bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal oxidative studies of poly(hexafluoropropene oxide) fluids
Authors: Paciorek K. J. L. , Kratzer R. H. , Kaufman J. , Nakahara J. H.
Published: April 2003

Elucidation of mechanisms operative in thermal oxidative degradation of hexafluoropropene oxide derived polyethers and the effect of metals on these processes are reported. Thermal oxidative instability of a commercial fluid, at moderate temperatures (550°F), was found to be due to the presence of ∼3% of thermooxidatively unstable chains believed to be hydrogen terminated; treatment at 650°F in oxygen volatilized these chains by unzipping. The resultant fluid was unaffected by oxygen at 650°F and by M‐50 and Ti(4Al, 4Mn) alloys at 600°F in oxidizing atmospheres. M‐50 alloy catalyzed the degradation of the hydrogen‐terminated chains below and at 600°F, but after completion of this process did not affect the remainder of the fluid at these temperatures. At 650°F a chain scission process promoted by the metals constituting the alloy, or their oxides or fluorides, came into play. Ti(4Al, 4Mn) alloy in the presence of CF3COF and COF2 species, formed via decomposition of the hydrogen‐terminated chains, degraded poly(hexafluoropropene oxide) fluids at 550°F by chain scissions.
Impact strength of thick‐interlayer composites
Authors: Peiffer Dennis G.
Published: April 2003

The impact strength of a thicker interlayer fiber filled composite material is evaluated as a function of both interlayer thickness and glass transition temperatures (Tg). The results confirm that for maximum strength, an optimum interlayer thickness is required. It is shown that this result is a function of the interlayer's Tg. Comparison with studies on other rubber reinforced systems are noted.
Interfacial properties of polyelectrolyte‐cellulose systems. IV. Electrokinetic properties of carboxymethylcellulose fibers with adsorbed multilayers of cationic polyelectrolyte
Authors: Onabe Fumihiko
Published: April 2003

Zeta potential measurements by the streaming current method were performed on carboxymethylcellulose (CMC) with and without irreversibly adsorbed multilayers of cationic polyelectrolyte. Factors affecting the electrokinetic properties such as the amount of adsorbed polymer, polymer molecular weights (Mn 50,000 and 200,000), ionic strength (10−5 ∼ 10−2M KCl), and pH of the streaming medium (KCl solutions) were examined. The negative zeta potential of CMC decreased to the point of monolayer formation and increased from that point to the saturated multilayer formation. The polarity of the zeta potential was negative throughout every adsorption stage. The negative zeta potential increase was attributed to: (a) binding of anions (Cl− and OH−) to the outermost layer of the multilayer from KCl solutions and (b) change in chemical potentials of counterions in a diffuse double layer due to expansion of the double layer in the presence of the adsorbed multilayer on CMC. The results suggest that the carboxyl groups under the monolayer are undetectable electrokinetically; however, the negative charge, due to unneutralized carboxyl groups under the monolayer, appears to cause further adsorption forming a saturated multilayer. When the effect of unneutralized carboxyls of CMC are shielded at higher levels of adsorption, the outermost layer of the multilayer becomes a potential‐determining layer.
Radiation‐induced polymerization of ethylene in pilot plant. III. Heavy‐phase recycling process
Authors: Takehisa Masaaki , Watanabe Hiromasa , Kurihara Hirondo , Yamaguchi Kouichi , Nakajima Hayato , Yagi Toshiaki , Watanabe Terutaka , Sugo Takanobu , Suwa Takeshi , Maruyama Shinsaku , Kodama Atsuro , Shimada Takeo , Maruyama Yoshio , Tohei Masamichi , Wada Takeshi , Machi Sueo
Published: April 2003

Radiation‐induced polymerization of ethylene using aqueous tert‐butyl alcohol as medium was carried out in a large‐scale pilot plant with a 50‐liter central source‐type reactor at a pressure of 105 to 395 kg/cm2, temperature of 30° to 80°C, mean dose rate of 4.5 × 104 to 1.9 × 105 rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.‐hr and 1.3 × 104 to 8.9 × 104, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine‐powder polyethylene were successfully carried out. In the central source‐type reactor, a dose rate of 1.9 × 105 rads/hr was obtained with a 60Co source of ca. 12 kCi.
Refractive index increments of polyethylene
Authors: Horská Jitka , Stejskal Jaroslav , Kratochvíl Pavel
Published: April 2003

The refractive index increments of linear and branched polyethylene were determined for several solvents and various wavelengths (403, 436, 546, and 633 nm), mainly at 135°C. Differences were observed between values for linear and branched samples. Data obtained in this investigation are compared with the reported ones.
Stabilization of poly(vinyl chloride). IV. Color changes on heating poly(vinyl chloride)–dye systems
Authors: Iida Takeo , Gotō Kunio
Published: April 2003

