bluuebunny/crossref_metadata_2025 huggingface dataset:
Styrene–isoprene block copolymers. II. Hydrogenation and solution properties
Authors: Velichkova R. , Toncheva V. , Antonov C. , Alexandrov V. , Pavlova S. , Dubrovina L. , Gladkova E.
Published: April 2003

Styrene–isoprene block copolymers with a different degree of monomer distribution are hydrogenated with homogeneous catalysts. The products are characterized by means of IR and 1H‐NMR spectroscopy, GPC, viscometry, and light scattering. Hydrogenation proceeds without destruction and selectively for olefinic unsaturation. The hydrogenated copolymers are homogeneous in molecular weights and chain composition. The influence of the copolymer structure on the solution properties in selective solvents is established. In cyclohexane an equilibrium between micelle associates and individual polymer coils, monomolecular micelles, or micelle aggregates are observed, depending on the type of the copolymer. The micellization in base‐lubricating oil leads to micelle fractions with a different degree of association.
Grafting onto wool. XXVIII. Effects of acids on gamma‐radiation induced graft copolymerization of ethylmethacrylate onto wool fiber
Authors: Misra B. N. , Chauhan G. S. , Rawat B. R.
Published: April 2003

Graft copolymerization of ethylmethacrylate (EMA) onto Himachali wool fiber has been investigated in aqueous medium by mutual gamma irradiation from a Co60 source in air and in nitrogen atmosphere. Percentage of grafting has been evaluated as a function of (i) total dose, (ii) concentration of monomer, and (iii) effect of concentration of different acids such as hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, and acetic acid. Maximum percentage of grafting has been obtained in the presence of sulfuric acid. Following reactivity order of different acids towards grafting has been observed: H2SO4 > HCI > HNO3 > HCIO4 > CH3COOH. A plausible mechanism to explain the effect of acids on percentage of grafting of EMA has been suggested.
Phenol–formaldehyde resin curing and bonding in steam‐injection pressing. I. Resin synthesis, characterization, and cure behavior
Authors: Myers George E. , Christiansen Alfred W. , Geimer Robert L. , Follensbee Robert A. , Koutsky James A.
Published: April 2003

Two different phenol–formaldehyde (PF) resole resins are serving as models in a study aimed at establishing the effects of moisture, temperature, pressure, and time on resin cure and bonding during the pressing of wood flakeboard. This phase of the program had two goals: first, to characterize the two resins in terms of their structure and chemistry during synthesis, aging, and cure—using viscosity measurement, gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA); second, to make a preliminary evaluation of the utility of DSC, FTIR, and DMA for measuring the degree of resin cure. The two resins differed significantly in relative amounts of hydroxymethyl groups and methylene linkages (NMR), in molecular weight and its distribution (GPC), and in reaction rate (as measured by viscosity, DSC, FTIR, or DMA). The degree of cure developed during constant heating rate DSC scans was calculated for a series of maximum DSC temperatures from both the loss in hydroxymethyl groups (FTIR) and the decrease in available exothermic heat (DSC). Agreement between the two methods was quite good, considering the inherent difficulties in quantifying infrared data. For comparison, the degree of cure developed during constant heating rate DMA scans was calculated for a series of maximum DMA temperatures from both the increase in storage modulus (DMA) and the decrease in exothermic heat (DSC after rewetting). Samples that apparently achieved complete cure in the DMA still exhibited significant residual cure potential in the DSC. We attribute the lower apparent cure in the DMA to loss of moisture from samples during the DMA scan, with consequent loss in plasticization and molecular mobility.
Surface modification by continuous graft copolymerization. II. Photoinitiated graft copolymerization onto polypropylene film surface
Authors: Zhang Pei Yao , Rånby Bengt
Published: April 2003

A method for photochemically induced graft copolymerization of acrylamide (AM) onto polypropylene (PP) film surface by a continuous presoaking process under nitrogen atmosphere has been developed. After removal of homopolymer formed, ESCA, UV spectroscopy, contact angle, and adhesion measurements confirmed a photografted layer on the surface of the PP film. The results from spectral analysis and surface properties measurements were consistent. The best grafting yield was obtained for 7–10 s irradiation time. Stabilizing additives in the PP film had no evident effect on the photografting. Benzophenone was an efficient photoinitiator for photografting of PP film with AM. An AM concentration of 0.5–1.3M in the presoaking solution was appropriate in the present case. Acetone was the best solvent among the three alifatic ketones tested (acetone, methylethylketone, and methylpropylketone).
Microheterogeneity in PPO/PS blends
Authors: Li S. , Dickinson L. Charles , Chien James C. W.
Published: April 2003

Proton spin magnetization relaxation in the rotating frame is a simple exponential for poly(2,6‐dimethylphenyleneether) (PPO) (23K)/polystyrene (PS) (9K) blends of various compositions; these blends are truly homogeneous at the spin‐diffusion distance scale of a few nanometers. Blends of PPO with high molecular weight PS exhibit nonexponential decays for the PS component but exponential decays for the PPO component, indicating compositional fluctuation for PS. In some blends, the relaxations are nonexponential for both components. Three factors have been identified to promote microheterogeneity of nanometer dimensions: high polymer molecular weight, increase of temperature, and preparation of blend using solvent that induces crystallization of PPO such as toluene.
Cure behavior of an epoxy–novolac molding compound
Authors: Hsieh T. H. , Su A. C.
Published: April 2003

