bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glass transitions of styrene/α‐methylstyrene statistical copolymers and of their blends with PPO® resin
Authors: Shultz A. R. , Young A. L. 
Published: April 2003

AbstractThe glass transition temperatures (Tg) and specific heat increments (ΔCp) at Tg of S/AMS statistical copolymers having weight fractions AMS of 0.00, 0.09, 0.17, 0.26, 0.36, and 0.44 are (by DSC) 380.0 (0.280), 384.2 (0.275), 388.8 (0.284), 391.5 (0.275), 398.3 (0.272), and 405.9 (0.27) °K (J·g− ·deg−), respectively. The Tg (ΔCp) for the PPO resin are 492.2 (0.221). The glass transitions of P(S/AMS) (1) + PPO resin (2) blends having w2 = 0.25, 0.50, and 0.75 were also measured. Examination of the copolymer and blend Tg vs. composition data indicates that a relation recently proposed by Couchman gives a somewhat better approximation than the simple Fox relation. However, the nonadjustable k = ΔCp2/ΔCp1 constant in the Couchman relation must be replaced by a smaller empirical k to give a true match of calculated to observed Tg.
Intumescent flame retardants for polymers. I. The poly(acrylonitrile)–ammonium polyphosphate–hexabromocyclododecane system
Authors: Ballistreri A. , Montaudo G. , Puglisi C. , Scamporrino E. , Vitalini D. 
Published: April 2003

AbstractThe influence of ammonium polyphosphate (APP) and hexabromocyclododecane (HBCD) as flame retardant (FR) on poly(acrylonitrile) (PAN) has been examined. The APP–HBCD system behaves as an intumescent flame retardant (IFR) formulation, APP being the char‐forming agent and HBCD the blowing agent. A negligible gas‐phase mode of action was ascertained for HBCD with this substrate. A synergism between the two FR agents was observed, corresponding to about 50% increased efficacy with respect to the separate effects of the two components. Thermogravimetry (TG), oxygen index (OI), nitrous oxide index (NOI) experiments and phosphorous residue measurements were performed to substantiate the conclusion that a conclusion that a condensed phase mechanism of action accounts for all the facts observed.
Effects of sucrose on the rheological behavior of wheat starch pastes
Authors: Cheer R. L. , Lelievre J. 
Published: April 2003

AbstractThe rheological properties of starch–water–sucrose pastes have been determined under steady and oscillatory shear conditions. The results show that the effect of sucrose at concentrations of less than about 20% w/w is to increase the apparent viscosity, yield stress, dynamic viscosity, and dynamic rigidity. At higher surose concentrations the yield stress and dynamic rigidity tend to zero while values of the dynamic viscosity and apparent viscosity are reduced compared with controls. Sucrose causes the dispersed gel particles in pastes to change volume, and it is suggested that this is one of the factors responsible for the observed effects of sucrose on rheological behavior.
Birefringence of injection‐molded glassy polymers during relaxation and recovery
Authors: Qayyum M. M. , White J. R. 
Published: April 2003

AbstractBirefringence measurements have been made on six glassy polymers during stress–relaxation and recovery experiments at temperatures below Tg. Of the six polymers tested only one pair, poly(ethylene terephthalate) and a glassy polyamide (“Trogamid”), show a strong mutual resemblance in the behavior of birefringence under these conditions. The results are discussed with reference to molecular structure, and, although detailed interpretations are not offered, it is observed that the behavior is less complex for polymers which possess their most polarizable groups in the main chain or attached rigidly to it than for those polymers having polarizable side groups with relaxations which do not involve the main chain. All six polymers have been tested in injection‐molded form, and the possible consequences of this are considered. The major differences observed to occur between the different materials do not appear to be related to processing, however, and some results obtained using specimens prepared in other ways are also presented to illustrate this.
Analysis of thermal oligomerization mechanism of styrene by field desorption mass spectrometry
Authors: Saito J. , Teramae N. , Hara J. , Toda S. , Tanaka S. 
Published: April 2003

