bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of ion exchange membranes by plasma polymerization. I
Authors: Sakata Jiro , Wada Mitsuo
Published: April 2003

Plasma polymerizations of three kinds of amines, γ‐aminopropylethoxydimethylsilane (APEMS), allylamine (AA), and pyrole (PY), were investigated by IR and XPS analysis. Plasma‐polymerized films were deposited on porous substrates, and ion exchange abilities of the composite membranes were measured. When APEMS were used as the monomer, the polymer retained the chemical structure of the monomer, amino groups. However, when AA and PY were used as the monomers, the plasma polymers contained a larger amount of amido structures than did the polymer of APEMS. Each membrane had ion exchange ability. In particular, the membrane prepared from APEMS showed superior ion exchange ability, anion permselectivity and conductivity, in acidic solutions. This property was attributed to the chemical structure of the polymer from APEMS retenting amino groups. The ion exchange properties of the membranes depended on the pH of the solution. In particular, the membrane of APEMS showed high membrane potential and low electric resistance only in a narrow pH region due to the weak basicity of amines and the hydrophobic property of the polymer.
Dynamics of the threadline in melt spinning
Authors: Martin W. K.
Published: April 2003

In the nylon 6 melt spinning process at speeds of 900 and 1200 m/min the quenching is done in a stepwise manner. The effect on physical data of the drawn yarn is investigated and correlation between quench height, water takeup, and boiloff shrinkage discussed. Length changes across the takeup machine are also measured as function of quench height and seem to correlate with physical data. The speed of length changes for both finished and unfinished yarn as a function of quench height suggests a molecular oscillation along the spinning line rather than a continuous orientation of the molecular structures. A secondary disorientation zone is defined.
Studies on some physical properties and structural characteristics of methyl methacrylate‐grafted silk fiber
Authors: Tsukada Masuhiro
Published: April 2003

Structural characteristics and physical properties of methyl methacrylate‐grafted silk fiber from Bombyx mori were studied by X‐ray diffractometry, differential scanning calorimetry (DSC), thermogravimetry, and scanning electron microscopy. Methyl methacrylate (MMA)‐grafted silk fiber with a grafting yield of more than 30% showed two endothermic peaks at 320°C and 390–410°C, which are attributed to the thermal decomposition of silk fibroin and MMA polymer filled in the fiber, respectively. These DSC results indicate that MMA‐grafted silk fiber showed a poor compatibility in the relation between the silk fibroin molecules and MMA polymer. The weight of the MMA‐grafted silk fiber decreased as observed at 160°C on the thermogravimetric thermograms due to the evaporation of water from the sample with increasing graft yield. The crystalline structure of MMA‐grafted silk fiber remained unchanged regardless of MMA grafting. Taking into account the X‐ray diffraction patterns and the increasing graft yield with reaction time, it is assumed that the graft chains of MMA polymer have penetrated into a weak aggregate region and not in the crystalline region of silk fibroin.
The effect of thermal aging on xanthan solutions
Authors: Milas M. , Linossier J. L. , Contat F.
Published: April 2003

The viscosity stability of xanthan solutions is crucial to petroleum recovery processes. The effects of oxygen concentration, pH, and temperature on viscosity during aging up to 6 months were studied. The structure modifications of the xanthan (substituent contents, weight‐average molecular weights) with aging times were followed and related to viscosity loss. In all cases, the acetyl groups were hydrolyzed. The best stability to thermal aging corresponds to neutral or basic conditions with very low oxygen concentrations. At these conditions the viscosity was stabilized to about 50% of its initial value after 6 months at 80°C. In these cases the pyruvate groups were not hydrolyzed. The stabilization of main chain breaks in the ordered xanthan conformation improves the stability results.
Charring processes in thermoplastic polymers: Effect of condensed phase oxidation on the formation of chars in pure polymers
Authors: Martel B.
Published: April 2003

Fifteen different pure polymers were studied by thermal methods under air, nitrogen, and nitrous oxide in order to determine their tendency to char in relation with their structure and the experimental conditions used. Styrene polymers and aliphatic polyolefines give chars under air and total volatilization without carbonization under nitrogen and nitrous oxide, showing the essential part played by oxygen in the charring process. On the opposite, ambient oxygen has some effect on the carbonization of polymers containing aromatic rings in their main chain. A schematic mechanism of the charring process is discussed in which condensed phase oxidation, formation of olefinic bonds and crosslinking, dehydrogenation–aromatization are postulated.
Continuous preparative method of relatively large and uniform polymer beads and their application to immobilization of urease
Authors: Ogawa N. , Kawauchi Y. , Nishimura K. , Sugii A.
Published: April 2003

An apparatus for continuous preparative method of polymer beads was investigated. Monomer droplets formed in glycerol were continuously introduced to a rotating glass tube which was filled with warmed glycerol and polymerized. Polymer beads of around 4 mm diameter were obtained. As an application of the polymer beads, urease was immobilized on the beads and their properties were evaluated. Macroreticular type of beads prepared with a mixture of maleic anhydride, styrene, and divinylbenzene showed the highest enzymatic activity among the beads tested, and the urease immobilized beads could be successfully applied for determination of blood urea nitrogen in human sera.
The oxygen index method in fire retardance studies of polymeric materials
Authors: Camino G. , Costa L. , Casorati E. , Bertelli G. , Locatelli R.
Published: April 2003

