bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractionation of a statistical copolymer in a demixing‐solvent system: Theory and experiment
Authors: Podešva Jiří , Stejskal Jaroslav , Prochǎzka Ondřej , Špaček Pavel , Enders Sabine 
Published: April 2003

AbstractIt has been shown that, under specific conditions, a demixing‐solvent fractionation according to chemical composition can be applied to statistical copolymers. Formally, identical expressions have been derived for the distribution of a copolymer between coexisting phases in precipitation (sol‐gel) and demixing‐solvent fractionations. Theory predicts that the effects of molar mass and chemical composition cannot be separated in either of the phaseequilibrium fractionations. With demixing solvents, the partition coefficient depends steeply on copolymer composition, which enables one, e.g., to separate homopolymers from a blend. Multistep demixing‐solvent fractionation of a copolymer may proceed only in specific cases, e.g., immediately below the maximum of the coexistence curve. A feasibility study was performed with a chemically heterogeneous statistical copolymer of styrene and 2‐methoxyethyl methacrylate; the experimental results have confirmed the theoretical predictions. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of metal‐containing coordination polymers of poly(methylene diphenylene terephthalamide)
Authors: Bajpai U. D. N. , Rai Sandeep , Bajpai Anjali 
Published: April 2003

AbstractAmino group‐terminated poly(methylene diphenylene terephthalamide) (PMDTA) was prepared using a phosphorylation technique that was then converted into Schiff's base coordination polymers by their reaction with Co(II), Ni(II), and Cu(II) complexes of salicylaldehyde [M(SAL)2] and 2‐hydroxy‐1‐naphthaldehyde [M (NAPTHAL)2]. The resulting coordination polymers were characterized by IR, elemental analysis, magnetic susceptibility measurements, and thermogravimetric analysis (TGA). TGA shows that coordination polymers are more thermally stable than is the ligand under similar conditions. On the basis of observed results, an oxygen‐and nitrogen‐coordinated structure for polyar‐amid‐metal complexes has been proposed. © 1993 John Wiley & Sons, Inc.
The influence of the equilibrium melting temperature on the supermolecular morphology of several polymers
Authors: Murphy C. J. , Fay J. J. , Vail E. A. M. , Sperling L. H. 
Published: April 2003

AbstractAt a constant isothermal crystallization temperature (Tc), the crystalline morphologies of several polymers have been found to be a function of the melt‐liquid temperature (T1). At a constant Tc below a critical crystallization temperature (T [about 0.9 T(K)], a transition from a nonspherulitic to a spherulitic morphology occurs when the melt liquid is heated above a melt‐liquid transition temperature, (Tlt) [approximately 1.03 Tm (K)], where Tm is the observed melting temperature of the sample. The melt‐liquid transition temperature, Tlt, which experimentally affects the visible morphology of a semicrystalline polymer, is apparently indistinguishable from the thermodynamic melting temperature, T, determined by the Hoffman‐Weeks procedure. The X‐ray powder diffraction patterns of spherulitic and nonspherulitic morphologies were identical, independent of the heating‐cooling cycle. This suggests that the transition that occurs at TIt does not affect the arrangement of polymer molecules in the crystallite, but only the manner in which the crystallites are arranged in the supermolecular morphology. The evidence suggests, at least for the polymers studied, that a residual order exists in the melt until the T or TIt of the particular polymer is reached. © 1993 John Wiley & Sons, Inc.
The effect of plasticization and pH on film formation of acrylic latexes
Authors: Eckersley S. T. , Rudin A. 
Published: April 2003

