bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractPolymerization 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

AbstractThe 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

AbstractThe 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

AbstractBlends 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

AbstractAfter 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

AbstractThe 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

AbstractThermosetting 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

AbstractMethods 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractExperimental 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

AbstractAllyl 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

AbstractA 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

AbstractThe 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

AbstractEvidence 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

AbstractThe 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

AbstractIonic 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

AbstractA 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

AbstractPolyhydrazides 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.
Graft copolymerization of lignosulfonate and styrene
Authors: Chen R. , Kokta B. V. , Valade J. L. 
Published: April 2003

AbstractA study was made of the graft copolymerization of calcium lignosulfonate with styrene. Heterogenous copolymerization were carried out with methanol as swelling medium, using ferrous ion as catalyst, and ozone and/or hydrogen peroxide as initiator. When using peroxide alone as initiator, monomer conversion was low; after ozonization of lignosulfonates, monomer conversion increased considerably and the grafting efficiency, as well as degree of lignosulfonate grafted, was improved. At 55°C, a 10‐fold increase in conversion was observed for reactions with ozone‐pretreated lignosulfonates. The investigated factors that affected the graft copolymerization were: the amount of peroxide and ozone charged, the reaction temperature and the ratio of styrene/methanol.