bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermogravimetric/mass spectrometric characterization of the thermal decomposition of (4‐O‐methyl‐D‐glucurono)‐D‐xylan
Authors: Šimkovic Ivan , Varhegyi Gabor , Antal Michael J. , Ebringerová Anna , Szekely Tamas , Szabo Piroska
Published: April 2003

A thermogravimetric/mass spectrometric (TG/MS) system was used to characterize the thermolysis reactions of (4‐O‐methyl‐D‐glucurono)‐D‐xylan. The mass spectrometric peaks, measured as function of time, were attributed to water, methanol, carbon monoxide, carbon dioxide, formaldehyde, formic acid, acetic acid, acetone, acrolein, 2‐furaldehyde, and 3‐hydroxy‐2‐penteno‐1,5‐lactone. The time derivative of the thermogravimetric curve (DTG) consisted of two partially overlapping peaks, indicating a multistep mechanism. The mass spectrometric intensities of the peaks assigned to methanol and 2‐furaldehyde coincided with the first DTG peak, suggesting that the first DTG peak represents both dehydration and fragmentation pathways. Methanol, water, formyl group, and carbon dioxide contributed to both of the DTG peaks. This indicates that the dehydration, decarboxylation, and decarbonylation took place in two steps. The compounds observed only in the second DTG peak and later (acetone, formic acid, formaldehyde, acrolein, acetic acid, and 3‐hydroxy‐2‐penteno‐1,5‐lactone) are probably products of reactions which occur after the collapse of the original polysaccharide structure.
Micromechanical properties of polyether block amide copolymers
Authors: Alberola Nicole
Published: April 2003

A series of polyether block amide copolymers based on poly(tetramethylene oxide) of molecular weight 1000 or 2000 and polyamide 12 of molecular weight between 600 and 4000 with varying PE/PA weight ratio (from 80 to 20%) were studied by using dynamic mechanical spectroscopy and differential scanning calorimetry. Dynamic mechanical experiments showed three main relaxation peaks related to, the subglass transition of the soft segments, the glass transition of the soft segments, and the glass transition of the hard segments. A quench, carried out on a 70% PA copolymer from 110 to 15°C, leads to a decrease in the storage modulus. This result should be related to the destruction of physical ties.
Morphology of composite film prepared by polymerizing styrene in poly(vinyl chloride) film
Authors: Mizutani Yukio , Nishimura Toshihiko , Nishimura Masakatsu
Published: April 2003

Styrene and the styrene‐additive mixtures (kerosene, dioxane, ethylene dichloride, or dioctylphthalate) were soaked into a poly(vinylchloride) film and then styrene was polymerized. Subsequently, poly(styrene) was extracted with CCl4 and the microporous membrane was obtained, of which the morphology was studied. It is elucidated that the additives affect the morphology of the resultant composite films.
Processing–property interactions in poly(vinylidene fluoride). I. An analysis of melt stress history in an extensional flow geometry
Authors: Khomami B. , McHugh A. J.
Published: April 2003

A numerical and experimental analysis of the melt flow history of poly(vinylidene fluoride), PVF2, in an extensional flow, film‐processing geometry is presented. Numerical computations were carried out for both Newtonian and power law flow in an impinging channels die using a finite‐element technique. Computations demonstrate that a strong extensional flow exists in the region from the stream impingement point to a distance about 0.75 D downstream where D is the channel height at the impingement point. Measurements of the stress fields using the technique of flow birefringence showed that in consequence of the changing flow kinematics from the stream impingement region to the downstream converging channels region, both the isochromatic and isoclinic patterns exhibit a pronounced axial positional dependence. Excellent qualitative and quantitative agreement was found between measured and calculated shear stress fields. However, large differences were exhibited between calculated and measured normal stress differences along the symmetry axis of flow. Results to be presented in a companion paper (Part II) demonstrate that the strong extensional flow which occurs in this geometry is sufficient to produce oriented, row‐nucleated structures in the extruded PVF2 films.
The role of hindered piperidine (HALS) compounds for the stabilization of polypropylene against oxidation reactions caused by ozone and oxidative products formed during photolysis of ozone
Authors: Lucki J. , Rabek J. F. , Rånby B. , Watanabe Y.
Published: April 2003

The role of hindered piperidine (HALS) photostabilizers for the photostabilization of polypropylene films against oxidative reactions caused by ozone and oxidative species formed during photolysis of ozone under UV irradiation (i.e., atomic oxygen and singlet oxygen) has been investigated and discussed. It has been found that ozonization and/or photoozonization of 2,2,6,6‐tetramethyl‐piperidine (I) and piperidinoxy radical (2,2,6,6‐tetramethylpiperidino‐1‐oxy) (II) gives a high yield (91–98%) 2,6‐dimethyl‐2‐hydroxy‐6‐nitro‐heptane. Ozonization and/or photoozonization of HALS probably occur by a similar mechanism as reported for (I) and (II). HALS photostabilizer reacts with ozone and/or photolysis products of ozone (atomic oxygen and/or singlet oxygen) and loses its function in the photostabilization process. For that reason protection of polypropylene against photooxidative degradation and photoozonization is of great commercial importance.
Characterization of rubber particle size distribution of high‐impact polystyrene using an image analysis method
Authors: Hall R. A.
Published: April 2003