The oxygen index test is a fundamental tool in basic research on polymer combustion and on mechanisms of fire retardance. Although the oxygen index should provide an evaluation of intrinsic flammability of polymeric materials, its response may depend on geometry of the specimen. This is shown by comparing the behavior of polypropylene fire retarded with different additive systems. The implication of such in mechanistic studies is discussed. Furthermore, new measurements are proposed to be carried out with the oxygen index apparatus, which give parameters related to ease of ignition, behavior on forced burning, and thermal insulating characteristics of char developed on burning the material.
Effect of impurities on emulsion polymerization: Case II kinetics
Authors: Huo B. P. , Campbell J. D. , Penlidis A. , MacGregor J. F. , Hamielec A. E.
Published: April 2003

The effects of water‐soluble and monomer‐soluble impurities on the kinetics of emulsion polymerization of monomers following Case II kinetics (e.g., styrene) are investigated. Experimental studies reveal that impurities can have an appreciable effect on both polymer particle nucleation and growth. These effects are shown to be well predicted by a mathematical model.
Block copolymers derived from azobiscyanopentanoic acid. XI. Properties of silicone–PMMA block copolymers prepared via polysiloxane(azobiscyanopentanamide)s
Authors: Inoue Hiroshi , Ueda Akira , Nagai Susumu
Published: April 2003

Mechanical, thermal, and surface properties of poly(dimethylsiloxane)–poly(methyl methacrylate) block copolymers (PDMS‐b‐PMMA) prepared by the use of polysiloxane(azobiscyanopentanamide)s were intensively investigated. The mechanical strength of block copolymers was found to decrease with an increase of siloxane contents. Dynamic mechanical analysis (DMA) of block copolymers having long siloxane chain length (SCL) and high siloxane content revealed the existence of two glass transitions attributable to microphase separation of two segments. Differential scanning calorimetry (DSC) also gave some evidence of microphase separation supporting the DMA results. It was observed that the incorporation of PDMS segments in block copolymers improved thermal stability of PMMA, as confirmed by thermogravimetric analysis. Surface analysis of the block copolymers films cast from several solutions indicated surface accumulation of PDMS segments, as revealed by water contact angle and ESCA measurements.
Structural characteristics of 2‐hydroxyethylmethacrylate (HEMA)/methacrylamide (MAA)‐grafted silk fibers
Authors: Tsukada Masuhiro
Published: April 2003

A series of 2‐hydroxyethylmethacrylate (HEMA)/methacrylamide (MAA)‐grafted silk fibers obtained in various comonomer compositions was prepared and their structural characteristics were studied by X‐ray diffractometry, differential scanning calorimetry, and scanning electron microscopy. HEMA/MAA‐grafted silk fibers with a graft yield of about 60% obtained in a HEMA/MAA mixture system containing 20% of HEMA and 80% of MAA on a weight basis showed endothermic peaks at 280 and 420°C (shoulder form), which are attributed to the thermal decomposition of the MAA and HEMA polymers, respectively, in addition to the thermal decomposition peak of the silk fibroin fiber which appeared at 323°C. These DSC results suggest that the HEMA/MAA‐grafted silk fiber showed a low compatibility in the relation between the silk fibroin molecules and HEMA and/or MAA polymers. The crystalline structure of the HEMA/MAA‐grafted silk fiber remained unchanged regardless of the HEMA/MAA grafting ratio even when the graft yield value reached 120%.
Processing of ultrahigh molecular weight polyethylene
Authors: Wang Xi‐You , Li Sheng‐Ying , Salovey R.
Published: April 2003

The extent of recrystallization of nascent UHMWPE powder is easily measured by calorimetry. Melting and recrystallization of nascent UHMWPE at 140°C can be suppressed by compression molding. Crystals of UHMWPE prepared from dilute solution show a peak melting temperature of 140°C and exhibit crystallinity up to 75.5% depending on crystallization temperature. Large changes in crystallinity result from drawing single crystal mats or compression‐molded films.
Characterization of copolymers of N‐vinyl‐2‐pyrrolidone with 2‐phenyl‐1, 1‐dicyanoethene
Authors: Kharas Gregory B.
Published: April 2003

Copolymers of N‐vinyl‐2‐pyrrolidone and 2‐phenyl‐1, 1‐dicyanoethene were studied. Infrared, proton, and carbon‐13 spectra of the copolymers are discussed by comparison with poly(N‐vinyl‐2‐pyrrolidone), model compounds, and various copolymers. Thermal behavior of the copolymers was investigated by using DSC, TMA, and TGA methods. Thermal as well as thermooxidative stability of the copolymers was found to be lower than those of poly(N‐vinyl‐2‐pyrrolidone).
Modification of polyimide coatings by high energy ion bombardment
Authors: Zussman M. P. , Wood S. , Scala L. C. , Bartko J. , Vincenz A.
Published: April 2003

Exposure of 25‐μm films of polyimide and polyamideimide to high doses (> 1015/cm2) of energetic ions (energy ≥ 100 keV) resulted in physical and chemical modification of the film surface. Cross‐section microscopy revealed damaged layers extending beyond the projected ion range; conductivity in this damaged layer was found to be as high as 103ω−1 cm−1. Surface conductivity was found to be a function of ion energy and dose, with an exponential energy dependence from 200 to 900 keV. The temperature dependence and thermal stability of the surface conductivity were determined.
Development of an elastomer with a high static or breakaway friction coefficient
Authors: Meier Joseph F. , Siemon John T. , Quirk James F.
Published: April 2003

