bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and application of low molecular weight poly(vinyl chloride). II. Thermal stability of blended poly(vinyl chloride)
Authors: Yamamoto Kikuo , Maehara Takashi , Mitani Katsuo , Mizutani Yukio
Published: April 2003

The blending effect of poly(vinyl chloride) (PVC) with relatively higher molecular weight (HMW‐PVC) and relatively lower molecular weight (LMW‐PVC) has been investigated by measuring various thermal stability and fusion times. The thermal stability of the blended PVC is improved when the small amount of LMW‐PVC obtained using mercapto compounds as a chain‐transfer agent is blended into PVC with HMW‐PVC. At the LMW‐PVC content from about 5–30 wt %, the thermal stability of the blended PVC is much more improved. Furthermore, the blended PVC with LMW‐PVC, obtained using mercapto compounds, exhibits significant improvement in the discoloration time. The fusion time of the blended PVC is related to the weight‐average polymerization degree of LMW‐PVC and the LMW‐PVC content. © 1994 John Wiley & Sons, Inc.
Molecular weight characterization of fluoropolyoxyalkylenes by gel permeation chromatography
Authors: Gianotti G. , Levi M. , Turri S.
Published: April 2003

Conditions required for the molecular weight and molecular weight distribution determination of fluoropolyoxyalkylenes by gel permeation chromatography are reported and discussed. Experimental work was carried out with three series of narrow fractions of oligomers having the same perfluorinated copolymeric body and three different types of chain ends. The same calibration curve describes very well the behavior of the three series of samples, so that a “size‐exclusion” mechanism of the molecular separation can be postulated practically. © 1994 John Wiley & Sons, Inc.
Solutions spinning of the high Tc oxide superconductor. II. Effect of organic acid on the complex formation of PVA with the copper (II) ion
Authors: Tomita Hisayo , Goto Tomoko
Published: April 2003

As basic research for the solution spinning of the high Tc oxide superconductor, the effect of organic acid on the complex formation of poly(vinyl alcohol) (PVA) with the copper [Cu(11)] ion was explored with various carboxylic acids, such as formic acid, acetic acid, n‐butylic acid, and lactic acid. The effects of these acids on the interaction between PVA and Cu(II) acetate in aqueous solution were nonexistent, while a chelation of the Cu(II) ion and lactic acid was detected. In the solid state, a linear complex of PVA with the Cu(II) ion was formed by adding organic acid. The ligand of the linear complex was highly dependent on the kind of acid used. © 1994 John Wiley & Sons, Inc.
Syntheses and nonlinear optical properties of polymers prepared from chloromethylstyrene
Authors: Zerroukhi A. , Trouillet A. , Blanc D. , Boinon B. , Cachard A. , Montheard J. P.
Published: April 2003

The synthesis and characterization of new dyes, prepared in two steps from chloromethylstyrene, and containing azo moieties or stilbene are reported. All synthesized monomers show spectroscopic properties (nuclear magnetic resonance, ultravoilet) in accordance with the attempted structure. These monomers have been copolymerized with styrene and the nonlinear optical properties of the new compounds and those of previously described polymeric imines have been studied via second harmonic generation. © 1994 John Wiley & Sons, Inc.
Surface properties and flocculations of globulin‐immobilized fine polymer particles
Authors: Tamai Hisashi , Sakurai Hiroyuki , Suzawa Toshiro , Yasuda Hajime
Published: April 2003

Characteristics of globulin‐immobilized styrene/acrylamide/acrylic acid copolymer [poly(St/AAm/AA)] fine particles and their flocculation by an antigen–antibody reaction were investigated as a function of acrylamide (AAm) content. Immobilization of globulin was carried out through octamethylenediamine with a carbodiimide reaction. The increase in AAm content in particles decreases the amounts of bovine γ‐globulin (BγG) immobilized, shifts the isoelectric points of BγG‐immobilized poly(St/AAm/AA) particles to acidic pH, and increases the dispersion stability of BγG‐immobilized poly(St/AAm/AA) particles. The flocculation rates of antihuman epidermal growth factor (hEGF) immunoglobulin (IgG)‐immobilized poly(St/AAm/AA) fine particles of low AAm content by the antigen‐antibody reaction are higher than that of anti‐hEGF IgG‐adsorbed polystyrene particles, whereas those of high AAm content are lower and decreased with increasing AAm content. © 1994 John Wiley & Sons, Inc.
Fracture mechanics investigation on the PP/EPDM/ionomer ternary blends using j‐integral by locus method
Authors: Ha Chang‐Sik , Kim Youngkyoo , Cho Won‐Jei
Published: April 2003

The fracture mechanics investigation of the polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM)/ionomer ternary blends was performed in terms of the J‐integral by measuring fracture energy via the locus method. Blends were prepared in a laboratory internal mixer. The composition of PP and EPDM was fixed at a 50/50 ratio by weight. Two kinds of Poly(ethylene‐co‐methacrylic acid) (EMA) ionomers were used. The J‐integral value at crack initiation, Jc, of the PP/EPDM/EMA ionomer ternary blends were affected by the cation types (Na+ or Zn2+) and contents (5–20 wt %) of the added EMA ionomers. The ternary blend having 5 wt % of Na‐neutralized ionomer showed a higher Jc value than that of any other ternary blends. The results were discussed with regard to the fracture topology by a scanning electron microscope (SEM). © 1994 John Wiley & Sons, Inc.
The method of measuring macromolecular entanglements of polymers using swelling differential scanning calorimetry (DSC)
Authors: Qin Jian , Hu Panpan , Zhao Jiongxin , Wu Zongquan , Qian Baojun
Published: April 2003

