bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of aqueous swelling and stretching on the structure and properties of cotton
Authors: Doke S. S. , Iyer K. R. Krishna
Published: April 2003

Spectacular 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

Attempts 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

Itaconic 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

The 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

A 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

The 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

Open‐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

Dielectric 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

In 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

Plasma 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

A 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

A 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

Crosslinked 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

Our 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

Polyamides 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

A 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

The 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

Cationic 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.
Durability of radiation‐sterilized polymers, XI. The effect of irradiation on rubber gloves
Authors: Kadir Zahrah Abdul , Yoshii F. , Hosoi F. , Makuuchi K. , Ishigaki I.
Published: April 2003

The effect of both gamma ray and electron beam irradiations on three rubber gloves are compared in relation to sterilization. Two of these gloves are sulfur vulcanized and the other is radiation vulcanized. It was found that the radiation‐vulcanized rubber gloves could be used, even at 25 kGy, the sterilization dose used. For all three gloves, it was found that the tensile strength and elongation at break are not significantly affected after irradiation in either gamma rays or electron beam or during storage. The tear strengths, however, decrease with increasing dose and storage, and it was found that degradation was higher in gamma rays than electron beam. The chemiluminescence data show that the rate of degradation is the highest in latex film followed by radiation‐vulcanized and sulfur‐vulcanized gloves.
CP–MAS NMR spectra of polyurethane–lignin blends
Authors: Natansohn A. , Lacasse M. , Banu D. , Feldman D.
Published: April 2003

Solid‐state high‐resolution C‐13 NMR spectra of lignin, a polyurethane, and their blend give information about phase structure and interactions in the blend. As the Tg values indicate, this is an incompatible blend, and values of the spin–lattice relaxation times in the rotating frame confirm tthat there are two separate phases in the blend. However, buildup of magnetization wiitthin the two phases clearly indicates some interactions between the phases, which allow transfer of magnetiization from lignin to the polyurethane.
Thermal conductivity of a polymer filled with particles in the wide range from low to super‐high volume content
Authors: Agari Y. , Ueda A. , Tanaka M. , Nagai S.
Published: April 2003

Polyethylene and polystyrene composites filled with high‐volume content of filler particles (quartz or Al2O3) were prepared by ordinary melt‐casting method to effectively increase the thermal conductivity. The result, however, suggested that fractional void volume cssentially occupied by filler particles is left unfilled when high or super‐high content of filler is used. After investigating the relation between the mixing ratio of different sized filler particles and the fractional voidage under various compression intensities, a mixture of filler was found to give minimum fractional voidage. Polymers filled with such an optimum mixture of fillers for minimum fractional voidage were then prepared under compression. Thus, expected monotonous increases in thermal conductivity in the wide range from low to super‐high filler content were obtained. Further, it was confirmed that a predictive model proposed by us agreed quite satisfactorily with the experimental data in comparison with many other models.
Solubility and diffusivity of sulfur dioxide in latex paint films
Authors: Hendricks B. J. , Balik C. M.
Published: April 2003

Sorption of SO2 in latex paint films is measured as a function of time. This data is used to extract the solubility (S) and the diffusion coefficient (D) for SO2 in these films. The solubility of SO2 in each of the samples follows Henry's law behavior. Sorption occurs only in the polymer, with the inorganic pigment particles acting as impenetrable fillers. The diffusion of SO2 is Fickin with an exponential dependence upon the concentration of SO2. This data is used to calculate the permeabilities of the paint samples to SO2, at levels typically found in the atmosphere.
Studies on the role of organophosphites in polyester blends: II. The inhibition of ester‐exchange reactions
Authors: Cheung M.‐F. , Carduner Keith R. , Golovoy A. , Van Oene H.
Published: April 2003

