bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melting and curie transition behavior of blends of vinylidenefluoride‐tetrafluoroethylene copolymer and polymethylmethacrylate
Authors: Cho Jae Whan 
Published: April 2007

AbstractThermal properties were investigated using differential scanning calorimetry of blends of vinylidenefluoride‐tetrafluoroethylene (VDF‐TFE) copolymer and polymethylmethacrylate. Curie transition behavior was strongly dependent on the crystallization temperature. A Curie temperature was shown in pure VDF‐TFE copolymer and in the blend with 91 wt % VDF‐TFE copolymer, which were crystallized above the Curie temperature. The samples crystallized above the Curie temperature showed higher melting temperatures than those crystallized below the Curie temperature, resulting in an upturn of slope at high temperatures in the Hoffman‐Weeks plot. The polymer‐polymer interaction parameter was calculated to be −0·165 at 130°C from the equilibrium melting temperatures, indicating miscibility of the two components.
Sulphur‐containing polyacrylates. III: UV‐induced copolymerization of methyl methacrylate with some dimethacrylates containing ether or thioether linkage
Authors: Andrzejewska Ewa 
Published: April 2007

AbstractThe UV‐induced copolymerization of methyl methacrylate (MM) with 2,2′‐thiobisethanol dimethacrylate (TEDM) and MM with 2,2′‐oxybisethanol dimethacrylate (OEDM) was investigated for a wide range of the diester content (6‐80 mol%) in the initial mixture. The influence of the feed composition on the course of copolymerization was determined. It was found that there exists a minimum on the plot of maximum yield of soluble copolymer versus diester content at a diester content of 30 mol%. The total copolymer yields were lower in the case of mixtures containing TEDM comonomer. Determination of the reactivity ratios gave the following values: for MM + TEDM ra = 0·21, rb = 4·59 and for MM + OEDM ra = 0·55. rb = 4·42. A possible explanation of the results obtained is discussed.
Surface inhibition of double base rocket propellants with photocurable unsaturated esters
Authors: Mirza Meher S. , Navale N. G. , Sadafule D. S. , Kumbhar C. G. , Panda S. P. 
Published: April 2007

AbstractInhibition of a double base propellant surface with a good percentage of nitro bodies in the propellant composition is a rather difficult process. One of the methods of inhibiting the surface is to use unsaturated polyesters with free radical cure having high exotherm as a barrier coating. This system has been improved by using a 1:1 mix of photocurable vinyl ester with pendant —OH groups and unsaturated polyester that underwent room temperature free radical cure. Adhesion of the barrier coat to the propellant surface through its —OH groups was stronger than the propellant strength itself. Additional layers of commercially available unsaturated polyester could be easily grafted on to the barrier coat through chemical cure.
Dilithium initiators based on 1,3‐bis(1‐ phenylethenyl)benzene. Tetrahydrofuran and lithium sec‐butoxide effects
Authors: Quirk Roderic P. , Ma Jing‐Jing 
Published: April 2007

AbstractThe adduct (3) from 2 moles of sec‐butyllithium with 1,3‐bis(1‐phenyl‐ethenyl)benzene has been prepared and evaluated as a hydrocarbon‐soluble, dilithium initiator for butadiene and styrene polymerization in cyclohexane or benzene solution. Under high vacuum conditions with purified reagents, bimodal molecular weight distributions are observed for polybutadienes with Mn < 150 × 103 g/mol and for polystyrenes with Mn < 50 × 103 g/mol; monomodal distributions are observed only for higher molecular weights. Addition of tetrahydrofuran ([THF]/[Li] = 14 to 32) or preformed lithium sec‐butoxide ([LiOBu]/[3] = 1·1) produces narrow, monomodal molecular weight distributions even at Mn = 26·2 × 103 g/mol polybutadiene and at Mn = 10 × 103 g/mol for polystyrene. Added lithium sec‐butoxide is the preferred additive since high 1,4‐polybutadienes are obtained. These results provide an explanation for the contradictory results reported previously; under less rigorous experimental conditions, oxygen and hydroxylic impurities can form lithium alkoxides in situ.
Kinetic behaviour of muscle LDH immobilized in nylon tubing
Authors: Roig M. G. , Bello J. F. , Cachaza J. M. , Kennedy J. F. 
Published: April 2007

