bluuebunny/crossref_metadata_2025 huggingface dataset:
New block copolymers II. Synthesis and characterization of an ABA‐type block copolymer
Authors: Shit Subhas C. , Mahato Beni Madhab , Maiti Mrinal M. , Maiti Sukumar
Published: April 2003

A new regular ABA‐type triblock copolymer has been synthesized by polycondensation of the acid chloride of carboxy‐terminated butadience‐acrylonitrile rubber (CTBN) with hydroxyterminated polyethylene isophthalate (PEI) oligomer. This block copolymer was characterized by elemental (nitrogen) analysis, vapor pressure osmometry, viscometry, and IR and NMR spectroscopy. Quantitative estimation of block segments has been carried out by measuring the area under peaks assigned to various protons in the NMR spectrum of the polymer. NMR spectral analysis has been found to agree well with the nitrogen analysis of the polymer. The solubility and solution viscosity behavior of the polymer has also been studied.
The use of dyestuff‐treated rice hulls for removal of heavy metals from waste water
Authors: Suemitsu R. , Uenishi R. , Akashi I. , Nakano M.
Published: April 2003

Rice hulls, when coated with the reactive dye of Procion Red or Procion Yellow, was found to be highly effective for removal of many metal ions from aqueous solutions both in batch and column method. When 120–130 ppm solutions were used, quantitative removal could be achieved with Pb2+, Cd2+, and Hg2+. After the adsorption of metal ions, the substrate could be recovered almost completely by treating with dilute hydrochloric or nitric acid solution, and used repeatedly.
Modelization of matter transfers between plasticized PVC and liquids in case of a maximum for liquid‐time curves
Authors: Taverdet J. L. , Vergnaud J. M.
Published: April 2003

When plasticized PVC and liquids are contacted with each other, as in liquid and packaging, some matter transfer may occur. The phenomenon is complicated, and no analytic solution can be found. A simultaneous transfer of the liquid into and plasticizer out from the PVC mass takes place with concentration‐dependent diffusivities. Very often, liquid concentrationtime curves have a maximum, when the rate of transfer is higher for the liquid than for the plasticizer at the beginning of the contact. Another application of short tests has been obtained with success in this hard case. A new model using short test data has been developed. It takes into account not only the diffusion of both liquids through the PVC, but also matter transfers through the liquid—PVC interface with a coefficient of matter transfer, as well as the data corresponding to the equilibrium. Some information of interest is given by way of the materials transferred through PVC faces, and the profile of concentration through the PVC for the liquid and plasticizer.
Preparation of Tri‐O‐alkylcellulose by the use of a nonaqueous cellulose solvent and their physical characteristics
Authors: Isogai Akira , Ishizu Atsushi , Nakano Junzo
Published: April 2003

Tri‐O‐methyl‐, ‐ethyl‐, ‐n‐propyl‐, ‐n‐butyl‐, ‐n‐pentyl‐, ‐iso‐amyl‐, ‐n‐hexyl‐, ‐n‐heptyl‐, ‐n‐octyl‐, ‐n‐decyl‐, and ‐3‐phenoxypropyl‐celluloses have been prepared with powdered sodium hydroxide and the corresponding alkyl iodides or bromides in one of nonaqueous cellulose solvents, SO2‐diethylamine‐dimethylsulfoxide. These new tri‐O‐alkylcelluloses were characterized by infrared spectra, 13C‐NMR spectra, and optical rotations. The first six tri‐O‐alkylcelluloses described above were obtained as white powders and most of them (tri‐O‐methyl‐, ‐ethyl‐, ‐n‐propyl‐, and ‐n‐pentyl‐celluloses) showed thermotropic liquid crystals due to smetic or short pitch cholesteric phases. On the other hand, the latter five derivatives were obtained as gummy solids even at room temperature, and easily showed lyotropic liquid crystals in their concentrated chloroform solutions due to choresteric phases. some of these tri‐O‐alkyl‐celluloses (tri‐O‐methyl‐, ‐ethyl‐, ‐n‐propyl‐, and ‐n‐butyl‐celluloses) were characterized by differential scanning calorimetric and X‐ray diffractometric analyses.
Postirradiation polymerization of vinyl monomers on poly(ethylene terephthalate)
Authors: Hsieh Y. ‐L. , Shinawatra M. , Castillo M. D.
Published: April 2003