Ester‐exchange reactions during melt extrusion of polyarylate, polycarbonate, and polyethylene terephthalate ternary blends result in a decrease of the melting point and the heat of fusion of the poly(ethylene terephthalate). When an organophosphite is used to suppress the ester‐exchange reactions, it was found that whenever the phosphite is converted into a phosphonate, there is little change in both the melting point and the heat of fusion of the polyethylene terephthalate during prolonged exposure to high temperature in the blends. 31P nuclear magnetic resonance is employed to investigate the chemical changes and differential scanning calorimetry to evaluate the thermal stability of the blends. The organophosphite appears to be transformed through side‐chain hydrolysis into other phosphorous species, such as diphosphonate in order to be an effective suppressant of the ester‐exchange reactions.
Determination of the entanglement molecular weight of thermoplastic elastomers by tensile retraction measurements
Authors: Hergenrother William L. , Doshak John M.
Published: April 2003

The molecular weight between crosslinks was measured as a function of the maximum extension to which samples of solution cast films of ABA triblocks were tested. These measurements were done by applying the kinetic theory of rubber elasticity to the retraction portion of a tensile hysteresis curve. The molecular weight between chain restrictions, as determined by extrapolation to 0% elongation, was found to be identical to the entanglement molecular weight normally associated with the polybutadiene or polyisoprene that was used for the center block. The disentanglement of the small amount of AB diblock present could also be followed by fitting the data collected to what could be pictured kinetically as a simultaneous first‐and second‐order loss of crosslink density.
Ultrahigh molecular‐weight polyethylene–chalk composites resulting from in situ polymerization
Authors: Gorelik V. M. , Fushman E. A. , Topolkaraev V. A. , Dyachkovsky F. S. , Shestenina L. A. , Borisova L. F. , Sergeev V. I.
Published: April 2003

Ethylene polymerization on chalk surface under the action of TiCl4–organoaluminium compound systems yields filled composites possessing high stress–strain properties and preserving their ductility up to the chalk content of 60–70 wt %. The kinetics of the process and the properties of the composites have been investigated, as well as the interrelation between catalyst fixation technique, polymerization rate, and the ductile properties of composites containing 50 wt % of chalk. The conditions leading to the formation of “homogeneous” composites with a high ductility are examined. The possible causes of the formation of composites with a low value of elongation at break are analyzed. The principal regularities of the mechanical behavior of composites are considered for the case when the process is taking place on the filler surface and leads to “homogeneous” composites.
The effect of surface treatments on wear of polytetrafluoroethylene
Authors: Deli Gong , Qunji Xue , Hongli Wang
Published: April 2003

This paper reports the effect of surface chlorination, oxidation, and phosphatization of carbon steel, copper, and aluminum, and surface treatment with sodium naphthalenide of PTFE on wear of PTFE. It was found that the wear behavior of untreated PTFE is not affected by surface treatments of metals but treatment of PTFE can reduce its wear by a factor of at least 100. The wear mechanism of PTFE is discussed.
Emulsion copolymers of α‐methylstyrene and styrene
Authors: Branston Randolph E. , Plaumann Heinz P. , Sendorek Jerzy J.
Published: April 2003

The preparation of copolymers of α‐methylstyrene and styrene in an emulsion system is described. At both 40 and 60°C, there was no evidence of deviation from simple kinetics. Polymers of high molecular weight and high and high α‐methylstyrene content showed good thermal properties such as Tg and softening point. However, these polymers proved to be awkward to process due to a strong proclivity to degrade under shearing conditions.
Differential scanning calorimetry cure studies on the effect of addition of epoxy diluents of tetrafunctional epoxy resins
Authors: Jagadeesh K. S. , Siddaramaiah  , Kalpagam V.
Published: April 2003

The effect of the addition of p‐aminophenol and aniline‐based epoxy diluents on the curing behavior of highly viscous tetraglycidyl diamino diphenyl methane resin with diamino diphenyl sulfone hardener have been investigated kinetically by differential scanning calorimetry. Dynamic scans were carried out over a temperature range 30–300°C for different resin formulations. Isothermal scans at four differnt temperatures have also been carried out for the evaluation of kinetic parameters. Heat flow measurements at different heating rates have indicated the evidence of autocatalytic behavior of curing reaction following a simple nth‐order kinetics.
Multiple endotherm melting behavior in relation to the morphology of poly[3,3‐ bis(ethoxymethyl) oxetane]
Authors: Fay J. J. , Murphy C. J. , Sperling L. H.
Published: April 2003

