bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of water‐soluble polymers using hydrodynamic chromatography
Authors: Hoagland D. A. , Prud'Homme R. K.
Published: April 2003

Hydrodynamic chromatography (HDC) has been successfully applied to measurements of the molecular size and molecular size distribution of high molecular weight, water‐soluble polymers. The scope of the method has been probed by experiments with xanthan, a comparatively stiff polysaccharide, and hydrolyzed polyacrylamide, which possesses a more flexible backbone. Separation occurs during convection of dissolved polymer through the interstitial volume of a chromatography column packed with nonporous beads. Nonequilibrium polymer configurations are readily created by the complex flow between these beads. Such altered configurations strongly affect molecular size measurements. To maximize resolution, hydrodynamic stress must be reduced by employing extremely low flow rates. These low flow rates, particularly important for ultrahigh molecular weight samples, unavoidably lengthen analysis time. Conditions under which chromatograms reflect the size distribution of an injected sample are elucidated. A complete description includes selection of column packing, solvent composition, flow rate, column calibration, and sample detection.
Orientation of polymer chains in films of syndiotactic‐rich poly(vinyl alcohol)
Authors: Yamaura Kazuo , Takeyama Kuniko , Tanigami Tetsuya , Matsuzawa Shuji
Published: April 2003

The infrared spectra of the films of syndiotactic‐rich poly(vinyl alcohol) (s‐PVA) prepared by the casting, frame, and bubble methods were obtained. The band at 705 cm−1 decreased with the increased inclination of the film plane to the direction of the irradiation of infrared rays and was related to the orientation of the molecules in the adsorbed phases of both sides of film.
Study on rough‐surface biaxially oriented polypropylene film. III. Influence of MFI of base resin
Authors: Fujiyama Mitsuyoshi , Kawamura Yoshimasa , Wakino Tetsuo , Okamoto Tomomi
Published: April 2003

In Part II of this series we reported that by using a successively stretching tenter method, biaxially‐oriented polypropylene films (BOPs) with a crater‐like roughness have been obtained by selecting appropriate machine direction (MD) stretching conditions. In the present article, in order to select still better conditions, the influences of melt flow index (MFI) of base polypropylene (PP) and machine and transverse direction stretching conditions on the roughening of BOP have been studied. Rough‐surface BOPs were obtained by casting homoisotactic PPs, having MFIs of 1.3–9.8 dg/min and containing no β‐crystal nucleator, with a T‐die extruder into sheets which subsequently have been stretched successively in the machine direction (MD) and the transverse direction (TD) with a roll‐type stretching machine and a pantograph‐type stretching machine, respectively. The level of β‐crystal content in the cast sheet was maximum when a PP with MFI ≒ 8 dg/min was used as a raw material and the obtained roughness state of the BOP was the best. As for the MD‐stretching conditions, the roughness state of a BOP improved as the surface temperature of the heating roll was increased to a temperature range of 135–150°C, and there was the best roll rotation speed from the balance of the thermal conductivity of the sheet and the melt‐recrystallization rate of the β crystals. A temperature in a range of 150–155°C was best for the TD‐stretching.
Study on rough‐surface biaxially oriented polypropylene film. IV. Influence of addition of crystal nucleator
Authors: Fujiyama Mitsuyoshi , Kawamura Yoshimasa , Wakino Tetsuo , Okamoto Tomomi
Published: April 2003

In the roughening of biaxially oriented polypropylene film (BOP) by utilizing β‐form crystals in a successively stretching tenter method, the influence of an α‐crystal or β‐crystal nucleator added to base polypropylene (PP) during roughening of BOP has been studied. Rough‐surface BOPs were made from homoisotactic PPs which had a melt flow index (MFI) of 8.5 dg/min and contained the α or β nucleator at levels of 0‐10 ppm. The β crystals formed in cast sheets and the roughness of the BOPs was analyzed. Degree of roughness and the diameter of craters on BOP decreased with increasing α‐ or β‐nucleator content. This stems from the fact that the diameter of the β spherulites formed in the cast sheet decreases with increasing nucleator content. In the cases of nucleator content below 1 ppm, the diameter of the β spherulites in the cast sheet did not change significantly, and the decrease in diameter of the BOP craters was small. On the other hand, the degree of roughness of the BOP dropped significantly when nucleator content was above 10 ppm. Accordingly, a nucleator content of about 1 ppm is suitable for the roughening of BOP for both the α and β nucleators.
Dependence of viscoelastic properties on segregation degree of components in interpenetrating polymer networks
Authors: Lipatov Yu. S. , Rosovizky V. F. , Datsko P. V. , Maslak Yu. V.
Published: April 2003

The temperature dependences of elastic moduli, loss moduli, and mechanical loss angle tangent were investigated for the interpenetrating polymer networks: polyurethane–polyurethane acrylate by the method of dynamic mechanical spectroscopy (DMS). The segregation degree of components due to phase separation have been calculated from the parameters of relaxation maxima. An essential change was found in the segregation degree of components with the curing sequence of individual networks being changed. It was shown that, with the conditions and sequence of IPN formation changed, the phase separation degree can be fixed at a particular stage, i.e., the structures with a different segregation degree of components are obtainable. For the IPNs under investigation the variation of elastic moduli of the composites proved possible by fixing the separation degree of components.
Electrodeposition of polyimides from nonaqueous emulsions
Authors: Uebner Michael , Ng Ka M.
Published: April 2003

