bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) polyols. IV. Effects of poly(propylene glycol) modified diols
Authors: Harris Robert F. , Joseph Michael D. , Davidson Carla 
Published: April 2003

AbstractA series of polyurethane elastomers with a (A{BC}m)n type of structure have been prepared and characterized based on poly(propylene glycol) modified poly(ethylene ether carbonate) polyols, where the poly(propylene glycol) content and block length were varied systematically. Strength and modulus properties showed a marked dependence on modifier level and exhibited synergistic property improvements at 25–50 wt % modifier, relative to both unmodified poly(ethylene ether carbonate) diol and poly(propylene glycol) controls. DMA results indicated an increased modulus for the modified plaques throughout the rubbery plateau region, with higher thermal dissociation temperatures. Excellent organic solvent resistance was maintained with 25–50 wt % poly(propylene glycol) modification in the soft segment. Chemical structure of the polyurethane elastomers was established by proton and 13C‐NMR spectroscopy. The morphology of these modified polyurethanes appears to be quite complex. Since the modified soft segments are block copolymers of blocks with a tendency toward immiscibility, some microphase separation within the soft segment domains of the polyurethane polymers might be expected. The soft segment Tg is highest where properties are maximized, suggesting changes in phase mixing. © 1992 John Wiley & Sons, Inc.
Preparation of polymer–ceramic composite membranes with thin defect‐free separating layers
Authors: Rezac M. E. , Koros W. J. 
Published: April 2003

AbstractPolymer—ceramic composite membranes with essentially defect‐free separating layers have been prepared by a solution deposition technique. Rigid polymers were used for the selective organic layer. These included high molecular weight samples of 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethylidene]bis‐1,3‐isobenzofuran‐dione, isopropylidenedianiline (6FDA‐IPDA), 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethylidene]bis‐1,3‐isobenzofuran‐dione, methylenedianiline (6FDA‐MDA), tetramethylhexafluorobisphenol‐A polycarbonate (TMHFPC), and tetramethylhexafluoropolysulfone (TMHFPSF). Attempts to prepare composite membranes from lower molecular weight samples of bisphenol‐A polycarbonate (PC) and tetrabromohexafluorobisphenol‐A polycarbonate (TBHFPC) were unsuccessful. The PC and TBHFPC composites exhibited a decrease in the measured gas flux after polymer deposition; however, the selectivities of the composites were considerably less than that of a dense film of the same materials. A microporous ceramic membrane prepared by Anotec Separations was used as the support layer. This ceramic membrane provided minimal resistance to gas flow. The selective composite membranes were found to have high gas fluxes and gas separating abilities essentially equivalent to that of a dense isotropic film. The estimated, effective skin layer thicknesses for these membranes are on the order of 1500 Å to 1.0 μm. The formation of these composites is believed to occur through a sieving process in which large swollen polymer chains are sieved out of solution by the ceramic support. Polymer solutions that had swollen coil diameters that were smaller than that of the ceramic membrane did not produce selective composite membranes, while those solutions with swollen coil diameter that were larger than that of the ceramic membrane produced defect‐free polymer layers. © 1992 John Wiley & Sons, Inc.
Immobilization of enzymes on electrostatic medium of positively charged dimethylamino nylon gel
Authors: Kobayashi Takaomi , Miyama Hajime , Kawata Souji , Nosaka Yoshio , Fujii Nobuyuki 
Published: April 2003

AbstractUrease and glucose oxidase were immobilized by positively charged nylon gel matrix made from dimethylaminated nylon. The stability of the immobilized enzyme after preheating and incubation in organic solvent were measured and compared with that of native enzymes. Also, pH dependency of the immobilized enzymes was examined. The pH activity curves of the immobilized enzyme shift toward a low pH compared with that of the native enzyme. Using the pH difference, the electrostatic potential of the positively charged nylon gel was estimated. The estimated values of the positively charged gel were +90 and +102 mV for the immobilized urease and immobilized glucose oxidase, respectively. In the presence of buffer salt, they decreased to +30 and +24 mV, respectively. © 1992 John Wiley & Sons, Inc.
Thermodynamic modeling of the sorption of organic chemicals in thermoplastics and elastomers
Authors: Park Jae K. , Bontoux Laurent 
Published: April 2003