Two crystalline melting peaks have been observed by differential scanning calorimetry for low molecular weight poly[3,3‐bis(ethoxymethyl) oxetane] (polyBEMO) samples, Mn < 1 × 104 g/mol, whereas only one melting peak has been observed for samples of higher molecular weight, Mn < 1 × 104 g/mol. Crystallization of low molecular weight samples at large supercoolings produces the lower melting form while low supercooling or annealing favors the higher melting species. Enthalpy of fusion values obtained by DSC for a multiple melting endotherm sample range from 28 to 39 J/g for crystallization temperatures from 58 to 35°C, respectively. Optical microscopy studies indicate that the lower melting peak corresponds to a spherulitic type morphology and the higher melting peak correlates to a fine grained crystal structure. Wide angle X‐ray powder diffraction studies do not detect differences in the crystal structures of samples exhibiting either one or two melting peaks, which suggests that the multiple melting phenomenon is due to differences in morphology rather than the presence of different crystal forms.
Modeling of polymerization of urea and formaldehyde using functional group approach
Authors: Kumar A. , Sood A.
Published: April 2003

The urea formaldehyde polymerization has been modeled using the functional group approach, which accounts for the formation of higher oligomers. The kinetic model involves four molecular species and three rate constants, as opposed to six as proposed in earlier studies. The experimental data of Price et al. have been curve fitted using our model, which is found to describe them very well in the entire range of temperature and urea formaldehyde ratio. Based on the activation energies, it has been argued that the reverse reaction step must involve the condensation product, water.
Fractionation and characterization of polyacetal copolymers by column elution method
Authors: Ogawa Toshio
Published: April 2003

Sufficient fractionation was attained for polyacetal copolymers by the column elution method. The characteristics of molecular weight, composition, and sequence length of the original copolymers were evaluated through the analyses of fractions by 1H‐NMR, GPC, and DSC. Comonomer content in polymer fractions decreased with the increase of molecular weight in any samples, and the copolymer prepared by gas‐phase polymerization showed broad compositional distribution as compared with that by solution polymerization.
Rubber‐modified polystyrene from multistage latexes: Rheological and physical properties
Authors: Silverstein M. S. , Narkis M.
Published: April 2003

The combination of rubbery and rigid polymers in a multiphase structure using staged emulsion polymerization has yielded materials with properties ranging from reinforced elastomers to high impact plastics. The many different particle morphologies that result from multistage latexes include core/shell, domain, interpenetrating polymer networks, and various combinations thereof. The present work focuses on rubber modified polystyrene (polyacrylates (PA) and polystyrene (PS) in a 1:3 ratio). The nature of the rubber‐modified polystyrene from multistage latexes has been determined through a combination of microscopy and mechanical property analyses. The uncrosslinked PS shells that form around the crosslinked PA seed particles with grafted PS microdomains coalesce upon molding to form a continous thermoplastic PS matrix that may absorb impact energy through mechanisms of crazing and shear yielding. The crosslinking of the acrylate seed with butadiene enhances PS grafting through residual unsaturation and thus affects the effective particle volume fraction and particle‐matrix interaction in these rubber‐modified PS materials. The substitution of some of the uncrosslinked PS of the second stage with crosslinked PS in a separate intermediate stage, resulting in a three‐stage latex, also affects the effective volume fraction and the particle‐matrix interaction through enhanced PS grafting and the formation of interpenetrating networks. In flow the rubber modified PS exhibits a Newtonian plateau at low shear, unlike crosslinked particles which flow through a particle slippage mechanism, and an unexpected deviation from power law behavior at high shear with a viscosity plateau, or even a slight increase in viscosity. These materials may essentially flow through molecular deformation, depending upon the temperature, molecular weight, particle‐matrix interaction, and level of shear. The rubber‐modified PS from the multistage latexes are a potential high impact material whose unique structure and chemistry distinguish it from commercial high impact PS (HIPS), although its mechanical and impact properties are, at the very least, similar to those of HIPS.
Preparation and characterization of hydroxamic acid derivative and its metal complexes derived from cellulose
Authors: Maekawa Eiichi , Koshijima Tetsuo
Published: April 2003