AbstractThe effect of several variables relevant to film formation in 49 : 49 : 2 poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) latexes were studied.Plasticization of the terpolymer by both an anionic [sodium dodecyl benzene sulphonate (NaDBS)] and a nonionic [nonyl phenol ethylene oxide adduct (NP40), forty ethylene oxide units on average] surfactant were investigated. Dynamic mechanical measurements indicated that NP40 plasticized the polymer, whereas NaDBS did not. This was attributed to the compatibility of the nonionic emulsifier and the polymer. The influence of the surfactants on the film formation process was studied using minimum film temperature (MFT) measurements and scanning electron microscopy (SEM). As expected, the MFT was independent of NaDBS concentration. However, the MFT was also independent of NP40 concentration. Film formation was further investigated using SEM. The series of micrographs at varying NaDBS concentrations showed no effect on the degree of film fusion. However, surface exudates were observed. The micrographs revealed that increasing NP40 content resulted in an apparently greater degree of film coalescence. That is, there was bridging of the particles in the interstitial regions. This was attributed to localized plasticization of the polymer in these regions by NP40.The effect of water plasticization of the latex polymer was studied using dynamic mechanical measurements. The physical character of the terpolymer was varied using mol wt modifiers (CBr4 chain transfer agent and ethylene glycol dimethacrylate crosslinker). It was found that all of the polymers were plasticized by water.Finally, the film forming behavior was investigated as a function of latex pH. MFT measurements indicated an independence of pH. © 1993 John Wiley & Sons, Inc.
Deformation behavior of poly(dimethyl siloxane) networks. I. Applicability of various theories to modulus prediction
Authors: Venkatraman S. 
Published: April 2003

AbstractThe shear moduli of end‐linked poly(dimethyl siloxane) networks were measured as a function of mol wt between chemical crosslinks (Mc) and the dilution‐at‐cure (Cx). The results were interpreted in terms of theories that take into account contributions from trapped entanglements. It was found that the network deformation follows the predictions of the theory of “phantom” networks, with an added contribution from trapped entanglements. At high mol wts of the precursor polymer, network imperfections play a role, as seen in the frequency dependence of the shear modulus. This results in deviation from predicted behavior. © 1993 John Wiley & Sons, Inc.
Determination of the elastic component for polymeric melt under steady shear flow
Authors: Pham H. T. , Bosnyak C. P. , Wilchester J. W. , Christenson C. P. 
Published: April 2003

AbstractSteady state shear flow in rectilinear coordinates can be generated by a direct shear rheometer. The rheological behavior of polymeric melts under shear flow can be characterized by the inception of steady shear flow and stress relaxation after cessation of steady shear flow. Experiments were performed for bisphenol A polycarbonate with various mol wts. The elastic components, such as the primary normal stress differences and the elastic recoverable shear strain of the polymeric melts, can be determined from the shear moduli. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of membranes with positively charged main chain from polyethylenimine
Authors: Nagaya Jiro , Tanioka Akihiko , Miyasaka Keizo 
Published: April 2003

AbstractA membrane, which has positively charged groups in the polymer main chain, was prepared from polyethylenimine by crosslinking and successive alkylation. Dibromoalkane was used as a crosslinking agent. The crosslinked membrane was alkylated using methyl iodide under several conditions. Elemental and ICP emission analyses were introduced to measure the rates of alkylation and quaternization. From the membrane potential measurement, the effective charge density was estimated. The highest value was about 1.0 M, which was obtained by a prolonged alkylation time. This value was larger than that of some commercial ion exchange membranes. The effective charge density, which was obtained by the last alkylation procedure, was 10 times larger than that of the former one, though the rate of quaternizing increased by less than a factor of two. This implies that the activity constant in the membrane increased when the charge density is increased. © 1993 John Wiley & Sons, Inc.
Enhancement of the metal‐binding properties of chitosan through synthetic addition of sulfur‐ and nitrogen‐containing compounds
Authors: Lasko C. L. , Pesic B. M. , Oliver D. J. 
Published: April 2003

AbstractSeveral new chitosan derivatives were synthesized with the intent of forming polymers that could be used in hazardous waste remediation as toxic metal‐binding agents in aqueous environments. The ability of these derivatives to bind Cu2+, Pb2+, Cd2+, and Fe2+ was tested and compared to chitosan. Four of the new compounds, the products of the reaction of chitosan with mercaptosuccinic acid, thiirane, pyridoxal hydrochloride, and succinamide, show promising results as binding agents for the above metal ions. The compound with mercaptosuccinic acid bound twice as much Cd2+, five times as much Pb2+, and virtually no Fe2+ when compared to chitosan. The compound with thiirane bound three times as much Pb2+, whereas the pyridoxal hydrochloride derivative bound 30% more Cu2+ and twice the Pb2+. The succinamide derivative gave results comparable to chitosan, but with decreased solubility at low pH. © 1993 John Wiley & Sons, Inc.
Characterization of grafted polyethylene by contact‐angle hysteresis and ESCA studies
Authors: Konar J. , Sen A. K. , Bhowmick A. K. 
Published: April 2003

