bluuebunny/crossref_metadata_2025 huggingface dataset:
Saccharide radicals induced by UV irradiation at room temperature
Authors: Kubota Hitoshi , Ogiwara Yoshitaka , Matsuzaki Kei
Published: April 2003

The stability of saccharide radicals induced by UV irradiation at room temperature and the ability to initiate polymerization of acrylamide were investigated. UV light of 220 < λ < 300 nm was proved to form saccharide radicals effectively at room temperature. ESR signal intensity of the irradiated saccharide was in the order of sucrose > methyl‐α‐D‐glucopyranoside ≫ cellobiose > D‐xylose > D‐glucose α D‐fructose. The saccharide radicals were fairly stable at room temperature, however, the markedly declined in amount as the samples were brought to their own melting points or allowed contact with water. When an aqueous solution of acrylamide was added to the irradiated saccharide, polymerization was initiated and the conversion increased with an increasing amount of the preirradiated saccharide. Regarding the kind of saccharide, the conversion decreased in the following order: sucrose > methyl‐α‐D‐glucopyranoside > cellobiose > D‐glucose, which indicated a good agreement with the magnitude of ESR signal intensity.
Fast determination of fatty acids in oil‐utilizing resins by NMR spectroscopy
Authors: Rybicky Jaroslav
Published: April 2003

This work describes the determination of oil either as such or in oil‐utilizing resins such as alkyds and urethanes, by means of NMR techniques. Both the qualitative and quantitative analyses are demonstrated and the accuracy is assessed. Typically, the complete analysis of an alkyd resin takes less than 1 hr.
Sulfur vulcanization of natural rubber accelerated with 2‐mercaptobenzothiazole plus tetramethylthiuram disulfide
Authors: Bandyopadhyay P. K. , Banerjee S.
Published: April 2003

The sulfur vulcanization of NR by a MBT‐TMTD mixed accelerator system both in the presence and absence of ZnO and stearic acid with or without DCP has been studied. The rate of decomposition of DCP in the presence of both MBT and TMTD is quite similar to that in the MBT system alone. The reduction in crosslinking due to DCP is dependent mainly on MBT. The decomposition product of TMTD may contribute to it only at the later stage of vulcanization. Though TMTD has no influence on the decomposition rate, it reacts with MBT at least in the initial stage of vulcanization and suppresses the retardation caused by MBT on DCP vulcanization in accordance with the free sulfur decrease, the nature of crosslinking formation both in the presence and absence of DCP, and the methyl iodide treatment of the vulcanizates. The vulcanization process of the MBT‐TMTD‐S‐NR system has been interpreted in terms of both free radical and polar mechanisms. The domination of either of these depends on the dominant amount of either MBT or TMTD in the acclerator ratio. According to the initial high rate of crosslink formation, free sulfur decrease and also the initial additiveness of crosslinking in stocks containing DCP, the vulcanization process of MBT‐TMTD‐ZnO‐St. acid‐S‐NR system has been explained in terms of an ionic mechanism. The pronounced synergistic nature of such systems has been interpreted by the enhanced activation of MBT‐S‐ZnO‐St. acid complex due to the dithiodicarbamate ion formed in the initial stages of vulcanization, and also by the activation of TMTD accelerated vulcanization due to the mercaptobenzothiazylion.
A method for determining the permeability and solubility of sulfur in poly(dimethylsiloxane) (RTV)
Authors: DiGiacomo G. , Spaulding E.
Published: April 2003

A method has been devised whereby the S8 permeability and solubility in silicon resin are determined by observing the reaction between sulfur vapors and silver particles within the polymer. The particles (∼10 μm diameter), which may vary between 0.1 and 100 μm in diameter, are dispersed in the polymer at a concentration up to 20% within a glass cylinder (also an aluminum container). The polymer is cured according to procedure and exposed to S8 saturated vapors at various temperatures (55°–125°C), leaving one end of the cylinder open. The Ag particles are a perfect sink for sulfur, which is consumed as soon as it reaches the reaction boundary that separates the reacted and unreacted Ag particles. Consequently, a distinct black region containing Ag2S product is left behind as the boundary advances. The line displacement, measured at time intervals for the several temperatures, is used to calculate the gas permeability in the polymer as a function of temperature on the basis of a mass transport model developed from diffusion theory. The S8 solubility in the polymer is calculated from the permeability and diffusivity. The latter is determined independently by measuring the time that the Ag2S reaction is delayed when a layer of plain polymer separates a silver surface and the sulfur environment.
Kinetics of hydrolysis, acetylation, and deamination reactions on polyamide fibers in homogeneous medium
Authors: Lokhande H. T. , Bhattacharyya Niyati
Published: April 2003

