bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new technique for the study of the kinetics of adsorption of polymers onto surfaces
Authors: Bajpai U. D. N. , Bajpai A. K. 
Published: April 2007

AbstractA new and simpler technique is described for the study of the kinetics of adsorption of poly(methylmethacrylale) (PPMA) on a glass surface at 30°C. The kinetics of adsorption were followed gravimetrically by knowing the amount of polymer adsorbed on glass balls at various time intervals. A simple kinetic model for rate of adsorption has been proposed, and from the scheme outlined various adsorption parameters such as adsorption coefficient, surface coverage and film thickness have been evaluated. From the available experimental data, adsorption isotherms have been drawn, and the effect of molecular weight of PMMA on adsorption behaviour has been studied.
Sorption and diffusion of aldehydes and ketones into elastomers
Authors: Aminabhavi Tejraj M. , Munnolli Ravindra S. 
Published: April 2007

AbstractThe results of the sorption and diffusion of aldehydes and ketones into structurally different elastomers such as ethylene propylene diene terpolymer, styrene butadiene rubber, nitrile butadiene rubber, neoprene and natural rubber are described in the temperature interval of 25‐60°C. From these data, the Arrhenius parameters for the processes of diffusion and permeation are determined. The activation parameters for the diffusion of ketones range from 10.29 to 49.62 kJ/mol and for aldehydes, from 13.18 to 50.42 kJ/mol; these values fall in the range expected for rubbery polymers well above their glass transition temperatures. Transport data are affected by the nature of the interacting solvent molecule rather than its size and also by the structural variations of the elastomers. For all the solvents, the polymers remained intact; however, natural rubber in the presence of benzaldehyde showed degradative reactions at higher temperatures. Volumetric expansions of the elastomers have been measured from the dimensional response in the presence of aggressive solvents.
Anionic synthesis and characterization of poly(4‐vinylpyridine)‐poly(dimethylsiloxane) block copolymers
Authors: Nugay N. , Küçükyavuz Z. , Küçükyavuz S. 
Published: April 2007

AbstractPoly(4‐vinylpyridine)‐b‐Poly(dimethylsiloxane) (P4VP‐b‐PDMS) copolymers have been synthesized by sequential anionic polymerization of 4VP and hexamethylcyclotrisiloxane at — 70°C. The initiator was sodium naphthenate. The solvent used during reactions has a very critical role in an homogeneous polymerization medium. A 1:1 pyridine/THF mixture was found to be the most suitable. The products were characterized by 1H‐NMR spectroscopy, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) techniques. All the results indicated the formation of 4‐vinylpyridine‐siloxane block copolymers. Also, the P4VP blocks can be completely quaternized with methyl iodide as indicated by 1H‐NMR and FTIR spectroscopies.
Adsorption and desorption dynamics of associative polymers onto particulates of titanium dioxide, alumina and quartz
Authors: Filippov Leonid K. , Silebi Cesar A. , El‐Aasser Mohamed S. 
Published: April 2007

AbstractThe authors have been investigating the adsorption and desorption dynamics of nonionic water soluble polymers on inorganic particles. The influence of the nature of polymers with and without associating hydrophobic end groups, the nature of adsorbents [TiO2, Al2O3 (neutral, acid and basic), and SiO2], polymer concentrations, linear velocity of fluids, and mutual diffusion of polymer molecules on the patterns of adsorption and desorption distribution of polymer concentrations are shown. The model polymer is a nonionic polyurethane polymer based on ethylene oxide. The polymer's structure is R‐O‐(DI‐PEO)6‐DI‐O‐R (R is C16H33, DI is isophorone diisocyanate, and PEO is CARBOWAXTM with a molecular weight of 8200). The phenomenological models of association and dissociation kinetics of associative polymers are suggested. The half‐lives of clusters into adsorption and desorption layers are estimated. It is shown that heats of desorption of associative polymers are dependent essentially on heats of dissociation of clusters.
Influence of a monomeric plasticizer on the water‐sorption behaviour of food‐grade plastics packaging materials
Authors: Kalaouzis Panagiotis J. , Demertzis Panagiotis G. 
Published: April 2007

