bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of porosity in polyethylenimine adsorption onto cellulosic fibers
Authors: Alince B. 
Published: April 2003

AbstractThe total adsorption of a given polyethylenimine on pulp fibers, the porosity of which was altered by different drying conditions, was determined and compared with the available internal surface of the fibers. Since polymer adsorption takes place in an aqueous environment, the pore volume and the internal surface of pores as a function of their size were determined from a first benzene desorption isotherm, measured on fibers in which water was replaced by benzene to preserve their swollen structure. The total adsorption of a given polyethylenimine was found to be in a direct relation to the internal surface available in pores larger than a certain size, regardless of the total porosity. Consequently, it is concluded that the adsorption capacity is determined by the accessible surface.
Blends of nylon 6 with a polyethylene functionalized by photooxidation
Authors: Curto D. , Valenza A. , La Mantia F. P. 
Published: April 2003

AbstractAn easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt‐blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved by chemical modification of the polyolefines chains. This step could be very expensive.
Competition between cure and thermal degradation in a high Tg epoxy system: Effect of time and temperature of isothermal cure on the glass transition temperature
Authors: Pang K. P. , Gillham J. K. 
Published: April 2003

AbstractThe isothermal cure of a diglycidyl ether of bisphenol A with a tetrafunctional aromatic diamine has been studied in an attempt to achieve full cure (maximum glass transition temperature, Tg∞, ca. 170°C). Since high temperatures of cure are necessary for high Tg∞ systems (because of low reaction rates after vitrification), cure and thermal degradation reactions often compete. In this work Tg is used as a direct measure of conversion. An approach leading to a series of iso‐Tg contours in a temperature vs. time transformation (TTT) diagram, which can be used to design time‐temperature cure paths leading to particular values of Tg, is discussed.
Molecular structure, melting behavior, and crystallinity of 1‐octene‐based very low density polyethylenes (VLDPEs) as studied by fractionation and heat capacity measurements with DSC
Authors: Mathot V. B. F. , Pijpers M. F. J. 
Published: April 2003

AbstractHeat capacity measurements with DSC on 1‐octene‐based very low density polyethylenes (VLDPEs), with densities from 888 to 907 kg/m3, show crystallization between 120 and −60°C and melting between −60 and 130°C. Under the assumption that hardly any octene groups are present in the crystal lattice, the experimental heat capacity values were compared with reference values for purely amorphous and purely crystalline linear polyethylene on the basis of a two‐phase model. The enthalpy‐based weight crystallinity data as a function of temperature show that the crystallinities at −60°C are about 40% higher than those at room temperature, which vary from 25 to 40% and are in good agreement with volume‐based weight crystallinities. The crystallization and melting curves show several peaks. Fractionations by the crystallization/dissolution method and the direct extraction method show that this is due to intermolecular heterogeneity of comonomer incorporation and that VLDPE is a reactor blend of molecules ranging from the uncrystallizable and poorly crystallizable type to the HDPE type.
Electroinitiated polymerization of commercial divinylbenzene in acetonitrile medium
Authors: Mahata Prafulla Kumar , Nayak Bimbadhar 
Published: April 2003

AbstractThe electroinitiated polymerization of commerical divinylbenzene (DVB) containing p‐ and m‐DVB and p‐ and m‐ethylvinylbenzene (EVB) and traces of diethylbenzene has been studied in acetonitrile medium with an added electrolyte, namely, tetrabutylammonium fluoroborate (TBAFB). A white partially crosslinked polymer is formed only after the passage of an electrical current. The dependence of yields on parameters such as current strength, temperature, time of electrolysis, and stirring of the reaction mixture has been determined. A detailed IR analysis of the polymeric product has been made and the linear polymeric product is identified as poly(p‐DVB‐co‐m‐DVB‐co‐p‐EVB‐co‐m‐EVB). The electropolymer is thermally stable up to 645 K as found by its DTA, TG, and DTG studies and possesses partial crystallinity as indicated by the X‐ray diffraction experiments. Experiments conducted with a split cell indicated the formation of the polymer in the anode compartment; hence the polymerization mechanism appears to be cationic in nature.
Internal stress of epoxy resin modified with acrylic polymers produced by in situ UV radiation polymerization
Authors: Nakamura Yoshinobu , Yamaguchi Miho , Kitayama Akiko , Iko Kazuo , Okubo Masayoshi , Matsumoto Tsunetaka 
Published: April 2003