Chemical reactions on polymers in homogeneous medium were used to characterize the structure of the macromolecules. The polymer was in the form of polyamide fibers dissolved in m‐cresol to give a fairly highly concentrated solution (approximately 6%). Kinetic studies of hydrolysis, acetylation, and deamination reactions on the polyamide fibers were carried out in homogeneous medium at different temperatures. All the three reactions studied followed first‐order kinetics. Rate constants and apparent activation energies were determined for these reactions, which show two rates—an initial fast rate followed by a slow one. A new microfibrillar model of the polymer dissolved in m‐cresol is proposed, and the existence of two rates is explained on the basis of the two‐phase structure of the proposed microfibril. The fast rate is attributed to the free chain segments, and the slow rate is shown to correspond to the regions which are strongly hydrogen bonded and which hold the various chains together to give the microfibrillar structure of the polymer in the homogeneous phase. The apparent activation energy for hydrolysis was 3.20 and 0.18 kcal/mole for the fast and slow rates, respectively. The apparent activation energy values for acetylation were 1.50 and 0.80 kcal/mole, while those for the apparent deamination reaction were 6.90 and 4.60 kcal/mole, respectively. Lower values of apparent activation energies are attributed to the ease of reaction in the difficult‐to‐penetrate regions of the microfibril due to the role played by the solvent of the homogeneous phase in carrying the reacting species inside these regions while simultaneously breaking the hydrogen bonds between the polypeptide chains. The apparent deamination reaction is shown to be a resultant reaction of simultaneous deamination and “amination” through hydrolytic breakdown of the polypeptide chain.
Polymer miscibility in mixed organic liquids having acid‐base interaction—a modified two‐dimensional approach
Authors: Chen Show‐An , Lai Wen‐Jen
Published: April 2003

A mixture of two organic liquids, each of which is a solvent for a given polymer, may become a nonsolvent mixture, if there is strong acid‐base interaction between the two solvents. Experimental results of such cases are presented for five polymers. These results are then correlated with the proposed modified form of the two‐dimensional approach. In the modification, an additional term for taking into account the acid‐base interaction is added to the expression for the hydrogen‐bonding solubility parameter of the liquid mixture; the dispersion forces and polar interactions are assumed to be undisturbed by the occurrence of the acid‐base interaction.
Mechanical and processing requirements for a shock mitigating phenolic foam
Authors: Mendelsohn M. A. , Meier J. F. , Rudd G. E. , Rosenblatt G. B.
Published: April 2003

A high load‐bearing shock‐mitigating phenolic foam was developed to meet specific compression‐deflection and gas permeability requirements. It was required that the foam display an almost constant compressive stress within the limits of 50–68 psi at strains ranging from 10% to 60%. Furthermore, the foam had to possess a highly open‐celled structure so that its resistance to gas flow would be minimal. These properties were obtained from a chemical formulation utilizing a combination of two phenolic resins, a phosphoric‐sulfuric acid catalyst system, a surfactant combination that included both a hydrophilic and a lipophilic surfactant, and a fluorocarbon blowing agent.
Blocked isocyanate‐terminated prepolymers in a delayed‐cure durable‐press finish for wool. Influence of isocyanate and blocking group structure on reactivity
Authors: Guise G. B. , Freeland G. N. , Smith G. C.
Published: April 2003

A series of prepolymers containing terminal blocked isocyanate groups was prepared by reaction of isocyanate‐terminated prepolymers [derived from a poly(propylene oxide) diol (MW = 2000) or a triol (MW = 3000) and different diisocyanates] with various blocking agents. Their curing rates with a polyepoxide crosslinking agent were measured to assess their suitability for a delayed‐cure durable‐press treatment for wool. The curing rates varied over a wide range, but commonly used blocking groups such as phenols, caprolactam, β‐diketones, and alcohols were not sufficiently reactive for the intended application, although others, e.g., oximes and certain blocking agents containing a basic center such as N,N‐diethylhydroxylamine, hydroxypyridines, and hydroxyquinolines, had the required reactivity. Blocking by 1,3‐dipolar cycloaddition of nitrones was examined, but the reactivities were too low. Prepolymers containing blocked aromatic isocyanates were more reactive than those containing blocked aliphatic isocyanates. Difunctional butanone oxime‐blocked pre‐polymers cured slightly more slowly than analogous trifunctional prepolymers.
Copolyamides derived from brassylic acid
Authors: Kim Ki‐Soo , Yu Arthur J.
Published: April 2003

Polyamides were prepared from C6 to C12 diamines with brassylic acid, a linear C13 dicarboxylic acid, derived from Crambe seed oil. One distinct characteristic of these polymers is their low moisture adsorption as compared to nylon 66 and nylon 6. To modify the properties of these nylons, multi‐component copolyamides were prepared from hexamethylene diamine and mixtures of brassylic acid with adipic, terephthalic, or isophthalic acids. It was found that the melting points of the co‐polyamides were changed by the choice and the levels of the diacids used. The melting point‐composition curves all show a eutectic minimum. The glass transition temperature of nylon 6,13 is also changed by the incorporation of other diacids. Water adsorption of nylon 6,13 increases with increased substitution of brassylic acid by other diacids in the order of adipic > isophthalic ≥ terephthalic. Mechanical properties of some copolyamides are in the same range as the commercial nylon 11 and nylon 12. The low moisture absorption, reduced fabrication temperature, and the wide range of properties obtainable through copolymerization make copolyamides derived from brassylic acid potentially suitable as specialty tubing, powder coatings, and molded machine parts. They will be commercially viable when brassylic acid becomes available on a large scale and is competitively priced.
The retention and removal behavior of perchloroethylene and dichloromethane in polyester fabric
Authors: Slaten B. Lewis
Published: April 2003

Polyester fabric was exposed to solvent at different bath temperatures. The retention of solvent by the fabric was determined. The removal of the retained solvent from the fabric was determined as a function of time and also as a function of temperature. The retention of perchloroethylene varied from >9% at 121°C to <0.01% at room temperature. The removal of perchloroethylene from the fabric was also a function of temperature, but even at 120°C significant quantities of perchloroethylene remained after 5 min of heating with nitrogen flow across the fabric. Dichloromethane was retained (>5%) at its boiling point and had similar slow removal rates as were found for perchloroethylene. Retention and removal rate data for both solvents as a function of time and temperature are presented.
Miscible blends of poly(butylene terephthalate) and the polyhydroxyether of bisphenol A
Authors: Robeson L. M. , Furtek A. B.
Published: April 2003