AbstractThe interaction of water with poly(vinylchloride) and poly(vinylidene chloride‐vinylchloride) (p(VdC‐VC)) plasticized with different amounts of a monomeric plasticizer (dioctylphthalate) has been studied using inverse gas chromatography. The present work was focused on the effect of temperature and plasticizer content on the water sorption behaviour of these plastics packaging materials. Values for thermodynamic parameters such as Gibb's free energy (ΔGs), enthalpy (ΔHs), entropy (ΔSs) and activity coefficient (γ) corresponding to sorption of water by the polymers have been calculated using chromatographic retention data. It was found that the sorption of water vapours increases with increasing the amount of plasticizer and decreases with increasing temperature. The Van Deemter equation was found to be applicable to these systems and was used to determine diffusion coefficients and activation energies for diffusion. Diffusion coefficient values increase with increasing amounts of plasticizer and they also increase with increasing temperature; this latter increase is accompanied by a decrease in the activation energy for diffusion. Present results were also compared to our own previous data, using a polymeric plasticizer.
Radiation‐initiated graft copolymerization of acrylic acid and vinyl acetate onto LDPE films in two individual steps
Authors: El‐Sawy Naeem M. , Hegazy El‐Sayed A. , Rabie A. M. , Hamed A. , Miligy G. A. 
Published: April 2007

AbstractRadiation‐induced grafting of vinyl acetate (VAc) and acrylic acid (AAc) onto low‐density polyethylene (LDPE) films was carried out in two individual steps: initially, the polymer substrate was grafted either with VAc or AAc and the grafted film thus obtained was grafted with the other monomer. The graft copolymerization of AAc onto LDPE‐g‐PVAc films was enhanced when the content of PVAc is low. This is due to the high polarity and hydrophilicity of AAc. On the other hand, the grafting of VAc onto LDPE‐g‐PAAc films was restricted due to the difficulties of VAc diffusion through the crosslinked grafted chains of PAAc. The influence of inhibitor and monomer concentration on the degree of grafting was studied. The addition of 2wt% of Mohr's salt effectively reduced the homopolymerization of monomer during the irradiation process. The dependence of the grafting rate upon VAc concentration was found to be of 1.5 order. Some selected properties of the graft copolymers, swelling behaviour and electrical properties, were investigated.
Retarding behaviour of organic solvents in permanganate‐sulphite‐initiated polymerization of acrylamide
Authors: Bajpai U. D. N. , Bajpai A. K. , Jain A. 
Published: April 2007

AbstractRedox polymerization of acrylamide initiated by a new redox couple, potassium permanganate‐sodium sulphite, has been studied under atmospheric oxygen at 35 ± 0.2° C. The rate of polymerization has been found to vary with the half power of the redox components and the first power of the monomer concentration. The energy of activation has been calculated to be 8.29 kcal/(deg. mol.). The effect of various additives such as neutral salts and surface‐active agents has been studied qualitatively. The retarding effect of organic solvents on the rate of polymerization has also been studied both qualitatively and quantitatively. An interpretation of the observed results has been proposed.
Dipolar relaxation behaviour in poly(methyl methacrylate)/4‐nitroaniline solid solutions
Authors: Dionísio Madalena , Ramos Joaquim J. Moura , Williams Graham 
Published: April 2007

AbstractIn the present paper the dielectric properties of solid solutions of 4‐nitroaniline in a poly(methyl methacrylate) matrix have been measured in the frequency range 20‐106 Hz and the obtained data have been compared with those for pure poly(methyl methacrylate). It is shown that the presence of the solute has a strong influence on the relaxation process of the polymer and this is ascribed to the formation of hydrogen bonds between the amino group of the solute and acetate side groups of the polymer.
Gelatin renaturation and viscosity of dilute gelatin solutions
Authors: Horský Jiři , Švantner Jiří 
Published: April 2007

AbstractMechanical melting temperatures of gelatin gels determined by the ball‐drop method are decreased by several degrees if 0.5m potassium thiocyanate aqueous solution is used as solvent instead of pure water. In agreement with that, the growth with time of the viscosity of dilute gelatin solutions occurs at lower temperatures in 0.5m potassium thiocyanate. Surprisingly enough, the reduced specific viscosity after five hours at 5° C is lower in pure water. This is because the temperature dependence of this quantity in water is not monotonic, and the temperature 5° C is below that at which a distinct maximum is reached. No similar maximum has been reported so far for the temperature and time dependences of the extent of renaturation determined by optical techniques. The difference between the results of these two methods could be ascribed to the fact that the viscosity of solutions of partially renaturated gelatin is given not only by the fraction of monomer units in the helical conformation but also by the average length of created helices.
Redox polymerisation—kinetics of polymerisation of acrylamide initiated by the Mn3+‐citric acid redox system
Authors: Sailaja G. , Raju K. Mohana , Raju M. Subramanyam 
Published: April 2007