Cellulose‐hydroxamic acid derivatives, which were reported as a novel cellulose derivative were prepared from dialdehyde celluloses obtained by periodate oxidation of cellulose, and certain properties of unusual cellulose derivative containing hydroxamic acid groups and of various metal complexes formed with heavy metal ions were characterized in this investigation.
Surface modification by continuous graft copolymerization. I. Photoinitiated graft copolymerization onto polyethylene tape film surface
Authors: Yao Zhang Pei , RÅNby Bengt
Published: April 2003

A process has been developed for continuous photoinitiated graft copolymerization of acrylamide (AM) and acrylic acid (AA) onto the surface of high‐density polyethylene (HDPE) tape film, presoaked in a solution containing monomer and initiator under nitrogen atmosphere. As photoinitiator we have used benzophenone, which is efficient for photografting of polyolefins with acrylic monomers. The presoaking procedure of the tape film is very important for efficient photografting within short irradiation times. In ESCA spectra of the grafted tape film the relative intensity of the nitrogen over carbon peaks of film grafted with acrylamide is about 5–10% after 6 s irradiation time. The relative intensity of oxygen over carbon peaks in ESCA spectra of film grafted with acrylic acid is about 10–20% after 8 s irradiation time. The effects of varying the monomer concentration in presoaking solution and the different irradiation conditions on the grafting yield have been investigated. This technique has the advantages of being a continuous process with short irradiation times without requirements of vacuum conditions and appears to be promising for practical applications.
A preliminary correlation between macroscopic and microscopic polymer properties: Dynamic storage modulus vs. CPMAS NMR cross polarization rates
Authors: Parker A. A. , Marcinko J. J. , Shieh Y. T. , Hedrick D. P. , Ritchey W. M.
Published: April 2003

A correlation has been established between the dynamic storage modulus (E') and the mean cross polarization time constants 〈TCH〉 for a set of five morphologically diverse polymers, including one at two temperatures and one at two plasticizer concentrations. The correlation is only possible when the TCH values for all of the motional environments within the polymers are considered. An inversion recovery cross polarization (IRCP) NMR technique is used to obtain motional and morphological information from the main chain carbons of each polymer. After comparing simplified correlation functions for the two parameters, an experimental relationship between them is established that suggests that TCH and E' are both modulated by a similar distribution of molecular motions.
Mechanical and dielectric properties of cyanoethylated wood
Authors: Yamawaki Yukio , Morita Mitsuhiro , Sakata Isao
Published: April 2003

The mechanical properties and dielectric properties of film specimens from cyanoethylated wood (CE‐wood) which is a mixture of CE‐(cellulose, hemicellulose, and lignin) were investigated and compared with those of cyanoethylated cellulose (CEC). From the dynamic mechanical measurement for CE‐wood, it was observed distinctively that the segmental motions of the main chains were restrained by lignin. But these restraints were released with chlorination of CE‐wood. The dynamic behavior for chlorinated CE‐wood was similar to that for CEC. It was found that the CE‐wood was plasticized effectively by blending with cyanoethylated poly(vinyl alcohol) (CE‐PVA). The dynamic and static modulus of CE‐wood decreased with increasing the CE‐PVA fraction in the blended film, and the change of tensile strength at break for the CE‐wood polyblends showed a maximum value at the CE‐PVA fraction of ca. 40%. It was found that CE‐wood which contained lignin showed very high values of dielectric constant comparable to those of CEC which was well known to be a high‐performance dielectric materials. These dielectric properties were attributed to the segmental motion of the side chains, and it was tough that the behavior of the side chain was not so much influenced by the lignin as that of the main chain. CE‐wood film specimens could be drawn to threefold the initial length in acetone aqueous solution. The degree of orientation measured by optical method increased rapidly at the early stage of drawing. The Young's modulus and the tensile strength at break of the high‐drawn specimen increased to as much as three or four times those of the undrawn one, and the elongation at break changed little.
In situ polymerization of nylon–polyurea block copolymers. I. Synthesis and characterization
Authors: Gardlund Zack G. , Bator Mary Ann
Published: April 2003

