bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large‐scale fractionation of poly(vinyl chloride) and characterization of the fractions
Authors: Pezzin G. , Sanmartin G. , Zilio‐Grandi F. 
Published: April 2003

AbstractA large‐scale fractionation of poly(vinyl chloride) (3000 g.) has been carried out by a fractional precipitation method. The molecular weight distribution of some fractions has been controlled by refractionation. The fractions have been also characterized by viscometry, osmometry, light‐scattering, and glass transition temperature measurements. The data available in literature concerning the molecular weight characterization of poly(vinyl chloride) fractions have been critically reviewed. It has been shown that most of the viscometric and osmometric data are in good agreement when the molecular weights are below 105. Above 105 the literature discrepancies can be attributed to aggregation.
Preparation of permselective membranes by means of a radioinduced grafting. I. Cation‐selective
Authors: Munari S. , Vigo F. , Tealdo G. , Rossi C. 
Published: April 2003

AbstractPermselective cationic membranes were prepared by a radioinduced grafting method of styrene onto PTFE, and a preirradiation technique was used. Some attempts were made to characterize the membranes. They show mechanical properties similar to the PTFE matrix, and good electrochemical behavior, i.e., good permselectivity, which, nevertheless, decreased with decreasing solutions concentration. Such behavior has been related to a larger swelling in diluted solutions. Swelling properties in aqueous solutions of KCl and some organic solvents are also reported.
Properties of random and block copolymers of butadiene and styrene. I. Dynamic properties and glassy transition temperatures
Authors: Kraus G. , Childers C. W. , Gruver J. T. 
Published: April 2003

AbstractThe effect of monomer sequence on physical properties was investigated for butadienestyrene solution copolymers made by organolithium initiation. The polymers varied from random copolymers of uniform composition along the polymer chain to ideal block polymers of specific block sequence arrangement and included rubbers of intermediate degrees of randomness. Uniform composition random copolymers exhibit a single glass transition temperature and a very narrow dynamic loss peak corresponding to this transition. The glass transition can be predicted from the styrene content and the microstructure of the butadiene portion of the rubber. Random copolymers in which composition varies along the polymer chain, and to some extent between molecules, exhibit a single glass transition, but the dynamic loss peak is broadened. The extent of this broadening is shown to be compatible with the sequence distribution, polymer segments of various compositions losing mobility at different temperatures. This indicates a tendency for association between segments of different temperatures. This indicates a tendency for association between segments of different chains which are similar in composition. Block copolymers display two transitions, corresponding to Tg for each type of block. The position and width of the dynamic loss peaks are related to block length and compositional purity of the blocks.
Changes in the reactivity of functional groups during polyesterification: A new approach to polymerization in fatty‐acid‐modified polyesters (alkyd resins)
Authors: Solomon D. H. , Loft B. C. , Swift Jean D. 
Published: April 2003

AbstractGel‐point calculations based on the theory of polyesterification proposed by Flory do not agree with the experimental values even when Bobalek's concept of gel point as the first formation of infinite molecules (microgel) is used. Resins covering the range 30–60% oil length were prepared and examined by electron microscopy for the presence of microgel particles. The extent of reaction at which microgel forms is discussed in relation to the concept of equal reactivity. The conditions necessary for the formation of microgel particles and the significance of these observations to the basic assumptions used in developing the theory of polyesterification are discussed.
Graft copolymerization of methyl methacrylate and natural rubber
Authors: Ghosh Premamoy , Sengupta Pranab K. 
Published: April 2003

AbstractGraft copolymerization of natural rubber and MMA was carried out in the presence of Bz2O2 or AIBN as thermal initiator and hydrogen peroxide or benzophenone as photosensitizer. From the overall copolymerization product, the rubber–PMMA graft copolymer fraction was isolated from unreacted rubber and free PMMA fractions and composition characterization of the separated fractions was done by determination of rubber unsaturation. The efficiency of grafting under different conditions has been calculated and compared.
Studies on the stretching of polypropylene film. I. Two‐step biaxial stretching
Authors: Okajima Saburo , Kurihara Kazuhiko , Homma Keisuke 
Published: April 2003