AbstractLow‐density polyethylene (LDPE) has been functionalized in the bulk through dicumyl peroxide (DCP)‐initiated grafting of dibutyl maleate (DBM) and vinyltrimethoxysilane (VTMO) in the temperature range from 140 to 200°C. The functionalized surfaces have been characterized through contact angle and contact‐angle hysteresis measurements as well as through ESCA studies. The degree of grafting has been determined by infrared spectrophotometry. From the ESCA patterns of the modified polymers, the atomic ratios of oxygen to carbon and silicon to carbon have been calculated. Determination of an empirical relation between contact‐angle hysteresis and the oxygen‐carbon ratio of the functionalized polymer surfaces has been attempted. It is found that the higher the oxygen‐carbon ratio, the lower the contact‐angle value for polyethylene. Contact angle‐hysteresis increases with increase of the degree of grafting. The total surface energy increases with grafting. The surface energy of the silane‐grafted polyethylene (PEgS) is found to be the lower than that of dibutyl maleate‐grafted polyethylene (PEgDBM). © 1993 John Wiley & Sons, Inc.
Morphology‐property relationships in oriented PET films: A role of in‐plane crystalline orientation distribution on the film properties
Authors: Gohil Ramesh M. 
Published: April 2003

AbstractThe role of in‐plane crystalline, amorphous, and overall molecular orientation on various properties in the plane of the films was investigated using a variety of techniques. It is shown that for a fixed value of crystallinity the in‐plane crystalline orientation and the nature of the constraint imposed by the crystallites on the molecules play an important role in obtaining isotropic in‐plane expansion or shrinkage properties. Achievement of in‐plane isotropic tensile strength and elongation at the break are found to depend entirely upon an isotropic distribution of the amorphous orientation; the orientation of crystallites plays no detectable role. Furthermore, the deformation mechanisms of sequential and simultaneous biaxial stretching processes have been investigated and compared. The simulteneous stretching process is considered to be a more controlled film‐fabricating method compared to sequential stretching in achieving balanced, in‐plane film properties. © 1993 John Wiley & Sons, Inc.
High speed tensile performance and fractography of acrylic latex films
Authors: Eckersley Sarah T. , Plumtree Alan , Rudin Alfred 
Published: April 2003

AbstractThe performance of acrylic (50:50 MMA/BuA) latexes was investigated as a function of fusion level using high speed tensile testing. The structure of the copolymer was varied via the addition of molecular weight modifiers to the emulsion polymerizations. Chain transfer agent (CBr4) was used to reduce the copolymer modulus, and crosslinker (EGDM, ethylene glycol dimethacrylate) was added to increase the modulus. The resulting materials exhibited a wide range of viscoelastic behavior (G* varied from ∼ 107 dyne cm−2 to ∼ 109 dyne cm−2). Fracture energy and peak force at break were measured as a function of the complex modulus. It was found that both of these parameters showed a maximum with respect to G* that corresponded to intermediate levels of crosslinking. This observation was explained in terms of the degree of coalescence of the films. Fully fused films (excess CBr4) were brittle and performed poorly, conceivably because of insufficient entanglement to support stress. Marginally fused films also exhibited inferior, brittle behavior. The films cast from latexes synthesized with low levels of molecular weight modifiers showed intermediate fusion levels and superior tensile performance. The quantitative results were rationalized using scanning electron microscopy (SEM) of both the virgin films and the fracture surfaces. For comparison, the same materials were tested in a fully fused state following hot pressing. The behavior paralleled that expected for vulcanized rubbers in which lightly crosslinked materials exhibit the highest tensile strength. © 1993 John Wiley & Sons, Inc.
Studies of polymer mobility in composite blends of poly(vinyl butyral) and alumina
Authors: Parker A. A. , Opalka S. M. , Dando N. R. , Weaver D. G. , Price P. L. 
Published: April 2003

