bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methyl nadimide resins: Synthesis and characterization
Authors: Alam Sarfaraz , Kandpal L. D. , Varma I. K. 
Published: April 2003

AbstractThis article describes the synthesis and characterization of several methyl nadimides endcapped resins based on tris(3‐aminophenyl)phosphine oxide. These resins were prepared by reacting methyl‐5‐norbornene 2,3‐dicarboxylic anhydride (methyl nadic anhydride) (MNA), 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, IR, and 1H‐NMR. Thermal characterization of uncured resins using DSC and TGA techniques revealed an exothermic transition accompanied by a weight loss in the temperature range of 200–350°C. Residual weight at 800°C in nitrogen was found to be 47–55%. Isothermal curing of the resins was done at 340°C for 1 h in an air atmosphere. The cured resins were stable up to 400 ± 20°C. © 1994 John Wiley & Sons, Inc.
The film formation of acrylic latexes: A comprehensive model of film coalescence
Authors: Eckersley Sarah T. , Rudin Alfred 
Published: April 2003

AbstractA comprehensive model of film formation that was proposed in an earlier article by the present authors was evaluated for latexes having a wide range of physical properties. In this model, capillary force and interfacial forces act in tandem to promote film coalescence. The emulsion polymers studied were all based on poly(methyl methacrylate‐co‐butyl acrylate). The viscoelastic nature of the copolymer was varied by the addition of molecular weight modifiers (CBr4 chain‐transfer agent and ethylene glycol dimethacrylate cross‐linking monomer) during synthesis. In contrast to the simplifications of the previous analysis, the experimental system was well characterized. The effect of water plasticization was investigated. The surface energetics of the system were studied. Also, drying kinetics were considered. Results showed that the degree of coalescence ranged from complete fusion to superficial fusion. The minimum film temperature was found to increase with increasing polymer rigidity, as is expected. Comparison of the model predictions and experimental observations validated the model. © 1994 John Wiley & Sons, Inc.
Effect of compatibility on specific volume of molten polyblends
Authors: Wang Y. Z. , Hsieh K. H. , Chen L. W. , Tseng H. C. 
Published: April 2003

AbstractThe specific volume of polymer blends with different degree of compatibility has been measured at high pressure, up to 2000 kg/cm2, in the molten state by a dilatometer. The specific volume and thermal expansion coefficient of the molten homopolymers at zero pressure were satisfactorily fitted to a simplified Simha–Somcynsky equation. The specific volume of styrene–butadiene (SBR) random copolymer, which is considered to be a compatible system, at a constant styrene composition can be calculated by an semiempirical equation based on the Tait equation. The temperature dependence of excess specific volume of SBR with different styrene content at zero pressure was estimated by a combining rule in terms of self‐and cross interactions. The concentration‐dependent equation is derived to estimate the specific volume of SBR with various styrene contents. Both the thermal and dynamic mechanical analysis of the blend from the two polystyrene (PS) and polybutadiene (BR) homopolymers show a low degree of compatibility. The weight fractions of each domain consisting of PS blending with BR and those of the components in each domain can be calculated from the mass balance on the two domains and the rearranged Couchman equation. The specific volume of PS–BR composed of two phases obeys the principle of additivity from the weight fractions of the specific volume of the corresponding phases. © 1994 John Wiley & Sons, Inc.
Morphological study of hydrogels of cellulosic super water absorbents by CRYO‐SEM observation
Authors: Yoshinobu Masahiro , Morita Mitsuhiro , Higuchi Mitsuo , Sakata Isao 
Published: April 2003

AbstractThe structures of the hydrogels of the partially hydrolyzed cellulose‐graft‐polyacrylamide copolymers as super water absorbents were examined by use of a cryogenic scanning electron microscope. The hydrogel of the wood pulp graft copolymer that had been not hydrolyzed (P/PULP‐AM) formed a spongelike structure with numerous circular micropores. The highly swollen hydrogel of the partially hydrolyzed wood pulp graft copolymer (P/PULP‐AM‐Hyd), on the other hand, formed a honeycomblike structure with polygonal pores surrounded with membraneous walls. A hydrogel of a crosslinked polyacrylamide (PAM) formed a similar structure to that of P/PULP‐AM, but the honeycomblike structure shown in P/PULP‐AM‐Hyd was not observed in the partially hydrolyzed PAM. The pore size of the honeycomblike structure of the hydrogel of P/PULP‐AM‐Hyd decreased with an increase in the amount of the crosslinker added at graft copolymerization. For the hydrogel of the P/PULP‐AM‐Hyd with less addition of the crosslinker, however, the honeycomblike structure had been broken. The hydrogel of the P/PULP‐AM‐Hyd without the addition of the crosslinker did not show a honeycomblike structure. In spite of no addition of the crosslinker, the cellulosic film and nonwoven fabric graft copolymers formed honeycomblike structures. © 1994 John Wiley & Sons, Inc.
A morphological examination of ceric ion and preirradiation acrylic acid‐grafted rayon fibers
Authors: Gupta B. S. , McDowall D. J. , Stannett V. T. 
Published: April 2003

