bluuebunny/crossref_metadata_2025 huggingface dataset:
Water‐soluble sulfonated amino–formaldehyde resins. IV. Melamine–urea resins: Synthesis and properties
Authors: Hovakeemian George , Absi‐Halabi Ma'Mun , Lahalih Shawqui M.
Published: April 2003

The factors affecting the preparation and the properties of sulfonated melamine urea–for‐maldehyde resins were studied. The resins weresynthesized using a four‐step procedure previously used in preparing sulfonated melamine formaldehyde resins. The melamine–urea resins required higher hydroxymethylation and condensation temperatures as the percentage of urea increased. The molecular weight distribution of the prepared resins revealed the formation of low molecular weight species in increasing amounts with higher percentages of urea. The effectiveness of the prepared resins as dispersants for concrete mixes was found to be lower than the pure melamine resins; however, it was possible to enhance them by raising the ratio of sulfonated groups in the resins.
Modification of natural rubber tubes for biomaterials. II. Radiation‐induced grafting of N,N‐dimethylaminoethylacrylate (DMAEA) onto natural rubber (NR) tubes
Authors: Razzak Mirzan T. , Otsuhata Kazushige , Tabata Yoneho , Ohashi F. , Takeuchi A.
Published: April 2003

Radiation‐induced simultaneous grafting of N,N‐dimethylaminoethylacrylate (DMAEA) onto NR tubes has been studied to improve blood compatibility of NR tubes. In the grafting of DMAEA onto NR tubes, effect of grafting parameters such as solvent, monomer concentration, temperature, dose, and dose rate on the grafting yield was investigated. As the results, it was found that the grafting proceeds effectively in the presence of carbontetrachloride (CCI4) as a solvent. The initial rate of grafting was found to be proportional to 0.70 power of dose rate and to 0.95 power of monomer concentration. The activation energy for this grafting system was calculated to be 6.78 kcal/mol. The evaluation of blood compatibility of NR‐g‐DMAEA was carried out by ex vivo test. Blood compatibility of those samples was found to be dependent on only grafting yield. When the degree of grafting is higher than 30 wt %, blood compatibility of NR tube could be improved by DMAEA grafting. This is the same tendency which that of previous grafting system of NR‐g‐DMAA.
Irreversible step growth polymerization having segmental diffusion limitations in HCSTRs—simulation and steady state multiplicity
Authors: Jana Sadhan C. , Gupta Santosh K.
Published: April 2003

The effect of various parameters on the overall rate constant, number average chain length, and polydispersity index of isothermal, irreversible, step growth polymerization of ARB monomers, exhibiting segmental diffusional limitations and carried out in HCSTRs, are studied. A phenomenological model which has proved useful for chain polymerization is adapted for step growth polymerizations and simulations for several values of the different parameters are carried out. The number average chain length μn and the polydispersity index ρ are obtained as a function of the dimensionless time t*. It is found that, even though the behavior of μn and ρ vs. t* depends on the values of the parameters, the plot of μn vs. ρ is unique as expected from statistical considerations. An attempt has been made to investigate the multiplicity of steady states under conditions of infinitely rapid heat transfer from a jacket, using singularity and bifurcation theory. It is found from the analysis that there is no multiplicity of steady states for this system, which is confirmed by simulations using a wide range of parameter values.
A new coupling agent for aramid fibers
Authors: Andreopoulos A. G.
Published: April 2003

Various compounds were used for the surface treatment of aramid fibers in order to promote adhesion to polymeric matrices. The improvement of adhesive bond could be based either on the roughness of fiber surface or on chemical modification introduced by grafting. The compounds used are more or less reactive to the secondary amide groups, present on the aramid chain. Thus, the fibers were impregnated with acetic acid anhydride, sulfuric acid–acrylamide, and methacryloyl chloride. The effect of such treatment was first evaluated by optical microscopy and infrared analysis. Tensile measurements were also carried out in order to define any changes of strength and modulus. Finally, tensile specimens were prepared using unsaturated polyester reinforced with aramid fibers and the effect of chemical treatment on the tensile strength was determined. From the above study, methacryloyl chloride was proved an effective coupling agent with possible grafting to aramid fibers.
Dynamic compression characteristics of flexible foams. II. Density variation
Authors: Yossifon S. , Szanto M.
Published: April 2003

In Part I, a simple mathematical model was proposed, based on dimensional similarity parameters, to describe the characteristics of flexible plastic foams under impact conditions. The model assumes that the foam is a rate‐dependent material. In the present part we extended the similarity model, by including the density of the foam parameter (for the same material and technological process). The density parameter is significant for systems cushioning with regard to weight and cost constraints. The behavior of flexible foams was studied with density as the variable parameter in a range of 100–240 kg/m3, with constant geometrical dimensions, for a wide range of drop heights and masses. We used the similarity parameters approach to predict the characteristics of the foams for various foam densities. The results show that for particular tested cases, the maximum deformation, the maximum deceleration, and the time pulse‐period decrease as the foam density increases.
Studies on the polyblends of poly(vinyl chloride) with various methacrylate copolymers, physical and mechanical properties. I
Authors: Saroop U. K. , Sharma K. K. , Jain K. K. , Misra Ashok , Maiti S. N.
Published: April 2003