AbstractThe amount of solute sorbed per unit weight of sorbent, qe, and the equilibrium solubility (partition) coefficient were measured using a gravimetric method for various types of organic chemicals in thermoplastics and elastomers. A thermodynamic model was derived to predict the activity‐dependent partition coefficient and qe for a wide range of organic chemicals. The thermodynamic model produced a better fit to the measured qe values than did the Flory–Huggins equation. Partition coefficients and qe increased with increase in activity. For nonpolar compounds, qe increased logarithmically but decreased for polar compounds with an increase in the saturation organic chemical vapor concentration. Elastomers had 14–28 times greater qe values than did thermoplastics. A structure–activity relationship was found to accurately predict the partition coefficient for liphophilic organic chemicals at a specific activity. © 1993 John Wiley & Sons, Inc.
Polymers from renewable resources. I. Castor oil‐based interpenetrating polymer networks: Thermal and mechanical properties
Authors: Nayak Padma L. , Lenka S. , Panda Santosh K. , Pattnaik T. 
Published: April 2003

AbstractA number of polyurethanes (PUs) were synthesized by reacting castor oil with toluene‐2,4‐diisocyanate and hexamethylene diisocyanate and varying the NCO/OH ratio. All these polyurethanes were reacted with some acrylic monomers like ethyl acrylate, n‐butyl acrylate, ethyl methacrylate, and butyl methacrylate using a crosslinker ethylene glycol dimethyl‐acrylate and benzoyl peroxide as the initiator. The physicochemical properties of interpenetrating polymer networks (IPNs) are reported. Thermogravimetric analysis was used to study the thermal behavior of IPNs and the evaluation of kinetic parameters. Degradation mechanism has also been investigated. Some of the mechanical properties viz. tensile strength, shore‐A hardness, elongation at break, etc. are also reported. © 1993 John Wiley & Sons, Inc.
Co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyester. II. X‐ray diffraction analysis
Authors: Shinn Ted‐Hong , Lin Chen‐Chong 
Published: April 2003

AbstractA series of co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyester with different compositions were prepared by the copolymerization of either poly(ethylene terephthalate) (PET) polymer or its oligomer with p‐acetoxy‐benzoic acid. The polymeric products were subjected to solid‐state polymerization for various time intervals. Effects of composition ratio and solid‐state polymerization time on X‐ray diffraction behavior were investigated. It is found that the effect of transesterification induced by solid‐state polymerization causes an increase in crystallinity with the copolyesters having high mol % of p‐oxybenzoic acid (POB) moiety and causes a decrease in crystallinity with the copolyesters having high mol % of PET moiety. In general, the crystallinity of copolyesters is first increased and then decreased as solid‐state polymerization time proceeds. However, the crystallinity of copolyester having POB/PET = 80/20 composition is increased generally at 4‐h solid‐state polymerization. It is also found that the crystallinity of copolyesters is decreased by quenching. The copolyester based upon either PET oligomer with 4‐h solid‐state polymerization or PET polymer with 8‐h solid‐state polymerization shows the most similar X‐ray diffraction pattern with that of Eastman 10109. © 1993 John Wiley & Sons, Inc.
Properties of polyamic acid ionomers
Authors: Yu Xuehai , Grady Brian P. , Reiner Richard S. , Cooper S. L. 
Published: April 2003

AbstractPolymers containing amic acid units were produced by reacting an oligomer based on polytetramethylene oxide (PTMO) with 1,2,4,5‐benzenetetracarboxylic dianhydride (BTDA). Neutralization by a metal salt produced amic acid ionomers. Similar to other ionomer systems, neutralization from the acid to the ionomer led to the formation of a separate ionic phase as determined by dynamic mechanical analysis. Phase separation resulted in a substantial increase in mechanical properties. The effect of neutralization level, cation, soft‐segment molecular weight, and soft‐segment end group on mechanical and thermal properties was investigated. © 1993 John Wiley & Sons, Inc.
Graft copolymerization of starch with methyl acrylate: An examination of reaction variables
Authors: Patil Damodar R. , Fanta George F. 
Published: April 2003