AbstractUsing the ceric ion and preirradiation methods, acrylic acid was grafted to rayon. The fiber used was large denier (50) continuous filament, particularly suited for examining changes in morphology and properties. The grafted fiber was given decrystallization treatments involving ZnCl2 and NaOH. Optimization studies conducted to seek maximum graft with minimum homopolymer formation has been published elsewhere.1 Also published earlier were the results of changes in mechanical and physical properties of the fiber resulting from the grafting and decrystallization treatments.2 Presented in this article are the results on the effects of these treatments on the structure and the morphology of the fiber. The structural features examined were the molecular orientation, crystallinity and crystalline orientation, and the surface morphology. Based on the results of this study and those of the earlier2, it was possible to develop and propose a model of fiber structure that fits the present fiber. © 1994 John Wiley & Sons, Inc.
Quartz crystal microbalance study for chemical synthesis of polypyrrole
Authors: Ayad Mohamad M. 
Published: April 2003

AbstractThe quartz crystal microbalance was used to monitor the deposition of a smooth film of the conductive polypyrrole (PP) using a purely chemical method. The film was grown from the oxidative polymerization of pyrrole with potassium persulfate in aqueous solution. A comparison was made between the growth rate of PP films and the PP formed in the bulk at the same molar ratio of the reactants. The kinetics of the PP film formation were found to be governed by the concentration of the reactants in the bulk. The effect of HCl on the growth rate of PP films was also investigated. © 1994 John Wiley & Sons, Inc.
Curing studies on the epoxides of carbono‐ and thiocarbonohydrazones
Authors: Thangamathesvaran P. M. , Jain S. R. 
Published: April 2003

AbstractThe curing behavior of a new class of NN bonded epoxy resins has been analyzed using the simultaneous DTA‐TG, dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA) techniques. The resin systems, viz, diglycidyl ether of furfuraldehydecarbonohydrazone (DGFCH), diglycidyl ether of furfuraldehydethiocarbonohydrazone (DGFTCH), and tetraglycidyl ether of vanillinthiocarbonohydrazone (TGVTCH) with the curative, diaminodiphenylmethane (DDM), taken in stoichiometric amounts have been examined. The curing exotherm could be resolved from the decomposition exotherm qualitatively using DTA‐TG analysis. The DMA has been carried out in both the dynamic and isothermal mode to follow the curing process of the systems DGFCH/DDM and TGVTCH/DDM. The storage modulus (G′), loss modulus (G″), complex viscosity (η) and creep factor (tan δ) were measured simultaneously. The crossover point of G′ and G″, taken as the gelation point in isothermal runs, was determined to obtain time to gelation at that temperature. The isothermal runs at different temperatures have been used to calculate activation energy of the curing process up to gelation. For the difunctional resin DGFTCH, the activation energy value was found to be 18.7 kcal/mol. The thermomechanical analysis (TMA) has been used to find the glass transition (Tg0, and melt transition (Tm) temperatures. The cured tetrafunctional TGVTCH/DDM system as expected, has higher Tg than those of the two difunctional resin systems. © 1994 John Wiley & Sons, Inc.
Polyamides and polyimides prepared from diaminomaleonitrile and their cross‐linking to thermally stable resins
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractUnsaturated cyano‐substituted polyamide and polyimides were prepared from the reactions of diaminomaleonitrile with terephthaloyl dichloride and tetracarboxylic dianhydrides such as pyromellitic dianhydride and benzophenone tetracarboxylic dianhydride. The polymers were characterized by inherent viscosity measurements, by FTIR and 1H‐NMR spectroscopy, as well as by DTA and TGA. They were soluble in polar aprotic solvents and certain strong inorganic and organic acids. Upon curing at 300°C for 70 h, cross‐linked polymers were obtained that were stable up to 397–426°C in N2 or air and afforded anaerobic char yield of 56–61% at 800°C. Their glass transition temperatures as determined by the thermal mechanical analysis (TMA) method were 210–249°C. © 1994 John Wiley & Sons, Inc.
Radiation‐initiated inverse emulsion polymerization of vinylpyrrolidone
Authors: Taylor M. B. , Gilbert R. D. , Stannett V. T. , Williams J. L. 
Published: April 2003