A theoretical and experimental study was carried out to investigate the process of electrodepositing a polyamic acid film from a nonaqueous emulsion onto a metal surface (copper, aluminum) as well as the subsequent drying and imidization steps. The rate of film growth is controlled by the electrophoresis of the polymer emulsion particles to one of the electrodes and the concomitant film compaction due to the outflow of the solvent caused by electro‐osmosis. Parameters affecting the coating process such as particle size, charge, ζ potential, viscosity of the liquid medium, conductivity of the deposited film, etc. were considered.
Some physical properties of alkali‐treated bhindi fiber (Hibiscus esculentus linn.)
Authors: Sen K. K. , Saha S. C. , Mojumder P. , Ray P. K.
Published: April 2003

Structural features of bhindi fiber have been studied by X‐ray diffractometry, scanning electron microscopy, and infrared spectroscopy. The fiber has multicellular structure and on alkali treatment, it behaves like other lignocellulosic fibers. Infrared spectra indicated that alkali degradation of cellulose and hemicellulose was quite significant in the fiber and that substantial portion of uronic acid was removed as a results of alkali treatment.
Conducting polypyrrole composite thin films chemically prepared by spreading on surface of aqueous solution containing oxidizing agent
Authors: Morita Mitsuyuki , Hashida Isao , Nishimura Masato
Published: April 2003

Polypyrrole–PMMA composite films have been prepared with the chemical oxidative polymerization by spreading the water‐insoluble solvent solution of pyrrole and PMMA mixture on the surface of the aqueous solution containing K2S2O8, the oxidizing agent. The conductivity of the films increases rapidly, passes through a plateau, and then decreases gradually as the reaction time increases. The conductivity of the oxidized side of the film is higher by over 1 order of magnitude than that of the evaporated side. It is due to the fact that the former is rich in polypyrrole while the latter is rich in PMMA. The thickness of the films can be controlled by adjusting the PMMA concentration. However, the lower limit of the film thickness is practically in submicron order. The relationship between the transmittance and the logarithm of the conductivity of the films gives a straight line with a gradient, ca. −8. The conductivity of the films is stable on silicagels in a desiccator over 2000 h at 25°C. The conductivity of the film is, however, very sensitive to the moisture in atmosphere and gives rise to decrease with humidity.
Grafted chain as spacer for an insoluble polymer ligand. II. Two‐step polymerization using tetraethylthiuram disulfide as an initiator
Authors: Arai Kenichiro , Ogiwara Yoshitaka
Published: April 2003

In order to increase the percent grafting in the graft polymerization of chloromethylstyrene onto a crosslinked polystyrene bead with UV light irradiation, a two‐step polymerization consisting of a suspension polymerization of styrene containing divinylbenzene using tetraethylthiuram disulfide as an initiator and then a subsequent graft polymerization of chloromethyl‐styrene onto the crosslinked polystyrene bead was carried out. The percent grafting of up to 180% was obtained, the value being about twofold larger than that for the usual method using benzoyl peroxide as an initiator. The higher percent grafting was found to result from the higher grafting efficiency due to the preferential decomposition of diethyldithiocarbamate group in the crosslinked polystyrene bead with UV light irradiation. The chloromethyl group in the grafted chain was converted to aminomethyl group, and then to the iminodiacetic acid group, which was a ligand group. The adsorption behavior of Cu(II) by the ligand polymer and the catalytic activity of the complex in the decomposition of hydrogen peroxide were examined, and both properties were found to be improved by introducing grafted chain as spacer, especially markedly at a higher percent grafting.
Postcrosslinking of linear polyesters. II. UV‐induced crosslinking agents having carboxyl reactive group
Authors: Inata Hiroo , Morinaga Tsutou , Matsumura Shunichi
Published: April 2003

A previous article reported that polyallyl compounds such as triallyl cyanurate could be applied as an effective melt‐blend‐type ultraviolet (UV)‐induced crosslinking agent for linear polyesters to improve their thermal resistances without sacrificing their melt processabilities. The present article reports the results from further investigation to seek more effective crosslinking agents for the polyesters. Compounds having both allyl and carboxyl reactive groups, such as diallyl glycidyl isocyanurate and 2‐[β‐(3,5‐diallylisocyanuro)ethyl]carbamoyl‐2‐oxazoline have been proved to be more effective UV‐induced crosslinking agents than the simple polyallyl compounds reported previously. The former compounds were coupled with carboxyl terminal groups of the polyesters by reaction in the melt and act as an effective UV‐induced crosslinking agent, which was proved by the observation that the polyester having more carboxyl terminals resulted in higher UV crosslinkabilities. Addition of such compounds to the polyester did not seriously affect the melt stability of the mixtures.
Mechanical denaturation of high polymers in solutions. XXXIX. Flow‐induced crystallization of high molecular weight syndiotactic‐rich poly(vinyl alcohol)
Authors: Yamaura Kazuo , Daimoh Motokazu , Tanigami Tetsuya , Matsuzawa Shuji
Published: April 2003