AbstractThe kinetics and mechanism of polymerisation of acrylamide initiated by manganese(III) acetate‐citric acid (CA) redox system in aqueous acetic acid and sulphuric acid medium were studied over the temperature range 30‐50° C. The overall rates of polymerisation (Rp), disappearance of manganic ion (—Rm), and degree of polymerisation (X̄n) were measured with variation in [monomer], [Mn3+], [CA], [H+], μ and temperature. The polymerisation is initiated by the organic free radical arising from the Mn3+‐CA reaction and the termination is by metal ions. The various rate parameters were evaluated and discussed.
Permeability of PHEMA membranes prepared by photoinitiation
Authors: Arica M. Yakup , Hasirci Vasif N. 
Published: April 2007

AbstractPoly(2‐hydroxyethyl methacrylate) membranes were prepared in aqueous media with different ions and ionic strengths. The enzyme glucose oxidase was incorporated into some of these membranes. It was found that membrane water contents and ionic strengths have a linear relationship as long as the salt is not changed. When the salt was varied, only a relationship between salt concentration and water content could be observed. The membrane permeabilities were all found to be of the same order (10−8cm2s−1) but the membranes were slightly more permeable to chromate ions than glucose. Incorporation of enzyme distinctly increased the water content of the membrane and permeability to both solutes.
Free radical copolymerization in the presence of lewis acids—III: Alternating copolymerization of butyl acrylate and styrene in the presence of Al2Et3Cl3: Solvent effect
Authors: Yuan Yumin , Hao Xiaojuan , Jian Xigao , Xu Late Guojin 
Published: April 2007

AbstractPhoto‐initiated alternating copolymerization of butyl acrylate (BA) and styrene (St) in the presence of Al2Et3Cl3 was investigated in tetrachloroethylene (TCE) and toluene (TOL) solution. The results showed that copolymers with equimolar compositions were obtained over a wide range of reactant composition. The 13C nuclear magnetic resonance spectrum confirmed their alternating structure. Solvent could greatly affect kinetic behaviour, in TCE solution, the optimum rate of copolymerization was observed near equimolar monomer ratio; while in TOL solution the rate of copolymerization increased rapidly at lower [BA], tended to a constant rate at higher [BA] and increased slightly with increasing [St]. Electron spin resonance spectra indicated that the St radical was the only one to be detected. The effect of solvent as well as Lewis acid on alternating mechanism is also discussed.
Living functionalization of polymethacrylates by group transfer polymerization (GTP) using low ceiling temperature monomers
Authors: Quirk Roderic P. , Ren Jie 
Published: April 2007

AbstractA living functionalization method for group transfer polymerization (GTP) has been developed for poly(alkyl methacrylates) using the sterically hindered monomer, methyl‐2‐phenylpropenoate (MPHA). The end‐capping reactions of MPHA with living trimethylsilyl ketene acetal‐ended poly(methyl methacrylate) (PMMA) chain ends have been systematically studied and characterized by size exclusion chromatography, vapor pressure osmometry, ultraviolet‐visible, 1H and 13C nuclear magnetic resonance spectroscopy. Although oligomerization of MPHA is observed at ‐ 78° C, this is reversible and only monoaddition is observed at room temperature. In principle, various functional groups can be introduced into poly(alkyl methacrylates) via substituents on the aromatic ring of MPHA and related monomers. Amino‐functionalized PMMA was prepared by end‐capping reactions of living trimethylsilyl ketene acetal‐ended PMMA with methyl E‐3‐(2‐dimethylaminophenyl)‐2‐phenylacrylate.
Synthesis and characterisation of PP‐g‐butyl acrylate copolymers
Authors: Sathe Sachin N. , Srinivasarao G. S. , Devi Surekha 
Published: April 2007

