bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(2‐hydroxyethyl methacrylate) (PHEMA)/poly(styrene‐co‐acrylamide) (PSAm) blends: miscibility and hydrogel properties
Authors: Zhu K. J. , Wang Liqun , Yang Shilin 
Published: April 2003

AbstractThe blend miscibility of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(styrene‐co‐acrylamide) (PSAm) was studied by DSC. A ‘miscible window’ was found in the range 47–57 mol% of acrylamide in blending PSAm with PHEMA (1:1 w/w) and was analysed by the mean‐field theory. The water content and permeability coefficients of proteins were measured. The results show that the water content of the blends depends on the composition of PSAm and the blends, and the behaviour of blends swollen in water in Fickian type. However, the permeability of the solutes not only related to water content, but was also affected by phase behaviour. Controlled release of somatotropin from a cylindrical device coated with PHEMA/PSAm was achieved.
Miscibility of poly(vinylidene fluoride) and potassium salt of poly(methyl methacrylate‐ran‐methacrylic acid)
Authors: Leung Louis M. , Lo Kenneth K. C. 
Published: April 2003

AbstractThe crystalline–amorphous polymer pair of poly(vinylidene fluoride) and poly(methyl methacrylate) is known to be miscible over a wide composition range. The effects of ionic moieties on the miscibility were studied by replacing the poly(methyl methacrylate) with a series of random copolymers of methyl methacrylate and potassium salt of methacrylic acid. The interaction parameter (χ) for the miscible blends in their molten state was obtained by thermal analysis using a melting‐point depression calculation. The parameter decreased to a minimum at c.2% ion content (χ=minus;0.514) and approached a positive value at above 10% ion concentration.
Water sorption and water binding properties of crosslinked polyacrylamides: effect of macromolecular structure and crosslinking
Authors: Chandy Mathew C. , Pillai V. N. Rajasekharan 
Published: April 2003

AbstractThe water binding properties of crosslinked copolymers of acrylamide with tetraethyleneglycol diacrylate triethyleneglycol dimethacrylate, N,N′‐methylene bisacrylamide and divinylbenzene were investigated. It was observed that the freezing water contents of these copolymers depend on nature of the monomers and crosslinkers, as well as on the extent of crosslinking.
Surface modification of kaolin. 2. Enhanced steric stabilisation of polymer‐modified kaolin
Authors: Molphy Marylou , Mainwaring David E. , Rizzardo Ezio , Gunatillake Pathiraja A. , Laslett Robert L. 
Published: April 2003

AbstractThe polymer‐modified surface of kaolin was studied to determine the effect of changing the molecular weight of the polymer chain grafted on the surface. The particle was modified by attaching poly(ethylene oxide) to the surface using a urethane linkage.Upper critical flocculation temperature and contact angle measurements were conducted to quantify the changes in surface characteristics and stability in an aqueous dispersion. The effect of pH on stability and grafted density of polymer chains showed the mechanism of stabilisation to be that of enhanced steric stabilisation.The kaolin particle was also modified with the more hydrophobic poly(propylene oxide). The behaviour was characterised as for poly(ethylene oxide) and interesting differences in extent and mechanism for stabilisation were observed.
Thermal degradation of polymethacrylic ester containing bisphenol‐S
Authors: Liaw Der‐Jang , Teng Kuei‐Fei 
Published: April 2003

AbstractThermal degradation of polymethacrylic ester containing bisphenol‐S, poly(BPS‐M), was investigated under nitrogen and air atmosphere at various heating rates. Ozawa's method was used to calculate the kinetic parameters, activation energy, preexponential factor and reaction order. Thermodegradation of the polymer occurs in one or two stages in nitrogen and air, respectively. The temperature at the start of intense degradation (Tstart) and the temperature corresponding to a 50% mass loss (T50%) were found to be 300 and 402°C, respectively, at a heating rate of 10°C min−1 in nitrogen. Larger sample masses have a larger temperature interval (ΔT) and a greater mass loss (ΔW). The kinetic order of degradation is unity both in nitrogen and air. The direct pyrolysis mass spectrum of the polymer shows one degradation peak. The most important degradation process under inert atmosphere is the loss of carbon dioxide, phenol and sulphur dioxide. A possible mechanism for thermal decomposition of poly(BPS‐M) is proposed based on the product analyses.
Filled interpenetrating networks: their formation and viscoelastic properties
Authors: Lipatov Yu. S. , Alekseeva T. T. , Rosovitsky V. F. , Babkina N. V. 
Published: April 2003