AbstractSolid‐state NMR and thermal analysis techniques were used to compare the mobility of poly(vinyl butyral) (PVB) in the presence and absence of both alumina filler particles and plasticizer. The relative mobility of main‐chain and side‐chain carbons increases in the presence of both plasticizer and alumina as seen from an increase in the average cross‐polarization rates, 〈TCH〉, and from a general decrease in the rotating frame spin‐lattice relaxation rates, CT1ρ. Unlike the main‐chain carbons, inversion recovery cross‐polarization (IRCP) data on solution cast composites show that the side‐chain methyl groups in neat PVB samples are best characterized by a monoexponential cross‐polarization model. However, in the presence of alumina, a fraction of the methyl groups becomes less mobile as indicated by the biexponential IRCP behavior. Polymer phase mobility also increases below the critical pigment volume concentration (CPVC) as seen from decreasing transition temperatures using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). This is accompanied by an increase in the rigidity of a portion of the polymer phase above the CPVC as indicated by an increase in the apparent Tg, along with an increase in the mobility of another portion as indicated by the appearance of a low‐temperature DMA transition. These trends are consistent with an increase in polymer chain packing heterogeneity in the presence of alumina. © 1993 John Wiley & Sons, Inc.
Photografting of acrylonitrile and methacrylic acid on polyethylene film under air atmosphere
Authors: Kubota Hitoshi 
Published: April 2003

AbstractPhotografting of acrylonitrile (AN) and methacrylic acid (MAA) on low‐density polyethylene film (thickness 70 μm), on which benzophenone was coated earlier, was investigated at 60°C in water medium under air atmosphere. In the case of AN monomer, where grafted polymer was formed predominantly, oxygen in the system promoted the formation of both grafted polymer and homopolymer. With MAA monomer, in which homopolymer was formed preferentially compared to the formation of grafted polymer, the formation of homopolymer was accelerated by the presence of oxygen while suppressing that of grafted polymer. The formation of polyethylene peroxides by photoirradiation seemed to be a factor for the accelerated polymerization under air atmosphere. It was found that additives such as hydrazine and metallic ions (Fe2+, Cu2+, and Ni2+) are useful for enhancing the photografting under air atmosphere. © 1993 John Wiley & Sons, Inc.
Effect of water on the glass transition temperature of hydrophilic polyurethanes
Authors: Schneider Nathaniel S. , Illinger Joyce L. , Karasz Frank E. 
Published: April 2003

AbstractThe depression of the glass transition temperature by water was studied in a set of polyurethanes in which the soft segment consisted of polyethylene oxide (sample I) or a block copolymer of poly(propylene oxide) terminated with poly(ethylene oxide) in various proportions (sample set II). DSC measurements were made at two added water contents for each type of sample and at various temperatures. The Tg reduction appeared to be governed solely by the nonfreezing bound water and was much larger in sample I than in samples of set II. The more limited effect on the Tg of set II samples is attributed to restricted mobility arising from coupling of the short terminal poly(ethylene oxide) to rigid hard‐segment units. Therefore, the data for sample I are preferred as a test of the predictive relations for the Tg depression. On this basis, it appears that the simple Fox mixing equation is more reliable than is the available free volume approach, which required unrealistically high values of the thermal expansion coefficient for water to fit the data for sample I. © 1993 John Wiley & Sons, Inc.
Procedure for zone winding of extended‐length netted composite shells
Authors: Pichugin V. S. , Kestelman V. N. 
Published: April 2003

AbstractThe subject of this paper is the extended‐length netted wound composite shells operating in cantilever loading conditions. The winding method that enables the attainment of various thicknesses of the netted shell zonewise is discussed. The distinguishing feature of this formation is the introduction of the sectional expansion mandrel into the production process. The efficiency of the elaborated method is based on the known dependence of the composites' mechanical properties on the tension of the reinforcing filler. On completion of winding, the blank is heated and, with the mandrel sections moved apart in the axial direction, the required level of fiber tension is created in each zone. The improved quality of the material enables increasing of the load‐carrying capacity of the items at the simultaneous reduction of their mass. Use of the procedure is most expedient for the manufacture of items from high‐modulus reinforcing materials. The field of application is the production of vital shell structures, such as helicopter tail booms, masts of vessels, and power transmission line supports. © 1993 John Wiley & Sons, Inc.
Enhanced laminate damping via modification of viscoelastic interlayer
Authors: Liao Fu‐Sen , Hsu Tzu‐Chien J. , Su A. C. 
Published: April 2003

