bluuebunny/crossref_metadata_2025_split huggingface dataset:
Settling characteristics of microparticles modified by hydrophilic semi‐interpenetrating polymer networks
Authors: Degrazia Janet L. , Bowman Christopher N. 
Published: April 2003

AbstractMicroparticles of 2‐hydroxyethyl methacrylate cross‐linked with ethylene glycol dimethacrylate were produced by suspension polymerization. Semi‐interpenetrating polymer networks were prepared by diffusion of poly(ethylene oxide) (PEO) solution into the particles. The PEO was allowed to diffuse into the dried particles and the resulting swollen particles were treated with an excess of acetone to collapse them. The ensuing networks consisted of the collapsed particles and the trapped PEO. The modified particles were allowed to settle in water, and characteristic settling times were measured as a function of swelling time. The settling times were compared to those of the unmodified particles. It was found that the settling time changes with volume fraction, particle size, degree of functionality, and amount of swelling. An increased volume fraction in both unmodified and modified particles causes a slower settling rate. The smaller particle sizes fall more slowly, and size difference plays a more significant role in hindering the settling for lower amounts of trapped PEO. As the amount of PEO increases, the settling rate decreases dramatically. Swelling also slows the settling rate, until the particles reach equilibrium. Equilibrium swelling occurs near 10 min for both unmodified and modified particles. Optical photo‐microscopy verified the amount of swelling and demonstrated the process of PEO penetration. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of block copolymers from D,L‐lactide and poly(tetramethylene ether glycol)
Authors: Xiong C. D. , Cheng L. M. , Xu R. P. , Deng X. M. 
Published: April 2003

AbstractThe copolymer from D,L‐lactide and poly(tetramethyene ether glycol) (PTMG) was prepared in bulk with an isotributyl aluminum–water–phosphoric acid complex catalyst as the initiator and characterized by H‐NMR, GPC, and DSC. The effects of the temperature and the amount of PTMG on the polymerization rate and the molecular weight of copolymers were studied. The behavior of the degradation and delivery rate of Levonorgestrel microspheres in vitro was observed. The results show that the degradation and the delivery rate can be controlled by adjusting the molar rate of hydrophilic and hydrophobic segments of the copolymer © 1995 John Wiley & Sons, Inc.
Study of miscibility of poly(vinyl acetate) and poly(vinyl alcohol) blends by fluorescence spectroscopy
Authors: Dibbern‐Brunelli D. , Atvars T. D. Z. 
Published: April 2003

AbstractSecondary relaxation of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and their blends in different proportions (9 : 1, 1 : 1, and 1 : 9) were studied by photoluminescence of anthracene, fluorescein, and both probes dissolved in the polymer blends. The temperature of the glass transition in the homopolymers was determined by the radiationless deactivation of anthracene as Tg(PVAc) ≅ 304 K and the photobleaching of fluorescein as Tg(PVA) ≅ 350 K. The relaxation processes of the different phases of the polymer blends occur at temperatures close to the homopolymers, which may be explained by the localization of each molecular probe within the matrix. These deactivation curves, however, are not similar to those of the individual homopolymers, suggesting a partial miscibility between these polymers. © 1995 John Wiley & Sons, Inc.
Optimal temperature for the control of the product quality in batch polymerization: Simulation and experimental results
Authors: Scali Claudio , Ciari Roberto , Bello Tiziana , Maschio Giuseppe 
Published: April 2003

AbstractA method to determine an optimal temperature profile that guarantees products having controlled molecular weight distribution (MWD) and desired values of molecular weight (Mw) is presented. The base case is the batch polymerization of MethylMethAcrylate, initiated by AIBN. On the basis of the kinetic model, the optimal temperature profile is determined by imposing that the value of the instantaneous chain length is maintained constant, thus counteracting the effects of the increase of viscosity, which leads to broad MWD. Some approximations permit to express, in a straightforward way, the relationship between the optimal temperature and the conversion as a function of the initial conditions. The validity of the simplifying hypotheses that have been assumed is confirmed first by simulation results and then by a comparison with experimental runs conducted in a labscale unit, with determination of MWD made by means of GPC. The obtained results suggest that it is possible to decouple the problem: acting on the operating temperature to control the MWD, acting on initial temperature and initiator concentration to influence the Mw. The possibility of application to industrial reactors has also been investigated, taking into account their peculiarities and constraints. © 1995 John Wiley & Sons, Inc.
Transcrystalline growth of thermoplastics and LCPs during isothermal crystallization
Authors: Huang Y. , Petermann J. 
Published: April 2003