AbstractStarch‐g‐poly(methyl acrylate) (S‐g‐PMA) copolymers containing 55–60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted PMA content, grafting frequency, and the molecular weight and molecular weight distributions of PMA grafts. Variables investigated in the graft copolymerization reaction were nitric acid concentration, ceric ion‐to‐starch ratio, reaction time, gelatinization of the starch, and reactant concentration in water. At high reactant concentrations, high conversions of methyl acrylate to grafted PMA could be obtained in less than 0.5 h at 25°C. © 1993 John Wiley & Sons, Inc.
Polystyrene–gelatin composites prepared via a gel pathway
Authors: Ruckenstein E. , Xu G. 
Published: April 2003

AbstractComposite polymers of polystyrene and gelatin have been prepared using a gel pathway. The gels have been obtained by mixing at 50°C an aqueous solution containing gelatin and a surfactant (SDS) with styrene containing an initiator (AIBN). The obtained emulsions have the appearance of gels and are very stable both at room temperature and at 50°C. At 50°C, these gels are liquidlike with high viscosity; at room temperature, solidlike gels are formed when the gelatin content is sufficiently high. Polymerization of the gels can be achieved in several days at room temperature and in 24 h at 50°C. Composite polymers with different water‐absorbing capacities have been produced by controlling the polymerization temperature and duration. These composite polymers are insoluble in water, ethanol, octane, and cyclohexane, but exhibit some swelling in these liquids. Additional thermal treatment at relatively high temperatures increases the mechanical strength of the composites. © 1993 John Wiley & Sons, Inc.
Surface modification of ultrahigh molecular weight polyethylene fibers by plasma treatment. II. Mechanism of surface modification
Authors: Gao Shanglin , Zeng Yeguang 
Published: April 2003

AbstractA detailed examination has been undertaken of the influence of surface treatment on the adhesion of ultrahigh molecular weight polyethylene (UHMW‐PE) fibers to epoxy resin. XPS, SEM, FTIR–ATR, LRS, and contact‐angle measurements have been used to characterize the chemical and physical changes of the fibers. The results, taken together, suggest that the adhesion depends on three factors: (i) chemical bonding effects, after plasma treatment, with the introduction of various kinds of oxygen‐containing groups into the surface of the nonpolar polyethylene, which greatly improve the surface energy of the fibers; (ii) mechanical keying effects; and (iii) the nonpolar dispersion force. It is concluded that these three factors can be regarded as additive and the contributions from each of them to fiber/resin adhesion are different and change with increasing treatment time. The optimum results are obtained when their respective contribution reaches about 60%, 30%, and 10%. © 1993 John Wiley & Sons, Inc.
Separation of liquid mixtures by using polymer membranes. IV. Water‐alcohol separation by pervaporation through modified acrylonitrile grafted polyvinyl alcohol copolymer (PVA‐G‐AN) membranes
Authors: Chiang Wen‐Yen , Huang Ching‐Chong 
Published: April 2003

AbstractThe acrylonitrile (AN) grafted onto polyvinyl alcohol (PVA) can improve the mechanical properties and water resistance of PVA; however, its hydrophilicity is decreased. Prepared PVA‐g‐AN membranes through modification with the NaOH and HCHO aqueous solutions can enhance its hydrophilicity. This modified PVA‐g‐AN membranes were used to separate alcohol/water solution with the pervaporation method. The flux was increased from 0.72 kg/m2 h of the original membrane to 2.06 kg/m2 h of the modified membrane. Moreover, adding a small quantity of CoSO4 to the water‐alcohol mixture can simultaneously increase the separation factor. © 1993 John Wiley & Sons, Inc.
An attempt to simulate the bowing phenomenon in tenter with simple models
Authors: Yamada Toshiro , Nonomura Chisato 
Published: April 2003

AbstractThe bowing phenomenon throughout a tenter was experimentally observed with a pilot plant of successive biaxial stretching. The observed results were compared with simulated ones, by which the deformation behaviors of film in a tenter were predicted, with the assumption that the film was homogeneous isotropic, homogeneous anisotropic, heterogeneous isotropic, or heterogeneous anisotropic for a two‐dimensional elastic body with an FEM. Comparatively good agreement between the simulated and observed results was obtained for a heterogeneous anisotropic elastic body with an initial mesh, involving in advance a plastic deformation part. © 1993 John Wiley & Sons, Inc.
Modeling poly(vinyl alcohol)‐stabilized vinyl acetate emulsion polymerization. I. Theory
Authors: Gilmore C. M. , Poehlein G. W. , Schork F. J. 
Published: April 2003

