bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and rheological behavior in aqueous solutions of poly(acrylamide‐co‐maleic acid)
Authors: Yao Ke‐Jun , Liu Feng‐Hui 
Published: April 2003

AbstractWater‐soluble copolymers of acrylamide with maleic acid were synthesized in aqueous solution by using potassium persulfate with N,N,N′,N′‐tetramethyl ethylenediamine as initiator. The influences of synthetic variables on the copolymerization were investigated. The copolymers were characterized by IR and 1H‐NMR spectroscopy. The copolymeric composition was obtained by using 1H‐NMR method. The monomer reactivity ratios were calculated by the Kelen‐Tudos method and the values of r1 (AM) and r2 (MA) were determined to be 11.45 and 0.0129, respectively. The rheological behavior of aqueous solution of synthetic poly(acrylamide‐co‐maleic acid) was determined, and flowing activation energy E was calculated. © 1995 John Wiley & Sons, Inc.
Effect of some superplasticizers on the mechanical and physicochemical properties of blended cement pastes
Authors: El‐Hosiny F. I. , Gad E. A. M. 
Published: April 2003

AbstractBlended cement pastes made of Portland cement and fine sand (known in Egypt as El‐Karnak cement) were made using a water–cement ratio of 0.25 by weight. Three pastes containing admixture (water‐soluble condensates) were also prepared using a water–cement ratio of 0.25 and condensate (superplasticizer) content of 0.25% by the weight of cement; the superplasticizers used are Na‐phenol sulfonate formaldehyde, Na‐polystyrene sulfonate, and Na‐ß‐naphthol sulfonate formaldehyde condensates. All pastes were cured for various time intervals within the range of 0.02–90 days. Compressive strength tests, hydration kinetics, X‐ray diffraction analysis, thermal analysis, and surface properties were studied and related as much as possible to the pore structure of the hardened pastes. © 1995 John Wiley & Sons, Inc.
Reactive extrusion of PP/natural rubber blends
Authors: Yoon Lee Keun , Choi Chi Hoon , Kim Byung Kyu 
Published: April 2003

AbstractReactive extrusion of polypropylene (PP)/natural rubber (NR) (90/10) blends was conducted in the presence of a peroxide [1,3‐bis(t‐butylperoxy)benzene] and coagent (trimethylolpropanetriacrylate, TMPTA). Effects of peroxide and coagent content were studied in terms of melt index (MI), melt viscosity, morphology, thermal, and mechanical properties. At a constant content of the coagent, melt viscosity increased at a low and decreased at a high content of the peroxide. On the other hand, melt viscosity increased monotonically with the coagent concentration at constant peroxide content. The increase and decrease of viscosity were interpreted in terms of crosslinking and chain scission of PP, which governed the rubber domain size and mechanical properties of the reactive blends. © 1995 John Wiley & Sons, Inc.
Role of bulky polysiloxanylalkyi methacrylates in oxygen‐permeable hydrogel materials
Authors: Lai Yu‐Chin 
Published: April 2003

AbstractPolysiloxanylalkyl methacrylates, such as methacryloxypropyl tris(trimethylsiloxy)silane (TRIS), have been used extensively in rigid gas‐permeable contact lens materials due to their ability to produce high oxygen permeability in the resulting polymeric material. In this study, the role of TRIS was evaluated as a component in silicone hydrogel materials based on polysiloxane‐based prepolymers. It was found that it not only gave high oxygen permeability, but also gave hydrogels with better tear strength and lower modulus. These changes in properties are all favorable for applications such as oxygen‐permeable hydrogel lenses. © 1995 John Wiley & Sons, Inc.
Photoresponsive permeability of polyelectrolyte complex capsule membrane containing triphenylmethane leucohydroxide residues
Authors: Kono Kenji , Nishihara Yasuhiro , Takagishi Toru 
Published: April 2003