The effect of blending various methacrylate copolymers on the physical and mechanical properties of poly(vinyl chloride) (PVC) has been investigated. Copolymers of methylmethacrylate with methylacrylate, ethyl acrylate, butyl acrylate, and 2‐ethylhexyl acrylate in 80:20 and 50:50 wit methylmethacrylate have been prepared and characterized by nuclear magnetic resonance spectroscopy. Polyblends of PVC and such polyacrylates have been prepared in 80:20 ratio by melt blending technique and characterized by thermomechanical analysis to study the glass transition behavior vis‐à‐vis the compatibility of these blends. Mechanical properties of these blends revealed a substantial increase in impact strength particularly when long chain acrylate polymers like butyl acrylate and 2‐ethyl hexyl acrylates are used; however, there is a decrease in the yield stress and initial modulus. A shift from brittle failure to ductility has been observed in blends of PVC on incorporation of these acrylate copolymers. Scanning electron microscopic studies have been carried out to support these observations.
A study of thermal degradation kinetics and mechanism of vinyl acetate and itaconic acid copolymers
Authors: Kotzeva L. , Mateva R. , Nikolova N. , Kovacheva P.
Published: April 2003

Vinyl acetate and itaconic acid copolymers, obtained by radical copolymerization using single and continuous methods of itaconic acid addition, the amount of the acid being up to 8.5 mol %, were characterized by DTA, TG, DTG, and DSC. Using IR spectroscopy for both types of copolymers, it was proved that cyclodehydration takes place in the temperature range 130–230°C. In the range 230–350°C, processes of decarboxylation of cycloanhydrous and carboxylic groups and splitting of acctic acid proceed at the same time, followed by destruction of the polyene structures formed. The rate of thermal degradation depends both on the amount and distribution of itaconic units in the macrochain. The kinetic parameters of the process were calculated.
Diffusion of saturated hydrocarbons in low density polyethylene (LDPE) films
Authors: Asfour Abdul‐Fattah A. , Saleem M. , Kee D. De , Harrison B. H.
Published: April 2003

The diffusion coefficients at zero penetrant concentration, D0, of n‐heptane, n‐heptane, n‐octane, n‐decane, and 2,2,4‐trimethylpentane (TMP) in LDPE were obtained in the range of 25–50°C, using the desorption method. The dependence of D0 on the size and shape of the penetrant is reported. It was found that D0 decreases with increasing penetrant molecule size. The activation energies of diffusion in the temperature range of 25–50°C increase with increasing penetrant molecule size and are independent of temperature. The results are interpreted in terms of the free volume theory and semiquantitative estimates of the free volume parameters are reported.
Ionene elastomers from polytetramethylene oxide diamines and reactive dihalides. I. Effect of dihalide structure on polymerization and thermal reversibility
Authors: Leir Charles M. , Stark John E.
Published: April 2003

The reaction of α,ω‐bis(dimethylamino) polytetramethylene oxide with various dihalides provided a series of elastomeric ionenes. The influence of dihalide structure on the reaction was studied and a number of substituents were found which dramatically increased the rate of polymerization and ultimate molecular weights achieved. These ionene elastomers were thermoplastic and it was shown that in some cases this result was due at least in part to a depolymerization reaction via a dequaternization of the ammonium links. Again, structural features in the dihalide were important not only for the reverse reaction, but for the repolymerization to high molecular weight elastomer as well. An uncharged “analogue” was also prepared to address the feature of microphase separation and compared with the above ionene materials.
Structure‐property behavior of elastomeric segmented PTMO–ionene polymers. II
Authors: Feng D. , Venkateshwaran L. N. , Wilkes G. L. , Leir Charles M. , Stark John E.
Published: April 2003

A series of segmented ionene polymers based on the reaction of α,ω‐bis(dimethyl amino)polytetramethylene oxide with various dihalide compounds were investigated with respect to their structure–property behavior. The placement of quaternary ammonium ions and halide counterions along the polymer chains was varied by changing the molecular weight of the PTMO soft segment and the structure of the dihalide linking agent. The techniques of dynamic mechanical spectroscopy, thermal analysis, small angle X‐ray scattering, and stress–strain behavior analysis were applied. For the case when the PTMO soft segment was amorphous, the ambient temperature properties of these materials displayed low modulus, high strength, and high elongation elastomeric behavior with tensile strength enhanced by the strain‐induced crystallization of the PTMO. A high level of phase separation existed between the dihalide component relative to the PTMO soft segment. Due to the Coulombic association of the ionene species, these materials displayed many similarities to the segmented urethane ionomers. In particular, distinct domain structure was noted by SAXS, whose dimensional scale was similar to the segmented urethanes. It was also shown, however, that the driving forces for the microphase separation was caused by favorable electrostatic or Coulombic interactions in contrast to segment–segment incompatibility features as in the segmented urethanes.
Microstructural and bulk characterization of two poly(siloxane‐imide) multiblock copolymers
Authors: Spontak Richard J. , Williams Michael C.
Published: April 2003

