bluuebunny/crossref_metadata_2025_split huggingface dataset:
An experimental investigation of poly(vinyl chloride) emulsion polymerization: Effect of initiator and emulsifier concentrations on polymerization kinetics and product particle size
Authors: Karakaş Gürkan , Orbey Neşe 
Published: April 2007

AbstractEffects of concentration changes in initiator species Na2SO3, (NH4)2S2O8 and CuSO4, and emulsifier, ammonium stearate, on poly(vinyl chloride) (PVC) emulsion polymerization kinetics and on product particle size were experimentally investigated. It was observed that to obtain industrially significant rates and overall conversions, not only an optimum concentration ratio of Na2SO3/(NH4)2S2O8/CuSO 4 must be used, but also the concentrations of these species must be above certain limits. Increasing the concentration of the emulsifier used did not influence the rate of polymerization, but led to increases in limiting conversions.Product particle size analyses indicate that average particle size is independent of initiator concentration and rate of initiation. An increase in the emulsifier concentration on the other hand appears to lead to an increase in number of particles in the system and thus promotes smaller particle sizes.
Two‐dimensional nuclear magnetic resonance of resins
Authors: Duff Alastair J. , Kemp William , Steedman William , Boyd Alan S. F. 
Published: April 2007

AbstractA group of resins was synthesised from a series of phenols and aldehydes, and their structures comprehensively deduced from two‐dimensional nuclear magnetic resonance spectroscopy (2‐D NMR). Correlation spectroscopy, in particular carbon‐proton heteronuclear chemical shift correlation spectroscopy, was shown to be especially incisive in assigning structural features to the NMR signals.The method has permitted fuller structural characterisation of these materials than was heretofore possible, and has identified, inter alia, methylene and methyleneoxy bridges unequivocally: complex substitution patterns in the phenol‐derived aromatic rings have also been elucidated.It is demonstrably possible to apply the same techniques to similar complex resin structures, and to utilise these structural insights to determine the mechanistic processes involved in their syntheses.
Aqueous polymerization of methyl methacrylate initiated by the redox system Ce(IV)—D‐glucose. I: General features and kinetics
Authors: Fernández M. D. , Guzmán G. M. 
Published: April 2007

AbstractThe polymerization of methyl methacrylate initiated by the ceric ammonium nitrate‐D‐glucose redox system has been studied in aqueous nitric acid under nitrogen in the temperature range 20‐5 to 35°C. The initial rate of polymerization was determined gravimetrically whereas the initial rate of ceric ion disappearance was determined by titration of ceric ion. The relationships between conversion and D‐glucose, Ce(IV), and monomer concentrations were determined. The dependence of the rates on D‐glucose, Ce(IV), and monomer concentrations was evaluated. The effect of temperature was also examined.
Start‐up and growth mechanisms in the loop continuous reactor
Authors: Geddes Kenneth R. 
Published: April 2007

AbstractChanges in physical properties during Loop continuous emulsion polymerisation reactor runs were studied, with particular reference to particle size distribution. Cycling of properties similar to those reported for continuous stirred tank reactors (CSTRs) was found.The cycling of properties was attributed to an intermittent creation of new particles caused by changes in surface area. It was predicted that cycles would die away and an equilibrium would be established. This occurs in practice.
Polymeric surfactants for enhanced oil recovery. Part II—the hlb‐cmc relationship of ethoxylated alkylphenol‐formaldehyde polymeric surfactants
Authors: Barakat Y. , Gendy T. S. , Basily I. K. , Mohamad A. I. 
Published: April 2007

AbstractThe natural log of critical micelle concentration (CMC) values obtained from the natural log discontinuities in surface tension‐concentration relationships, through the least‐squares regression analysis, were plotted against the respective hydrophile‐lipophile balance (HLB) values of four groups of ethoxylated octylphenol‐, dodecylphenol‐, tetradecylphenol‐ and hexadecylphenol‐formal‐dehyde polymeric surfactants.The obtained HLB‐CMC relationship for the investigated compounds can be represented satisfactorily by the linearized equation In (CMC) = a—b (HLB). Values of the two constants a (intercept) and b (slope) for 16 of these compounds were determined at 28, 38, 48 and 58°C, using the least‐squares regression analysis of data. The study revealed that both a and b values increase with increasing number of carbon atoms in the ethoxylates of polymeric compounds having a linear alkyl chain. The influence of branching is reflected in the values of a and b of the compounds having a branched dodecyl chain.The most striking feature of the obtained equation is that the CMC decreases with increasing HLB (negative slope). This observation is contrary to what is generally expected for both ionic and nonionic surfactants.
Effects of synthesis conditions on radiation‐induced graft copolymerization of methacrylic acid on to poly(vinyl chloride) films
Authors: Singh Jagbir , Ray A. R. , Singh Harpal 
Published: April 2007