Since Bueche, Graessley, Onogi, etc., advanced the concept of macromolecular entanglements, the subject has been studied extensively. So far, there are two kinds of methods of measuring the entanglements in a polymer system: One is the measurement of viscosity or other related properties of polymer fluids, either melts or solutions; the other is the measurement of modulus or other related properties of completely amorphous polymers. Until now, the effective method of measuring macromolecular entanglements for crystalline or semicrystalline polymers and fibers has not been developed. We report here a new method of measuring macromolecular entanglements of polymeric solids—using swelling differential scanning calorimetry (swelling DSC or SDSC), and we prove that the entanglements in fibers and polymeric materials can be measured quickly and conveniently with this method. © 1994 John Wiley & Sons, Inc.
Application of NMR cross‐polarization/modulus correlations to a series of polyurethane elastomers
Authors: Marcinko J. J. , Parker A. A. , Rinaldi P. L. , Ritchey W. M.
Published: April 2003

A structure/property relationship is developed between the dynamic storage modulus, E′, and the cross‐polarization time constant TCH for a series of polyurethane elastomers. The correlations made are based on the standard linear solids model (SLSM) and on the concept that TCH is modulated by near static molecular motions. The use of the SLSM to describe the main viscoelastic range of these polyurethanes is contrasted to previous models used to develop similar correlations. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of acrylonitrile onto cotton cellulose by potassium permanganate–thioacetamide redox system
Authors: Eromosele Ighodalo Clement
Published: April 2003

The graft copolymerization of acrylonitrile onto cotton, initiated by the KMnO4–thioacet‐amide redox system in an aqueous medium, has been investigated. The percentage graft yield was determined by varying the concentrations of KMnO4, acrylonitrile, thioacetamide, and temperature. The percentage graft yield increased initially and then decreased with increasing concentrations of KMnO4 and thioacetamide, with an optimum yield not greater than 21%. The percentage graft yield, however, was greatly enhanced with a value of up to 66% as the concentration of acrylonitrile was increased. The percentage graft yield increased with temperature in the range of 35–70°C with a calculated activation energy of 8.33 Kcal/mol. The effects of solvents and amines on the percentage graft yield were also investigated. © 1994 John Wiley & Sons, Inc.
Solubility parameters of poly(4‐substituted α‐acetoxystyrenes) and alternating copolymers of vinylidene cyanide with substituted styrenes
Authors: Belfkira Ahmed , Montheard Jean‐Pierre
Published: April 2003

The δ solubility parameters of three families of polymers have been determined by two calculation methods suggested by Small and Hoy. Hansen's model has also been used to assess δ and its components δd0, δp0, and δh0, so as to obtain more information on the intensity of the forces between the chain segments. Knowing the microstructure, the tacticity, and the thermal behavior of the copolymers has made it possible to explain both the different values of δ and the progression of solubility areas. Using Teas' method has made it possible to visualize on the same map the influence of the forces of interaction. This representation shows that the presence of the vinylidene cyanide unit in styrenic chains implies an increase of δp and a decrease of δd, whereas δh remains roughly constant for the corresponding homopolymer. © 1994 John Wiley & Sons, Inc.
Carbon‐13 NMR investigation of spin‐lattice relaxation mechanism of poly(4‐methyl‐1‐pentene)
Authors: Ma Sun , Chen M.‐C. , Wang S.‐P.
Published: April 2003

Carbon‐13 spin‐lattice relaxation rates (1/T1) and nuclear Overhauser enhancement (NOE) measurements were performed on poly(4‐methyl‐1‐pentene) above the glass transition temperature in order to explain the segmental motion of the molecule by means of high resolution nuclear magnetic resonance spectroscopy. Experiments were carried out for poly(4‐methyl‐1‐pentene) with low, medium, and high molecular weights. The similarity of the T1 values showed that for polymers with a degree of polymerization (DP) > 100 the relaxation behavior of the carbon atoms no longer depends on molecular weight. The temperature effects were studied at 358, 363, 373, 383, 393, and 403 K, both on 25.18 and 100.61 MHz magnetic fields. Finally, several mathematical T1 models were applied to study the change of T1 encountered by the individual carbon atoms. The results reveal that the more factors being considered in the calculation the more consistent will be the results obtained with the T1 model. A comparison showed that parameters used in the DLM T1 model gives the best fit. © 1994 John Wiley & Sons, Inc.
Thermal behavior of p‐acryloyloxy‐tri‐n‐butyltin benzoate–acrylonitrile copolymers
Authors: Azab M. M.
Published: April 2003

The copolymerization of p‐acryloyloxy‐tri‐n‐butyltin benzoate (ABTB) with acrylonitrile (AN) has been investigated in dimethylformamide (DMF), using azobisisobutyronitrile (AIBN) as an initiator. The prepared homopolymer of (ABTB), as well as the copolymers, were characterized by a variety of analytical, spectral, and thermal methods. Thermogravimetry (TG) and differential thermal analysis (DTA) data showed a little improvement in the thermal behavior of the investigated copolymer. A mechanism for the initiation of ABTB units in the nitrile oligomerization in the copolymer was also proposed. © 1994 John Wiley & Sons, Inc.
Adhesive monomers to dental ceramics. II. Methacrylamide derivatives containing carboxyl and phenyl groups for effective adhesion of calcium metaphosphate ceramic
Authors: Kitoh Shinya , Suzuki Kunitomo , Kiyohara Takao , Kurita Keisuke
Published: April 2003