Much of the unique thermomechanical behavior of microphase‐separated block copolymers is well established for the diblock and triblock architectures, and most of the data base involves polymers with polystyrene and polydiene blocks. However, there have been few reports about phase‐separated multiblocks composed of polysiloxane blocks and polyimide blocks. Here, using various facets of electron microscopy, we have characterized the domain sizes and elemental composition of these copolymers. In situ responses to both thermal annealing and tensile strain have been examined as well. To suggest possible structure‐property relationships, differential scanning calorimetry and rheological tests have also been conducted. Measurements are reported for glass‐transition and decomposition temperatures, linear viscoelastic properties (storage and loss moduli), and nonlinear stress‐strain tensile properties.
A new method to measure temperatures in polymer melts using heusler alloys
Authors: Sobczak R. , Hermann W.
Published: April 2003

With the help of ferromagnetic Heusler alloys, which are mixed in powdery form into a cylindrical polymer sample surrounded by an induction coil, temperature can be measured. Some 10 K below the Curie temperature small temperature changes already yield considerable signals in the induction coil via the temperature dependence of the permeability of the alloy. From the tremendous variety of Heusler alloys avaialable for each temperature region of interest the proper material can be chosen. The amount of sample needed is small enough to leave the rheological properties of the melt unchanged. Measurements do not involve touching the sample and follow each temperature change more or less simultaneously since the grains of the alloys are very small and have very small heat capacities only.
Monitoring the UV degradation of PVC window frames by microhardness analysis
Authors: González A. , Pastor J. M. , De Saja J. A.
Published: April 2003

While well‐known methods of bulk analysis of thermal degradation of PVC become standard industrial tools, techniques for the study of surface damage produced by weathering are not generally considered. In this paper we present a new test, based on microhardness measurements, which can be used as a complementary technique for the study of this phenomenon. Comparison of this method with color changes and specific elongation at break measurement has been established for PVC window frames.
New aspects in cationization of lignocellulose materials. X. Thermooxidation of TMAHP–sawdust
Authors: Šimkovic Ivan , Antal Miroslav , Csomorová Katarina , Micko M. M.
Published: April 2003

With the help of dynamic and isothermic thermogravimetry in inert and oxidative atmosphere the thermooxidation of TMAHP–sawdust in individual anionic forms was studied. The values obtained indicate that the most resistant samples against thermooxidation are H2PO−4 and Br− anionic forms. The most easily thermooxidized sample is the OH− form. The thermooxidation seems to be a less energy‐consuming reaction than thermolysis.
Monomer addition policies for copolymer composition control in semicontinuous emulsion copolymerization
Authors: Arzamendi Gurutze , Asua Jose M.
Published: April 2003

The effect of various monomer addition policies on the composition of a copolymer synthesized by semicontinuous emulsion copolymerization, using monomes with widely different ractivity ratios, was studied by mathematical simulation. Three policies were considered. In the first, both monomers are added under starved conditions. In the second, the reactor is initially chanrged with all of the less reactive monomer plus the amount of the mono reactive monomer needed to initially form a copolymer with the desired composition. Subsequent addition of the remaining monomer is made at a flow rate that ensures the formation of a copolymer of of constant composition. In the third, the initial charge is the same as in the previous case with subsequent addition of the remaining monomer at a constant fed rate. The copolymer composition obtained under starved conditions was almost constant in the cases where low feed rates were used. however, this led to long process times. For the second policy, a mathematical model ws developed to calculated the necessary addition rate of the more reactive monomer, that ensured the production of a copolymer of constant composition. It was found that the resulting process time was one third of that corresponding to the starved process. When variations in a copolymer composition were allowed, the third addition polycy might prove to be a good alternative to the second addition polyce because of iots shorter process time and teh advantage of working with teh constant feed rate.
Effect of the fine structure and electrolytic contaminations on the specific conductance of some cellulosic materials
Authors: Moteleb M. M. Abdel , Shinouda H. G.
Published: April 2003

From dielecric loss measurements the specific conductance of some cellulosic materials of different fine structure free of and constaminated with electrolytic impurities in the temparature range of 283.15–333.15 K was determined. Also the activation energy of conductance for the different samples examined was calculated. Based on the data obtained and the discussion given, it is now possible to view the conductivity of the complex structure cellulosic substances in a much clearer light.
Effect of particle volume fraction on crack‐tip crazes in high impact poly(methyl methacrylate)
Authors: Mauzac O. , Schirrer R.
Published: April 2003

The fracture behavior of a PMMA toughened by small (0.2 μm diameter) rubber particles was investigated over a wide range of rubber particle volume fractions. Crack tip morphology, material toughness, and fracture surfaces were studied. Whereas isolated particles have no effect, interactions between particles strongly modify the fracture behavior. Interactions occur via two different mechanisms: (i) an overlap of the stress enhancements due to particles, which is a function of the ratio of the distance between particles versus particle diameter; (ii) a geometrical “sifter” effect, which occurs when the distance between particles is less than the craze thickness.
Plasma surface treatment on nylon fabrics by fluorocarbon compounds
Authors: Iriyama Yu , Yasuda Takeshi , Cho D. L. , Yasuda H.
Published: April 2003

Nylon fabrics were treated by low temperature fluorocarbon plasmas. All of the fluorocarbon plasmas applied altered the surface of nylon fabrics to be hydrophobic and water‐repellent. The durability of hydrophobicity and water repellency was examined by measurements of the water contact angle, the water droplet rolling‐off angle, and the breakthrough water pressure after plasma‐treated fabrics were washed. It was found that the structure of starting fluorocarbon and the plasma energy input were important factors in the durability. After washing, surface dynamics were investigated on different drying conditions. It was found that chemical composition and water repellency were dependent on drying conditions because of rotation of hydrophobic segments on the surface of fabrics.
DMA and ATR FT‐IR studies of gas plasma modified silicone elastomer surfaces
Authors: Urban Marek W. , Stewart Mark T.
Published: April 2003