AbstractPoly(vinyl chloride) (PVC) films were grafted with methacrylic acid (MAA) using a simultaneous‐irradiation technique. The effect of solvent ratio (methanol‐water) on grafting was studied and maximum grafting was found for an equivolume mixture of methanol and water. The graft level increased with increase of the plasticizer (dioctylphthalate) content in PVC. Grafting was found to be higher at low dose rate and increased linearly up to 0.25 Mrad for all dose rates and then levelled off. Grafting also increased continuously with increasing monomer concentrations up to 5.4mol/litre, but a linear increase in grafting was observed only up to 2.5 mol/litre. The dependences of rate of grafting on dose rate and monomer concentration were found to be 0.62 and 1.20 respectively.
Comparative effects of resorcinol and bisphenol A in non‐mesogenic units in liquid crystalline copolyesters containing a flexible spacer
Authors: Rao A. Kameswara , Lenz Robert W. , Jin Jung‐Ii 
Published: April 2007

AbstractTwo series of copolyesters containing both linear mesogenic and nonlinear, non‐mesogenic aromatic ester units, each with a decamethylene spacer, were prepared and characterized for the effect of the non‐mesogenic unit and the spacer on the stability of the liquid crystalline (LC) phase. The mesogenic units were formed from the reaction of 2‐chlorohydroquinone and 1,10‐bis(4‐carboxy‐phenoxy)decane while the non‐mesogenic units were derived from reacting either resorcinol (Series I) or bisphenol A (Series II) with the latter monomer. The non‐mesogenic units containing bisphenol A were found to be more efficient in destroying liquid crystallinity of the copolyesters than were resorcinol‐containing units. However, the presence of a flexible spacer in each unit allowed the copolymers to form a nematic LC phase even at contents of the resorcinol and bisphenol A non‐mesogenic units as high as 70 and 60 mol %, respectively.
Siloxanes with 1‐oxypyridin‐3‐yl groups. Part 6. synthesis of copolymers and application as transacylation catalysts
Authors: Zeldin Martel , Fife Wilmer K. , Tian Cheng‐Xian , Xin Yue 
Published: April 2007

AbstractLinear end‐blocked and crosslinked siloxane copolymers containing dimethylsiloxyl and methyl(1‐oxypyridin‐3‐yl)siloxyl groups were prepared and characterized thermally (TGA) and spectroscopically. These hydrophobic copolymers were found to be highly effective transacylation catalysts in the synthesis of carboxylic anhydrides and the hydrolysis of diphenyl phosphoro‐chloridate (DPPC) under phase‐transfer catalysis (PTC) conditions, i.e. CH2Cl2‐H2O suspension. The insolubility of the copolymers in water and the preference of the intermediate, polymeric 1‐acyloxypyridinium ion for the more lipophilic carboxylate ion in anhydride formation suggest that the reaction occurs at the CH2Cl2‐H2O interphase. The rapid rate of hydrolysis of DPPC under PTC conditions and in water provides evidence for initial hydrophobic binding or association of the hydrophobic catalyst prior to reaction with a water‐insoluble substrate.
Polyorganosiloxanes containing both ester and hydride functionalities: A detailed study by 1H and 13C NMR spectroscopy
Authors: Ashworth Anthony J. , Brisdon Brian J. , Zafar Imran , England Richard 
Published: April 2007

AbstractA total of eighteen linear polysiloxanes of general formula Me3SiO‐(MeSi(E)O)x(MeSi(H)O)ySiMe3 (E = —(CH2)nester; x+y = 40) have been prepared by the platinum catalysed addition of CH2=CH(CH2)n‐2 ‐ester to Me3SiO‐(MeSi(H)O)40SiMe3 under anhydrous conditions. Polymers containing the ester functionalities—(CH2)3CO2R(R = Me, CF3, Et, Pr, and CH2COMe),—(CH2)3‐CHMeCO2Et, —(CH2)2CH(CO2Me)2, —(CH2)3CH(CO2Et)2, ‐(CH2)3CO2CH= CHCO2CH2CH=CH2 and —(CH2)3CO2C6H4CO2 CH2CH=CH2 have been characterised by analysis and 1H and 13C NMR spectroscopies. Factors affecting Markownik off versus anti‐Markownikoff addition of allyl acetate to this polymethylsiloxane have also been explored.
Aqueous polymerization of methyl methacrylate initiated by the redox system Ce(IV)‐D‐Glucose. II: Effect of reaction conditions on polymer molecular weight
Authors: Fernández M. D. , Guzmán G. M. 
Published: April 2007

