bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallinity in PPS–carbon composites: A study using diffuse reflection FT‐IR spectroscopy and differential scanning calorimetry
Authors: Cole K. C. , Noël D. , Hechler J.‐J. , Wilson D. 
Published: April 2003

AbstractA method based on diffuse reflection Fourier transform infrared (FT‐IR) spectroscopy has been developed for determining the state of crystallinity in composite materials made from poly(phenylene sulfide) (PPS) reinforced with carbon fibers. Using this technique, good‐quality spectra can be obtained directly from the surface of prepreg or molded composite; thus the method is rapid and nondestructive. Several peaks in the spectrum are sensitive to the crystallinity and can be used for quantitative characterization purposes. The recommended indicator is the ratio of the heights of the peaks at 1075 and 1093 cm−1. Using a range of samples of varying crystallinity prepared by annealing amorphous prepreg, it has been shown that there is a very good correlation between this ratio and the enthalpy of crystallization as determined by differential scanning calorimetry. The effects of such annealing, as well as heating in air at high temperatures, have been investigated.
Thermal effects of heat‐resistant rubber blends. I. Joule heating effects in carbon black‐loaded NR/SBR blends
Authors: Hassan H. H. , Abdel‐Bary E. M. , Amin M. , El‐Mansy M. K. , Gouda M. E. 
Published: April 2003

AbstractA heat‐resistant rubber blend of natural rubber NR and styrene butadiene rubber (SBR‐1502) was prepared according to the standard techniques. The rubber blend was loaded with different concentrations of LAMP black and general purpose furnace (GPF) black for obtaining conductive rubber composites. The obtained vulcanizates were subjected to electrical conductivity measurements over a wide range of temperature and electric field. It was found that all samples showed negative values of temperature coefficient of conductivity (TCC). The temperature developed inside the samples by the Joule heating effect was recorded as a function of time (T–t) at different values of the initial applied DC‐electric power. The T–t dependence was found to obey an exponentially growing function with a time constant (τ), which was found to be dependent on the concentrations as well as the type of carbon black and the value of the initial applied power. The current–voltage characteristics of the samples showed a negative resistance behavior after a characteristic voltage (V*). It was noticed that V* decreases as the carbon black concentration increases.
Effect of aqueous swelling and stretching on the structure and properties of cotton
Authors: Doke S. S. , Iyer K. R. Krishna 
Published: April 2003

AbstractSpectacular changes in structure and properties of cotton have been found to result from swelling and stretching treatments in water. Fibers from one variety of cotton (Sudan) were swollen in water and stretched to their limit. While one lot was dried in the stretched state, another was allowed to dry in the slack condition after being subjected to stretch. The two types of treatments produced considerable changes in structural and physical properties, the stretch drying being more drastic. Enhancement of breaking load and tenacity without much loss in extensibility improved fibrillar orientation without change in crystallinity; reduction in ribbon width wall thickness and number of convolutions, etc. are some of the changes resulting from the treatment
Spinning of high‐molecular‐weight liquid crystalline polyarylates
Authors: Zimmerman J. 
Published: April 2003

AbstractAttempts to spin high‐molecular‐weight liquid crystalline polyarylates frequently lead to decreases in strength rather than increases as a result of draw resonance in spinning and formation of thick–thin yarns. This phenomenon is attributed to the onset of highly non‐Newtonian elongational flow behavior for these polymers. However, the use of small spinneret capillaries, (≤ 6 mils diameter) maintained at temperatures below the melting point of the polymer but above the freezing point, and selection of copolymers which have relatively low heats of fusion (≤ 10 J/g) can eliminate draw resonance and produce relatively high‐strength fibers (up to about 14 dN/tex) without heat strengthening. With critical selection of polymer composition (i.e., copolymers containing phenylhydroquinoneterephthalate as the major component and 1,4 hydroxybenzoic acid plus, optionally, a small amount of another monomer as minor components), spinning of high‐molecular‐weight polymers can be effected above the melting point of the polymers without draw resonance. Tensile strengths as high as 18 dN/tex (as‐spun) have been obtained in this way. A mechanism for these effects is proposed.
Investigation of the persulfate/itaconic acid interaction and implications for emulsion polymerization
Authors: Lock Michele R. , El‐Aasser Mohamed S. , Klein Andrew , Vanderhoff John W. 
Published: April 2003