The results obtained from ATR FT‐IR and DMA studies of gas/plasma surface modified silicone elastomers are presented. The structural analysis indicates that, upon the plasma treatment in the presence of argon and carbon dioxide gases, the primary components of the surface are short chain layers with carbonyl groups. Their presence significantly influences the viscoelastic properties of the elastomer. The measurements of the storage modulus (E′) indicate a substantial decrease of the crosslink density upon the plasma treatment. Although the glass transition temperature also changes, these changes do not follow the trend observed of E′ values, and primarily depend on the chemical structures that develop upon the treatment. On the other hand, the ammonia–plasma surface modification introduces surface amide groups on the surface of the silicone elastomer, which effectively contribute to the increase of both Tg and storage modulus of the elastomer.
Influence of molecular weight and molecular weight distribution on the tensile properties of amorphous polymers
Authors: Bersted B. H. , Anderson T. G.
Published: April 2003

Tensile property data for polystyrene samples of varying polydispersity are correlated with various parametric measures of molecular weight. Traditional measures of molecular weight, such as M̄n, M̄w, and M̄z, are shown to be unable to account for the variation of tensile properties with molecular weight. However, a new molecular weight parameter, termed the failure property parameter, is able to provide a single relationship between tensile strength and the parameter for both the broad and narrow distribution polymers. The form of this parameter is consistent with its having origins in the view that it is the entanglement network in an amorphous polymer that provides the observed strength properties. Specifically for polystyrene, the failure property parameter results indicate that material below 60,000 molecular weight does not contribute to polymer strength. Although the results of this investigation are specifically for polystyrene, the arguments used to develop the failure property parameter are not dependent on polymer chemical structure. Consequently, we believe that both the concepts and definition of this new parameter are applicable to all amorphous polymers.
Effects of fibers on the crystallization of poly(phenylene sulfide)
Authors: Desio Glenn P. , Rebenfeld Ludwig
Published: April 2003

The isothermal crystallization of unreinforced poly(phenylene sulfide) (PPS) and PPS filled with glass, carbon, and aramid fibers was studied by differential scanning calorimetry. The Avrami exponent and rate constant are reported, but the crystallization half‐times were used to compare the effects of different fibers on the rate of PPS crystallization. The aramid and carbon fibers decreased the crystallization half‐time with the aramid fiber having the most pronounced effect. The glass fibers affected the crystallization half‐time only at the higher crystallization temperatures. The aramid filled PPS exhibited anomalous degree of crystallinity behavior in that the degree of crystallinity passed through a minimum as a function of temperature. The other systems all exhibited increasing degree of crystallinity with increasing crystallization temperature. Finally, the Avrami plot for the aramid filled PPS is not linear, and the data are fitted better with two linear regions indicating that two types of crystallization processes may be present.
Kinetic study of ethylene polymerization by highly active silica supported TiCL4/MgCl2 catalysts
Authors: Kim Il , Kim Jae Ha , Woo Seong Ihl
Published: April 2003

The kinetics of ethylene polymerization with TiCl4/MgCl2/SiO2 has been investigated in the range of temperatures between 40 and 90°C and in the range of ethylene pressures between 4 and 12.4 kg/cm2. The role of MgCl2 was discussed from the dependence of the Mg/Ti ratio on the catalytic activity. The polymerzation rate was first order with respect to the monomer concentration and the dependence of the polymerization rate on the concentration of Al(C2H5)3 could be described by the Langmuir–Hinshelwood mechanism. The dependence of initial rate and the time to reach the maximum polymerization rate on the concentration of Al(C2H5)3 was also discussed. Polymerization rates as a function of the polymerization temperature showed a maximum and the activation energy was 11.8 kcal/mol between 50 and 80°C. The polymerization rate decreased with the increase of hydrogen partial pressure. The active site concentration (C*) was 1.9 × 10−2 mol/mol Ti by the inhibition method with carbon monoxide.
Oxygen permeability of teflon–PFA tubing
Authors: Giacobbe F. W.
Published: April 2003

The permeability coefficient for oxygen diffusing through a sample of Teflon‐PFA tubing was determined experimentally. The source of the diffusing oxygen was ambient temperature air surrounding a coiled length of the PFA tubing. High pressure nitrogen was directed through the center of the PFA tubing. Oxygen permeating from the low pressure ambient air source, through the PFA tubing, and into the flowing high pressure nitrogen was observed in the effluent gases as they passed through a trace oxygen analyzer. By this means, oxygen concentrations in the effluent nitrogen were determined as a function of varying nitrogen flow rates, at nitrogen gas pressures of 4.4 and 7.8 atm (absolute), within the tubing bore. All measurements were also carried out at ambient temperatures of 21 ± 1°C. In addition, a theoretically related graphical method of evaluating the experimental data was developed and subsequently employed to actually determine the oxygen permeability coefficient for this system.
Vapor phase photografting on low‐density polyethylene film in binary monomer systems
Authors: Kubota Hitoshi , Yoshino Nobuyuki , Ogiwara Yoshitaka
Published: April 2003