AbstractThis study sought to develop a sandwich‐type vibration damping laminate suitable for room‐temperature applications. The laminate consisted of a polymeric interlayer that was sandwiched between two steel sheets. The study was initiated to promote the relatively low‐damping capability of a maleic anhydride‐grafted polypropylene (mPP)‐based laminate, which failed to meet the requirement that the loss factor of the laminate should be greater than 0.05 for effective damping. Modifications of mPP by incorporation of a dynamically vulcanized PP/butyl rubber blend were then followed. The modifications were based on the theoretical analysis proposed by Rose, Ungar, and Kerwin (RUK) for a general polymer‐based laminate. The design criteria for the polymeric interlayer, i.e., the preferred range of storage modulus G′ for a set of reasonable values of loss tangent (tan δ), were first established from calculations by use of the RUK theory. The theoretical calculations revealed that the low damping of the mPP‐based laminate resulted primarily from the high G′ and low tan δ of the interlayer. Incorporation of butyl rubber into the polymeric interlayer led to a strong decrease in G′ and a moderate increase in tan δ. These modifications resulted in significantly improved damping capability of the laminate, as predicted by the RUK theory. © 1993 John Wiley & Sons, Inc.
Modeling and simulation of semibatch emulsion polymerization
Authors: Li Bogeng , Brooks Brian W. 
Published: April 2003

AbstractBy taking advantage of recent theoretical developments in emulsion polymerization and radical polymerization kinetics at high conversion, a model is developed for simulating seeded semibatch emulsion polymerization. The model is used to calculate the time evolution of the polymerization rate, the monomer conversion, the instantaneous degree of polymerization, the monomer concentration in particles, the average radical number per particle, and the propagation rate coefficient and termination rate coefficient over the whole course of the polymerization. Experimental observations by previous workers, including the existence of steady‐state phenomenon and the broad distributions of molecular weight, are reproduced in the results of the simulation. The gel effect on emulsion polymerization and the open‐loop stability of the semibatch process are discussed. © 1993 John Wiley & Sons, Inc.
Graft polymerization of fluorinated monomer onto corona‐treated PVA and cellulose films
Authors: Hoebergen A. , Uyama Y. , Okada T. , Ikada Y. 
Published: April 2003

AbstractSurface graft polymerization of a hydrophobic monomer, 2,2,3,3,3‐pentafluoropropyl methacrylate (5FMA), onto hydrophilic poly(vinyl alcohol) (PVA) and cellulose films was studied after corona discharge of the films. It was found that grafting strongly depended on the reaction medium; especially, addition of alcohol to the monomer greatly accelerated graft polymerization. For instance, when an ethanol/ water /5FMA mixture (65/25/10, by volume) was used as the polymerization medium. the PVA and cellulose films corona‐discharged for a few minutes exhibited a high contact angle up to 100° after 30 min polymerization, the graft density being approximately 170 μg/cm2 for cellulose and 80 μg/cm2 for PVA. © 1993 John Wiley & Sons, Inc.
Toughening of epoxy resins by N‐phenylmaleimide‐N‐cyclohexylmaleimide–styrene terpolymers
Authors: Iijima Takao , Sato Ken , Fukuda Wakichi , Tomoi Masao 
Published: April 2003

AbstractN‐Phenylmaleimide (PMI)‐N‐cyclohexylmaleimide (CMI)‐styrene (St) terpolymers were used to improve the touchness of bisphenol‐A diglycidyl ether epoxy resin cured with p,p′‐diaminodiphenyl sulfone (DDS). The terpolymers were effective as modifiers for toughening of the epoxy resin system. The most suitable compositions for the modification of the epoxy resin were inclusion of 10 wt% of the terpolymer (45 mol % PMI, 5 mol % CMI, and 50 mol % St units) with Mw higher than 247,000, which led to ca. a 140% increase in the fracture toughness (KIC) of the cured resin with a medium expense of mechanical properties. The glass transition temperatures of the modified resins were equal to or higher than that of the parent epoxy resin. The morphologies of the modified resins were dependent on the terpolymer molecular weight and concentration. On addition of 5 wt % of the terpolymer (Mw 400,000), the modified resins had two‐phase morphologies and the terpolymer‐rich dispersed particles in the epoxy matrix. On addition of more than 8 wt % of the terpolymer, the morphologies of the cured resins changed drastically and showed a tendency to from cocontinuous phases. The toughening mechanism was discussed in terms of the morpho‐logical behaviors of the modified epoxy resin systems. © 1993 John Wiley & Sons, Inc.