AbstractThe radiation‐induced inverse emulsion polyerization of vinylpyrrolidone using an isoparaffinic hydrocarbon and nonionic emulsifier blend is described. High molecular weight polyvinylpyrrolidone (PVP) (1 million to 2 million Mv) was readily obtained at rapid polmerization rates (Rp ∼ 10–35 mol 1−1 s−1) to high conversions (90–95%). The polydispersity of the polymer varied from 2.6 to 4.4, suggesting that chain transfer to the polymer had occurred. Adding a polymeric surfactant to the nonionic blend modified the polymerization rate and particle‐size distribution. © 1994 John Wiley & Sons, Inc.
Graft‐copolyamide molecular composites
Authors: Aharoni Shaul M. 
Published: April 2003

AbstractA novel family of graft‐copolyamides was prepared in which several chains of high molecular weight polycaproamide (nylon 6) are grafted onto the backbone of each stiff aromatic polyamide chain. The unique feature of the present graft‐copolyamides is that the side chains are connected through amide groups directly to the aromatic rings in the stiff chain, and not to the amide groups in the backbone of the stiff chain. Because they are miscible with linear nylon 6, blends of the graft‐copolymers and nylon 6 are easily prepared. Electron microscopy, x‐ray diffraction scans, DSC runs, and solid‐state NMR relaxation and spin diffusion experiments all indicate that the aromatic stiff polyamide chains are molecularly dispersed in the graft‐copolyamides and their blends with nylon 6. In an ungrafted blend of the stiff aromatic and flexible aliphatic nylon 6, the stiff chains tend to agglomerate into small hydrogen‐bonded sheaf‐like aggregates the size of which increases upon annealing above the melting point of the flexible polyamide. The NMR results point to a substantial flexibility of the stiff chains in the graft‐copolyamides, helping to explain the levels of reinforcement reflected in the tensile properties of these materials. In the ungrafted blends, the aromatic‐chain stiffness is greatly enhanced when these chains are phase separated in the minute sheaf‐like particles. The tensile properties of the graft‐copolymers and their mixtures with pure nylon 6 are far superior to those of the ungrafted blends. The reinforcement of the flexible matrix by the stiff polyamide chains is explained in terms of the Halpin—Tsai formulation. © 1994 John Wiley & Sons, Inc.
Development and control of a blend morphology by In situ cross‐linking of the dispersed phase
Authors: De Loor A. , Cassagnau P. , Michel A. , Vergnes B. 
Published: April 2003

AbstractThe development of the morphology of a reactive blend along a twin‐screw extruder has been experimentally studied. A transesterification reaction activated by a catalyst allowed a cross‐linking of the dispersed phase during the flow in the extruder. In comparison with the nonreactive system (without catalysts), the resulting morphologies were characterized by larger dimensions. Influence of screw speed and feed rate were similar for both systems, whereas the changes along the screws were more pronounced for the reactive blend. It appeared that the local morphology was strongly dependent on the extent of the reaction. At low extent, the equilibrium between breakup and coalescence was shifted toward coalescence, whereas at high extent, the classical mechanisms were largely modified and replaced by a “coagulation” mechanism. It was shown that, for the fully cross‐linked dispersed phase, the final morphology remained remarkably stable during successive extrusion steps. For such products, the observation of a low‐frequency plateau of the elastic modulus suggested the formation of a copolymer at the interface with the matrix. © 1994 John Wiley & Sons, Inc.
Cross‐linked polymer brushes. II. Formation and properties of poly(isobutyl vinyl ether)‐b‐poly[2‐(vinyloxy)ethyl cinnamate] brushes
Authors: Liu Guojun , Xu Xiuqi , Skupinska Krystyna , Hu Nanxing , Yao Hong 
Published: April 2003