Vapor phase photografting of monomer mixtures on low‐density polyethylene film, on which benzoyl peroxide is coated, was investigated at 60°C using various vinyl, allyl, and solid monomers. Styrene (St) itself was difficult to graft on the film substrate, but the combinations of St with vinyl monomers such as acrylonitrile (AN), glycidyl methacrylate (GMA), acrylic acid, and methacrylic acid led to the accelerated grafting, affording a maximum percent grafting at an certain monomer ratio. The same combination effect was observed for AN–N‐vinyl pyrrolidone and –GMA monomer mixtures. The monomer combinations such as allyl aldehyde–St and allyl alcohol–maleic anhydride were useful for performing the grafting of allyl monomers effectively. Maleic anhydride and maleimide as solid monomers were also possible to introduce into the film substrate by means of the monomer combination, where St, N‐vinyl pyrrolidone, vinyl ethers, and benzyl methacrylate were available as comonomers. Thus, the monomer combinations affording an accelerating effect on grafting may be monomer pairs rich in an alternative copolymerizability, suggesting that monomer reactivity ratio controls a major factor for the combination effect. It was confirmed from IR study on grafted films that both monomer components are introduced in the film substrate as the grafted chain component.
Modeling of poly(ethylene terephthalate) reactors. IX. Solid state polycondensation process
Authors: Ravindranath K. , Mashelkar R. A.
Published: April 2003

A mathematical model for simulation of industrial process of solid state polycondensation of poly(ethylene terephthalate) (PET) has been developed. The model eliminates errors evident in the earlier models by proper formulation. The model results have been validated by experimental data in the literature. It enables prediction of the influence of particle shape, size, temperature, etc. on the polycondensation process correctly in all different regimes of operation, apart from bringing out the importance of gas‐side resistance, influence of carrier gas, etc. for the first time.
Fluorescent properties of polymer–rare earth ion complexes. II. Poly(acrylic acid‐co‐acrylamide)–rare earth ion complexes
Authors: Lu Hong , Li Gao‐Fen , Fang Shi‐Bi , Jiang Ying‐Yan
Published: April 2003

Poly(acrylic acid‐co‐acrylamide) with uniform composition was synthesized from acrylic acid and acrylamide by azeotropic copolymerization. The fluorescent properties of the copolymer–Eu3+ or −Tb3+ complexes were investigated. It was found that the fluorescence intensity of the complexes is dependent on the composition of the copolymer. Fluorescence lifetime measurement indicates that Eu3+ or Tb3+ exists in the complexes in at least two coordination forms, and the difference of the nature or relative quantity of the coordination forms varies with the composition of the copolymer. The fluorescence lifetime of Eu3+ or Tb3+ in the complexes is also dependent on the composition of the copolymer. It was also found that intramacromolecular hybrid coordination of oxygen containing and nitrogen containing coordination groups makes Eu3+ or Tb3+ fluoresce more strongly than intermacromolecular hybrid coordination of the two types of coordination groups does.
Chemical toughening of epoxies. I. Structural modification of epoxy resins by reaction with hydroxy‐terminated poly(butadiene‐co‐acrylonitrile)
Authors: Sankaran S. , Chanda Manas
Published: April 2003

In an attempt to toughen the epoxy resin matrix for fiber‐reinforced composite applications, a chemical modification procedure of a commercially available bisphenol‐A‐based epoxy resin using reactive liquid rubber HTBN [hydroxy‐terminated poly(butadiene‐co‐acrylonitrile)] and TDI (tolylene diisocyanate) is described. The progress of the reaction and the structural changes during modification process are studied using IR spectroscopy, viscosity data, and chemical analysis (epoxy value determination). The studies support the proposition that TDI acts as a coupling agent between the epoxy and HTBN, forming a urethane linkage with the former and an oxazolidone ring with the latter. The chemical reactions that possibly take place during the modification are discussed.
Chemical toughening of epoxies. II. Mechanical, thermal, and microscopic studies of epoxies toughened with hydroxyl‐terminated poly(butadiene‐co‐acrylonitrile)
Authors: Sankaran S. , Chanda Manas
Published: April 2003

Diglycidyl ether–bisphenol‐A‐based epoxies toughened with various levels (0–12%) of chemically reacted liquid rubber, hydroxyl‐terminated poly(butadiene‐co‐acrylonitrile) (HTBN) were studied for some of the mechanical and thermal properties. Although the ultimate tensile strength showed a continuous decrease with increasing rubber content, the toughness as measured by the area under the stress‐vs.‐strain curve and flexural strength reach a maximum around an optimum rubber concentration of 3% before decreasing. Tensile modulus was found to increase for concentrations below 6%. The glass transition temperature Tg as measured by DTA showed no variation for the toughened formulations. The TGA showed no variations in the pattern of decomposition. The weight losses for the toughened epoxies at elevated temperatures compare well with that of the neat epoxy. Scanning electron microscopy revealed the presence of a dual phase morphology with the spherical rubber particles precipitating out in the cured resin with diameter varying between 0.33 and 6.3 μm. In contrast, a physically blended rubber–epoxy showed much less effect towards toughening with the precipitated rubber particles of much bigger diameter (0.6–21.3 μm).
Blends of low density polyethylene/plasticized poly(vinyl chloride): The rheological, morphological, and mechanical characterization
Authors: Mikkonen Raija , Savolainen Antti
Published: April 2003