The stabilization of poly(vinyl chloride) (PVC) involving complementary colors has been previously reported. Obliterating polyene color with various dyes containing complementary colors with the polyene color is studied on the basis of colorimetry. The changes in the color of heated PVC containing Thren Blue IRN, Ceres Blue GN, Oplas Violet 730, Macro‐Lex Violet 3R, Macro‐Lex Green 5B, or Macro‐Lex Red 5B were investigated using a differential colorimeter. When the PVCs containing various dyes were heated, the discoloration from the color of each dye to the color mixture of each dye and polyene color was observed with increased heating times for all systems. In particular, an achromatic color has been observed, during the heat treatments, in PVC containing blue dyes such as Thren Blue IRN or Ceres Blue GN, which set up complementary color relationship with the polyene color. Thus the color of polyenes, which appears with advancing dehydrochlorination of PVC, is masked by the blue dyes. It is also apparent that the obliteration of polyene color does not depend on the chemical influences of the dyes added, but by color mixing of polyenes and the dyes. Cool‐color dyes markedly slow down the appearance of polyene colors.
Dielectric behavior of the constituents of the natural resin shellac
Authors: Goswami Dipendra Nath
Published: April 2003

The dielectric relaxation data of the constituents of natural resin shellac have been analyzed by the Cole–Cole method at temperatures between 10° and 90°C in the frequency range of 50 Hz to 500 kHz. The functional groups present in hard and soft lac appeared to be responsible for the dielectric properties exhibited by shellac below and above its glass transition and melting temperature, respectively. A combination of 70% hard lac and 30% soft lac was found to exhibit the dielectric properties of shellac satisfactorily.
Water permeation of polymer films. II. Dual‐mode absorption in teflon FEP
Authors: Sacher E. , Susko J. R.
Published: April 2003

DuPont Teflon FEP has been shown to permeate water vapor through a dual‐mode process: adsorption followed by permeation. A model is proposed for this process based on the interactions of condensible gas molecules with themselves and with the polymer surface. This model appears to have general applicability.
Experimental study of the relationship of processing to the morphology in blends of SBR and cis‐polybutadiene with carbon black
Authors: Lee Biing‐Lin , Singleton Chloe
Published: April 2003

The morphology of carbon‐black‐loaded styrene–butadiene rubber (SBR)/cis‐1,4‐polybutadiene (BR) blends is characterized as a function of mixing energy input. The blends consist of an 80:20 weight ratio of SBR and BR with the incorporation of 20 phr carbon black via three different schemes. These schemes are: (1) free mixing of the three components, (2) mixing of BR–black masterbatch with SBR, and (3) mixing of SBR–black masterbatch with BR. Differential scanning calorimetry (DSC) and electron microscopy (EM) results indicate that the domain morphology is strongly affected by the manner in which the carbon black is introduced into these blends. Some of the features of the blends are as follows: (1) BR, which is the minor rubber component, is always the dispersed phase, and its domain size decreases with increasing energy input during mixing. (2) In the black–rubber masterbatch mixing, the black always stays in the original rubber phase throughout the mixing process. No significant migration of carbon black from one rubber phase to the other is observed. (3) In the free mixing process, the carbon black agglomerates initially line up along the SBR–BR interfaces, and later disperse throughout the SBR matrix with increased mixing. However, the DSC results suggest that the amount of carbon‐black‐free BR is decreasing with increased mixing. This would occur if there is created a carbon‐black‐loaded SBR–BR diffuse interphase. A model is developed to interpret these findings.
Preparation of higher aliphatic acid esters of wood in an N2O4–DMF cellulose solvent medium
Authors: Shiraishi Nobuo , Matsunaga Tadayo , Yokota Tokuo , Hayashi Yoshiyuki
Published: April 2003

Esterification of wood meal with a series of aliphatic acid anhydrides and acid chlorides in a nonaqueous cellulose solvent, an N2O4–DMF solvent, has been studied. The N2O4–DMF–pyridine solution used as the reaction medium plays a role in destroying the molecular order of the cellulose within the wood, enabling the cellulose to be uniformly substituted by acyl groups along its chain. These uniformly distributed blocking groups result in the permanent decrystallization of the wood. The acyl blocking groups are best achieved by esterification using acid chlorides in the nonaqueous solvent. Acid chlorides, from caproyl to stearoyl chloride, were found to be much more effective as acylating agents than acid anhydrides, from propionic to caproic anhydride. Although no difference in reactivity can be recognized among the acid chlorides, the reactivity decreases with increase in the number of carbon atoms in the acyl group among the acid anhydrides.
Thermal softening and melting of esterified wood prepared in an N2O4–DMF cellulose solvent medium
Authors: Shiraishi Nobuo , Matsunaga Tadayo , Yokota Tokuo
Published: April 2003

The thermal softening and melting of a series of esterified wood samples, whose preparation has previously been described,4 have been studied by measuring the deformation of the samples under constant load at a constant heating rate. The introduction of acyl groups into wood including part of the original crystal structure in cellulose makes the modified wood meal conspicuously thermoplastic. While untreated dry wood shows a thermal softening point (Ts) of ca. 260°C, esterified wood meal samples with acyl groups larger than caproyl have a Ts of around 100°C or less, and appeared to melt over the temperature range of 220° to 250°C. In this case, the melting occurs even with wood meal samples esterified with appropriate acid chlorides in an N2O4–DMF–pyridine medium only for 30 min at room temperature. This might be the first finding that wood meal is converted, as a whole, into a thermoplastic material which can melt without any accompanying detectable degradation.
Effects of moisture and stoichiometry on the dynamic mechanical properties of a high‐performance structural epoxy
Authors: Keenan Joseph D. , Seferis James C. , Quinlivan John T.
Published: April 2003