AbstractA mathematical model for particle nucleation and growth in the isothermal semibatch emulsion polymerization of vinyl acetate stabilized with poly(vinyl alcohol) is presented. In addition to the particle nucleation and growth mechanisms governing ionically stabilized polymerizations of relatively water‐soluble monomers, the model accommodates grafting onto the poly(vinyl alcohol) backbone during nucleation, and polymeric stabilization. The user supplies the emulsion recipe, process conditions and kinetic parameters, and the model predicts the various species concentrations, along with the conversion and particle size and number profiles. In part II, model predictions are discussed. © 1993 John Wiley & Sons, Inc.
Modeling poly(vinyl alcohol)‐stabilized vinyl acetate emulsion polymerization. II. Comparison with experiment
Authors: Gilmore C. M. , Poehlein G. W. , Schork F. J. 
Published: April 2003

AbstractThe mathematical model presented in Part I, accommodating the emulsion polymerization of vinyl acetate stabilized with poly(vinyl alcohol), predicts experimental conversion and particle size data with reasonable accuracy. Model predictions of measurable variables exhibit sensitivity to variables affecting either primary ungrafted particle nucleation of flocculation kinetics, but are relatively insensitive to variables affecting poly(vinyl alcohol) grafting reactions and the resulting primary grafted particle concentration. Semibatch simulations indicate that independent increases in the vinyl acetate, poly(vinyl alcohol), and initiator levels of all increase the primary grafted particle population. It is unlikely, however, that this population exceeds the ungrafted counterpart under most commercial polymerization conditions. This relative insignificance of grafting during particle nucleation is also noted in literature data simulations where, with appropriate parameter adjustments, the model predictions agree well with the batch, thermal initiation data. © 1993 John Wiley & Sons, Inc.
Morphology‐permeability relationships in biaxially oriented Pet films: A relationship between oxygen permeability and PROF
Authors: Gohil Ramesh M. 
Published: April 2003

AbstractThe effect of uniaxial and biaxial film‐processing parameters on the orientation of the phenyl ring in the crystalline and amorphous phases has been evaluated using a variety of techniques. It has been demonstrated that the total phenyl ring orientation factor (PROF) measured from refractive indices can reflect the nature of amorphous and crystalline phases as well as morphological changes taking place due to variation in processing conditions. The PROF parameter can, therefore, offer a useful relationship to predict oxygen perme‐ability for biaxially oriented PET films prepared under a variety of processing conditions. The cause of nonlinearity of oxygen permeability with birefringence, percent crystallinity, and tan δ maximum peak temperature (MPT) is discussed in detail. © 1993 John Wiley & Sons, Inc.
Anomalous dependence of the size of droplets of disperse phase on intensity of mixing
Authors: Fortelný I. , Černá Z. , Binko J. , Kovář J. 
Published: April 2003

AbstractThe dependence of phase structure on the intensity of mixing was studied for two modified polyamide/[poly(phenylene oxide) + polystyrene] (50/50) blends with different viscosity ratios of components. In these blends, polyamide forms the matrix and the mixture of miscible polymers [poly(phenylene oxide) and polystyrene] forms the disperse phase at all rates of mixing. The average size of the droplets of the disperse phase grows with increasing rate of mixing. This (rather surprising) result is explained as a consequence of the dynamic equilibrium between breakup and coalescence of droplets in a highly concentrated system at the condition of steady mixing. Generally, the dependence of droplet size on rate of mixing is not necessarily a monotonic function for blends with a high content of the disperse phase. © 1993 John Wiley & Sons, Inc.
Transport characteristics and other physicochemical properties of aged poly(1‐(trimethylsilyl)‐1‐;propyne)
Authors: Yampol'Skii Yu. P. , Shishatskii S. M. , Shantorovich V. P. , Antipov E. M. , Kuzmin N. N. , Rykov S. V. , Khodjaeva V. L. , Platé N. A. 
Published: April 2003