A postirradiation process was evaluated in polymerizing vinyl monomers on poly(ethylene terephthalate) (PET) film, fiber, and fabric. The use of DMF, pyridine, and DMSO as swelling agents to facilitate monomer incorporation and effective polymerization were also investigated. The solvents were effective in promoting the incorporation of acrylic acid (AA) in PET film and that of n‐vinyl‐2‐pyrrolidinone (VP) in Dacron 54. AA, a good swelling agent for PET, produced equivalent polymerization yield and moisture regain results with or without any solvent on Dacron 54 and 64. Polymerization yields on films increased with increasing total doses, but those on yarns and fabrics were independent of total dose. The different results obtained on film versus yarn and fabric from solvent treatment and total dose is thought to be due to the different surface‐volume ratio of these substrates. The moisture properties of the substrates were dependent mainly upon the monomer type. Among the monomers studied, VP gave highest moisture regain values, followed by AA. The tensile properties of the modified Dacron 54 were not affected. However the breaking elongation of the modified Dacron 64 was slightly lowered by postirradiation polymerization without solvent treatment and was increased when solvent treatment was included.
The viscosity of concentrated polymer solutions containing low molecular weight solvents
Authors: Richards William D. , Prud′homme Robert K.
Published: April 2003

The zero shear rate viscosities of polystyrene/ethylbenzene solutions having polymer weight fractions ranging from 0.5 to 1.0 have been measured using a novel sealed rheometer cell over a temperature range of 50 to 200°C. The concentration and temperature dependence of the solution viscosity has been found to be well described by the relation η0 = K caMw3.4ζ(c, T) where the monomeric friction coefficient ζ is determined by the free volume of the solution. Following the procedure of Berry, the free volume parameters, αf(c)/γ and T∞ (c), and the fractional free volume, f(c,T)/γ, have been determined. After using these parameters to account for the concentration dependence of the friction coefficient, the concentration exponent a has been evaluated and found to be in reasonable agreement with the value of 3.4 obtained by Berry and Fox for other polymer/solvent systems. A comparison of the relative conributions made by the friction coefficient and the term c3.4 to the overall concentration dependence of the viscosity of these highly concentrated solutions shows the friction coefficient to be the dominant factor
Diffusion/adsorption model of cellulose dyeing. I. The diffusion through never‐dry cellulose
Authors: Morita Zenzo , Tanaka Takaaki , Motomura Hiromi
Published: April 2003

The diffusion coefficients D0, of C.I. Direct Yellow 12, Red 2, Blue 1, and Blue 15 in aqueous NaCl solution were measured at 90°C by the diaphagm cell method. The values of D0 for Yellow 12 and Red 2 showed a salt concentration dependence and those for Blue 1 and Blue 15 were constant over the ionic strength range from 0.01 to 0.10. In the adsorption/diffusion models proposed so far for the direct dye–cellulose system, the Standing–Warwicker–Willis model was shown to be similar in principle to the Weisz–Zollinger model. The adsorption/diffusion behaviors in never‐dry cellophane sheet for C.I. Direct Yellow 12 and Blue 15 were examined by the method of cylindrical film roll at 90°C. The concentration dependence of the apparent diffusion coefficient for these dyes showed an incomplete validity of both the models.
Effect of pretreatment of cellulosic wastes on the production of cellulase enzymes by Trichoderma reesei
Authors: Kassim E. A. , Ghazi I. M. , Nagieb Z. A.
Published: April 2003

The cellulosic wastes, bagasse and sawdust, were treated with different acidified solvents: chloroform, dioxan, ethanol, ethylacetate, dimethyl sulfoxide and dimethyl formamide; for increasing periods up to 36 h. The treated materials were delignified, dried and introduced in the fermentation media as inducing carbon source for Trichoderma reesei. The untreated materials and pure cellulose powder were used individually in control and reference media, respectively. The fermentation media containing bagasse treated for 8 h in chloroform or dioxan gave a promising cellulase activity, nearly the same as that from the reference medium. The untreated bagasse gave a markedly low cellulase activity.