AbstractTwo technical methods were developed for transcrystalline growth in order to create perfect transcrystalline growth for both thermoplastics and liquid crystalline polymers. A principle was suggested for oriented crystallization that the nucleation is created with high density along a one‐dimensional or on a two‐dimensional unit, while the nucleation in the matrix is suppressed. The steric hindrance was a key factor to create the transcrystalline growth in isothermal crystallization. © 1995 John Wiley & Sons, Inc.
Fractionation of reactive perfluoropolyoxyalkylene oligomers
Authors: Levi Marinella , Turri Stefano 
Published: April 2003

AbstractFractional distillation, solubility fractionation, and column chromatographic separation have been applied in the study of fractionation of perfluoropoly(oxymethylene‐co‐oxy‐ethylene) oligomers with CH2OH end units, containing mono and bifunctional species. With a suitable choice of conditions, all three techniques proved to be useful for the preparation of fractions with narrow molecular weight distribution. Column chromatography allowed the separation of fractions having, in addition, sharp mono and bifunctionality. On the bsis of the experimental results, general indications for designing reactive oligomers fractionation procedures are discussed, prevalently centered on the copolymer end effect, which is typically present in this kind of compound. © 1995 John Wiley & Sons. Inc.
An extension of the penalty function formulation to incompressible hyperelastic solids described by general measure of strain
Authors: Kakavas P. A. , Chang W. V. 
Published: April 2003

AbstractThe penalty function formulation for incompressible hyperelastic solids was first proposed about 30 years ago. Since then all studies have been limited to invariant type formulation of the strain energy function, although it is well known that this formulation does not correctly describe the behavior of a real material. On the other hand more realistic constitutive equations, based on general measures of the strain only, have been incorporated to mixed finite element algorithms. In this article, a penalty function formulation is proposed for the analysis of stress field in materials with constitutive equations based on the general measure of strain. The reduced integration method is used to weaken the penalty constraint in order to obtain meaningful numerical results. The incremental equilibrium equations are solved using the regular Newton–Raphson algorithm. The method is applied to evaluate the stress field in materials subjected to plane strain conditions. Satisfactory agreements have been obtained with analytical solutions when available. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of negative photosensitive polysiloxaneimide
Authors: Zhu Pukun , Li Zuobang , Feng Wei , Wang Qiang , Wang Lixin 
Published: April 2003

AbstractA photosensitive polysiloxaneimide precursor was synthesized from oxydianiline, bis(p‐aminophenoxy)dimethylsilane, and a diacid chloride. This diacid chloride was prepared by the reaction of thionyl chloride with a diacid, which resulted from the reaction of pyromellitic dianhydride with hydroxyethylacrylate in N‐methylpyrrolidone (NMP). The adhesion properties between polyimide and substrates such as SiO2 wafer were improved with introduction of siloxane moiety into the polyimide chain. The dielectric constant decreased with increasing siloxane moiety content. The photocrosslinking reaction results show that an 88–90% gel fraction was reached under the irradiation of a high‐pressure mercury lamp. © 1995 John Wiley & Sons, Inc.
Bilayer thin‐film composite membranes for air separation
Authors: Huang Mei‐Rong , Li Xin‐Gui , Chen Guan‐Wen 
Published: April 2003

AbstractBilayer composite membranes suitable for separating air, consisting of poly(4‐methylpentene‐1) (PMP) thin film as a selective top layer, an ethylcellulose–heptycellulose (ECHC) blend thin film as a selective sublayer, and polysulfone as a porous support, were investigated using a constant pressure–variable volume method. By varying operating temperature, pressure, time, as well as stage cut, the membranes were characterized for their oxygen enriched air (OEA) flux and oxygen concentration in the OEA permeated in a single step. The results show that both the OEA flux and oxygen concentration through the membranes increase with increasing operating pressure. With the increase of operating temperature, the OEA flux increases largely but the oxygen concentration decreases slightly. The oxygen concentration also decreases slightly with the stage cut. On the contrary, the OEA flux decreases and oxygen concentration increases slightly with operating time. It is found that a PMP thin film plays an important role in enhancing the air‐separation capability of the membrane. The PMP/ECHC bilayer thin‐film composite membrane could enrich the OEA containing 43.6% oxygen at the OEA flux of 5.06 × 10−4 cm3 (STP)/s cm2 with a good performance stability. © 1995 John Wiley & Sons, Inc.
New catalysts for poly(ethylene terephthalate)‐bisphenol a polycarbonate reactive blending
Authors: Fiorini Maurizio , Berti Corrado , Ignatov Vladimir , Toselli Maurizio , Pilati Francesco 
Published: April 2003