AbstractField desorption mass spectra of normal and deuterated styrene oligomers synthesized in several alkylbenzenes were measured. Analysis of the mechanism of thermal oligomerization was carried out by identifying the molecular species in the reaction system using field desorption mass spectra. As a result, the existence of several kinds of molecular species was confirmed. The minor molecular species originated from dissolved oxygen, from the cleavage of solvent radicals to which oxygen was attached, or from H–D exchange in the oligomerization of deuterated styrene. The major molecular species originated from radical telomerization of solvents and styrene dimers, from the recombination termination reaction, and from the cage reaction between initiating radicals. Field desorption mass spectrometry was found to be useful for analyzing the mechanism of styrene oligomerization as well as characterizing the oligomers.
Grafting of polyesters onto carbon black. III. Polymerization of β‐propiolactone initiated by quaternary ammonium carboxylate groups on the surface of carbon black
Authors: Tsubokawa Norio , Funaki Akira , Sone Yasuo 
Published: April 2003

AbstractBy use of carbon black containing quaternary ammonium carboxylate (COO−N+R4) groups as catalyst, the anionic ring opening polymerization of β‐propiolactone (PL) was carried out at 50°C. Although carbon black itself was unable to initiate the polymerization of PL, carbon black containing COO−N+R4 groups, which was prepared by the reaction of carboxyl groups with corresponding quaternary ammonium hydroxide, was found to be able to initiate the polymerization. The carbon black obtained from the polymerization gave a stable colloidal dispersion in an organic solvent, and it was confirmed that the polyester formed was effectively grafted onto the surface. In addition, the effect of quaternary ammonium countercation on the polymerization was investigated.
Rheology‐processing‐property relationships in tubular blown film extrusion. II. Low‐pressure low‐density polyethylene
Authors: Kwack Tae Hoon , Han Chang Dae 
Published: April 2003

AbstractAn experimental investigation was undertaken to establish rheology‐processing‐property relationships in the tubular blown film extrusion of low‐pressure low‐density polyethylene (LP‐LDPE). For the study, three commercial LP‐LDPE resins, each from a different resin manufacturer, were used in producing tubular films, by employing the apparatus described in Paper I of this series. Both molecular and rheological characterizations of the resin were conducted, enabling us to interpret the tubular film blowing characteristics of the resins. Correlations were obtained between the processing variables (namely, blowup and takeup ratios) and the tensile properties of the films. The tubular film blowing characteristics of LP‐LDPE and HP‐LDPE resins are compared. Differences in the rheological properties (namely, elongational viscosity) of the two types of resin are used in explaining the experimentally observed differences in their tubular film blowability.
Relationships between the synthesis conditions and the characteristics of anion exchangers
Authors: Luca Cornelia , Poinescu Ig. , Avram Ecaterina , Ioanid Aurelia , Petrariu I. , Carpov A. 
Published: April 2003

AbstractSeveral macroporous styrene–divinylbenzene copolymers were prepared using different diluents. The copolymers were chloromethylated with monochlor methyl ether and aminated with N,N‐dimethyl‐2‐hydroxyethylamine in order to perform strongly basic anion exchanger, type II. It was established that the network morphology of anion exchanger determines its ion‐exchange rate. It was, also established, by means of transmission electron microscopy, that chloromethylation reaction led to the morphological changes in the macromolecular network of the copolymers.
Semi‐ and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. II. Polyurethane–poly(methyl acrylate) semi‐1‐interpenetrating polymer networks
Authors: Hourston D. J. , Zia Y. 
Published: April 2003

AbstractA series of semi‐1‐IPNs based on polyurethane networks and poly(methyl acrylate) were prepared, and their properties and morphologies investigated. All the materials showed substantial phase separation, but the phase sizes were orders of magnitude smaller than those observed for blends of the same linear polymers. The effects of the isocyanate/hydroxyl ratio used in the preparation of the polyurethane, of the molecular weight of the linear polymethyl acrylate component, of the overall composition, and of the molecular weight between crosslinks in the polyurethane networks were investigated. Stress‐relaxation experiments were conducted over a range of temperatures and master curves were produced for both components of the semi‐1‐IPNs and for a semi‐1‐IPN containing 40 wt% polyurethane. It was found that both the components obeyed a WLF type of equation, but that the semi‐1‐IPN only showed this type of behavior over a limited temperature range. Several reinforcement theories were applied to experimental dynamic storage modulus data. The closest fit was given by the Davies equation and by the logarithmic rule of mixing. By changing the exponent in the Davies equation to 1/10, a close fit was found. Application of a modified Takayanagi model indicated that these semi‐1‐IPNs showed some dual phase continuity when the poly(methyl acrylate) composition was relatively high.
Diffusion of dyes in adsorptive dyeing
Authors: Kumazawa Hidehiro , Sada Eizo , Ando Tetsuo 
Published: April 2003

