bluuebunny/crossref_metadata_2025 huggingface dataset:
The synthesis and gas‐transport properties of some hydrosilylation condensation polymers
Authors: Rickle Greg K.
Published: April 2003

High‐permeance collection layers are needed in composite membranes but few polymers have the required permeability. Hydrosilylation condensation polymers, because of their high silicon content, were thought to be good candidates to have high permeabilities. Several novel polymers were made and a new and simpler synthesis of ethynylated silanes is reported. One polymer, poly(divinyldimethylsilane‐co‐1,4‐bis [dimethylsilyl] benzene), appears to be of a liquid crystalline nature and has a low oxygen permeability (1.10 barrers). Two others [poly(diethynyldimethylsilane‐co‐1,4‐bis) [dimethylsilyl] benzene and poly(divinyldimethylsilane‐co‐p,p′diethynylbiphenyl‐co‐tetramethyldisiloxane)] were viscous liquids that could be thermally cured to give elastomers with oxygen permeabilities of ˜ 85 barrers. © 1994 John Wiley & Sons, Inc.
Structural changes and dyeability of silk fibroin fiber following shrinkage in neutral salt solution
Authors: Tsukada Masuhiro , Kato Hiroshi , Freddi Giuliano , Kasai Nobutami , Ishikawa Hiroshi
Published: April 2003

The fine structural changes of Bombyx mori silk fibroin fibers, induced by shrinking with concentrated calcium chloride aqueous solution at elevated temperature were investigated as a function of shrinking rate. Tensile strength decreased and elongation at break increased in the shrinkage range 13–67%, the shape of the stress–strain curve changing from rubberlike to brittle at high shrinkage values (70–90%). The birefringence gradually decreased over the entire shrinking range examined, the curve becoming steep as the shrinkage exceeded about 67%. The behavior of isotropic refractive index (niso) closely resembled that of birefringence (Δn) in the shrinking range 13–67%. Beyond shrinkage of 67%, the niso showed a tendency to increase, especially for the sample with 80% shrinkage. Dichroism measurements showed that the molecular orientation within the amorphous regions decreased sharply at the beginning of the shrinking treatment, within the range 0–13%, then attained a saturation at about 55%. The position and intensity of the major X‐ray diffraction peak at 20.5° remained essentially unchanged regardless of the shrinking treatment. The results of dyeing behavior showed that the saturation value attained by shrunk silk fibers was significantly larger than that of the untreated control sample. Both standard affinity and the heat of dyeing increased slightly for the shrunk silk fibroin fiber, suggesting that a larger number of reactive sites became available for the interaction between dye molecules and fibroin chains. A schematic model is proposed for explaining the relation between structural changes and enhanced dyeability of the silk fibers following shrinkage in neutral salt solution. © 1994 John Wiley & Sons, Inc.
Influence of electrolyte on electrical properties of thin cellulose acetate membranes
Authors: Friebe A. , Moritz W.
Published: April 2003

The electrical behavior of thin cellulose‐2.5‐acetate membranes for chemical semiconductor sensor applications was investigated. The influence of electrolyte on the electrical membrane properties was studied by means of electrochemical impedance spectroscopy. The polymeric membranes can be described using the electrical model of Cole and Cole. The membrane electrolyte distribution equilibria were investigated by means of an absorption–desorption method using conductivity measurements. The desorption kinetics for thin cellulose acetate membranes differ significantly from those of thicker cellulose acetate reverse osmosis membranes because here the rate of the ionic exchange at the membrane interface cannot be neglected. The experimentally determined distribution coefficients were used for the discussion of the electrolyte influence on the electrical membrane parameters. A functional dependence was found between the specific membrane resistance of cellulose acetate membranes and the ionic hydration enthalpy. The effect of electrolyte on the relative permittivity can be explained by a theoretical model. © 1994 John Wiley & Sons, Inc.
Crystallization of nylon 6–clay hybrid by annealing under elevated pressure
Authors: Kojima Yoshitsugu , Matsuoka Takaaki , Takahashi Hideroh , Kurauchi Toshio
Published: April 2003