AbstractA polypropylene film was stretched at 100–160°C., quenched to room temperature, and then restretched at the same temperature perpendicularly to the first stretching. The reorientation behavior was investigated by using optical and x‐ray methods. During the restretching the monoaxial orientation caused by the stretching is converted into a new monoaxial orientation through a balanced state, where npp = nps < nss. The more or less parallel orientation to the film surface of the polypropylene molecules, brought about by the first stretching, proceeds further on restretching. nss is a linear function of the degree of stretching in area vA. The inclination of this line is independent of the type of deformation, stretching, or restretching, provided the temperature is kept constant. At 160°C. the plot of nss versus thickness is less steep than it is at 100 or 130°C. The overall reorientation apparently proceeds according to Kratky's first deformation law. The x‐ray pattern of a res̀tretched film is a four‐point diagram which indicates the existence of a pair of reorientation axes inclined symmetrically against the stretching axis. The inclination grows larger with restretching, and the axes merge into the restretching axis at extreme restretching. This phenomenon is less pronounced when the restretching is carried out at higher temperatures. The density of the restretched film is determined mainly by the stretching temperature, but extreme restretching has a tendency to lower it very slightly.
Environmental stability of ABS plastics
Authors: Kelleher P. G. , Boyle D. J. , Gesner B. D. 
Published: April 2003

AbstractExperiments with different ABS resins indicate that thermal stability in this class of polymers is dependent upon the ratio of styrene–acrylonitrile copolymer to polybutadiene rubber in the graft phase; resins containing more highly grafted rubber are more resistant to thermal oxidation. It is also found that in outdoor aging there is a minimum carbon black loading for these resins below which light screening is not effective.
Studies with thin membranes. III. Measurement of water permeabilities of parlodion membranes formed by the dip technique
Authors: Lakshminarayanaiah N. 
Published: April 2003

AbstractThin Parlodion membranes whose preparation and electrochemical properties have already been described are used to study permeation of water through them. All the membranes allowed water to go through them when subjected to gradients of mechanical pressure or chemical potential. Thicker membranes were less permeable to water than thinner membranes. The total water flow observed under the influence of an applied pressure was analyzed in terms of an existing theory due to Ticknor and found inadequate to describe the flow in thicker membranes containing low quantities of water, whereas the flow in thinner membranes of moderate water content was found to be made up of both viscous and diffusional components. On the contrary, analysis of both the total and isotopic diffusional flows from the standpoint of another theory due to Mauro showed that all membranes gave flows which were composed of both diffusional and viscous components, the proportion of the former in the total flow increasing with increasing thickness of the membrane. The permeability data have been used to derive values for both the average radius of membrane pores and the total number of such pores present in different membranes.
Kinetic analysis of the autohesion of raw SBR samples
Authors: Baumbach D. O. 
Published: April 2003

AbstractA kinetic analysis of the autohesion of raw, cold, emulsion SBR rubbers having number‐average molecular weights ranging from 74,000 to 169,000 was undertaken by using the modified Wallace tackmeter. The autohesion was observed to be a reversible process following first‐order kinetics with respect to the formation of elementary area bonds. The application of greater contact pressures during autohesion increase in the kinetic work, bond strength, and time required for bond rupture. A practical aspect of the study shows that the contact time necessary to form a complete area bond is reduced by: (1) the annealing of samples to release internal stresses; (2) production of clean and very smooth surfaces; (3) equilibrating samples under pressure prior to joining them; (4) lowering the sample temperature. The raw SBR offering the best potential autohesive properties has a Mn of 133,000 and ML‐4 (212°F.) of 66.
Stress softening in natural rubber vulcanizates. Part V. The anomalous tensile behavior of natural rubber
Authors: Harwood J. A. C. , Payne A. R. 
Published: April 2003

AbstractStress‐strain cycling of natural rubber to high strains produces greater softening than amorphous rubbers, but only if the force on the sample is relaxed below a certain value during the cycle. This phenomenon, attributed to crystallization shows why nonrelaxing tests give a longer fatigue life than relaxing tests.
The use of porous glass as a column packing for gel permeation chromatography
Authors: Cantow M. J. R. , Johnson J. F. 
Published: April 2003