Dynamic mechanical measurements have been made on a 4,4′‐diaminodiphenyl sulfone‐cured tetraglycidyl 4,4′‐diaminodiphenylmethane epoxy (TGDDM‐DDS). There are basically three transitions on the mechanical spectra that have been identified, and the effects of moisture uptake and amount of DDS on these transitions were examined. The dynamic mechanical behavior of the same epoxy with 60% carbon fiber loading was also studied, providing further elucidation on the nature of the transitions observed with this system.
Effect of postdrawing on the permeability of gases in blown polyethylene film
Authors: Paulos James P. , Thomas Edwin L.
Published: April 2003

The effect of orientation on the structure and transport properties of high‐density polyethylene film has been studied. Microstructure was characterized using small‐angle light scattering, birefringence, and wide‐angle x‐ray scattering. Water vapor and oxygen transmission rates were determined as a function of film draw ratio. The object of the present work is to correlate the effects of postprocessing conditions on the transport properties and morphology of linear polyethylene. High‐density spherulitic polyethylene films were produced by blown film extrusion and subsequently oriented by longitudinal stretching in a postoperation. Various degrees of orientation were imparted to the films, with percent crystallinity, sample orientation and transport properties measured as a function of draw ratio. For the postoriented films, results indicate there was no significant change in percent crystallinity with increasing draw ratio although water vapor and oxygen permeability decreased substantially. This is attributed to the increased orientation of the crystalline and amorphous regions and rod‐like and microfibril structure formation brought about by the drawing process. Lower processing temperatures result in increased orientation which improves the vapor barrier properties.
Surface modification of polyethylene by radiation‐induced grafting for adhesive bonding. IV Improvement in wet peel strength
Authors: Yamakawa Shinzo , Yamamoto Fumio
Published: April 2003

Adhesive joints of hydrolyzed methyl acrylate grafts, bonded with epoxy adhesives, yield extremely high peel strength (adherend failure) in dry conditions. However, when the joints are exposed to humid environments, the peel strenght rapidly decreases with exposure time and then reaches a constant value (wet peel strength). Since the locus of failure changes from the adherend to the homopolymer layer with decreasing peel strength, the decrease is due to a decrease in mechanical strength of the homopolymer layer itself, which results from its swelling by water absorption. Many attempts to reduce the swelling of the homopolymer layer or to strengthen the swollen homopolymer layer were unsuccessful except (1) priming with epoxy solutions consisting of a base epoxy resin and organic solvents which can dissolve not only epoxy resins but also hydrolyzed poly(methyl acrylate) and (2) partial etching of the homopolymer layer by photo‐oxidative degradation. All the results on the improvement in wet peel strength can be explained in terms of the penetration of epoxy resins into the homopolymer layer and subsequent curing of the penetrated epoxy resin.
Grafting vinyl monomers onto wool fibers. V. Graft copolymerization of methyl methacrylate onto wool using peroxydiphosphate as initiator
Authors: Nayak Padma L. , Lenka Subasini , Mishra Munmaya K.
Published: April 2003

Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using potassium peroxydiphosphate as initiator. The rate of grafting was determined by varying monomer, peroxydiphosphate ion, temperature, solvent, and nature of wool. The graft yield increases with increase in monomer concentration. The graft yield increases significantly by increasing peroxydiphosphate ion up to 80 × 10−4mole/l.; with further increase of peroxydiphosphate ion the graft yield decreases. The rate of grafting increases with increase in temperature. The effect of acid‐and water‐soluble solvents on the rate of grafting was investigated and a suitable rate expression has been derived.
The initiation of in situ polymerization of vinyl monomers in polyester by glow discharge
Authors: Moshonov Aharon , Avny Yair
Published: April 2003

Glow discharge initiation of in situ polymerization of acrylic acid and other vinyl monomers incorporated in PET films was investigatigated. The influence of glow discharge conditions such as the gas used, plasma power, discharge current, and plasma treatment time on polymerization yield was determined. Though glow discharge effects are limited to the film surface, in situ polymerization of the vinyl monomers took place and the vinyl polymer could be found all through the film cross section. At short plasma treatment time only surface modification took place, while at longer treatment time bulk modification occurred, too. Good polymerization yields were obtained. Gel effect behavior was observed. Mechanical properties of the modified PET film were not changed, while the contact angle with water improved when polar vinyl monomers were used.
The formation of volatile pyrolyzates form poly(vinyl chloride)
Authors: Lattimer Robert P. , Kroenke William J.
Published: April 2003

The formation of volatile pyrolyzates in poly(vinyl chloride) has been studied by pyrolysis–gas chromatography–mass spectroscopy. Isotopic distributions of pyrolyzates from experiments with perdeutero‐PVC show that pure conjugated aromatic pyrolyzates (e.g., benzene, styrene, naphalene, biphenyl, anthracene) are formed mostly via intramolecular cyclization. Mixed aromatic‐alphatic pyrolyzates (e.g., toluene, indene, methylnaphthalene) are formed at least partially via intermolecular (crosslinking and/or hydrogen transfer) mechanisms. Direct scission of the PVC chain to form chlorine‐containing pyrolyzates is a very minor degradation pathway. Most chlorine‐containing “pyrolyzates” from PVC are due to secondary reactions of HCl with the environment or with non‐PVC compounding ingredients. No evidence was found for oxygen‐containing pyrolyzates derived from the PVC backbone under conditions of nonflaming pyrolysis in air.
Cocrystallization and polymer miscibility
Authors: Starkweather Howard W.
Published: April 2003