AbstractButyl acrylate was grafted onto isotactic polypropylene using benzoyl peroxide as an initiator and toluene as a solvent. Effects of various parameters such as monomer and initiator concentration, reaction time and temperature on rates of polymerization, percentage grafting and grafting efficiency were studied. The extent of grafting achieved was 2.85%. The graft copolymers were characterized by IR, thermal, viscometric and contact‐angle studies. Improved thermal stability and decreased intrinsic viscosity and critical surface tension were observed for graft copolymers.
Epoxy/amine systems with monodisperse modifiers: thermodynamic analysis of the phase separation process taking the polymer polydispersity into account
Authors: Riccardi Carmen C. , Borrajo Julio 
Published: April 2007

AbstractPhase separation during polymerisation was studied by taking into account in the thermodynamic analysis the generated distribution of polymer species. A model system consisting of a diepoxide based on diglycidylether of bisphenol A, a diamine and castor oil as modifier was considered. One‐and two‐step polymerisation processes were simulated (in the two‐step process a first step was carried out with an epoxy excess up to a particular conversion, stoichiometry was balanced and the reaction continued in a second step). A thermodynamic analysis for a monodisperse modifier‐epoxy/amine system was performed taking the polydispersity of the polymer into account. It was shown that the cloud point conversion was decreased when the polymerisation was carried out in two steps. This effect was enhanced for lower stoichiometric ratios (higher epoxy excesses) and higher epoxy conversions in the first step. The dispersed phase became richer in low molecular weight species than the continuous one. In particular both monomers increased their concentration in the dispersed phase.
Effect of alkyl phthalate plasticizers on permeation of water vapour through PVC membranes
Authors: Shailaja D. , Yaseen M. 
Published: April 2007

AbstractPVC membranes plasticized with various concentrations of a di‐n‐alkylphthalate (methyl, ethyl, butyl or octyl) were studied for their water vapour permeation (WVP) properties. The rates of WVP through them were estimated under steady state by permeating the vapour through the membrane under the vapour pressure differential of approximately 100% to 0% relative humidities at 25°C. The rates of WVP were found to decrease with an increase in the size of the alkyl group of the phthalate but increased with its concentration. The maintenance of the property by the membranes being critical for their long‐term applications, the measurements were also repeated on the membranes aged for 250 days at intervals of 50 days. The WVP data indicate that membranes containing medium concentrations, i.e. 17.5‐20% of the plasticizers have better maintenance of the property during ageing and also in handling with good mechanical strength.
Kinetics of heterogeneous cyanoethylation of cellulose
Authors: Sefain Magdi Z. , Fadl Mohamed H. , Elwakil Nahla A. , Naoum Magdi M. 
Published: April 2007

AbstractHeterogeneous sodium and potassium hydroxide‐catalysed cyanoethylation of cotton linter and viscose grade wood pulp, investigated by analysing the nitrogen content of the cyanoethylated product as a function of the time of reaction, were shown to follow a first‐order rate equation. A new procedure was elaborated and a computer program was written to estimate the number of hydroxyl groups accessible for cyanoethylation per anhydroglucose unit and the specific rate constant from the rate curves. The effect of the type of alkali, its solution‐to‐cellulose ratio, temperature of reaction, mode of agitation, and the degree of polymerisation and packing density of cellulose fibres on the kinetics of cyanoethylation reaction were investigated.
Synthesis and characterisation of poly(amide‐hydrazides) containing many flexible spacer groups
Authors: Joseph K. Abraham , Srinivasan M. 
Published: April 2007

AbstractA set of 12 fully aromatic poly(amide‐hydrazides) were synthesised by the direct polycondensation phosphorylation reaction. Four different diamines containing preformed hydrazide units were condensed with three diacids in a mixture of N‐methylpyrrolidinone and pyridine. The polymers were obtained in 70‐85% yield and characterised by infrared and elemental analysis. The thermal stability, crystallinity, density and solubility were also measured.
Polymerisation control in casting of methylmethacrylate
Authors: Ramaseshan Vinod , Trivedi M. K. , Raghunathan T. S. 
Published: April 2007