Accurate characterization of high‐impact polystyrene (HIPS) rubber particle size distribution has been achieved using an automatic image analysis system. The new method involves preparation of a microscope slide consisting of a dilute suspension of HIPS particles in a polymer matrix. Images of silhouetted rubber particles of true diameter are obtained using an image processor and particle size calculations can be made with a minimum of editing of the binary image. The new method provides measurement of true rubber particle diameters because the particles in the prepared slide are not swollen by any solvent.
Stirring‐induced solution crystallization of ultra high molecular weight polyamide 6
Authors: Doppert H. L. , Van Dijk J. G.
Published: April 2003

Unstable solutions of ultrahigh molecular weight polyamide 6 have been prepared by adding a nonsolvent to the polymer solution. Crystallization of the polyamide from such a solution proceeds very slowly. It has been found, however, that vigorous stirring of the unstable solutions induces rapid fibrous crystallization of the polymer. The fiber mat consists of irregularly shaped fibers. A low temperature and a high stirring rate are among the conditions necessary to obtain a high yield of fibrous material. The fibers formed upon stirring have a higher molecular weight than the polyamide 6 molecules which remain in the solution. The melting point of the fibers depends on the speed of the paddle stirrer. The differential scanning calorimetry (DSC) thermogram reveals higher melting temperatures of the fibrous material if higher stirring rates have been applied.
The equilibrium water content of some thermoplastic hydroxyalkyl methacrylate polymers
Authors: Stevenson W. T. K. , Sefton M. V.
Published: April 2003

The equilibrium water content (EWC) of thermoplastic 2‐hydroxypropyl methacrylate and 2‐hydroxyethyl methacrylate homopolymers from technical grade monomer and of copolymers of the latter with methyl methacrylate has been measured in distilled water and in phosphate‐buffered saline (PBS). In distilled water, as expected, EWCs increased monotonically with the proportion of hydrophilic monomer in the polymer and showed only a small dependence on molecular weight. In contrast, the degree of swelling (and in some cases dissolution) and “freezable” water content of polymers in PBS were shown to be anomalously high and to be a consequence of ionization at pH 7.4 of methacrylic acid incorporated into the polymer in small quantity (< 1 mol %) as an impurity. Initial studies indicated a strong relationship between copolymer molecular weight and small molecule permeability in distilled water.
Recovery of uranium from seawater. VI. Uranium adsorption ability and stability of macroporous chelating resin containing amidoxime groups prepared by the simultaneous use of divinylbenzene and ethyleneglycol dimethacrylate as crosslinking reagent
Authors: Nakayama Morio , Uemura Keiji , Nonaka Takamasa , Egawa Hiroaki
Published: April 2003

Macroporous chelating resins (RNH‐DVB‐1G) containing amidoxime groups with various degrees of crosslinking were synthesized by varying the amount of divinylbenzene (DVB) and ethyleneglycol dimethacrylate (1G). It was confirmed that the content of amidoxime group decreased with an increase in the degree of crosslinking. On the other hand, the amount of amidoxime group hydrolyzed by acid treatment showed a tendency to decrease with an increase in degree of crosslinking. From the measurement of specific surface area and pore size distribution, it was found that the macropore of RNH‐DVB‐1G with the same degree of crosslinking was remarkably affected by the composition of crosslinking reagent (DVB and 1G). The RNH‐DVB‐1G prepared in the present work were applied to the recovery of uranium from seawater. It was found that the uranium adsorption ability of RNH‐DVB‐1G with the same degree of crosslinking was remarkably affected by the proportion of DVB and 1G, although each RNH‐DVB‐1G had the same content of amidoxime group. In the case of RNH‐DVB‐1G prepared with 25 mol% of crosslinking reagent, the resin prepared with 10 mol% of DVB and 15 mol% of 1G showed the high adsorption ability for uranium in seawater. These results indicate that the simultaneous use of DVB and 1G contributes to the formation of effective macropore and micropore for recovery of uranium from seawater and the increase of chemical and physical stability.
Surface‐modified polysulfone hollow fibers
Authors: Higuchi Akon , Iwata Noboru , Tsubaki Masayuki , Nakagawa Tsutomu
Published: April 2003

Controlled reactions on the inner side, outer side, and both sides of the surfaces of polysulfone ultrafiltration hollow fibers with propane sultone and Friedel‐Crafts catalysts were developed. EPMA measurements and MTR spectra for the chemically modified fibers suggested existence of CH2CH2CH2SO3− segments on the modified surfaces. The modified fibers were found to have smaller molecular weight cut‐off than nonmodified fibers, and the fibers modified on the internal surfaces gave better rejection of polyethylene glycol 6000 than those modified on the external surfaces, although the fibers that reacted with solution of the propane sultone and SnCl4 at 70°C and 80°C showed negative rejection of the polyethylene gylcol. Absorption of polyethylene glycol on the modified fibers is estimated to be less than the nonmodified fibers from the flux ratios of aqueous polyethylene glycol solution to pure water. This effect is attributed to the heparinlike active group of modified segments.
Diffusional aspects for the chlorination of the sulfonated poly(styrene‐co‐divinylbenzene) resin beads
Authors: Ihm Son‐Ki , Ahn Jou‐Hyeon , Widdecke Hartmut , Struß Klaus , Klein Joachim
Published: April 2003