The media with treated sawdust gave a relatively higher enzyme activity but far below the reference medium. The sawdust treatment with the solvents mentioned resulted in a very mild effect because of its high content of admixtures, lighin and hemicellulose bonding cellulose.
Preparation of polymers with pendant quinonoid groups and their photocrosslinking with visible light irradiation
Authors: Cha Younsik , Tsunooka Masahiro , Tanaka Makoto
Published: April 2003

Photosensitive polymers with pendant quinonoid groups were prepared by the reaction of p‐(benzoquinon‐2‐ylthio) acetic acid (QTAA) or p‐(p‐benzoquinon‐2‐ylthio)benzoic acid (QTBA) with hydroxyethyl methacrylate‐methyl methacrylate copolymer. The polymers showed a strong π‐π* absorption band at around 410 nm and were efficiently crosslinked by visible light irradiation. Somewhat higher photosensitivity of QTAA‐bound polymer compared with that of QTBA‐bound polymer suggested some contribution of intramolecular hydrogen abstraction of QTAA to the photocrosslinking.
Nonisothermal bulk copolymerization of styrene and methyl methacrylate in a CSTR: Multiplicity and stability analysis
Authors: Balaraman K. S. , Kulkarni B. D. , Mashelkar R. A. , Madhavan K. P.
Published: April 2003

A theoretical investigation of the nonisothermal bulk copolymerization of styrene and methyl methacrylate in a CSTR is reported. A modified framework of free volume theory is developed for a copolymerization system to account for the effect of concentration and temperature on the propagation and termination processes. The evolution of multiple steady states for a set of system parameters has been demonstrated. The stability of these steady states has also been examined.
Thermotropic polyester amide‐carbon fiber composites
Authors: Chung Tai‐Shung , McMahon Paul E.
Published: April 2003

Liquid crystal polymers (LCP) have been developed for the first time as a thermoplastic matrix for high‐performance composites. A successful melt impregnation method has been developed that results in the production of continuous carbon fiber (CF)‐reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality.

Tensile and flexural properties of LCP‐CF composites are comparable to those of epoxy‐CF composites. LCP‐CF composites have better impact resistance than the latter, although epoxy‐CF composites possess superior compression and shear strength. LCP‐CF composites have good property retention until 200°F (67% of room temperature value). Above 200°F, mechanical properties are found to decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber.
Mechanical properties of crosslinked polyethylene
Authors: Andreopoulos A. G. , Kampouris E. M.
Published: April 2003

The mechanical properties of crosslinked polyethylene were studied in an extended range of test conditions in order to determine the recommended service conditions for articles made of crosslinked polyethylene. On the other hand, this study can clarify the advantages of crosslinked polyethylene against the unmodified polymer. In fact, the results referred in the literature concerning the changes of mechanical properties of polyethylene introduced by crosslinking are contradictory and cannot clearly distinguish the two types of polymer. The above study concluded that tensile tests at elevated temperatures (above 70°C) with low stresses (about 0.5 MPa) can clearly describe the effect of crosslinking on the mechanical properties of LDPE, i.e., an improvement at least for deformation and service life.
Flame‐resistant polycaproamide by anionic polymerization of ϵ‐caprolactam in the presence of suitable flame‐retardant agents
Authors: Alfonso Giovanni Carlo , Costa Giovanna , Pasolini Massimo , Russo Saverio , Ballistreri Alberto , Montaudo Giorgio , Puglisi Concetto
Published: April 2003

Poly(ϵ‐caprolactam) (PCL) with improved flame‐retardant (FR) properties can be easily obtained by activated anionic polymerization of the monomer, ϵ‐caprolactam (C), in the presence of adequate amounts of red phosphorus (red P). Analogous results with reduced P content can be achieved by coupling red P with a synergistic compound such as a chlorinated hydrocarbon or magnesium oxide (MgO). A peculiar advantage of this method is the possibility of obtaining a very fine and homogeneous dispersion of the FR additive in the polymer matrix, meanwhile avoiding the typical compounding techniques, which are expensive, often unsafe, and require melt mixing of the ingredients. Molecular, thermal, and mechanical characterization, as well as morphology of the resultant products, have been determined: No significant properties change have been found when FR agents are present, apart from the relevant improvement of the flame‐resistance. Thus, by this novel procedure it is possible to prepare FR poly‐(ϵ‐caprolactam) without any appreciable deterioration of its typical properties.
Aging of pressure‐sensitive adhesives III. Studies of surface oxidation with multidetector size exclusion chromatography
Authors: Harrison Daniel J. , Yates W. Ross , Johnson Julian F.
Published: April 2003