AbstractItaconic acid, a carboxylated water‐soluble vinyl monomer, is shown to greatly induce the thermal decomposition of potassium persulfate initiator. From decomposition rate studies carried out at 50, 60, and 70°C, the rate constants for this interaction are found to be increased eight to 15 times as much over the values of rate constants from uninduced decompositions. The induction is found to be particularly sensitive to the concentration of the first anion of itaconic acid and is thought to lead to wastage of initiator radicals. As the polymerization temperature is increased from 50 to 70°C, this interaction between itaconic acid and persulfate leads to worsening monomer conversion levels in acrylate latexes made with both compounds. Employing a water‐soluble azo initiator in the presence of itaconic acid does not result in any induced decomposition of the former. Acrylate latexes prepared with these two compounds have monomer conversion levels which rise as the polymerization temperature is increased, as is expected in conventional emulsion polymerizations.
Thermal behavior of cellulosic graft copolymers. I. Cotton grafted with vinyl acetate and methyl acrylate
Authors: Fernández M. J. , Fernández M. D. , Casinos I. , Guzmán G. M. 
Published: April 2003

AbstractThe thermal degradation of samples of cotton, cotton oxidized by ceric ion, cotton grafted with vinyl acetate and methyl acrylate having different percent grafting yield, poly(vinyl acetate), and poly(methyl acrylate) has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The ceric ion redox system shows little effect upon thermic properties of cotton cellulose. Graft copolymerization of vinyl acetate makes cotton thermally less stable, while, in the case of methyl acrylate grafted cotton samples having 33, 83, and 174% grafting yield, the initial decomposition starts at lower temperatures; but decomposition beyond 360°C takes place at higher temperatures than those for ungrafted cotton, and in the case of the sample with 430% grafting yield the thermal stability is higher than that of original cotton. The thermal stability of cotton grafted with methyl acrylate is higher than that of cotton grafted with vinyl acetate. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.
Removal of methyl orange by systems of chloromethylated polystyrene–polyethylenepolyamines and –polyethyleneimines
Authors: Tashiro Tatsuo 
Published: April 2003

AbstractA study was made of the removal of methyl orange (MO) solutes in water by the reaction products of chloromethylated divinylbenzene crosslinked polystyrene (CMPS) with polyeth‐ylenepolyamines (PEPA), polyethyleneimines (PEI), and 2‐methyl‐2‐oxazoline (MeOZO). This behavior of such polymers in regard to the Klotz equation and Freundlich adsorption formula was also examined and noted to conform better to the former than to the latter. The constants of the Klotz equation were calculated. The amounts of MO removed with unit masses of the polymers and the effects of salts on removal were studied. A possible mechanism for removal is discussed.
Preparation and characterization of heterophase blends of polycaprolactam and hydrogenated polydienes
Authors: Lawson David F. , Hergenrother William L. , Matlock Mark G. 
Published: April 2003

AbstractThe preparation, analysis, testing, and structure determination of ultrahigh impact rubber‐toughened polycaprolactams (nylon 6) are described. Partially unsaturated hydrocarbon rubbers were used for this purpose. They were functionalized by reaction either in solution or in bulk with maleic anhydride to give rubbery “ene” adducts containing varying amounts of pendnet succinic anhydride. Tough, rigid, thermoplastic engineering resins with notched Izod impact strengths of 750–1000 J/m were prepared by briefly melt‐blending these adducts with nylon 6. Properties of the blends could be affected by the type and amount of elastomer used, the anhydride content, the type of nylon, the mixing conditions and the test conditions. Fractionation by coacervation in m‐cresol/cyclohexane of a typical resin containing 20% by weight of functionalized rubber showed approximately 35% of a rubber–nylon graft, along with a few percent of free rubber dispersed in the nylon 6 matrix. A comb‐block copolymer structure for the graft and a model for its formation are proposed, consistent with analyses of the fractions. Some of the blends prepared with partially hydrogenated medium vinyl polybutadiene–maleic anhydride adducts displayed a retention of impact properties at low temperatures which was superior to that obtainable with a similarly prepared EPDM‐modified nylon 6. Transmission electron microscopy of a blend containing an anhydride‐modified hydrogenated medium vinyl polybutadiene showed a morphology consisting of a nylon matrix containing finely dispersed, irregularly shaped, 0.03–0.55 μm rubber domains in which were found even smaller domains of nylon.
Optimization of diffusion‐controlled free radical polymerizations in lumped‐parameter systems
Authors: Huang Y. J. , Lee L. James 
Published: April 2003