AbstractImmobilization was carried out of the lactate dehydrogenase (LDH) from rabbit muscle (EC 1.1.1.27), cross‐linked through the bifunctional reactive glutar‐aldehyde on to nylon tubing (1 m long, 53cm2 internal surface area). Immobilized LDH inactivation kinetics are of first order (t1/2 = 3·6 years, k = 5·4,e−4 day−1 to 5°C). The smaller effect of pH on activity than in the case of LDH in solution can be explained on the basis of limitation to proton diffusion towards the support. A limiting effect to free external diffusion of the substrate towards and products from the support was also observed, an effect which seems to determine the effective kinetic behaviour of immobilized LDH. The apparent optimum temperature is centred around 40°C, observing a clear inactivation (thermal denaturation) above this temperature. In the temperature range studied (10–40°C), the co‐existence was seen of a kinetic control accompanied by another control, involving diffusional transport of substrates and products, on the global activity of the immobilized enzyme. This makes the Arrhenius profiles curvilinear. Both graphic and statistical non‐linear regression analysis of the kinetic data—rate, v, versus substrate concentration [S]—carried out under conditions in which the diffusional limitations can be considered negligible (high recirculation flow rate), permitted investigation of the intrinsic kinetic behaviour of immobilized LDH. In this sense, it can be deduced that the rate equation to which these data seem to be fitted is of the polynomial quotient type in [S] of minimum degree 2:2. Although the diffusional limitations have a marked effect on the type of global kinetics shown by immobilized LDH, temperature was not found to affect its v[S] behaviour. The experimental evidence obtained thus indicates that the rate equation in the 10‐40°C temperature range continues to be a rational equation of at least degree 2:2 in [S].
A study of the cements formed between metal oxides and polyvinylphosphonic acid
Authors: Ellis John , Wilson Alan D. 
Published: April 2007

AbstractIonic polymer cements, formed by the reaction of metal oxides or ionleachable glass powders with various polyacids, have found widespread use in dentistry. Commonly, the polyacid employed is a homopolymer or copolymer of acrylic acid. An alternative ionic polymer cement system has recently been developed, based on phosphonic acid polymers. In this study, cement formation between polyvinylphosphonic acid, PVPA, and a range of metal oxides has been examined, including an assessment of hydrolytic stability and the relative stabilities of the Mn+‐PVPA bonds formed. An infrared spectroscopic technique has been used to determine the relative extents of the reactions between PVPA and the various metal oxides.It is found that cements based on PVPA are far more reactive than those based on the polycarboxylic acids, and that the hydrolytic stability of the cements is greater. This greater resistance to water is probably due to the nature of the binding of the cations to the polyanion.
Thermotropic liquid crystalline copolyesters. II. Synthesis and thermal characterization of copolyesters of terephthalic acid, methyl hydroquinone and 1,4‐butane diol
Authors: Rath Asoke K. , Selvaraj Leena , Ponrathnam Surendra 
Published: April 2007

AbstractThe synthesis and thermodynamic evaluations of a series of random copolyesters based on terephthalic acid, methyl hydroquinone and 1,4‐butane diol are presented. The copolyester composition was varied by altering the relative concentrations of methyl hydroquinone and 1,4‐butane diol. The copolyesters display thermotropic transitions. The enthalpy changes during mesophasic transition display a minimum corresponding to equimolar composition. The copolyester with 75 mol% of spacer diol exhibited the lowest nematic transition temperature (190‐6°C). At this composition the nematic mesophase was most stable (δTN = 115‐6°C). ΔHN‐1 and ΔSN‐1 decrease with increasing rigid diol content. The isotropization temperatures were almost comparable since the largest mesogenic residues are similar in aspect ratio. These residues are required to melt prior to isotropization.
Polymeric surfactants for enhanced oil recovery. Part V: Prediction models for the effect of temperature and length of polyoxyethylene chain or hlb on surface and thermodynamic properties of some ethoxylated polymeric nonionics
Authors: Gendy T. S. , Barakat Y. , Mohamad A. I. , Youssef A. M. 
Published: April 2007

AbstractSeveral equation models were investigated to find the relationship between temperature (T). number of ethylene oxide (EO) units (n) or the hydrophile‐lipophile balance (HLB) and the surface and thermodynamic properties of some ethoxylated alkylphenol‐formaldehyde polymeric nonionic surfactants. These properties include critical micelle concentration (CMC), free energy of micellization (ΔGmic), surface tension at CMC (7CMC), effectiveness (γCMC) and efficiency (pC20) of surfactant to reduce the surface tension of water. The values of the ratio CMC/C2(π = 20) were also considered.The linear multiple regression technique was employed to determine the parameters of the equations and to choose the best forms with the highest values of R2 and F‐ratio which reflect the goodness and the reliability of the fit.
Performance of zircoaluminate coupling agents in wood flour/fibre‐polyolefin composites
Authors: Freischmidt G. , Michell A. J. 
Published: April 2007