AbstractUse of porous glass with a broad pore‐size distribution as a column packing for gel permeation chromatography has been investigated. The porous glass is readily available, and columns are packed easily and have excellent mechanical stability. Separations of polystyrene over molecular weight ranges of 500–2,000,000 have been obtained. Porous glass thus appears to be a useful packing material for gel permeation chromatography.
Size analysis of polymer latex powder. Comparison of results obtained by means of the I.C.I.–Joyce, Loebl disk centrifuge, the coulter counter, and the electron microscope
Authors: Eckhoff R. K. 
Published: April 2003

AbstractThe volume frequency size distribution of PVC latex powder was determined by means of three different methods, which all gave the same frequency maximum at about 0.8–0.9 μ diameter. While the electron microscope analysis, which allows the agglomerates to be resolved into individual primary particles, did not show any particles above 1.5 μ in a sample of 9000, both the Coulter counter and the disk centrifuge showed a considerable amount of larger particles.
Regulation of molecular weight of styrene–butadiene rubber. II. Influence of variation of polymerization recipe on the regulating efficiency of diisopropyl xanthogen disulfide
Authors: V´clavek Vladimíar 
Published: April 2003

AbstractThe influence of kind and amount of an anionic emulsifier, pH of water phase, addition of free rosin, and content of conjugated structures in rosin on the regulation efficiency of diisopropyl xanthogen disulfide in emulsion copolymerization of butadiene with styrene at +5°C. was studied. The apparent chain transfer constant C decreased in the order: Li+ > Na+ > K+, for the cations with the hydrolysis of rosin soap. This soap is replaceable with other anionic emulsifiers, C being dependent on the absorption area of one soap molecule. With increasing amount of soap the value of C decreased. With the decreasing pH of the water phase, the value of C increases. This fact can be explained by the increase in hydrolysis of carboxylic groups of rosin and oleate soaps and an increase in the permeability of the monomer–polymer particle surface to molecules of regulator. This tendency does not exist in the case of sulfonate‐type soaps. After addition of free rosin to the monomer phase, a similar increase in C is noted. The value of C increased also with an increase in the content of conjugated structures characterized by a value δ, which is related to the retardation of polymerization. The standard polymerization recipe at pH 10.8 is suitable from the point of view of using diisopropyl xanthogen disulfide as a molecular weight regulator.
Regulation of molecular weight of styrene–butadiene rubber. III. Choice of regulator from the homologous series of aliphatic mercaptans
Authors: Václavek Valdimír 
Published: April 2003

AbstractThe regulating efficiency of four aliphatic mercaptans was studied in emulsion copolymerization of butadiene with styrene, at +5°C. with the use of the redox system, diisopropylbenzene hydroperoxide–complexed ferrous iron–sodium formaldehyde sulfoxylate as an initiator and the sodium soap of disproportionated rosin as an emulsifier. The apparent transfer constants C of tertiary mercaptans decreased logarithmically with increasing length of molecule. This tendency is connected with the analogous dependency of solubilities of these compounds in water. The mercaptans did not affect the rate of polymerization. The value of C is independent of the amount of regulator used. With the value of C, the amount of regulator, and the conversion known, it is possible to predict the molecular weight of the polymers, except for the region of poor regulation, where the deteriorative influence of termination and crosslinking reactions takes place. The apparent transfer constant of tertiary dodecyl mercaptan decreased with increasing rate of polymerization. After elimination of diffuse processes, the value of the actual relative transfer constant was calculated. The tertiary dodecyl mercaptan has been selected as the most convenient molecular weight regulator for emulsion copolymerization of butadiene with styrene of all compounds studied for the system mentioned.
Effect of γ‐radiation on the thermal conductivity of polypropylene
Authors: Tomlinson J. N. , Kline D. E. 
Published: April 2003