The crystallization of syndiotactic‐rich poly(vinyl alcohol) (s‐PVA) with a molecular weight of 6.73 × 105 from aqueous solutions was carried out under Couette flow with or without seed crystals. The crystallization of s‐PVA from aqueous solutions occurred below the surface of the solutions even in the presence of seed placed in the solution; whereas, in the case of aqueous s‐PVA solutions containing 0.02% octyl alcohol (antifoaming reagent) only the longitudinal growth of seed occurred. The lengths of the fibers obtained were 2.5 to 3.0 cm.
Production of carbonaceous adsorbents by using novolac‐resin and cottonseed
Authors: Simitzis Johannis , Sfyrakis Johannis
Published: April 2003

Mixtures of novolac resin with pressed cottonseed in different proportions after their curing as small cylinders, and also pressed cottonseed as powder were pyrolyzed until 1000°C. Some samples follow, as well as an activation process by steam between 700 and 950°C. The weight losses of the samples are much higher, up to 500°C, while small weight losses are observed over 800°C. The weight losses for the 100% pressed cottonseed during the carbonization are essentially higher than those of the specimens also containing novolac; indeed, for the total weight losses up to 1000°C an increasing linear dependence was found with increasing proportion of the cottonseed in its mixture with novolac. The shrinkage of the specimens also containing novolac follows in general a curve similar to that of the weight losses for the corresponding case. The specific surface areas of the carbonaceous materials produced show higher values with measuring by CO2 than by N2 due to the larger dimensions of the N2 molecule as compared to the CO2 molecule, so that N2 areas are more sensitive to slight changes in aperture sizes of the porous materials produced. The specific surface areas of the materials that have also been activated indicate higher values in comparison with those without activation and also higher than activated carbon commercially available. The more increased and fine porous structure of the activated carbons as compared to those only pyrolyzed become also obvious from the corresponding photos obtained by the scanning electron microscope. These results are also in agreement with the discoloring ability of the produced adsorptive media for the methylene blue from aqueous solution, following the Freundlich equation for the adsorption.
Studies on the glass transition of blends of nylon‐6 and polyacrylic acid
Authors: Jin Y. , Huang R. Y. M.
Published: April 2003

The glass transition temperatures (Tg) of blends of polyacrylic acid (PAA)–Nylon 6 in various proportions used as membrane material in pervaporation separation of acetic acid–water and ethanol–water mixtures were determined using differential scanning calorimetry (DSC). All the samples examined showed a single Tg which lay between the Tg of Nylon 6 and PAA, indicating that complete miscibility was achieved in these polymer blends. Further evidence of complete miscibility was obtained by scanning electron microscopy (SEM) of cross sections of the blended films which showed a uniform structure. An interesting phenomenon was observed during the DSC measurements which showed a shift in Tg of the blended samples with scanning time. Infrared and thermogravimetric measurements were conducted to further investigate this phenomenon and the results were explained as the change in Tg being caused by the elimination of water molecules and the formation of anhydrides in the polyacrylic acid portion of the polymer blends.
Study on ketalization reaction of polyvinylalcohol by ketones. III. Reaction between polyvinylalcohol and methyl ethyl ketone and behavior of polyvinylketal in water
Authors: Nakamura Naofumi , Aoshima Sadahito , Higashimura Toshinobu
Published: April 2003

Ketalization reaction of polyvinylalcohol (PVA) by methyl ethyl ketone (MEK), dimethyl‐sulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out, and the synthesis of polyvinylketal with any ketalization degree was successfully performed. The reaction mechanism of PVA with MEK is identical with that with acetone: for both cases, the equilibrium constant is ca. 0.07 at 40°C and the heat of reaction is 7.5 kcal/mol. Films prepared from the polyvinylketal were soaked in water and degree of swell, solubility, and hydrolysis of films were measured. The reaction of film with water, in acidic side, easily proceeds, and at first the film swells; then, as deketalization reaction proceeds, the film dissolves in water. With polyvinylketal of the ketalization degree of above 15 mol %, dissolution time is controlled by both ketalization degree and pH of water, which reveals that deketalization reaction proceed proportionally to proton concentration at 37°C. On the other hand, in the neutral condition where hydrolysis does not proceed at all, polyvinylketal of ketalization degree of 10–40 mol % dissolves in water at 0°C. The polyvinylketal obtained by MEK is more stable in water than that from acetone since MEK has hydrophobicity.
Spectroscopic determination of copolymer composition in high isocyanate content polymers
Authors: Brown Richard G. , Glass J. Edward
Published: April 2003

Copolymer compositions high in aliphatic isocyanate content cannot be determined by typical titration methods due to crosslinking during polymer workup. A quantitative method involving ultraviolet analysis of an isocyanate/absorbing amine adduct is presented. Agreement between the ultraviolet (UV) method and elemental analysis, in both composition data and reactivity ratios (r1r2, which are calculated from data obtained by the UV method) delineate a viable method of polymer analysis. Data from Fourier transform infrared (FTIR) analysis of the urea linkage is in good agreement with nitrogen analysis and the UV method, but is sufficiently biased to cause significant differences in r1r2 values. Bias in the infrared analysis may arise from the intra‐ or intermolecular interaction of CO and NH groups of the urea linkage. Hypochromic effects are observed in UV analysis in noncarbonylic solvents. Hypochromicity varied with copolymer composition and could be related to sequence distributions. The hypochromic effects observed were most pronounced in low amine adduct content polymers where the majority of phenyl chromophores are isolated between MMA units.
Graphitization studies of cured phenolic resins by high‐resolution 13C‐cross‐polarization magic angle spinning solid‐state NMR spectroscopy
Authors: Amram B. , Laval F.
Published: April 2003

