB
Authors: Gatenholm P. , Mathiasson A. 
Published: April 2003

AbstractThis article reports on the synergistic effects observed during the processing of cellulose with bacteria‐produced polyhydroxybutyrate (PHB). Cellulose fibers processed with PHB‐melt exhibited defibrillation as shown by SEM. Microscopic studies of extracted fibers demonstrated that a dramatic fiber‐size reduction occurred during processing. The size reduction was related to the degree of processing, which, we believe, depended on the amount of crotonic acid produced during thermal degradation of PHB. Size exclusion chromotography (SEC) studies of PHB samples thermally treated under well‐defined conditions showed a decrease in molecular weight as a function of treatment time. The samples processed with and without cellulose were analyzed for their molecular weight, and the processing of cellulose was found to contribute to a greater amount of chain scission, plausibly caused by local overheating as a result of shear forces developed during processing. Thermogravimetric studies performed isothermally on PHB under various temperatures gave correlations between the amount of volatile products and the molecular weight reduction of PHB. These findings confirmed our hypothesis on in situ formation of acid during melt processing of PHB and hydrolysis of cellulose fibers by such an acid during compounding. © 1994 John Wiley & Sons, Inc.
Radiation‐induced graft polymerization of vinyl benzyltrimethylammonium chloride onto polyethylene film
Authors: Nho Y. C. , Sugo T. , Tsuneda S. , Makuuchi K. 
Published: April 2003

AbstractAn attempt was made to introduce a strong base anion‐exchange group by radiation‐induced grafting of vinyl benzyltrimethylammonium chloride (VBTAC) onto polyethylene film. Both two‐step grafting and comonomer grafting techniques were tried owing to the difficulty of direct graft polymerization of VBTAC onto polyethylene. 2‐Hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA), having the same backbone structure except that the hydroxyl group of HEMA was grafted onto the polyethylene film and then VBTAC was grafted to examine the reactivity of VBTAC with each grafted polyethylene film. Co‐grafting of the binary mixtures of VBTAC and HEMA, or EMA, onto polyethylene film was also carried out. © 1994 John Wiley & Sons, Inc.
Solvent‐induced structural changes in sulfonated poly(ethylene terephthalate) (SPET) fibers
Authors: Timm Debra A. , Hsieh You‐Lo 
Published: April 2003

AbstractThe microstructure and macrostructure of sulfonated poly(ethylene terephthalate) (SPET) fibers were studied by subjecting them to solvents with solubility parameters similar to those of the PET. Dimethyl sulfoxide (DMSO), methylene chloride (MeCl2), and pyridine, whose solubility parameters (δ) are close to those of the flexible aliphatic ester segment (COOCH2CH2), the semirigid aromatic segment (COC6H4), and the average δ of the PET repeating unit, respectively, were used. The solvent uptake levels of these three solvents, which were not affected by crimping or relaxing processes of the fibers, were related to their sizes, shapes, and solubility compatibility with SPET. The solventinduced effects were strongly dependent upon the fiber structure caused by the fiber‐forming processes, but were generally not as strong as the processes. The most distinct changes brought about by the solvents include overall orientation determined by birefringence and the trans–gauche ratio and extent of chain fold by FTIR measurements. © 1994 John Wiley & Sons, Inc.
Influence of reaction temperature on direct esterifications in a continuous recycling process between terephthalic acid and ethylene glycol
Authors: Yamada Toshiro 
Published: April 2003

AbstractSimulations were carried out with a continuous recycle esterification model for the terephthalic acid–ethylene glycol (TPA–EG) system proposed previously. The influence of reaction temperatures, recycle ratios, and residence times on the oligomer characteristics was examined and the following results were obtained: (1) The main reactions proceed more under higher reaction temperatures, but the side reactions on diethylene glycol (DEG) proceed further than do the main reactions. (2) The higher residence time ratio of the first reactor to the total results in the proceeding of esterifications, which becomes remarkable as the temperature becomes high. (3) As the recycle ratio becomes high, the esterfications proceed, but in the very high degree of esterification, the tendency is reversed. (4) The characteristics of oligomer are almost the same at the same degree of esterification, independent of the reaction conditions. © 1994 John Wiley & Sons, Inc.
Studies on the sulfonation of poly(phenylene oxide) (PPO) and permeation behavior of gases and water vapor through sulfonated PPO membranes. I. Sulfonation of PPO and characterization of the products
Authors: Fu Hongyong , Jia Lianda , Xu Jiping 
Published: April 2003