Melt blends of poly(butylene terephthalate) (PBT) and the polyhydroxyether of bisphenol A (phenoxy) exhibit excellent transparency above the melting point of PBT as well as for the quenched molded specimens. Dynamic mechanical and calorimetric characterization revealed single and sharp glass transitions intermediate between those for the individual constituents. Increasing phenoxy content in the blends depressed the crystallization rate of PBT due to dilution and viscosity (Tg increase) effects. The apparent miscibility is believed due to the potential specific interactions between phenoxy pendant hydroxyl (proton donor) and the ester carbonyl of PBT (proton acceptor). Heat of fusion results surprisingly show an increase in the degree of PBT crystallinity as the phenoxy content of the blend is increased. No explanation is offered at this point for this unexpected behavior.
A kinetic investigation of thermal degradation of poly(vinyl formals)
Authors: Chanda Manas , Kumar W. S. Jaywanth , Raghavendrachar P.
Published: April 2003

Several samples of poly(vinyl formal) having the same vinyl alcohol content (8–9%) but varying contents of vinyl acetate (6–22%) and vinyl formol (70–85%) were prepared and subjected to thermogravimetric analysis, in air and nitrogen atmospheres, employing both isothermal and dynamic methods. Kinetic parameters determined from both the isothermal and dynamic TGA data are compared. The activation energy is seen to be largely dependent on the degree of conversion, implying a complex degradation reaction. The activation energy is also much less for degradation in air than in nitrogen, which can be explained by a reaction with oxygen‐producing structures favoring degradation. The activation energy is less sensitive to variation in polymer composition for degradation in air than in nitrogen. Thus, in the dynamic process, the activation energy value decreases (from 36 to 23 kcal/mole) with increasing acetate content (from 6 to 22%) in nitrogen atmosphere, while in air the activation energy value increases only moderately (from 21 to 27 kcal/mole) with increasing acetate content (from 6 to 22%). The order of reaction is nearly unity, irrespective of the composition of the polymer, both in air and nitrogen.
Permeability of polyglutamic acid ester membranes to benzene vapor
Authors: Minoura Norihiko , Nakagawa Tsutomu
Published: April 2003

Permeability of poly(γ‐methyl L‐glutamate) (PMLG), poly(γ‐hexahydrobenzyl L‐glutamate)‐(PHBLG), and poly(γ‐n‐amyl L‐glutamate) (PALG) membrane to benzene vapor was studied. Permeability coefficients of all the membranes were large, of the order of 10−9–10−6 cm3(STP) cm/cm2 sec cm Hg, and increased markedly with increasing relative vapor pressure and temperature. The large permeability was due to the large diffusion coefficient. The sorption behavior of the PALG–benzene system was interpreted in terms of the theory of the mixing of solvent with side chains. The Arrhenius plots of diffusion coefficients for PMLG and PHBLG showed a break at about 29 and 40°C, respectively, where the volume‐expansion curves of each polymer also showed a break, which is thought to be related to the side‐chain motion. The diffusivity data for PALG were examined in terms of Fujita's free‐volume theory, and it was found that the value of the average free‐volume fraction in the pure polymer for PALG was much larger than that for vinyl polymers. This means that the side‐chain motion of PALG is easy and is the reason that the diffusion coefficients for PALG are large. These results indicate that the diffusion of benzene in these polypeptides takes place in the side‐chain regions between helices.
The origin of residual internal stress in solvent‐cast thermoplastic coatings
Authors: Croll S. G.
Published: April 2003

Experiments on polystyrene and poly(isobutyl methacrylate) coatings cast from toluene have shown that residual internal stress is independent of dried coating thickness and initial solution concentration. A theory is presented that predicts the magnitude of the stress and shows that it has no dependence on thickness or initial solution concentration. Internal strain is calculated from the volume of solvent lost after the coating has solidified. This solidification point is identified with the solvent concentration that is sufficient to depress the glass transition of the polymer to the prevailing experimental temperature. A one‐to‐one correlation is confirmed between the volume of solvent lost from solution during drying and the volume change of the polymer film.
Polymerization of vinyl chloride in presence of substituted olefins: Effects on molecular weight and melt rheology
Authors: Langsam Michael
Published: April 2003

Vinyl chloride (VCM) was polymerized by free‐radical suspension procedures in presence of methyl‐substituted olefins such as propylene, isobutylene, cis‐2‐butene, trimethylethylene, and tetramethylethylene. Dilute solution viscosities of polymer formed in the presence of these olefins were measured and compared to that of trichloroethylene, a chlorinated chain‐transfer agent. A pseudo‐chain‐transfer coefficient for these olefins was calculated based on solution viscosity determinations and found to be exponentially proportional to the number of allylic hydrogens. The effects on melt flow of the olefin distribution in the polymer chain were examined. Olefins at the ends of polymer chains were found to have no effect on melt rheology, whereas those in internal portions of chains were found to significantly increase melt flow.
Styrene divinyl benzene copolymers. I. Texture of macroporous copolymers with ethyl‐2‐hexanoic acid in diluent
Authors: Jacobelli H. , Bartholin M. , Guyot A.
Published: April 2003

