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

AbstractA series of diisocyanate‐modified, molecular weight advanced poly(ethylene ether carbonate) diols has been prepared, characterized, and formulated into polyurethane elastomers using a prepolymer process. Properties were compared to a polyurethane elastomer control in which the only variable was the diisocyanate modification. The diisocyanate modification produces polymers with increased modulus (445–730% at 25°C), improved tensile strength and hardness properties and reduced (improved) coefficients of linear thermal expansion, while still passing the notched Izod impact test. The tensile strength at break increases with increasing number of urethane moieties in the soft segment and the elongation at break also increases. The plaques studied appear to have a three‐phase morphology—a soft segment continuous phase containing amorphous hard segment, an amorphous hard segment phase plasticized by about 11% of the soft segment material, and a crystalline hard segment. The polymers based on the diisocyanate modified polyols are significantly more phase mixed than the control due to the increased amount of hard segment‐soft segment interactions taking place. The improved properties of the polymers made with the modified polyols are due to their higher hydrogen bonding protential which gives more physically crosslinked polymers.
Photodegradation of polyimides. I. A spectral, viscometric, chromatographic, and weight loss investigation of polyimides based on a hexafluorinated dianhydride
Authors: Hoyle C. E. , Anzures E. T. 
Published: April 2003

AbstractThe photodegradation of aromatic‐dianhydride‐based polyimide films in air with hexafluorinated groups in the dianhydride moiety is characterized by significant weight loss and chain cleavage. A conventional polyimide film based on pyromellitic dianhydride yields little decomposition under similar conditions of photolysis. Emission changes on photolysis of polyimide solutions demonstrate an efficient rearrangement to yield a highly fluorescent species which can be used as an effective tool for following the degradation process.
Photodegradation of polyimides. II. Thermal property changes of polyimides based on a hexafluorinated dianhydride
Authors: Hoyle C. E. , Anzures E. T. 
Published: April 2003

AbstractPolyimides based on a hexafluorinated dianhydride decrease in thermal and thermal‐oxidative stability upon photolysis with an unfiltered medium pressure mercury lamp source in air. Additionally, the glass transition of photolyzed polyimides containing the hexafluorinated moiety is lowered with increasing photolysis time. By contrast, pyromellitic‐dianhydride‐based polymers are relatively thermally stable even after prolonged photolysis under similar conditions.
Response time measurements of liquid crystal dispersed in polyester resin film
Authors: Mucha M. 
Published: April 2003

AbstractNew material consisting of nematic liquid crystal droplets from 2‐30 μm in radius in a crosslinked UV‐cured polyester resin binder was prepared. Micrographs of the samples were taken in the optical microscope with cross‐polaroids. Reorientation of the droplets by application and removal of an electric field is discussed. Electrooptic properties of the material were measured using polarized light from a helium‐neon laser. Transmittance and response time vs. voltage applied with driving frequency 2 kHz were detected on the oscilloscope and photographed. The response times were: rise time τon shorter than 20 ms at applied voltage higher than 50 V, and decay time τoff = 80 ms. They are a promising feature for this material for a display application.
Irradiation of oriented LDPE films
Authors: Nikolova M. , Mateev M. 
Published: April 2003

AbstractLow‐density polyethylene (LDPE) films deformed uniaxially at 70°C and to low draw ratios have been irradiated on a 60Co source with a dose rate of 0.33 Mrad/h in air. Their elastic modulus has been determined at room temperature and at 145°C, and their crystallinity has been studied by wide‐angle X‐ray scattering (WAXS). A two‐stage process has been proposed for the influence of irradiation on the structure and properties of the films. The first stage is characterized by enhanced chain scission in the strained regions, as a result of which structural reorganization takes place there and the crystallinity increases. This increase is greater for higher draw ratios and higher doses. The second stage is characterized by no structural changes in the material. The value of D, which separates the two stages, shifts toward higher doses for higher draw ratios. Under the conditions of the present experiment, the orientation of the films decreases the efficiency of network formation by the irradiation.
Synthesis of vinyl phenyl acetate and an evaluation of vinyl chloride/vinyl phenyl acetate copolymers
Authors: Rees Gwilym J. 
Published: April 2003