Low‐density polyethylene was blended in various proportions with an ethylene/propylene/1,4‐hexadiene copolymer having an ethylene/propylene mole ratio of 4.5 and a low level of crystallinity. The DSC melting peak of polyethylene was decreased, the unit cell was expanded, and the spherulitic development was disturbed. The temperature of a dynamic mechanical loss peak varied smoothly with composition between the Tg of the copolymer and the β‐relaxation of the polyethylene, but the glass temperature of the copolymer measured by DSC was unchanged. These effects were all diminished when the ethylene/propylene ratio of the copolymer was reduced. Blends with highdensity polyethylene showed little depression of the melting point or change in crystal structure and much less effect on the dynamic mechanical behavior. However, the behavior of copolymers of ethylene with low levels of vinyl acetate or methyl methacrylate was similar to that of low‐density polyethylene. Therefore, the ability to cocrystallize is an important factor for limiting the tendency of nonpolar polymers to separate, thereby facilitating the preparation of blends with desirable combinations of properties.
New approach to aqueous gel permeation chromatography of nonderivatized cellulose
Authors: Bao Yen T. , Bose Arindam , Ladisch Michael R. , Tsao George T.
Published: April 2003

A novel approach to the gel permeation chromatography (GPC) of nonderivatized cellulose is reported using Sepharose CL‐6B as the column packing material, 0.5N NaOH as the eluent, and cadoxen as the cellulose solvent. The traditional approach to GPC of cellulose has been to convert the cellulose to its nitrate thereby making it soluble in the solvent tetrahydrofuran. The circumvention of the need to derivatize the cellulose in the new system results in considerable saving of time. The new system gives good fractionation for cellulose. It also provides excellent separation of polystyrene sulfonate and dextran standards thereby making the system amenable to calibration. The effect of the particle size distribution of the column packing material on the efficiency of separation is discussed. Potential applications for this new method include studies on both acidic and enzymatic hydrolysis as well as fine structure of cellulose, starch, and other polymers capable of forming stable alkaline solutions.
Phosphorylation of cellulose: Effect of the reactivity of the starting polymer on the properties of the phosphorylated product
Authors: Zeronian S. H. , Adams S. , Alger K. , Lipska A. E.
Published: April 2003

When cellulose is phosphorylated with phosphorus oxychloride, the reactivity of the cellulose, as well as reaction time and temperature, influences the relative amounts of phosphorylated and chlorinated product formed. The swelling ability of the phosphorylated product is affected by the pretreatment received by the cellulose (i.e., prior to phosphorylation) to change its reactivity. The thermal decomposition process of phosphorylated cellulose, as indicated by differential thermal analysis, is affected also by the pretreatment received by the cellulose.
Microphase separation and properties of urethane elastomers
Authors: Nierzwicki W. , Wysocka E.
Published: April 2003

Several polyurethanes were prepared from poly(ethylene adipate)glycol, 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol, or 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane. Thermomechanical curves were determined for all investigated systems, and the glass transitions found thereof formed the basis of subsequent analysis. The analysis showed that the investigated systems belonged to those polyurethanes that can undergo microphase separation. It was also shown that the separation in the diamine‐extended elastomers was less sensitive to changes in chemical composition than in the diol‐extended systems. The diamine‐based polyurethanes were also closer to the ideal separation than the diol‐extended elastomers. Examinations of elastomers of varying amount of chemical crosslinking revealed a joint action of the crosslinking and microphase separation in determining mechanical properties of the systems. Together with swelling measurements, the examinations showed that optimum mechanical properties were obtained while keeping a very careful balance between these two factors.
Effects of fiber length on the tensile strength of epoxy/glass fiber and polyester/glass fiber composites
Authors: Miwa Minoru , Ohsawa Tadashi , Tahara Kenji
Published: April 2003

In discontinuous fiber‐reinforced composites, the shear strength at the fiber–matrix interface plays an important role in determining the reinforcing effect. In this paper, a method was devised to accurately determine this shear strength, taking the strength distribution of glass fiber into consideration. Calculated strength values based on the shear strenght obtained by the method were in better agreement with the experimental observations than those calculated by employing the shear strength obtained on the assumption that the fiber strength was uniform. The tensile strength of composites increases with increasing aspect ratio of the reinforcing fibers. This trend is almost the same regardless of the kind of matrix, the nature of interfacial treatment, and the environmental temperature. When composites are reinforced with random‐planar orientation of short glass fibers of 1.5 times the mean critical fiber length, the tensile strength of composite reaches about 90% of the theoretical strength of composites reinforced with continuous glass fiber. Reinforcing with glass fibers 5 times the critical length, the tensile strength reaches about 97% of theoretical. However, from a practical point of view, it is adequate to reinforce with short fibers of 1.5–2.0 times the mean critical fiber lenght.
On shift and resolution of relaxation maxima in two‐phase polymeric systems
Authors: Lipatov Yu. S. , Rosovitsky V. F. , Babich B. V. , Kvitka N. A.
Published: April 2003