AbstractThe effects of various catalysts on the reactive blending of poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) was investigated. The various catalysts employed for PET syntheses, Ti(OBu)4, SmL3, EuL3, Ca + Sb, CeAc3, Er(NO3)3·B12C4 and Tb (acac)3·diPy (where L is o‐formylphenolate; B12C4 is a crown ether, benzo‐12‐crown‐4; acac is acetylacetonate; and diPy is 2,2′‐dipyridyl) have shown a different catalytic activity toward exchange reactions. Solubility tests, in solvents able to separate unreacted PET and PC, and selective degradation of the PC segments, combined with 1H NMR spectroscopy and size exclusion chromatography, made it possible to order the catalysts according to their catalytic activity: Ti(OBu)4 ≫ SmL3 > EuL3 > Ca + Sb > CeAc3∼Er(NO3)·B12C4 > Tb (Acac)3·diPy ≈ 0. © 1995 John Wiley & Sons, Inc.
Study of nylon 6 and poly(propylene oxide) blends by thermal measurements and carbon‐13 NMR high resolution solid‐state
Authors: Tavares Maria Inês Bruno , Castro Washington P. , Costa Dilma A. 
Published: April 2003

AbstractSamples of Nylon 6/poly(propylene oxide), with poly(propylene oxide) (PPO) content varying up to 35%, have been examined using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) carbon‐13 at solid‐state. Carbon‐13 spectra were measured by cross‐polarization (CP), magic angle spinning (MAS), and high‐power hydrogen decoupling (HPHD). The variation contact time experiment and MAS technique were also determined. The data are discussed in terms of compatibility and plasticization of the samples. © 1995 John Wiley & Sons, Inc.
Structure and mechanical properties of the compositions of polyisocyanurate polymers with low molecular weight rubbers
Authors: Askadskii Andrei A. , Shvorak Alexander E. , Frenkel Tsylia M. , Babtschinitzer Tatyana M. , Bychko Capitolina A. , Kovriga Oleg V. , Pankratov Viatscheslav A. , Rajulu A. Varada 
Published: April 2003

AbstractThe structure and properties of the compositions of polyisocyanurates modified with low molecular weight rubber networks have been investigated by means of dynamical mechanical analysis (DMA), electron microscopy, and stress‐relaxation experiments. The network compositions consist of two different polymeric networks. The first component (macrodi‐isocyanate based on low molecular weight polybutadiene or copolymers of tetrahydrofuran and propylene oxide) has bulky cross‐linked points connected by short flexible chains. The second component (diphenylmethanediisocyanate) also has bulky cross‐linked points of the same structure, but the linear fragments between them in this case are very small and rigid. These compositions result in the formation of the heterophase system. As a result, transparent samples were prepared, which differ from the mechanical properties of both the glassy and rubbery polymers. These materials have a modulus of elasticity (from 103 to 10 MPa) that is usual for the transition zone between the glassy and rubbery states; nevertheless, these materials show elastic (and not viscoelastic) properties. For the materials investigated, the modulus is decreased not more than 10 times in the wide temperature interval from 200 to 500 K. A new state of the polymer, which differs from both the glassy and rubbery states, has been identified in the present case. © 1995 John Wiley & Sons, Inc.
Release of radioactive steroids from dried down hydrogels of polyurethane networks
Authors: Zulfiqar M. , Quddos A. , Zulfiqar S. 
Published: April 2003

AbstractThe polyurethane networks were based on poly(ethylene glycol) 6000 (PEG), crosslinked with 1,1,1‐tris(hydroxy methyl)ethane and with the stoichiometric equivalence of hexamethylene diisocyanate. Radioactive steroids were incorporated into cylindrical hydrogels over a wide range of compositions. The release profiles were drawn from dried down hydrogel of polyurethane networks. The scintillation counter was used for the release study of steroids after different intervals. In vivo, the loaded hydrogels were implanted into rats. The results for constant release studies were recorded. © 1995 John Wiley & Sons, Inc.
Molecular transport of alkanes through thermoplastic miscible blends of ethylene–propylene random copolymer and isotactic polypropylene
Authors: Aminabhavi Tejraj M. , Phayde Hemant T. S. 
Published: April 2003