AbstractOpen‐loop optimal temperature control strategies for the batch free radical polymerizations of styrene are investigated using the minimum principle. Two kinetic models, one considering the gel effect and the other incorporating both the gel effect and the glass effect, are employed. By using the Min‐H strategy, a control variable program that minimizes one objective function and yields values of other terminal quantities can be obtained. It is found that the optimal temperature programs are highly dependent upon the kinetic characteristics of reactions. The gel and glass effects, which control ultimate molecular weights, play important roles in affecting the temperature programs. Numerical examples using two objective functions, one in which reaction time is minimized, and the other in which molecular weight distribution is minimized, are presented. The theoretical predictions using kinetic model with the gel and glass effects are also compared with experimental measurements of conversion, molecular weight, and molecular weight distribution. Although the agreement between the experimental work and the theory is less than satisfactory, the trends of policy improvements are consistent.
Polymer latex particle size measurement through high speed dielectric spectroscopy
Authors: Sauer Bryan B. , Stock Ruth S. , Lim Kyung‐Hee , Ray W. Harmon 
Published: April 2003

AbstractDielectric techniques have been implemented to study aqueous colloidal suspensions. A four electrode cell was used in two configurations; the first, a sweep of frequencies using a sequence of standard single frequency null‐balance measurements, and the second relying on the dielectric response to a Fourier synthesized pseudo random white noise (FSPN) with measurements performed using correlation techniques in the time domain. Single frequency measurements, which take on the order of 5–10 min per spectrum, were performed on polymer latex standards of varying size, latex concentration, and electrolyte concentration and were extended from 0.02 to over 500 kHz. It was found that the central relaxation frequency fc was inversely propotional to the square of the particle size, consistent with previous experimental results. Experiments were performed at different particle concentration and ionic strengths, and the magnitude and breadth of the dielectric dispersion was analyzed in terms of current theories. The distribution of relaxation times was found to be in general qualitative agreement with those predicted by some existing theories. The results indicate that a wide range of conditions exist in terms of latex concentration and ionic environment where the rapid and accurate measurement of polymer latex particle size and size distribution is feasible. FSPN measurements, which take on the order of seconds, were shown to be accurate over a moderate frequency range for model electrical network studies but were only partially successful for aqueous suspensions of latex because of high frequency limitations in the electronics. Experimental details and difficulties concerning the application of this technique are discussed.
Consolidation of high‐modulus PET laminates and the role of chemical healing
Authors: Lertola J. G. , Schultz J. M. 
Published: April 2003

AbstractIn this work, a process for making high‐modulus (8GPa) laminates of poly(ethylene terephthalate) (PET) has been developed. Oriented films of the polymer were produced by a technique utilizing a very high extension rate, and these films were crossplied and consolidated to form the product laminates. The procedures for drawing the original film lamina and consolidating the laminates were optimized with respect to the material properties. Further, the possibility of chemical healing–bonding of the lamina together by chemical reaction, not diffusion–was investigated for these materials. It was found that laminates could be formed with both high moduli and strong interply bonding and that the moduli actually increase due to crystallization during pressing. Longrange diffusion during bond formation was ruled out, since crosslinked polyesters were found to bond as readily as uncrosslinked. Chemical reactions between contacted surfaces appear to be a likely mechanism of bonding.
Gas separation membrane made by plasma polymerization of 1,3‐ditrifluoromethylbenzene/CF4 mixture
Authors: Inagaki N. , Tasaka S. , Park M. S. 
Published: April 2003