The isothermal cure of an epoxy–novolac molding compound was studied by means of differential scanning calorimetry (DSC). The glass transition temperature (Tg) of the molding compound increased in an approximately linear manner with conversion (α) during the major part of the cure process. Predictions of an empirical kinetic scheme (established earlier from dynamic DSC results) compared favorably with the present isothermal results in the absence of vitrification. In combination with the gel point conversion (αgel) determined via dynamic rheological analysis and gravimetric measurements, our DSC results indicated that gelation bears no apparent effect on the rate of cure whereas vitrification retards the cure reaction. Based on the measured αgel, the approximate Tg−α relationship, and the thermokinetic results, the time–temperature–transformation diagram of this molding compound was constructed and discussed.
Polymerization of N‐vinylcarbazole by gaseous initiators
Authors: Bhadani Suraj N. , Gupta Sumanta K. Sen , Sinha Arvind K.
Published: April 2003

The polymerization of N‐vinylcarbazole initiated with NO2 and SO2 in dichloroethane has been studied. The kinetics of polymerization were followed gravimetrically. The Polymerization is fast with NO2 but a relatively slow rate was obtained with SO2. The polymerization with these gases appears to be initiated by a charge transfer mechanism.
Effects of spinning conditions on morphology and properties of polyethylene terephthalate fibers spun at high speeds
Authors: Chen Gao‐Yuan , Cuculo John A. , Tucker Paul A.
Published: April 2003

Fiber spinning of polyethylene terephthalate (PET) was studied at take‐up speeds ranging from 2000 m/min to 7000 m/min under various spinning conditions. Effects of changes in process variables on the molecular orientation, crystallinity, and properties of as‐spun PET fibers are reported. Conventional cross‐flow quench in high‐speed spinning yields fibers with undesirable crimp and asymmetric structure with respect to the fiber axis. Radial‐flow quench eliminates these problems. Changes in other spinning conditions, such as extrusion temperature, throughput or take‐up denier, and molecular weight, may also affect the development of PET fiber structure in the high‐speed threadline.
Dynamic mechanical properties of polypropylene–polyamide blends: Effect of compatibilization
Authors: Liang Zhizhong , Williams H. Leverne
Published: April 2003

The influence of compatibilization on the dynamic mechanical properties of polypropylene (PP) binary blends with polyamide‐11 (PA) has been investigated. In the blends an acrylic acid functionized PP was used as a blend component and compared with nonfunctionized PP over the who concentration range. The results demonstrate that the use of the functionized PP instead of the unmodified one produced blends with different dynamic mechanical properties due to adhesion enhancement between the two phases. The storage moduli E′ of the compatibilized blends vary nearly linearly as a function of composition over a broad temperature region, whereas those of the noncompatibilized ones deviate greatly from linearity, specially at about 50/50 ratio, at which a minimum exists at about room temperature. While the dynamic testing gives no evidence for the variation in the glassy transition temperatures (peak maxima) of the components (PP and PA) in the two types of blends, both the loss modulus (E″) and the loss factor (tan δ) data indicate that the compatibilized blends differ from the noncompatibilized ones mainly in the glassy transition (βrelaxation) process of the PA phase, suggesting that the compatibilization of the blends seems to influence the PA phase more than the PP phase included. But, for the β‐relaxation behavior of the PA in the modified blends, the tan δ spectrum shows a more complex pattern than does the E″. These results are discussed in terms of the morphological texture of the blends and possible chemical or physical interactions between the two consituent polymers.
Catalytic grafting: A new technique for polymer–fiber composites I. Polyethylene–asbestos composites
Authors: Wang Qi , Kaliaguine Serge , Ait‐Kadi Abdellatif
Published: April 2003

In this work we present a new technique to prepare polyolefin‐fiber composites. This technique is based on chemical anchoring of a catalyst on reinforcing agents containing OH groups on their surface and then conducting an olefin polymerization on the supported catalyst. This technique offers the possibility to approach the challenging problems encountered in polymer composites, namely, the reinforcement‐matrix adhesion, the dispersion, and the wetting of the reinforcement by the resin. As a first part of a systematic research, we report on the procedure of fixation of titanium tetrachloride on the surface of asbestos fibers and the Ziegler‐Natta polymerization of ethylene on the surface‐modified fibers. The procedure as well as the structure and properties of the composite were investigated by means of FTIR, atomic absorption, SEM, solvent extraction, and tensile testing. The experimental results show that the Ziegler‐Natta catalyst can be efficiently anchored on the surface of the fibers to conduct successful polymerization and to “synthesize” a new class of polymer composites.
Reactions of glycerol with poly(ethylene ether carbonate) polyols
Authors: Harris Robert F. , Lopez Karen M.
Published: April 2003

Poly(ethylene ether carbonate) polyols can be modified by chemical reactions with polyglycol modifiers under conditions of elevated temperatures and reduced pressures. The modifier becomes chemically incorporated into the modified polyol and is used to control properties such as moisture sensitivity, CO2 content, Tg, density, etc. in the resultant polyol. However, glycerol cannot be used as a modifier for poly(ethylene ether carbonate) polyols under the same conditions since it reacts with poly(ethylene ether carbonate) polyols by a transesterification reaction sequence to form glyceryl carbonate. As the temperature is increased, the glyceryl carbonate decomposes to yield glycidol and carbon dioxide. These reactions are conveniently followed by 13C‐NMR. The preparation of glyceryl carbonate by this process has not been previously reported.
Studies in optical properties and optical radiation hardness of polyorganosiloxanes
Authors: Harmon J. P. , Jhaveri T. , Gaynor J. , Walker J. K. , Chen Z.
Published: April 2003