AbstractA cured epoxy resin is modified with polybutyl acrylate (A) and polyethyl acrylate (B) produced by in situ ultraviolet radiation polymerizations of their corresponding monomers in the epoxy resin, respectively, to reduce the internal stress. In the A system, a heterogeneous structure with submicron domains was formed. In the B system, however, the B mixed well with the epoxy matrix. In both systems, the internal stress was decreased by the modification. The glass transition temperature of the epoxy matrix decreased in the B system more than in the A system. The A‐modified resin was superior to the B‐modified resin in reducing the internal stress without decreasing the thermal resistance of epoxy resin.
Mechanism of persulfate decomposition in aqueous solution at 50°C in the presence of vinyl acetate and nitrogen
Authors: Sarkar Swati , Adhikari Mukti Sadhan , Banerjee Monoranjan , Konar Ranajit Singha 
Published: April 2003

AbstractThe rate of the thermal decomposition of potassium persulfate has been studied in an unbuffered aqueous solution at 50°C in nitrogen atmosphere in the presence of vinyl acetate (VA) monomer (M). It has been found that the initial rate of persulfate decomposition may be written as

in the concentration range of persulfate (1.85 × 10−2–1.85 × 10−3 m/dm3) and VA (0.054–0.27 m/dm3). The pH of the aqueous solution of persulfate was found to decrease continuously at 50°C, but there was no measurable change of pH of the aqueous solution containing persulfate and VA at 50°C in the presence of nitrogen at the early stages of the reaction. VA, methyl acetate, and ethyl acetate have been found to undergo very slow hydrolysis in aqueous solution at 50°C. The partition coefficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 21 ± 2 in the presence and absence of electrolytes (K2SO4, 10−4–10−3 m/dm3) by the bromometric estimation of the monomer present in the aqueous phase containing known amounts of monomer [1.80–2.20%, w/v] and freshly prepared polymer (0.3–0.5 g/100 mL). Above 10−2 (m/dm3) persulfate, the polymer obtained was found to be insoluble in common solvents, viz., acetone, benzene, etc. Highly purified sodium dodecyl sulfate (0.5–5.0 × 10−3 m/dm3) had no measurable effect on the rate of persulfate decomposition.
Radiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene–tetrafluoroethylene) film by preirradiation method. III. Properties of anion‐exchange membrane obtained by chloromethylation and quaternization of the grafted film
Authors: Momose Takashi , Kitazumi Tomoko , Ishigaki Isao , Okamoto Jiro 
Published: April 2003

AbstractA study was made of certain properties of the anion‐exchange membranes obtained by the preirradiation grafting of α,β,β‐trifluorostyrene (TFS) onto poly(ethylene–tetrafluoroethylene) (ETFE), followed by chloromethylation and quaternization of the grafted film. Swelling, water uptake, electric conductivity, and transport number of the membranes were measured as a function of ion‐exchange capacity. Thermal and chemical stability were also investigated. These properties were found to be mainly dependent on ion‐exchange capacity. The stable membrane properties were established due to a homogeneous ion‐exchange group distribution in the membrane, as confirmed by X‐ray microscopy analysis of the membrane cross sections. In addition, the membranes showed good electrochemical, thermal, and chemical properties, and were found to be acceptable for practical use as anion‐exchange membranes.
High‐strength poly(L‐lactide) fibers by a dry‐spinning/hot‐drawing process. II. Influence of the extrusion speed and winding speed on the dry‐spinning process
Authors: Postema A. R. , Luiten A. H. , Oostra H. , Pennings A. J. 
Published: April 2003

AbstractThis paper is concerned with the influences of the extrusion speed and the winding speed during dry spinning of 4 wt % solutions of poly(L‐lactide) (PLLA) in mixtures of chloroform and toluene, on the ultimate fiber tenacities after hot drawing. It was found that high‐strength PLLA fibers (1.5 GPa) can be produced at high spinning rates (> 180 m/min) if rupturing of the entanglement network and oriented crystallization during spinning is suppressed. This could be accomplished by avoiding spinline stretching and applying low elongational deformation rates in the spinneret during spinning.
Reversible crosslinking in epoxy resins. II. New approaches
Authors: Sastri V. R. , Tesoro G. C. 
Published: April 2003