The diffusional process in the chlorination of sulfonated poly(styrene‐co‐divinylbenzene) bead was investigated through a general model as well as direct observation with electron microprobe. Two modes of diffusion, namely the pore diffusion and gelular permeation, were analyzed by two system parameters through a two‐phase model. The effective pore and gelular diffusivities estimated from the x‐ray energy‐dispersive analysis data on the chlorine profile and the conversion suggest that, even for the same crosslinking, the diffusivity of chlorine in the gelular bead is larger by several orders of magnitude than that for the gelular microparticle in the macroreticular bead.
Miscibility in poly‐p‐phenylene terephthalamide/nylon 6 and nylon 66 molecular composites
Authors: Kyu Thein , Chen Tsuey Ing , Park Ho‐Sung , White James L.
Published: April 2003

Miscibility and crystallization of poly‐p‐phenylene terephthalamide (PPTA)/nylon 6 and nylon 66 composites prepared by coagulation of isotropic ternary sulfuric acid solutions were studied. The apparent crystallinity of nylon 6 and nylon 66 in molecular composites was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The solvation of nylon 6 crystals in PPTA matrix was observed when the PPTA content exceeds 70 wt%. Cross‐hydrogen bonding seems to be responsible for the virtual disappearance of nylon 6 crystals. Specific interaction between PPTA and nylon 6 macromolecules and phase separation during thermal treatment has been discussed.
Distribution of MBS emulsion particles in immiscible polystyrene/SAN blends
Authors: Fowler M. E. , Keskkula H. , Paul D. R.
Published: April 2003

The effect of mixing technique and sequence on the distribution of methacrylated‐butadienestyrene (MBS) emulsion particles in immiscible blends of polystyrene (PS) and a styrene/acrylonitrile copolymer (SAN) was examined using transmission electron microscopy. The shell of the emulsion particle is essentially poly(methyl methacrylate) (PMMA), which is miscible with SAN but immiscible with PS. In simple thermodynamic terms, the MBS particle should have an affinity for SAN over PS. It was found, however, that the sequence of mixing had a strong influence on the location of the MBS particles. If the PS‐SAN interface is established before the addition of the MBS particles, the MBS particles are located exclusively in the SAN phase. If the MBS particles are present at the time the PS‐SAN interface is formed, then the particles line up at the interface.
Thermal degradation of cellulose‐containing composites during processing
Authors: Sapieha S. , Pupo J. F. , Schreiber H. P.
Published: April 2003

The strength properties of composites made of untreated cellulose fibers and linear low density polyethylene were investigated as a function of processing parameters. Studies have shown that the strength properties of composites increase with processing time and temperature. The increase in strength is accompanied by the appearance of new infrared absorption bands at 1718 and 1735 cm−1. A linear relationship between the absorbance and yield strength of composites indicates that oxidation, possibly directly at interfaces, takes place and enhances adhesion between the cellulose and polyethylene.
Morphology of HDPE/(PEC/PS) blends modified with SEBS copolymers
Authors: Schwarz M. C. , Barlow J. W. , Paul D. R.
Published: April 2003

In this study, immiscible blends of HDPE and an amorphous glassy polymer were compatibilized with styrene‐hydrogenated butadiene block copolymers. The glassy phase consisted of either pure PS or a miscible blend of PS and polyether copolymer (PEC); PEC is similar to poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). The morphology of these two‐phase mixtures depended on physical characteristics of the components and the method of fabrication. Suitable copolymers increased the degree of dispersion and minimized heterogeneities resulting from the inherent incompatibility of the individual phases. Further reduction in the phase size and increased adhesion between the components of modified blends were achieved by increasing the composition of PEC in the glassy phase. It was concluded that favorable exothermic mixing between PEC and PS endblocks of the copolymers provided an additional driving force for compatibilization. Results from dynamic mechanical thermal analysis suggests that penetration by the copolymers into the homopolymer phases is not complete.
Crosslinking of poly(vinyl chloride) with metal oxides, sulfur, and organo sulfur compounds
Authors: Běhal Miroslav , Ducháček Vratislav
Published: April 2003

The crosslinking of poly(vinyl chloride) in the presence of zinc oxide, magnesium oxide, ethylenethiourea (ETU), tetramethylthiuramdisulfide (TMTD), and sulfur at 160 and 180°C has been studied. The effects of ETU and sulfur on the crosslinking of PVC in the presence of TMTD have been individually studied. It has been found that zinc dimethyldivhiocarbamate (ZnDMDC) is the actual crosslinking agent and heat stabilizer of PVC, formed in the cured polymer mix.
Dual function curative for NR
Authors: Datta Rabindra Nath
Published: April 2003

Two derivatives of thiocarbamyl sulfenamide containing thiocyclohexyl moiety on sulfenamide nitrogen atom have been synthesized and evaluated for their action as accelerator cum retarder in NR gum stocks.
Influence of inertia and viscoelasticity in entry flows through an abrupt annular contraction
Authors: Mitsoulis E.
Published: April 2003

A numerical simulation of entry flows in an annular die has been undertaken for Newtonian and power‐law fluids as well as viscoelastic fluids that exhibit normal stresses in shear flow. Experimentally measured normal stress and viscosity data are included in a simple rheological model. The influence of inertia and viscoelasticity are examined separately as functions of the Reynolds (Re) and Weissenberg (Ws) numbers. It is found that inertia decreases the size of the corner vortices in the reservoir corners which tend to increase rapidly with elasticity level in the absence of inertia. The combined effect of inertia and elastic forces is to first increase the vortex size followed by a decrease at higher Re numbers. The numberical simulations are in qualitative agreement with experimental studies available in the literature.
Synthesis, characterization, and curing of o‐and p‐chlorophenol‐furfural resins
Authors: Arora Pravin B. , Patel Vithal S. , Patel Shanti R.
Published: April 2003