AbstractTo develop a functional capsule, which can be controlled to release materials entrapped in the inner aqueous space responding to light, partly crosslinked poly(acrylic acid)–poly‐ethylenimine complex capsules containing a copolymer of acrylic acid and bis[4‐(dimethylamino)phenyl](4‐vinylphenyl)methyl leucohydroxide as an additional membrane component with radii of ca. 3 mm have been prepared. The triphenylmethane derivative on the copolymer dissociated into an ion pair under ultraviolet light irradiation in the weak alkaline region. Permeation of p‐toluenesulfonate through the capsule membrane was enhanced significantly by the photoirradiation after a several minutes time lag under a weak alkaline condition. The photoinduced increase in permeability of the capsule was pH‐dependent. The maximum effect of light on the permeability was observed near pH 8, whereas less enhancement was observed above or below the pH value. When the irradiation of the light was stopped, permeation of the permeant decreased. The photoresponsive permeability change of the capsule membrane can be carried out reversibly. © 1995 John Wiley & Sons, Inc.
Development of an anisotropic conductive adhesive film (ACAF) from epoxy resins
Authors: Asai Shin'ichiro , Saruta Ueki , Tobita Masayuki , Takano Minoru , Miyashita Yasuo 
Published: April 2003

AbstractA thermoset type anisotropic conductive adhesive film (ACAF), which electrically connects an ITO glass and a flex circuit both having conducting pattersn of less than 100 μm in pitch, has been developed. In this development, bisphenol A and bisphenol F epoxy resins were tested to formulate an ACAF with easy‐to‐handle tackiness, flexibility, and strenght. A curing agent that gives fast cure and long shelf‐life properties to the epoxy resin was also selected. The tensile stress–strain responses of obtained adhesive films were successfully used for determining the formulation. Good aftercure physical properties (electrical and mechanical) were obtained. Durability against high temperature and high humidity were also tested to confirm long‐term stability of the conduction of this ACAF. © 1995 John Wiley & Sons, Inc.
Positron annihilation lifetime study of vapor sorption in polypropylene and polytetrafluoroethylene
Authors: Sánchez Victor , López Rafael , Fucugauchi Luz Alicia , Ito Yasuo 
Published: April 2003

AbstractPositron annihilation lifetime (PAL) spectra were measured for two different kinds of polymers: polypropylene (PP) and polytetrafluoroethylene (PTFE), during sorption of vapors of the following molecules: n‐hexane, cyclohexane, benzene, methyl methacrylate, acrylic acid, and water. The behavior of ortho‐positronium (o‐Ps) annihilation parameters: lifetime, τ3, and intensity, I3, can be explained by considering different sorption mechanisms in rubbery and glassy polymers. The mean size of the intermolecular‐space holes and the relative free‐volume fraction of PP and PTFE were estimated before and during the sorption process from the o‐Ps parameters obtained. Sorption of n‐hexane, cyclohexane, and benzene in both polymers affect the o‐Ps component in a systematic way, for PP τ3 and I3 tend to decrease, while in PTFE, τ3 stay almost constant and I3 diminishes. These effects are interpreted in relation to the different states of the polymers studied: rubbery for PP and glassy for PTFE. In case of methyl methacrylate molecules, the behavior of o‐Ps parameters was more complicated. For acrylic acid and water, their associated polarity provokes a diminution in I3, which is explained from the viewpoint of the spur model of positronium formation. Large changes in the mean size and the fraction of free volume, as well as their constant behavior in some cases, were interpreted to be due to positive or negative interactions, respectively, between vapor molecules and PP and PTFE, which could be correlated with the solvent‐interaction parameters calculated. © 1995 John Wiley & Sons, Inc.
Effect of morphology on mechanical and rheological properties of butyl acrylate–methyl methacrylate multiphase polymers
Authors: Canche‐Escamilla G. , Mendizabal E. , Hernandez‐Patiño M. J. , Arce‐Romero S. M. , Gonzalez‐Romero V. M. 
Published: April 2003

AbstractPolymers of butyl acrylate–methyl methacrylate with different morphologies were synthesized by emulsion polymerization. Four types of polymers were obtained: copolymer, core–shell, three layer, and a core–shell with a copolymer layer of variable composition (gradient). The effect of the morphologies on the mechanical and rheological properties of these polymers was studied. It was found that when the same overall composition was used the properties of the polymer can be varied from those of rigid plastic to those of an elastomeric material. It was found that increasing the content of butyl acrylate (BA) improves the mechanical properties and the presence of a copolymer zone improves the impact resistance of the material. © 1995 John Wiley & Sons, Inc.
Thermal characterization of some products obtained by chemically modified poly(vinyl chloride) with phenol
Authors: Cascaval Constantin N. , Robilǎ Gabriela , Stoleriu Aurel 
Published: April 2003