The use of multidetector size exclusion chromatography is described for studying oxidation in styrene‐isoprene‐styrene block copolymer films. It is shown that exposure of these films to atmospheric oxygen causes surface oxidation of the isoprene midblocks and that the antioxidant system used is incapable of preventing this. Higher temperature exposure initially merely accelerates the surface reaction but is followed after an induction period by severe bulk‐phase degradation. The implications of ambient temperature surface oxidation of SIS‐based pressure‐sensitive adhesives are discussed.
Polyester polyurethane ionomers
Authors: Rutkowska Maria
Published: April 2003

The urethane elastomers based on 4,4′‐diphenylmethane diisocyanate (MDI), oligo (ethylene adipate) (OEA) with different chain extenders, and dibromohexane or ammonium salt were synthesized. Their mechanical and thermal properties were studied by stress‐strain analysis, thermomechanical methods, and differential thermal analysis. It was demonstrated that the incorporation of ionic groups in the structure of urethane elastomers due to the reaction of dibromohexane with a tertiary amine or urea NH group improves their tensile strength and thermal resistance.
Manufacture and physical properties of alginate fiber papers as an analysis model of cellulosic fiber papers
Authors: Kobayashi Yoshinari , Matsuo Ryûkichi , Kawakatsú Hironobu
Published: April 2003

The staple fibers of Ca alginate or alginic acid were found to have interfiber self‐bonding, which allowed us to make papers composed of fibers with homogeneous fiber diameter and fiber length without binders. The analysis of the effect of the molecular weight (MW) and fiber diameter on physical properties of the sheets showed that strength factors, except zero span breaking length and tear index, increased with increase of MW of alginic acid up to 6 × 105 dalton. The folding endurance was the most sensitive to MW, requiring a MW of 5 × 105 dalton or higher to reach the level of 10 folds. The breaking length of alginate fiber papers ranged from 2.0 to 3.5 km and was higher than that of the corresponding free acid fiber sheets. Investigation of the effect of fiber length indicated that the folding endurance increased almost linearly with increase in fiber length but that the breaking length and tear index were maximum at a fiber length of 3.0 mm, suggesting that these factors were mainly influenced by sheet formation. The paper formability of the metallic salts of alginate fiber was as follows: Ca2+ > Ba2+ > Al3+ > > Fe3+. The admixture of acidic polysaccharides, such as pectin and κ ‐carrageenan with Na alginate, also made it possible to spin continuous yarn. Papers obtained from the admixed fibers had higher bulk density and Young's modulus by 1.5–1.8 times and were very transparent, just like glassine paper. X‐ray microanalysis showed that the Ca alginate fiber had no skin‐core structure, homogeneously distributing Ca2+ in whole fiber.
Heterogeneous styrene–divinylbenzene copolymers in collapsed and reexpanded states
Authors: Okay O. , Balkaş T. I.
Published: April 2003

The pore structure of styrene–divinylbenzene (DVB) copolymers formed by phase separation before or after gelation was compared using apparent densities and mercury porosimetry. The copolymers were prepared with di‐2‐ethylhexyl phthalate (DOP) as diluent. The pore structure of copolymers formed in homogeneous gelation can collapse upon drying in the rubbery state. The collapsed pores have a mean diameter of about 100–200 Å corresponding to the interstices between the microspheres. The collapsed microspheres reexpand again during the sulfonation or chloromethylation reactions, or during the solvent exchange. The pore structure of styrene–DVB networks formed in heterogeneous gelation do not collapse on drying in the swollen state, this being a stable and permanent porosity. The critical crosslink density for transition from homogeneous to the heterogeneous gelation represents a borderline between stable and unstable porosity. The drastical change of swelling and porosity values at the critical crosslink density is due to the collapse of unstable pores.
Polybutadiene hydroperoxide by singlet oxygen: Its grafting and morphology in polystyrene matrix
Authors: Peng F. M.
Published: April 2003