AbstractEpoxy resins of varying epoxy equivalent weight were crosslinked with 4,4*‐dithiodianiline (DTDA) at a 2/1 mole ratio. Resin of equivalent weight 190 (Epon 828) was cured with DTDA at mole ratios varying from 2/1 to 1.25/1. Properties of cured resins were evaluated and their reduction was investigated. Under the conditions used, reduction to the point of complete solubilization was possible providing crosslink density did not exceed a threshold value tentatively established as Mc = 400 −; 500. Recurring of reduced resins was accomplished by oxidation and by reaction of thiol groups with polyfunctional reagents, including bismaleimides and polyepoxides.
Coatings and surface modification by methane plasma polymerization
Authors: Ho Chung‐Peng , Yasuda H. 
Published: April 2003

AbstractPolymers formed from plasma‐polymerized methane were employed to modify the surface properties of silicone rubber membrane. Polymers were evaluated based on the energy input parameter W/FM, where W is the discharge power, F is the monomer flow rate, and M is the molecular weight of the monomer. Dealing with the characteristics of plasma polymerization and the deposited polymer film, the effect of pumping rate on deposition rate and the coating thickness, surface energy, and gas permeabilities of methane‐plasma‐polymer‐coated silicone rubber membrane were investigated in three plasma regions. Because more reactive species are expelled at high pumping rates, the monomer‐deficient region is reached at lower W/FM in the high pumping rate system than that in the low pumping rate system. The composite parameter W/FM had a strong influence on coating thickness, gas permeability, surface energy, and the polar component of the surface energy but little effect on its dispersion component. Examination of gas permeabilities indicated that coating thickness was another important controlling factor on the properties of plasma polymer.
Bismaleimide and bisazomethine high temperature polymers
Authors: Chattha M. S. , Siegl W. O. 
Published: April 2003

AbstractConjugated aromatic bisazomethine, resulting from the reaction of terephthaldicarboxaldehyde and aniline, has been found to react with bismaleimidodiphenylmethane to provide polymeric compositions with glass transition temperature higher than 300°C. These two materials form a low viscosity melt at ca. 150°C and the melt shows only a small viscosity increase when maintained at 120°C over a period of 8 h. Differential scanning calorimetry (DSC) of this composition shows that upon heating above 200°C, it cures rapidly to produce a thermally stable polymer. Thermal mechanical analysis (TMA) of the cured composition does not detect any softening up to 350°C. In the thermal gravimetric analysis (TGA), no weight loss is observed up to 400°C in air and the material leaves a rather large amount of residue (ca. 60%) even up to 600°C. Dynamic mechanical thermal analysis (DMTA) shows that the polymer maintains its high modulus with increasing temperature up to 250°C.
Copolymer of ketonic resin–polyacrylonitrile
Authors: Akar Ahmet , Gali̇oǧlu Oya , Göçmen Ayten , Sarac A. Sezai̇ 
Published: April 2003

AbstractThe polymerization of acrylonitrile in the presence of Ce(IV) salts and ketonic resin such as methyl ethyl ketone/formaldehyde and cyclohexanone/formaldehyde resin was investigated. Block copolymer of ketonic resin–polyacrylonitrile was produced. The effect of Ce(IV) concentration, temperature, time, and monomer concentration on the yield and molecular weight was studied. Maximum yield was obtained at 50°C and ceric ammonium nitrate concentration of 0.033 mol/L.
X‐ray diffraction studies in resins: Effect of entanglements and chain structure
Authors: Swarup S. , Nigam A. N. 
Published: April 2003

AbstractX‐ray diffraction halo of alkyd, amino, and epoxy resins were recorded. The effective d obtained from them was used to estimate certain physical parameters like cross‐sectional area, number of carbon atoms per chain, and stiffness parameters from the empirical curves of Boyer and Miller. Amino resin was found to behave differently than the rest of the resins which have a benzene ring in their backbone. These ideas find a confirmation from the ultrasonic and dielectric measurements performed on these very samples.
High performance size exclusion chromatography of poly(organo)phosphazenes
Authors: De Jaeger R. , Lecacheux D. , Potin Ph. 
Published: April 2003