AbstractThe synthesis of vinyl phenyl acetate, by an ester interchange reaction between phenyl acetic acid and vinyl acetate and utilizing a catalyst, is described. Copolymerization with vinyl chloride, in a suspension system and using a peroxide catalyst, is described on a laboratory and pilot plant scale. Monomer/copolymer compositions, for an initial charge consisting of vinyl chloride/vinyl phenyl acetate (80/20 by weight) are presented over a range of conversions, as an indication of reactivity ratios. Discs, molded from unstabilized copolymers, show very good clarity and color stability, which improve with increased comonomer loading. Some retention of unpolymerized vinyl phenyl acetate monomer occurred, and some increase in softening points resulted following two reprecipitations from acetone into excess methanol. Compound from a 96/4 vinyl chloride/vinyl phenyl acetate copolymer has better color stability than does an equivalent vinyl chloride/vinylidene chloride copolymer compound. The enhanced color and heat stability of the copolymers is attributed to the aromatic character of the comonomer vinyl phenyl acetate.
Interfacing polypropylene/poly(BPA carbonate) blend phases with graft copolymers: Thermal and dynamic mechanical analyses
Authors: Liang Zhizhong , Williams H. Leverne 
Published: April 2003

AbstractThis paper presents data on the thermal, dynamic, and mechanical properties of polypropylene (PP) blends with bisphenol‐A‐polycarbonate (PC), to which a series of graft and block copolymers in a small quantity was added. The effect of the minor component on the crystallization and relaxation behavior of PP in the blends has been investigated and correlated with the mechanical properties obtained. The results demonstrate that the graft copolymeric additives to the blends can reduce the degree of undercooling (Tm°C − Tc°C) of the PP phase. However, the block copolymers used, substituting for the graft copolymers, showed no such function. Dynamic mechanical thermal analysis (DMTA) indicates that, with the addition of several different copolymers as minor additives to the blends, two loss peaks representing the glassy transitions (Tg) of the individual components (PP and PC) were retained, with little tendency of approaching toward each other, suggesting no obvious improvement in compatibility of the PP phase and the PC phase in the blends. Nevertheless, the inclusion of different copolymers in the PP/PC blends, in spite of the small quantity used (4%), can lead to a significant mechanical property difference of the blends. This difference could be reasonably explained from the data obtained in dynamic mechanical characterization of the different graft copolymers in PP blends.
Combined processing of polypropylene film by coextrusion and zone‐annealing
Authors: Kunugi Toshio , Yoneyama Yuko , Suzuki Akihiro , Porter Roger S. 
Published: April 2003

AbstractIn order to improve the mechanical properties of polypropylene film, a new processing combining extrusion and zone‐annealing has been applied. It was found that there are suitable conditions for each step in the combined processing. When the coextrusion draw ratio was low, the total draw ratio and modulus could be increased by the zone‐annealing subsequently done. The highest modulus was obtained when the film was coextruded at extrusion draw ratio 4 and then zone‐annealed at 120°C under 7 kg/mm2. The value was 12 GPa in Young's modulus or 17 GPa in dynamic modulus. The peak temperature of αc dynamic dispersion for the combinedly processed film was 109°C, which is higher by 10°C than that for the as‐coextruded film. Four drawing methods were compared in dynamic viscoelasticity. These methods are the coextrusion, zone‐drawing/zone‐annealing, two‐step coextrusion, and the combined processing by coextrusion and zone‐annealing. The highest dynamic modulus for each method was arranged in the above order. The combined processing indicated the most effective improvement in mechanical properties, because it is believed that lamellae in the original film were broken by cooperating interaction of shear stress, compression, and tension on coextrusion and then the superstructure with a high crystallinity and a high molecular orientation was formed on zone‐annealing.
Toughening of epoxy resins by modification with aromatic polyesters
Authors: Iijima Takao , Tomoi Masao , Tochimoto Takuya , Kakiuchi Hiroshi 
Published: April 2003