Polycondensation of furfural, respectively, with o‐ and p‐chlorophenols has been carried out under various reaction conditions. All the resin samples have been characterized by spectral studies, viscometric measurement and by the estimation of the number‐average molecular weight. Thermogravimetric analysis (TGA) of selected resin samples has been carried out. The kinetics of curing reaction of selected resin samples has been investigated by differential scanning calorimetry (DSC). The properties of the glass laminates prepared using each of the two types of resins showed that the latter are much less suitable than phenol‐furfural resin as matrices for the fabrication of laminates.
Effect of vulcanization temperature on the technical properties of NR, SBR, and BR
Authors: Kurian Thomas , George K. E.
Published: April 2003

Compounds of natural rubber, styrene‐butadiene rubber, and butadiene rubber are vulcanized at different temperatures and the crosslink density and physical properties of the vulcanizates are compared. It is found that for each compound there is an optimum vulcanization temperature which results in the best compromise of properties for specific applications.
Modification of solute dissolution rate by coprecipitation with certain acrylate–methacrylate copolymers
Authors: Okor R. S.
Published: April 2003

Coprecipitates containing certain cationic acrylate‐methacrylate copolymers and paracetamol (polar solute) have been prepared by evaporating to dryness an ethanolic solution of both components; their friability (i.e., degree of crumbling to dust under impact stress) and dissolution characteristics were evaluated. Friability decreased with increase in the polymer content of the coprecipitates; this effect was more marked in the polymer system containing the higher cation content. Dissolution rates also decreased with increase in polymer content, but this time the effect was slightly more pronounced in the polymer system with the lower cation content. It is thought that the polymer cationic groups interacted with polar groups of the solute to increase coherence of the particle; on the other hand, the cationic groups confer hydrophilic character and at certain concentrations, > 5% they may promote swelling in aqueous fluids and hence weaken bonding forces in the solute‐polymer particle with a tendency to reduce the polymer effect on dissolution rate.
Crystallinity changes during PVC processing
Authors: Obande O. P. , Gilbert M.
Published: April 2003

Thermal analysis, solvent sorption, density measurement, and X‐ray diffraction techniques were used to investigate structural changes in a variety of PVC compounds which were extruded or compression‐molded at temperatures in the range 150–220°C. In all cases processing at lower temperatures in this range resulted in a disappearance of primary crystallinity and a concomitant development of secondary crystallinity, of lower order. In many cases processing above 190–200°C caused a small increase in crystallinity. It is believed that this is more ordered secondary crystallinity, which is therefore detectable by X‐ray diffraction and also capable of influencing density and solvent sorption behavior. The observed structural behavior depends on shear as well as temperature. Primary crystallinity is higher in compression moldings, which have experienced lower shear levels, and the increase in crystallinity at higher temperatures is also greater. Equilibrium solvent sorption depends on the presence of primary and ordered secondary crystallinity. Diffusion is, however, unaffected as it occurs through amorphous and disordered crystalline regions only.
Radical copolymerization of ethylene and 2‐phenyl‐3‐vinyloxirane
Authors: Endo Takeshi , Suga Katsufumi , Orikasa Yuichi , Kojima Shinji
Published: April 2003

The radical copolymerization of ethylene and 2‐phenyl‐3‐vinyloxirane was carried out under high pressure to obtain the corresponding copolymers. The structure of the obtained copolymers was discussed by the data of infrared and nuclear magnetic resonance.
Mean field calculations of the dynamic mechanical properties of two‐phase elastomer blends: Included particles in a matrix phase
Authors: Mazich K. A. , Plummer H. K. , Samus M. A. , Killgoar P. C.
Published: April 2003

Mean field theories developed by Kerner and van der Poel were applied to several binary elastomer blends. Calculations were compared with experimental small strain dynamic mechanical properties of the blends. Although the blends exhibit a wide range of detailed structures, the theories were able to model blenas with well‐defined included particles embedded in a matrix phase. Blends with a continuous morphology were not properly modeled with the Kerner or van der Poel theories.
Determination of the density dispersion of suspension poly(vinyl chloride) by the method of kinetic density curves
Authors: Ševčík Stanislav , Kolínský Miloslav
Published: April 2003

A new method has been developed for the evaluation and comparison of quality of various types of poly(vinyl chloride) (PVC) powder with respect to their density homogeneity. The method consists in the determination of the dependence of the volume of a specifically heavier fraction of PVC powder on the density or concentration of testing aqueous NaNO3 solutions after a chosen time of contact between the powder and the testing solutions. Compared with the method of determination of density distribution using densitometric titration, the new method simplifies and extends possibilities of comparison of polymers and improves the density characterization.
Accurate molecular weight distribution of polymers using thermal field‐flow fractionation with deconvolution to remove system dispersion
Authors: Schimpf Martin E. , Williams P. Stephen , Giddings J. Calvin
Published: April 2003