Twelve methacrylamide derivatives containing carboxyl and phenyl groups have been evaluated as adhesives for calcium metaphosphate ceramic, a promising but hard‐to‐adhere cast ceramic restoration material. Although methacrylamide monomers having a carboxyl group showed low adhesive tensile strength for the ceramic, contrary to the glycidyl methacrylate derivatives, the monomer having neighboring two carboxyl groups at the phenyl ring exhibited quite high adhesion. Moreover, the monomer proved to retain high adhesion strength for the surface‐etched ceramic for a long period of time even in water and would thus be suitable for practical clinical applications. © 1994 John Wiley & Sons, Inc.
Preparation of superconducting edge junctions using polymeric Langmuir–Blodgett films as barrier layers
Authors: Liu Yun Qi , Zhang Jin Biao , Wu Pei Ji , Zhu Dao Ben , Sun Zhi Jian , Ji Zheng Ming , Yang Sen Zu , Wu Pei Heng
Published: April 2003

Aromatic polyamic acid alkyl ammonium salt exhibits very good transfer behavior under suitable deposition conditions. A superconducting thin film of YBa2Cu3Ox (YBCO) on Langmuir–Blodgett film (LB) has been obtained when the substrate temperature is higher than 500°C. Superconducting edge junctions of (Pb—In)/LB/(Pb—In) and YBCO/LB/YBCO incorporated with polyimide LB films were fabricated. Their current–voltage characteristics are discussed in terms of the temperature stability of polyimde LB films. © 1994 John Wiley & Sons, Inc.
Microstructure of charged mosaic membranes constructed by phase growth
Authors: Ishizu Koji , Iwade Masaya
Published: April 2003

A template pattern with alternating poly(4‐vinylpyridine) (P4VP)/poly(vinyl alcohol) (PVA) lamellae was fabricated upon a cross‐linked PVA film by casting of poly[4‐vinyl‐pyridine (4VP)‐g‐vinyl alcohol (VA)] graft copolymer. After a treatment involving the binding of a PVA film with the graft copolymer and also domain fixing of the PVA phases, a dilute solution of poly[acrylic acid (AA)‐benzyl N,N‐dimethyldithiocarbamate (DMTC)] copolymer/P4VP binary blend was cast on this template surface. The microstructure of binary blend was observed from scanning electron microscopy (SEM) by wet‐etching of films after domain fixing of one component of the binary blend. The poly(AA‐DMTC) copolymer/P4VP binary microdomains formed by phase growth were oriented perpendicularly to the film surface. We also fabricated these charged mosaic regions on a microporous poly(vinyl chloride) (PVC) membrane, and carried out the surface analysis by X‐ray photoelectron microscopy (XPS). Finally, we examined the transport of KCl through the charged mosaic composite membranes. © 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. III. Sorption behavior of water vapor in PPO and sulfonated PPO membranes
Authors: Jia L. , Fu H. , Xu J. , Hirai A. , Odani H.
Published: April 2003

Water vapor absorption and desorption by poly(phenylene oxide) (PPO) and sulfonated PPO (SPPO) membranes were studied at a constant temperature of 30°C and over a broad range of water activity (0.05 ≤ a < 0.8) by the weighing method. The experimental sorption isotherms of both PPO and SPPO possessed a general sigmoidal shape, which suggested that they belong to type II; thus, the data may be quantitatively analyzed according to the BET or GAB equation for multilayer sorption processes. The number of site‐bound water molecules per monomeric unit was increased by a factor of 150 after sulfonation of PPO. The features of the reduced absorption and desorption curves of both PPO and SPPO suggested that the sorption processes were non‐Fickian. The diffusion coefficient calculated from the slope of the initial linear part of the curves showed concentration dependence. The permeability of water vapor through SPPO was more pressure‐dependent than was that through PPO. The Flory–Huggins interaction parameter derived from experimental data on SPPO had a smaller value compared with that of PPO and was a monotonic increasing function of water activity in the low‐activity region and then leveled off at a > 0.6, showing a corresponding initial decrease of the polymer–water interaction, which then gradually reached a certain stable value. Water clustering for SPPO was much less than that for PPO, which is clear proof of its higher hydrophilicity. The results from this study showed that SPPO could be an excellent dehumidification membrane material. © 1994 John Wiley & Sons, Inc.
Deformation of rubber‐toughened polycarbonate: Macroscale analysis of the damage zone
Authors: Cheng Chihmin , Hiltner A. , Baer E. , Soskey P. R. , Mylonakis S. G.
Published: April 2003

Two commercial core‐shell rubbers were used as impact modifiers for polycarbonate (PC). Specimens with a single semicircular edge notch were stretched uniaxially in order to study the prefracture damage evolution of blends under a triaxial tensile stress state. The irreversible deformation of modified PC included a cavitation mechanism in addition to the three shear modes of unmodified PC. At the macroscopic level, the cavitation condition could be described by a mean stress concept. The corresponding critical volume strain for cavitation in PC blends was determined to be independent of rubber content but differed for the two impact modifiers. The critical volume strain for cavitation was used as an index of cavitation resistance for the impact modifiers. The effect of rubber content and temperature on Izod impact strength of the PC blends was also reported. From the relationship between the cavitation resistance and the Izod impact strength, it was proposed that impact modifiers with a higher cavitation resistance impart better toughness to blends with PC. © 1994 John Wiley & Sons, Inc.
Fractography and failure mechanisms of particulate‐filled thermoplastic polyester
Authors: Li J. X. , Hiltner A. , Baer E.
Published: April 2003