AbstractPoly(2,6‐dimethylphenylene oxide) (PPO) was sulfonated to varying degrees using different sulfonating agents. Physical properties such as solubility, density, and thermal properties were studied for both PPO and sulfonated PPO (SPPO) with different degrees of sulfonation. Density and Tg value were increased after sulfonation. The solubility in dipolar aprotic solvents was improved and was dependent on the degree of sulfonation, and the thermal stability of PPO was slightly decreased after sulfonation. © 1994 John Wiley & Sons, Inc.
High‐energy radiation‐resistant elastomeric vulcanizates. I. Chlorosulfonated polyethylene
Authors: Shah Chaianya S. , Patni Mahendra J. , Desai Manish R. , Pandya Madhav V. 
Published: April 2003

AbstractIn this article, a detailed study on the stabilization of chlorosulfonated polyethylene (CSP) vulcanizates in γ radiation is reported. The special additives (antirads) for the stabilization are synthesized from polynuclear aromatics and formulated in the laboratory. The effect of these antirad formulations on the physicochemical structure and performance properties of these materials is studied by monitoring the degradation in γ radiation using resistivity, wide‐angle X‐ray diffraction, and mechanical properties. Antirad formulations to stabilize CSP against a total dosage of 200 Mrads of γ radiation have been achieved. © 1994 John Wiley & Sons, Inc.
Kinetics studies of two‐stage soapless emulsion polymerization of butyl acrylate and methyl methacrylate
Authors: Lee Chia‐Fen , Lin Kuen‐Rong , Chiu Wen‐Yen 
Published: April 2003

AbstractIn this work, butyl acrylate (BA) and methyl methacrylate (MMA) were used as monomers and K2S2O8 was used as the initiator to study the kinetics of two‐stage soapless emulsion polymerization. The first stage of the reaction was to synthesize polyBA (PBA) seeds, and the second stage of the reaction was a seeded polymerization of MMA. The results showed that an increase of initiator concentration would increase the rate of polymerization and the number of polymer particles, but would decrease the size of the polymer particles and the weight‐average molecular weight of the polymers. On the other hand, a decrease of the weight ratio of BA/MMA caused a decrease in the reaction rate and the weight‐average molecular weight of the polymers in the second stage of the reaction. The morphology of emulsion particles was observed from transmission election microscopy (TEM). The polymer particles were very uniform in size and showed coreshell morphology with PBA as a core and poly MMA (PMMA) as a shell. © 1994 John Wiley & Sons, Inc.
Proton‐exchange membranes by radiation grafting of styrene onto FEP films. II. Mechanism of thermal degradation in copolymer membranes
Authors: Gupta B. , Highfield J. G. , Scherer G. G. 
Published: April 2003

AbstractThe thermal degradation of radiation‐grafted and sulfonated FEP‐g‐polystyrene membrane has been investigated in the temperature range 50–650°C in an inert gas atmosphere by thermogravimetry. The evolved gaseous products were analyzed by FTIR in combination with mass spectrometry to correlate weight losses at different temperatures with molecular composition of the copolymer membrane. On the basis of these results, a simple degradation model has been established. © 1994 John Wiley & Sons, Inc.
Effect of functional groups on the triboelectric charging property of polymer particles
Authors: Kamiyama Masafumi , Maeda Masahiro , Okutani Haruo , Koyama Kikuhiko , Matsuda Hideomi , Sano Yoshiki 
Published: April 2003

AbstractTriboelectrification of small polymer particles (< 10 microns) in which various functional groups are introduced by addition of substituted comonomers is studied. The particles are produced by suspension polymerization and mechanical crushing of larger particles. The effect of the different production methods on the particle is described. The particles produced by the polymerization method have a spherical shape with a smooth surface, and those produced by the crushing method have an irregular shape. Studies show that particles that have easily ionizable functional groups are charged more effectively. It is believed the iontransfer route is the dominant mechanism in the triboelectrification charging of the particle. The magnitude of charge becomes saturated after 0.5% addition of substituted comonomers in the particles. The particles produced by the polymerization method have a tendency to be charged effectively compared with those produced by the crushing method. © 1994 John Wiley & Sons, Inc.
Effects of weathering, scale, and rate of loading on polycarbonate fracture toughness
Authors: Kim A. , Bosnyak C. P. , Chudnovsky A. 
Published: April 2003