A variety of polyorganosiloxanes containing dimethyl, diphenyl, and methylphenyl substituents were studied to determine transparency and optical radiation hardness. Siloxanes show superior optical radiation hardness when compared to optical thermoplastics such as PMMA. Transparency is diminished in polymers containing diphenyl units. This is attributed to the inability to remove traces of the crystalline monomer. Methylphenyl polymers are highly transparent. The maximum attainable refractive index in transparent systems is 1.53.
Studies on the radiation‐induced graft copolymerization of mixtures of n‐butyl acrylate and 2‐hydroxyethyl methacrylate on polyurethane. I. Synthesis and characterization
Authors: Sreenivasan K. , Rao K. V. C.
Published: April 2003

Modification of polyurethane, by grafting two types of monomers, a hydrophilic and hydrophobic, with an aim to enrich the surface with both hydrophobic and hydrophilic moieties, is attempted. Grafting of 2‐hydroxyethyl methacrylate and n‐butyl acrylate from a mixture of these two onto polyurethane by γ‐irradiation and subsequent characterization of the graft copolymer by infrared spectroscopic method, mechanical characterization, contact angle, and scanning electron microscopy is detailed.
Influence of molecular weight on the thermal and mechanical properties of polyurethane elastomers based on 4,4′‐diisocyanato dicyclohexylmethane
Authors: Hespe Hans F. , Zembrod Alfred , Cama Farhad J. , Lantman Christopher W. , Seneker Stephen D.
Published: April 2003

Two series of segmented polyurethane elastomers based on 4,4′‐diisocyanato dicyclohexylmethane were investigated with respect to their thermal properties and deformation behavior. We used a crystallizable soft segment, 1,4‐poly(tetramethylene glycol), for one series and a noncrystallizable soft segment, 1,2‐poly(propylene glycol), for the other. Both systems exhibited mechanical self‐reinforcement that depended strongly on the deformation rate. We propose a mechanism for the observed stress/strain behavior in terms of two competing processes: (1) the buildup of orientation caused by deformation and (2) the loss of orientation caused by plastic slippage and segmental relaxation during deformation. The kinetics of these processes depend stronly on the deformation rate and overall molecular weight.
Synthesis of macromolecular coupling agents and binders
Authors: Crespy A. , Caze C. , Loucheux C.
Published: April 2003

Sizes of glass fibers used in composite materials include binders and coupling agents. Usually these types of compounds have a low molecular weight and present two identical reactive groups for binders and two different functions (namely, organic and inorganic groups) for the coupling agents. The aim of this paper was to describe the synthesis of macromolecular binders and coupling agents in order to perform the interphase region. These products appear as difunctional or polyfunctional compounds. Difunctional compounds were obtained by reaction between a telechelic polymer (prepared by anionic polymerization) and alkoxysilane or epoxy groups. Polyfunctional compounds were performed by hydrosilylation reactions between a polysiloxane containing hydrogenosilane functions and vinylsilane, and/or 1‐allyloxy‐2,3 epoxypropane.
Effect of latex concentration on epoxidation of natural rubber (NR) latex
Authors: Vernekar S. P. , Sabne M. B. , Patil S. D. , Patil A. S. , Idage S. B. , Avadhani C. V. , Sivaram S.
Published: April 2003

Effect of latex concentration on the extent of epoxidation and physical properties of epoxidized natural rubber (ENR) was evaluated as a function of latex concentration in the range of 20–60% by weight. The epoxidation rate increased with increasing latex concentration. Physical properties and sequence distribution of an epoxy group of ENR with 30 mol % epoxy content was invariant with the latex concentration employed for epoxidation.
Coconut husk lignin. II. Characterization by infrared and nuclear magnetic resonance spectroscopy
Authors: Vázquez‐Torres H. , Canché‐Escamilla G. , Cruz‐Ramos C. A.
Published: April 2003

Results of the characterization of coconut husk lignin by infrared (IR) and proton nuclear magnetic resonance (H‐NMR) spectroscopy are presented. Lignin was extracted with both alkaline and organosolv liquors. The IR spectra of dioxane lignin were very similar to those reported for hardwood lignins. Furthermore, these results combined with those obtained from the H‐NMR studies suggest that coconut husk lignin can be classified into the Lm‐type lignins. These lignins are characteristic of the monocotyledon class, of which the coconut palm is a member. The H‐NMR studies showed that anthraquinone significantly inhibited the occurrence of lignin condensation during the alkaline extraction with sodium hydroxide solutions. This inhibition was more intense in the lignin extracted at 150°C than in that extracted at 100°C.
Synthesis and thermal stability, dielectric, and conductivity characteristics of some carbazole‐bearing pendant and backbone sulfones
Authors: Mitra Pradyot , Biswas Mukul
Published: April 2003

A group of poly(N‐vinylcarbazole) pendant polysulfones has been prepared by reacting it with benzene, toluene, p‐chlorobenzene‐ and p‐nitrobenzenesulfonyl chloride and N‐methyl carbazole, 3,6‐disulfonyl chloride by the Friedel Crafts reaction. Carbazole‐based backbone polysulfones have also been prepared by the reaction of N‐methyl carbazole, 3,6‐disulfonyl chloride and biphenyl, naphthalene, anthracene, and carbazole in presence of anhydrous aluminum chloride. The various sulfone polymers, thus prepared, have been structurally characterized by elemental analysis and IR spectroscopy. Detailed analyses of thermal stability, dielectric, and conductivity characteristics have revealed certain significant differences between these two types of sulfone polymers.
Properties and swelling characteristics of cross‐linked poly(vinyl alcohol)/chitosan blend membrane
Authors: Kim Jin Hong , Kim Ju Young , Lee Young Moo , Kim Kea Yong
Published: April 2003