Thermal field‐flow fractionation (ThFFF) is an elution process that separates polymeric materials by molecular weight. Elution profiles thus provide approximations to the molecular weight distributions of polymers. The accuracy of such approximate distributions is expected to be improved by accounting for the effect on the elution profile of band‐broadening processes in the FFF system. Fortunately this intrinsic band broadening, referred to as system dispersion, is theoretically well‐defined in ThFFF. In this article we present an algorithm that corrects ThFFF elution profiles by removing system dispersion. The program is applied to ThFFF fractograms of standard polymers having both narrow and broad molecular weight distributions. The increased accuracy obtained by accounting for system dispersion is demonstrated. For the narrow standard, deconvolution shows that the polydispersity (weight/number‐average mol. wt.) is only 1.004. For the broad standard, NBS 706, the molecular weight distribution and parameters obtained agree well with previously published results. Application to a simulated fractogram resulting from mixing five narrow standards helps define the conditions under which accurate molecular weight information can be recovered.
A scanning electron microscopic study on the morphology of beech wood (Fagus crenata) copolymerized with acrolein using the xanthate method of grafting
Authors: Hirabayashi Yasuhiko
Published: April 2003

Powdered beech wood (Fagus crenata) copolymerized with acrolein by using the xanthate method of grafting is examined in a scanning electron microscope. Homopolymer was observed as spherical‐shaped particules deposited on the surface of cell walls. Coral‐ and spongelike shaped graft polyacrolein made its appearance after the removal of the homopolymer by the extraction with the pyridine–water mixture. Wrinkles which were observed in the noncopolymerized sample were interpreted as a result of the formation of voids by dissolving the oxidatively degraded cell wall materials in the pyridine–water and the subsequent collapse of the voids and shrinkage of the cell walls on drying. The wrinkle formation was minimized in the case of the copolymerized samples because of the restriction of the shrinkage of the cell wall by the presence of graft polymer in the cell wall.
Mixing study of L shape mixheads in reaction injection molding
Authors: Molnar John A. , Lee L. James
Published: April 2003

The effect of mixhead geometry on the impingement mixing in the reaction injection molding (RIM) process is largely unknown. In this study, high speed photographs are used to show the flow patterns produced by L shape mixheads. The mixing quality of the conventional I and various L shape mixheads is quantified by an emulsion test. The adiabatic temperature rise of a polyurethane/urea system is followed to further characterize the mixing produced by I and L shape mixheads. The results show that L shape mixheads give a better mixing quality than the I shape mixhead, especially at lower Reynolds numbers. In addition, the L shape mixheads can provide a more laminar flow from the mixhead, which is important for mold filling.
CO gas sensor devices plasma‐polymerized from tetramethyltin
Authors: Inagaki N. , Tasaka S. , Mase T.
Published: April 2003

Thin films plasma‐polymerized from tetramethyltin was applied for CO gas sensor device. The films formed from tetramethyltin contains alkyl chains with organic tin moieties, and pyrolysis of them at 350–500°C yields carbonized films with SnO2 moieties. The electrical resistance for the films pyrolized at 350–500°C decreases in exposing to CO gas. The sensitivity, the ratio of the electrical resistance between in air and in CO atmosphere, is enhanced by catalytic actions of palladium chloride, specially in operation at low temperatures below 50°C. The gas sensitivity between CO and other gases such as ethanol, methane, and propane gases is good. The possible determination of CO gas concentration by the sensor device is in ranges from 10 to 1000 ppm.
Solubility parameters of amine‐crosslinked aromatic epoxies
Authors: Bellenger V. , Morel E. , Verdu J.
Published: April 2003

For six epoxide–amine systems, based on mixtures of two different aromatic epoxides with four various aromatic amines, the solubility parameters δ were determined by calculation, by using several literature sources and molar additive laws, and experimentally from equilibrium concentrations of 25 solvents, by using bidimensional solubility maps. δ values ranging from 20 to 27 MPa1/2 were found. Their variations with the epoxide and amine structure were discussed. The crosslink density was found to have a neglectable effect on the solvent absorption compared to interaction parameters.
MMA/TPX homograft membrane for oxygen enrichment
Authors: Lai J. Y. , Shieh J. J. , Shyu S. S.
Published: April 2003

Utilizing the factors of degradation and crosslinking of TPX polymer and high O2/N2 selectivity of MMA, the performances of MMA homografted TPX membrane are efficiently improved compared to those of pure TPX membrane. The degradation and crosslinking of TPX polymer solution with or without dissolved oxygen during irradiation were observed and proved in existence by the gas permeability, mechanical, and viscosity change study. High O2/N2 permeability ratio of 7.6 and fairly high oxygen permeability of 28 × 10−10 cm3 cm/cm2 s cm Hg of the membrane which was cast from the degassing polymer solution, with 20% degree of MMA grafting, can be obtained. Also the membrane for high oxygen permeability of 63 × 10−10 cm3 cm/cm2 s cm Hg with an O2/N2 permeability ratio of 4.5, which was cast from the polymer solution with dissolved oxygen, can be obtained under the condition of 60 h irradiation time and about 7% degree of grafting. O2/N2 selectivity of TPX membrane can be improved by homografting method with lower MMA grafting degree than that of heterografting method.
Graft polymerization of polyvinylpyrrolidone onto silica
Authors: Chaimberg Mark , Parnas Richard , Cohen Yoram
Published: April 2003