AbstractThe effect of 60Co γ‐radiation on the thermal conductivity of polypropylene (PP) has been studied over the temperature range 0–160°C. for radiation doses of 600 and 1800 Mrad. The conductivity of unirradiated specimens rises from 4.5 × 10−4 cgs units (cal./cm.‐sec.‐°C.) at 0°C. to 4.8 × 10−4cgs units at 80°C. and subsequently decreases with temperature to a value of about 3.1 × 10−4cgs units at 160°C. Upon irradiation to 600 Mrad the thermal conductivity is lowered over the 0–150°C. temperature range. Above 90°C. the conductivity decreases with temperature and becomes relatively constant at 3.4 × 10−4 cgs units from 120 to 160°C. Differential scanning calorimeter (DCS) measurements from 30 to 200°C. show that irradiation to 600 Mrad lowers the energy associated with crystalline melting and shifts the endotherm melting peak from about 160 to 105°C. Irradiation to 1800 Mrad results in additional lowering of the thermal conductivity over the 50–160°C. range, a further decrease in area of the endothermic peak and a shift of its maximum peak position to about 75°C. The effects of radiation on the thermal conductivity of polypropylene are compared and correlated with the observed effects of radiation on the dynamic mechanical behavior.
Alkali solubility of carboxylated polymer emulsions
Authors: Muroi Soichi , Hosoi Keizo , Ishikawa Teruyuki 
Published: April 2003

AbstractThe solubility of carboxylated polymer emulsions in an aqueous alkaline solution was studied. The alkali solubility was shown to depend on the degree of carboxylation, the hydrophilic nature of the noncarboxylic main components, the degree of polymerization, the glass transition temperature, the chain configuration, and the dissolution temperature. Emulsions of the copolymer containing acrylic acid units showed considerably different dissolution behavior from those containing methacrylic acid units, possibly owing to the difference in the distribution state of carboxylic units inside the particle. It is deduced that methacrylic acid units are distributed more homogeneously inside the particle than acrylic acid units.
Thermal behavior of dimethyl‐m‐carboranyl–dimethylsiloxane copolymers
Authors: Delman A. D. , Stein A. A. , Kelly J. J. , Simms B. B. 
Published: April 2003

AbstractThe manner in which a series of silcarboranylene–siloxane polymers behave in air at elevated temperatures was investigated by thermogravimetric, isothermogravimetric, and differential thermal analyses techniques. Results indicate that methyl pendant groups on the polymers undergo thermal and oxidative degradations at temperatures under 600°C. Final weight losses of the polymers, however, are significantly lower than that shown by dimethylsiloxanes. The reduced volatility is attributed to the inhibition of thermooxidation by the m‐carboranylene group in the polymer molecules. This protective influence decreases apparently as the distance between the carborane nucleus and the methyl groups increases.
Polyelectrolyte complexes: Permeability to water and potential uses in ophthalmology
Authors: Refojo Miguel F. 
Published: April 2003

AbstractComplexes from poly(vinylbenzyltrimethylammonium chloride) and polystyrene‐sulfonate are transparent, water‐insoluble materials which offer interesting possibilities in ophthalmology for contact lenses and surgical implants. The permeability to water of a series of neutral polyelectrolyte complex membranes was determined. The measurements were carried out at relatively low pressure gradients (20–900 mm. Hg). The results are in good agreement with previously reported data obtained at higher pressures (6.9 atm. and higher). The refractive index of the complexes was also determined, and apparently a linear relationship exists between the refractive index and the amount of water in the complex: 70% water, nD 1.40; 45% water, nD 1.48; 35% water, nD 1.51. A polyelectrolyte complex membrane 0.09 mm. thick containing 60% water at equilibrium swelling will have a similar permeability to water as the endothelium of the cornea (1.55 × 10−11 cm.3/sec.‐dyne) at 35°C. The same membrane, but with a thickness of 0.03 mm., will have a permeability similar to that of the whole corneal stroma (4.9 × 10−11 cm.3/sec.‐dyne). At 0.21 mm. thickness the membrane will have a permeability similar to that of the epithelium (0.67 × 10−11 cm.3/sec.‐dyne).
On the crystallite orientation in jute and mesta fibers under different moisture conditions
Authors: Ray P. K. 
Published: April 2003

AbstractThe Hermans' average angle of orientation, the angle at 40% intensity, and the Hermans' orientation factor have been studied in raw and delignified jute and mesta fibers under different moisture conditions. It is observed that the average orientation of micelles in these fibers improves on moisture absorption and further improves when the moist fiber is subjected to tension, and that the action of water is more pronounced in delignified jute fibers. The derangement of a fraction of the regions, contributing to the x‐ray pattern of these fibers, and the releasing of internal stresses have been cited here as possible caused of the phenomenon.
Selection of proper mounting media for examining heterogeneous copolymers with the phase microscope
Authors: Bond R. H. , Hannah R. E. 
Published: April 2003