Blend membrane consisting of poly(vinyl alcohol) (PVA) and chitosan was prepared from a solvent‐casting technique and characterized for their intermolecular interactions using infrared and X‐ray diffraction methods. Cross‐linking the blend with glutaraldehyde produces a membrane with lower crystallinity and a smaller swelling degree, but having improved thermostability and mechanical properties. The present blend membrane shows a pH‐dependent swelling characteristic and will be discussed in detail. © 1992 John Wiley & Sons, Inc.
Effect of acid–base interaction on the sorption characteristics of liquids in poly(vinylidene fluoride)
Authors: Myeong Wan‐Jae , Ihm Son‐Ki
Published: April 2003

The sorption characteristics of various liquids in poly(vinylidene fluoride) (PVDF) were investigated in relation to the Lewis acid–base interaction between the liquids and the polymer. The sorption amount of various liquids and the sorption selectivity of binary mixtures in PVDF were measured and their characteristics were found to be significantly affected by acid–base interaction. The acid–base interaction was evaluated from the Drago constants of PVDF, which were obtained by extending the Fowkes' method observing the shift of stretching frequency of the carbonyl bond of ethylacetate sorbed in PVDF. The partial molar enthalpy change of mixing at infinite dilution was estimated using the Drago constants of PVDF and used as a parameter explaining the sorption characteristics of liquids in PVDF. © 1992 John Wiley & Sons, Inc.
Characterization of cellulose–chitosan blend films
Authors: Hasegawa Makoto , Isogai Akira , Onabe Fumihiko , Usuda Makoto , Atalla Rajai H.
Published: April 2003

Interactions between cellulose and chitosan molecules in cellulose–chitosan blend films, prepared using trifluoroacetic acid as a cosolvent for the two polysaccharides, were studied by X‐ray diffraction and Raman analyses and by measurements of mechanical properties of the blend films. Crystallinity of cellulose in the blend films decreased with an increase in chitosan content. The blend films had tensile strengths of 45–100 MPa and Young's moduli of 2–7.5 GPa in dry states. These values had the maximum around 30% chitosan content in the blend films. These results suggested the presence of interactions between cellulose, chitosan, and water molecules in the films. However, Raman analysis suggested that cellulose and chitosan molecules in the blend films seemed to have the same secondary structures as those in 100% cellulose and 100% chitosan films, respectively. Thus, these results indicate the presence of interactions in the interfacial region between small domains of cellulose and chitosan. The presence of chitosan molecules may lead to decrease in the domain size of cellulose, and to increase in the interfacial region between cellulose and chitosan domains.
Synthesis of substituted polymethylenes from acenaphthylene by radical polymerization and copolymerization
Authors: Otsu Takayuki , Matsumoto Akikazu , Nakamura Keisuke
Published: April 2003

Radical polymerization of acenaphthylene (Ace) as a 1,2‐disubstituted ethylene was investigated. It was found that the polymerization rate (Rp) was expressed as follows: Rp = k[Ace]1.0[AIBN]0.68, and that the overall activation energy was 113 kJ/mol for polymerization with 2,2'‐azobisisobutyronitrile (AIBN) in benzene at 50–70°C. Poly(Ace) obtained was characterized by NMR spectroscopy and GPC. Some substituted copolymethylenes were also prepared by radical copolymerization of Ace with other 1,2‐disubstituted ethylenes, that is, maleic anhydride, diisopropyl fumarate, and N‐cyclohexylmaleimide. The monomer reactivity ratios were determined from comonomer–copolymer composition curves.
N‐methylation of wholly aromatic polyamides for size‐exclusion chromatography
Authors: Mourey T. H. , Guistina R. A. , Bryan T. G. , Thornbury R. F. , Blevins R. , Perry R. J. , Turner S. R.
Published: April 2003

Wholly aromatic polyamides, including poly(1,4‐phenyleneisophthalamide) and poly(1,4‐phenyleneterephthalamide) are N‐methylated to render them soluble in N,N‐dimethylformamide, a common size‐exclusion chromatography eluent. The procedure N‐methylates 50–55% of the total amide linkages in these two examples, permitting reproducible measurement of their absolute molecular weight distributions using differential viscometry detection. There is no observable degradation in molecular weight resulting from the N‐methylation, provided the excess methylating reagent is destroyed shortly after completion of the derivatization by quenching with potassium acetate. The validity of the molecular weight data obtained by the method is confirmed by light‐scattering measurements on derivatized polymer and by comparison to the molecular weight of underivatized polymer that can be approximated from the intrinsic viscosity in concentrated sulfuric acid. The method is applicable to a variety of wholly aromatic polyamide structures. Examples are given.
Preparation of monodisperse carbonaceous particles with micro‐, meso‐, and macroporous structures
Authors: Daer Khaled M. , Levendis Yiannis A.
Published: April 2003

Spherical, highly porous synthetic carbon particles have been prepared from formulations of either poly(furfuryl alcohol) or poly(vinyl acetate) mixed with a solvent and poreforming agents. Production was carried out by atomizing these mixtures inside a thermal reactor and drying the resulting aerosol. The size of the collected polymeric particles was controlled by preadjusting the parameters of the atomization process. Fine‐tuning of the process resulted in the generation of batches of monosized particles. Subsequent thermal degradation at 600°C resulted in porous chars with controlled pore‐size distributions. Several distinct pore structures were superimposed using this technique with pore widths spanning the region from a few nanometers to a few tens of micrometers. Spherical and equal‐sized macropores were also generated with a special technique described herein. All chars were produced in batches of spherical and monodisperse particles, with diameters in the range of 20–150 μm. BET surface areas were measured to vary from 1 m2/g to over 150 m2/g prior to any oxidative treatment. Porosities varied from 10 to 80%.
Thermal aging of plasticized PVC. II. Effect of plasticizer loss on electrical and mechanical properties
Authors: Audouin L. , Dalle B. , Metzger G. , Verdu J.
Published: April 2003