Singlet oxygen was used to synthesize hydroperoxide functional groups onto a polybutadiene. These hydroperoxides served as grafting sites for the preparation of polybutadiene‐modified polystyrene by a bulk polymerization process. As anticipated, the dispersed polybutadiene droplet size decreased as the level of hydroperoxidation increased. Various types of morphology, similar to those of butadiene–styrene diblock and styrene–butadiene–styrene triblock copolymer systems, were obtained. Furthermore, at an extremely high level of hydroperoxidation, a unique reticular structure of polybutadiene was developed.
Effect of radiation chemical treatment on sisal fibers I. Radiation induced grafting of ethyl acrylate
Authors: Zahran A. H. , Zohdy M. H.
Published: April 2003

Radiation induced graft copolymerization of ethyl acrylate onto sisal fibers was investigated. It was fond that the percent added‐on of ethyl acrylate to sisal fibers was prohibitively low when using the direct grafting method due to excessive hompolymerization. The preirradiation method was found to be invalid for improving the grafting content. In the presence of small amounts of styrene (St) the copolymerization can be achieved with little homopolymer formation by the direct grafting technique. The presence of sulfuric acid in the grafting solution enhances the grafting of styrene–ethyl acrylate comonomer to sisal fibers. the effect of different solvents, monomer concentration, and irradiation doses were followed. Sisal fibers were treated with sodium hydroxide, sulfuric acid, and combined treatment of both of them. The effect of these treatments on the grafting content was investigated. The grafting yield decreased when sisal fibers were subjected to alkali treatment under tension. However, sisal fibers pretreated with 0.4N sulfuric acid showed a slight increase in the grafting yield over the untreated samples.
Invariant kinetic parameters of polymer thermolysis. I. Oxidative degradation of flame‐retardant polyesters
Authors: Lesnikovich A. I. , Levchik S. V. , Levchik G. F.
Published: April 2003

The paper gives an analysis of the data reported by J. D. Cooney and others. [J. Appl. Polym. Sci., 29, 911 (1984)] on the kinetics of oxidative degradation of flame‐retardant polyesters [poly(ethylene terephthalate)]. A linear correlation is shown to exist between the parameters of the kinetic compensation effect. A formal interpretation of the correlation is given as well as its interpretation within two alternative polyester degradation schemes. The above correlation allowed the invariant kinetic parameters of the process log Â = 15.7±1.3;Ê = 183±16 (min−1; kJ/mol) to be estimated, which seem to characterize the destruction of the polyester bond in the presence of oxygen. It is shown that Â and Ê may be used to characterize the kinetics of polyester oxidative degradation during combustion, while the compensation parameter T̂; may characterize the flame‐retardant effect.
Effects of mechanical drawing on gas transport in an emulsion acrylic multipolymer
Authors: El‐Hibri M. J. , Paul D. R.
Published: April 2003

A study was conducted on the gas sorption and transport properties of a multiphase commercial acrylic polymer trade‐named Korad ACV before and after subjecting the polymer to mechanical drawing operations. The Korad system is an emulsion‐polymerized amorphous composite comprised of a glassy, predominantly PMMA matrix phase and a ply(butyl acrylate)‐dispersed phase surrounded by a PMMA/PBA copolymer shell. Large increases (up to eightfold) in permeabilityPto several gases were observed upon drawing Korad. The observed changes in the permeability to He, Ar, N2, and CH4on drawing were correlated with the draw ratio, drawing temperature, and molecular diameter of the gas penetrant. Most of the increase in permeability occurred at low draw ratios (1–2). The increases inPwere most dramatic for drawing temperatures below or near theTgof the matrix phase (about 90°C) and were quite small for drawing temperatures 30°C or more above the matrixTg. The extent of the permeability increase also depended on the gas, being greatest for CH4and essentially imperceptible for He. The changes in permeability behavior were interpreted in terms of a morphological transformation in the phase of the drawn Korad, which causes the originally dispersed rubber particles to assume a more continuous character. The behavior of the composite was modeled by the Takayanagi and Nielson treatments of two‐phase composite systems. Volumetric, thermal, mechanical, and viscoelastic properties were measured for the as‐received and processed Korad films to elucidate physical changes in the drawn polymer.
The concept of solid solvent as a processing aid
Authors: Chung Chan I.
Published: April 2003