Nylon 6–clay hybrid (NCH) is a molecular composite of nylon 6 and uniformly dispersed silicate layers of montmorillonite. We found that the phase with the high melting temperature (HMT phase) in the NCH annealed under elevated pressure. The melting temperature of the HMT phase was 240°C. Nylon 6 annealed under elevated pressure did not have the HMT phase. Thus, the presence of the HMT phase was characteristic of the NCH. The relative heat of fusion of the HMT phase (heat of fusion of HMT phase/heat of fusion in the pressure annealed NCH) increased with increase in pressure. High‐pressure differential thermal analysis (DTA) measurement revealed that the temperature, at which the relative heat of fusion showed a maximum value, was below about 20°C of the melting temperature of the original NCH under elevated presssure. It was considered that the nylon 6 crystallite near the melting temperature and the molecular mobility under elevated pressure were necessary to the appearance to the HMT phase. © 1994 John Wiley & Sons, Inc.
Fatigue‐resistant nylon alloys
Authors: Wyzgoski M. G. , Novak G. E.
Published: April 2003

Crystalline 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

Hydroxyterminated 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

The 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

Interpenetrating 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

In 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

Synthesis 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

In 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

This 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

This 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

An 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

The 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

Simulations 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

Poly(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

In 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

In 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

The 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

Triboelectrification 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

The 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

Thermotropic 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

Sorption 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

Chemical 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.
Chemical crosslink densit and network structure of natural rubber vulcanizates modified with phosphorylated cardnol prepolymer
Authors: Menon A. R. R. , Pillai C. K. S. , Nando G. B.
Published: April 2003

The chemical crosslink density (CLD) and network structure of natural rubber (NR) vulcanizates, modified with phosphorylated cardanol prepolymer (PCP), have been studied by equilibrium swelling and other chemical methods. The PCP‐modified NR vulcanizates showed lower CLD, as compared to the unmodified NR samples, the decrease being lesser for the semiefficient vulcanization (SEV) system, as compared to the conventional (CV) and efficient (EV) vulcanization system. The superior tensile characteristics of the PCP‐modified vulcanizates of the SEV system is presumed to be partly due to the presence of an entangled network structure between the aliphatic segment of PCP and the isoprene chains, as evident from X‐ray diffraction studies. The critical role of Zn++ions in the crosslinking reactions, especially at higher concentrations of PCP, was evident from the increase in CLD at higher concentrations of ZnO. The reduction in the IR absorption intensity, in the presence of ZnO, indicated the probable complex formation of Zn++ions with the phosphate groups of PCP. © 1994 John Wiley & Sons, Inc.
Diffusion of methyl esters of higher fatty acid in polypropylene
Authors: Hayashi Hiromichi , Sakai Hiroshi , Matsuzawa Shuji
Published: April 2003

Diffusion coefficients of several methyl esters of linear higher fatty acid (C10˜C18) into polypropylene (PP) were determined, over the temperature range of 50 to 110°C, using a mass uptake technique. The relations between an amount of mass uptake and t1/2 were linear within 10 min, indicating Fickian diffusion. The diffusion coefficients were in the range of 4.6×10−8 to 6.2×10−12 cm2 sec−1, increased with temperature, and decreased with increasing n‐alkyl chain length of fatty acid. The plots of In D vs. the molecular weight of methyl esters were approximately linear. The temperature dependence of diffusion followed an Arrhenius relationship, and the activation energies were in the range of 133 ˜ 147 KJ mol−1 and increased with an increase in n‐alkyl chain length of corresponding fatty acid. The diffusion coefficients were discussed with the interaction between methyl esters of higher fatty acid and PP. The diffusion coefficients of methyl esters, at the simultaneous diffusion process, were always higher than that derived from the single diffusion process, except for methyl decanoate with lower molecular weight. The difference in diffusion coefficients in single and simultaneous diffusion was discussed thermodynamically. © 1994 John Wiley & Sons, Inc.
On the effect of treating poly(acrylic acid) with argon and tetrafluoromethane plasmas: Kinetics and degradation mechanism
Authors: Terlingen Johannes G. A. , Takens Gijsbert A. J. , Van Der Gaag Frederik J. , Hoffman Allan S. , Feijen Jan
Published: April 2003