AbstractThe chemical modification of poly(vinyl chloride) (PVC) in reaction with phenol, in the absence of a catalyst and at temperatures within the range of 60°C and the boiling temperature of phenol (180°C), led to the reaction products with the general structure of a vinyl chloride–vinyl phenol copolymer. The synthesized polyphenols were thermally characterized using the following experimental techniques: thermo–optical analysis (TOA), thermogravimetry (TG), derivative thermogravimetry (DTG), and pyrolysis in combination with gas chromatography (P–GC). The PVC samples modified with phenol show a thermal stability lower than the original PVC sample. The glass transition temperatures (Tgs) increase with increased degree of chlorine substitution. The main pyrolysis products of the modified PVC samples are hydrocarbons with low boiling points (C1–C4), benzene, toluene, naphthalene, indan, and phenol. The semiquantitative estimation of the pyrolysis products of the synthesized samples led to the conclusion that the following structural element types can be present, statistically distributed along the chain: vinyl chloride and vinyl phenol units, acetylenic and ethylenic units, and indan type structures. © 1995 John Wiley & Sons, Inc.
Selective crosslinking reaction in polymer blends. III. The effects of the crosslinking of dispersed EPDM particles on the impact behavior of PP/EPDM blends
Authors: Inoue Toshio , Suzuki Tokuhito 
Published: April 2003

AbstractThe selective dynamic crosslinking reaction by means of the N,N'‐m‐phenylene–bismaleimide/poly‐(2,2,4‐trimethyl‐1,2‐dihydroquinoline) system was carried out on PP/EPDM blends and its effect on the Izod impact strength (IIS) was investigated. Three series of PP/EPDM combinations were adopted to establish different morphologies. In each series, the EPDM wt % varied from 5 to 30 at 5 wt % intervals. The system crosslinked the EPDM particles selectively without PP degradation and change of morphology. Following the crosslinking, the IIS at 23, −10, and −30°C increased in all blends, and the critical EPDM wt % at 23°C necessary to cause the dramatic IIS increase was lowered. The increase in interfacial adhesion is considered to be the most important factor necessary for the improvement. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM were also considered to contribute to the improvement in the IIS. Impact fracture energy absorption can thus be changed by adjusting the magnitude of the interfacial adhesion by the dynamic crosslinking even at essentially the same morphology. © 1995 John Wiley & Sons, Inc.
Effect of network structure on thermal and mechanical properties of biphenol‐type epoxy resins cured with phenols
Authors: Ochi M. , Tsuyuno N. , Sakaga K. , Nakanishi Y. , Murata Y. 
Published: April 2003

AbstractIn the biphenol‐type epoxy resin cured with catechol novolac (CN), a very weak glass transition and, thus, a very high rubbery modulus were observed. On the other hand, the glass transition was clearly observed in the system cured with phenol novolac (PN). This means that the micro‐Brownian motion of network chains is highly suppressed in the system cured with CN. The reason for this suppression of the chain motion in the CN‐cured system has been pursued from the viewpoint of the conformation of network chains. The disappearance of the glass transition in the biphenol‐type resin depends on the formation of the active hydrogens in the curing agents. Thus, it was suggested that the suppression of the micro‐Brownian motion is due to the orientation of the biphenyl groups in the network. Moreover, it has been shown that the mechanical and bonding strength at high temperature is considerably improved by the suppression of the network chain motion in the CN‐cured biphenol resin system. © 1995 John wiley & Sons, Inc.
Surface modification of polyimide films by graft copolymerization
Authors: Loh F. C. , Lau C. B. , Tan K. L. , Kang E. T. 
Published: April 2003

AbstractSurface modifications of polyimide (PI) films by Ar‐plasma, O2‐plasma, and O3 pretreatment and by near‐UV light‐induced graft copolymerization with water‐soluable monomers, such as acrylamide (AAm), acrylic acid (AAc), and sodium salt of 4‐styrenesulfonic acid (NaSS), have been carried out. The angle‐resolved x‐ray photoelectron spectroscopy (XPS) results show that surface pretreatment results in the formation of peroxide species on the polymer film surfaces and leads to a substantial enhancement of the density of surface graft. The XPS results further suggest that in the case where substantial grafting has taken place, the grafted polymer either forms a surface layer uniformly intermixed with the substrate chains, or a graft‐rich surface layer in the case of sterically hindered migration of the graft. The resulting surface structures are further supported by dynamic water contact angle measurements. These surface structures are probably associated with the thermoset character of PI, as they differ from the stratified microstructures observed on most thermoplastic films after surface modification by graft copolymerization with hydrophilic monomers. © 1995 John Wiley & Sons, Inc.
Applications of magnetic resonance imaging to ion‐exchange resins
Authors: Wallner Anton S. , Ritchey William M. 
Published: April 2003