The results of calculations of viscoelastic properties of filled polymers assuming “boundary layer” and the polymer matrix having their own and different glass transition temperatures are presented. The calculations have been made on the basis of the models in series and parallel coupling of viscoelastic bodies as well as Takayanagi's model. Using specified temperature, dependences of viscoelastic properties of the polymer and the “boundary layer” temperature dependences of the real part G′ of the complex shear modulus and tan δ for such a two‐phase system with varied differences in glass transition temperatures and concentration of the components were derived. The degree of maxima shift observed experimentally for the filled polymer owing to variation of properties of the “boundary layer” (its concentration and glass transition temperature) were evaluated. Conditions for the appearance of two maxima tan δ for the respective glass transtion temperatures of the polymer and “boundary layer” on the curves tan δ = f(T) were determined.
Morphology and fracture properties of pure and reinforced aluminum‐epoxy adhesive joints
Authors: Mijović Jovan
Published: April 2003

Several types of nonreinforced and reinforced epoxy‐aluminum adhesive joints were prepared and investigated. High modulus carbon fibers and hollow glass microspheres were used as reinforcement. The amount of curing agent, postcure time, adhesive thickness, and type and amount of reinforcement were varied throughout this study, and their effect on fracture energy was determined. Unstable crack propagation through the adhesive layer was observed. Nodular morphology typified all fracture surfaces of nonreinforced adhesive joints, indicating the existence of an inhomogeneous thermosetting network. Electron microscopic evidence was obtained for plastic flow in crack initiation and crack arrest regions. The nature of this plastic flow was discussed in terms of changes in the resin morphology.
Stabilization of poly(vinyl chloride). VI. Synergetic effects of aminopolycarboxylates or nitrogen‐containing agents with zinc stearate/calcium stearate soap
Authors: Iida Takeo , Gotō Kunio
Published: April 2003

Discoloration such as zinc burning was observed in aged poly(vinyl chloride) (PVC) compounded with synergetic soaps. This discoloration was caused by excessive formation of cool color‐producing π complexes formed between double bonds in polyene chain and zinc chloride or cadmium chloride produced from the corresponding metal soap. The appearance of excessive color of the π complexes was reduced by adding some masking agents into PVC admixed with synergetic soaps. In the present study differences in masking effects results by adding solid or an aqueous solution of aminopoly‐carboxylates such as glycine, ethylenediaminetetraacetates, and nitrilotriacetates to PVC stabilized with zinc stearate/calcium stearate synergetic soap. The mechanism of synergetic effect between nitrogen‐containing agents and synergetic soaps upon the stabilization of PVC is also investigated by colorimetry. The aqueous solution of aminopolycarboxylates exhibits a greater masking effect than the solid. The masking effect of aminopolycarboxylates depends on the ease with which they are fnely dispersed into PVC. Colorimetry indicated that the masking effect of aminopolycarboxylates and other nitrogen‐containing agents depends on forming the colorless complex compound with the excessive cool color‐producing metal chlorides.
Structure and properties of acrylonitrile‐[(2‐methacryloyloxy)alkoxy]trimethyl silane copolymers
Authors: Bajaj P. , Gupta D. C. , Gupta A. K.
Published: April 2003

Dielectric, x‐ray diffraction, density, thermomechanical, and thermogravimetric studies on polyacrylonitrile (PAN), poly[acrylonitrile‐(2 methacryloyloxy)ethoxytrimethylsilane] [poly(AN‐2MAETMS)], and poly[acrylonitrile‐(2 methacryloyloxy)propoxytrimethylsilene] [poly(AN‐2MAPTMS)] copolymers have been carried out for investigating their structure. The glass transition temperature as indicated from the dielectric and thermomechanical analysis data are lower for the copolymers as compared to PAN. Crystallinity is influenced by the introduction of the silylated acrylic comonomer units but the crystalline lattice remains similar to that of PAN. The changes obseved in the various properties of these coplymers clearly suggest a more closely packed structure of poly(AN‐2MAETMS) than poly(AN‐2MAPTMS), and the uninterrupted PAN sequences are longer in the former. Thermal stability of copolymers has also been investigated.
Investigation on the synthesis and characterization of rare earth metal‐containing polymers. II. Fluorescence properties of Eu3+–polymer complexes containing β‐diketone ligand
Authors: Ueba Y. , Banks E. , Okamoto Y.
Published: April 2003

Europium(III) chelates of dibenzoylmethane (DBM) (1) and β‐diketone‐containing polymers, i.e., poly(p‐benzoylacetylstyrene) (2) and poly(aryl β‐diketone) (3), were prepared. In the polymer 2 the β‐diketone moiety is attached to the phenyl ring, and for polymer 3 the β‐diketone group is incorporated in the linear chain. The chelate structures were confirmed by measuring IR spectra, TGA, and DTA. The fluorescence emission intensity was measured on fine powder samples. For the composite samples of Eu(DBM)4 in polystyrene, the fluorescence intensity was found to increase linearly with increasing Eu content. However, for Eu coordination polymers, the intensity reached a maximum at Eu3+ content as small as 1 wt % and remained constant on further increasing the Eu3+ content. When the fluorescence intensities of Eu complexes were compared under the same conditions, namely, 1 wt % Eu, at which Eu–2 and Eu–3 show nearly maximum intensity, the order was found to be Eu–1 > Eu–2 > Eu–3. These phenomena were accounted for by the differences in the coordination number of the Eu complexes.
Kinetics and conversion monitoring in a RIM themoplastic polyurethane system
Authors: Steinle Edmund C. , Critchfield Frank E. , Castro José M. , Macosko Christopher W.
Published: April 2003