Fractography has been used for the postfailure analysis of a filled thermoplastic polyester. The five fracture modes that were previously defined on the basis of macroscopic stress–strain behavior were distinguished by certain fractrographic features. These features were characteristic of the fracture mode and did not depend on filler type or filler content. The Mode A ductile fracture surface consisted of two regions: a pullout region of slower crack growth and a rosette region of faster crack growth. The Mode B ductile fracture surface contained only a ductile pull out texture. The Mode C quasi‐brittle fracture surface exhibited secondary fracture features that sometimes included the herringbone pattern. The Mode D quasi‐brittle fracture surface consisted of a stress‐whitened dimple region and a brittle fracture region. The Mode E Fracture surface exhibited primarily the rough texture characteristic of brittle fracture. The failure mechanisms inferred from analysis of the fracture surfaces confirmed a microscopic failure model of the ductile‐to‐quasi‐brittle transition in filled PETG that is based on the strain‐hardening strength of the polymer ligaments between debonded filler particles. © 1994 John Wiley & Sons, Inc.
PVC/MBS blends with small concentrations of PET: Failure processes in thin films during uniaxial tension
Authors: Li J. X. , Twigg M. V. , Hiltner A. , Baer E.
Published: April 2003

The effects of small concentrations of poly(ethylene terephthalate) (PET) particles on the failure of poly(vinyl chloride), blended with a (methacrylate–butadiene–styrene) impact modifier (PVC/MBS) were studied. The failure processes arising from isolated and interacting particles were observed in situ in the optical microscope during tensile deformation. At low PET content ( < 0.5%), voids grew around individual particles without particle‐particle interaction. Subsequently, a stable neck developed, and the material experienced relatively large deformation before fracture. With increasing PET content and increasing particle size, particle–particle interactions were observed. At higher PET content (≥ 1%), the neck was not stable and fracture occurred during neck formation. Materials with larger particles exhibited neck instability and fracture at lower PET content. © 1994 John Wiley & Sons, Inc.
Application of scanning acoustic microscopy to polymeric materials
Authors: Lisy F. , Hiltner A. , Baer E. , Katz J. L. , Meunier A.
Published: April 2003

Scanning acounstic microscopy (SAM) is now a viable technique for the nondestructive evaluation of various materials. SAM is capable of distinguishing defect and discontinuities and/or the variations in elastic properties on a scale comparable to optical microscopy. The pulse mode utilizes a single narrow acoustic wave that permits surface and internal studies over a range of frequencies from 5 to 200 MHz with resolution down to approximately 20 μm. This technique was applied to image surface features of an opaque sheet‐molding compound and to analyze flow patterns of chopped glass fibers. The pulse mode was also used to image the internal damage sustained from a high‐speed projectile in oriented polypropylene and two carbon fiber‐reinforced composites, with different matrices. Most importantly, the pulse mode of the acoustic microscope is a nondestructive method and the interior of samples that are entirely opaque can be readily studied with this unique instrument. The burst mode is composed of a group of acoustic waves and is capable of operating at higher frequencies than the pulse mode up to several gigahertz. This mode permits resolution down to the micrometer level and is especially useful for investigating surface and subsurface microstructural features. The burst mode was used to determine the distribution of chopped fibers in a PEEK matrix and carbon black particulars in an adhesive, the orientation of the mineral phase and density variations in a single osteon from a dog femur, and the orientation of collagen fibers in sheep meniscus. Also, the sensitivity of the burst mode to surface features was used to examine the topographical features in a multilayer composite and a blend of poly(vinyl chloride) (PVC) with poly(ethylene terephthalate) (PET) particulates. © 1994 John Wiley & Sons, Inc.
Effects of water content on the properties of starch/poly(ethylene–vinyl alcohol) blends
Authors: Dell Paul A. , Kohlman William G.
Published: April 2003

The physical properties of unmodified starch, poly(ethylene vinyl alcohol), glycerol, and water mixtures are reported. Thermal and melt‐flow properties of the preprocessed, physically mixed materials were determined along with the tensile properties and morphology of injection‐molded microtensile samples. Melt‐flow properties were measured by a capillary rheometer, and the water content was varied from 4 to 18%. The morphology, rheology, and tensile properties are all highly related to the percentage of water present. A transition in the tensile properties and morphology of the blends was observed at approximately 11% moisture content. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Grafting poly(vinyl amine‐co‐acrylic acid)s on poly(vinylidene fluoride) membranes
Authors: Iwata Hiroo
Published: April 2003

In this study, N‐vinylacetamide (NVA) was graft‐polymerized and graft‐copolymerized with acrylamide (AAm) onto plasma‐activated surfaces. The polymer compositions of the grafted layer were estimated from X‐ray photoelectron spectroscopy spectra. N‐vinylacetamide was enriched in the grafted polymers in all regions of the monomer compositions. The primary amine groups could be densely introduced on the surface by hydrolyzing the grafted poly(vinylacetamide‐co‐acrylamide). © 1994 John Wiley & Sons, Inc.
Solvent replacement in the synthesis of persubstituted phosphonitrilic hydroquinone prepolymer materials
Authors: Femec Douglas A. , McCaffrey Robert R.
Published: April 2003