AbstractThe concentration dependence derived from both steady‐state permeation and unsteady‐state dyeing runs for a system of acid dye C. I. Acid Blue 182‐nylon 6 film was analyzed in terms of parallel diffusion with simultaneous multimodal adsorption proposed in the previous paper. The present dyeing process was governed by the surface diffusion incorporating three kinds of Langmuirean adsorption modes. The concentration dependence of the diffusion coefficient of the cationic dye C. I. Basic Red 22 in the anionically modified polyester fiber Dilana measured by Ostrowska et al. [B. Ostrowska, A. Narebska, and H. Krzystek, J. Appl. Polym. Sci., 26, 463 (1981)] was satisfactorily interpreted by the parallel diffusion incorporating two kinds of Langmuirean adsorption modes.
The effects of degree of mixing on the properties of filled elastomers
Authors: Lee Michael C. H. 
Published: April 2003

AbstractA new technique has been established for improving the degree of mixing of the filler in an elastomer matrix. This technique includes a unique heating and colling mixing procedure in conjunction with surface modification of the carbon black and proper choices of polymers. The heating cycle is for decreasing the microvoid concentration and for enhancing polymer–filler adhesion. The cooling cycle is for improving the degree of mixing of the filler. Experimental data obtained from several polychloroprene systems strongly substantiate the new mixing technique. The results clearly show that a good degree of mixing obtained using the foregoing mixing technique can indeed enhance the mechanical and permeability properties of filled elastomers.
New aspects in cationization of lignocellulose materials. I. Preparation of lignocellulose materials containing quarternary ammonium groups
Authors: Antal Miroslav , Ebringerová Anna , Šimkovic Ivan 
Published: April 2003

AbstractTMAHP derivatives were prepared by the reaction of beech sawdust with CHMAC in alkaline medium. The examination of the reaction conditions showed that the most suitable molar ratio was NaOH/CHMAC = 1.8 (1 ml 17.5% NaOH/1 mL 50% CHMAC). At this ratio the maximum degree of substitution expressed by the exchange capacity of 0.35 mmol/g of modified sawdust was obtained by using 1.5–2mL of 50% aqueous solution of CHMAC/g sawdust. The optimal reaction time at 60°C was 2 h. This condition gave yields of modified sawdust above 90% and soluble derivatives mainly consisting of hemicelluloses up to 12%.
New aspects in cationization of lignocellulose materials. II. Distribution of functional groups in lignin, hemicellulose, and cellulose components
Authors: Antal Miroslav , Ebringerová Anna , Šimkovic Ivan 
Published: April 2003

AbstractThe distribution of functional groups in the three main components of beech after alkylation with 3‐chlor‐2‐hydroxypropyltrimethylammoniumchloride (CHMAC) was studied. By fractional extraction of hemicellulose combined with delignification it was found that the three components were substituted to various extents. The exchanging capacity decreased in the following order: hemicellulose, lignin, and cellulose. The obtained degree of substitution is related to the accessibility and reactivity of the individual components in the wood. Hemicellulose, which is substituted the most, can be extracted from modified sawdust with water. This represents a new method of hemicellulose isolation from native plant materials.
Chemical modification of polystyrene. V. Sulfonic acid resins from anhydride substituted polystyrene
Authors: Biswas Mukul , Chatterjee Shakuntala 
Published: April 2003