AbstractMagnetic resonance imaging (MRI) was used to determine swollen resin morphology in cation–exchange beads. The study of the nonuuniformity of the swelling of cation–exchange beads [sulfonated styrene–divinylbenzene (SDVB) copolymers] is of interest because the exchange kinetics and other properties are expected to be strongly influenced by the swelling. MRI can replace current invasive and destructive methods for studying the morphology of these resins. Several types of ion–exchange resins were examined including beads which exhibit homogeneous swelling, heterogeneous swelling, and partially sulfonated beads. The variation in intensity observed is due to a variation in crosslink density, degree of sulfonation, composition, sulfone bridging, or a combination of these variables. Due to their small size, the beads were also imaged using a small coil insert. Results are compared to commercially available insert images in terms of signal‐to‐noise and experiment time. © 1995 John Wiley & Sons, Inc.
Effects of low‐profile additives on the curing reaction of unsaturated polyester resins
Authors: Sun B. , Yu T. L. 
Published: April 2003

AbstractThe effect of low‐profile additives (LPA), i.e., poly(vinyl acetate) (PVAC) and poly(methyl methacrylate) (PMMA), on the curing reaction of unsaturated polyester (UPE) resins was studied by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The curing reaction profiles were determined by DSC, while GPC was used to investigate the variation of the sizes of microgel particles during the early stage of curing reaction in UPE–styrene resins. The DSC experimental results indicated that the curing reaction rate decreased as the concentration of LPA increased. At a fixed LPA concentration, the curing reaction rate was slower for resins mixed with LPA possessing worse compatibility with UPE resins. During the early stage of curing reaction, the size and structure of the UPE microgels formation strongly depended on the concentration of LPA and also on the compatibility of the components in the curing system. The experimental results of this study revealed that the concentration of LPA and the compatibility of LPA with UPE resins had a strong influence on the polyester microgel formation and the curing behavior. © 1995 John Wiley & Sons, Inc.
Solvent effect on fluorescence lifetimes at swollen glassy–rubber interphase domains in blendlike particles
Authors: Pekcan Önder 
Published: April 2003

AbstractFluorescence of naphthalene (N) labeled to poly(methyl metracrylate) (PMMA) particles sterically stabilized by polyisobutylene (PIB) was studied by transient fluorescene method in iso–octane, hexadecane, and in powder from. When samples of dispersions are annealed above 60°C, their room temperature lifetimes increase, and when powder samples are so annealed, lifetimes decrease. Self‐quenching effects among N*/N pairs were eliminated to isolate unimolecular lifetimes. Low‐frequency intramolecular vibrations are found responsible for the temperature dependence of nonradiative transition of excited N molecules. Corresponding activation energies are measured and found to be between 2300 and 1100 cal/mol. Solvent effects on these activation energies are discussed. © 1995 John Wiley & Sons, Inc.
Surface behavior of dilute blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers
Authors: Gorelova M. M. , Pertsin A. J. , Volkov I. O. , Filimonova L. V. , Makarova L. I. , Zhdanov A. A. 
Published: April 2003

AbstractX‐ray photoelectron spectroscopy is used to study the surface segregation of siloxane in blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers. At high concentration of the oligomeric additive, the surface segregation of siloxane in the blends strongly depends on the molecular architecture of the additive: the segregation is much higher when the siloxane blocks are at the ends of the oligomeric chains. At low additive concentrations, the surface segregation of siloxane is governed solely by the siloxane concentration in the bulk. © 1995 John Wiley & Sons, Inc.
Graft‐interpenetrating polymer networks of polyurethane and bismaleimide
Authors: Hsieh K. H. , Hung W. Y. , Liao D. C. , Kao S. C. 
Published: April 2003