AbstractAromatic polyesters, prepared by the reaction of phthalic or isophthalic acids and α,ω‐alkanediols, were used to reduce the brittleness of bisphenol‐A diglycidyl ether epoxy resin cured with methyl hexahydrophthalic anhydride. These polyesters were effective as modifiers for toughening of the epoxy resin system. The most suitable composition for modification of the epoxy resins was inclusion of 20 wt % of poly(ethylene phthalate) (MW 7200), which resulted in a 150% increase in the fracture toughness (KIC) of the cured resin at no expense of its mechanical properties. The effectiveness of poly(alkylene phthalate)s as modifiers decreased with increasing the chain length of alkylene units. The toughening mechanism was discussed based on the morphological and dynamic mechanical behaviors of the modified epoxy resin system.
Multifrequency analysis of the α relaxation region of high‐density polyethylenes: Influence of thermal history
Authors: Orozco Jose A. Gonzalez , Rego Jose M. , Katime Issa 
Published: April 2003

AbstractThe activation energy analysis of the dynamic‐mechanical α relaxation has been carried out as a function of thermal history for several high‐density polyethylenes. The air‐quenched samples display a unique α relaxation whose temperature dependence fits a constant activation energy regardless of the structural features of the samples, whilst the isothermally crystallized samples, on the other hand, display an asymmetric α peak that, often, splits into two, which does not fit a constant activation energy. The asymmetry of the α peak as well as the splitting has been explained accounting for two different relaxation time distributions. The dependence of the intensity of the α and α′ relaxations on frequency have been discussed in terms of different mean relaxation times and amorphous layer thickness.
Physical and mechanical properties of henequen fibers
Authors: Cazaurang‐Martinez M. N. , Herrera‐Franco P. J. , Gonzalez‐Chi P. I. , Aguilar‐Vega M. 
Published: April 2003

AbstractA study of morphology, physical, and mechanical properties of henequen (Agave fourcroydes) fibers have been performed in this article. It has been concluded that properties of the fibers are more uniform in their middle section. As other natural hard fibers, henequen has a relative high tenacity, low elongation at break and a low modulus. These properties suggest that the fiber could be used as reinforcing agent in composite materials.
Synthesis of polymers with long side chain of N‐alkyl esters and their effects on pour‐point depression of oil
Authors: Huiyang Zeng , Weibang Zhang , Zhuomei Li 
Published: April 2003

AbstractThree poly(n‐alkyl acrylates), PA‐14, PA‐16, and PA‐18, and three poly(vinyl alcohol) aliphatic acid esters, PVA‐14, PVA‐16, and PVA‐18, have been synthesized. They are white crystalline polymers at room temperature and characterized by IR, DSC, SALLS‐photometer, and polarizing microscope. Both the melting point and heat of fusion of PVA–esters are larger than those of the corresponding PA–esters, and the sizes of spherulites of PVA–esters are also larger. This may be attributed to the different order of linking in the ester group and the OH group residue in PVA–esters. In the testing of the effects on pourpoint depression of some petrolic oils, only PA‐14 and PVA‐14 are effective for 0# diesel oil. The influences of molecular weight and molecular weight distribution of PA–esters and PVA–esters upon the pour‐point depression of oil are negligible. These results show that the length of n‐alkyl side chain of the polyesters plays the most important role in depressing the pour‐point of petrolic oil and that the order of linking in the esters group seems to be in no relation to this effect.
PVT scaling parameters for polymer melts. II. Error in all variables
Authors: Hartmann Bruce , Simha Robert , Berger Alan E. 
Published: April 2003

AbstractAn algorithm is discussed for determining best‐fit scaling parameters in the PVT equation of state of polymer melts from experimental data. The underlying theoretical expressions are those employed in our preceding work. There it was assumed that values of pressure and temperature are known exactly and experimental uncertainty was admitted in the volume solely. This condition is now relaxed to allow for errors in P and T also. The methodology developed involves multiple small nonlinear fitting problems for two or three unknowns at a time. We employ it on the experimental data base in the earlier work, which consists of 11 polymer melts. To these is added ethylene monomer, analyzed earlier by Nies et al. by different methods. The numerical values of the scaling parameters differ by at most a fraction of a percent from those in the earlier computations and enhance the accuracy of fit but slightly. The significant improvement over the consecutive procedure (analysis of atmospheric pressure isobar, followed by isotherms at elevated pressures), seen earlier, continues therefore. The scaling parameters so obtained should represent the ultimate in computational accuracy consistent with a specified experimental accuracy. This may have a bearing ultimately on the issue of modeling molecular characteristics, expressed through the scaling parameters, versus macroscopic properties. Using the parameters determined here, it is shown that the entropy is correlated with the scaling temperature and that the flexibility parameter is related to polymer complexity.
Sag equation for coatings on rotating substrates
Authors: Frisch H. L. , Scopazzi C. 
Published: April 2003