The texture and the pore size distribution of a set of styrene divinylbenzene copolymers, prepared by suspension polymerization with various compositions and various amounts of ethyl‐2‐hexanoic acid as diluent, have been studied using nitrogen adsorption‐desorption isotherms, mercury porosimetry, and scanning‐electron microscopy. It appears that pore volume and surface area may be well predicted in a large range of conditions (divinylbenzene contents between 20 and 60%, ethyl‐2‐hexanoic acid contents between 35% and 60%). In this range of conditions there are three structures: the elementary nuclei are spherical particles of about 100–200 Å in diameter. They are organized in microspheres of about 500–1000 Å, and the microspheres form aggregates (2500–5000 Å) more or less separated by large holes. The smaller pores (<40 Å) are in the microspheres, between the nuclei; they are present only if the amount of divinylbenzene is high enough. Intermediate pores (40–500 Å) are, in the aggregates, between the microspheres, although the larger pores between the aggregates range from about 500 Å to more than 10,000 Å, depending on the amount of diluent.
Mechanical properties of polycarbonate antiplasticized with a charge‐transfer complex
Authors: Kryszewski M. , Ulanski J. , Gale¸ski A.
Published: April 2003

Polymers doped with low‐molecular‐weight charge‐transfer (CT) complexes exhibit interesting electrical and photoelectrical properties. On the basis of the results of thermally stimulated depolarization (TSD) for polycarbonate (PC) doped with tetracyanoethylene‐t‐stilbene complex and its components, some information about the mechanism of mutual interaction was obtained. The measurements of stress relaxation, mechanical moduli, and ultimate strength in a wide temperature range fully confirmed the predicted behavior of PCs doped with CT complex and its components. Doping the PC with CT complex and its components lowers the glass‐transition temperature and increases the modulus in the range −60 to +60°C. The effects of doping on the mechanical properties of PC are explained in terms of α‐ and β‐relaxations.
Novel binary chlorides containing TiCl3 as components of coordination catalysts for ethylene polymerization. II. Behavior of the resulting catalyst systems
Authors: Greco A. , Bertolini G. , Bruzzone M. , Cesca S.
Published: April 2003

Binary chlorides described in part I yielded very active catalyst systems for HDPE synthesis when they were associated with (i‐C4H9)3Al. Very high initial polymerization rates were observed for systems bases on MnCl2·TiCl3, MnCl2·2TiCl3, or FeCl2·2TiCl3 (III), but high yields, i.e., above 30 kg polymer/g Ti, could be reached only using moderate pressure of ethylene. Hydrogen consumption during ethylene polymerization was observed in the case of catalysts based on AlCl3·3TiCl3, CrCl3·3TiCl3, and other binary chlorides containing elements of the VIII group. Relevant amounts of ethane were found in the case of systems III, V, and VIII. All the mixed chlorides studied were able to reduce cyclohexene in the presence of H2 and (i‐C4H9)3Al, even though with different kinetic courses. Compounds II, III, V, and VIII and (MgCl2)1.5·TiCl3 and AlCl3·3TiCl3 were very active. The results have been explained on the basis of solubilization processes involving the heterogeneous catalysts which actually were experimentally verified during cyclohexene reduction. Analogous processes may occur also during HDPE synthesis.
Studies in the photodimerization of the diglycidyl ether of 4,4′‐dihydroxychalcone
Authors: Zahir Sheik A.
Published: April 2003

In order to elucidate the reaction mechanism involved in the photocrosslinking of epoxide resins containing the 4,4′‐dioxychalcone functional group as part of the polymer backbone, the behavior of the monomeric model compound, namely, the digylcidyl ether of 4,4′‐dihydroxychalcone, when subjected to UV irradiation has been studied in some detail. The initial photochemical reaction is trans‐cis isomerization to a photostationary state, the trans/cis ratios in this state being wavelength dependent. This is followed by a slow dimerization to dimers of the truxillic and truxinic type, the products being mainly formed from the trans isomer under our conditions of irradiation (λ = 350 nm). GPC studies on the irradiated products also reveal the formation of low molecular weight oligomers. Irradiation in the solid phase resulted in the conversion of 37% of the reacted monomer into polymer, whereas irradiation in the solution phase led to 23% of the reacted monomer being converted into low molecular weight polymer. A slow depolymerization of the dimer into the monomeric chalcone is also believed to occur on irradiation at 350 nm.
Quaternary phosphonium compounds as latent accelerators for anhydride‐cured epoxy resins. I. Latency and cure characteristics
Authors: Smith J. D. B.
Published: April 2003

Quaternary phosphonium compounds have been found to be extremely effective latent accelerators for anhydride‐cured bisphenol A epoxy resins; at concentrations from 0.01% to 0.25%, fast gel times are found in the temperature range of 135°–200°C combined with very good storage properties at ambient temperatures. Using these materials as accelerators, it is possible to formulate long‐life, one‐component epoxy resins. From gel time data, Arrhenius plots were made for some of these phosphonium compounds, and results indicate low activation energy values of the order of 16.1 kcal/mole. Reaction mechanisms are proposed to explain the effectiveness of these phosphonium compounds as latent accelerators. The initiation mechanism probably involves the formation of hydrogen‐bonded phosphonium–epoxy or phosphonium–anhydride complexes which rearrange on the application of heat to form activated species resulting in polymerization of the epoxy–anhydride components. The transfer of a proton from the phosphonium complex(es) to other epoxy or anhydride molecules would appear to be the rate‐determining step in this initiation mechanism. Comparison of other well‐known accelerators used for the anhydride cure of bisphenol A epoxy resins shows quaternary phosphonium compounds to be among the most effective accelerators disclosed to date.
Suspension bromination of high‐density polyethylene
Authors: Arroyo Nestor A. , Hiltner Anne
Published: April 2003