AbstractA new experimental protocol based on the measurements of sorption (S), desorption (D), resorption (RS), and redesorption (RD) has been used to study the molecular transport of aliphatic alkanes through the miscible blends of an ethylene–propylene random copolymer and an isotactic polypropylene over the temperature interval 25–70°C. Diffusion and activation parameters are evaluated and their dependencies on solvent size, shape, and nature are discussed. Estimated values of the molar mass between chain entanglements, kinetic rate constants, and overshoot index parameters have been influenced by the polymer–solvent interactions. The sorption–diffusion mechanism is found to be of anomalous type. © 1995 John Wiley & Sons, Inc.
In‐plane shearing stress–strain response of glass‐fiber‐reinforced composites as determined from four‐point bending tests
Authors: Sideridis E. , Kyriazi E. 
Published: April 2003

AbstractIn this article an experimental study to determine the longitudinal (or in‐plane) shearing stress–strain response of a unidirectional fiber‐reinforced composite material is presented. The test method used is the four‐point blending of a ±45° off‐axis glass‐fiber‐reinforced laminate. Although a laminate is used for the investigation of the shearing stress–strain response, it is shown that unidirectional shear properties can be found from the laminate test data following a procedure analogous to that used in previously. Also, the 45° off‐axis test of unidirectional composite in bending was carried out to obtain the in‐plane shear modulus and compare it with that obtained by the ±45° off‐axis method. Finally both values were compared with the theoretical value of the in‐plane shear modulus obtained from a theoretical formula where the concept of boundary interphase between fiber and matrix was introduced. © 1995 John Wiley & Sons, Inc.
Structure and mechanical properties of heterogeneous polymer blends
Authors: Kozlowski M. 
Published: April 2003

AbstractMaterial response under uniaxial stress has been reported for heterogeneous systems: low density poly(ethylene)–poly(styrene). The ystems differed in a component ratio and in a content of the macromolecular modifier type compatibilizer. Tensile properties have been determined for the systems in a molten state (473 K) and below Tg as a function of elongation rate. The modifier which diminishes the interfacial tension is advantageous for mechanical properties of the system—both in the melt and the solid state. The differences in mechanical characteristics have been related to a specific phase structure of polymer systems. © 1995 John Wiley & Sons, Inc.
Adhesive properties of DGEBA–acid homopolymer and DGEBA–acid copolymer systems
Authors: Laref F. Heba , Mouzali M. 
Published: April 2003

AbstractAdhesive properties of high molecular weight acid copolymers used as hardeners for a commercial epoxy resin are investigated. For comparative purposes, physical blends of poly(acrylic acid)–polystyrene are used as hardeners. Joints prepared from physical blends exhibit lower lap shear strength than do those prepared form synthesis products. The use of copolymers is more adequate. Thermodynamic work of adhesion using wettability criteria is explored to explain the differences. The apparent energies of rupture determined by lap shear tests are 103 higher than those of the thermodynamic work of adhesion. © 1995 John Wiley & Sons, Inc.
Monodisperse poly(butadiene/styrene) particles by dispersion polymerization
Authors: Hu R. , Dimonie V. L. , Sudol E. D. , El‐Aasser M. S. 
Published: April 2003

AbstractExperimental conditions for preparing monodisperse, micron‐size poly(butadiene/styrene) particles by dispersion polymerization were investigated. After some initial recipe development, the following variables were fixed: butadiene/styrene weight ratio (90/10), dispersion medium (ethanol), polymeric stabilizer [poly(vinyl pyrrohdone), K‐30], costabilizer (sodium dioctyl sulfosuccinate), initiator (2,2′‐azobisisobutryonitrile), and polymerization temperature (70°C). The primary process variables investigated were the monomer/ethanol ratio (M/S), the rpm of the bottle polymerizer, and the amount of free space (FS) in the polymerization bottles. The particle size varied from 0.77 to 1.8 μm and was found to increase with increasing M/S and rpm, and decreasing FS. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of a new degradable thermoplastic elastomer based on 1,5‐dioxepan‐2‐one and ε‐caprolactone
Authors: Lofcren A. , Renstad R. , Albertsson A.‐C. 
Published: April 2003