AbstractWood flour and fibres do not bond well to polyolefins. Fillers or reinforcing agents for polyolefins based on these materials need to be treated before incorporation. This paper describes the property improvements obtained by treating papers, wood flour and wood fibres with zircoaluminate coupling agents before their forming into composites with polyolefins. The zircoaluminates were found to be effective coupling and hydrophobing agents in this system at low concentrations.
Studies on the hydrogenation of alkenes and alkynes using silica coated polymer anchored palladium complexes
Authors: Mathew Joice P. , Srinivasan M. 
Published: April 2007

AbstractPalladium complexes of polyvinyl pyridine coated silica gel have been prepared and used as hydrogenation catalysts for alkenes and alkynes under ambient conditions. The kinetics of hydrogenation for a few substrates have been studied and a possible mechanism proposed. The kinetic and mechanistic aspects of the hydrogenation of the substrates, effect of additives on the rate of hydrogenation, selectivity of the catalyst and recycling efficiency of the catalyst are presented in this paper.
Synthesis and characterisation of methoxysilyl terminated polybutadienes
Authors: Lindsell W. E. , Radha K. , Soutar I. 
Published: April 2007

AbstractPolybutadienyllithium systems with M̄n in the range 1.5 × 103‐20 × 103 are formed in hydrocarbon solvents by using n‐butyllithium or 3‐dimethylamino‐propyllithium as initiator. These ‘living’ polymers, of low polydispersity and relatively high 1,4‐structure, react with 3‐chloropropyl(trimethoxy)silane at < − 20°C, in the presence of tetrahydrofuran, to give, primarily, polymers terminated by the 3‐chloropropyl(dimethoxy)silyl group, Si(OMe)2{(CH2)3Cl}, as characterised by GPC and by 1H, 13C and 29Si NMR studies. Quaternisation by iodomethane of the telechelic polybutadiene with a dimethylamino end‐group produces a silylated cationomer containing the terminal functionality, I−+Me3N(CH2)3. In some silylation reactions of polybutadienyllithium systems, especially at higher temperatures, and in related reactions with Si(OMe)4, polymers coupled via the silyl groups are also formed. Hydrolysis of the terminal dimethoxysilyl functions occurs under acidic or basic conditions; end‐group coupling to silica gel also occurs and other reactions have been investigated.
Adsorption effect of 4‐carboxy benzene sulphonyl azide on calcium carbonate in sbr vulcanizates
Authors: Marcos A. , de Benito J. L. , Ibarra L. , Rodriguez A. , González L. 
Published: April 2007

AbstractThe effects of calcium carbonate modified with 4‐carboxy benzene sulphonyl azide on the mechanical properties of SBR mixes have been investigated. The studies include determination and comparison of tensile strength, elongation, tear strength, compression‐relaxation behaviour, and swelling measurements of modified and unmodified filler systems. The results show that the azide attached to the surface of the filler particles reacts with the rubber and improves the mechanical properties.
Mechanistic and kinetic studies on the polymerization of styrene initiated by dimethyl sulfonium 2‐pyridyl carbonyl methylide
Authors: Bhatnagar Urvi , Srivastava A. K. 
Published: April 2007

AbstractDimethyl sulfonium 2‐pyridyl carbonyl methylide (Ypy‐s) initiated radical polymerization of styrene in dimethyl sulfoxide at 85±0.1°C for 6 h under a nitrogen blanket using dilatometric techniques has been studied. The initiator and monomer exponent values were calculated to be 0.5 and 1.2, respectively. The system follows ideal radical kinetics with bimolecular termination. The higher monomer exponent value is ascribed to significant solvent effects on the initiation rate. The overall activation energy and average value of k2p/kt are 52.0 kJ mol−1 and 1.0 × 10−3 litre mol−1 s−1, respectively. The polymerization was retarded in the presence of hydroquinone or benzene; dimethylformamide, however, enhanced the rate of polymerization. Kinetic data and ESR studies indicate that the overall polymerization takes place via triplet carbene formation which acts as a source of free radicals.
Singlet oxygen lifetime in polymer films
Authors: Schiller Kurt , Müller Franz Werner 
Published: April 2007

AbstractSinglet oxygen lifetimes [τ(1O2)] in polymer matrices were calculated using the strong exponential correlation between the incremental rate constant (Kxy) of energy transfer from 1O2 to terminal oscillators X—Y contained in solvent molecules and the energy (Exy) of the highest fundamental vibration of the oscillator X—Y. The lifetimes in polymers correspond very well to experimental data in the literature. They depend only on the nature and quantity of molecular oscillators in the medium but not on the state of aggregation. The computed lifetimes in common polymers vary only from 10 to 50 μs. Therefore the lifetime of 1O2 in singlet oxygen reactions in polymers is of secondary importance in comparison to the diffusion coefficient.
Synthesis and characterisation of graft copolymers of oxidised rubber and 2‐hydroxy ethyl methacrylate
Authors: Devi Surekha , Rakshit Animesh Kumar , Guthrie James T. 
Published: April 2007