High‐density polyethylene powder has been brominated in suspension. The product was characterized by various physicochemical methods to determine the nature and effect of the substitution. Analysis of the infrared spectra indicates an initial addition reaction to terminal vinyl double bonds, followed by a substitution reaction on the polymer chain. The kinetic and thermal data show that the pseudo‐first‐order reaction occurs in the amorphous regions only. The brominated sites function as chain defects to decrease the crystallinity of the melt‐recrystallized polymer, prevent annealing, and cause intensity changes in the mechanical α relaxation. Limits are observed in these effects, however, which confirms the expected “blocky” rather than random nature of the substitution.
The effect of moisture presoaking on graft copolymerization of methyl methacrylate in wood under mutual irradiation by electron beam accelerator
Authors: Handa Takashi , Yoshizawa Shuji , Hatakeyama Ko
Published: April 2003

Polymerization of MMA was carried out in wood under mutual electron beam irradiation. The changes in molecular weight (Mn, Mm) and the number of polymer branches grafted to holocellulose and lignin were compared with the swelling degree (ΔLH2O) of base veneers obtained by moisture presoaking before impregnation of the monomer. Increases in molecular weight as well as in the number of both grafted branches were observed with increase in ΔLH2O up to ca. 4% in the lower range of ΔLH2O. However, for the number of polymer branches grafted to holocellulose, the increse reached a peak at ΔLH2O of ca. 4%, in contrast to the continuous increase of both molecular weights Mn and Mw. This is due to the bimolecular recombination‐type termination of the propagating radicals mutually between those originating from the holocellulose and the irradiated MMA within the cellular parts or due to their termination onto lignin. The polymer branches grafted to lignin came from the latter termination, and it was found that the lower molecular weight branches grafted to lignin came from those propagating radicals which were produced from irradiated MMA in the void space and terminating onto lignin.
Adsorption of polyacrylamide on zirconium dioxide
Authors: Chong Paul , Curthoys Geoffrey
Published: April 2003

The adsorption of an anionic‐type polyelectrolyte (polyacrylamide) onto zirconium dioxide from aqueous dispersion has been studied as a function of pH. Polymer adsorption takes place in the acid region, obeying a Langmuir‐type isotherm. Adsorption decreases with increasing pH. The zero‐point of charge (zpc) at the ZrO2–H2O interface and the nature of the ionic charge on the polymer molecules were investigated. The behavior of polymer attachment is discussed on the grounds of a nonionic bonding mechanism including H bonding and of electrostatic interaction. It has been found that the zpc of ZrO2 is at pH ∼3.5 and that the ionic properties of the polymer molecules depend, to a noticeable extent, upon the pH of the medium.
Flow properties of saturated rubber‐modified polymer melts
Authors: Itoyama Kuniyoshi , Soda Atsuhiko
Published: April 2003

The flow properties of saturated rubber‐modified polymer melts were studied using a capillary rheometer. The two‐phase polymer consists of styrene–acrylonitrile copolymer as matrix and ethylene–vinyl acetate copolymer (EVA) as rubber component. When the rubber concentration increases, melt viscosity of the polymer increases appreciably and activation energy for the viscous flow decreases. When the degree of grafting of EVA rubber increases, melt viscosity of the polymer increases, but activation energy is nearly constant at a given shear rate. It is shown that the superposition principle of shear rate–temperature is applicable to polymer containing from 0 to 12 wt‐% rubber at a temperature from 180 to 280°C and that the superposition principle of shear rate–concentration is also applicable only in the shear rate range of above 70 sec−1. Die swell ratio decreases monotonically with increasing rubber concentration. A master curve is obtained for the reduced variables of die swell ratio and shear rate using the method described by Petraglia et al. Assuming the polymer melt as a generalized Maxwell body, relaxation spectra were evaluated from die swell ratio and dependence of viscosity on shear rate.
Polyblends based on vinyl chloride/propylene copolymer
Authors: Cheng John T. , Mantell Gerald J.
Published: April 2003

Blends of vinyl chloride/propylene copolymer (VCM–P) with aromatic polycarbonate (PC) and with ABS terpolymer were studied. Particular emphasis was on characteristics of deflection temperature under load (DTUL), simply referred to as heat deflection temperature (HDT). In a binary system which contained PC and VCM–P, the HDT–composition plot exhibited an S‐shaped curve, suggesting incompatibility. In contrast, a straight‐line correlation, indicating compatibility, was found for VCM–P/ABS blends. These observations are consistent with dynamic measurements by viscoelastometer (Vibron Model DDV‐II). Compatibility of the VCM–P/PC system was improved through incorporation of ABS copolymer, as indicated by the broadening of tan δ peak. Electron photomicrographs revealed that, in a 50% VCM–P binary blend, polycarbonate existed in a string‐like morphology which differed from the compatible ABS system where the ABS copolymer was dispersed in a form of discrete particles.
Measurements of vapor sorption/desorption properties of ultrathin polymeric films
Authors: Belli Frank G. , Buckley David A.
Published: April 2003