Poly(acrylic acid) (PAAc) films were treated with either an argon or a tetrafluoromethane (CF4) plasma and subsequently analyzed with X‐ray photoelectron spectroscopy (XPS). PAAc films were decarboxylated during both types of plasma treatments. In addition, during the CF4 plasma treatment, the PAAc films became fluorinated. The plasma phase during the argon plasma treatment of PAAc films was investigated with optical emission spectroscopy. It was shown that during this plasma treatment carbon dioxide, water, and possibly hydrogen were liberated from the PAAc surface. By covering the surface of PAAc films with different materials (lithium fluoride, UV fused silica, and glass) during the plasma treatment, it was possible to differentiate between photochemically induced and particle‐induced changes of the surface. This method was used to show that decarboxylation during the argon plasma treatment was caused by vacuum UV radiation (wavelength < 150 nm) and the decarboxylation/fluorination during the CF4 plasma treatment was induced by reactive fluorine‐containing species from the plasma phase. Furthermore, during both processes, etching of the PAAc surface occurred. Based on these mechanisms, kinetic models were derived that could be used to describe the measured kinetic data adequately. © 1994 John Wiley & Sons, Inc.
The craze‐tip deformation zone in PC/SAN microlayer composites
Authors: Sung K. , Haderski D. , Hiltner A. , Baer E.
Published: April 2003

Crazing in styrene‐acrylonitrile copolymer (SAN) layers of polycarbonate (PC)/SAN microlayer composites and the deformation zone that formed in the PC layer in response to the stress concentration created at the PC/SAN interface by the craze tip were examined by optical and scanning electron microscopy. A 49‐layer composite with relatively thick layers, on the size scale of tens of microns, was chosen in order to confine interactions to the region of a single PC/SAN interface. The SAN craze density, which increased with applied stress, was shown to fit the Weibull distribution function. The distance between crazes was described by a correlation length, and the distribution of correlation lengths indicated that crazing occurred randomly in the SAN layers. In the PC layer, the crazetip deformation zone consisted of a colinear plastic zone together with a pair of microshearbands that grew away from the craze tip at an angle of about 45°. Assuming a blunted craze tip, the plastic zone was analyzed using the slip‐line field theory. The dependence of the micro‐shearband length on remote stress was similar to that predicted by both the BCS and Vitek models. © 1994 John Wiley & Sons, Inc.
Effect of compatibilization on the properties of polypropylene/polyamide‐66 (75/25 wt/wt) blends
Authors: Duvall J. , Sellitti C. , Myers C. , Hiltner A. , Baer E.
Published: April 2003

Interfacially compatibilized immiscible blends with an isotactic polypropylene matrix (PP) and dispersed polyamide‐66 (PA) were prepared by extrusion with anhydride‐grafted isotactic PP compatibilizers, one of high‐anhydride content (HAC, 2.7 wt % grafted maleic anhydride) and one of low‐anhydride content (LAC, 0.2 wt % anhydride). On a weight basis, HAC was more efficient than LAC in dispersing PA to submicron domains, but on a total weight % anhydride basis, both compatibilizers were equally efficient. Both compatibilizers imparted similar tensile strength improvement compared to an uncompatibilized blend. Maximum fracture strain was obtained at similar total anhydride content, but much higher maximum fracture strain was achieved with LAC than with HAC. Good adhesion in an 11.25 wt % LAC blend was seen at the microscale as fibrillar ligaments connecting PA particles to the drawn PP matrix. Interfacial failure was observed in a lower fracture strain composition, 11.25 wt % HAC. © 1994 John Wiley & Sons, Inc.
Modified lignosulfonate as adhesive
Authors: Chen Rubie , Wu Quoxiong
Published: April 2003