AbstractA diblock copolymer, i.e., poly(isobutyl vinyl ether)‐b‐poly[2‐(vinyloxy)ethyl cinnamate] (PIBVE‐b‐PVEC), has been shown to form polymer brushes quickly on the surface of solid substrates by deposition from a solvent selectively poor for PVEC. The resultant brush could be cross‐linked photochemically by initiating the dimerization between VEC groups of different polymer chains and the cross‐linking was extremely efficient. Crosslinked polymer brushes, as expected, were resistant to organic solvent, such as chloroform, and nitric acid attacks. Important industrial applications are expected of cross‐linked brushes. © 1994 John Wiley & Sons, Inc.
Solid‐state NMR studies of relaxations in modified duroplastic low‐stress materials
Authors: Domke W.‐D. , Halmheu F. , Schneider S. 
Published: April 2003

AbstractDuroplastic low‐stress molding materials, based on epoxy novolak resins with different siloxane modifications have been investigated with respect to the mobility of different structural elements and the morphology of the resulting polymers. Different solid‐state NMR relaxation experiments have been used to probe the mobility in a wide range of motional frequencies. Spin diffusion experiments allowed the estimation of domain sizes even in the case of highly filled polymers and indicate that the effect of low‐stress modification is correlated with microphase separation. © 1994 John Wiley & Sons, Inc.
Permeation of gases across the poly(chloro‐p‐xylylene) membrane
Authors: Tanioka Akihiko , Fukushima Noriaki , Hasegawa Koichi , Miyasaka Keizo , Takahashi Noboru 
Published: April 2003

AbstractGas permeabilities across poly(chloro‐p‐xylylene) (parylene C) films are measured with different thicknesses of 20.2, 10.0, 8.9, 4.6, 3.4, and 1.0 μm. Measurements were carried out below 1 atm and between 10 and 80°C, which are under the glass transition temperature. The temperature and pressure dependencies of the permeability and the apparent diffusion coefficients were measured. If the membrane thickness is larger than 8 μ, the gas‐transport mechanism is solution–diffusion, which implies that it is pinhole‐free, because the pressure dependency of the permeability cannot be found and the apparent activation energy of permeation and diffusion are observed. If the membrane thickness is less than 8 μ, the gas transport mechanism is pore flow combined with solution–diffusion flow because gas may penetrate both the porous area and the polymer matrix. The thinner the membrane, the higher is the permeability coefficient, since the diameter and number of pores increase with decrease of the membrane thickness. The gas permeability coefficient has different values at the same pressure or temperature. As this film is in the glassy state, it should be explained using the average ordering parameter (ξ), which is a function of temperature, pressure, gas concentration, and time. © 1994 John Wiley & Sons, Inc.
Degradability testing of radiation‐vulcanized natural rubber latex films
Authors: Thiangchanya Adul , Makuuchi Keizo , Yoshi Fumio 
Published: April 2003

AbstractThe degradability under various conditions of five kinds of radiation‐vulcanized natural rubber latex (RVNRL) films was studied. The treatments were leaching in methanol, leaching in 1% ammonia solution, mixing with tris(nonylated phenyl)phosphite (TNP) antioxidant, blending with poly(methyl methacrylate) (PMMA), and grafting with PMMA, Comparisons were made with sulfur‐vulcanized natural rubber latex (SVNRL) film. RVNRL films SVNRL film can be kept for a long time when indirectly exposed to sunlight at room temperature. However, the former degraded much more rapidly than did the latter. TNP was found to be very suitable as an antioxidant to prolong the life of RVNRL films under dry conditions. PMMA, either blended or grafted with RVNRL, was ineffective in the prevention of deterioration of RVNRL films. The rapid degradation of RVNRL products could be an advantage over SVNRL products in environmental and wildlife conservation. © 1994 John Wiley & Sons, Inc.
Effect of molecular orientation on the dielectric properties of spin‐coated polyimide films
Authors: Lin Linda , Bidstrup Sue Ann 
Published: April 2003