After a brief review of various standard methods of diffusion measurements of vapors into and out of polymeric solids, a direct gravimetric method for studying the sorption/desorption process in thin polymer films is discussed. The apparatus used consisted of a sensitive electrical balance housed in a vacuum pump. The sorption and desorption characteristics of thick polystyrene films were studied for comparison with literature values. The system polystyrene/methylene chloride was chosen to calibrate the system because of its known data. Experiments were carried out using the polystyrenes PS‐5 and Dow Trycite 1000 at 35 and 50 mm Hg. Results agreed well with those reported in the literature. The apparatus was also suitable for measuring the very initial uptake of vapor. This information is important in the study of very thin films where the amount of vapor absorbed is minimum and the initial rate of uptake is almost instantaneous.
Diffusivity and solubility of organic vapors in modified polyethylene films. II. Diffusivity studies
Authors: Aboul‐Nasr Osman T. , Huang Robert Y. M.
Published: April 2003

The diffusion coefficient at zero concentration and the free volume parameters in Fujita's free volume theory were measured for benzene, hexane, and heptane in modified polyethylene films using an unsteady‐state absorption technique. Films were modified by gamma irradiation, solvent conditioning, and post‐ and preirradiation conditioning. Dc=0 was found to drop with irradiation, the drop being larger the larger the molecular size of the diffusing molecule. A relationship for the dependance of Dc=0 on the crosslink density is proposed. Solvent conditioning led to an increase in Dc=0 directly proportional to the swelling power of the conditioning agent and to the molecular size of the diffusant molecule. In most cases, combined treatment resulted in an increase in Dc=0, the extent of which was dependent upon the relative effect of the swellant and the irradiation dose. In all cases, postirradiation conditioning led to values of Dc=0 higher than those obtained by preirradiation conditioning. The fractional free volume of the polymer was found to decrease with irradiation, showing a marked drop at low doses when reaching a state where the dose was of small effect. Changes in f(0,T) with conditioning and with combined treatment followed the same general pattern as Dc=0. β(T) was unaffected by any kind of treatment studied. Bd changed in practically the same manner as f(0,T) but in the opposite direction. A method is proposed for the optimum choice of a membrane modification procedure based on solubility and diffusivity results.
Size distribution of suspension‐polymerized unsaturated polyester beads
Authors: Narkis M.
Published: April 2003

Thermosetting polyester beads in the size range of 200 to 2000 μm were prepared in a PVAl stabilized suspension polymerization system from a commercial unsaturated polyester resin. Bead size distribution curves were determined and the average surface mean diameter Dm was calculated. Agitation speed, resin volume fraction in the reaction medium and PVAl concentration were varied and their effect on Dm was studied.
The analysis of rigid polyurethanes by chemical ionization mass spectrometry
Authors: Mumford N. A. , Chatfield D. A. , Einhorn I. N.
Published: April 2003

Methods for the elucidation of the chemical components of polyurethane foams are described. Foam samples of 50 mg were hydrolyzed in aqueous base and the resulting mixture of polyols and polyamines was analyzed by chemical ionization mass spectrometry (CI‐MS) and high‐pressure liquid chromatography (HPLC). The aromatic polyamines, which were separated by HPLC, produced few fragment ions under methane chemical ionization and were identified without difficulty. Each propoxylated homolog in the mixture of polyols was detected by CI‐MS techniques, and approximate molecular weight profiles are presented for each polyol studied. Chemical ionization spectra are listed for samples of standard polyols and of base‐hydrolyzed isocyanates. The hydrolysis products from urethane foam formulations were easily related to the standard compounds via CI‐MS. These methods should be applicable to polymeric materials containing urethane, urea, and ester link‐ages.
Grafting onto polyester fibers. II. Kinetics of grafting of acrylic acid, acrylonitrile, and vinyl acetate onto polyester fibers
Authors: Rao K. N. , Rao M. H. , Lokhande H. T. , Mody N. R. , Jog A. G.
Published: April 2003

The kinetics of grafting of acrylonitrile, acrylic acid, and vinyl acetate onto polyester fiber by catalytic initiation and radiation were studied. The energy of activation determined for acrylic acid grafting by the catalytic method was 10.7 kcal/mole and that for vinyl acetate grafting by the radiation method, 11.7 kcal/mole. In the case of acrylonitrile grafting by the catalytic method, the rate of grafting decreased with increase in temperature of grafting, showing the differential behavior of the precipitating type of polymer from that of homogeneous polymerization.
A study of sequence distribution of chloroprene and methyl methacrylate copolymers by 1H‐NMR
Authors: Okada Tadashi , Otsuru Masaaki
Published: April 2003

The 1H‐NMR spectra of poly(chloroprene‐methyl methacrylate) which was copolymerized with ethylaluminum dichloride (EtAlCl2) and vanadyl trichloride (VOCl3) were measured with the radical copolymers. The split signals of the OCH3 and α‐CH3 protons in the spectra were assigned to triads and pentads with methyl methacrylate as a center, respectively, and the fomer concentrations were in reasonable agreement with the latter concentrations in triads. Moreover, it was found that the α‐CH3 signal was split into peaks of different tacticity when the mole fractional ratio of methyl methacrylate (MMA) to chloroprene (CP) in the copolymer was approximately 3.0 or greater.
The influence of reactor conditions, antioxidant, and processing on the degradation of LDPE
Authors: Bergström C. , Brenner J. , Stenius P.
Published: April 2003