This paper reviews the literature concerning the measurement of friction coefficients (μ) for elastomers and summarizes our data measured under static or breakaway conditions against epoxy painted steel using ∼ 176 psi contact pressure. Although largely related to missile launch system applications, the μ values presented are specific for interface pairs, normal loading force, and speed. Therefore, this article should serve as a starting point for those requiring specific friction data for selected elastomers.
Chemical modification of poly(2,6‐dimethyl‐1,4‐phenylene oxide) via phase transfer catalysis
Authors: Percec Simona
Published: April 2003

The chemical modification of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) has been performed under phase transfer catalyzed (PTC) conditions. Four types of reactions: Williamson etherification, cyanide displacement, esterification, and heterocyclic group transfer have been identified as positive reactions involving the nucleophilic displacement on PPO. In reaction with alcohols, under PTC conditions, functional yields as high as 100% were obtained while for the esterification reaction functional yields of 92% were reached. Low conversions were found in reactions with cyanides and heterocylic compounds. Possible interactions of the reactive sites leading to additional crosslinking are being suggested. Minor changes in thermal stability of substituted PPO compared with the parent polymer were recorded. The modification of their permeation properties to gases was attributed to changes in polymer chain mobility and packing as well as to changes in polymer side chain polarity.
Moisture‐induced plasticization of amorphous polyamides and their blends
Authors: Ellis T. S.
Published: April 2003

The moisture‐induced plasticization of some amorphous polyamides in pure and blended form has been determined by calorimetric methods. The compositional dependence of the glass transition temperature of these polymer‐diluent systems has been adequately accounted for using an existing predictive expression derived from both a conformational entropy and a thermodynamic treatment of the glass transition phenomenon. The success of this approach to account for the behavior of amorphous polyamide blends containing hydrophobic and hydrophilic constituents exemplifies the importance of compositional parameters in determining the overall response of morphologically complex hydrophilic polymers. The results add further credence to the simple plasticizing action of water in polar polymers irrespective of their chemical and physical constitution.
Modification of natural rubber tubes for biomaterials I. Radiation‐induced grafting of N,N‐dimethyl acrylamide onto natural rubber tubes
Authors: Razzak Mirzan T. , Otsuhata Kasushige , Tabata Yoneho , Ohashi F. , Takeuchi A.
Published: April 2003

Radiation‐induced simultaneous grafting of N,N‐dimethyl‐acrylamide (DMAA) onto natural rubber (NR) tubes has been studied to improve blood compatibility of the NR tubes. Concerning grafting of DMAA onto NR tubes, it was found that the grafting proceeds effectively in the presence of carbon tetrachloride (CCl4) as a solvent. The degree of grafting was found to be saturated at about 26 wt%, but a higher degree of grafting can be obtained by either “so called two‐step grafting” or “putting a standing time for a while before irradiation.” The initial grafting rate was proportional to 0.85 power of dose rate. The apparent activation energy of the graft‐copolymerization was 7.42 kcal/mol. Evaluation of blood compatibility of DMAA‐grafted NR tubes has been carried out by ex vivo test. According to the results, significant improvement of blood compatibility was obtained for the samples in which degree of grafting is higher than 30 wt%.
Sample overloading effects in polymer characterization by field‐flow fractionation
Authors: Caldwell Karin D. , Brimhall Steven L. , Gao Yushu , Giddings J. Calvin
Published: April 2003

There are two subtechniques of field‐flow fractionation (FFF), thermal FFF and flow FFF, that have been successfully employed for polymer fractionation and characterization. These techniques are primarily analytical in nature, yielding accurate polymer characteristics from small sample loads (∼ 10 μg or less, depending on detection sensitivity). In this study the effects of increasing sample size are examined. Modest increases in load are found to result in shifts toward higher retention volumes. These modest loads also result in some broadening of the sample peaks without a major loss of peak symmetry. Excessive loading, by contrast, appears to give rise both to skewed peaks and to new artifact peaks at higher levels of retention. These observations are discussed in terms of the concentration dependence of various properties (viscosity, diffusivity, thermal diffusivity) which influence polymer transport through the FFF channel. The results are used to indicate upper limits to suitable sample concentrations.
Thermotropic polyester carbonates. III. Thermotropic polyester carbonates as self‐reinforced plastics
Authors: Lai Y.‐C. , Debona B. T. , Prevorsek D. C.
Published: April 2003

Thermotropic polyester carbonates derived from t‐butylhydroquinone, methylhydroquinone, diphenyl terephthalate, and diphenyl carbonate in the molar ratio of 50 : 50 : 55 : 45; 50 : 50 : 57.5 : 5 : 42.5 and 50 : 50 : 60 : 40 can be injection molded successfully from temperatures 10°C below melting to 30–40°C above melting. Normally the best molding temperatures are 10–20°C above melting. If the molding conditions are controlled properly, tensile strengths as high as 1.8 × 104 psi, tensile moduli as high as 7.4 × 105 psi, and flex moduli as high as 1.1 × 106 psi can be obtained.
Polymerization in gel‐like emulsions
Authors: Ruckenstein Eli , Kim Kyu‐Jun
Published: April 2003