AbstractThe dependence of molecular weight of poly(methyl methacrylate) on reaction conditions, as polymerized in aqueous nitric acid with the redox system ceric ammonium nitrate‐glucose, has been studied. The average molecular weights and molecular weight distributions were determined by size‐exclusion chromatography. The degree of polymerization was found to increase in the course of a run and was also affected by changes of Ce(IV) and glucose concentrations in the range where the rate of polymerization increased, but not where the rate was independent of Ce(IV) concentration and decreased with glucose concentration. The average molecular weights can be controlled by variations in monomer concentration and in temperature. The polymerization rate was found to attain a maximum with nitric acid concentration whereas the rate of ceric ion consumption increased. A fall in the degree of polymerization was observed on increasing the acid concentration. The effect of nitrate ion concentration as well as of that of certain water‐miscible solvents on the above‐mentioned parameters has also been studied.
Thermal behaviour of partially neutralised ethylene‐maleic acid copolymer
Authors: Nicholson John W. , Wasson Eleanor A. 
Published: April 2007

AbstractAs part of continuing studies on the cure of candidate polymers for waterborne coatings, the thermal behaviour of partially neutralised ethylene‐maleic acid copolymer, EMA, has been examined. Films of EMA neutralised with a variety of bases were heated at 250°C. For this copolymer, as for poly(acrylic acid) at the same temperature, reflectance infrared spectroscopy has shown that heating led initially to anhydride formation. In the unneutralised state, or with the divalent ions calcium, magnesium, cobalt or zinc, further heating led to little or no further reaction. By contrast, the presence of univalent metal ions lithium, sodium and potassium caused a second reaction to occur, namely decarboxylation to yield keto crosslinks. This second reaction, however, did not occur to the extent that it does with poly(acrylic acid) under identical conditions. Possible reasons for this are discussed.Unlike poly(acrylic acid), EMA when partially neutralised was found not to form continuous films on the tin‐plate substrate.
Effect of stretching temperature on proton spin‐lattice and spin‐spin relaxation times of isotactic polypropylene film
Authors: Tanaka Hiroshi , Takagi Kiyohide 
Published: April 2007

AbstractStructural properties of isotactic polypropylene film during stretching were investigated mainly by the measurements of proton spin‐lattice, T1 and spin‐spin, T2, relaxation times. Both T1 and T2a, T2 of the most mobile amorphous regions, of the sample stretched at 150°C are longer than those of the sample stretched at 130°C. These results indicate that in the sample stretched at 150°C the proportion of mobile amorphous region decreases, while the amorphous region achieves enhanced molecular mobility.
Kinetic study of aqueous polymerization of methyl methacrylate initiated by Ce(IV)‐maltose redox system
Authors: Fernández M. D. , Guzmán G. M. 
Published: April 2007

AbstractPolymerization of methyl methacrylate initiated by ceric ammonium nitrate‐maltose has been investigated in aqueous nitric acid under nitrogen in the temperature range 20.5‐35°C. The dependence of the initial rate of polymerization and the initial rate of ceric ion consumption on maltose, Ce(IV), and monomer concentrations has been determined. The reaction orders were found to depend on ceric ion concentration. At a moderately high Ce(IV) concentration (1 × 10−3mol litre−1) the orders were 1/2 and 3/2 with respect to maltose and monomer concentration, respectively, and independent of Ce(IV) concentration. But at a low Ce(IV) concentration (4 × 10−4mol litre−1) the orders with respect to monomer and Ce(IV) changed to 1 and 1/2, respectively. The effect of temperature was also examined. The average molecular weight, as determined by size‐exclusion chromacography, was found to depend on maltose, Ce(IV), and monomer concentrations, as well as on temperature.
Blends of polycarbonate and poly(hexamethylene sebacate): IV. Polymer blend intrinsic viscosity behavior and its relationship to solid‐state blend compatibility
Authors: Shih K. S. , Beatty C. L. 
Published: April 2007