The extrusion of LDPE was simulated under well‐defined conditions by using a Brabender Plasti‐Corder. The grades tested according to gel formation were synthesized in a modified autoclave reactor. With the basic synthesis conditions the same two different reactor pressures were used and at both pressures, two melt index levels were maintained. The two grades with the lower reactor pressure were synthesized under two‐phase conditions. With the Brabender Plasti‐Corder the influence of melt temperature, mixing efficiency, mixing time, as well as BHT content was investigated. By studying the torque, the gel content, and the change in molecular weight distribution, the following results were obtained. LDPE synthesized under two‐phase conditions is sensitive to gel formation, and this can be more easily seen when the melt index is low. Gel formation was also found to increase with increasing melt temperature and increasing mixing time. The effect of mixing efficiency was minor. When the polymer contained BHT, there was a decrease in torque drop as well as gel content. The Brabender curves had peaks indicating molecular enlargement; and when using more BHT, these peaks developed at a later moment. From the GPC data it can be seen that combination of secondary radicals is typical for the two‐phase grades, whereas stripping of LCB predominates for the single‐phase grades.
Thermal decomposition of anionic and emulsion polymerized polystyrenes
Authors: Rudin Alfred , Samanta Madhu C. , Reilly Park M.
Published: April 2003

The thermogravimetric behavior of anionic and emulsion polymerized polystyrenes was investigated in nitrogen at a heating rate of 18°C/min. Kinetic data were obtained by least squares analyses of experimental points obtained by differentiating primary thermograms. Degradation was generally zero order for about the first 25% of the reaction and first order thereafter. No molecular weight effects were observed for anionic polystyrenes with M ≥ 1 × 105. Anionic and emulsion polystyrenes differed significantly in thermal stability. Degradation of emulsion polymers proceeded more slowly and with higher activation energies in both the zero‐ and first‐order regions. Activation energies for anionic polystyrenes were 28 and 44 kcal/mole in the zero‐ and first‐order domains while the corresponding values for emulsion polymers were 36 and 60.5 kcal/mole, respectively. No tacticity differences were detected in 220 MHz NMR spectra. The differences in thermal stability are attributed to differences in end groups in the two polymer types.
Calibration of vapor pressure osmometers for molecular weight measurement
Authors: Burge David E.
Published: April 2003

Experimental molecular weights in the range 200 to 100,000 Daltons have been determined by vapor pressure osmometry using three different solvents. For all values in excess of 10,000, molecular weights were also determined by membrane osmometry. The general agreement found for molecular weights determined under a variety of conditions, leads to the conclusion that values as high as 100,000 Daltons can be determined by at least one type of vapor pressure osmometer when it is calibrated with a material of 200 Daltons. Thermistor self‐heating and diffusion in the liquid phase are shown to be unimportant for this particular instrument.
Allyl esters of crambe‐derived long‐chain fatty acids and their polymers
Authors: Chang Shu‐Pei , Miwa Thomas K.
Published: April 2003

Allyl esters of erucic, brassidic, behenic, oleo‐erucic, and stearo‐behenic acids, prepared by refluxing benzene solutions of the acids with excess allyl alcohol in the presence of p‐toluenesulfonic acid monohydrate, polymerize smoothly in the presence of 5 wt. % t‐butyl perbenzoate at 120°C for 24 hr. Polymerization of the unsaturated acid esters involves a large portion (ca. 84%) of allylic and a small portion (ca. 26%) of ethylenic bonds. The products, saturated and unsaturated, have a degree of polymerization between 6 and 10 and are soluble in typical polymer solvents. Crystallinity, judged by thermal analysis, decreased with increased cis unsaturation. The oligomers melted between −30°C and 59°C and started decomposing at 200°C.
Ionically crosslinked poly(acrylic acid) membranes. I. Wet technique
Authors: Habert A. Claudio , Huang Roberty Y. M. , Burns Charles M.
Published: April 2003

A study has been made of the ionic crosslinking of poly(acrylic acid) membranes for possible applications in dialysis and reverse osmosis. The technique consists of casting a film of poly(acrylic acid) neutralized with sodium hydroxide, followed by immersion in appropriate metal salts (aluminium, zinc, and chromium salts). A qualitative rate model has been developed to guide this synthesis. Since both metal cations and protons in solution compete for the carboxylic acid sites, acid–base properties of the metal and polycarboxylic acid appear to be important for successful membrane formation. The use of a nonsolvent for the polymer in the crosslinking solution was tested and found to give improved membranes under some conditions. The nonsolvents tested were methanol, acetone, benzene, and dimethylformamide, dimethylformamide being the most successful. Crosslinking agents such as the Zn2+ and Cr3+ salts were tried but were not as successful as the Al3+ salts. A series of membranes was synthesized in aluminium/dimethylformamide crosslinking baths under various conditions in order to determine suitable procedures for preparation of membranes.
Simultaneous interpenetrating networks based on castor oil elastomers and polystyrene. V. Behavioral trends and analysis
Authors: Devia N. , Manson J. A. , Sperling L. H. , Conde A.
Published: April 2003