A desirable solvent replacement has been effected in the synthesis of persubstituted phosphonitrilic hydroquinone prepolymer materials. The replacement of carbon tetrachloride with cyclohexane has no adverse effect on the composition and quality of the material prepared. The overall yield of the reaction increases from 65 to 70% and the toxicity of the reaction mixture and of the waste generated from the reaction are greatly reduced. The particularly close match of solvent properties between carbon tetrachloride and cyclohexane makes this an excellent solvent replacement. Such changes to less‐expensive, less‐toxic, and less‐environmentally damaging solvents are on the increase. A brief list of some known replacement solvents for use in polymer and coatings applications is presented. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Mechanical properties of cellulose acetate propionate/aliphatic polyester blends
Authors: White Alan W. , Buschanan Charles M. , Pearcy Barry G. , Wood Matthew D.
Published: April 2003

Useful blends of cellulose esters with other higher molecular weight polymers are generally unknown. Two aliphatic polyesters, poly(tetramethylene glutarate) (PTG) and poly(tetramethylene succinate) (PTS), have been thermally compounded with cellulose acetate propionate (CAP) in the range of 10–40 wt % polyester. These blends have been injection molded, and the mechanical properties of the molded bars were compared to bars molded from CAP plasticized with a low molecular weight diester, dioctyl adipate (DOA). The CAP/aliphatic polyester blends have significantly higher tensile strengths, flexural moduli, heat deflection temperatures, and greater hardness values than the corresponding CAP/DOA blends. © 1994 John Wiley & Sons, Inc.
Characterization of model anaerobic adhesive cure using real‐time fourier transform infrared spectroscopy and dielectric spectroscopy
Authors: McGettrick Brendan P. , Vij Jagdish K. , McArdle Ciaran B.
Published: April 2003

A technique has been developed based on Fourier transform infrared spectroscopy (FTIR) in the attenuated total reflectance (ATR) mode, which is suitable for the investigation of the heterogeneous cure of surface‐initiated redox polymerizations in thin and thick bondline situations. The results of the investigations into the surface‐catalyzed and anaerobically promoted cure of some model adhesives using this method are reported. The systems under investigation were designed to exhibit different levels of cure heterogeneity or “cure through volume” (CTV) so that the influence of the bondline thickness and the formulation variables may be assessed. The analysis of the data provides evidence that supports our concept of the heterogeneous cure distribution existing in the form of a cure gradient. This concept of a cure gradient is developed further using dielectric spectroscopy. Here the cure gradient is characterized in terms of the parameters obtained using an empirical equation to fit the dielectric relaxation data. The results obtained using the infrared and dielectric spectroscopic methods are in satisfactory agreement and are shown to be most informative in characterizing and quantifying the CTV performance of the model anaerobic adhesives. © 1994 John Wiley & Sons, Inc.
Crystallization of poly(ethylene terephthalate) (PET) from the oriented mesomorphic form
Authors: Parravicini Lidia , Leone Biagio , Auriemma Finizia , Guerra Gaetano , Petraccone Vittorio , Di Dino Gabriele , Bianchi Riccardo , Vosa Renato
Published: April 2003

Yarns of different inherent viscosities, in the range 0.6–1.1 dL/g, spun in industrial plants, and drawn at room temperature to obtain mesomorphic samples, have been characterized. The evolution from the mesomorphic form toward the triclinic crystalline form has also been studied by combined differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA), and accurate wide angle X‐ray diffraction experiments. The DMA analysis of the mesomorphic samples allows better resolution of the glass transition and crystallization phenomena, which are superimposed in the DSC scans. The degree of molecular orientation in the mesomorphic samples, and the temperature of crystallization from the mesomorphic form (60–80°C), are essentially independent of the polymer molar mass. © 1994 John Wiley & Sons, Inc.
Chain transfer behavior of fractionated commercial mercaptans in emulsion polymerization of styrene
Authors: Harelle Ludovic , Pith Tha , Hu Guo‐Hua , Lambla Morand
Published: April 2003

The chain transfer behavior of fractionated commercial tertiary mercaptans was investigated in batch and semicontinuous emulsion polymerization of styrene over the entire monomer conversion range. Four mercaptans were obtained by fractionation, which contained 9, 11, 12, and 13 carbons, respectively. The effect of the mercaptans was evaluated in terms of the consumption rates of the monomer and the chain transfer agents, the number average degree of polymerization, DPn, and the polydispersity index, I, of the polymer. The batch experiments showed that the chain transfer efficiency decreases with increasing carbon number, which is due primarily to a lower diffusion rate of the chain transfer agent to the reaction sites (growing latex particles) through the aqueous phase. The partitioning ratio of the chain transfer agents between the aqueous phase and the monomer droplets also contributes, to a lesser extent, to the efficiency. The number average degree of polymerization and the polydispersity index are primarily controlled by the ratio of the mercaptan consumption rate over that of the monomer. In order to obtain a polymer with a constant DPn and a narrow I, this ratio should be as close to unity as possible, as is the case for C11. Otherwise, too high a ratio causes a severe increase in DPn at the end of polymerization, and too low a ratio leads in the opposite direction. The semicontinuous experiments confirmed the batch results. © 1994 John Wiley & Sons, Inc.
Phosphorus modification of epoxidized liquid natural rubber to improve flame resistance of vulcanized rubbers
Authors: Derouet D. , Radhakrishnan N. , Brosse J.‐C. , Boccaccio G.
Published: April 2003