AbstractThe intrinsic viscosities of blends of bisphenol‐A polycarbonate and poly(hexamethylene sebacate) have been measured in chloroform as a function of blend composition for a variety of molecular weight species. The compatibility of the polymer blend mixtures is characterized by the parameter δb, from the Krigbaum and Wall theory. Using Tg of the blend as a measure of bulk solid‐state compatibility, a correlation is obtained with the Krigbaum and Wall parameter δb for each of the molecular weight pairs studied. Slopes of the correlation are invariant, as expected, as the chemical composition is the same for the different molecular weight pairs studied.
Kinetics of photo‐oxidative degradation and stabilization of poly(2,6‐dimethyl‐1,4‐phenylene oxide) by metal dialkyl dithio phosphate
Authors: Chandra R. , Thapliyal B. P. , Singh R. P. 
Published: April 2007

AbstractThe kinetics of photo‐oxidative degradation and stabilization of poly(2,6‐dimethyl‐1,4‐phenylene oxide) have been studied in the temperature range 313‐363 K using monochromatic light of 365 nm with a constant intensity flux of 8.7 × 10−9 einstein s−1 cm−2 in the absence and presence of Ni(II) O,O′‐diisopropyldithiophosphate. The course of degradation and stabilization was determined by means of light scattering and spectroscopic techniques. The extent of photodegradation was followed by carbonyl formation, gel content and activation energy. The incorporation of 1.2 wt% stabilizer in the matrix of the polymer films exercises the maximum protective influence on the photodegradation of the polymer.
Synthesis and characterisation of poly(arylene sulphides): Part 11. Preparation of poly(1,4‐phenylene sulphide) directly from bis(4‐bromophenyl) disulphide
Authors: Lovell Peter A. , Still Richard H. 
Published: April 2007

AbstractReaction conditions for the preparation of poly(1,4‐phenylene sulphide) (PPS) directly from bis(4‐bromophenyl) disulphide (BBD) have been established. Reactions were performed in a boiling quinoline/pyridine solvent mixture (91% by vol. quinoline) in the presence and absence of copper powder. Reaction products were fractionated and the fractions characterised using elemental analysis, IR and NMR spectroscopy, viscometry, hot‐stage microscopy, differential scanning calorimetry, thermogravimetry and curing studies. The yields and properties of the polymeric fractions are compared to those of similar fractions obtained from preparation of PPS by solution polymerisation of copper(I) 4‐bromobenzenethiolate under conditions which correspond to those employed in this work.PPS was not produced, and BBD was almost quantitatively recovered when copper was absent from the reactants.Reactions performed using an equimolar ratio of copper to BBD produced PPS of molar mass approximately 2–4 × 103 gmol−1 in 76% yield after 8h reaction. However, this PPS was contaminated with an insoluble infusible material which had a deleterious effect on the physical properties of derived cured PPS materials. The yield of PPS decreased and the quantity of contaminant increased as reaction time increased.PPS of molar mass approximately 104g mol−1 was obtained in 50–60% yield, free from insoluble infusible material, when the molar ratio of copper: BBD was increased to 2:1; it exhibited normal properties on curing.
Electron transport in Fe‐doped polyvinyl acetate films
Authors: Sharma A. K. , Rukmini B. 
Published: April 2007

AbstractThe electrical conductivity and current‐voltage characteristics of pure and Fe3+‐doped polyvinyl acetate films have been studied for various temperatures and bias field strengths. The activation energy for conduction showed an increasing trend with increasing dopant concentration. This has been attributed to the formation of molecular aggregates. The variation of electrical conductivity for doped films with temperature showed three regions with different activation energies. This behaviour has been explained in terms of the type of conduction mechanism operating in the material. It has been suggested that at low temperatures the conduction is electronic while at high temperatures it appears to be ionic. As the dopant concentration increases ionic conduction tends to dominate the electronic conduction even at low temperatures. From the current‐voltage measurements it has been concluded that the conduction mechanism tends towards Schottky type with increasing dopant concentration.
An analytical method for the determination of cationic flocculants of the epichlorohydrin‐dimethylamine condensate type
Authors: Clarke Michael Cassin 
Published: April 2007

AbstractA method for the analysis of epichlorohydrin‐dimethylamine flocculants is presented. The method is applicable to concentrations of flocculant of between 2 and 60 parts per million. These concentrations are used in coal and other mineral processing operations. An extension of the method may be used to give semiquantitative estimations of higher concentrations.
Kinetics of ylide‐initiated radical copolymerization of 4‐vinylpyridine and methyl methacrylate
Authors: Vasishtha Rita , Awasthi Sanjay , Srivastava A. K. 
Published: April 2007