The change of mechanical properties was followed during thermal aging at 85, 95, 105, and 120°C of the 10 PVC–didecylphthalate extrudates studied in the first part of this paper, but also of four new samples differing only by the plasticizer concentration. For these latter samples, the change of dielectric properties was also studied. It appears that the dielectric properties are essentially the function of the plasticizer concentration whatever is the initial concentration or aging conditions. In contrast, the mechanical properties vary in a more complex way and cannot be predicted by a simple physical model. It is suggested that, among other factors, the depth distribution of plasticizer can play an important role.
Thermotropic liquid crystalline behaviors of ethylcellulose
Authors: Jianan Chen , Yifang Huang , Jinyue Yuan , Shaoqiong Yan , Hua Ye
Published: April 2003

The thermotropic liquid crystalline behaviors of ethylcellullose (EC) were investigated by DSC, polarizing microscope with hot stage, and capillary rheometer. It was found that only those EC that have the ethoxyl content over 45% can exhibit the thermotropic liquid crystalline behaviors: the DSC trace showed the transition from mesophase to isotropic phase, the texture appeared under the crossed polarizer, and the rheological flow curves exhibited two yield points.
Graft copolymerization of methacrylates onto wool fibers
Authors: Liouni Maria , Touloupis Costas , Hadjichristidis Nikos , Karvounis Sotiris , Varriano‐Marston Elizabeth
Published: April 2003

Grafting of butyl (BuMA), decyl (DeMA), and octadecyl methacrylate (ODeMA) onto reduced wool was carried out by using K2S2O8 or K2S2O8–LiBr redox system as initiator. The influence of the monomer and monomer concentration, temperature, and duration of the reaction on the percentage of grafting was studied. Evidence of grafting was provided by scanning electron microscopy, size exclusion chromatography, and infrared spectroscopy.
Some aspects of stabilization and degradation of nigerian natural rubber (II): The environmental degradation of DBHBT‐modified unprocessed, unvulcanized nigerian natural rubber
Authors: Ebi G. C. , Kolawole E. G.
Published: April 2003

3,5‐Di‐tert‐butyl‐4‐hydroxybenzyl thioglycollate (DBHBT) was bound to the natural rubber (Hevea Brasilenisis) latex using 4,4'‐azobiscyanovaleric (AZBN) acid‐ferrous sulfate redox system. The degradation of various dilutions of the master batch as cast films under environmental influence has been investigated using spectroscopic method. Latex‐bound DBHBT protects natural rubber latex against environmental degradation with an optimum concentration around 50%. The formation of C0 groups by some pathways independent of OH groups and allylic hydrogen atoms has been suggested in the natural weathering of DBHBT‐modified and unprocessed natural rubber.
Synthesis and photoelectrical properties of poly[2,6‐(p‐phenoxy)‐4‐phenylquinoline]
Authors: Kim Kyeong‐Ah , Park Soo Young , Kim Yoo Joong , Kim Nakjoong , Hong Sung Il , Sasabe Hiroyuki
Published: April 2003

New heteroaromatic polymer containing quinoline unit in the main chain, poly[2,6‐(p‐phenoxy)‐4‐phenyl quinoline] (PQ), was synthesized by the acid‐catalyzed self‐condensation reaction [Friedländer quinoline synthesis] of 4‐amino‐4′‐acetyl‐3‐benzoyldiphenyl ether, and its chemical structure was characterized by IR and NMR spectra and also by elemental analysis. The PQ was soluble in common organic solvents such as chloroform or tetrahydrofuran; thus a strong coherent film of this polymer could be easily prepared from the solution by the casting or spin‐coating technique. Attributing to the wholly aromatic chemical structure, PQ appeared an extremely high thermal stability as to show no weight loss up to 550°C both in air and nitrogen atmosphere. From the UV–VIS absorption spectra, we found that PQ had a strong tendency to form the charge transfer (CT) complex with electron acceptors such as 2,4,7‐trinitrofluorenone (TNF). The CT complex film of PQ–TNF showed a good photoconductivity even under the ambient room illumination and was utilized for the fabrication of photovoltaic device whose conversion efficiency was around 10−2%.
Plasma polymerization of octafluorocyclobutane and hydrophobic microporous composite membranes for membrane distillation
Authors: Kong Ying , Lin Xiao , Wu Yonglie , Chen Jie , Xu Jiping
Published: April 2003

In this paper, hydrophilic microporous cellulose nitrate membranes have been surface‐modified by plasma polymerization of octafluorocyclobutane (OFCB). The microporous composite membranes with a hydrophilic layer sandwiched between two hydrophobic layers have been obtained. The obtained composite membranes have been used in a membrane distillation (MD) process and have exhibited good performance. The effects of polymerization conditions, such as glow‐discharge power and deposition time, on the structures and MD performances of the obtained composite membranes have been investigated by SEM, X‐ray microscopical analysis, and XPS. The polymerization conditions should be as mild as possible in order to prepare the hydrophobic composite membrane with good MD performance. The typical MD behaviors of the obtained hydrophobic composite membranes are in agreement with that of hydrophobic membranes directly prepared from hydrophobic polymeric materials, like PVDF, PTFE, or PP.
Polyimides derived from a methylene‐bridged dianhydride
Authors: Boston Harold G. , St. Clair Anne K. , Pratt J. Richard
Published: April 2003