AbstractThe effect of molecular orientation on the dielectric properties of spin‐coated polymide films has been studied in Situ for pyromellitic dianhydride with 4,4′‐oxydianiline (PMDA/ODA) and biphenyldianhydride with p‐phenylendiamine (BPDA/PPD). The degree of molecular orientation is characterized by the optical anisotropy between the in‐plane and the through‐plane, refractive indices. The through‐plane dielectric properties are measured by fabricating parallel‐plate capacitors directly onto the silicon substrate. Both the birefringence and the dielectric constant of PMDA/ODA polyimide vary with film thickness; however, these properties are independent of film thickness for BPDA/PPD films. To confirm that the measured dielectric constant obtained from the parallel‐plate structures is free from a significant edge effect, finite element modeling of the electrstatic potential within the dielectric edge effect, finite element modeling of the electrostatic potential within the dielectric is performed. Models for both isotropic and anisotropic dielectric properties indicated that the fringing effects are indeed negligible for the film thicknesses examined. Thus, the changes observed in the measured dielectric constant are attributed to the variations in the molecular orientation. The optical anisotropy observed for the polyimides suggests a corresponding dielectric anisotropy in the films. An estimation using the Maxwell relation indicates that the dielectric anisotropy at 105 Hz is 0.31 for PMDA/ODA and 0.85 for BPDA/PPD. © John Wiley & Sons, Inc.
On the in situ generation of reinforcing fibers
Authors: Qin Yimin 
Published: April 2003

AbstractA study has been made of the formation of the microstructure of a polypropylene (pp) and liquid crystal polymer (LCP) blend. The pp/LCP mixture was fed into a single‐screw melt extruder, and polyblend fibers were made by extrusion of the melt through a spinneret plate. Samples of the melt were taken from various sections of the screw barrel, before and after the metering pump, before and after the mesh filter, before and after the die head, and in the as‐made fibers. The microstructure of the LCP phase in the blend was studied with a hot‐stage microscope. It was found that the dispersion of the LCP phase in the pp matrix was well completed before the metering pump. Planar flow and compressional strain in the metering pump had little influence on the LCP phase structure, but elongational strain in the mesh filter produced fine dispersion of the LCP phase. It was found that the LCP phase existed largely in spherical particles before the die‐head entrance. Although the extensional flow in the die entrance deformed the LCP particles into thin droplets, further elongational strain below the die head is essential if thin and long LCP fibrils are required in the polyblend fibers. © 1994 John Wiley & Sons, Inc.
Pervaporation performance of polyetherimide membranes spin‐ and dip‐coated with polydimethylsiloxane
Authors: Page C. A. , Fouda A. E. , Matsuura T. 
Published: April 2003

AbstractThe pervaporation performance of polydimethylsiloxane (SR) spin‐ and dip‐coated polyetherimide (PEI) membranes was inmvestigated for acetic acid/water mixture. The spincoating technique was used to produce a thin, uniaform coating, and compared to the dipcoating technique in terms of pervaporation performance, thickness, and uniformity of the coatiing layer. It was fould that the PEI membranes studied were water‐selective and that the water selectivity of PEI membranes increased when spin‐coated with a SR solution. It wal also fould that the water selectivity increased when the PEI membranes were conated with SR solutions of increassing concentration, Althought the permeate flux noticeably decreased. The coating thickness was measured by the weighting techniquo and the results were compared with the thickless estimation by two versins of the resistance model. It was determined that the spin‐coating technique can provide a thinner and more uniform coating than the dip‐coating technique, and that the coating solution penetrates the mem brane pores beofre coating the surface. © 1994 John Wiley & Sons, Inc.
Preparation and characterization of perlite‐filled high‐density polyethylenes. I. Mechanical properties
Authors: Akin‐öktem Gülsu , Tincer Teoman 
Published: April 2003

AbstractFour different types of high‐density polyethylenes (HDPE) were blended with perlite at different concentrations. Silane coupling agent γ‐aminopropyltriethoxv silane (γ‐APS, A‐1100) was used to enhance the adhesion between perlite and HDPEs. Ultimate tensile strength and elastic modulus increased as the perlite content increased, while ultimate elongations decreased with the increasing amount of perlite. Exceptional variations in the measured properties are explained in terms of the differences in polyethylenes used in the composites. The biggest improvement in ultimate tensile strength was observed in the highly crystalline polyethylene; on the other hand, in the absence of sialane coupling agent the high molecular weight polyethylene showed the least improvement in tensile strength. The effect of branching in HDPE composites was demonstrated. The enhancement of interfacial adhesion by using a coupling agent was also examined by scanning electron microscopy (SEM). © 1994 John Wiley & Sons, Inc.