The morphology and/or mechanical properties of simultaneous interpenetrating networks, SINs, based on castor oil elastomers and crosslinked polystyrene, were studied by electron microscopy, stress–strain analysis, and/or Izod impact tests. Several synthetic details were changed systematically and the concomitant changes in morphology or particular properties observed. The toughness of elastomer SINs increased with decreasing domain size of the polystyrene dispersed phase. The use of a prepolymer for the elastomer network synthesis promotes the formation of larger polystyrene domains. The impact resistance of the SINs increased with the total elastomer content. Properly crosslinked and postcured compositions developed impact energies of about 60–70 J/m. SINs based on castor oil‐derived elastomers and crosslinked polystyrenes form prototype engineering materials which already compared satisfactorily to commercial polymers in terms of mechanical behavior.
Influence of monomer preemulsification on formation of particles from monomer drops in emulsion polymerization
Authors: Durbin D. P. , El‐Aasser M. S. , Poehlein G. W. , Vanderhoff J. W.
Published: April 2003

Evidence was obtained supporting the theory that monomer droplets can become a locus of initiation and propagation in emulsion polymerization. This was done by reducing the size of the monomer droplets prior to initiation of polymerization using different preemulsification techniques for a typical latex recipe containing a common anionic surfactant. Monomer droplet size reduction caused an increase in the total surface area of the monomer droplets and thereby increased the competitiveness of these droplets for capturing active free radicals which are generated in the aqueous phase. As the total surface area of the monomer droplets was increased by preemulsification, a corresponding increase in the number of large particles formed by polymerization of these monomer droplets was experimentally measured. This work shows that monomer droplets are a locus of emulsion polymerization. However, the importance of monomer droplet polymerization is limited by their total surface area because of the competition for free radicals with other surfaces and/or particle nucleation processes. The results offer a basis for explaining why broad, and sometimes bimodal, particle size distributions are obtained in some commercial processes where the reactants are preemulsified prior to being charged into a reaction vessel.
Structure and morphology of poly(tetrafluoroethylene)‐poly(N‐vinylpyrrolidone) copolymer membranes
Authors: Morel G. , Jozefonvicz J.
Published: April 2003

The structure and morphology of poly(tetrafluoroethylene)‐poly(N‐vinylpyrrolidone) (PTFE‐PVP) copolymer membranes prepared by direct radiation grafting were studied by using differential scanning calorimetry, x‐ray diffraction, and scanning electron microscopy. The granulometry of the base emulsion used in PTFE film forming did not have any influence on the mechanism of radiochemical grafting. Moreover, it is proposed that the size of base grains induces morphologies of grafted membranes which differ markedly from each other. The results are analyzed on the assumption that grafted chains of PVP are formed between the base grains of PTFE and gradually move inward toward the crystalline zones. For a given grafting ratio, the space of distribution of grafted chains inside the PTFE matrix depends on the size of PTFE base grains. A correlation between morphologies of membranes and water permeability of copolymer membranes is indicated.
Ionic crosslinking of carboxyl‐terminated liquid rubbers with metal oxides
Authors: Matsuda Hideaki , Minoura Yuji
Published: April 2003

Ionic crosslinking of carboxyl‐terminated liquid rubbers with metal oxides and metal carbonates, mainly with the former, were investigated. The liquid rubbers used were a polymer of butadiene (Hycar CTB 2000X162) and a copolymer of butadiene–acrylonitrile (Hycar CTBN 1300X8). The CTBN ionically crosslinked rubbers obtained showed higher tensile strength than the CTB series, due to the polarity effect of the nitrile groups. The ionic rubbers cured with MgO and CaO were studied in detail, and it was found that their tensile strength increased markedly with increase in the metal oxides used, and in addition white carbon and carbon black showed remarkable reinforcing effects. The properties such as tensile strength, elongation, Shore A hardness, and melt index are influenced by humidity. It is characteristic of these ionically crosslinked rubbers that they can be successfully reprocessed.
Synthesis and characterization of poly(phenylene sulfide), poly(2‐methylphenylene sulfide), and poly(2,6‐dimethylphenylene sulfide)
Authors: Port A. B. , Still R. H.
Published: April 2003

A facile synthesis of poly(phenylene sulfide) (PPS), poly(2‐methylphenylene sulfide) (PMPS), and poly(2,6‐dimethylphenylene sulfide) (PDMPS) from the respective copper (I) bromothiophenoxides is described. Polymerization was effected in a 10:1 quinoline:pyridine mixture at atmospheric pressure and conditions optimized for the preparation of high‐molecular‐weight materials. The preparation of PPS in pyridine under pressure at 250°C has been investigated for comparative purposes. Yields and the properties of materials produced by solution polymerization are comparable to or better than those produced in the autoclave reaction. Properties have been investigated as a function of reaction time and molecular weight, and the deficiencies of the molecular‐weight assessment methods are discussed. PMPS and PDMPS have been similarly studied and their properties evaluated. The use of heat of crystallization determinations for molecular‐weight studies on PPS are described and critically evaluated.
Heavy metal ion adsorbents having thioamide groups
Authors: Kaeriyama Kyoji
Published: April 2003

Polyhydrazides are prepared by condensation of cyanuric chloride with dihydrazides of dibasic carboxylic acids and are sulfurized with phosphorus pentasulfide. Copolymers of acrylamide and dimethylacrylamide with divinylbenzene are also sulfurized with phosphorus pentasulfide. The sulfurized polymers adsorb mercuric ion. In order to incorporate thiocarbamide groups into a polymer matrix, methylolthioureas are condensed with polyethylenimine. The reactions are carried out in the solid state or in aqueous solution. In the former, water is distilled off from the solidified mixture of the reactants; in the latter, methylothiourea and polyethylenimine are allowed to react in the presence of sulfuric acid. The products are good mercuric ion adsorbents.