The use of phosphorus for improving flame retardancy of natural rubber vulcanizates was attempted by incorporating a modified form of natural rubber. By reacting epoxidized liquid natural rubber (ELNR) with dibutylphosphate it was possible to chemically modify the polymer. On a 25% epoxidized LNR, 5.2–6.8% w/w of phosphorus could be fixed on the polymer backbone. The reaction carried out in bulk and solution resulted in products with different Tg values probably due to the varying crosslink levels in the resultant products. Chemical analysis of the modified polymers prepared by two sets of reactions under identical conditions proved the reproducibility of the reactions in bulk and in solution. Incorporation of the phosphorus‐modified ELNR in a natural rubber formulation decreased the flammability behaviors of the vulcanizate. On the other hand, a decrease of the rate of curing and mechanical properties was observed. The phosphorus addition could also be carried out by mixing ELNR and dibutylphosphate at the time of mixing the compounds and resulted in equally good flame retardance with relatively better processing and mechanical properties. © 1994 John Wiley & Sons, Inc.
Comparative study on rebound resilience and structures of sodium salts of maleic anhydride‐grafted ethylene‐co‐ethyl acrylates with its analogous polymers
Authors: Iwase Yoshiyuki , Hara Hisaaki , Hirasawa Eisaku
Published: April 2003

Sodium salts of ethylene‐co‐ethyl acrylate‐g‐maleic anhydride show high rebound resilience, the same as those of both saponified ethylene‐co‐ethyl acrylates and sodium salts of ethylene‐co‐methacrylic acids at low salt contents. The measurements of thermal and mechanical properties and dynamic viscoelastic behaviors indicate that the sodium salts of ethylene‐co‐ethyl acrylate‐g‐maleic anhydride behave like strong ionic bond cross‐linkages close to covalent bond cross‐linkages in the polymer, differing from the monocarboxylate salts of saponified ethylene‐co‐ethyl acrylate and the sodium salts of ethylene–methacrylic acid. It is concluded that the strong cross‐linking of the dicarboxylate salts of the neutralized ethylene‐co‐ethyl acrylate‐g‐maleic anhydride causes the high rebound resilience. © 1994 John Wiley & Sons, Inc.
Cure kinetics of different molar ratios of 4,4′‐bismaleimidodiphenylmethane and bisphenol A dicyanate
Authors: Hong Jin‐Long , Wang Cherng‐Kuo , Lin Rong‐Hsein
Published: April 2003

Bismaleimide‐triazine (BT) resins are thermosets derived from the addition polymerization of different molar ratios of 4,4′‐bismaleimidodiphenylmethane (BM) and bisphenol A dicyanate (BA). The possible cross‐linking reactions involved in the formation of BT resins are addition polymerization of BM, cyclocrimerization of BA, and heteropolymerization between BM and BA. Fourier‐transform infrared spectroscopy reveals that cyclotrimerization of BA occurs during the cure of a 1 : 2 molar ratio of BM to BA (as 1M2A). No sign of cyclotrimerization is observed for the case of the 1 : 1 molar ratio of BM to BA (as 1M1A). A dynamic differential scanning calorimeter (DSC) is employed to study the cure kinetics. The apparent activation energy evaluated from the Prime method is increased with the content of the BM component in the starting mixture. The different pattern of activation energy with fractional conversion (α) indicates the different chemical nature for the cure reactions of 1M1A and 1M2A. The empirical rate functions thus evaluated are 2.32 × 105 + 5.62 α 105α − 8.61 × 105α2 and 6.07 × 105 + 1.06 × 106α − 1.66 × 106α2s−1 for the cure reactions of 1M1A and 1M2A, respectively. © 1994 John Wiley & Sons, Inc.
Application of ionically crosslinked latex membranes to the separation of ethanol–water mixtures by pervaporation
Authors: Wei Yi , Huang Robert Y. M.
Published: April 2003

Ionically crosslinked latex membrane is prepared by treating the latex membrane containing carboxyl groups with salt solutions. Pervaporation separation with these membranes shows that the ionic crosslinking raises the permeability, with the selectivity being maintained or increased. Ionically crosslinked membranes also have a higher pervaporation separation efficiency than the nontreated membranes. Permeability and selectivity increase with increasing ethanol content in feed. The temperature dependence of permeability can be correlated by the Arrhenius relationship. © 1994 John Wiley & Sons, Inc.
100% solids ultraviolet curing acrylated chlorinated rubber coatings
Authors: Thames Shelby F. , He Z. Alex
Published: April 2003

Acrylated chlorinated rubber (ACR) has been synthesized from masticated natural rubber and characterized with Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance spectroscopy (NMR), and differential scanning calorimetry (DSC). The ACR products have been used as prepolymers in formulations of 100% solids ultraviolet (UV) cured coatings. The UV cured ACR‐based coatings show excellent performance and attractive appearance. Formulation examples and coating performance are reported. © 1994 John Wiley & Sons, Inc.
Enantioface differentiation by chiral polymers containing dimethylaminobornyl moieties
Authors: Liu Jui‐Hsiang
Published: April 2003

Chiral monomers cis,endo‐3‐dimethylamino‐2‐bornyl methacrylate (DABM) and N,N‐dimethyl[cis,endo‐2‐(2‐vinyloxy‐ethoxy)‐3‐bornyl]amine (DVEBA) were synthesized from (+)‐camphor. The homopolymerization of both DABM and DVEBA, and the copolymerization of both chiral monomers with achiral methylmethacrylate (MMA) and styrene (St) were carried out with 2,2‐azobisisobutyronitrile (AIBN) in various organic solvents. Effects of temperature, solvents, reagent molar ratio and reaction time on the polymerizations were studied. Dependences of the feeding concentration and reaction conditions on the specific rotation of the chiral copolymers were investigated. Enantioface differentiation by using the chiral polymers having dimethylaminobornyl moieties synthesized in this investigation were investigated. Effects of temperature and solvent on the asymmetric induction were also studied. © 1994 John Wiley & Sons, Inc.
Fractionated crystallization in polyolefins–nylon 6 blends
Authors: Tang Tao , Huang Baotong
Published: April 2003