13C‐cross‐polarization/magic angle spinning solid‐state NMR spectroscopy is used to investigate the graphitization process of a pyrolyzed formophenolic resin. The formation of a 2‐dimensional graphitelike lattice, growing with the duration of the laser pyrolysis, is shown. A one‐parameter‐condensation model is used to estimate, from our dipolar‐dephasing NMR experimental data, the quaternary‐to‐tertiary aromatic fraction, the number of condensed aromatic rings (from 10 to 23 units), and the average cluster diameter (from 9 to 14 Å).
Synthesis, polymerization, and end‐use evaluation of 3‐pentadecylphenyl acrylate and methacrylate
Authors: Sitaramam B. S. , Chatterjee P. C.
Published: April 2003

Two new polymerizable monomers, namely, 3‐pentadecylphenyl acrylate and methacrylate, were synthesized starting from Cashew Nut Shell Liquid. The synthetic method used is simple, and is of general utility. These monomers were homopolymerized by bulk, solution, and emulsion polymerization techniques which yielded moderately high molecular weight polymers that showed promise as pressure‐sensitive adhesive.
Synthesis of nylon 4 through the use of the carbon dioxide/potassium pyrrolydonate catalyst system with and without added 18‐Crown‐6 ether activator
Authors: Huang Robert Y. M. , Rhim Ji‐Won
Published: April 2003

The anionic polymerization of 2‐pyrrolidone at 40°C via CO2/KOH and CO2/KOH/18‐Crown ether catalyst for membrane separation purposes was investigated in detail. The effects of reaction time, CO2 quantity, and potassium hydroxide concentration including crown ether on yield and intrinsic viscosity were also studied. Under the reaction conditions of reaction temperature 40°C, reaction time 24 h, CO2 quantity of 60 s at a constant flow rate of 3.5 L/min and 1.98 mol % Crown ether a maximum yield of 95.36% of nylon 4 polymer with intrinsic viscosity of 3.28 was obtained.
Bonding a HTPB liner to modern rocket case materials
Authors: Sandén Roland , Wingborg Niklas
Published: April 2003

Methods for bonding propellants based on HTPB (hydroxyl‐terminated polybutadiene) to modern rocket motor case materials have been studied. Thus a typical rocket propellant liner, based on HTPB, was adhesion tested to various polymer materials and to an aluminum alloy. The polymer materials are an epoxy resin and composite materials, based on epoxy‐poly(ether sulfone), poly(ether ether ketone), poly(amide imide), and poly(phenylene sulfide). With proper surface treatment, excellent results were obtained at separation tests for all materials with cohesive failure in the liner.
Influence of emulsifiers on film formation from cellulose acetate latexes. Modeling approach to the fate of emulsifiers in highly plasticized films. II
Authors: Bindschaedler C. , Gurny R. , Doelker E.
Published: April 2003

Experimental results on the redistribution of sodium dodecyl sulfate in cellulose acetate membranes produced from latexes (Part I) are interpreted in terms of a framework involving both thermodynamic (affinity of the components, composition) and kinetic (plasticizer evaporation rate) parameters. Two situations were examined, corresponding to liquid–liquid and liquid–solid phase separation. The proposed model better accounts for the observed phenomena than more classical views about the fate of emulsifiers.
Correlated color temperature detection of radiation damage in thermoplastic polyurethane
Authors: Lawandy S. N. , Amera A. M.
Published: April 2003

The correlated color temperature change in a polymer was used as a technique to determine the degree of damage sustained due to radiation exposure. This technique shows fair agreement with the swelling technique. These two methods were used to detect radiation damage in four thermoplastic polyurethane grades of different hardness. Polymers that possess higher amounts of isocyanate groups give better resistance to radiation than to lower isocyanate‐content polymers.
Scratch resistant low friction/low surface energy coating for silicon substrate
Authors: Chen H. H.
Published: April 2003

A smooth, ultrathin film of a polydimethylsiloxane (PDMS) on a silicon substrate has been prepared by spin‐coating. This film gives a 0.06 dynamic coefficient of friction against paper, the lowest value ever reported for polymer–paper sliding pairs. The value is only about one‐third of the coefficient of friction (0.21) between polytetrafluoroethylene and paper. The coating is not scratchable by sliding a stainless steel stylus over the surface with a pressure greater than 3.6 × 1010 dyn/cm2. The film displays a surface tension of 20.5 dyn/cm. It is stable in water and propylene glycol. The film is an effective and durable solid lubricant. The surface characteristics of a spray‐coated PDMS and a plasma‐copolymerized thin film of perfluoropropane and 3,3,3‐trifluoropropylmethyldimethoxysilane have also been investigated. Both films show much lower scratch resistance, weaker adhesion to the silicon substrate, and higher friction. The plasma film yields the same surface tension as the spin‐coated PDMS. Its surface energy, however, increases after soaking in water or propylene glycol. The exceptionally low friction and the unusually high scratch resistance of the ultrathin film of PDMS are attributed to the absence of deformation and tearing components and a low adhesion components in the sliding friction mechanism.
In situ determination of calcium carboxymethylcellulose on a cellulose film via ion exchange
Authors: Chen H. H.
Published: April 2003