AbstractThe kinetics of curing, the microphase separation process (MPS) and the viscoelastic properties of interpenetrating polymer networks (IPNs) based on crosslinked polyurethane and linear poly(butyl methacrylate) were studied in the presence of two fillers—talc and polymeric fine‐disperse triethylene glycol dimethacrylate. It was found that introducing filler into the reaction mixture changes the reaction kinetics and degree of microphase separation, which in turn affects the viscoelastic properties of the IPNs. The data obtained by dynamic mechanical spectroscopy and differential scanning calorimetry for filled semi‐IPNs and calculations of the degree of segregation of the components show that filler introduction results in MPS inhibition on account of a local increase in viscosity near the solid interface, i.e. compatibility is increased.
Effects of interfacial adhesion on microdamage and rheological behaviour of glass bead filled nylon 6
Authors: Ou Yu‐Chun , Yu Zhong‐Zhen 
Published: April 2003

AbstractModel composites consisting of glass beads dispersed in a matrix of nylon 6 with different degrees of interfacial adhesion were prepared. The effects of interfacial adhesion on damage generation in the glass bead filled nylon 6 were studied by acoustic emission monitoring and scanning electron microscopy, and the critical damage stress was measured. Improvement of the interfacial adhesion enhanced the tensile strength of the composite. The melt rheological behaviour of the glass bead filled nylon 6 was also investigated. It was found that the interfacial adhesion strength significantly affected the rheological behaviour of the glass bead filled nylon 6.
Plasma polymerization of some silicon‐ and tin‐containing monomers
Authors: Akovali Güneri , Rzaev Zakir M. O. , Mamedov Dadash H. 
Published: April 2003

AbstractPlasma polymerization of several selected saturated and unsaturated silicon‐ and tin‐containing monomers, such as vinyltriethoxysilane (VTES), 3‐aminopropyltriethoxysilane (APTS), hexamethyldisiloxane (HMDS), hexabutyldistannoxane (HBDS) and tetraethylstannane (TES), were examined in terms of the following selected plasma operational parameters: discharge time (t), flow rate of monomer (F) and power input (W). For the initial deposition rates (DR), the following empirical equation was proposed: DR = k ta Fb Wc, from which the experimental values of the kinetic power factors (a,b,c and k) were calculated. The value of k calculated for VTES was the highest, indicating the high activity of the monomer in plasma in contrast to HBDS, which was about two orders of magnitude smaller. A modified Arrehnius equation was employed in the form of yield of deposition (DR/F) versus the specific energy (W/F), which showed that silicon‐containing monomers are more active than their organotin analogues in the chosen plasma conditions. Plasma polymers of HMDS, TES and HBDS prepared at low conversions were highly crosslinked and their structures were similar to those of crosslinked poly(dialkylsiloxane) or poly(organostannoxane) while those of VTES and APTS were primarily linear.
The role of disorder in phase transformations in PTFE
Authors: Macturk K. S. , Farmer B. L. , Eby R. K. 
Published: April 2003

AbstractThe transformation of PTFE from phase II to phase IV at 19°C and atmospheric pressure has been investigated using wide angle X‐ray diffraction. Diffraction patterns were taken as a function of temperature. The integrated intensity of an equatorial peak present only in phase II was used to monitor the extent of the transformation. Peaks on the second and fifth layer lines were used to determine the effect of transformation and/or disorder. Integrated intensities on these three layer lines were shown to decrease differently with increasing temperature. The decrease in intensity on the second and fifth layer lines could be described in terms of a model comprising the initial integrated intensity, fraction transformed and the amount of rotational disorder present. Molecular modeling also was used to investigate the transformation. A commercially available force field was modified to represent the equilibrium solid state of PTFE. The modified force field was used to examine aspects of the transformation including the influence of neighboring molecules on the molecular conformation.
Novel anionic polymerization of β‐lactones mediated by alkali metal supramolecular complexes
Authors: Jedliński Zbigniew , Kurcok Piotr , Kowalczuk Marek 
Published: April 2003

AbstractThe anionic polymerization of β‐lactones mediated by supramolecular complexes of alkali metal alkoxides and naphthalenides is demonstrated. The novel chemistry of the initiation and the propagation steps of polymerization is discussed.
A study on the hydrated acrylic polymers
Authors: Kim B. C. , Min B. G. , Son T. W. , Lee C. J. 
Published: April 2003