The crystallization behavior of polyolefins–nylon 6 polymer blends was studied by differential scanning calorimetry (DSC) measurements. In these blends, the crystallization of the minor component often starts with distinctly deeper supercooling than that of the pure polymer, and proceeds in several separate steps. The origin of this phenomenon was studied and was related to the volume fraction of the dispersed phase and the compatibility between the dispersed phase and the matrix. © 1994 John Wiley & Sons, Inc.
Thermoplastic elastomers from iPP/EPR blends: Crystallization and phase structure development
Authors: D'Orazio L. , Mancarella C. , Martuscelli E. , Sticotti G. , Ghisellini R.
Published: April 2003

The phase morphology and structure of thermoplastic elastomers obtained from isotactic polypropylene (iPP) and ethylene—propylene random copolymer (EPR) blends by means of the dynamic curing of EPR rubbery component carried out during its melt mixing with iPP in a Banbury mixer at 180°C were investigated. Samples obtained by compression molding and by using isothermal crystallization conditions of the iPP phase were analyzed by means of differential scanning calorimetry, of optical, scanning, and transmission electron microscopy, and of wide‐angle and small‐angle X‐ray diffraction. The influence of cooling below the melting point and of EPR molecular structure on the kinetic and thermodynamic parameters related to crystallization process of the iPP phase was also studied. It was found that the process of dynamic curing of the EPR component dramatically affects the development of the phase morphology and structure in the material. As a matter of fact, the blend containing the uncured EPR is characterized by the presence of iPP domains randomly distributed in the EPR rubbery matrix, whereas in the blend containing the cured EPR the iPP phase becomes the continuous phase crystallizing in a structure that resembles a cobweb tending to surround the EPR cured particles; moreover such an iPP cobweb appears to be contituted by row structures of stacked lamellae. It was found that the addition of EPR phase interferes dramatically with the crystallization process of the iPP, thus inducing drastic modification in its intrinsic morphology (size, neatness, regularity of spherulites, inner structure of spherulites, etc.). Such interference was found to be comparatively stronger when the iPP phase crystallizes in presence of cured EPR. The elastic behavior of the thermoplastic elastomer material was accounted for by applying the “leaf spring model” to the morphology and structure of the iPP phase crystallized in presence of cured EPR. © 1994 John Wiley & Sons, Inc.
Studies on preparation and ion‐exchange properties of weakly acidic cation exchange fiber by preirradiation‐induced graft copolymerization with electron beam
Authors: Yun Lu , Zhu Zhang , Hanmin Zeng
Published: April 2003

Weak acidic cational exchange fibers were obtained by means of preirradiation‐induced graft copolymerization of methacrylic acid, acrylic acid, and diglycol acrylate onto polypropylene nonwoven fabric with electron beam. Effects that influence grafting and the exchange adsorptive property of the ion‐exchange fibers obtained toward transition and rare‐earth metal ions have been investigated. © 1994 John Wiley & Sons, Inc.
PBI powder processing to performance parts
Authors: Hughes O. R. , Chen P. N. , Cooper W. M. , DiSano L. P. , Alvarez E. , Andres T. E.
Published: April 2003

A new route (“direct forming”) was developed for forming dense PBI shapes from PBI powder. The new process affords the possibility of automated PBI powder shaping (“cold compaction”) and densification in batches of multiple parts by a “powder‐assisted hot isostatic pressing” process. Direct forming is a more productive alternative to hot compression molding. Two developments enable PBI direct forming: (1) the discovery that PBI powders that are porous and plasticized with moisture can be shaped by compaction at ambient temperatures (cold‐compacted), and (2) a finding that cold‐compacted shapes can be densified in large batches by a powder‐assisted hot isostatic pressing. The porous PBI powder is formed from PBI in solution by a spray‐precipitation process. When plasticized with moisture, this powder is cold‐compactible to PBI shapes with densities up to 94% of that of ultimate density of PBI. These shapes, which have sufficient strength to be handled, are then further consolidated via powder‐assisted hot isostatic pressing to shapes with excellent thermal and mechanical properties and densities of about 99% of the ultimate. © 1994 John Wiley & Sons, Inc.
Composition depth profiles of plasma‐fluorinated poly(ethylene terephthalate) fibers
Authors: McCaulley James A. , Goldberg Harris A.
Published: April 2003

Composition depth profiles of the outer 50 Å of plasma‐fluorinated poly(ethylene terephthalate) fibers were obtained by angle‐dependent X‐ray photoelectron spectroscopy (XPS). The effect of sample geometry on XPS sampling depth and the depth distribution function (DDF) was determined theoretically for cylindrical and hemispherical surfaces. The theoretical DDFs are nonexponential. For cylindrical surfaces, the effect is small, a 22% increase in surface sensitivity. The average XPS sampling depth for smooth, properly oriented fibers is shown to vary, as it does for a planar surface, as the sine of the nominal takeoff angle. The DDF appropriate for cylindrical surfaces was incorporated into a computer program for inversion of angle‐dependent XPS data to obtain composition depth profiles of the fibers. Plasma‐fluorinated PET fibers were used to demonstrate the use of angle‐dependent XPS on fibers. XPS results indicate that most fluorination occurs within the top few “monolayers,” attack is preferentially at the phenyl ring, both CHF and  CF2  moieties are formed, and fluorination causes partial loss of aromaticity. © 1994 John Wiley & Sons, Inc.
Synthesis, characterization, and processing of aromatic copolyesters with different monomer sequences
Authors: Makhija S. , Jaffe M.
Published: April 2003