AbstractThe ylide‐initiated radical copolymerization of 4‐vinylpyridine (4‐VP) with methyl methacrylate (MMA) at 60°C using carbon tetrachloride as inert solvent yields non‐alternating copolymers. The kinetic parameters, average rate of polymerization (Rp) and orders of reaction with respect to monomers and initiator, have been evaluated and the kinetic equation is found to be Rpα[ylide]0.94 [MMA]1.0 [4‐VP]1.5. The values of the energy of activation and kp2/kt are 48 kJ mol−1 and 6.6 × 10−5 litre mol−1s−1, respectively. The copolymers have been characterized by IR and NMR spectroscopy.
Processing and characterization of a biaxially oriented conducting polymer
Authors: Machado J. M. , Masse M. A. , Karasz F. E. , Burnett J. M. , Kovar R. F. , Druy M. A. 
Published: April 2007

AbstractTwo methods have been developed for the preparation of biaxially oriented poly(phenylene vinylene) from its poly(sulfonium salt) precursor. A two‐stage stretching process permits non‐equibiaxial stretching over a wide range of deformation ratios and a bubble expansion technique allows equibiaxial planar extension. The resulting films were examined using X‐ray diffraction prior to chemical doping with SbF5 vapor. Biaxial orientation was shown to exert considerable influence over the attainable electrical conductivity.
Electroinitiated polymerization of bis(tribromophenoxo)‐N,N,N′,N′‐tetramethylethylenediamine copper(II) complex
Authors: Akbulut Ural , Sacak Mehmet , Kisakürek Duygu , Toppare Levent 
Published: April 2007

AbstractTribromophenol copper(II) complexes with ligands such as pyridine and ethylenediamine are known to polymerize thermally. Generally, high temperature is required for thermal polymerization of such complexes. Thermal polymerization of trihalophenol copper(II) complexes in toluene has an induction period of c. 30 min. Electroinitiated polymerization of trihalophenol copper(II) complexes has also been accomplished recently using pyridine or ethylenediamine as ligands. However, the above mentioned copper(II) complexes cannot be polymerized electro‐chemically in acetonitrile. When pyridine and ethylenediamine are used as ligands, such complexes rapidly polymerize in acetonitrile without the passage of any current even at room temperature. Therefore, the electrochemical polymerization of trihalophenol copper(II) complexes with pyridine and ethylenediamine ligands must be carried out in dimethylformamide.In the present work, electroinitiated polymerization of bis(2,4,6‐tribromo‐phenoxo)‐N,N,N′,N′‐tetramethylethylenediamine copper(II) complex (TBPTD) was accomplished for the first time in acetonitrile. When N,N,N′,N′‐tetramethylethylene diamine is used as the ligand in the preparation of tribromophenol copper(II) complex it is found that acetonitrile can be used as solvent. This complex does not polymerize in acetonitrile without the application of potential.Electroinitiated polymerization of TBPTD was carried out by constant potential electrolysis, at each anodic peak potential of the complex. These potentials of TBPTD were measured, in advance, by cyclic voltammetry in acetonitrile.Electrolysis of TBPTD yielded polymers in the anode compartment only. Electroinitated polymerization of this monomer exhibited no induction period in contrast to the case of thermal polymerization.The reacted monomer concentration was simultaneously followed by cyclic voltammetry, in the same electrolysis cell. This process was accomplished by a specially designed H‐type cell equipped with six electrodes. Use of cyclic voltammetry for simultaneous in‐situ monitoring of reacted monomer concentrations was found to be more accurate, quicker and more reproducible than gas chromatography or spectroscopy.Polymers were characterized by FTIR, 1HNMR, and 13CNMR spectral analyses as well as measurement of molecular weight by the isopiestic method.
Studies on grafting of methacrylic acid on to poly(vinyl chloride) films
Authors: Singh Jagbir , Ray Alok R. , Singh Harpal 
Published: April 2007

AbstractThe characterization of poly(vinyl chloride‐g‐methacrylic acid) (PVC‐g‐MAA) films, prepared by the simultaneous‐irradiation technique, was undertaken through swelling measurements, attenuated total reflection infrared spectroscopy (ATRIR), scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and thermogravimetric analysis (TGA). The per cent swelling of grafted PVC in various media increased with the increase in the graft level. A higher per cent swelling was observed in 0‐5m NaOH aqueous solution relative to that in distilled water. It is concluded from the ATRIR and ESCA studies that the concentration ratio of oxygen to chlorine atoms on the surface of grafted PVC increased compared with unmodified PVC, indicating grafting of methacrylic acid on to the surface. It was also found that the thermal properties of PVC improved after grafting with methacrylic acid.