A simple and rapid ion exchange method is presented for the in situ determination of calcium carboxymethylcellulose (CaCMC) on a cellulose film. The method is based on the ion‐exchange reaction between the calcium ion in CMC and a large quaternary ammonium ion, such as hexadecyltrimethylammonium ion, followed by a second ion exchange reaction in which the quaternary ammonium ion is displaced by 3,9‐bisdimethylaminophenazothionium ion. The development of a blue color allows for the determination of the CaCMC distribution on the film by using a scanning densitometer. The reasons that CMC prefers a relatively large quaternary ammonium ion to the divalent calcium ion are suggested. This method is also applicable for the determination of sodium carboxymethylcellulose film where it is only necessary to carry out the second ion‐exchange reaction. The minimum detection limit for a CaCMC (degree of substitution is 0.7) coating is at least 1 μg/cm2.
Compatibility of epoxidized natural rubber with thermoplastic and thermosetting resins
Authors: Kallitsis John K. , Kalfoglou Nikos K.
Published: April 2003

The compatibility behavior of epoxidized natural rubber (ENR) at two different degrees of epoxidation with hydroxyl‐containing polymeric resins was investigated. These included Novolac and Resole resins, the cured epoxy of bisphenol A (CER), and phenoxy. For each system, compositions covering the complete range were studied using the dynamic mechanical (DMA), DSC and phase‐contrast microscopy techniques. ENR/Novolac blends were compatible, ENR/Resole, and ENR/phenoxy semicompatible, and ENR/CER incompatible. The results were interpreted in terms of the acid character of the aromatic or aliphatic hydroxyl contained in the resin and a predictive compatibility scheme based on copolymer‐copolymer miscibility theory was tested.
Optimal compositions of molded phenolic resins and its properties
Authors: Chiang Wen‐Yen , Yang Sung‐Yeng
Published: April 2003

Phenolic resins [commercial (CP), pure (PP), and woodflour‐filled (WP)] containing different levels of hexamine, were evaluated in terms of curing behavior as well as thermal, electrical, and mechanical properties. The degree and rate of curing increase markedly with the rise of the hexamine content; however, the dielectric constant, dielectric loss, and dissipation factor decrease gradually. Dielectrical values decrease with the increase of the applied frequency. When the ratios of hexamine to phenolics are increased, samples become harder and experience increased molding shrinkage. With the increase of molding time or temperature, the surface hardness and molding shrinkage improve. The optimal hexamine contents of WP and PP are determined with respect to the above properties.
Quality assessment of polyester chips and yarn by TMS‐2
Authors: Joshi K. A. , Naik G. A. , Nevrekar N. B.
Published: April 2003

Penetration in polyester chips of different manufacturers and yarn (undrawn and drawn) was studied between 323 and 423 K on a thermomechanical system (TMS‐2) using a penetration kit. It was observed that the penetration of the probe varied in the case of chips from manufacturer to manufacturer. The undrawn and drawn yarns from different batches and also within the same batch showed a clear variation in penetration curve, which may be attributed to the degree of crystallization. The same technique can be utilized for an assessment of the quality of yarn in continuous production and for differentiating the manufacturing process of polyester chips.
ESCA and other morphological investigations of the brittle failure caused by an environmental stress cracking (ESC) of a HDPE milk crate
Authors: Kulshreshtha A. K. , Kaushik V. K. , Pandey G. C. , Chakrapani S. , Sharma Y. N.
Published: April 2003

The causes of a drastic reduction in the service life of a HDPE milk crate have been investigated. The mechanism and the type of crate failure have been deduced from a detailed morphological examination of its fracture surface as well as the interior. Various factors responsible for a rapid failure of the milk crate have been identified. An ESCA study of ESC of weathered milk crate surfaces revealed the presence of heavy oxidative degradation on the surface and a diffusion‐controlled oxidation mechanism being operative in successive inner layers. The brittleness of this surface layer and formation of sharp cracks therein have been exhibited in SEM micrographs. Optical micrographs clearly show the presence of a surface layer, formed due to degradation, which is nonspherulitic and thus identifiable from the bulk, which is imperfectly spherulitic. Evidence for a migration of polymer additives from bulk to the surface is provided by the ESCA data and the SEM micrographs. DSC thermogram of the microtomed surface layer reveals bimodal endothermic peaks attributed to two phases present in the surface layer—one original phase and the second being degradation‐induced. The formation of this brittle surface layer and its effect on the long‐term fracture performance of milk crates are discussed, and suggestions for improving their durability are given.
Analysis of radiation chemical yields of chlorinated polystyrene derivatives
Authors: Hartney Mark A.
Published: April 2003

A technique for determining radiation chemical yields from lithographic exposure curves for crosslinking type negative electron beam resists has been extended to include polymers with a general Poisson distribution. The technique is applied to several different chlorine‐containing styrene‐based resists. The radiation yields show good agreement with the differences in lithographic sensitivity and are explained by recent mechanistic studies. Optimal synthetic approaches for preparing this type of resist are described.
Steady‐state and transient behavior of a continuous polyethylene terephthalate condensation polymerization process. I. Melt transesterification stage
Authors: Khan A. A. , Choi K. Y.
Published: April 2003