A series of linear aromatic polyimide films that are based on a novel methylene‐bridged dianhydride, 3,3′‐bis(3,4‐dicarboxyphenoxy) diphenylmethane dianhydride, have been synthesized and characterized. High molecular weight polyamic acids were prepared by combining this dianhydride with numerous aromatic diamines. The effects of thermal and chemical imidization of the polyamic acids are discussed as they relate to the dielectric constant, optical transparency, and solubility of the resulting polyimide films. The objective of this work was to obtain low dielectric, optically transparent, and soluble polyimides that can be easily processed as coatings or composite matrices for advanced aerospace and electronics applications.
Modeling the effects of micromixing and start‐up procedures on bulk copolymerization and copolymer in a tubular reactor
Authors: Atiqullah M. , Hassan M. M. , Beg S. A.
Published: April 2003

The combined effects of micromixing and start‐up procedures on free radical, bulk copolymerization of styrene and acrylonitrile in an isothermal, premixed‐feed tubular reactor have been theoretically analyzed. An axial dispersion model, which takes into account the entire range of backmixing, froms the basis of this analysis. Model predictions show that the overall conversion decreases with the increase of initial styrene content in the reactor, and is not affected by the degree of micromixing. However, for the nonazeotropic feed, the copolymer composition distribution becomes wider with the increase of initial acrylonitrile content in the reactor. For the azeotropic feed, broadening occurs with the decrease of initial acrylonitrile content in the reactor. Average copolymer composition is not affected either by micromixing or start‐up procedure.
X‐ray investigations on annealed fibers of poly(p‐phenylene‐1,3,4‐oxadiazole)
Authors: Hofmann D. , Leonhardt R. , Weigel P.
Published: April 2003

The influence of annealing on the supermolecular structure of commercial, thermostable fibers, spun from solutions of poly(p‐phenylene‐1,3,4‐oxadiazole) (POD) in H2SO4, is examined. The crystalline α‐modification of thermally treated POD fibers has an orthorhombic unit–cell probably of space group P212121. The symmetry of the single POD chain in these crystallites is 21. The unit–cell dimensions are a = 1.235 nm, b = 0.655 nm, c = 1.40···1.47 nm, where c depends on the annealing temperature Ta. The unit cell contains 4 chains of two monomers each. Annealing up to Ta of about 755 K causes increases in crystallite size, crystalline orientation, and linear degree of order, combined with an improved axial Young's modulus E. Thermal degradation at higher temperatures leads to the breaking of tie molecules in general, while UV‐radiation selectively damages tie molecules that are not taut.
Influence of an electric field on polar‐group orientation and adhesion at poly(ethylene terephthalate) surfaces
Authors: Lavielle L. , Nakajima K. , Schultz J.
Published: April 2003

Application of a high continuous electrical field accelerates the orientation kinetics of polar groups at a polymer–water interface and so improves the surface polarity. This is preliminary to adhesion establishment on a polar substrate. Adhesion of PET and gelatin performed under an electric field leads to an increase of the interfacial adhesion properties, due to simultaneous effects of the electric field at the interface. Polar‐group orientation at a polymer surface and electrical aspects of adhesion are therefore self‐consistent.
Graft copolymerization of polyfurfuryl alcohol and cellulose
Authors: Nguyen Charles , Zavarin Eugene
Published: April 2003

Viscosity of polyfurfuryl alcohol (PFA) and addition of hydroquinone exert a strong positive effect on grafting polyfurfuryl alcohol to cellulose fiber with H2O2/Fe2+ oxidant in an aqueous slurry at pH 2. Composition of the atmosphere and the nature of acids used to adjust pH does not influence the reaction, with the exception of phosphoric acid, which negatively influences polymer loading. Conducting the reaction in nonaqueous media inhibits grafting. K2S2O8, Ce(SO4)2, and K2Cr2O7 perform as well as H2O2/Fe2+, whereas H2O2/thiourea dioxide, H2O2/thiourea, NH4VO3, KMnO4, and KNO3 give inferior polymer loads; Mn3+/acetylacetonate and azobisisobutyronitrile are ineffective. A small improvement in polymer loading is obtained by gradual addition of the oxidant to the reaction slurry.
Glucose‐responsive insulin release from poly(vinyl alcohol)‐blended polyacrylamide membranes containing glucose oxidase
Authors: Chandy Thomas , Sharma Chandra P.
Published: April 2003

Glucose‐sensitive membranes that can increase their permeability in the presence of glucose have been developed. Membranes are fabricated by free‐radical polymerization of acrylamide and poly(vinyl alcohol) blends, containing glucose oxidase (GOD). The polymers are hydrogels, with water content in the range of 85–95%, depending on the pH or glucose concentration. The gluconic acid produced by an enzymatic reaction between glucose oxidase and glucose induces a decrease in pH value of the medium. This may causes the protonation of the amino groups in the membrane, resulting in an increase in water content of the polyamine membrane or which changes the solubility of insulin and the diffusional driving force. The in vitro retention of the enzyme activity by the membrane is also reported. It appears that the problem of membrane rupture may be alleviated by the blending of polyacrylamide (AA) with poly(vinyl alcohol) (PVA), since they have demonstrated an improved wet strength, without altering their insulin‐transport properties. This preliminary report proposes the possibility of developing glucose‐sensitive membranes for controlled delivery of insulin and also benefits from ongoing research on biosensors.
Crystal orientation distributions in injection‐molded polypropylene compounds
Authors: Chen Z. , Finet M. C. , Liddell K. , Thompson D. P. , White J. R.
Published: April 2003