AbstractGraft‐interpenetrating polymer networks (graft‐IPNs) of polyurethane (PU) and bismaleimide (BMI) were prepared by using a simultaneous polymerization technique. The effects of the PU molecular weight and the amounts of the PU on the mechanical properties, density, and morphology of the IPNs are discussed. The graft‐IPNs exhibited superior ultimate tensile strength and large improvement in flexural strength when the short soft segments of the PU were introduced. Better thermal stability of the IPNs was shown by increasing the BMI content. The heterogeneous and phase‐separated characteristics were found from the results of dynamic mechanical analysis. The maximum density was achieved by the graft‐IPNs structure when 33.3 wt % of PU with short soft chain length was added. The graft‐IPNs also showed heterogenous morphology in the micrographs when a large amount of PU was incorporated. © 1995 John Wiley & Sons, Inc.
Hydrolysis of poly(acrylamide)–starch graft copolymer
Authors: Khalil M. I. , Farag S. , Fattach S. Abd El 
Published: April 2003

AbstractPoly(acrylamide)–starch graft copolymer was treated independently with sodium hydroxide and different acid solutions. The different acids include phosphoric, hydrochloric, and sulphuric acid. The treatment was carried out under a variety of conditions including sodium hydroxide concentration, time, and duration of hydrolysis as well as type of acid used. The extent of hydrolysis was assessed by estimating amide and carboxyl content as well as the acrylate and starch content before and after treatment. It was found that the increment in carboxyl content is equal to the decrement in amide on using sodium hydroxide concentration up to 1N, while using higher concentration than 1N leads to a difference in formed carboxyl and decreased amide groups. The magnitude of this difference depends on sodium hydroxide concentration as well as temperature and duration of hydrolysis. The maximum value of carboxyl content obtained was 593 meq/100 g sample. The acidic treatment of the starch copolymer does not affect the conversion of amide groups to carboxyl groups, and the sole effect was hydrolysis of starch component of the copolymer. Evaluation of the alkali‐treated copolymer as cation exchanger was carried out. The absorption efficiency % of different cations depends on the associated anions and follow the order: Cu2+ > Zn2+ > Co2+ > Mg2+. © 1995 John Wiley & Sons, Inc.
UV and fluorescence characterization of styrene and methyl methacrylate polymerization
Authors: Kim You Shin , Sung Chong Sook Paik 
Published: April 2003

AbstractPolymerization of styrene and methyl methacrylate (MMA) were studied by UV and fluorescence spectroscopic techniques. Using a sharp decrease in the extinction coefficient at 250 nm and the fluorscence quantum yield at 308 nm of styrene following polymerization, styrene conversion in solution polymerization by UV and fluorescence measurements were found to correlate well with IR results monitoring the disappearance of vinyl groups, at three different temperatures (65, 70, and 75°C). The activation energy of about 6 kcal/mol was obtained. Using the decrease in UV absorbance of MMA during polymerization, solution polymerization of MMA was studied and compared with IR results. Due to the solvent absorbance, the UV method underestimates the conversion to a certain extent. When a small amount of styrene is added in MMA polymerization as a reactive extrinsic comonomer, the conversion of styrene measured by fluorescence is found to be faster than MMA, due to the characteristic reactivity ratios of MMA and styrene. The correlation curve could be used to estimate MMA conversion from styrene fluorescence, providing a method more sensitive than the viscosity‐dependent fluorescence probe technique. Bulk polymerization of styrene was studied by bifurcated fiber‐optic fluorescence. Due to self‐quenching, little fluorescence of styrene is observed up to 75% conversion, but increases sharply from 75 to 85% conversion, followed by a drastic decrease during the last 15% conversion. In comparison to other methods of following vinyl polymerization such as refractive index, density, and gel permeation chromatography, these spectroscopic techniques provide real‐time in situ capability as well as better sensitivity, especially in the later stages of polymerization. © 1995 John Wiley & Sons, Inc.
Curing reaction of diglycidylesters containing alicyclic imide structures with anhydrides and amines as hardeners
Authors: Galià M. , Serra A. , Mantecón A. , Cádiz V. 
Published: April 2003

AbstractThe cure reaction of diglycidyl esters containing bicyclo[2.2.2]oct‐7‐ene units with phthalic annhydride, hexahydrophthalic anhydride, bis(4‐aminophenyl)methane, and bis(4‐aminophenyl)ethane as hardeners was studied by differential scanning calorimetry. The use of 4‐dimethylaminopyridine as a catalyst agent for the anhydride–epoxide reaction was also investigated. Depending on the curing agent, anhydride or amine, and the concentration of the catalyst, differences in activation energies were found, but negligible changes are observed between both anhydrides and the two primary amines. Thermal properties of the final product were unaltered by the hardener used. © 1995 John Wiley & Sons, Inc.