The steady‐state and transient behavior of a continuous stirred‐tank reactor for melt transesterification of dimethyl terephthalate with ethylene glycol in the presence of metal acetate catalyst is presented. The kinetic model includes the main transesterification reactions and side reactions leading to diethylene glycol and carboxylic acid end groups. The effect of various reactro operating parameters such as [EG]/[DMT] mole ratio and feed catalyst concentration on the product distribution under steady‐state reactor operating conditions is analyzed. The dynamic process model has also been solved and the reactor transients to step changes in various reactor parameters are reported.
Interpenetrating polymer network from castor oil‐based polyurethanes and poly(methyl acrylate). XIV
Authors: Patel Prashant , Suthar Bhikhu
Published: April 2003

Castor oil containing hydroxyl functionality was reacted with 4,4′‐diphenylmethanediisocyanate under different stoichiometric ratios of NCO/OH to obtain liquid polyurethanes. These polyurethanes were subsequently interpenetrated with methyl acrylate monomer using ethylene glycol dimethacrylate as a crosslinker by radical polymerization using benzoyl peroxide as an activator. The polyurethane/poly(methyl acrylate) interpenetrating polymer networks (PU/PMA IPNs) were obtained as tough films by transfer molding techniques. All IPNs were characterized by their resistance to chemical reagents, optical properties, thermal behavior, and mechanical properties: tensile strength, Young's modulus, elongation at break (%) and hardness Shore A. The morphology of the IPNs was studied by scanning electron microscopy and dielectric properties: electrical conductivity (σ), dielectric constant (ϵ′), dielectric loss (ϵ″), and loss tangent (tan δ) at different temperatures.
A comparison of the determination of macromolecular orientation in polypropylene by attenuated total‐reflection fourier‐transform infrared spectroscopy and X‐ray diffraction
Authors: Mirabella Francis M. , Shankernarayanan M. J. , Fernando Priya L.
Published: April 2003

Attenuated total reflection‐infrared (ATR‐IR) spectroscopy and wide‐angle x‐ray diffraction (WAXD) were used to determine the macromolecular orientation of a series of six uniaxially oriented polypropylene sheets with elongations of 0% to 500%. The orientation functions were expressed as fractions of chains oriented along the machine, trasverse, and normal directions in the sheets. Good agreement was found between the orientation functions for the two techniques. Sources of potential difference between the two techniques were discussed. The ATR‐IR technique is surface sensitive to a depth of about 5 or 10 μm into the surface while the WAXD technique is bulk sensitive. The ATR‐IR technique is sensitive to both the crystalline and noncrystalline material while the XRD technique is sensitive only to the crystalline material.
Epoxy–lignin polyblends. III. Thermal properties and infrared analysis
Authors: Feldman Dorel , Banu Dorina , Khoury Marwan
Published: April 2003

Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and IR analysis were performed on a nonviscous epoxy polymer system (EP) with Kraft lignin (L) up to 20%. Mixtures of EP with similar amounts of silica (S) as in EP–L polyblends were used as a reference system for the analyses performed. EP–L polyblends cured at room temperature exhibit a single Tg, a fact characteristic for the monophasic systems. One‐step tensile storage modulus vs. temperature curves, and related one‐peak tensile loss modulus vs. temperature curves were found for all the EP–L polyblends. At about 30°C the tensile storage modulus of EP does not change in the presence of lignin in amounts up to 20% by weight. All these showed that L is miscible with EP and it does not affect the crosslinking at room temperature. IR spectra led to similar conclusions. The gradual decrease of the peak values of tan δ with the amount of L in polyblends is due to an increase in the tensile storage modulus and a decrease of the tensile loss modulus at temperatures close to Tg. This fact is explained by a stronger bond between EP and L, which could be formed at higher temperatures. The DSC and DMA data are in agreement with the mechanical properties of EP–L polyblends, which were reported previously.
Accumulation and desorption of free radicals in emulsion copolymerization
Authors: Hagiopol Cornel , Deleanu Theodor , Memetea Tatiana
Published: April 2003

The emulsion copolymerization of styrene with acrylonitrile, seeded on a polybutadiene support and initiated either potassium persulfate or γ‐rays has been studied. The original technique of support activation consists of two steps: the start of the copolymerization in the presence of a small fraction of monomers, followed by the addition of the rest of monomers, which leads to a great increase in the reaction rate. The experimental data provide evidence for a new mechanism that takes into account the desorption–reentry of the free oligoradicals into another particle, their transfer to the polybutadiene support, which results in the accumulation of trapped free radicals. As a consequence of free radicals' accumulation, the overall copolymerization rate increases. The accumulation as well as the desorption processes place this type of copolymerization far from Smith–Ewart theory case II.
Kinetics of vinylchoride removal from polyvinylchloride by thermal treatment in a flow of inert gas
Authors: Peev G. , Trifonova M. , Peeva L.
Published: April 2003

The kintetics of free monomer removal from powdered suspension polyvinylchloride at elevated temperatures in a nitrogen flow is studied. It is found that in fluidized bed the monomer concentration decreases linearly with time. This behavior cannot be explained by a model of molecular diffusion in single spheres because of particle degradation during the treatment. Conditions for complete vinylchloride removal from the polymer are proposed.
Die geometrical effect on annular die swelling
Authors: Seo Yongsok , Wissler Eugene H.
Published: April 2003