AbstractWe develop the sag length equation for coatings on rotating substrates, neglecting Coriolis force effects. The equation is integrated analytically for both Newtonian and some cases of non‐Newtonian flow. For rotating substrates, the sag in one direction is compensated for by sag in the opposite direction, and unlike the nonrotating case, the sag is not proportional to time.
Structural effect of the microgels with a core‐shell morphology synthesized from poly(α‐methylstyrene‐b‐methyl methacrylate) on the swelling behavior of the microgel
Authors: Saito Reiko , Ishizu Koji , Fukutomi Takashi 
Published: April 2003

AbstractThe swelling behavior of the core‐shell microgels [32 mol % poly(methyl methacrylate) (PMMA) core and 68 mol % poly(α‐methylstyrene) (PMeSt) shell], the random mixing microgels with 32 mol % PMMA and 68 mol % PMeSt, and the PMMA microgels was investigated in two solvent systems (toluene/n‐hexane and benzene/n‐butanol) by turbidimetric titrations from the viewpoint of the structural effect of the microgels. All coreshell microgels did not precipitate in the solvent in which the material block copolymer had perfectly precipitated. For the core‐shell microgels, the flat regions appeared on the way to perfect turbidity. From the measurement of the composition of the solvent swollen in the polymers and the microgels, it was determined that these anomalous phenomena were due to the properties of the polymer micelles in the core‐shell microgels.
Diffusion and subsequent polymerization of styrene in oriented polypropylene matrix
Authors: Trznadel M. , Milczarek P. , Kryszewski M. 
Published: April 2003

AbstractResults of investigations of styrene diffusion into oriented polypropylene matrix and subsequent polymerization performed in special conditions are shown for samples drawn at various temperatures to different draw ratios. It is demonstrated that styrene sorption in oriented polypropylene is relatively low, but proposed processing leads to obtaining polypropylene–polystyrene composities with large polystyrene contents.
Interpenetrating polymer network of poly(vinyl chloride) and polymethacrylates
Authors: Abu‐Isa Ismat A. 
Published: April 2003

AbstractA curable polymeric composite was prepared using equal weights of poly(vinyl chloride) (PVC), reactive polyfunctional methacrylate monomers, and inorganic fillers. Peroxide initiated in situ polymerization of the polyfunctional methacrylate monomers in the PVC matrix produced an interpenetrating polymer network (IPN) structure. The polymerization kinetics and the degree of polymerization were investigated using differential scanning calorimetry (DSC), carbon‐13 nuclear magnetic resonance (13C NMR), and solvent extraction. All measurements indicated that during polymerization, the PVC is either crosslinked by or grafted onto the methacrylate three‐dimensional network structure. The rheological properties of the composite were measured before curing using a Rheometrics mechanical spectrometer and found to exhibit mainly viscous behavior and diminished elasticity. The PVC and the methacrylate monomers form a two‐phase system when mixed at room temperature. However, when heated to 100°C the PVC dissolves in the monomers and forms a one‐phase optically clear blend with a single glass transition temperature. In the presence of peroxide, the one‐phase blend is stable and does not separate out upon cooling and storing at room temperature.
Identification of styrene copolymers and a terpolymer by second derivative ultraviolet spectroscopy
Authors: Meal Larie 
Published: April 2003

AbstractA method for distinguishing styrene copolymers and a terpolymer by second derivative ultraviolet spectroscopy will be described. The polymers were dissolved in chloroform except for one which was dissolved in 2‐butanone. Concentrations of about 5 g/L were used. The polymer solutions were applied to the removable windows of divided, quartz cells and were allowed to dry to a thin film. The ultraviolet region was scanned from 300 to 230 nm. Then thinner films were used, and the 240–200 nm region was scanned. The second derivative spectra that resulted could be distinguished easily. This technique allows rapid, sample preparation and identification of these copolymers and the terpolymer.
Chemical modification of poly(substituted‐acetylene). VI. Introduction of fluoroalkyl group into poly(1‐trimethylsilyl‐1‐propyne) and the improved ethanol permselectivity at pervaporation
Authors: Nagase Yu , Sugimoto Kikuo , Takamura Yuriko , Matsui Kiyohide 
Published: April 2003