AbstractPlasma polymerization of 1,3‐ditrifluoromethylbenzene (DTFMB)/CF4 mixture was investigated by means of elemental analysis and infrared spectroscopy and the permeation properties of the formed plasma polymer films were examined. The plasma polymerization deposited films containing fluorine atoms, of which the concentration depended on the starting composition of the DTFMB/CF4 mixture. The films were composed of fluorinated alkyl moieties with a small amount of fluorinated aromatic moieties and carbonyl moieties. The CF4 addition to DTFMB caused the breaking down of aromatic rings. Permeation properties of the plasma polymer films depended on the starting composition of the DTFMB/CF4 mixture, the discharge current, and the thickness of the deposited films. The permselectivity was enhanced by adding CF4 and increasing the discharge current. Plasma polymer films prepared from DTFMB/CF4 mixture containing 75 mol % CF4 at a discharge current of 150 mA had a permselectivity of 5.0 and an oxygen permeation coefficient of 3.5×10‐10 cm3 (STP) cm/cm2 s cm Hg.
Characteristics and annealing behavior of polyethylenes designed for use as underground insulation
Authors: Lee Y. D. , Phillips P. J. 
Published: April 2003

AbstractA series of polyethylenes developed for use as high voltage electric cable insulation have been studied. All crosslinked polyethylene materials show similar thermal aging characteristics, whereas linear low‐density polyethylene is susceptible to thermal aging at higher annealing temperatues. Tree‐retardant additives are soluble in xylene, but some are also attached to the gel network. They function both as enhanced antioxidants and as enhancers of electric breakdown strength. Biaxially oriented film shows the greatest resistance to electric breakdown.
Chemical modification of jute fibers. I. Permanganate‐initiated graft copolymerization methyl methacrylate onto jute fibers
Authors: Moharana S. , Mishra S. B. , Tripathy S. S. 
Published: April 2003

AbstractA study on the graft copolymerization of methyl methacrylate onto defatted jute fibers by using potassium permanganate as initiator has been made. To determine the optimum conditions for grafting, the effects of permanganate, monomer, acid, alkali treatment, time, and temperature on percentage of grafting have been studied. Kinetic studies showed that the overall reaction obeyed second order mechanism. The activation energy of the reaction has been found to be 4.34 kcal/mol. A suitable mechanism for the grafting process has been proposed. The grafted fibers have been characterized by thermogravimetric analysis (TGA, DTG, and DTA). It has been found that chemical modification of jute fiber by grafting process using permanganate as the initiator does not improve the tensile properties of the fibers.
Dynamic mechanical analysis of bismaleimidodiphenyl methane and diallylbisphenol‐A crosslinked polymers
Authors: Chattha M. S. , Dickie R. A. 
Published: April 2003

AbstractCrosslinked compositions prepared from bismaleimidodiphenyl methane and diallylbisphenol A in the weight ratio of 0.99 to 1.31 have been subjected to dynamic mechanical thermal analysis (DMTA). The glass transition temperatures of all these fully cured compositions are above 300°C. The stoichiometry of the reactants in the above range does not change the thermal degradation pattern of these crosslinked polymers. DMTA shows that there is a very small decrease in storage modulus at room temperature with increasing amount of diallylbisphenol A. The glass trnasition temperature decreases slightly as the amount of diallylbisphenol A increases; the Tg range is 330–339°C.
Fiber formation and characterization of a thermotropic LCP
Authors: Sarlin Juha , Törmälä Pertti 
Published: April 2003

AbstractOur work dealt with the spinnability of the commercial liquid crystal polymer Vectra A900 (Celanese Speciality Operations, Ltd.). The nonisothermal spinning was carried out using a pilotplant scale equipment and a monofilament die. The mass flow rate was constant while take‐up velocity was varied between 200 and 1100 m min‐1 and spinning temperature between 287 and 327°C. In the light of results it seems that the spin‐draw ratio is of little importance insofar as it is over 30, albeit the best tensile strengths and modulis were obtained with the highest spin‐draw ratio. The fibers showed the inhomogeneity in particular with high spinning temperatures. A SEM analysis of the fibers also showed that high spinning temperature is apt to produce defects in the fibers.
Effect of structure on properties of aromatic polyamides
Authors: Varma I. K. , Kumar Ramakant , Bhattacharyya A. B. 
Published: April 2003