Die geometrical effect on Newtonian annular jet swelling was studied using a finite element method. Numerical result shows what we expected in the limiting cases of die swelling with annular die geometries, i.e., variation of the die gap for straight dies follows the limiting behavior of capillary and planar die swellings. Also the effect of upstream die geometry was investigated. The result shows that final extrudate dimensions are generally influenced by its previous history in the die, i.e., not only by shearing action but also by elongational effect caused by narrowing die gap.
The effect of corona discharge treatment of ethylene copolymers on their adhesion to aluminum
Authors: Hjertberg T. , Sultan B.‐Å , Sörvik E. M.
Published: April 2003

The efficiency of different techniques of obtain improved adhesion in polyethylene‐aluminum laminates have been studied. Both surface treatments, such as thermal oxidation and corona discharge, and the use of copolymers with polar comonomers, i.e., vinyl acetate (EVA) and butyl acrylate (EBA), have been included. Thermal oxidation performed by high temperature extrusion including an ozone shower seems to be more effective than corona discharge. In a model experiment thermal oxidation was studied in more detail. The adhesion, as measured by a T‐peel test, increased with the content of carbonyl measured by reflexion IR, except for relatively long thermal treatments. In the latter case molecular scission gave a large fraction of low molecular weight material with low cohesive strength. For EBA and EVA the peel strength increased linearly with the bulk concentration of comonomer from about 100 N/m for untreated polyethylene to 450 and 300 N/m, respectively, at 5 mol % comonomer. Corona discharge treatment of these copolymers had, however, a most remarkable effect on the adhesion properties. The increases, relative to untreated EBA and EVA, were much more dramatic compared to polyethylene, e.g., three to four and less than two times, respectively. The higher values obtained with EBA are suggested to be due to the conversion of acrylate groups into carboxylic acid. In the case of EVA, loss of acetic acid might instead decrease the content of polar groups.
Reinforcement of EPDM matrices with carbon and polyester fibers—mechanical and dynamic properties
Authors: Ibarra L. , Chamorro C.
Published: April 2003

This paper reports on the study of the mechanical and dynamic properties of composites with an EPDM matrix and short fiber, either polyester or carbon, at three different fiber concentrations. In general, the properties prove to be dependent on fiber concentrations and type, in particular on the final ratio fiber length/diameter. This ratio ranges for carbon fiber over 35–45 and for polyester over 135–175, thus placing the former near the lower limit of acceptability. Evidence is supplied of the existence of adhesion between the matrix and the fiber, in the form of measurements of the swelling and dynamic properties, especially through variation of relative damping and the displacement of the dynamic glass transition temperature towards higher ranges. Composites present a marked property anisotropy.
Influence of solvent penetration on the electrical conductance of pre‐extended FEF carbon black‐loaded rubbers
Authors: Amin M. , Nasr G. M. , Khairy S. A. , Ateia E.
Published: April 2003

The penetration of organic solvent and its influence on the electrical conductance of pre‐extended styrene butadiene (SBR), butadiene (BR), acrylonitrile butadiene (NBR), butyl (IIR), and natural (NR) rubbers are investigated. A model is proposed for a process by which it is possible to estimate the separation distance between carbon black particles (or aggregates) and its dependence on the extent of penetration of the liquid. An empirical formula is suggested to describe the variation of the conductance of rubber composites with swelling time in terms of the interspacing distance.
Reaction rate and MWD changes in crosslinking of PVC, with dithioltriazine
Authors: Hjertberg Thomas , Dahl Roger , Sörvik Erling
Published: April 2003

The reaction rate of crosslinking of PVC with dithioltriazine has been studied by following gel formation and changes in the molecular weight distribution (MWD). Compounding was performed on a roll mill at 145°C and crosslinking by heat treatment at 180 or 90°C. In this system crosslinking is executed by the thiolate anion, formed in situ by reaction with MgO. We have studied the catalyzing effect of several polyols in order to achieve a more efficient reaction. Most likely, these catalysts work by chelating the Mg2+ ions, thus increasing the nucleophilic character of the thiolate. With the most efficient ones, ditrimethylolpropane and HO(CH2CH2)6‐7H, complete crosslinking can be obtained in 3 min at 180°C, i.e., at processing temperatures. We also followed the changes in the MWD before gelation at a considerably lower temperature, 145°C, and found an extensive molecular enlargement even after 5‐10 min. Most surprisingly, μMn increased up to 100% without formation of insoluble material. By 1H‐NMR measurements on low molecular weight extracts, we have shown this to be due to a fast and selective reaction with allylic chlorine in the unsaturated end groups, ∼ CH2CHCHCH2Cl, formed in the mechanism of chain transfer to monomer. Due to this reaction, formulations with too high reactivity may crosslink during processing, which calls for a careful balancing of the reactivity for each processing case.
Studies on polypyromellitimides containing phosphorus
Authors: Varma Indra K. , Saxena Sneh , Varma D. S.
Published: April 2003