Polymerization of styrene in gel‐like emulsions (concentrated emulsions which have a volume fraction of monomer greater than 0.74), by using sodium dodecylsulfate as emulsifier and small amounts of water, was carried out with an oil‐soluble initiator, AIBN. Both higher conversions and higher molecular weights of the polymer were obtained as compared to the polymerization in bulk. The higher “rigidity” of the monomer in the interior of the cells of the gel is responsible for the increased rate of polymerization and molecular weight. The polymer particles thus obtained have diameters in the range of 0.1 to 0.3 μm, depending upon the conditions of preparation of the gel. The effects of the concentration of the initiator, the concentration of surfactant, the monomer volume fraction, termperature, and ionic strength of the aqueous solution have been investigated.
Study on rough‐surface biaxially oriented polypropylene film. VI. Roughening by laminated cast sheet
Authors: Fujiyama Mitsuyoshi , Kawamura Yoshimasa , Wakino Tetsuo , Okamoto Tomomi
Published: April 2003

When the roughening of biaxially oriented polypropylene film (BOP) is performed by forming β crystals in a monolayer cast sheet, occasionally voids are formed in the BOP. In order to prevent this and to roughen both sides of the BOP, rough‐surface BOPs were obtained by casting two‐resin, three‐layer sheets consisting of two surface layers with a high‐melt flow index (MFI) polypropylene (PP) and a core layer with a low‐MFI PP, by stretching the cast sheets five times in the machine direction (MD) with a roll‐type stretching machine, and by stretching the MD‐stretched sheets 10 times in the transverse direction (TD) with a pantograph‐type stretching machine. Comparatively large spherulites were observed in the surface layers of the cast sheets and structural differences between the surface layers and core layer were recognized. Both sides of the cast sheets could be roughened. The influence of processing conditions on the roughness state of BOP was generally similar to that in the case of monolayer cast sheet.
Thermal degradation of poly(aryl‐ether–ether‐ketone) (PEEK): A differential scanning calorimetry study
Authors: Day M. , Suprunchuk T. , Cooney J. D. , Wiles D. M.
Published: April 2003

Differential scanning calorimetry (DSC) has been used to study the crystallization kinetics and thermal characteristics of poly(aryl‐ether–ether‐ketone) (PEEK) samples heated under a variety of conditions. Samples were heated in nitrogen and air at temperatures between 380 and 420°C for times up to 120 min. The results indicate that as the holding time and temperature of the melt increased, the amount of recrystallizable material decreased, especially when heated in air. Isothermal crystallization kinetics confirmed the presence of a two‐stage crystal nucleation and growth process with Avrami exponents of the order of about 2.4 and 1.5 for the first and second processes, respectively. Analysis of the primary crystallization process using the Avrami equation revealed that PEEK samples heated above the melt temperature in air crystallized at a much slower rate than samples heated in nitrogen.
Organotin polymers. XII. Azeotropy in binary and ternary copolymerization reactions of di(tri‐n‐butyltin) itaconate with acrylic acid esters, styrene, and acrylonitrile
Authors: Shaaban A. F. , Mahmoud A. A. , Messiha N. N.
Published: April 2003

Binary and ternary copolymerizations of di(tri‐n‐butyltin) itaconate (TBTI) with methyl acrylate (MA), ethyl acrylate (EA), n‐butyl acrylate (BA), styrene (ST), and acrylonitrile (AN) were carried out in solution at 70°C in the presence of a free‐radical initiator. Experimental terpolymerization data agreed well with calculations based on the Alfrey–Goldfinger equation. The determination of unitary, binary, and ternary azeotropies of the various systems studied was easily handled by a computer. Ternary azeotropic compositions for TBTI–MA–AN and TBTI–EA–AN systems were 37 : 48 : 15 and 9 : 80 : 11 mol %, respectively. Also, “Pseudo‐azeotropic” regions were identified where the deviation between feed and polymer compositions is very small.
Mechanism of accelerated photofading of thioether anthraquinone dyes in styrene butadiene resins
Authors: Paine Anthony J. , Winnik Françoise M. , Bocking Victor
Published: April 2003

Many anthraquinone dyes fade in visible light up to 100 times faster in styrene butadiene copolymers than in polyester resins or polystyrene. A mechanistic investigation of the photofading of 1,5‐dihydroxy‐2,6‐diisobutyl‐4‐thiophenylanthraquinone has established that the dye sensitizes formation of singlet oxygen, a very reactive species, which attacks the double bonds in the styrene butadiene, resulting in extensive chain cleavage and peroxide formation. The major process is the oxidation of the polymer, and the dye fading is a minor process whereby the dye is apparently attacked by polymeric peroxides. The mechanism appears to be general for anthraquinone dyes, especially those with thioether, amino, hydroxy, or double‐bond functionality. Unfortunately the fading is unaffected by most anticxidant stabilizers: the best result achieved was a doubling of half‐life with 1 wt% Spinuvex A‐36. This is still insufficient to give colored styrene butadiene copolymer resins the intrinsic dye stability available in other polymers, rendering styrene butadiene unsuitable for applications requiring high photostability of anthraquinone dyes.
Optimizing poly(chloro‐p‐xylylene) or parylene C synthesis
Authors: Sharma Ashok K. , Hahn Allen W. , Nichols Michael F.
Published: April 2003

