bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface characterization of hydrophilic functional polymer latex particles
Authors: Tamai H. , Hasegawa M. , Suzawa T. 
Published: April 2003

AbstractSurface characteristics of styrene/acrylamide/acrylic acid copolymer and styrene/2‐hydroxyethyl methacrylate/acrylic acid copolymer latexes prepared without emulsifier using potassium persulfate as initiator and their colloidal stabilities were investigated. The negative ζ‐potentials decreased with increasing the amount of acrylamide and 2‐hydroxyethyl methacrylate copolymerized. In spite of the increase in surface charge density, the negative ζ‐potentials decreased through the maximum with increasing pH. The colloidal stabilities for NaCl concentration were remarkably enhanced with increasing both pH and the amount of acrylamide and 2‐hydroxyethylmethacrylate. These results suggest that the contration and expansion of water‐soluble polymer layer surrounding the particles play an important role in the surface properties.
Benzoyl‐peroxide‐initiated graft copolymerization of poly(ethylene terephthalate) fibers with acrylamide
Authors: Saçak M. , Pulat E. 
Published: April 2003

AbstractIn this study the grafting of acrylamide onto poly(ethylene terephthalate) fibers with the help of benzoyl peroxide and the effects of the temperature and the concentrations of initiator and monomer were investigated. Some of the experiments were repeated several times in order to check the reproducibility. The optimum temperature for grafting was found to be 75°C. The graft yield was observed to increase with the monomer concentrations examined. The graft yield increased up to the benzoyl peroxide concentration approximately 0.05 g/50 mL, and then passed a plateau, before showing a decrease. The fiber diameter, intrinsic viscosity, and the moisture regain increased while the fiber density decreased with the graft yield.
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

AbstractThe 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

AbstractRadiation‐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

AbstractThe 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

AbstractVarious 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

AbstractIn 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

AbstractThe 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

AbstractVinyl 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractMuch 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

AbstractWith 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

AbstractWhile 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

AbstractWith 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

AbstractThe 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

AbstractFrom 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

AbstractThe 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

AbstractNylon 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

AbstractThe 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

AbstractTensile 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.