AbstractA new, highly elastomeric ABA triblock copolymer made from ω‐caprolactone (ε‐CL) and 1,5‐dioxepan‐2‐one (DXO) has been synthesized by sequential addition of the comonomers in THF or toluene solution initiated by aluminum isopropoxide. Careful purification of the comonomers was essential to obtain high conversion of the final amount of the added monomer. The optimal conditions were found to be polymerization in toluene solution at 25°C with the addition of 1 molar equivalent (with respect to initiator) of pyridine, which gives a slight increase in the rate of polymerization. Under these conditions, poly(ε‐CL‐b‐DXO‐b‐ε‐CL) triblock copolymers of high molecular weight (Mn > 105 g/mol) with a relatively narrow molecular weight distribution were obtained. Thermal analysis shows a melting peak at 51°C and a glass transition at ca. −38°C, corresponding to the PCL block crystalline phase and the PDXO amorphous region, respectively. The mechanical properties of these materials are highly elastic and can be varied by tailoring the block lengths of the corresponding comonomers. Tensile modulus, tensile strength at break, and elongation at break were found to be 20–30 MPa, 50 MPa, and ca. 1000%, respectively. © 1995 John Wiley & Sons, Inc.
Kinetic study on simultaneous interpenetrating polymer network formation of epoxy resin and unsaturated polyester
Authors: Lin Mu‐Shih , Chang Reui‐Je , Yang Timothy , Shih Yen‐Fong 
Published: April 2003

AbstractSimultaneous interpenetrating polymer networks (SIN) based on diglycidyl ether of bisphenol‐A (DGEBA) and unsaturated polyester (UP) in weight ratios of 100/0, 50/50, and 0/100 were blended and cured simultaneously by using cumene hydroperoxide (CHP) and m‐xylenediamine (MXDA) as curing agents. A kinetic study during SIN formation was carried out at 43, 53, 58, and 64°C. Concentration changes for both epoxide and CC bond were monitored with Fourier transform infrared (FTIR). Rate expressions for epoxide polymerization were established with model reactions for phenyl glycidyl ether (PGE) and benzylamine in dichloroethane containing benzyl alcohol. Experimental results revealed that a lower cure rate constant for the CC bond during SIN formation was found, compared with pure UP network formation. A model of network interlock is proposed to account for this phenomenon. During simultaneous cure of DGEBA and UP, the network interlock should provide a sterically hindered environment, which subsequently retards cure rate for UP. On the other hand, epoxide cure during SIN formation indicates higher rate constants for both uncatalyzed and catalyzed reactions, compared with those of pure DGEBA cure. Presumably the catalytic effect of hydroxyl end groups in UP overcomes the effect of network interlock. Kinetic parameters were calculated and are discussed. © 1995 John Wiley & Sons, Inc.
Miscibility and complexation behavior of poly(cyanomethyl methacrylate) and poly(2‐cyanoethyl methacrylate) with tertiary amide polymers
Authors: Yeo Y. T. , Lee S. Y. , Goh S. H. 
Published: April 2003

AbstractThe miscibility and complexation behavior of poly(cyanomethyl methacrylate) (PCYMMA) and poly(2‐cyanoethyl methacrylate) (PCYEMA) with various tertiary amide polymers was studied. PCYMMA and PCYEMA form interpolymer complexes with poly(N‐methyl‐N‐vinylacetamide) (PMVAc) or poly(N‐vinyl‐2‐pyrrolidone) (PVP) in tetrahydrofuran (THF) solutions. PCYMMA also forms complexes with poly(N,N‐dimethylacrylamide) (PDMA) in THF solutions. However, PCYEMA does not form complexes with PDMA in THF solutions, but the THF‐cast blends are miscible over the entire composition range. Both PCYMMA and PCYEMA do not form complexes with poly(2‐ethyl‐2‐oxazoline) (PEOx) in THF solutions and are only miscible with PEOx when the blend contains greater than 60 wt % PCYMMA or 80 wt % PCYEMA. On the other hand, both PCYMMA and PCYEMA do not form complexes with PMVAc, PVP, or PDMA in N,N‐dimethylformamide (DMF) solutions. The compositions of the complexes consist of simple mole ratios of the component polymers, and the glass‐transition temperatures of the complexes are higher than those of the DMF‐cast blends of similar compositions. Fourier‐transform infrared spectroscopy provides further evidence on the miscibility behavior through changes in the amide carbonyl absorption bands of each tertiary amide polymer in the blends as well as in the cyano absorption band of PCYEMA. © 1995 John Wiley & Sons, Inc.