An experimental study was conducted to investigate the rheological, morphological, and mechanical properties of a heterogeneous polymer blend system consisting of low density polyethylene (LDPE) and plasticized poly(vinyl chloride) (PVC). The components were mixed using a single‐screw extruder, which was equipped with a special measuring head for the determination of rheological quantities. The morphology of blends was examined by scanning electron microscopy. Die swell was determined by photography. The velocity of ultrasound through the polymer melt was also measured. The dependencies of viscosity, die swell, and ultrasonic velocity on blend composition were qualitatively similar, exhibiting a minimum at about 70 wt % PVC. The morphology of the blend system at this blending ratio was different from morphologies of the other blends. Tensile properties of blends, except elongation at break, were not significantly inferior to those of the LDPE component.
Correlation of mechanical and acoustical properties of plasticized epoxy polymers
Authors: Prassianakis J. N.
Published: April 2003

In the present experimental work the influence of the percentage of plasticizer on the mechanical and acoustical properties of the plasticized epoxy polymers was studied. The velocity cl of the longitudinal waves and the acoustic attenuation coefficient α were evaluated from the acoustical properties. Also the influence of curing time of plasticized epoxy polymers on the acoustical properties, cl and α, was examined and it was found out that these quantities tend to their limiting values when the polymerization is completed. Furthermore, the determined acoustical properties are correlated with the corresponding mechanical properties for the same materials, which were also considered in earlier papers. So, a simple and quick experimental nondestructive technique is provided for the evaluation of the elastic properties, as well as of the epoxy polymers composition, by determining the velocity cl of the longitudinal waves only.
Effects of core‐shell latex morphology on film forming behavior
Authors: Devon Michael J. , Gardon John L. , Roberts Glen , Rudin Alfred
Published: April 2003

A series of core‐and‐shell latex particles were made from methyl methacrylate/butyl acrylate copolymers. All latexes were almost monodisperse in particle size. The polymer hardness was varied by changing the methyl methacrylate/butyl acrylate ratio between the limits of 40/60 and 60/40 parts by weight. The minimum film temperatures(MFTs) of these particles were expected to vary with core and shell characteristics in the following order: soft/hard > medium/medium > hard/soft. In fact, this order was observed only if the shell thickness was greater than a certain minimum value that depends on the diameter of the core polymer. Thinner, softer shells on harder cores may require higher drying temperatures than thicker shells with the same composition because the former are required to deform more to produce void‐free films.
Aqueous polymerization on clay surfaces. IV. Effects of hydrogen–montmorillonite, monomer concentrations, and temperature on the polymerization of methyl methacrylate
Authors: Bhattacharya J. , Talapatra S. , Saha S. K. , Guhaniyogi S. C.
Published: April 2003

The polymerization of methyl methacrylate in aqueous montmorillonite suspension with thiourea was studied. The polymerization initiated on the montmorillonite surface following the adsorption of thiourea and the monomer. A 20% increase in the basal spacings of the clay mineral was observed. A large fraction of the polymer was nonextractable and was found to be thermally more stable than the extractables. The rate of the polymerization increased with increasing amounts of clay, thiourea, and followed one‐half order on the latter. The apparent energy of activation (Ea) of the system was characteristic of redox free radical polymerization.
Properties of positive resists. III. The dissolution behavior of poly(methyl methacrylate‐co‐maleic anhydride)
Authors: Drummond Rashmi K. , Boydston Gail L. , Peppas Nikolaos A.
Published: April 2003

The dissolution characteristics of model positive resists were investigated through the use of various copolymers of methyl methacrylate and maleic anhydride. Dissolution in methyl ethyl ketone was found to be dependent on the radiation dose and on the composition of the copolymers. The Lee–Peppas dissolution model was used to calculate important parameters of this dissolution process. It was shown that the overall dissolution rate was initially controlled by the swelling process whereas the true disentanglement/dissolution process predominated during the latter portion of the overall phenomenon. In addition, the thickness of the formed gel layer was a function of the square root of time.
Poly(styrene‐co‐acrolein) latex particles: Copolymerization and characteristics
Authors: Yan Changhong , Zhang Xianming , Sun Zonghua , Kitano Hiromi , Ise Norio
Published: April 2003

Reactive microspheres suitable for binding proteins were prepared using emulsifier‐free emulsion copolymerizations of styrene (St) and acrolein (AL) with various molar ratios of monomers St and AL. A maximum polymerization rate was obtained when the molar ratio of the monomers was 1 : 1. The diameter of the latex particles increased with increase in the amount of monomer AL. The amounts of aldehyde groups on the latex particle surfaces were determined by conductometric titration. The binding capacity of the copolymer latexes with spacer molecules was also examined.
Dielectric relaxation properties in polypropylene–polyurethane composites
Authors: Bánhegyi G. , Karasz F. E. , Petrović Z. S.
Published: April 2003