AbstractA technique for examining heterogeneous copolymers with the phase microscope is described. This method is based on the use of a mounting medium that displays selective solubility toward the constituent materials, thereby masking one or more phases in order to provide suitable phase contrast and isolation of the constituent to be examined.
Thermal decomposition of additive polymerization initiators. I. Azobisisobutyronitrile
Authors: Sasaki Hideki , Nagayama Masako 
Published: April 2003

AbstractWe measured the rate of thermal decomposition of azobisisobutyronitrile (AIBN) from the rate of loss of 2,2‐diphenylpicrylhydrazyl (DPPH) on reaction of the free radicals formed by thermal decomposition of azobisisobutyronitrile (AIBN) in organic solvents with DPPH. There has been some doubt about the quantitative relation between AIBN and DPPH required to get the rate constant of thermal decomposition of AIBN. In the past, AIBN has been used in excess, and the rate constants measured by using DPPH are smaller than they ought to be. In our experiments we used as little of AIBN relative to DPPH as possible and obtained a value of 3.8 × 10−4 min.−1 at 50°C. as the rate constant of the first‐order reaction, which was shown satisfactorily by the linearity of the graph. We also obtained 32 kcal./mole as activation energy. We were also able to make clear the meaning of the result when a large quantity of AIBN was used.
Properties of random and block copolymers of butadiene and styrene. II. Melt flow
Authors: Kraus G. , Gruver J. T. 
Published: April 2003

AbstractFlow curves, log (rate of shear) versus log (shear stress), as functions of temperature were obtained for several butadiene‐styrene copolymers of fixed (25%) styrene content, differing in monomer sequence distribution. A random copolymer of constant composition along the polymer chain and narrow molecular weight distribution (MWD) exhibited behavior similar to linear, narrow MWD polybutadienes; the flow was Newtonian at low shear stresses, and the flow curves for various temperatures were accurately superimposable by a shift along the log (shear rate) axis. In a random copolymer varying in composition along the polymer chain, non‐Newtonian behavior was more pronounced, and temperature‐shear rate superposition did not succeed, a trend further perpetuated in copolymer of a single long styrene block sequence. The latter resemble branched polymers, as would be expected from association of the styrene blocks. With two styrene blocks, association produces network structures below the glass transition of polystyrene with consequent loss of flow. Disruption of these associations above Tg (styrene) imparts the greatest thermoplasticity to these elastomers. There is evidence, however, that some of the associations persist at temperatures well in excess of Tg (styrene).
Programmed polymer light‐scattering data
Authors: Evans J. M. , Huglin M. B. , Lindley J. 
Published: April 2003

AbstractAn ALGOL computer program has been devised to manipulate light‐scattering data from the Brice‐Phoenix photometer. The input consist of experimental values of the galvanometer deflections and filter factors used for each concentration c and angle of measurement θ. These are transformed to the appropriate variables in the fundamental equation including the particle scattering factor, viz: c/Qθ = (W/K*)M̄w−1[1 + (16/3) × π2n12λ〈S2〉 sin2 (θ/2)] + (W/K*)2A2c + (W/K*)3A3c2 in which Qθ is a corrected from of the Rayleigh ratio and (W/K*) is a composite constant term for the instrument and polymer–solvent system. By writing X̄ij for the variable c/Qθ at θi and cj, a function X is found by least squares to fit X̄ij, thus X = l + m sin (θ/2) + ncj + bcj2. The equations arising from minimizing ΣiK=1 ΣjL=1 (Xij − X̄ij)2 are solved by the computer to yield the best‐fitting coefficients l, m, n, and b. These can then be related simply to the molecular weight, root‐mean‐square radius of gyration, second and third virial coefficients, respectively. The final portion of the program is designed to check the fit of these coefficients. It yields a table of the differences between all experimental c/Qθ values and the coressponding ones obtained by inserting the derived l, m, n, and b into the fundamental equation. The procedure has been tested satisfactorily by using a well‐standardized sample of polystyrene in toluene at 30°C. and a wavelength of 436 mμ.