The concept of solid solvent entails the use of low‐molecular weight crystalline materials (LMC) as a processing aid. A LMC as an ideal solid solvent mixed into a polymer is expected to become a solvent for the polymer at high processing temperatures, reducing the melt viscosity and thus enhancing the processability, but to become a nonsolvent for the polymer at low use temperatures precipitating out of the polymer without adversely affecting the properties of the polymer. The feasibility of such a concept was examined using acetanilide as a potential solid solvent for polystyrene (PS) and two ABA‐type block copolymers containing PS end blocks. Acetanilide demonstrated the essential features required of a solid solvent supporting the concept of solid solvent. It had a high solubility in PS at high temperatures very effectively reducing the melt viscosity of PS and the block copolymers, and it precipitated out of PS at low temperatures although it had an undesirably high residual solubility. The concept of solid solvent appears to be a viable one.
The effect of some catalysts on the curing of oxiranes with p‐phenylenediamine
Authors: Kishore K. , Joseph Mary , Dharumaraj Verghese , Vijayshree M. N.
Published: April 2003

The effect of some alcohols, acetylacetonates of transition metals, and manganese stearate and naphthenate on the curing reaction of a diglycidyl ether of ether of bisphenol‐A with p‐phenylenediamine is studied. Maximum catalytic activity is shown by the manganese compounds and triethanolamine.
Polymerization of olefins through heterogeneous catalysis. III. Polymer particle modelling with an analysis of intraparticle heat and mass transfer effects
Authors: Floyd S. , Choi K. Y. , Taylor T. W. , Ray W. H.
Published: April 2003

Propylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. Intraparticle heat and mass transfer effects are investigated for a range of catalyst activities. For slurry polymerization, intraparticle mass transfer effects may be significant at both the macroparticle and microparticle level; however, for normal gas phase polymerization, microparticle mass transfer effects appear more likely to be important. Intraparticle temperature gradients would appear to be negligible under most normal operating conditions.
A kinetic scheme for an amine‐epoxy reaction with simultaneous etherification
Authors: Riccardi Carmen C. , Williams Roberto J. J.
Published: April 2003

The curing reaction of an epoxy resin with a diamine is analyzed, taking into account the possibility of simultaneous etherification. A kinetic scheme is derived and fitted to experimental results for the reaction of commercial bisphenol A diglycidyl ether (BADGE) with diaminodiphenyl sulfone (DDS). Total reaction heat, vitrification curve, and reactivity ratio of secondary to primary amine hydrogens are experimentally characterized. It is shown that the etherification reaction is significant at T > 150°C, at intermediate and high reaction extents when the primary amine has been sufficiently depleted.
Elastomer solvent interactions III‐effects of methanol mixtures on fluorocarbon elastomers
Authors: Myers Mark E. , Abu‐Isa Ismat A.
Published: April 2003

Fluorocarbon elastomers exhibit high volume swell in methanol, but not in ethanol or other alcohols. Proton nuclear magnetic resonance (NMR) data indicate that neat methanol exists as a hydrogen‐bonded tetramer with a solubility parameter close to that of the fluorocarbon elastomer, thus causing the high swell. The NMR and volume swell data show further correlations: Increased temperature or dilution of methanol with nonpolar solvents or water breaks down the hydrogen‐bonded structure and reduces the volume swell. Mixtures of methanol and ethanol form mixed tetramer species. In this case the volume swell can be predicted by statistical theory which indicates that an all‐methanol tetramer and a tetramer containing one ethanol molecule are the only swelling species. Similarly, a tetramer singly substituted with butanol is too bulky to swell the elastomer. Thus the molecular structure of methanol and its mixtures as determined by NMR provides an explanation for the swelling of fluorocarbon elastomers in these environments.
The effect of precipitation on the molecular weight distribution of cellulose tricarbanilate
Authors: Wood Barry F. , Conner Anthony H. , Hill Charles G.
Published: April 2003