Oxidized lignosulfonate (LS‐OB) displays a high crosslinking during thermal condensation. When LS‐OB was used as a partial substitute of urea‐formaldehyde (UF) in wood adhesive, a positive effect on the curing of resin could be observed. With 30–40% substitution, no deteriment in strength properties of particleboard was observed. Polycondensation of lignin and UF could occur between methylol groups in UF resin and hydroxyl and carbonyl groups in lignin, through ether bonds and methylene bridges. A high surface activity of LS‐OB would reduce the surface tension of binder solution and facilitate its distribution on wood particles, improving consequently the strength properties of particleboard. © 1994 John Wiley & Sons, Inc.
Water absorption and disc cracking in urethane–methacrylate resins
Authors: Bucknall Clive B. , Zhang Xiang Cheng , Orton Michael L. , Jackson Graham V.
Published: April 2003

Water absorption at 23 and 100°C has been studied in three materials based on a single type of urethane–methacrylate resin: the neat resin, a rubber‐toughened blend containing 15 wt % of core‐shell modifier, and a filled rubber‐toughened resin containing 46 wt % silica plus 8 wt % core‐shell modifier. In all six absorption experiments, water diffusion followed Fick's law. However, in neat resin at 100°C, the period of Fickian diffusion, during which the material appeared to reach saturation, was followed by an additional period of water uptake, which was accompanied by formation of internal disc cracks up to 1 mm in diameter. At both 23 and 100°C, fracture of water‐saturated neat resin was defect dominated: cracks were initiated at inorganic impurities between 40 and 80 μm in diameter. The adverse effects of water are attributed to hydration and consequent swelling of these insoluble impurities. No internal cracking was detected in either the rubber‐modified or hybrid resin, which have higher a KICs than the neat resin. © 1994 John Wiley & Sons, Inc.
Crystallization processes in poly(ethylene terephthalate) as modified by polymer additives and fiber reinforcement
Authors: Reinsch Veronika E. , Rebenfeld Ludwig
Published: April 2003

The effect of fiber reinforcement on the crystallization kinetics of poly(ethylene terephthalate), or PET, was investigated using differential scanning calorimetry. The objective of the study was to determine how the effects of fiber reinforcement on PET crystallization are modified by the presence of polymer nucleating and plasticizing additives. Undirectional fiber composites were prepared using aramid and glass fibers in PET. The rate of crystallization of PET, as reflected by crystallization half‐time, is seen to depend on reinforcing fiber type, crystallization temperature, and presence of nucleant or plasticizer. Howerver, degree of crystallinity of PET is largely unaffected by the presence of additives and reinforcing fibers. Crystallization kinetics are analyzed using the Avrami model for PET volume crystallized as a function of time. Avrami plots for PET and fiber‐reinforced PET exhibit two linear regions, possibly corresponding to primary and secondary crystallization. The crystalline morphology of fiber‐reinforced PET was also studied using polarized light microscopy. Results concerning nucleation density and growth morphology are used in explaining differences seen in crystallization kinetics in fiber‐reinforced systems. © 1994 John Wiley & Sons, Inc.
Kinetics of synthesizing 2,4,6‐tribromophenyl benzyl ether in a triphase catalysis
Authors: Wang Maw‐Ling , Peng Ching‐Zou
Published: April 2003

The reaction of benzyl bromide with 2,4,6‐tribromophenol in an organic solvent/aqueous alkaline solution of KOH to synthesize 2,4,6‐tribromophenyl benzyl ether by triphase catalysis was investigated. The macroporous and microporous polymer pellets that served to support the catalyst were prepared by reacting styrene monomers, chloromethylstyrene monomers, and divinylbenzene in a suspension polymerization. Tributylamine was then immobilized on the surface of the polymer pellet to form the three‐phase phase‐transfer catalysts. The effects of the rate of agitation, degree of cross‐linking of the polymer, solvents, inorganic salts, and temperature on the conversion of benzyl bromide and the reaction rate in the three‐phase catalytic reaction were investigated in detail. We recommend that a macroporous polymer pellet with a small degree of cross‐linking be used to react in a highly polar solvent to obtain high conversion of benzyl bromide and a rapid reaction. © 1994 John Wiley & Sons, Inc.
Studies on the structure and properties of nylon 46 fiber. I. Dimensional stability
Authors: Kudo Kazushige , Mochizuki Masatsugu , Kiriyama Shunichi , Watanabe Masaharu , Hirami Matsuo
Published: April 2003