A new technique is reported for the surface grafting of polyvinylpyrrolidone (PVP) to hydroxylated solid surfaces. Free radical graft polymerization of vinylpyrrolidone onto vinylsilane–modified impermeable silica particles was carried out in an aqueous slurry reactor. The graft yield and the monomer conversion were determined by thermogravimetric analysis and UV spectroscopy, respectively. The graft yield was shown to increase by increasing the initial monomer concentration. A comparison of the graft polymerization reaction with the adsorption of polyvinylpyrrolidone onto untreated, vinylsilane‐modified, and PVP‐grafted silica was performed.
Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. I. The effects of salts on the permselectivity of cellulose membrane in pervaporation
Authors: Mochizuki Akira , Sato Yoshio , Ogawara Hisashi , Yamashita Shuzo
Published: April 2003

In the separation of water/alcohol mixtures through cellulose membranes, the addition of trace amounts of specific salts to the feed mixture (10−5−5 × 10−3 mol/kg) caused the marked increase of the separation factor and only the salts composed of a multivalent metal ion and a multivalent counteranion were effective for the increase of the selectivity. For example, when 1.5 × 10−3 mol/kg CoSO4 was added to water/ethanol mixture (35/65 wt/wt), the separation factor was 194 and the permeation rate was 5.14 kg/m2 h. But, in the absence of the salt, the separation factor was only 6.7 and the permeation rate was 5.63 kg/m2 h. We presumed that the increase of the selectivity by the addition of specific salts would be attributed to the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of cellulose molecule.
Molecular orientation in the amorphous fraction of poly(ethylene terephthalate) and polyamide 6 fibers
Authors: Urbańczyk G. W.
Published: April 2003

Comparison of the Hermans orientation functions of the amorphous fraction of PET and PAG fibers oriented by stretching to various degrees was made. The orientation functions obtained by different methods enable one to draw conclusion about the acceptability of different methods and their correlation with each other.
Influence of the catalyst on the kinetics of a RIM formulation
Authors: Rego J. M. , Pastor M. A. , Campo J. J. , Katime Issa
Published: April 2003

The influence of three different catalysts [triethylendiamine (TD), stannous octoate (SO), and dibutylindilaurate (DBTDL)] and their blends (TD + SO and TD + DBTDL) on the kinetics of a RIM formulation, based on a high functionality polyether–polyol and a polymeric MDI, has been studied using the adiabatic temperature rise method and Fourier transform infrared spectroscopy. The synergism observed in the DBTDL/TD systems is explained by means of complex formation between the amine‐based and metal‐based catalysts. Infrared spectroscopy data support this complex formation. The SO/TD systems do not exhibit synergetic behaviour, being the reaction rate controlled by the metal catalyst which complexes the isocyanate group.
Mechanical behavior of closed cell plastic foams used as cushioning materials
Authors: Miltz J. , Ramon O. , Mizrahi S.
Published: April 2003

Two methods for the prediction of force–deformation curves of closed cell plastic foams at any strain rate from a limited number of experiments are described. These methods are based on the “modified Boltzman integral model” and on the “reference model.” Both methods use constitutive equations and experimentally determined parameters. The modified Botlzman integral model uses data obtained in a limited number of stress–relaxation experiments while the reference model uses a very limited number of stress–relaxation and one force–deformation curve data. Both models predict well the force–deformation curves, the reference model providing somewhat better predictions.
Polymerization of isoprene in n‐heptane with triethylaluminum–titanium tetrachloride catalyst. I. Effect of Al/Ti ratio on stereoregularity, conversion, molecular weight, and molecular weight distribution
Authors: Al‐Jarrah Mustafa M. F. , Abdul‐Latif Numan A. , Al‐Madfai Suham H. F. , Apikian Rita L.
Published: April 2003

The influence of the Al/Ti ratio of the heterogeneous Ziegler–Natta catalyst system AlEt3–TiCl4 on the isoprene polymerization in n‐heptane at 30°C in a bench scale reactor was investigated. Each batch run consisted of 50 mL isoprene, 200 mL n‐heptane with 0.45 and 0.5g catalyst. Conversion of isoprene and molecular weights of polyisoprene increased with increasing Al/Ti ratio, reaching their maxima values at 1.0 and 1.2, respectively. Conversion and molecular weights decreased remarkably at a higher ratio of Al/Ti. As this ratio decreases from the value of 1.2 to 0.4, the cis1,4 content in polyisoprene decreased from 97 to 25%. When the ratio of Al/Ti increased from 1.2 to 2.2 the cis‐1,4 structure of polyisoprene decreased from 97 to 85%.
The preparation and properties of acrylic and methacrylic acid grafted cellulose prepared by ceric ion initiation. III. Some physical, mechanical, and ion exchange properties
Authors: Vitta S. B. , Stahel E. P. , Stannett V. T.
Published: April 2003

The first two articles were concerned, (1) with the preparation and, (2) with the water retention properties of the grafted cellulose. This articel presents some physical, mechanical, and ion exchange properties. Bleached sulfite softwood puplp filter paper was the substrate and polyacrylic acid the grafted side chains. The thickness of the paper increased with grafting accompanied by a decreased in area, particularly in the machine direction. The air permeabilities of the grafted papers were essentially unchanged even at high degrees of grafting. The dry tensile strength increased somewhat with grafting but the zero span strength decreased. Wet tensiles increased considerably up to about 50% graft, but then decreased. The wet elongations, however, steadily increased but began to level off at 120% graft. Strength properties were also measured with melamine wet strenghened paper. The ion exchange capacities of the dispersed paper pulp indicated that all the grafted polyacid groups were rapidly utilized.
Pole figure analysis of poly(vinyl chloride) samples: A first approximation
Authors: Guerrero Saul J.
Published: April 2003