AC dielectric relaxation properties of polypropylene/polyurethane composites have been studied. The segmented polyurethane (PUR) component contained a poly(propylene oxide) soft segment, and a diphenyl methane diisocyanate/butanediol hard segment. The molecular weight of the soft segment, the concentration of the latter in the polyurethane phase, and the PUR content of the blends were changed systematically. It was observed that the polypropylene is phase‐separated with respect to both PUR segments and that the dielectric relaxation properties are determined largely by the PUR component. Two transitions attributable to the glass transitions of the soft and hard phases, respectively, were observed. The soft segment transition temperature decreases with increasing molecular weight of the latter. The transition temperatures are somewhat dependent on the PUR content in the blend, indicating some interaction between the phases. Model calculations show that these shifts and some intensity anomalies are not due simply to the existence of a heterogeneous structure. The ohmic interfacial relaxation process does not play an important role in the temperature and frequency range studied.
Ink adhesion on corona‐treated polyethylene studied by chemical derivatization of surface functional groups
Authors: Lanauze J. A. , Myers D. L.
Published: April 2003

Corona discharge (CD) treated polyethylene films were examined using X‐ray photoelectron spectroscopy (XPS) and a variety of chemical derivatization techniques. The composition of the CD‐treated surfaces were found to be relatively unaffected by aging at temperatures between 70 and 80°F. Ink adhesion testing of films treated under progressively more serve conditions indicated the efficiency of adhesion varied directly with the severity of treatment. Derivatization of CDtreated polyethylene films with pentaflurophenylhydrazine (PFPH) resulted in the formation of a stable hydrazone complex. The PFPH complex extends the detection limit for enolizable carbonyl groups ca. eight‐fold and provides relative quantitation of the number of these groups on variously treated polyethylenes. Formation of the hydrazone complex destroyed ink adhesion, indicating that the complex had blocked the site responsible for chemical bonding to the ink. Adhesion of water‐soluble printing inks to CD‐treated polyethylene is a direct consequence of hydrogen bonding between enolic hydroxyls on the polymer surface and carbonyl groups of the ink.
Studies on impact modification of polystyrene (PS) by ethylene–propylene–diene (EPDM) rubber and its graft copolymers. II. PS/EPDM‐g‐(styrene‐co‐methylmethacrylate) blends
Authors: Shaw S. , Singh R. P.
Published: April 2003

The toughness of a polymer blend is one of the major factors deciding its practical application. An impact modified polystyrene (PS) is usually a multiphase system consisting of the thermoplastics and an elastomeric component. The heterogeneous character of such a system and the interfacial adhesion between the components determine its impact strength. The graft copolymer of ethlene–propylene–diene (5‐ethylidene‐2‐norbornene) rubber with styrene and methylmethacrylate is synthesized, characterized, and blended with polystyrene to improve its impact strength. It is observed that there is improvement in impact strength with the subsequent decrease of tensile strength. The improved impact strength has been discussed in terms of morphology, compatibility, and interfacial adhesion of graft copolymers with PS matrix.
Infrared spectroscopic and dielectric studies of swollen cellulose
Authors: Nada A. M. A. , Shabaka A. A. , Yousef M. A. , Abd‐El‐Nour K. N.
Published: April 2003

Infrared spectra of treated cotton linters and bleached cotton stalk pulp with different concentrations of ethylene diamine and zinc chloride solution are studied. The structural changes brought about by these treatments have been studied from infrared spectral diagrams. It is found that the crystallinity index calculated from the infrared spectral data of these treated pulps decreases with increasing concentration of ethylene diamine and zinc chloride. The decrease in the crystallinity index (Crl) of the treated pulp with zinc chloride is higher than in case of treatment with ethylene diamine (EDA). The detectable frequency change at the hydrogen bonded OH of cotton linters by treatment with zinc chloride and ethylene diamine reflects the contributions of this bond in the swollen pulp. The dielectric study of these treated pulps confirmed the molecular structural changes determined from IR spectroscopic study.
The effect of coagulant on the structure and properties of poly(p‐phenylene benzobisthiazole) fibers [PBZT]
Authors: Rakas M. A. , Farris R. J.
Published: April 2003

Fibers spun from anisotropic solutions of a lyotropic rigid‐rod polymer, poly(para‐phenylene benzobisthiazole) [PBZT], were coagulated into homogeneous nonsolvents including a solution of 18% iodine/82% ethanol, ethanol, and water. The effect of these coagulants on the structure and mechanical properties of the PBZT fibers was studied. Structural and mechanical studies were performed on as‐spun fibers. Wide‐angle X‐ray diffraction techniques have shown that fibers coagulated in the presence of iodine anions had d‐spacings that were unique, as well as d‐spacings that were characteristic of PBZT or iodine anions. Tensile and shear properties were highest in a fiber having a spin/draw ratio of 3 which contained 19.5% iodine species by weight. For these fibers, an average tensile strength of 2.2 GPa and a torsional modulus of 1.14 GPa was recorded. For fibers having this spin/draw ratio, and undergoing no post‐processing heat treatment or tension drying, these values are much higher than would be expected.
Studies on the role of organophosphites in polyester blends: I. 31P nuclear magnetic resonance spectroscopy
Authors: Carduner K. R. , Carter R. O. , Cheung M.‐F. , Golovoy A. , Van Oene H.
Published: April 2003