Kinetic data are reported for the fast polymerization of a thermoplastic polyurethane under conditions similar to that of commercial reaction injection molding (RIM). The components were a 2000 molecular weight polyester polyol, butanediol and 4,4′‐diphenylmethane diisocyanate. Three catalysts–dibutyltin dilaurate, phenyl mercuric propionate, and triethylenediamine–as well as uncatalyzed formulations were studied. Kinetic parameters were obtained by numerically fitting adiabatic temperature rise data with both second‐order and hyperbolic models. The hyperbolic model gave consistently better fits and is supported by mechanistic studies in the literature. Activation energies compare well to literature values. The uncatalyzed rate was found to be significant. The kinetic parameters obtained by this method are useful measures of catalyst performance in the RIM systems. Moreover, the models provide a conveient way to predict the extent of reaction during the production of parts by the RIM process. The shape of the reaction pathway (extent of reaction time) may be important in the development of physical properties of polymers produced by the RIM process. Physical properties for these samples compare favorably to those for a conventionally produced (batch) polyurethane of the same formulation.
Flammability resistance synergism in BPA polycarbonate–silicone block polymers
Authors: Kambour R. P.
Published: April 2003

The synergism in limiting oxygen index found in BPA carbonate–dimethylsiloxane block polymers (BPAC/DMS) is correlated with a rise in yield of pyrolytic char and an improvement in char oxidation resistance. These changes in turn are related to a peaking of fractional silicon retention in the char at a resin composition of 50 mole % DMS. This behavior, the fine dispersion of silicon in the char, and analyses of the pyrolysates suggest that an important feature of char formation in the block polymers is a polycondensation reaction between pyrolysis products from the two blocks. In addition to the role of chars in withholding fuel from the flame, they are thought to function effectively as thermal insulators.
Gas permeability of copolypeptide membranes composed of γ‐methyl L‐glutamate and γ‐benzyl L‐glutamate
Authors: Minoura Norihiko , Fujiwara Yukihiko , Nakagawa Tsutomu
Published: April 2003

Membranes of copoly(γ‐methyl L‐glutamate, γ‐benzyl L‐glutamate) (PMBLG) as well as the related homopolymer membranes were prepared, and permeabilities of oxygen, nitrogen, argon, and carbon dioxide were measured in the 0–70°C temperature range. The values of permeability coefficients and solubility coefficients of the copolymers were smaller than those of permeability coefficients and solubility coefficients of the two homopolymers for every gas studied. The diffusion coefficients of the gases showed a minimum at around 25 mole % benzyl glutamate. The temperature at a maximum of tan δ spectra for the membranes showed a maximum at around 25 mole % benzyl glutamate. The Arrhenius plots of diffusion coefficients and solubility coefficients for PMBLG, which contained 50 and 71 mole % benzyl glutamate, showed a break at about 50 and 40°C, respectively. This permeation behavior is explained by assuming a unique interaction between methyl glutamate and benzyl glutamate side chains.
Effects of ionizing radiation on perfluorosulfonic acid ion‐exchange polymer
Authors: Balko E. N. , Chaklos J. T.
Published: April 2003

The effects of β and γ radiation on the Nafion perfluorinated ion‐exchange polymer have been examined and the radiolysis products have been identified. The polymer degrades by simple chain scission, and the rate of degradation is not affected by the state of polymer hydration of the nature of the ion which occupies an exchange site.
Delignification and degelation: Analogy in chemical kinetics
Authors: Yan Johnson F. , Johnson Donald C.
Published: April 2003

Structurally and kinetically, chemical pulping can be treated as a degelation process. Kinetics derived from the empirical power law is rejected on the grounds that lignin is a polymer. Using an extended version of the Flory–Stockmayer theory and a kinetic expression derived by Whittle, the delignification kinetics is expressed in terms of opposing unimolecular–bimolecular reactions. The quantity replacing lignin concentration is the “extent of reaction” defined in the theory. Parameters used in this reaction are estimated, and the time dependence of the undissolved lignin fraction can be calculated. The calculated delignification curve is shown to be in good agreement with experimental results.
Copolymerization of styrene with acrylamide in an emulsifier‐free aqueous medium
Authors: Ohtsuka Yasuji , Kawaguchi Haruma , Sugi Yoshishige
Published: April 2003

Copolymerization of styrene with acrylamide was carried out in an emulsifier‐free aqueous medium. The resulting latex contained an appreciable amount of acrylamide‐rich copolymer in the serum. The copolymerization course was divided into three stages on the basis of the main reaction locus. At first, acrylamide polymerized in preference to styrene in the aqueous phase. Water‐soluble growing radicals lost hydrophilicity rapidly and nucleated the particles. After particle formation, styrene polymerized exclusively in the particles until styrene droplets disappeared. The decrease in the concentration of residual styrene monomer caused growing radicals to keep the hydrophilicity for a long time, and polymerization of acrylamide was accelerated in the aqueous phase. Polymerizations at higher temperature and lower pH resulted in prolongation of the first stage of the polymerization, that is, preferential polymerization of acrylamide in the aqueous phase. An increase in the acrylamide fraction in monomer feed caused some decreases in the particle size and its uniformity.
Model networks of end‐linked polydimethylsiloxane chains. XII. Dependence of ultimate properties on dangling‐chain irregularities
Authors: Andrady A. L. , Llorente M. A. , Sharaf M. A. , Rahalkar R. R. , Mark J. E. , Sullivan J. L. , Yu C. U. , Falender J. R.
Published: April 2003