The paper describes the synthesis of several polypyromellitimide samples containing phosphine oxide in the backbone and maleimido groups as pendant side chains. These polymers were obtained by solution polycondensation reaction in DMF in three steps. First step involved the reaction of equimolar amounts of maleic anhydride (MA) and tris(3‐aminophenyl) phosphine oxide (TAP) in DMF at 60°C for 2 h. Low temperature polycondensation was carried out at 0–5°C by the addition of 4,4'‐diaminodiphenyl ether (DADPE) and pyromellitic dianhydride. Cyclodehydration of poly(amide acid) thus obtained was done by chemical means. Various copolymers thus obtained were characterized by intrinsic viscosity measurements, elemental analysis, and IR spectroscopy. Thermal behavior and curing characteristics of copolyimides were evaluated by thermogravimetry and differential scanning calorimetric studies. An increase in the char yield at 800°C was observed on increasing phosphine oxide content of polyimides.
Invariant kinetic parameters of polymer thermolysis. II. Butyl rubber pyrolysis
Authors: Levchik S. V. , Levchik G. F. , Lesnikovich A. I.
Published: April 2003

The methodological problem of correct estimation of invariant Arrhenius parameters Ǎ and Ě from nonisothermal experiments has been analyzed for thermal decomposition of commercial butyl rubber in inert atmosphere. It is shown that restriction of the kinetic analysis by varying n in the function f(α) = (1 − α)n may yield incorrect Ǎ and Ě. It is necessary to apply the set of f(α) known in the formal topochemical reactions kinetics for correct estimation of Ǎ and Ě.
Influence of steric length in electrosteric surfactants on emulsion polymerization
Authors: Dittman‐McBain Carla B. , Piirma Irja
Published: April 2003

Four PPG Avanel Series S surfactants (sodium alkyl polyether sulfonates) with varying ethylene oxide content (n = 3, 7, 9, and 15) were used to investigate the influence of the steric length in this type of electrosteric stabilizers on emulsion polymerization. The polymerization studies employing potassium persulfate as an initiator with styrene, methyl methacrylate, and vinyl acetate monomers showed no apparent change in particle size, number of particles, and polymerization rate with the changing steric length of the surfactant. Steric influences were observed in the redox‐initiated systems of styrene, butyl acrylate, and methyl methacrylate. Increasing the ethylene oxide unit content from three to nine units decreased the rate of polymerization, the particle size and number in the polystyrene latexes. Polymerizations with the acrylates displayed the same trend except that the polymerization rate reached a minimum value at nine ethylene oxide units and increased when the surfactant containing 15 ethylene oxide units was used.
Plasma‐modified Nylon 4 membrane for dialysis
Authors: Lai J. Y. , Chou C. C.
Published: April 2003

The effects of plasma treatment conditions, such as supply power, treatment time, gases used in reactor, surface energy, water content, dialysis permeability, partition coefficient, diffusion coefficient, and free volume of Nylon 4 membranes, were studied. The solutes considered for dialysis system were NaCl, urea, and MgCl2. The permeabilities of NaCl and urea of membranes with plasma treated in argon at 80 W for 20 min are 5.57 × 10−5 and 5.89 × 10−5 cm2/min, respectively. Much higher permeabilities of NaCl and urea obtained by oxygen plasma‐treated membranes under 20 W and for 20 min are 30.74 × 10−5 and 17.66 10−5 cm2/min, respectively, compared to that of untreated Nylon 4 membranes.
Stress evolution analysis in postforming cooling
Authors: Cohen A. , Dibbs M. G.
Published: April 2003

An interaction between heat transfer, shrinkage, and stress relaxation during postforming cooling of thermoplastic materials was studied. In order to arrive at a treatable mathematical formulation, while retaining the basic physical effects, the one‐dimensional case was analyzed with the relaxation spectrum approximated by a single relaxation time depending on temperature. An effective relaxation parameter β controlling the postforming behavior was identified. Its dependence upon the relaxation time, rate of heat transfer, and a temperature interval was established. An analytical approximation for a maximal tensile stress was developed. This result enables an understanding of the interaction between cooling conditions and material behavior.
Synthesis, characterization, and kinetic study on the thermal decomposition of polyamidoethers
Authors: Ahmed I. K. , Rashid M. A. M. , Kafaf B. T.
Published: April 2003

Some new polyamidoethers have been synthesized by condensation reaction of N,N'‐dichloroacetyl‐1,4‐phenylene‐diamine with bisphenols (4,4'‐isopropylidenediphenol, 4,4'‐dihydroxydiphenyl sulfone, 4,4'‐dihydroxydiphenyl sulfide, and 4,4'‐dihydroxybiphenyl) in N‐methylpyrrolidone medium using DB‐24‐Crown‐8 as a phase‐transfer catalyst. The structure of these polymers has been characterized by infrared (i.r.) and 1H nuclear magnetic resonance (NMR) spectroscopy. Kinetic method of thermal decomposition of these polymers and their 2% mixture with polyvinylchloride (PVC) has been studied.
Mechanism of poly(methyl methacrylate) fire retardation by Wilkinson's salt
Authors: Sirdesai Sunil J. , Wilkie Charles A.
Published: April 2003

The reaction of Wilkinson's salt, CIRh(PP3)3, and poly(methyl methacrylate) (PMMA) has been studied. Char formation is observed, and some 30% of the reaction product is nonvolatile at 600°C. In order to understand the pathway of this reaction, the reaction of dimethylglutarate (DMG) and CIRh(PP3)3 has been studied. A pathway is proposed in which the initial step is the oxidative addition of the rhodium species into a carbon—oxygen bond of the DMG molecule. Six different products have been isolated from this reaction and can be seen to result from the oxidative insertion. This pathway also seems to apply to the PMMA reaction and leads to an interpretation of the results of this reaction and permits one to understand the role of this, and similar, compounds as flame retardants.