Current interest for implantable insulating biomaterials has resurrected a class of polymers synthesized from p‐xylylene and its derivative dimers. Important kinetic aspects for the synthesis of the polymer are derived from measurements of chamber pressure and total weight of film deposition. Reduction of peak chamber pressure during polymer deposition was found to improve film quality, uniformity of deposit, adhesion, and transparency. A low‐cost reactor design is proposed which simplifies the deposition characterization steps needed for producing high quality films.
Far infrared birefringence versus other orientational measurements of high‐pressure injection‐molded high‐density polyethylene
Authors: Boldizar Antal , Jacobsson Stellan , Hård Sverker
Published: April 2003

Far infrared (FIR) birefringence is a new tool for measuring orientation in semicrystalline polymers. In this work FIR birefringence of high‐pressure injection‐molded high‐density polyethylene (HDPE) was compared with wide‐angle X‐ray scattering (WAXS) and shrinkage for the first time. An indirect measure of orientation was obtained by differential thermal analysis (DTA). The content of high‐temperature melting crystals was found to increase with increasing orientation. A high correlation was found between FIR birefringence and the other orientational measurements. Contrary to the other orientational methods used, FIR birefringence does not saturate with highly oriented samples. It is furthermore faster, nondestructive, and can be used for probing fairly thick samples.
Effect of fillers on electrical properties of epoxy composites
Authors: Sastry S. Sreehari , Satyanandam G. , Raj T. F. Sundar , Vasanthakumari R.
Published: April 2003

The effect of fillers such as glass, ferrite, and carbon on the dielectric properties of epoxide resin along with conductivity has been studied as a function of frequency (1–100 kHz) and temperature (30–200°C). The glass transition temperature is not much affected by the presence of the fillers. The observed higher values of dielectric permittivity and loss in the case of filled polymers are attributed to Maxwell–Wagner–Sillars polarization.
Enhanced compatibility of SAN and PC in their blends exposed to extremely high shear field
Authors: Takahashi Hideroh , Matsuoka Takaaki , Ohta Takashi , Fukumori Kenzo , Kurauchi Toshio , Kamigaito Osami
Published: April 2003

Originally incompatible blends of SAN 30% and PC 70% were extruded with extremely high shear rate up to 107 s−1 as a typical example of the blends. The materials were examined with a scanning electron microscope (SEM), a pulsed NMR, etc. The molecular weight of the blends was also measured with gel permeation chromatography. The blends are of binary systems microscopically in the first run of extruding, in which the minor constituent is present as small spherical particles in the major constituent. The apparent volume fraction of the spherical minor constituent estimated from the microscopic photographs decreases with the shear rate. The fraction is decreased also with the repeated runs. SEM observation reveals that dimple fracture of microsize takes place on SAN sphere dispersed in PC matrix. And at the bottom of the dimple, a small particle, which would be composed of PC, is present. From these, SAN in the blend is thought to be partly ductile even at the temperature of liquid nitrogen. At the fifth run, the blend appears uniform or structureless. Dynamic loss tangent gives two peaks corresponding to that of SAN and that possibly attributed to PC. The latter shifts to lower temperatures with the number of extruding run. These show that some of SAN is mixed with PC in a compatible form. The pulsed NMR analysis supports the conclusion. Furthermore, the analysis suggests that some of SAN is mixed in PC. This result shows the compatibility of SAN with PC is enhanced in extremely high shear rate processing.
Impact fracture behavior of continuous glass fiber‐reinforced nylon 6
Authors: Otaigbe J. U. , Harland W. G.
Published: April 2003

The impact fracture toughness of nylon 6/continuous glass fiber composites at four levels of fiber content has been studied. The composites were produced by anionically polymerizing caprolactam within a glass mat using a vacuum injection technique. Application of linear elastic fracture mechanics to characterize the impact fracture toughness of the composites, using an energy approach (GIC), has been found to be applicable provided that a correction is made for the size of the damage zone. The concept of Jc, fracture energy per unit ligament area, has also been applied to the composites and agreement between GIC and Jc has been found to be reasonably satisfactory. The ratio of crack propagation energy to the total energy absorbed (ductility index) has also been calculated. The ductility index was found to be close to one for the composites, indicating that additional energy is involved in propagating the fracturing cracks probably due to fiber debonding and/or crack blunting and fiber pullout. Fractographic examination of the impact fracture surface confirmed the presence of these features.
Solubility properties of poly(1,1‐difluoroethylene) in dipolar aprotic solvents
Authors: Galin J. C. , Lutringer G. , Galin M.
Published: April 2003

A screening study of the solubility of poly(1,1‐difluoroethylene) (PVF2, M̄w = 2 × 105) at room temperature in a wide variety of dipolar aprotic species has facilitated the discovery of a series of new solvents (N‐methyloxazolidone, cyclic‐substituted ureas) and rationalization of the data in a two‐dimensional solubility map involving their dipole moment, μ, and their hydrogenx‐bond‐accepting (HBA) power β (Taft solvatochromic parameter). This map may be used as a predictive tool for the research of new functional classes of solvents, such as N‐substituted mixed amideester of phosphoric acid or N‐substituted sulfurous diamides. The variations of the intrinsic viscosity of the polymer with solvent polarity may be quantitatively analyzed using a linear multiparametric correlation which emphasizes the two opposite contributions of cavitation effects (Hildebrand solubility parameter δ) and of polymer–solvent interactions (β) on the coil expansion: [η] (dL.g−1) = 0.792 ‐ 1.2 × 10−3δ2(J.cm−3) + 1.59 β. Finally, 1,3‐dimethyl‐2‐oxo‐hexahydropyrimidine (N,N′‐dimethylpropylene urea) leads to the highest value of the refractive index increment (dn/dc = −0.065 mL.g−1 at λ = 632 nm), and thus appears as the best solvent for light‐scattering measurements.
Quick determination of dielectric anisotropy of paper sheets by means of microwaves
Authors: Osaki Shigeyoshi
Published: April 2003