Elastomeric networks were prepared by end‐linking vinyl‐terminated polydimethylsiloxane (PDMS) chains having number‐average molecular weights of 11.3 × 103 g mol−1. The tetra‐functional end‐linking agent, Si[OSi(CH3)2H]4, was used in varying amounts smaller than that corresponding to a stoichiometric balance between its active hydrogen atoms and the chain vinyl groups. The number of dangling‐chain irregularities thus introduced into the networks was directly determined by iodometric titration for unreacted vinyl groups. The (unfilled) PDMS networks thus obtained were studied in elongation to their rupture points at 25°C (a temperature sufficiently high to prevent complications from strain‐induced crystallization), and in swelling equilibrium in benzene at room temperature. Small to moderately large proportions of dangling chains were found to have less of an effect on the elongation modulus than might be expected, and similarly a relatively small effect on the degree of equilibrium swelling. Most importantly, comparisons of constant values of the high deformation modulus show that dangling‐chain irregularities decrease both the maximum extensibility of a network and its ultimate strength.
Dicyandiamide analysis and solubility in epoxy resins
Authors: Hagnauer Gary L. , Dunn David A.
Published: April 2003

A simple procedure is described for the rapid, quantitative analysis of dicyandiamide in epoxy resins and epoxy resin prepregs. High performance liquid chromatography is used to analyze for dicyandiamide and to investigate the solubility behavior of dicyandiamide and 3‐(p‐chlorophenyl)‐1,1‐dimethylurea (Monuron) in liquid epoxy resins. Solubility expressions and differential heats of solution are determined. The formation of soluble amine‐epoxy reaction products and epoxy resin additives such as Monuron are found to enhance the solubility of dicyandiamide.
Wettability of glow discharge polymers
Authors: Sharma Ashok K. , Millich Frank , Hellmuth Eckhard W.
Published: April 2003

Treatment of good adhering glow discharge polymerized propylene (GDPP) coatings with reactive gas plasma from oxygen, nitrogen, or water (produced in a tubular reactor operation at 27.1 MHz) results in surfaces characterized by more hydrophilic interactions. Zisman's plots indicate a change in surface energy after such treatment. Transmission electron microscopy depicts that the pronounced improvement in wettability of GDPP polymer after oxygen plasma treatment in part results from the high surface development in the polymer. However, the effect is not permanent. The wettability of plasma‐treated polymer diminishes with time and reaches a limiting value in 2–3 months indicating structural rearrangements at the polymer surface. Argon, carbon monoxide, or bromotrichloromethane plasma does not change the polymer surface wettability significantly. In contrast to the O2 plasma‐treated GDPP polymer, a glow discharged polymer synthesized from ϵ‐caprolactam maintains its inherent hydrophilicily over an extended period of time.
Shrinkage and internal stress during curing of epoxide resins
Authors: Shimbo M. , Ochi M. , Shigeta Y.
Published: April 2003

The shrinkage and internal stress of bisphenol‐type epoxide resins cured with aliphatic α,ω‐diamines, H2N(CH2)m′NH2(m′ = 2, 4, 6, and 12), were investigated by measuring the change of density and the strain of the steel ring embedded in the cured resins. Internal stress was found to be induced by the shrinkage occurring in the cooling process from the glass transition temperature (Tg) to room temperature. Shrinkage and internal stress increased with increase in the concentration of network chains and Tg of the cured systems, and then with a decrease in m′ of the curing agents. It appears that the reductions in the concentration of network chains and Tg were necessary to reduce the shrinkage and internal stress caused by the curing.
Thermal diffusivity and conductivity of crystalline polymers
Authors: Choy C. L. , Ong E. L. , Chen F. C.
Published: April 2003

The thermal diffusivity and conductivity of the isotropic and drawn samples of five semicrystalline polymers—nylon 6, poly(ethylene terephthalate), poly(butylene terephthalate), polybutene‐1, and poly(4‐methylpentene‐1)—were measured by the flash method over the temperature range 100–350 K. The temperature dependence of the thermal diffusivity was found to follow a simple phenomenological pattern, while a more detailed understanding of the temperature dependence and the effect of orientation on thermal conductivity was obtained by using the modified Maxwell model.
Studies on the light‐focusing plastic rod. IX. Chemical composition of the copolymer rod‐diethylene glycol bis(allyl carbonate) with 2,2,3,3‐tetrafluoropropyl methacrylate
Authors: Ohtsuka Yasuji , Terao Yukiko
Published: April 2003

For the preparation of the light‐focusing plastic rod (LFR) a gel rod of partially polymerized diethylene glycol bis(allyl carbonate) (CR‐39) was immersed in 2,2,3,3‐tetrafluoropropyl methacrylate (4FMA) followed by heat treatment under nitrogen. Variations in the chemical composition in this process indicated the following mode of copolymerization: copolymerization of 4FMA with the allylic group in the gel rod occurs to some extent in the immersion process, but a significant amount of either 4FMA or CR‐39 remains in the rod. Under heat treatment, these monomers copolymerize to a CR‐39–4FMA network copolymer, the preferential component of the LFR. Excellent imaging of the representative LFR is also demonstrated.
The influence of filler particles and polymer structure on the mobility of polymer molecules
Authors: Howard Gordon J. , Shanks Robert A.
Published: April 2003