AbstractThe determination of the molecular weights of polyorganophosphazenes can only be achieved with great care. The nature of the substituents, the proportion of residual chlorine atoms after substitution, and also any traces of hydrolysis can considerably modify the behavior of these polymers in solution and thus lead to erroneous results. In our current research we have been developing a characterization method based on steric exclusion chromatography, coupled with a light scattering detector. We have used columns with styrene–divinylbenzene organic micropacking as the stationary phase and THF with added LiBr (0.1 mol/L) as the eluent. This method has enabled us to establish accurate correlations between molecular weight, hydrodynamic volume, and viscosimetric measurements for polyaryloxyphosphazenes of varying structures and origins. The method also provides results which agree very well with the variables for the preparation of polyphosphazenes, which is based on polycondensation of P‐trichloro‐N‐dichlorophosphoryl monophosphazene Cl3P = NP(O)Cl2. Finally this method allows us to show that, despite their mineral backbone, these polymers obey Benoit's universal calibration concept.
Studies on the temperature dependence of extinction oxygen index values for cellulosic fabrics: III. Comparison with limiting oxygen index for commercial flame‐retarded cotton
Authors: Horrocks A. R. , Price D. , Tunc M. 
Published: April 2003

AbstractLimiting oxygen index values of single and multilayer Proban CC‐ and Pyrovatex CP‐flame retardant finished cotton fabrics having a variety of area densities were determined as a function of igniter application time and temperatures up to 200°C. Except for the lightweight (140 g m−3) Proban CC‐treated fabrics, LOI, like comparable extinction oxygen index (EOI) values, increased as ignition times were increased from 2 to 10 s. Extrapolation to zero ignition time enabled [LOI]0 values to be determined at each temperature, which, for a given flame retardant, increased linearly with area density of mono‐ and multilayered fabric combinations. Comparison with earlier extinction oxygen index results showed that this [LOI]0 vs. area density dependence had significantly lower correlation than that for [EOI]0. These ṕoor former correlations further substantiated the claims that the EOI concept offers a more effective means of quantifying textile fabric flammability. Analysis of the linear relationships enabled intrinsic limiting oxygen index, L0, and area density‐dependent, L1, terms to be determined. Like conventional LOI values, L0, values also reduce significantly at elevated temperatures.
Surfactant effects in the emulsion polymerization of vinyl acetate
Authors: Lee C. H. , Mallinson R. G. 
Published: April 2003

AbstractContinuous vinyl acetate emulsion polymerization was carried out by using a mixed surfactant system of “Aerosol” OT (AOT) and sodium dodecyl sulfate (SDS). It is well known that the AOT reduces surface tension considerably and has stronger monomer solubilization power than SDS. In this work, particular attention is given to observe the effects of the mixed surfactant on the molecular weights and polydispersities. In comparison with experiments using only SDS, the particle size appears similar, in the range of 190–280 nm. The conversion increased substantially to the 70% range from the 50% level observed with only SDS. All experiments were conducted at 60°C with a mean residence time of 30 min. The total surfactant concentration was maintained at 0.03 mol/L water for all experiments. It was found that once some AOT was included in the surfactant, the behavior was very similar to that observed with only AOT. The number average molecular weights were found to decrease substantially while the polydispersity increases dramatically to about 12. It is believed that AOT may act as a significant chain transfer agent in the polymerization.
Studies on the aging process of a highly condensed resol resin
Authors: Latocha Czesław , Balcerowiak Wojciech 
Published: April 2003

AbstractThe nature of the structure changes of a highly condensed resol resin during its aqueous solution storage was considered. To this end, the curing process of the resin was investigated by means of DTA and its structure was analyzed by means of NMR. The hypothesis relative to stability of the hemiformal bonds was made.
Acoustic properties of transparent polysiloxanes
Authors: Bosc D. , Mauguen P. 
Published: April 2003