The crystal orientation distribution in injection‐molded bars made from several polypropylene compounds has been investigated using pole figure analysis. The fillers used were glass fibers, chalk, and talc, and some compounds contained one filler and others contained glass fibers plus one or both of the others. All compounds showed strong orientation in the skin with the b‐axis of the monoclinic crystals lying preferentially normal to the flow direction and in many cases parallel to the normal to the bar face. This normal direction orientation was very strong in compounds containing talc and is probably caused by crystals forming with their (010) planes on the talc platelet faces, which align themselves parallel to the mold face. Strong orientation persists into the interior of the moldings containing talc, whereas in the other compounds, the orientation at intermediate depths is much less pronounced than in the skin. © 1992 John Wiley & Sons, Inc.
Structural characteristics of wool fiber modified with itaconic anhydride
Authors: Tsukada Masuhiro , Goto Yohko , Romanó; Maria , Ishikawa Hiroshi , Shiozaki Hideki
Published: April 2003

The physicochemical properties of wool fibers chemically modified with itaconic anhydride in dimethylformamide were analyzed by DSC, TMA, and TGA and on the basis of measurements of the tensile characteristics. The acyl content in wool fiber increased even at the comparatively low reaction temperature (65°C) compared with that in silk fiber; this fact was due to the larger number of reactive sites in the wool than in silk such as basic amino acid residues. On the basis of DSC, TMA, and TGA analyses, the high thermostability of the modified wool fiber was evident. The molecular orientation, evaluated from the birefringence measurement, decreased slightly after the modification; however, tensile properties and surface characteristics of the wool fiber were not damaged. © 1992 John Wiley & Sons, Inc.
Plasticizing polyesters of dimer acid and butane diol
Authors: Bajpai U. D. N. , Singh Kavita , Nivedita
Published: April 2003

The polyesterification reaction between dimer acid and 1,4‐Butane diol under different experimental conditions has been studied to obtain the optimum conditions for synthesizing poly(1,4‐butanediol)dimerate plasticizers. The effect of varying molar ratio and catalyst concentration on acid number, intrinsic viscosity, and molecular weight have been investigated. It has been found that p‐toluene sulfonic acid is an effective catalyst for the polyesterification reaction. © 1992 John Wiley & Sons, Inc.
Pore formation, permeability, and permselectivity in porogen derived membranes
Authors: Eyal A. M. , Hajdu K. , Hazan B. , Edelstein D.
Published: April 2003

Porogen derived membranes, formed on decomposition of porogen molecules homogeneously dispersed in premembranes, were divided into two groups according to permeability and permeation mechanism. The more open membranes were formed when premembranes were cast on nonwoven polyester cloth support, or when decomposition products were extracted by solvent. The molecular cut off found for these membranes was at about 1000 Daltons and permeability was mainly determined by permeants' diffusivity and concentration. Permeability through the denser membrane was mainly determined by the permeants' partial vapor pressure, leading to high permselectivities. These denser membranes allowed relatively high osmotic water permeation while practically blocking permeation of solutes, such as salt, in the opposite direction. These membranes were thus also suitable for concentration of aqueous solutions by water removal into concentrated electrolyte solutions. © John Wiley & Sons, Inc.
Synthesis of block copolymers by the combination of chain transfer polymerization and initer process
Authors: Demircioglu Perihan , Acar Metin H. , Yagci Yusuf
Published: April 2003

Radical polymerizations of styrene (St) and methyl methacrylate (MMA) were carried out in the presence of tri phenylmethyl mercaptan (TPMM) as a chain transfer agent to give trityl (triphenylmethyl) terminated polymers. Transfer constants were found to be 17.8 and 0.71 for St and MMA, respectively. Trityl terminated polymers served as thermal “INITERS” for polymerization of vinyl monomers which proceeded via a quasi‐living radical mechanism. This procedure makes it possible to prepare block copolymers. © John Wiley & Sons, Inc.
Blends of poly[3,3‐bis(chloromethyl)oxetane] with poly(vinyl acetate). I. Thermal and mechanical properties
Authors: Weilian Liu , Qipeng Guo , Zhiliu Feng
Published: April 2003

Blends of poly[3,3‐bis(chloromethyl)oxetane] (Penton) with poly(vinyl acetate) were prepared. Compatibility, morphology, thermal behavior, and mechanical properties of blends with various compositions were studied using differential scanning calorimetry (DSC), dynamic mechanical measurements (DMA), tensile tests, and scanning electron microscopy (SEM). DMA study showed that the blends have two glass transition temperatures (Tg). The Tg of the PVAc rich phase shifts significantly to lower temperatures with increasing Penton content, suggesting that a considerable amount of Penton dissolves in the PVAc rich phase, but that the Penton rich phase contains little PVAc. The Penton/PVAc blends are partially compatible. DSC results suggest that PVAc can act as a β‐nucleator for Penton in the blend. Marked negative deviations from simple additivity were observed for the tensile strength at break over the entire composition range. The Young's modulus curve appeared to be S‐shaped, implying that the blends are heterogeneous and have a two‐phase structure. This was confirmed by SEM observations. © 1992 John Wiley & Sons, Inc.
Model for attachment of active species onto gelular polymer bead
Authors: Jo Young‐Do , Ihm Son‐Ki
Published: April 2003