AbstractPolyamides were prepared by reacting 3,5‐diamino benzoic acid (DAB) and/or 1,3‐bis (3‐amino benzamido) benzene (ABB) with terephthaloyl chloride in N, N‐dimethylacetamide. Five polymer samples having different contents of pendant carboxyl groups were prepared by changing the molar ratios of DAB: ABB in the initial monomer feed as 1: 0 (C), 3:1 (C3
A), 1:1 (CA), 1:3 (CA3), and 0:1 (A). The inherent viscosities of the polymers ranged from 0.198 to 0.478 dL/g. DSC and TG studies indicated loss in weight in the temperature range of 80–200°C due to absorbed moisture. The major loss in weight was observed above 400°C. The anaerobic char yield at 800°C depended on the backbone structure and was found to range from 25 to 40%. The resistivities of polyamide film was determined at 110 and 130°C and was found to decrease with an increase in carboxyl content. The dielectric constant of C and C3A polymer films was determined at frequencies ranging from 100 Hz to 1 MHz and at 110 and 130°C and was found to decrease with an increase in frequency or decrease in COOH content in the backbone.
HPLC analysis of polycarbonate oligomers and its process applications in the interfacial phosgenation reaction
Authors: Gu Jen‐Tau , Huang Shu‐Lang , Chang Feng‐Chih 
Published: April 2003

AbstractA liquid chromatographic method for the oligocarbonates and chloroformate‐containing oligomers at various stages in a typical polycarbonate phosgenation reaction has been developed. The accurate measurement of various types oligomers during phosgenation should allow for a better understanding of polymerization mechanism and provide great aid in defining the critical process parameters. Comparison of the total choloroformate concentration by accumulating every individual chlorofor‐mate‐containing componenent and the standard colorimetric method shows close agreement.
Effect of temperature on gas permeation of polymer blends. II. Copolyester/copolyester–polyurethane
Authors: Qipeng Guo , Hechang Xu , Dezhu Ma 
Published: April 2003

AbstractThe transport behavior of H2, N2, CO2 was studied for blends of an aliphatic copolyester with a copolyester‐polyurethane (PU) at various temperatures from 20 to 80°C. It was found that there was an abrupt change in slope near the melting point of the copolyester in Arrhenius plot of the permeability vs. temperature. This was considered to be due to the phase changes in the blends. The relationship between the logarithm of gas permeability and blend composition were only slightly dependent on temperature owing to the low degree of crystallinity of the copolyester; however, the activation energy of gas permeation for the blends had different values below and above the melting temperature of copolyester. The Tg measurements by DSC suggested that the copolyester/PU blends are miscible. However, the gas permeation measurements revealed the blends are not molecularly homegeneous. The miscibility of the blends did not extend to the angstrom level.
Transport of alkali metal and alkali earth metal ion against their concentration gradient through 2,3‐epithiopyl methacrylate‐methacryloyloxyethyl phosphoric acid copolymer membranes
Authors: Nonaka Takamasa , Egawa Hiroaki 
Published: April 2003

AbstractCationic exchange membranes were prepared with 2,3‐epithiopropyl methacrylate (ETMA)–methacryloyloxyethyl phosphoric acid (MP) copolymers. Transport of alkali metal and alkali earth metal ion against their concentration gradient through the UV‐irradiated and nonirradiated membranes was investigated by using the system, where one side (L side) of the membrane in a diaphragm cell was acidic and the other (R side) alkaline or neutral, under various conditions. The ETMA–MP copolymer membranes transported rapidly alkali metal and alkali earth metal ion against their concentration gradient and the maximum transport fraction was more than 95%. The transport rate and transport fraction of metal ions was greatly affected by the composition of the copolymer membranes and H+ concentration in the L side. The transport selectivity between alkali metal ions was increased by using the E8P2 membrane UV‐irradiated, but the degree of increase in the selectivity was not large. Ca2+ was transported more rapidly than Li+ against their concentration gradient.