This paper deals with a new type of method for determining the complex dielectric constant at microwave frequencies in about 30 s. This method determines the dielectric anisotropy and refractive index for optically opaque paper sheets. The dielectric anisotropy ascribable to the local motions of cellulose molecules is supported by electron microscopic observations and mechanical anisotropy. The angular dependence of the complex dielectric constant gives the degree of molecular orientation and the distribution of cellulose molecules in paper sheets. The direction of the average orientation of molecular chains can be inferred from the anisotropic data. It is also suggested that the cellulose molecules should be oriented on an average in the direction of long axis of pulp fibers. The accumulation of data for complex dielectric constant and refractive index at microwave frequencies gives an important chart for manufacturing the functional paper corresponding to needs.
Measurements of residence time distribution for the peroxide degradation of polypropylene in a single‐screw plasticating extruder
Authors: Tzoganakis C. , Tang Y. , Vlachopoulos J. , Hamielec A. E.
Published: April 2003

Measurements of the residence time distribution (RTD) in a single‐screw plasticating extruder were carried out during experimental studies of the peroxide‐initiated controlled chemical degradation of polypropylene (PP). A radioactive tracer method was employed, and the effect of screw speed, temperature, and reaction on the RTD was examined. An increase of the peroxide concentration resulted in a broader distribution whereas an increase of the extrusion temperature was found to result in a narrower distribution. Use of low screw speeds simply increased the time delay through the extruder without affecting considerably the breadth of distribution. Results obtained from the present experiments were compared with several theoretical models.
Influence of coupling agents and treatments on the mechanical properties of cellulose fiber–polystyrene composites
Authors: Maldas D. , Kokta B. V. , Daneault C.
Published: April 2003

Wood fibers of aspen in the form of chemithermomechanical pulp (CTMP) and Tembec 6816 have been used as reinforcing fillers in different varieties of polystyrene. The tensile strength, elongation, and energy at maximum point, as well as tensile modulus at 0.1% strain is reported. Also revealed is the optimum condition of compression molding. The influence of different coupling agents, such as poly[methylene(polyphenyl isocyanate)], silanes (A‐172, A‐174, A‐1100), and grating on the mechanical properties of composites is discussed. The extent of increase in mechanical properties depends on the weight percentage of fibers, the concentration of coupling agents, and the grafting level (add‐on %). Coating followed by an isocyanate treatment appears to be the best treatment. In addition, the isocyanate treatment and grafting are superior to the silane treatment. Experimental results are explained on the basis of possible interactions among cellulose fiber‐coupling agent‐polymer in the interfacial area.
Polymerization reactor: The influence of “gel effect” in batch and continuous solution polymerization of methyl methacrylate
Authors: Maschio G. , Moutier C.
Published: April 2003

This article describes the influence of gel effect in the free radical polymerization of methyl methacrylate. A mathematical model has been developed which tries to predict the performance of batch and continuous polymerization reactors under dynamic and steady‐state conditions. The influence of diffusion phenomena on the process kinetics (gel effect) is very important. The autoacceleration in the polymerization rate of the batch reactor and the mulitple steady state for the continuous stirred tank reactor (CSTR) are connected with the attainment of critical conditions in the system. Such a model is useful for the design of the reactor and the choice of the control system.
Photodegradation of rigid PVC formulations. I. Wavelength sensitivity to light‐induced yellowing by monochromatic light
Authors: Andrady Anthony L. , Torikai Ayako , Fueki Kenji
Published: April 2003

Light‐induced yellowing of extruded rigid poly(vinyl chloride) formulations containing 0, 2.5, and 5 phr of titanium dioxide under exposure to monochromatic light was studied. Both photoyellowing and photobleaching were observed as wavelength‐dependent phenomena in the range of 280–500 nm. Action spectra for yellowing of the different compounds were similar. In the case of the formulation with no titanium dioxide, significant color changes were observed on the back surface of the sample, indicating transmission of the longer wavelength light through the 1‐mm thickness of the sample.
Kinetics and mechanism of emulsion copolymerization. IV. Kinetic modeling of emulsion copolymerization of styrene and methyl methacrylate
Authors: Nomura Mamoru , Horie Ichiro , Kubo Masayuki , Fujita Kazumi
Published: April 2003

Based on the micellar nucleation theory, a mathematical kinetic model for an unseeded emulsion copolymerization system is developed, where the radicals with and without electric charge are discriminated from each other in view of the role in the particle nucleation process. In order to demonstrate the validity and utility of this kinetic model, the experiments of the unseeded emulsion copolymerization of styrene (ST) and methyl methacrylate (MMA) are carried out varying the initial initiator (potassium persulfate) and emulsifier (sodium lauryl sulfate) concentrations and the monomer composition in the initial monomer feed, and various kinetic features observed are compared with the model predictions. It is concluded from this comparison that in this system, almost all the polymer particles are generated by the charged radicals stemming from the initiator, and further that this mathematical kinetic model can provide a satisfactory explanation of the various kinetic features observed.
A facile method for the study of slow physical and chemical processes in polymeric systems
Authors: Lundgren Roger , Sandén Roland , Albertsson Ann‐Christine
Published: April 2003