Thermal shrinkage, viscoelastic properties, wide‐ and small‐angle X‐ray diffractions, and molecular orientation by fluorescence method were measured for fiber samples of nylon 46 [poly(tetramethylene adipamide)] as compared with nylon 66 [poly(hexamethylene adipamide)]. The structural study of nylon 46 fiber indicated that molecular chains are well‐oriented along the fiber axis in the interlamellar region whose thickness is relatively thin. It was also shown that the onset of thermal movement of nylon 46 molecules is shifted to the higher temperature than nylon 66. These characteristics will be attributed to the cause of good dimensional stability, a significant feature of nylon 46 fiber, attractive for its application to industrial usages. © 1994 John Wiley & Sons, Inc.
Determination of functionality and functionality distribution of polyether polyols by quantitative 13C NMR spectroscopy
Authors: Carr Robert H. , Hernalsteen Jan , Devos Julien
Published: April 2003

A method is described for the determination of the number average functionality and functionality distribution of polyols based on the measured intensities of relevant end groups observed in 13C NMR spectra. Longitudinal (T1) relaxation time measurements on glycerol‐, trimethylolpropane‐, and pentaerythritol‐initiated copolymers of propylene oxide and ethylene oxide show that the slowest relaxing moiety that needs to be quantified is the vinyl CH2group of the unsaturated side product of the propoxylation reaction. A. chromium (III)‐containing relaxation reagent allows the analysis to be speeded up by decreasing the relaxation times. The relative precision of the functionality measurement is ca. ±1%, while determinations of the mole percentage levels of species with different functionalities can be carried out with a precision better than ±3 mol %. © 1994 John Wiley & Sons, Inc.
The cross‐linking of acrylic rubber in the presence of group IIB metal oxides
Authors: Chowdhury P. , Chakravorti M. C. , Das C. K.
Published: April 2003

Effects of group IIB metal oxides (viz., ZnO, CdO, and HgO) on ethylene thiourea (ETU) accelerated the curing of acrylic rubber (ACM) have been evaluated with a view to elucidate the cross‐linking mechanism with special reference to the role of metal oxides. Best results are obtained with CdO in the presence of ETU. ZnOCdO or CdOHgO blends provide no synergism in the state and rate of cure. Formation of metal sulfide and chloride during the cross‐linking reaction has been confirmed by XRD and XPS. Examination of FTIR spectra reveals that cross‐linking occurs at the CCl cure site of the acrylic polymer. Based on spectral and chemical analysis, a reaction mechanism has been put forward. © 1994 John Wiley & Sons, Inc.
Measurement of diffusivity of a liquid diamine in solid epoxies using attenuated total reflectance infrared spectroscopy (FTIR‐ATR)
Authors: Skourlis T. P. , McCullough R. L.
Published: April 2003

A number of studies on thermosetting polymeric composite materials have indicated the existence of a three dimensional region of the matrix in the vicinity of the fiber, which exhibits distinct properties. A key factor in the interphase formation of epoxy‐diamine mixtures is the diffusivity of the diamine relative to the epoxy prepolymer. A technique for measuring diffusion coefficients of a liquid through solid polymeric thin layers is described. Infrared attenuated total reflectance (ATR) spectroscopy is used to analyze diffusion couples with infrared distinguishable bands. A cylindrical germanium crystal, coated with the polymeric layer of interest, is immersed in a boat cell filled with the diffusant, and infrared spectra of the system are taken in real time. By those means, only the region close to the solid surface is scanned without interferences from the bulk. The temperature dependence of diffusivity can also be evaluated by the use of a heated cell. Diffusivities that are evaluated in this way can be used to predict stoichiometric gradients during the curing reaction of the system and, therefore, the structure and property gradients of the material around the fiber. © 1994 John Wiley & Sons, Inc.
NMR study of the stabilities of urea–formaldehyde resin components toward hydrolytic treatments
Authors: Chung I‐Ssuer , Maciel Gary E.
Published: April 2003