The utility of 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) for the identification of organophosphite polymer additives, their hydrolysis products, and for the determination of their concentration is demonstrated for bis‐(2,4‐di‐t‐butylphenyl) pentaerythritol diphosphite (BTBP) in polycarbonate. This additive undergoes a complex process of hydrolysis that leds to the formation of at least three new phosphous species. High‐resolution solution 31P NMR is used to help in the identification of the products of the stailizer chemistry.
Synthesis and characterization of oxyethylene containing polyamide‐imides
Authors: Avadhani C. V. , Wadgaonkar P. P. , Vernekar S. P.
Published: April 2003

Two nonlinear dihydrazides, namely 1,2‐bis(3‐hydrazinocarbonylphenoxy)ethane and bis[2(3‐hydrazinocarbonylphenoxy)ethyl] ether, were synthesized by the acylation reaction of hydrazine hydrate with the corresponding aromatic esters and were characterized by IR, 13C‐NMR, and mass spectroscopy. These dihydrazides were each polycondensed with dianhydrides, benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA) to obtain poly(amic acid) with ηinh 0.60–0.85 dL/g in dimethylacetamide solution. These poly(amic acid)s were soluble in polar aprotic solvents like dimethylacetamide (DMAc), dimethyl formamide (DMF) and could be cast into transparent, tough, and flexible films that were cyclodehydrated to obtain amorphous, thermally stable polyamide‐imides. The polymers were characterized by IR spectroscopy, X‐ray diffraction, and thermogravimetric analysis.
Permeation of mixed gases in glassy polymer membranes
Authors: Sada E. , Kumazawa H. , Xu P. , Wang S.‐T
Published: April 2003

Steady‐state permeation rates for pure CO2 and CH4 and the binary mixture through homogeneous dense polysulfone and polycarbonate membranes have been measured at 40°C and upstream pressures up to 26 atm. The pressure dependence of the mean permeability coefficients for CO2 and CH4 for all of the systems was simulated equally well in terms of the dual‐mode mobility models driven by gradients of chemical potential and concentration. The dual‐mode sorption and transport parameters used for evaluation of the mobility models are only those determined from sorption and permeation runs for a single gas. The approximate solution for the mean permeability coefficient of each component in a binary mixture was derived on the basis of the same mobility model driven by gradients of chemical potential. The deviation of approximate solutions from numerical ones remains less than 0.3%.
Graft copolymerization of poly(butyl methacrylate) onto wool in the presence of air and nitrogen atmosphere. I
Authors: Shukla J. S. , Tiwari S. C. , Dixit Subodh K.
Published: April 2003

Poly(butyl methacrylate) (PBMA) was grafted onto wool in the presence of air and nitrogen atmosphere using potassium persulphate (KPS) and thioacetic acid (TAA) as redox pair under different reaction conditions. The percentage grafting and efficiency were compared. The graft copolymer was characterized by scanning electron micrograph, thermogravimetry, and molecular weight.
The second‐generation polysulfone gas‐separation membrane. II. The relationship between sol properties, gel macrovoids, and fiber selectivity
Authors: Kesting R. E. , Fritzsche A. K. , Cruse C. A. , Moore M. D.
Published: April 2003

All integrally skinned asymmetric membranes contain some defects which are attributable to the incomplete coalescence of the nodule aggregates of which the skin layer is composed. When such defects are small in size and few in number, they can be effectively sealed by coating with a highly permeable polymer. The resulting composite then exhibits the selectivity to gas permeation which is characteristic of the base polymer. Prior to their sealing, therefore, such membranes can be said to exhibit the potential for intrinsic selectivity. However, not all gas separation membranes can be effectively sealed. In the present study the relationship between sol properties, the presence of macrovoids in the substructure of the gel, and the subsequent failure of the fibers to achieve the potential for intrinsic selectivity are considered. Macrovoid‐free fibers with the potential for intrinsic selectivity can be prepared by the utilization of high viscosity, high total solids sols with low nonsolvent tolerance whose solvent vehicles consist of appropriate Lewis acid: base complexes.
Morphology of polymer films and single molecules
Authors: Howell Barbara , Reneker Darrell H.
Published: April 2003

Seven polymeric substances were examined by high‐resolution transmission electron microscopy. Features on the scale of the diameter of single molecular chains were observed. Polymers examined include (1) linear polyethylene (Mw = 52,000), (2) linear polyethylene (Mw approximately 5,000,000), (3) poly(cis‐1,4‐butadiene), (4) poly‐γ‐benzyl‐L‐glutamate, (5) poly(etheretherketone) (PEEK), (6) deuterated polystyrene‐poly(methylmethacrylate) (PMMA) block copolymer, and (7) a polydiacetylene, poly(1,12‐di(butoxy‐carbonylmethylurethanyl)‐5,8‐dodecadiyne), also called poly‐4BCMU. A variety of methods were used to prepare dispersed single molecules and very thin films, some of which had regions with strands containing only a few molecules. Staining with RuO4 revealed structures near the surface of the films that were reproducible and characteristic of each polymer.
Prediction of dynamic properties of plastic foams from constant–strain rate measurements
Authors: Ramon Ori , Miltz Joseph
Published: April 2003

This study demonstrated how cushioning curves can be predicted from constant‐strain rate measurements and a limited number of stress‐relaxation or drop experiments. For rate‐independent foams, only one stress‐strain curve and the proposed dynamic model are required. For rate‐dependent foams, however, a computer and appropriate software are also needed to predict accurately cushioning curves.