Pole figure analysis has been applied to different types of poly(vinyl chloride) (PVC) samples. Drawn samples of formulations containing increasing amounts of plasticizer show that the presence of plasticizer at concentrations exceeding 20 pph decreases the orientation of the crystalline phase for a given draw ratio. Cast and pressed films of PVC show incipient orientation in the plane of the films. This orientation can be removed to a great extent by immersing the films in diethyl ether. The method is experimentally feasible and the resolution achieved is determined by the automation of the equipment.
A simple one‐step synthesis of unsaturated copolyesters
Authors: Mathias Lon J. , Kusefoglu Selim A. , Kress Albert O.
Published: April 2003

Copolyesters containing pendent vinylidine groups were prepared in a one‐step synthesis by reacting either chloro‐ or bromoacetic acid with 2‐(bromomethyl)acrylic acid and triethylamine in diethyl ether. Polymers were characterized by IR, 1H‐ and 13C‐NMR, DSC, and TGA. Copolymer formation supports a mechanism involving a triethylammonium carboxylate salt acting as an active nucleophilic species in a manner analogous to that seen in phase transfer catalysis involving carboxylate anions. Comparison of 13C‐NMR spectra intensities indicates that 2‐(bromomethyl)acrylic acid is much more reactive than the haloacetic acids leading to higher copolymer incorporation than in the monomer feed. Unsaturation in the copolymers provides a site for crosslinking during radical polymerization with an added vinyl monomer, similar to the way unsaturated polyesters function in commercial fiberglass formulations. This was confirmed by polymerization of both styrene and methyl methacrylate in the presence of an unsaturated copolymer giving insoluble semi‐interpenetrating networks. These unsaturated copolymers are the first examples of soluble biodegradable glycolic acid polyesters containing such reactive functionality.
Kinetics of polyesterification of 1,3‐(dicarboxymethoxy) benzene with tetraethylene glycol
Authors: Shaaban A. F. , Moustafa H. Y. , Messiha N. N.
Published: April 2003

The polyesterification of 1,3‐(dicarboxymethoxy)benzene with tetraethylene glycol in both equimolar and nonequimolar ratios were studied over the range of 120–160°C in the absence and presence of p‐toluenesulphonic acid as catalyst. The experimental results for uncatalyzed reactions agreed quite well with the kinetic equation proposed by Flory. The kinetic equations for acid‐catalyzed reactions, however, are in agreement with the kinetic equation proposed by Lin and Hsieh. The kinetic equations were −d[COOH]/dt = k1[COOH]2[OH] and −d[COOH]/dt = k2[COOH]2 for uncatalyzed and acid‐catalyzed polyesterfications, respectively. The rate constants for uncatalyzed and acid‐catalyzed reactions were calculated by using the method of least squares for various values of initial molar ratio between [OH] and [COOH]. Also, the activation energies were calculated.
Rheological behavior of ultrahigh molecular weight polyethylene semidilute solutions. II. Effect of aluminium stearate
Authors: Chen Kequan , Zhang Anqiu , Lu Pin , Wu Zongquan
Published: April 2003

The effect of aluminium stearate on the rheological behavior of ultra‐high molecular weight polyethylene (UHMWPE) semidilute solutions with paraffin oil as the solvent has been investigated. Adding aluminium stearate to paraffin oil can prevent the spinning solution from adhering to the pipe or screw, greatly improving the flow behavior of UHMWPE solutions. The geometric sizes of spinnerette hole, such as length–diameter ratio L/D and entrance angle of a capillary, also affect the flow behavior of the spinning solution. The calculated first normal stress difference σ11 − σ22 and the Bagley‐end correction e from experimental data show that the elastic effect on spinning solutions in flow is quite large, although the shear rate is below 20 s−1.
Polymer characterization by thermal field flow fractionation with a continuous viscosity detector
Authors: Kirkland J. J. , Rementer S. W. , Yau W. W.
Published: April 2003

A sensitive flow viscometer detector has been successfully used with time‐delay, exponential‐decay thermal field flow fractionation (TDE‐TFFF) to produce unique information on polymers. TFFF with a concentration‐dependent detector (e.g., refractometer) and a differential capillary viscometer is unable to produce a universal calibration plot that eliminates the necessity of polymer standards for accurate molecular‐weight calibration. However, this system directly provides valuable information on the inherent (or intrinsic) viscosity distribution of polymers. Absolute intrinsic viscosity values are measured by TFFF without the need of calibration. Detailed TFFF/inherent‐viscosity distribution profiles uniquely describe individual sample differences and are not affected by the experimental conditions used in TFFF separations. These viscosity distributions should be very useful in polymer characterization, since they are closely correlated with polymer end‐use and solution properties, as well as to polymer molecule weight.
Studies on the polyblends of poly(vinyl chloride) with various methacrylate copolymers, melt rheological properties. II
Authors: Saroop U. K. , Sharma K. K. , Jain K. K. , Misra Ashok , Maiti S. N.
Published: April 2003