AbstractThe fracture toughness of polycarbonate specimens of 3–9 mm thickness obtained from an actual aircraft canopy, were studied under accelerated weathering conditions and different rates of loading. Although no significant effects of thickness and loading rate on the critical stress intensity factors were observed, two different failure modes, brittle fracture and ductile fracture triggered by “pop‐in,” were observed. The mode of failure was a random event and the probability of ductile failure associated with pop‐in increases with the weathering time. More insight to material characteristics are gained through analysis of the specific fracture energy (SFE). The average values of SFE decrease monotonically with accelerated weathering time. This effect is ascribed to physical aging of the PC in the weatherometer that was corroborated through increases in density. The values of SFE seem to correlate with the probability for ductile fracture. This information can be used to establish conservative critical stress values for design. © 1994 John Wiley & Sons, Inc.
Structure and properties of liquid crystalline naphthalenediol copolyesters
Authors: Li Xin‐Gui , Zhou Zheng‐Long , Wu Xiu‐Ge , Sun Tong 
Published: April 2003

AbstractThermotropic liquid crystalline copolyesters with 1.4‐, 1.5‐, and 2.7‐naphthalenediol (NDO) units were prepared by molten‐state copolycondensation. It was found that the chain structure of the copolyesters is almost the same as the structure of recurring moieties of five units. The copolyesters have a glass transition temperature above 381 K, decomposition temperature above 703 K, and melting temperature between 513 and 559 K and their melts exhibit nematic texture and stir opalescence. The copolyester melts show a usual rheological behavior depending on the NDO unit content, but much lower extrudate swell. Light‐scattering patterns of the copolyester films with low crystallinity are clearly asymmetric and therefore indicate the existence of preferred orientation of the copolyester chains. Scanning electron microscopy observation suggests that the as‐spun fibers of 2.7‐NDO‐containing copolyesters were highly oriented and fibrillated. © 1994 John Wiley & Sons, Inc.
Permeability of PEEK to carbon dioxide
Authors: De Candia F. , Vittoria V. 
Published: April 2003

AbstractSorption and diffusion of carbon dioxide were measured in amorphous and crystalline poly(aryl‐ether‐ether‐ketone) or PEEK, at different temperatures. The sorption follows Henry's law at all the investigated temperatures, and the reduction of sorption in the crystalline sample corresponds to the reduction of the amorphous phase as derived from X‐rays. Due to a more tortuous path, the diffusion parameter in the crystalline sample is lower than in the amorphous one, whereas the activation energy of the diffusion process is similar for both the samples. The permeability to carbon dioxide was very low, comparable, or lower than other rigid polymers. © 1994 John Wiley & Sons, Inc.
A 13C NMR study of polyflavonoid tannin adhesive intermediates. I. Noncolloidal performance determining rearrangements
Authors: Pizzi A. , Stephanou A. 
Published: April 2003

AbstractChemical and heat treatments introduce noticeable modifications on the structure of four different polyflavonoid tannin extracts during their modification for use as tannin‐form aldehyde polycondensates. Such modifications are performance determining and account for the profound differences in behaviour of the four tannin extracts when used as tanninformaldehyde adhesives. Such modifications are directly followed by 13C NMR on the tannin extracts. Although some of the modifications observed by 13C NMR appear to correlate well with previous findings by model compounds studies, others could only be observed by 13C NMR of the modified tannin extracts themselves. Structural rearrangements to phlobatannins, depolymerization, recyclation, rearrangement of the type of interflavonoid monomer links, and autocondensation have been followed by 13C NMR and found to occur to different extents in the four tannins accounting for many of their differences in adhesive performance and characteristics. A novel reaction of autocondensation was observed for pecan nut pith tannins, which is different in applied characteristics from other polyflavonoid tannin adhesives. © 1994 John Wiley & Sons, Inc.