AbstractIn order to improve the separation characteristics of membranes for pervaporation, the introduction of fluoroalkyl groups into poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) was achieved by two methods. First, 3,3,3‐trifluoropropyldimethylsilylated PTMSP was prepared via metalation of PTMSP followed by treating with 3,3,3‐trifluoropropyldimethylchlorosilane. About 6 mol % of 3,3,3‐trifluoropropyldimethylsilyl group was introduced by the polymer reaction. Second, the copolymerizations of 1‐trimethylsilyl‐1‐propyne (TMSP) with 1‐ (3,3,3‐trifluoropropyldimethylsilyl)‐1‐propyne (FPDSP) or 1‐ (1H,1H,2H,2H‐tridecafluorooctyldimethylsilyl)‐1‐propyne (FODSP) were carried out to afford TMSP/FPDSP or TMSP/FODSP random copolymers. The ratio of TMSP monomer unit and the comonomer unit, x/y, was in the range of 99/1‐85/15. All the chemically modified PTMSP membranes showed ethanol permselectivity for pervaporation of aqueous ethanol solution. In particular, the introduction of less than about 5 mol % of fluoroalkylsilylated units into PTMSP effectively enhanced the selectivity. However, excess introduction of FODSP comonomer unit caused a decrease of the selectivity, with the value being smaller than that of PTMSP membrane. Furthermore, tetrahydrofuran, acetone, acetonitrile, dioxane, and isopropanol were efficiently separated from their dilute aqueous solutions using a TMSP/FPDSP copolymer membrane.
Material design for polymer/azobenzene liquid crystal/metal salt composite films possessing thermo‐ and photoresponsive ionic conductivity
Authors: Kimura Keiichi , Morooka Hisashi , Yokoyama Masaaki 
Published: April 2003

AbstractVarious azobenzene derivatives and polymers were attempted as materials for thin composite films containing a polymer, a liquid crystal, and lithium perchlorate which can undergo ionic‐conductivity switching induced by light or heat. Poly(vinyl chloride) ‐based composite films containing enantiotropic azobenzene liquid crystals 1, exhibited significant ionicconductivity change based on thermo‐ and photoinduced phase transitions of 1, the temperature dependence on the ionic conductivity reflecting the enantiotropic phase transition behavior of the liquid crystals. Marked, reversible ionic‐conductivity switching on alternating irradiation of UV and visible lights was attained with the composite films containing 1, especially 1 (n = 12). Incorporation of monotropic liquid crystals 3 to the composite films allowed bistability in the temperature dependence on the ionic conductivity. Employment of a polycarbonate resin and poly(methyl methacrylate) as the polymer material of the composite films gave similar ionic‐conductivity changes to the poly(vinyl chloride) composite films, whereas polyethyleneoxide brought about some different results in the photoinduced ionic‐conductivity change.
Optically controlled ligand delivery. II. Copolymers containing α‐methylphenacyl bonds
Authors: Yen Hung‐Ren , Andrade Joseph D. , Kopeček Jindřich 
Published: April 2003

AbstractN‐(2‐hydroxypropyl) methacrylamide copolymers containing side chains terminated in a model ligand, N‐tert‐butyloxycarbonylglycine (Boc‐Gly), bound via photocleavable α‐methylphenacyl bonds were synthesized to test the possibility of developing an optically controlled ligand delivery system suitable for sensors. One of the copolymers was further covalently attached to 3‐aminopropyl triethoxy silane (APS) coated porous silica beads which were modified with an excess of α,ω‐diaminopoly(ethylene oxide), molecular weights 1000 or 5000. The photochemical release of ligand induced by exposure to light in solution and at the solid‐liquid interface was studied. The influence of solvent and the length of poly(ethylene oxide) (PEO) spacers on the rate of photocleavage were determined. The hydrolytic stability of the α‐methylphenacyl bond in both solution and at the solid‐liquid interface were also investigated.