Two aromatic copoyester compositions were prepared from p‐hydroxybenzoic acid, hydroquinone, and isophthalic acid with compositions 2 : 1 : 1 (HIQ50) and 1 : 1 : 1 (HIQ33). For each of these compositions, one random copolyester and one known sequence copolymer was prepared. The random compositions were prepared by melt condensation, whereas controlled sequence polymers were prepared by low‐temperature solution polymerization. For the 1 : 1 : 1 composition, the controlled sequence polymer had higher crystallinity than that of the random, whereas the 2 : 1 : 1 composition random copolymer had higher crystallinity. The difference in crystallinity is attributed to the sequence distributions in the copolymers. All compositions were thermotropic in nature. © 1994 John Wiley & Sons, Inc.
Synthesis and randomization of well‐defined sequence, wholly aromatic copolyester/esteramides
Authors: Choe Eui‐Won , Borzo Marie
Published: April 2003

Well‐defined sequence, wholly aromatic copolyester/esteramides have been synthesized by an interfacial polycondensation of a preformed triad diacid chloride monomer, di(para‐chlorocarbonylphenyl)isophthalate, with the disodium salt of hydroquinone or of deuterated hydroquinone, or with meta‐phenylene diamine. Carbon‐13 nuclear magnetic resonance (NMR) spectroscopy provided unequivocal evidence for regularly alternating polymer structures, and coupled with statistical methods, for randomization on heating in the case of regularly alternating poly(p‐oxybenzoate‐co‐p‐phenylene isophthalate). Polymers synthesized using standard high‐temperature melt‐polymerization techniques were shown by statistical/carbon‐13 NMR methods to have essentially random structures. Thermal properties of copolymer powders and films were found to vary with monomer sequence distribution as well as with composition. © 1994 John Wiley & Sons, Inc.
Measurement of polar orientation in poled side‐chain NLO polymers using infrared spectroscopy
Authors: Carr P. L. , Davies G. R. , Ward I. M.
Published: April 2003

Infrared spectroscopy has been used to provide an independent estimate of dipole orientation in poled films of a side‐chain polymer based on poly(methyl methacrylate) with an oxynitrostilbene side group attached via an aliphatic spacer. In particular, we used the dichroism of the absorption band assigned to the NO2 symmetric stretching vibration as a measure of the orientation of the nitrostilbene group. This yields 〈P2(cos θ)〉, where θ is the angle between the transition dipole moment and the symmetry axis of the sample. We then used a Langevin‐type model to calculate 〈cos θ〉 from 〈P2(cos θ)〉 and concluded that values of 〈cos θ〉 as high as 0.5 are being achieved. We find, however, that 〈P2(cos θ)〉 obtained by comparison of normal incidence measurements on unpoled and poled films does not agree with 〈P2(cos θ)〉 obtained from tilted‐film measurements on poled films. We propose that this discrepancy arises because the local field in a poled sample affects the polarizability of the molecules. To confirm this, we applied high fields to unpoled films in the infrared spectrometer at room temperature. The results clearly show a large reduction in absorbance with the applied field when the infrared electric field vector has a component perpendicular to the plane of the film. A major error therefore occurs as a consequence of the internal field in poled samples if 〈P2(cos θ)〉 is derived from the tilted film measurements, whereas 〈P2(cos θ)〉 derived from normal incidence measurements is essentially correct. © 1994 John Wiley & Sons, Inc.
Nonlinear optical polymers in advanced photonics
Authors: Jacobson S. , Landi P. , Findakly T. , Stamatoff J. , Yoon H.
Published: April 2003

Development of advanced photonic devices requires extensive integration of several technologies. Electrooptical devices must simultaneously satisfy several materials properties including: high nonlinear optical activity, thermal stability, mechanical strength, and optical transparency. In addition, the device materials must be amenable to fabrication, and must be compatible in a multi‐layered configuration. We have recently developed polymers which meet these complex requirements. Indeed, electrooptical devices have been demonstrated using these polymers. This paper is a comprehensive review of the development of such devices, from design of the molecular architecture to waveguide design and fabrication. The critical issues in each aspect of device development are discussed. © 1994 John Wiley & Sons, Inc.
Mechanical failure in thin‐film nonlinear optical polymers: Structure and processing issues
Authors: McCulloch Iain , Man Hong‐Tai , Song Kigook , Yoon Hyun
Published: April 2003

Stress developed during the spin‐coating process often initiates cracks leading to failure in nonlinear optical devices. The primary intrinsic reasons for this were shown to be a lack of a secondary relaxation process below the glass transition as well as an insufficiently large molecular weight to enhance toughness by chain entanglement, as detected by dielectric measurements and viscoelastic shear moduli, respectively. A detailed systematic synthetic effort was undertaken to increase the chain length through improved free‐radical methods. Results showed that as the molecular weight was raised chain entanglements were observed and film toughness was improved as evidenced by the thicker, crack‐free film attained. As well as thermal stresses, solvent stress cracking was identified as a major source of fabrication defects in the multilayer spin‐coating process. A plasma polymer layer deposited on the film surface was successful as a barrier layer preventing solvent penetration and crack formation. © 1994 John Wiley & Sons, Inc.