AbstractThis paper reports a technique for the controlled bulk polymerisation of methylmethacrylate initiated by benzoyl peroxide. Due to the high exothermic nature of this polymerisation process, casting of thin sheets and profiles must generally be carried out at relatively low temperatures and over extended intervals of time at a constant rate. Curing profiles of 6‐12 h have been considered incorporating the kinetic features of polymerisation which includes a gel effect. The influence of the gel effect on the propagation and termination rate constants can be divided into two regions: one up to 20% conversion, and the other beyond it. In the first range the gel effect is independent of conversion while in the latter stage its influence is characterised by Ross‐Laurence parameters. The study indicates that no advantage is gained through the employment of two‐stage initiator loading. Curing cycles of longer duration can be generated for thicker castings from the analysis given.
Kinetics of phase separation in polyurethane/polystyrene semi‐1 interpenetrating polymer networks. 1. Light transmission studies
Authors: He Xiongwei , Widmaier Jean‐Michel , Meyer Guy C. 
Published: April 2007

AbstractThe phase separation of different in‐situ semi‐1 interpenetrating polymer networks (IPNs) based on polyurethane and polystyrene has been followed by light transmission. The effect of the presence ab initio of small amounts of homopolystyrene in the initial reaction mixture on the phase separation process has also been examined. If gelation of the polyurethane occurs before the onset of phase separation, the latter is impeded or strongly limited, and transparent semi‐1 IPNs are obtained. In the opposite case, phase separation is macroscopic and the material is turbid.
Kinetics of phase separation in polyurethane/polystyrene semi‐1 interpenetrating polymer networks. 2. Microscopy observations and theoretical approach
Authors: He Xiongwei , Widmaier Jean‐Michel , Meyer Guy C. 
Published: April 2007

AbstractThe phase separation process of in‐situ polyurethane/polystyrene semi‐1 interpenetrating polymer networks has been followed by optical microscopy completed by image analysis. The final morphology has been examined by scanning electron microscopy, and its relation to the phase separation process has been established. When phase separation occurs before gelation of the medium, polystyrene is dispersed both as large and small noduli in the polyurethane network; a polyurethane‐rich interphase separates the noduli from the matrix. These observations explain the previous results on the turbidity of such systems measured by light transmission. In the opposite cases, no visible phase separation is observed on the micrographs. The thermodynamics of the phase separation process has also been examined.
Crosslinking of PVC and NBR blends
Authors: Oravec Jan , Oishi Yoshiyuki , Hirahara Hidetoshi , Mori Kunio 
Published: April 2007

AbstractThe purpose of our work is to control the interfacial bonds between PVC and NBR using the ammonium salts of triazine thiols and dithiodimorpholine (DTDM) and thereby reveal the relation between the interfacial bonds and the final mechanical properties of products.In the experimental work a two‐stage process was used. At first, an NBR/PVC blend was mixed with a mono‐tetra‐n‐butylammonium salt of triazine trithiol at a temperature of 100°C on a two‐roll mill to give the branching structure of triazine thiols into PVC. In the second stage branched NBR/PVC reacted with DTDM to afford the branched PVC containing trithiomorphonyl groups. In the presence of ZnO at 160°C trithiomorphonyl groups react with NBR to form a crosslinking structure between NBR and PVC.The mechanical properties of cured NBR/PVC blends were markedly improved by the treatment process and after addition of tetramethylthiuram monosulphide also. The mechanical properties were not improved by increasing the concentration of TT‐TBA (tetrabutylammonium salt of 1,3,5‐triazine‐2,4,6‐trithiol) over 4.2 phr.
Synthesis and properties of aromatic ionenes
Authors: Hochberg Gerd C. , Schulz Rolf C. 
Published: April 2007

AbstractCationic polyelectrolytes with aromatic segments can be synthesized by a repetitive alkylation reaction. The structure of the products, their synthesis and their solubility are described. All ionenes are not, or only in small amounts, water soluble. The best solubility can be achieved by mixtures of polar protic and aprotic solvents. Variations of the counterion produces sufficient solubility in THF. All ionenes show a typical polyelectrolyte effect. The thermal stability of aromatic ionenes and the glass transition temperature is dominated by the nature of the counterion. The molecular weight of oligomers can be described by using a combination of a conductive titration method and an ion selective electrode.
Thermal behaviour of nylon 6 synthesized using urethane‐based initiator system
Authors: Desai Manish R. , Pandya Madhav V. 
Published: April 2007

AbstractUsing ϵ‐caprolactam capped urethane molecule as an initiator, nylon 6 was prepared by anionic method using sodium metal as catalyst. Two different aromatic diisocyanates were used to prepare the initiator. The effect of the nature and concentration of the initiator molecules on the physical and thermal properties of polyamide 6 is discussed.