AbstractThe effect of chemical composition of copolymers of acrylonitrile (AN) and methylacrylate (MA) on the hydration and thermal transition behaviour was investigated. An increase of the MA content considerably depressed both Tm and Tc of the hydrated polymers. A double melting and crystallization transition behaviour was observed when the hydrated polymer was reheated after cooling from the molten state. The separation between primary and secondary peaks was more notable in the second heating scan than in the first heating scan. A novel solid‐state transition was observed in the dried acrylic polymers which had experienced hydration and melting in the wet state, followed by drying in the open state at 200°C.
Functionalization of polyethylene using borane reagents and metallocene catalysts
Authors: Chung T. C. , Lu H. L. , Li C. L. 
Published: April 2003

AbstractA new method to prepare functionalized polyethylene involving borane intermediates and transition metal catalysts is described. Two processes, direct and post polymerizations, were employed to prepare borane‐containing polyethylene (PE‐B), which can be transformed to functionalized polyethylene (LLDPE‐f) with various functional groups, such as BR2, OH, NH2, OSi(CH3)3. In the direct process, the PE‐B copolymers were prepared in one step by copolymerization of ethylene with a borane monomer (ω‐borane‐α‐olefin). The post polymerization process requires two steps: copolymerization of ethylene and 1,4‐hexadiene, and subsequential hydroboration reaction of unsaturated PE. Three transition metal catalysts, including two homogeneous metallocene (Cp2ZrCl2[bis(cyclopentadienyl) zirconium dichloride] and Et(Ind)2ZrCl2[1,1′‐ethylenedi‐η5‐indenyl‐zirconium dichloride] with MAO (methylaluminoxane)) and one heterogeneous (TiCl3·AA/Et2AlCl) ones, were studied in the copolymerization reactions. The single site Et(Ind)2ZrCl2/MAO homogeneous catalyst, with a strained ligand geometry and opened active site, is by far the most effective system in the incorporation of high olefins into polyethylene structures.
Phase structure, morphology and phase boundary diagram in an aromatic polyimide (BPDA–PFMB)/m‐cresol system
Authors: Park Jae‐Young , Kim Doyun , Harris Frank W. , Cheng Stephen Z. D. 
Published: April 2003

AbstractAn organo‐soluble aromatic polyimide has been synthesized from 3,3′, 4,4′‐bis(phenyltetracarboxylic) dianhydride (BPDA) and 2,2′‐bis (trifluoromethyl)‐4,4′‐diaminobiphenyl (PFMB) via a one‐step polymerization in m‐cresol. The phase boundary diagram for this system has been established by differential scanning calorimetry, polarized light microscopy (PLM) and wide angle X‐ray diffraction (WAXD) experiments. A crystallosolvate form I has been found over the entire concentration region at low temperatures. When the temperature is increased, an isotropic phase has been observed below concentrations of about 40%. In the relatively high concentration region between 45 and 95%, a transition from the crystallosolvate from I to a crystallosolvate form II has been observed. Form II exhibits a different WAXD pattern. In a narrow concentration region between the isotropic and the crystallosolvate form II (40–45%), a biphase behavior has been found. The birefringence of this region may be an indication of a liquid crystalline phase. The BPDA–PFMB polymer crystal has been found in the very high concentration region (>95%) for temperatures >250°C. The morphologies of these phases have been investigated via PLM and transmission electron microscopy. Above the gel/sol transition temperature, the form I shows negative birefringent spherulites consisting of thin lamellae. The form II exhibits a tendency of positive birefringent spherulites. Possible mechanisms of the formation of the metastable phase morphology and their associations with the mechanical gel/sol transition are also discussed.
On the triple melting behaviour of poly(ethylene succinate)
Authors: Al‐Raheil Ismail A. , Qudah Ali M. A. 
Published: April 2003

AbstractThe morphology of melt‐crystallized poly(ethylene succinate) (PES) was investigated by optical microscopy and scanning electron microscopy, and the melting behaviour of PES was studied by differential scanning calorimetry (DSC). At low crystallization temperature imperfect crystals were formed which could melt and recrystallize during the DSC scan. Triple melting peaks were observed, and the melting behaviour was strongly dependent on crystallization time and scan rate. It was observed that crystallization at high temperature perfected the crystals (dominant and subsidiary lamellae in the spherulitic structure). Increasing the scan rate reduced the chance for reorganization. However, at high crystallization temperature two melting peaks were observed. The material formed was much more perfect, so that the melting process was not dominated by recrystallization. Accordingly, the cause of dual melting is the existence of two kinds of crystal perfection.
Effect of high temperatures on the dielectric behaviour of viscose fibres at low frequency
Authors: Moteleb M. M. Abdel , Saad G. R. 
Published: April 2003