A method is described for continuously following a long‐duration process in a complex polymeric system by isothermal calorimetry. Computerized models for slow physical or chemical processes have been applied to calorimetric runs under different conditions and these have given information in the form of thermodynamic and kinetic data. The method also gives a means of determining the relationship between molecular weight and functionality for one of the polymers used, the order of reaction, and the degree of conversion before the start of the measurements. An example is given of a kinetic study of the reaction of hydroxyl‐terminated polybutadiene with two different diisocyanates. The temperature dependence of the formation of urethanes, the rate constants, and the degree of conversion before the start of the measurements were determined as well as the heat of reaction for the formation of urethanes using hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) as curing agents. The results have been compared with other kinetic studies of these systems.
Influence of hydrostatic pressure on the electrical properties of unvulcanized FEF‐loaded SBR
Authors: Nasr G. M. , Amin M. , Osman H. M. , Badawy M. M.
Published: April 2003

Styrene butadience rubber (SBR‐1502) loaded with different concentrations of FEF carbon black was tested to find out the effect of pressure on its electrical properties during vulcanization. Using the thermodynamically calculated values of the pressure coefficient (K), the thermoelastic coefficient (L = ∂T/∂P) was also estimated and compared with that obtained by other workers. The thermoelastic coefficient was found to be strongly dependent on the carbon black concentration.
A generalized correlation for the viscosity of dextrans in aqueous solutions as a function of temperature, concentration, and molecular weight at low shear rates
Authors: Carrasco F. , Chornet E. , Overend R. P. , Costa J.
Published: April 2003

An expression relating the viscosity of dextran solutions to polymer concentration (c), molecular weight (M), and temperature (T) has been derived from experimental data in the following ranges: 5 < c < 25% (wt/wt), 298.2 < T < 363.2 K, and 71,500 < M < 531,000 g/mol. The experimental work was based on capillary viscosimeters. Thermodynamic data (entropy and energy of activation for the viscous flow of a Newtonian fluid) are also presented as a function of polymer concentration for the three molecular weights studied. This thermodynamic analysis suggests that dextrans in aqueous solutions behave as flexible polymers. Application of our expression to existing viscosity data for ethylene/vinylacetate copolymers in paraffin has resulted in improved goodness of fit with respect to established correlations.
Effects of acceptor level on chemically synthesized polypyrrole‐halogen complexes
Authors: Neoh K. G. , Kang E. T. , Tan T. C.
Published: April 2003

Electrically conductive polypyrrole (PPY)‐halogen complexes have been synthesized by simultaneous chemical polymerization and oxidation of pyrrole. The ratio of pyrrole monomer to halogen (chlorine, bromine, or iodine) used in the synthesis was varied and the physicochemical and electrical properties of the resulting complexes were studied in detail. With all three halogens, the yield of the complex is affected by the initial amount of halogen used, with the properties of the polypyrrole‐bromine complex showing the strongest dependence on the acceptor level. For this complex, both the percentage of bromine incorporated and the ratio of covalent to ionic bromide increase upon increasing the initial bromine concentration, while the electrical conductivity shows a maximum. Experimental evidence suggests that some halogen substitution at the pyrrole ring must have occurred in the PPY–Br2 and PPY–Cl2 complexes, but not in the PPY–I2 complex.
Gelatin with hydrophilic/hydrophobic grafts and glutaraldehyde crosslinks
Authors: Chatterji Prabha R.
Published: April 2003

Acrylic monomers were graft copolymerized onto gelatin chains using potassium persulfate in aqueous medium. The graft copolymers were then treated with glutaraldehyde to establish crosslinks between gelatin macromolecules. This yielded a rigid water insoluble protein network sporting grafted chains at random. The chemistry of the acrylic monomer decided the hydrophilic/hydrophobic properties of the ultimate product. This paper describes the preparation and properties of such grafted, crosslinked gelatins.
Simplified hydrolysis of cellulose and substituted cellulose: Observations on trifluoroacetic acid hydrolyses
Authors: Rowland Stanley P. , Howley Phyllis S.
Published: April 2003

Hydrolyses of selected soluble polysaccharides (e.g., polyoses) and disordered and crystalline celluloses, each bearing 2‐diethylaminoethyl (DEAE) substituents at low degree of substitution (DS < 0.05) were explored in 100% and 2N trifluoroacetic acid (TFA). Analyses were evaluated relative to hydrolysis with 72% sulfuric acid. DEAE–polyoses hydrolyzed readily in 100% and 2 N TFA during extended reaction periods with complete liberation of DEAE–glucoses. Hydrolyses of cellulose and DEAE–celluloses in 100% TFA were critically dependent upon cautious incremental dilution of the TFA during stepwise reaction to avoid precipitation of incompletely hydrolyzed products. DEAE–celluloses were partially solubilized and hydrolyzed in heterogeneous reaction in 2N TFA at 121°C. Complete liberation of DEAE‐glucoses in the solubilized components was achieved after supplementary hydrolysis at 121°C. In all hydrolyses, including those with 72% sulfuric acid, extended hydrolyses were essential for complete liberation of the 2‐O‐ and 6‐O‐DEAE–glucoses. Under optimum conditions, results of hydrolyses in 100% TFA were comparable to those in 72% sulfuric acid. Ease of release of DEAE‐glucopyranoses in hydrolyses of DEAE‐cellulose in 2N TFA was in the same order (3‐O‐ > 6‐O‐> 2‐O‐) as in homogeneous hydrolyses in sulfuric acid and in 100% TFA. Differences in release of isomeric DEAE–glucoses were greater in the heterogenous system. Degradation of glucose and DEAE–glucopyranoses occurred in extended periods of reaction in all acidic media. Rates of degradation of glucose and DEAE–glucopyranoses in dilute acid at 100°C were similar for glucose and 6‐O‐DEAE–glucose. The rates were about half as fast for 3‐O‐DEAE–glucose and an order of magnitude lower for 2‐O‐DEAE–glucose.
Modification of atactic polypropylene to prepare emulsions by oxidation in melt
Authors: Yaykin Özden , Savaşçi Ö. Tunç , Baysal Bahatti̇n M.
Published: April 2003