AbstractNatural rubber was oxidised by hydrogen peroxide using 7 radiation. Various conditions such as variations in time of exposure to 7 radiation, H2O2 concentration, grafting reaction time and monomer to polymer ratio were examined with respect to optimisation of grafting. The resulting graft ccpolymers were characterised by FTIR, DSC, contact angle measurement and electrokinetic potential measurements.
Thermally stimulated discharge current studies in pure and fe‐doped polystyrene films
Authors: Sharma A. K. , Sagar D. Santhi 
Published: April 2007

AbstractStudies were made on the thermally stimulated discharge currents (TSDCs) in pure (undoped) and Fe‐doped polystyrene films as a function of polarizing field, polarizing temperature and dopant concentration. While undoped films exhibited a single peak, doped films showed two peaks one at low temperatures and another at high temperatures. The low temperature peak, which exhibits a shift towards lower temperatures with increasing dopant concentration, is attributed to the relaxation of the main chain, while the high temperature peak, which shows a tendency to shift towards higher temperatures with dopant concentration, is due to space charge polarization. The TSDCs were higher for low dopant concentrations than their undoped counterparts, while for high concentrations of the dopant, the TSDCs decreased. Formation of charge transfer complexes at low dopant concentrations and molecular aggregates at higher dopant concentrations are suggested as the possible reasons for this behaviour.
Calorimetric study of some poly(mono‐n‐alkyl itaconates)
Authors: Diaz‐Calleja Ricardo , Ribes‐Greus Amparo , Gargallo Ligia , Radić Deodato 
Published: April 2007

AbstractA calorimetric study of poly(mono‐n‐alkyl itaconates) containing 8, 10, 12 and 14 carbon atoms in the side chain was performed. No glass transition temperature (Tg) was observed in the temperature range 213‐263 K, but a melting process was observed for the dodecyl and tetradecyl derivatives, which was attributed to crystalline order in the long side chains.
Electrochemical behaviour of polyaniline in aromatic sulphonic acids
Authors: Dhawan Sundeep Kumar , Trivedi Dinesh Chandra 
Published: April 2007

AbstractThis report describes the synthesis and redox behaviour of polyaniline in aqueous solutions of benzene sulphonic acid and 4‐toluene sulphonic acid. The characterization of the polymer was carried out by electronic spectra, FTIR studies and 1HNMR in DMSO‐d6.
Tensile yield parameters for poly(vinylchloride) blends with a methyl methacrylate–butadiene–styrene impact modifier
Authors: Havriliak S. , Slavin S. E. , Shortridge T. J. 
Published: April 2007

AbstractTensile yield measurements were made on blends of poly(vinyl chloride) (PVC) with a methyl methacrylate‐butadiene‐styrene impact modifier (MBS) covering a blend range of 0 to 20 wt % MBS, a temperature range of −50 to 25°C, and a strain rate range of 10−3 to 10° s−1. Increasing MBS level in PVC reduces the tensile yield stress. The tensile yield stress variation with temperature and strain rate at constant MBS level was represented in terms of the Ree‐Eyring‐Roetling rate model. This model represents the experimental data within experimental error. The tensile yield parameters were also determined by assuming that stress concentrations exist around the modifier equatorial plane. Estimates of these stress concentrations were made and are discussed in terms of Goodier's model for spherical inclusions.
pH‐stat methodology in continuous monitoring of the kinetics of hydrolysis of phosphate esters catalysed by alkaline phosphatase from human placenta: II. Kinetic aspects
Authors: Roig M. G. , Serrano M. A. , Bello J. F. , Cachaza J. M. , Kennedy J. F. 
Published: April 2007