AbstractChemically modified polystyrenes based on the condensation of polystyrene with phthalic anhydride, trimellitic anhydride, and cis‐1,2,3,6‐tetrahydrophthalic anhydride have been processed into sulfonic acid cation exchange resins. The effects of variation of sulfuric acid amount and the temperature of sulfonation on the synthesis and the ion‐exchange capacities of the resins have been established. The resins have finally been characterized with respect to their structures by IR and elemental analysis data. The total ion exchange capacity as well as the salt‐splitting capacity and the pH‐metric titration characteristics of these resins have also been determined. These resins posses better ion‐exchange capacities than the conventional styrene based resins.
Effect of crystallinity on gas permeation in miscible polycarbonate–copolyester blends
Authors: Preston W. E. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractPermeation rates of helium, methane, and carbon dioxide in miscible blends of polycarbonate and a copolyester were measured at 35°C. The permeabilities for semicrystalline blends having copolyester cyrstallinity induced by annealing were compared to fully amorphous blends. Crystallinity caused a slightly greater impedance to carbon dioxide transport than it did for helium or methane. The relative rates of permeation of one gas compared to another, an issue important for membrane separations, varied greatly with blend composition; however, the effect of crystallinity was not large.
Nucleation of PET crystallization by metal hydroxides
Authors: Aharoni Shaul M. 
Published: April 2003

AbstractPET formulations containing small amounts of nonalkali metal hydroxides were prepared by extrusion from the melt. The efficiency of the hydroxides as nucleating agents was estimated from the elevation of Tcc, the crystallization temperature upon cooling from the melt, normalized for the purpose of comparison to a single convenient Mw (or the corresponding intrinsic viscosity). The results show that metal hydroxides capable of releasing water within the processing temperature interval of PET are effective nucleating agents for the crystallization of the polymer. Hydroxides releasing water out of said interval do not nucleate PET. There are two proposed nucleation mechanisms: (a) a localized severe hydrolysis of PET by the water released in the immediate neighborhood of the hydroxide particles and (b) a localized supercooling of the PET in the vicinity of the particles by the released water. The hydrolyzed PET of sharply reduced molecular weight has a Tcc significantly higher than the Tcc of the unhydrolyzed majority of the polymer. Upon cooling from the melt, and with the possible localized supercooling, the PET in the immediate vicinity of the hydroxide particles crystallizes first, nucleating the rest of the polymer. At present we can not verify whether both mechanisms operate concomitantly and which one of them is dominant.
Radiation vulcanization of natural rubber latex with polyfunctional monomers
Authors: Makuuchi Keizo , Hagiwara Miyuki 
Published: April 2003

AbstractNatural rubber latex was irradiated with γ‐rays from Co‐60 in the presence of polyfunctional monomers to accelerate crosslinking of rubber molecules. Hydrophobic monomers were more effective in accelerating the vulcanization than were hydrophilic monomers. This was ascribed to high solubility of hydrophobic monomers in rubber particles. Among the hydrophobic monomers, neopentylglycol dimethacrylate (NPG) exhibited the highest efficiency in accelerating the vulcanization. Advantages of using NPG are (1) high colloidal stability of the irradiated latex and (2) high thermal stability of dried rubber film.
Surface wettability of human hair. I. Effect of deposition of polymers and surfactants
Authors: Kamath Y. K. , Dansizer C. J. , Weigmann H.‐D. 
Published: April 2003

AbstractMonitoring the wetting force exerted on a single fiber while the fiber is slowly and continuously immersed in a liquid and then withdrawn can provide several kinds of information about the physicochemical heterogeneity of the fiber surface. This method for scanning the fiber surface with an appropriate liquid has been found useful for studying the distribution of materials deposited on the surface of human hair to improve hair assembly properties, such as cationic polymers used in hair conditioners. It is shown how wetting force vs. immersion depth curves can reflect not only the average distribution of the material on the surface, but also the degree of uniformity of the deposit; further, wetting force curves for multiple immersions of the same treated fiber indicate the ease of desorption of the surface material. The results for the systems studied, which include mildly oxidized hair and smooth nylon fibers for comparison, show how the relation between the critical surface tension of the fiber and the surface tension of the treating solution influences distribution and substantivity. Finally, data on the difference between advancing and receding wettability indicate how this hysteresis is related to the nature of the surface and to surface coverage by treating agents.
Thermokinetics and chemorheology of the cure reactions of the tetraglycidyl diamino diphenyl methane–diamino diphenyl sulfone epoxy systems
Authors: Apicella A. , Nicolais L. , Iannone M. , Passerini P. 
Published: April 2003