The synthesis of a carbamyl caprolactam terminated polyurea and a series of nylon–polyurea block copolymers has been accomplished. In addition to reaction profiles and thermal properties, proof of block copolymer formation is described.
Polyamic acid interactions at metal surfaces
Authors: Linde H. G.
Published: April 2003

Pyromellitic dianhydride‐oxydianiline (PMDA‐ODA)‐derived polyamic acid‐metal interactions were delineated by grazing incidence infrared spectroscopy on mirror surfaces. Vast differences were observed between unreactive gold, titanium, chromium, and aliminum, and reactive copper and silver, where copper and silver form amic acid salts. Other polymer‐metal interactions were observed with unreactive metals where aromatic ether rings appear to align on the metal surface. Further, reactive meta and para diacid carboxylates appear to assume different surface conformations. Heating the surface‐bound metal salts destroys the polymer interface, but nonsalt film, formed from amic acid or amic ester, appears to establish near planar aromatic ether conformations on the metal surfaces, with resultant orthogonal imide links.
Fractionation and characterization of a 1‐butene linear low density polyethylene
Authors: Springer H. , Hengse A. , Hinrichsen G.
Published: April 2003

A commercial 1‐butene LLDPE, Stamylex 1048, is cross fractionated by dynamic direct extraction and subsequent solution crystallization. The fractions are characterized by determining molecular masses Mn, Mn, and Mw and the comonomer content. DTA measurements are performed on unannealed and annealed samples of the fractions. The temperatures and specific heats of crystallization and fusion can be interpreted by reflecting the influence of molecular weight and comonomer content. The presented results are compared to data of 1‐butene LLDPE published in the recent literature.
Synthesis of polymeric chiral oxazoline and its applications on the asymmetric induction
Authors: Liu Jui‐Hsiang , Kuo Jue‐Cheng
Published: April 2003

A series of diastereoisomeric amino bicyclo [2,2,1] heptane derivatives was synthesized from (+)‐camphor. Further treatment of aminobornanols with triethyl orthopropionate afforded chiral oxazolines, which were found to be efficient for the asymmetric induction of carboxylic acids. Synthesis and polymerization of the new chiral oxazolinebornyl methacrylate derived from aminobornanols was carried out. Effects of temperature, solvents, and molar ratio of the reagent on the polymerization of the linear chiral polymers and the synthesis of the insoluble chiral crosslinked polymers were also discussed. Aminobornanols and chiral polymers with pendant aminobornanol moieties were found to be efficient for the asymmetric induction of chiral methylalkanoic acids. Recovery of the chiral reagents, the stereoselectivity of chiral oxazolines, and the parameters governing its successful implementation and the mechanistic aspects of the processes were also investigated.
Dielectric and dynamic mechanical behaviors of 1,2‐polybutadienes
Authors: Ni Shaoru , Yu Fusheng , Shen Lianfang , Qian Baogong
Published: April 2003

The dielectric relaxation behavior of 1,2‐polybutadienes is analyzed in terms of the experimental data and master curves. The dielectric measurement data were fitted to the empirical relaxation time distribution model of Havriliak and Negami over a frequency range from 100 to 1012 Hz. The constants of the WLF equation, C1 and C2, were evaluated with Tg at 100 kHz as a reference temperature for some samples, and the master curve of a sample was constructed. The dynamic mechanical measurements for a series of 1,2‐polybutadienes with different chain structure were performed over a temperature range from −150 to 50°C. A qualitative comparison of the dielectric and dynamic mechanical behaviors of 1,2‐polybutadienes has been made.
Polymerization of olefins through heterogeneous catalysis. VIII. Monomer sorption effects
Authors: Hutchinson R. A. , Ray W. H.
Published: April 2003