Equations for the equilibrium between the stresses and the degree of swelling, and also for the mass balance of substrate and functional groups, are proposed in order to analyze the attachment of active species onto gelular polymer bead. The asymptotic expansion technique was used to solve these equations when the relaxation rate of polymer in solvent is higher than the reaction rate and the reaction rate is much faster than the diffusion rate. It was shown that the interaction between solvent and polymer with attachment can be explained from the simulation. The equations proposed can be utilized to better understand the control of active species distributions in the polymer bead. © 1992 John Wiley & Sons, Inc.
Tris(3‐aminophenyl)Phosphine oxide‐based nadimide resins. II
Authors: Mathur Anju , Varma I. K.
Published: April 2003

A series of phosphorus‐containing nadimide end‐capped resins having different backbones was prepared by reacting endo‐5‐norbornene‐2‐3‐dicarboxylic acid anhydride (nadic anhydride), pyromellitic dianhydride (PMDA)/3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6F) and tris(3‐aminophenyl)phosphine oxide (TAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, FTIR, and 1H‐NMR. Thermogravimetric studies revealed a multistep decomposition reaction for uncured resins. Residual weight at 800°C in nitrogen was found to be 50–60%. Resins cured at 300°C for 1 h in air atmosphere were stable up to 440 ± 20°C and decomposed in a single step above this temperature. The char yields of cured resins were in the range 63–71.5%. © 1992 John Wiley & Sons, Inc.
Comparative rheological studies on jute‐fiber‐ and glass‐fiber‐filled polypropylene composite melts
Authors: Basu D. , Banerjee A. N. , Misra A.
Published: April 2003

An experimental study of the melt rheological properties of composites of isotactic poly‐propylene (IPP) filled with chopped jute‐fibers (JF) and glass‐fiber (GF) is reported. Fiber concentration is 5–20 wt %. Variation of shear stress with shear rate at constant temperature indicates increase in shear stress with shear rate and fiber loading. Shear stress values for IPP/GF melts are higher at the same shear rate and temperature. Variation of melt viscosity and melt elasticity with fiber concentration and shear stress or shear rate are also illustrated. Melt viscosity increases with fiber loading, while melt elasticity parameters such as dieswell and first normal stress difference decrease for both systems. For IPP/GF composite melts the viscosity values are higher, the die‐swell and first normal stress difference values are lower compared to IPP/JF composites melts. Processing temperature of the filled IPP composites increase with respect to the nonfilled polymer, being a little higher in case of IPP/GF composites. © 1992 John Wiley & Sons, Inc.
Bending and torsional fatigue of nylon 66 monofilaments
Authors: Toney Mary , Schwartz Peter
Published: April 2003

Using newly developed test equipment, the fatigue behavior of nylon 66 monofilaments was studied under two loading conditions, pure bending or simple torsion. For each mode, results are expressed in terms of the measured decay in stiffness with numbers of cycles over a range of maximum applied strain levels. Fatigue lifetimes are presented in S–N format where the log number of cycles of fatigue for a 40% decay in stiffness (N) is plotted as a function of applied strain (S). The failure mechanism for these fibers in each fatigue mode reflects the morphology of semicrystalline‐oriented synthetic fibers. In torsion, many longitudinal cracks form around the perimeter of a fiber as the result of cleavage of the relatively weak interfibrillar bonds in nylon 66. In bending, cracks form within kink band boundaries and grow at an oblique angle to the fiber axis. © 1992 John Wiley & Sons, Inc.
Interpenetrating polymer networks of polyurethane and vinyl ester resin for reactive injection molding process
Authors: Chen Ning Ping , Chen Yong Ling , Wang Dei Ning , Hu Chun Pu , Ying Sheng Kang
Published: April 2003

Three kinds of polyurethane (PU) and vinyl ester resin interpenetrating polymer network (IPN) have been synthesized to study their morphologies and mechanical properties for the potential application in the reinforced reactive injection molding process. For the PU prepared from uretonimine modified pure MDI, the macrophase separation of the IPNs between the rubber and plastic phases was found by DSC measurement and scanning electron microscopy (SEM) observation, whereas the interpenetration between the two networks was also observed on SEM photos at least around the area of interface. However, for the IPN systems including PU prepared from TDI or graft polyol, which was synthesized by using macromer technique, the compatibility between the two phases is excellent. The mechanical properties of these IPNs were measured and could be correlated well enough with their morphologies. The IPN prepared with graft polyol exhibited the best mechanical properties over all IPN specimens studied in this work. © 1992 John Wiley & Sons, Inc.
Syntheses and electric conductivities of poly(methyl vinyl ketone‐co‐acryl amide)s reacted with phosphorus oxychloride
Authors: Kim Dae Young , Ha Chang Sik , Choi Sam Kwon , Cho Won Jei
Published: April 2003

Studies have been made on the conductivities of poly(methyl vinyl ketone‐co‐acryl amide) [poly(MVK‐co‐AAm)]s after having reacted with phosphorus oxychloride. It was found that the conductivities were dependent on the mol ratio of [AAm] to [MVK], copolymerization temperature, and time. The effect of treatment conditions of POCl3 on the conductivities of the poly(MVK‐co‐AAm)s was shown to be significant. It was observed that the conductivities of the poly(MVK‐co‐AAm)s, treated with POCl3, are of the order of 10−6–10−9Scm−1. The maximum conductivity of the POCl3‐treated poly(MVK‐co‐AAm) was obtained as 8.7 X 10−6 Scm−1 when the mol ratio of AAm to MVK was 0.5. The conductivity of the poly(MVK‐co‐AAm) was increased with the treatment time and concentrations of POCl3. © 1992 John Wiley & Sons, Inc.