Studies have been made on the melt rheological properties of poly(vinyl chloride) (PVC) with copolymers of methyl methacrylate (MMA) and methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2‐ethyl hexyl acrylate (EHA) at a blending ratio of 80:20. Effect of blend composition on shear stress–shear rate, melt viscosity, melt elasticity, and extrudate distortion have been studied. A significant decrease in the melt viscosity is observed on incorporation of low Tg, acrylate copolymers such as those with BA and EHA, thereby reducing the processing temperature. First normal stress and die swell ratio also decreases with an increase in the side chains of acrylate copolymer. PVC blended with P(MMA‐co‐BA) and P(MMA‐co‐EHA) is sensitive to both temperature and shear stress.
Studies on binary and ternary blends of polypropylene with ABS and LDPE. I. Melt rheological behavior
Authors: Gupta A. K. , Jain A. K. , Maiti S. N.
Published: April 2003

Studies are presented on melt rheological properties of binary blend of polypropylene (PP) and acrylonitrile–butadiene–styrene terpolymer (ABS), and ternary blend of PP, ABS, and low‐den‐sity polyethylene (LDPE). Data obtained in capillary rheometer are presented to describe the effect of blending ratio, shear stress, and shear rate on flow properties, melt viscosity, and melt elasticity. At a blend composition corresponding to 10 wt % ABS content, both binary and ternary blends show maximum in melt viscosity accompanied by minimum in melt elasticity. Pseudoplasticity of the melt decreases with increasing ABS content. In ternary blends, LDPE facilitates the flow at low LDPE contents and obstructs the flow at high LDPE contents. Scanning electron microscopic studies are also presented to illustrate the state of dispersion and its variation with blend composition.
Higher aluminum trialkyls and magnesium aluminum alkyls as components of zioegler–natta catalysts
Authors: Gaponik L. V. , Antipova A. M. , Morozova T. K. , Mardykin V. P.
Published: April 2003

Magnesium aluminum alkyls containing higher (C4–C10) radical swere studied as components of Ziegler–Natta catalysts in styrene polymerization. The effects of alkyl radical length and MgR2 contents in the components mentioned on the degree of TiCl4 reduction and sterospecific activity of the catalysts were investigated. The components studied exdhibited high reducing (for TiCl4) and catalytic a tivities. Moleculear weight of the synthesized isotactic polystyrene was abnormally high.
Radiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene‐tetrafluoroethylene) film by preirradiation method. II. Properties of cation‐exchange membrane obtained by sulfonation and hydrolysis of the grafted film
Authors: Momose Takashi , Yoshioka Hiroko , Ishigaki Isao , Okamoto Jiro
Published: April 2003

A Study was made on certain properties of the cation‐exchange membranes obtained by the preirradiation grafting of α,β,β‐trifluorostyrene (TFS) noto poly(ethylene‐tetrafluoroethylene) (ETFE), followed by sulfonation and hydrolysis of the grafted film. Swelling, water uptake, electric conductivity, and transport number of the membranes were measured as a function of ino‐exchange capacity. Thermal and chemical stability were also investigated. These properties were found to be mainly dependent on ion‐exchange capacity. The stable membrane properties were established due to a homogeneous ion‐exchange group distribution in the membrane, as confirmed by x‐ray imcroscopy analysis of the membrane cross sections. In addition, the membranes showed good electrochemical, thermal, and chemical properties, and were found to be scceptable for practical use as cation‐exchange membranes.
Preparation by suspension polymerization of porous beads for enzyme immobilization
Authors: Skovby Michael H. B. , Kops Jørgen
Published: April 2003

Porous beads have been prepared by suspension polymerization of acrylic monomers and divinyl benzene in the presence of a porogen. The porosity varies greatly with the polymer composition, with the amount and type of porogen and with the conditions for the preparation. The enzyme binding capacity and activity has been determined for a lipase. The best results are found for crosslinked poly(methyl methacrylate) beads while other polyacrylates are less effective. Compositions based on poly(methacrylic acid) are not suitable for enzyme binding.
Influence of dimethyl sulfoxide on the kinetics of the graft copolymerization of acrylonitrile onto the jute fibers initiated by ceric ion
Authors: Das N. R. , Nayak N. C. , Das H. K. , Mishra S. N. , Singh B. C.
Published: April 2003

A study of the influence of dimethyl sulfoxide (DMSO) on the graft copolymerization of acrylonitrile (AN) onto jute fiber using ceric ion has been made. The effect of concentrations of monomer, Ce(IV) and DMSO on graft yield have been studied. Besides, the effect of time, temperature, acid, and the amount of jute fiber on graft yield has been investigated. On the basis of experimental findings, a reaction mechanism has been proposed and optimum condition for effective grafting has been suggested.
Morphological studies on the blends of poly(butylene terephthalate) and bisphenol‐A polycarbonate
Authors: Halder R. S. , Joshi Mangala , Misra A.
Published: April 2003

The morphology of the blends of poly(butylene terephthalate) (PBT) and bisphenol‐A polycarbonate (PC) crystallized from the melt were studied by density measurement and small angle light scattering techniques. Rate of crystallization of these blends was found to be slower with increasing amount of PC. The Avrami exponent n for the blends was calculated and related to the shape of superstructures formed. Hv and Vv scattering patterns as seen by small angle light scattering were analyzed to determine the nature, shape, and size of the superstructures. The changes in the superstructure formation with increasing amount of PC in these blends have been analyzed.