In solid catalyzed olefin polymerization, equilibrium sorption plays a key role in determining the local monomer concentration (s) in the semicrystalline polymer shell which surrounds the active sites of the catalyst surface. Modelling based on polymer solution thermodynamics indicates that crystallinity and reactor environment have a major effect on this local monomer concentration. The model is used to explain well known experimental trends seen in the literature, such as observed differences in gas phase and diluent slurry polymerization rates, and enhanced α‐olefin incorporation in gas phase copolymerization.
Thermodynamic models for swelling of heterogeneous networks
Authors: Harland Ronald S. , Klier John , Peppas Nikolaos A.
Published: April 2003

The equilibrium swelling behavior of heterogeneous systems consisting of a consisting of a continuous network phase and a dispersed lamellar, spherical, or cylindrical phase is described using a thermodynamic model. The case of swelling of both phases but to different extents is described. The equilibrium volume fractions of each phase as well as the stresses at equilibrium are predicted as functions of the polymer interaction parameter, X, the modulus, G, and the geometric character of the networks.
Transition metal chelates as accelerators for epoxy resin systems—studies with cobalt (III) acetylacetonate
Authors: Reddy P. V. , Thiagarajan R. , Ratra M. C. , Gowda N. M. Nanje
Published: April 2003

Cobalt(III)acetylacetonate serves as an accelerator for anhydride curable epoxy resin system and the rate of curing is found to increase with enhanced concentrations of the metal chelate. There is also an appreciable reduction in the cure gel time. Kinetic studies based on thermal analytical techniques reveal that the overall curing process follows first order kinetics. Based on the kinetic results a cure schedule has been proposed. It is also observed that the electrical, mechanical, and thermal properties of the cured epoxy system are not altered by the presence of the metal chelate at the concentration studied.
The role of extractives during vacuum pyrolysis of wood
Authors: Roy Christian , Pakdel Hooshang , Brouillard Dominique
Published: April 2003

Vacuum pyrolysis of wood, extractive‐free wood, holocellulose, and Avicel was conducted and their oil yields were compared. Formic and acetic acids and levoglucosan contents of all the oil products were determined. Molecular beam mass spectrometry analysis of wood and extractive‐free wood and their pyrolysis oils was performed. CO2and CO, the main pyrolysis gases, were measured for each pyrolysis experiment. The role of extractives and the modification in wood cellulosic structure, which occurred during wood extraction treatment process, were investigated. Extractives, lignin, and orientation of the cellulosic fibers all significantly influenced the production of pyrolysis oils and formic acid. Lignin and extractives exhibited an inhibiting effect for the production of acetic acid and levoglucosan, respectively. CO2and CO yields were affected by the presence of extractives and by the cellulosic fiber orientation.
Epoxy‐pretreated asbestos composites: Solution based versus interfacial polymerization pretreatment process
Authors: Papaspyrides C. D. , Duvis T.
Published: April 2003

Epoxy‐resin‐based composites filled with treated asbestos fibers were made. The asbestos, of chrysotile variety, was coated by impregnation in poly(hexamethylene adipamide) solution and the results of testing the tensile properties of the asbestos/polyamide/epoxy composite system are presented. The interest was focused on the influence of the asbestos content in the composite together with that of the polyamide content deposited on asbestos. No satisfactory reinforcing effect was found, especially when comparing with previous studies on coating the chrysotile by in situ interfacial polymerization. Nevertheless, a qualitative model was proposed to correlate the effect of the different phases contained in the composite with the experimental behavior encountered.
Theoretical estimations of diffusion coefficients
Authors: Huang Robert Y. M. , Rhim Ji‐Won
Published: April 2003

A model calculating the diffusion coefficients of liquids in polymeric membranes from the diffusion coefficients at zero concentration was developed. This model is based on Fujita's volume theory and considers crystallinity in the polymer and is tested by using available data in the literature, i.e., n‐hexane–polyethylene and benzene–polyethylene systems. The calculated diffusion coefficients were simulated by calculating the pure liquid permeabilities in a pervaporation system. When comparing the predicted pure liquid permeabilities with the experimental values, these calculated values were found to be in fairly good agreement.