The presence of carbon filler has been shown to cause a change in the glass transition temperature of polymers. For poly(vinyl chloride) and two of its copolymers with 10 and 15% vinyl acetate an increase in Tg was observed when Graphon C Carbon was added. The increase was greater when the proportion of vinyl acetate was greater. Polar vinyl acetate units allow stronger adsorption of polymer onto the carbon. Brittle polymers such as polystyrene and poly(methyl methacrylate) showed scattered Tg's when filled with carbon. The changes were not a function of concentration. It is postulated that the thermal stress of these polymers is increased in the presence of filler.
Poly(n‐butyl acrylate)/polystyrene interpenetrating polymer networks and related materials. III. Effect of grafting level and molecular weight in semi‐2 IPNs
Authors: Yeo J. K. , Sperling L. H. , Thomas D. A.
Published: April 2003

A series of poly(n‐butyl acrylate)/polystyrene IPNs and semi‐1 IPNs with deliberately controlled graft levels were synthesized via a urethane chemical coupling method. Also prepared were a series of semi‐2 IPNs with the molecular weight of polymer II as the variable. The more highly grafted IPNs displayed poorly defined morphologies in which the domain structures were irregular and phase domain boundaries were characterized by fibrillar and interphase regions. A single glass transition peak was another feature of the more highly grafted IPNs. Polymer network II formed in the presence of linear polymer I results in morphologies dependent on the molecular weight of linear polymers. In the semi‐2 IPNs, polymer I molecular weights below Mv = 20,000 caused polymer I to behave like a plasticizer or a diluent. The domain sizes of semi‐2 IPNs agree with theoretical predictions developed by the present authors.
Molecular motion of small molecules in cellulose gels studied by NMR
Authors: Nyström B. , Moseley M. E. , Brown W. , Roots J.
Published: April 2003

Measurements of relaxation times, T1 and T2, and self‐diffusion coefficients, D, for small molecules, viz., H2O, dioxane and t‐butanol, in the gel system cellulose/H2O are reported and compared with those for H2O in a polyacrylamide gel of the same polymer content. The temperature dependence of T1 and D can for all the penetrants be represented by Arrhenius type relations which merely are parallel shifts by the same amount, towards smaller values, of those obtained without polymer. The T2 values for H2O in both gels pass through a shallow minimum over the considered temperature interval (14°−44°C). Furthermore, relaxation times T1 of D2O in the gel system cellulose/D2O are reported; in a plot of ln T1 vs. 1/T, a plateau region is observed at higher temperatures.
Thermo‐oxidative degradation of low‐density polyethylene close to industrial processing conditions
Authors: Hoff A. , Jacobsson S.
Published: April 2003

Thermo‐oxidative degradation of low density polyetylene (LDPE) at a low degree of volatilization (about 4%) at 264–289°C was studied. Gas chromatography—mass spectrometric analysis was used to separate and identify the products of LDPE decomposition. Altogether 44 compounds representing hydrocarbons, alcohols, aldehydes, ketones, acids, cyclic ethers, cyclic ethers, cyclic esters, and hydroxycarboxylic acids were identified. Sixteen oxygen‐containing products were quantified. Among the components identified, the fatty acids and aldehydes predominated. The most abundant product was formic acid. The mechanism of formation of the degradation products is discussed.
The initial and terminating stage of glow discharge polymerization investigated by thickness monitor
Authors: Inagaki N. , Yasuda H.
Published: April 2003

An attempt to discuss the initial stage and terminating stage of glow discharge polymerization was made by selecting the monomer system of styrene and acetylene, which differ in their condensibility, and a certain polymerization procedure. Results indicate the important aspects of the initial and terminating stages of glow discharge polymerization. These aspects may not play a significant role in the study of bulk properties of plasma‐polymerized polymers or in the study of polymer deposition rate. However, the initial stage effect might influence the adhesion of the polymer. The terminating stage effect might influence the surface characteristics of glow discharge‐polymerized polymers. These effects are particularly important in a batch polymerization system, where the beginning and the end of process cannot be rigorously controlled with respect to the timing and sequence of the beginning and the end of monomer flow and of electric discharge. This study points to the importance of these aspects for proper utilization of glow discharge polymerization as a thin film process.
Effect of drawing on creep fracture of polypropylene fibers
Authors: Takaku Akira
Published: April 2003

The ultimate properties of polypropylene fibers, prepared by drawing the same undrawn fibers to different draw ratios, were determined by the creep fracture method at temperatures from 40 to 120°C. The composite curves of the engineering stress at break, the true stress at break, the ultimate extension ratio were constructed as a function of reduced time to break by assuming time–temperature superposition. The temperature dependence of the shift factor aT used in the superposition could be represented by a single equation of the Williams, Landel, and Ferry form. The composite curves of the true stress at break for the samples with different draw ratios were almost the same independently of draw ratio. The composite curves of the ultimate extension ratio for these samples could be reduced to a single curve by assuming that the ultimate extension ratio evaluated with respect to the unit length of the undrawn fibers were constant independently of draw ratio if the time to break and temperature conditions of the measurement were fixed constant. A possible fracture mechanism is discussed on the basis of the fracture mechanisms proposed by Samuels and Peterlin.