AbstractIt is well known that the glass transition temperature of polydimethylsiloxane elastomers lies close to −120°C. According to the time temperature superposition principle, we may state that these materials keep their caoutchoutic state when they are excited by a 10 MHz mechanical wave. This is an important point particularly for acoustooptic applications. Thus, in the range of 1–10 MHz, materials with good efficiency are missed; low acoustic wave velocity is needed to give the best conditions, which means to be in a caoutchoutic state for polymeric materials. With this work, we show that three polysiloxanes, polymerized under different conditions, do not fulfill this condition. Thus the shift of Tg with frequency is very large and these polymers reach their glassy state at relatively low frequency. The acoustic wave velocity is in good agreement with mechanical predictions provided by master curves of the Young modulus.
The effect of agitation, purge time, and nonsimultaneous addition of acid and initiator on xanthated cellulose–polystyrene graft copolymer
Authors: Graczyk Tomasz , Hornof Vladimir 
Published: April 2003

AbstractConversion to polymer and molecular weight of grafted copolymer in the graft copolymerization of styrene initiated by the xanthate method is strongly dependent on reaction conditions even in the range of agitation speed when the effect of diffusion of monomer is neglected. When sulfuric acid and hydrogen peroxide are added simultaneously after 15 min of purging with nitrogen 99.99%, conversion and molecular weight vary little with stirring speed. Both parameters decrease with increasing stirring speed when H2 SO4 is added 1 min earlier than H2O2 and nitrogen is purged 15 min before starting the reaction. Both parameters increase when H2SO4 and H2O2 are added simultaneously after 60 min of purging with nitrogen. Highest conversion is observed when both reagents are added after 15 min of purging with nitrogen. Molecular weight is the highest at 310 rpm when H2SO4 is added 1 min earlier than H2O2, and at 1100 rpm when nitrogen is purged for 60 min.
New biodegradable films from exploded wood solutions
Authors: Paillet M. , Peguy A. 
Published: April 2003

AbstractIn this paper experimental results obtained with the exploded wood/tertiary amine oxide system are presented. The use of particular conditions leads to the formation of new biodegradable films. These films may have a natural color from brown to black. The mechanical properties are studied and a comparison with a black commerical synthetic film is made. The structure of the films is made. The structure of the films is studied as well as the role of lignin as an antioxidant.
Graft copolymerization onto wool fibers: Grafting of acrylamide onto wool fibers initiated by potassium monopersulphate/Fe (II) redox system
Authors: Giri Gitisudha , Sahoo Prafulla K. , Samal Rajani K. 
Published: April 2003

AbstractGraft copolymerization of acrylamide (AM) onto wool fibers has been studied in aqueous solution with a new redox initiating system, KHSO5/Fe(II). For estimation of comparative influence of salts and selection of reaction medium, grafting has also been studied in the presence of a multitude of inorganic salts and some organic solvents. It was observed that the graft percentage was influenced by the reaction time, temperature, concentration of monomer initiator, FeSO4, and the base polymer. A maximum graft percentage of 120.5% was obtained at 35°C with the concentration of AM (0.8M), KHSO5 (0.0195M) and Fe (II) (2.5 X 10‐3 M) for reaction time of 2 h. From the experimental results, a suitable reaction mechanism for graft initiation and termination has been suggested. The water retention of the grafts and their behavior towards mineral acids and alkalis have been tested. The tensile strength and the thermal stability of the grafts have also been determined and compared with the base.
Yield and fracture mechanisms in ABS
Authors: Chen C. C. , Sauer J. A. 
Published: April 2003

AbstractThe deformation and fracture characteristics of ABS have been investigated under tension, compression, and tension‐compression fatigue cycling. The behavior of the rubber‐modified polymer is compared with that of unmodified styrene‐acrylonitrile, copolymer. The dispersed rubber particles in ABC cause extensive plastic deformation of the matrix material, markedly reduce the compressive yield stress, and, under tensile loading, cause yielding rather than early fracture. Under alternating stress conditions crazes occur sooner and lead to earlier craze breakdown, crack development, and reduced lifetime to fracture. The influence of rate of loading has been studied under applied tension and under fatigue cycling. The tensile yield stress varies linearly with the log of the strain rate in accord with the Eyring rate equation and, from the measured slope, the activation volume is estimated to be 2.2 nm3. The time to fatigue fracture reduces significantly with increasing frequency while cycles to fracture increase at a modest rate. Fatigue failure in ABS is not a cycle‐dependent process, nor is it in accord with a damage accumulation model, but it more nearly resembles the former. The influence of a dispersed rubber phase, and of loading rate, on fracture surface morphology is discussed.