AbstractSamples of poly[1–(trimethylsilyl)–1–propyne] were kept for about 4 years in ambient conditions. The permeability and diffusion coefficients were examined and found to be decreased by 1–2 orders of magnitude. To ascertain the nature of the changes underwent during long‐term storage of this polymer, several physicochemical methods were applied: positron annihilation, wide‐angle X‐ray diffraction, spin probe, and density evaluation. These studies indicated that a decrease of free volume and more close chain packing took place during the aging process. IR spectroscopy and 13C‐NMR showed that oxygen‐containing products appeared in the polymer after long‐term storage. This should result in a certain decrease in the rigidity of the backbone chains and more intensive interchain in‐teractions, and, hence, in a decrease in the free volume of the aged polymer. © 1993 John Wiley & Sons, Inc.
Melt rheology and elasticity of natural rubber—ethylene–vinyl acetate copolymer blends
Authors: Koshy Alex T. , Kuriakose Baby , Thomas Sabu , Premalatha C. K. , Varghese Siby 
Published: April 2003

AbstractThe melt rheology of blends of natural rubber (NR) and ethylene–vinyl acetate copolymer (EVA) has been studied with reference to the effects of blend ratio, cross‐linking systems, shear stress, and temperature. When EVA formed the dispersed phase, the viscosity of the blends was found to be a nonadditive function of the viscosities of the component polymers at lower shear region, i.e., a positive deviation was observed. This behavior has been explained based on structural buildup of dispersed EVA domains in the continuous NR matrix. The effect of the addition of silica filler on the flow characteristics of the blends has been investigated. The melt elasticity parameters such as die swell, principal normal stress difference, recoverable shear strain, and elastic shear modulus of NR–EVA blends were also evaluated. © 1993 John Wiley & Sons, Inc.
On the critical molecular chain length of polydimethylsiloxane
Authors: Dvornic Petar R. , Jovanovic Jelena D. , Govedarica Milutin N. 
Published: April 2003

AbstractBecause a study of the results reported for the chain dimensions of polydimethylsiloxane (PDMS), critical for the onset of this polymer's non‐Newtonian flow behavior, obtained from the viscosity‐molecular weight relationships available from the literature, clearly revealed that considerable differences exist between the reported data, a detailed analysis of these data was performed together with an additional examination of 10 new PDMS samples that were selected so as to have molecular weights that would fill the gaps observed in the polymer viscosity–chain length relationship constructed from the accepted literature data. The results obtained were analyzed by using several different procedures integrated into a recently described comparative method that could allow for determination of what is called the most realistic critical value, Zwc. The latter was determined as 930 PDMS main‐chain atoms, which corresponds to this polymer's degree of polymerization of 464.5 and the weight‐average molecular weight of 34,500. It is not only shown that after elimination of some clearly erroneous data points from the previously reported relationships the obtained critical chain‐length values could very well fit the earlier relationships, but also that appropriate “master” relationships were constructed including 48 pairs of the old and 10 pairs of the new data points. It is suggested that this relationship be accepted as the best‐fit viscosity–polymer chain‐length dependence for PDMS, and it is pointed out that the obtained PDMS critical chain‐length value ranks this polymer's macromolecules as the most flexible of the corresponding long‐chain molecules presently known. © 1993 John Wiley & Sons, Inc.
Mechanical and thermal properties of UV‐curable polyurethane and polyurea acrylates
Authors: Yu Xuehai , Grady Brian P. , Reiner Richard S. , Cooper S. L. 
Published: April 2003

AbstractSoft‐segment molecular weight, soft‐segment crystallization, hard‐segment‐type, and reactive diluent level were examined in urea and urethane acrylates. Increasing soft‐segment molecular weight led to a decreased tensile modulus, increased strength, and increased elongation at break. Soft‐segment crystallization increased the modulus below the melting temperature, but decreased the modulus above the melting temperature because crystallization interfered with cross‐linking. Materials with hard segments that allowed for greater phase separation showed a higher modulus, higher ultimate stress, and higher ultimate elongation. Materials with reactive diluents 2‐hydroxyethyl methacrylate (HEMA) and N‐vinyl pyrrolidinone (NVP) showed qualitatively different behavior. HEMA caused the modulus and strength to increase with little effect on elongation up to concentrations of 50 wt %; at higher concentrations, the elongation decreased. NVP also increased the modulus and strength; however, at 40 wt % NVP, ultimate elongation increased in a well‐phaseseparated system and decreased in a poorly phase‐separated system. In tensile tests, samples with 40% NVP also showed substantial sample necking and drawing. © 1993 John Wiley & Sons, Inc.