AbstractThe adaptation of the pH‐stat to continuous monitoring of the in‐vitro hydrolase activity of alkaline phosphatase in solution, an activity which until now has only been analysed by means of spectrophotometric methods in a continuous or static state, is described. To control the reliability of the method in the monitoring of these enzymic reactions, a series of kinetics of hydrolysis of chromogenic (p‐nitrophenyl and o‐carboxyphenyl phosphates) and non‐chromogenic (ATP) substrates was carried out, comparing the results obtained via continuous spectrophotometric analysis of the corresponding phenol released or via a discontinuous technique by the phosphate produced with those results obtained via pH‐stat analysis of the H+ released or utilized by the enzymic reaction of hydrolysis. It can be concluded that kinetic studies carried out on the pH‐stat of in‐vitro alkaline phosphatase activity offer results analogous to those obtained for the same system through classic spectrophotometric methods, offering as well notable advantages of speed and simplicity in the kinetic assays since it is always possible to monitor the enzymic activity continuously, with chromogenic or non‐chromogenic substrates. The pH‐stat methodology affords additional information on the kinetics of action of alkaline phosphatase from placenta acting on non‐chromogenic biological substrates. In this sense, kinetic studies with the pH‐stat on the enzymic hydrolysis of ATP were begun, determining their rate versus pH profile (optimum pH at 9.1) and proposing possible ‘non‐Michaelian’ type kinetic behaviour of the enzyme in solution as deduced from the graphical analysis of the data v([ATP]).
Poly(chloroprene)‐castor oil based polyurethane semi‐interpenetrating polymer network as an adhesive
Authors: Rajalingam P. , Radhakrishnan Ganga 
Published: April 2007

AbstractThe adhesive behaviour of polychloroprene rubber (CR)‐castor oil based polyurethane (CPU) semi‐interpenetrating network (SIPN) was studied by peel strength and shear strength. The order of peel and shear strength is leather‐leather>leather‐rubber>rubber‐rubber. Effects of solvents and acids on the bonded assembly were tested.
Epoxides bearing azomethine linkages
Authors: Mikroyannidis John A. 
Published: April 2007

AbstractSeven structurally different diepoxides, triepoxides or tetraepoxides bearing azomethine linkages were synthesized and characterized. The reactions of 4‐hydroxybenzaldehyde or 3,4‐dihydroxybenzaldehyde with 4‐aminophenol or 4‐aminobenzoic acid afforded azomethines, which reacted subsequently with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide to yield diepoxides or triepoxides. Triepoxides were prepared by reacting 4‐hydroxybenzaldehyde with 5‐aminoisophthalic acid or 4‐amino‐2‐hydroxybenzoic acid again to yield azomethines, which were subsequently reacted with epichlorohydrin. In addition, a tetraepoxide was prepared from the reaction of 1,4‐benzenedicarbaldehyde with a double molar amount of 4‐amino‐2‐hydroxybenzoic acid to afford a bisazomethine followed by reaction with epichlorohydrin. The epoxy compounds were characterized by IR and 1H NMR spectroscopy. Their thermal polymerization in the presence of 4,4‐diaminodiphenylsulfone (DDS) was investigated by DTA. Thermal stabilities of cured resins were ascertained by TGA and isothermal gravimetric analysis (IGA) in N2 or air. The polymer derived from the tetraepoxide was the most heat‐resistant. It was stable in N2 up to 313°C and afforded an anaerobic char yield of 58% at 800°C.
Experimental evidence for the existence of intramolecular hydrogen bonds in the water‐insoluble sodium salt of carboxyethyl cellulose solid
Authors: Kowsaka Keisuke , Yasuda Katsunari , Okajima Kunihiko , Kamide Kenji 
Published: April 2007

AbstractAn attempt has been made to explain the solubility behavior of sodium carboxyethyl cellulose (NaCEC) towards water and aqueous sodium hydroxide (aq. NaOH) in terms of supermolecular structure, i.e. degree of breakdown of intramolecular hydrogen bonding related to the degree of substitution. For this purpose, five NaCEC samples with «F» ranging from 0.03 to 0.0.39 were prepared in homogeneous aqueous media and subjected to CP/MAS 13C NMR and deuteration IR measurements. Existence of O3H…O'5 intramolecular hydrogen bonds in solid water‐insoluble NaCEC was first confirmed using both CP/MAS NMR and deuteration IR. This fact strongly suggests that for cellulose derivatives with relatively low «F» the solubility of the derivative in water or aq. NaOH is mainly governed by the considerable destruction of intramolecular hydrogen bonds. These findings are consistent with our previous conclusions [Polym. J., 16 (1984) 857] that the solubility of pure cellulose solid in aq. NaOH is mainly governed by the destruction of intramolecular hydrogen bonds.
Review: Complex formation between polymer pairs for template polymerization
Authors: Srivastava A. K. , Tewari Neeta , Awasthi Sanjay K. 
Published: April 2007

AbstractThis review paper presents an account of complex formation between polymer pairs for template polymerisation. The values for the coefficient of interaction KAB, evaluated using the polymer solvent method have been examined for a number of vinyl polymers in different solvents.