The solid residues of nine urea–formaldehyde (UF) resins after hydrolytic treatment at pH4 and 86°C for 20 h and the solid residues of one UF resin after eight different hydrolytic treatments were examined by 13C‐CP–MAS NMR. The relative stability toward hydrolysis of each structural component in each UF resin was established for various hydrolytic conditions. In general, UF resins prepared from starting mixtures with a formal F/U molar ratio of 1.00 show a high degree of stability toward hydrolysis. Cross‐linking methylene linkages in the UF resins show a higher susceptibility to hydrolytic treatments at pH 4 and 86°C than do linear methylene linkages. UF resins prepared with an F/U molar ratio of 2.00 are susceptible to hydrolysis at pH 4 and 86°C. Dimethylene ether linkages, methylols attached to tertiary amides, and poly(oxymethylene glycol) moieties are probably the main formaldehyde emitters in UF resin products. © 1994 John Wiley & Sons, Inc.
Microfiber formation: Immiscible polymer blends involving thermoplastic poly(vinyl alcohol) as an extractable matrix
Authors: Robeson Lloyd M. , Axelrod Robert J. , Vratsanos Menas S. , Kittek Margaret R.
Published: April 2003

The utilization of polymer‐blend technology to prepare microfibers via extraction of one of the components is known technology. Achieving fibrillation (microfiber formation) is not an a priori consequence of polymer blends exposed to a shear or elongational flow field. The viscosity ratio, concentration ratio, interfacial tension, and second normal stress function have all been noted to be important factors in achieving fibrillation in polymer blends. It has been found that thermoplastic poly(vinyl alcohol) is particularly effective in this technology, yielding fibrillated systems that can be easily extracted to yield microfibers (0.1–5 μ diameter). Thermoplastic poly(vinyl alcohol) (PVOH) offers cold‐water solubility, biodegradability, and fibrillation characteristics with many commodity polymers (polyolefins, polystyrene, scrap mixtures), thus offering advantages over previously investigated extractable polymers. In addition, the resultant microfibers via this process can be pulped and handled in paper‐making processes. The process for microfiber formation, the process variables, the polymers applicable to the formation of microfibers using PVOH as an extractable matrix, and the properties of the resultant microfibers are discussed with emphasis on the characterization of the microfibers as a fibrous thixotrope additive. Potential utility of the microfibers via this process include polymeric paper and admixtures with cellulosic‐based pulp, oil‐ or water‐adsorbent mats, fibrous thixotrope additives, filters, filler rentention and pitch control in paper applications, and ultralow denier fibers. © 1994 John Wiley & Sons, Inc.
13C CP–MAS NMR study of absorbed water in polyimide film
Authors: Waters J. F. , Likavec W. R. , Ritchey W. M.
Published: April 2003

Solid‐state nuclear magnetic resonance (NMR) relaxation studies were performed on Kapton H polyimide films in order to determine the location of water absorption within the polymer lattice and its effects on the microdomain properties of the polymer. Carbon spin lattice relaxation (13CT1), spin lattice relaxation in the rotating frame (T1ρ), and inversion recovery cross polarization (IRCP) experiments were performed to analyze wet and dry Kapton films and films exposed to D2O. The conventional pulse sequences for these experiments were modified with a TOSS acquisition sequence in order to remove spinning side bands from the 13C‐NMR spectra. The data indicates that the water molecules aggregate near the carbonyl group of the imide ring and are most probably bound via hydrogen bonding. Additionally the water molecules plasticize the polymer network by increasing the amplitude of low‐frequency motions. © 1994 John Wiley & Sons, Inc.