Oxidation of atactic polypropylene (APP) obtained as by product from polypropylene production is studied in melt to obtain polymers which are easily emulsified by commercial emulsifiers. The experiments are done using a sitrred, jacketed glass reactor and the relevant heating, air‐feeding, and sampling attachments. Oxidation is followed by the change of carbonyl absorbance, iodine number, acid number, molecular weight, and melt flow index (MFI) by time. The relevant tests are done by infrared (IR) spectroscopy and gel permeation chromatography (GPC) and standard tests with minor modifications are applied. It is found that as temperature, air flow rate, and mixing speed are increased, higher oxidation rates are obtained. It is also found that initiator types and concentrations used are not as effective as the above parameters. By oxidation as molecular weight reduces, molecular weight distribution narrows. Correlation between MFI, iodine number, and molecular weight of the oxidized APP is also made for easy follow‐up of oxidations. In addition, it is found that for easy and stable emulsions, APP must be modified by oxidation to iodine number and MFI higher than 30 mg/g and 3.5, respectively.
Sorption of organic compounds on strong basic macroporous anion exchangers
Authors: Chitanu Gabriela , Luca Cornelia , Avram Ecaterina , Airinei A. , Petrariu I. , Carpov A.
Published: April 2003

The behavior of various strong basic type II macroporous anion exchangers against the sorption of some organic acid alkaline salts as follows: natrium benzoate, natrium benzenesulfonate, potassium α‐naphthylacetate, natrium β‐naphthalenesulfonate, and natrium anthraquinone‐2‐sulfonate was established. The values of the sorption capacities depend on the morphology of anion exchanger network, the type and the size of organic anion, as well as the type of anion exchanger.
Determination of diffusion coefficient of oxygen into polymers by using electron spin resonance spectroscopy. I. Poly(methyl methacrylate)
Authors: Kaptan Yilmaz , Pekcan Önder , Arca Emin , Güven Olgun
Published: April 2003

A simple technique has been proposed for the measurement of the diffusion coefficient of oxygen into polymeric spheres. The technique is based on the scavenging of radicals produced by high energy radiation by oxygen. The diffusion coefficient of oxygen determined for poly(methyl methacrylate) has shown an inverse dependency on the dose received. Diffusion coefficient determined for low doses (D = 3.4 × 10−8 cm2/s) as well as that determined after extrapolation to zero dose (D0 = 3.7 × 10−8 cm2/s) are in excellent agreement with the values reported in the literature.
PVT scaling parameters for polymer melts
Authors: Hartmann Bruce , Simha Robert , Berger Alan E.
Published: April 2003

Scaling parameters for two PVT equations of state are evaluated for 11 polymer melt systems using a nonlinear least square fitting algorithm that analyzes all of the experimental data simultaneously. Two different criteria are considered in this evaluation. In the first method, the fitting criterion is the difference between the calculated and experimental volume. In the second method, the criterion is the difference between the calculated and experimental pressure. In both cases, the differences between the scaling parameters obtained using the simultaneous fit procedure and those obtained using the earlier consecutive fit procedure are a few percent, which can have a significant effect in some calculations. In addition to being a more consistent method of evaluating scaling parameters, the simultaneous fit procedure leads to much better agreement between calculated and experimental values, in some cases by a factor of 2.
Cure kinetics of neat and graphite‐fiber‐reinforced epoxy formulations
Authors: Mijović Jovan , Wang H. T.
Published: April 2003

An investigation was carried out into the cure kinetics of neat and graphite fiber‐reinforced epoxy formulation, composed of tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) resin and diaminodiphenyl sulfone (DDS) curing agent. Two experimental techniques were employed: isothermal differential scanning calorimetry (IDSC) and dynamic differential scanning calorimetry (DDSC). An autocatalytic mechanism with the overall reaction rate order of 2 was found to describe adequately the cure kinetics, of the neat resin and the composite. All kinetic parameters, including reaction rate constants, activation energies and preexponential factors, were calculated and reported. The presence of graphite fibers in the composite had only a very small initial effect on the kinetics of cure.
Self‐assembly of octadecyltrichlorosilane films on mica
Authors: Carson George , Granick Steve
Published: April 2003

Self‐assembled films of Octadecyltrichlorosilane (OTS) have been deposited on freshly cleaved mica. A combination of argon plasma pretreatment, long adsorption times in solution, and a posttreatment at a moderate temperature (60°C) were required to form homogeneous OTS layers exhibiting good adherence to the mica. This process is more complex than the procedure required to form similar layers on glass. Advancing contact angles of water droplets ranged from 113 to 116°, with receding angles of 107 to 110°.