AbstractCommercial and purified viscose fibres exhibit dielectric dispersion and a loss peak within the frequency range 0.05–1 k c/s and at temperatures of 80–140°C. Such high temperature relaxation is local in nature and is attributed to side group motion. The characteristics of the absorption bands of these samples are compared and the results obtained are interpreted. The variation of the dielectric constant with temperature showed a second order transition at about 110°C with these samples, which disappears on hydrolysis.
H‐complex formation and influence on the radical copolymerization of acrylic acid and 1‐vinyl‐2‐pyrrolidone in tetrahydrofuran
Authors: Georgiev George S. , Koseva Nely S. , Christov Latchezar K. 
Published: April 2003

AbstractThe association constant of the H‐complex formation between acrylic acid and 1‐vinyl‐2‐pyrrolidone in tetrahydrofuran at 22°C (K1 = 1350 mol 1−1) was determined by means of 1H NMR spectroscopy. A detailed equation for the copolymer composition, accounting for the participation in the chain propagation of the above complex and that between acid and solvent molecules, was derived. It was used for evalution of the relative reactivities of the complexes discussed and of the uncomplexed 1‐vinyl‐2‐pyrrolidone molecules.
Polyurethanes from renewable resources. IV–properties of linear, crosslinked and segmented polymers from polytetrahydrofuran diols and their glucosides
Authors: Donnelly Michael J. 
Published: April 2003

AbstractVarious types of polyurethanes were synthesised from two classes of polyols: (i) 1,4‐butane diol or selected polytetrahydrofuran (PTHF) diols of different average molecular weights in the range ∼300–2300; (ii) mono‐ or bisglucosides derived from each of these diols. Linear or crosslinked polymers were prepared by reaction with diphenylmethane diisocyanate (MDI) and the properties of polymers from each class of polyol were compared. Higher PTHF molecular weights produced better properties for the diol based materials whereas lower (parent) PTHF molecular weights favoured the glucoside based materials. Segmented polymers were prepared from reaction with MDI and the chain extender ethylene glycol (EG). Manipulation of the cure conditions and hard block concentration produced materials of widely differing properties. At certain hard block concentrations and using rapid (high temperature) curing the glucoside based materials were (i) superior in properties to the diol based materials and (ii) had similar properties to commercial reaction injection moulding polyurethanes.
Studies on the process and products of multimethacrylate polymerisation
Authors: Jantas Roman , Połowiński Stefan , Strobin Grażyna 
Published: April 2003

AbstractFree‐radical polymerisation of multimethacrylate‐poly(2‐methacryloyloxyethyl methacrylate)—in dilute dioxan solutions was examined. The effects of the multimethacrylate molecular weight and the multimonomer concentration on the polymerisation rate and molecular weight distribution and molecular weights of the polymerisation products were determined. The extent of conversion of double bonds in multimethacrylate was determined by FTIR spectrometry, while the molecular weight distributions were determined by gel permeation chromatography. The effect of the parameters under investigation on the template mechanism of the multimethacrylate polymerisation is discussed.
Studies on permeation through polymer latex films, III. Modification using soluble polymeric additives
Authors: Steward Paul A. , Hearn John , Wilkinson Michael C. 
Published: April 2003

AbstractThe influence of two distinct types of water leachable polymeric additives upon the transport properties across polymer latex films is considered. Hydroxypropyl methylcellulose, added as an aqueous solution, and a methyl methacrylate–methacrylic acid copolymer, added as latex particles, are both shown to be more effective than lower molecular weight rapidly water soluble additives, typified by sucrose, in enhancing solute transport and creating pathways for convective diffusion.
Sorption and desorption of water vapour by membranes of the polyelectrolyte complex of chitosan and carboxymethyl cellulose
Authors: Peniche‐Covas C. , Argüelles‐Monal W. , San Román J. 
Published: April 2003