AbstractThe cure behavior of commercial grade TGDDM–DDS mixtures of compositions ranging from 10 to 100 phr of hardener and the thermal polymerization of the epoxy component are analyzed by means of differential scanning calorimetry. The kinetic parameters and heats of reaction determined in isothermal and dynamic scans suggest that DDS primary amine addition and epoxide etherification dominate the cure reactions. The primary amine epoxide addition is characterized by overall heat of reaction (referred to the weight of the epoxy component) of 255 cal/g and by an activation energy of 16.6 kcal/mol. The corresponding values for the etherification reaction are, respectively, 170 cal/g and 41 kcal/mol. A method of derivation of the epoxide conversion from the heat evolved in DSC thermal scans of these systems is presented. The results are in good agreement with independent IR determinations. The steady shear and oscillatory viscosity measurements and the calorimetric analysis of the isothermal cure at 140°C, 160°C, and 180°C of a TGDDM–DDS mixture containing 35 phr of hardener indicate that gelation is principally governed by the primary amine addition. The gelation limits calculated in isothermal tests by combining the calorimetric analysis and the theory describing the nonlinear copolymerization of the tetrafunctional TGDDM with an essentially difunctional DDS were in good agreement with the values experimentally determined through rheological measurements.
High density polyethylene/polystyrene blends: Phase distribution morphology, rheological measurements, extrusion, and melt spinning behavior
Authors: Min Kyonsuku , White James L. , Fellers John F. 
Published: April 2003

AbstractAn experimental study of the development of phase morphology, rheological properties, and processing behavior of mechanical blends of a polystyrene (PS) and a high density polyethylene (PE) is presented. Phase morphologies were determined by scanning electron microscopy for (i) products prepared in a screw extruder/static mixer system, (ii) samples removed from a cone‐plate viscometer, (iii) extrudates, and (iv) melt spun fibers. Disperse phase dimensions were measured. The values varied from 1–5 μm in the products from static mixers. The dimensions of the dispersed phase in the blend products from the cone plate and capillary die were of the same order. The melt‐spun fibers exhibited disperse phase dimensions as low as 0.35 μm. Polystyrene was extracted from the blend fibers producing small diameter, PE fibrils, or minifibers. Both the initial melts and the blends were rheologically characterized. The shear viscosity and principal normal stress difference N1 exhibit maxima and minima when plotted as a function of composition. The characteristics of extrudates and melt spinning behavior of the blends were investigated. The shrinkage of extrudates of PE is much greater than PS. Additional small amounts of PE to PS greatly increase its shrinkage. Addition of PE to PS initially increases extrudate swell, though the swell shows maxima and minima when considered as a function of composition. The positions of the maxima and minima correspond to those of N1. The onset of draw resonance has been investigated in isothermal melt spinning. Wide angle X‐ray diffraction studies have been carried out on blend fibers and the orientation of the crystalline polyethylene regions has been determined as a function of process conditions. This orientation decreases rapidly with the addition of polystyrene when the melt‐spun filaments are compared at the same spinline stress or drawdown ratio.
The fabrication and characterization of polymer optical conductors
Authors: Srinivasan B. , Martin G. C. 
Published: April 2003

AbstractPolymer microstructures were evaluated as thin film optical conductors. The polymer waveguides were fabricated from a photosensitive silicone polymer by selectively crosslinking the polymer with the near‐ultraviolet radiation from an argon ion laser. The optical transmittance properties of curved and linear microstructures were characterized using an optical sensing technique. For the curved guides, an exponential decay in the intensity of transmitted light with guide length was observed. The linear guides exhibited an oscillatory relationship between output intensity and length over a range of 2 mm in length. The nature of the results for the linear guides was explained by considering the variations in the refractive index across the polymer microstructure and by comparison with the optical behavior of graded‐index glass fibers.
Additives in transparent glassy polymers: Concentration profiles obtained by solvent diffusion technique
Authors: Guerra G. , Moschetti A. , Carfagna C. , Mandara U. , Cutolo A. , Solimeno S. 
Published: April 2003

AbstractConcentration profiles of additives, introduced in transparent glassy polymers by solvent diffusion technique, are analyzed by measuring refractive index profiles. Such profiles depend not only on the diffusion conditions (temperature, time, kind of solvent, concentration), but also on the conditions of solvent desorption from the polymer (temperature, pressure, solvent, and additive volatilities). In particular, poly(methyl methacrylate) (PMMA) samples modified in an outer shell by zinc chloride carried by methanol are considered.