AbstractSorption of water vapour by chitosan/carboxymethyl cellulose polyelectrolyte complex membranes prepared at two different pHs was studied. A linear dependence of the water uptake (W) on time was observed for W values lower than 0.5 g of water per gram of membrane. For higher values of W diffusion becomes controlled by the relaxation of the chains, and second‐order kinetics is observed. An equation that satisfactorily reproduces this behaviour is proposed. Desorption experiments were carried out at different temperatures and the W versus time curves obtained exhibited the same general pattern and were also adjusted by this equation. The approximate average diffusion coefficients were evaluated at each temperature and the apparent activation energy for the diffusion process is reported.
Investigation of pH‐sensitive drug delivery system of chitosan/gelatin hybrid polymer network
Authors: Yao Kang De , Yin Yu Ji , Xu Mei Xuan , Wang Yu Feng 
Published: April 2003

AbstractA novel hydrogel based on a crosslinked chitosan/gelatin with glutaraldehyde hybrid polymer network was prepared. The gel swells in acidic medium and deswells in alkaline medium. A comparative study of the pH‐dependent release of levamisole, cimetidine and chloramphenicol was carried out.
Surface plasticisation of nylon 6,6 by water
Authors: Stuart Barbara , Briscoe Brian 
Published: April 2003

AbstractTribological studies have been carried out on Nylon 6,6 with particular emphasis placed on the examination of the effect of water on this polymer. An examination of the sliding frictional behaviour of Nylon 6,6 against a steel substrate shows that the friction decreases with increasing load, probably due to the formation of thermally softened interfaces in the contact. After exposure of this polymer to water, dramatic changes to the frictional behaviour of the Nylon are observed; the friction increases with increasing load. From the application of the adhesion model of friction it is postulated that the observed changes are caused by extensive plasticisation of the Nylon and, as a consequence, an increase in the contact area. This proposition is confirmed by the reported scratch hardness data. After treatment with water the scratch friction mechanism changes significantly and a notable reduction in the hardness of Nylon is observed.
Direct radiation grafting of acrylic acid to nylon‐6 fabric and the behaviour of the resulting graft copolymer
Authors: El‐Naggar A. M. , El‐Salmawi K. , Ibraheim S. M. , Zahran A. H. 
Published: April 2003

AbstractThe role of certain cations as homopolymer inhibitors in the direct radiation grafting of acrylic acid to nylon‐6 fabric was investigated. The grafting solution was methanol and water at a ratio of 30 : 70 vol%. The maximum graft yield was obtained at 0·08 wt% when using Fe2+ and at 0.7% for Fe3+. In addition, the graft yield obtained with the latter ion was higher than that for the former. Moreover, the presence of Na+ and K+ salts in concentrations as low as 0·1 wt% caused an increase in the graft yield. The hydrophilic properties investigated indicated that the water absorption of nylon‐6 fabric after 9 days increased by 44 times after grafting with poly(acrylic acid) at 166% graft yield. This ratio became 123 times, when this graft copolymer was transformed to the sodium salt. These ratios became 105 and 490 times for the corresponding recrystallized forms, respectively. A study was made to gain a better understanding of the observed super water absorption using SEM and DSC analysis. SEM micrographs of the recrystallized copolymer indicated the formation of large pores with a dendritic structure. Moreover, DSC showed a decrease in both the heat of fusion and melting point. The grafted nylon‐6 fabric showed a noticeable affinity for different dyestuffs.
Transient and thermally stimulated depolarization currents in polyvinyl formal films
Authors: Khare P. K. , Chandok R. S. 
Published: April 2003

AbstractTransient currents in double‐sided vacuum aluminized polyvinyl formal (PVF) film samples of thickness 40 μm were investigated in the charge and discharge modes at different temperatures and fileds. The results observed suggest that the transient currents are governed by charge injection processes leading to space charge effects. Comparative studies of the isochronal characteristics (i.e. current–temperature plots at fixed times) with the thermally stimulated discharge current (TSDC) indicated a strong resemblance between the two techniques. These studies suggest that the simultaneous mechanism of movement of charges through microscopic distances coupled with dipolar orientation may be responsible for the TSDC peak observed at 100°C.
Kinetic study of a radical scavenging effect of hyaluronic acid
Authors: Tokita Yuichi , Sakashita Hiroshi , Okamoto Akio , Kubota Kenji 
Published: April 2003

AbstractThe rate of the scavenging reaction of hyaluronic acid with hydroxyl radicals was investigated by means of competitive reaction with 4‐nitrosodimethylaniline. It was found that the reactivity of hyaluronic acid with hydroxyl radicals depends on both the molecular weight and the concentration of hyaluronic acid. These features were accounted for by the characteristic molecular properties of hyaluronic acid in solution.