The effect of precipitation on the molecular weight distributions of cellulose tricarbanilate (CTC) samples prepared from α‐pulp, hydrolyzed α‐pulp, and Avicel was determined using size exclusion chromatography (SEC). Precipitation of the CTC samples in methanol resulted in the loss of a low molecular weight fraction accounting for 26% of the weight of the hydrolyzed α‐pulp, 20% of the Avicel, and 5% of the α‐pulp. Precipitation in a methanol/water mixture resulted in less fractionation; in this case, however, the reaction byproducts were also precipitated. These results indicate that the molecular weight distribution of precipitated CTC may not accurately reflect the molecular weight distribution of the original cellulose. SEC analysis of the nonvolatile products from the carbanilation reaction offers a simple method for determining the complete molecular weight distribution of this cellulose derivative.
Effect of sequence distribution of poly(vinyl alcohol‐vinyl acetate) on the coloring reaction with iodine
Authors: Hirai Toshihiro , Okazaki Akira , Hayashi Sadao
Published: April 2003

Red complex formation between poly(vinyl alcohol‐vinyl acetate) with iodine was investigated from the standpoint of its application as a measure of sequence distribution in the copolymer. Defining a parameter Y which means a ratio of the bound triiodide ion to the VAc unit in a copolymer, we could relate the Y value to the sequence probabilities. Sequence probabilities have also been evaluated by differential thermal analysis. Comparing the probabilities obtained from both methods, the iodine complexation method is concluded to be a complementary method with thermal analysis, that is, the iodine complexation method is applicable to the VAc unit‐rich copolymers, in which the melting point cannot be measured by the thermal analysis.
Molecular weight distribution of polyphenylene sulfide by high temperature gel permeation chromatography
Authors: Stacy Carl J.
Published: April 2003

Poly(phenylene sulfide) (PPS) has been characterized using a novel high temperature gel permeation chromatograph (GPC). Samples were injected in slurry form at ambient temperature, and redissolved by an in‐line precolumn heater at 250°C. A viscometer consisting of a capillary tube with inlet and outlet taps connected to a sensitive differential pressure transducer was used as sole detector, with deflections converted to concentration using the column calibration. Columns and viscometer were operated at 210°C. Universal calibration was carried out using intrinsic viscosity/molecular weight relations for polystyrene and PPS, determined by light scattering. Satisfactory operation was confirmed by agreement between intrinsic viscosity calculated from GPC with independently measured values, and comparisons with melt flow data. Samples of PPS tested were found to be of relatively narrow distribution, with Mw/Mn typically less than two.
Melaminium molybdate smoke and fire retarders for poly(vinyl chloride)
Authors: Kroenke William J.
Published: April 2003

Melaminium molybdates are shown to be very effective smoke and fire retarder additives for PVC. In a simple tin stabilized rigid PVC compound the preferred melaminium β‐octa‐molybdate outperformed MoO3 and other common molybdenum smoke retarders. Combinations of melaminium molybdates with compounds of copper formed very efficient smoke‐reducing and char‐forming synergistic additive systems for PVC. For example, combining the octamolybdate with a series of different copper compounds consistently gave smoke reductions of about 85% in the flaming mode of the NBS Smoke Chamber at a total additive level of 5 parts per hundred parts of PVC. These large reductions in smoke were accompanied by large increases in the amount of char formed and retained as combustion residues.
Effect of the molecular weight of poly(ethylene glycol), used for the surface treatment of calcium carbonate, on the tensile modulus of filled oriented polypropylene
Authors: Mitsuishi Kazuta , Kodama Soji , Kawasaki Hitoshi
Published: April 2003

A relation between tensile modulus of oriented polypropylene filled with calcium carbonate, and modified with poly(ethylene glycol) (PEG) or alkyl phenyl ether derivatives (APED) of different molecular weights was investigated. Upon stressing, voids appear in the composites material. For systems prepared with unmodified CaCO3, the void volume increases with an increase of filler content. For systems containing modified CaCO3, the void volume is smaller than the one of the reference material and decreases with an increase of PEG or APED molecular weights (which range from 400 to 4000 for PEG). Moreover, the relative modulus of oriented composites, Edc/Edr, are reasonably accounted by the void volume irrespective of filler content and modifier molecular weight, wherein Edc, Edr are respectively the modulus of oriented composites and the modulus of oriented polymer matrix.
Some water‐soluble copolymers from lignin
Authors: Chen R. L. , Kokta B. V. , Daneault C. , Valade J. L.
Published: April 2003

The utilization of lignin materials would be enhanced if lignin properties could be altered through chemical modification. Towards this end, lignosulfonate, recovered from spent pulping liquors, was grafted with acrylamide or acrylic acid, using redox initiation. Study was made of the effects of some reaction variables (such as reaction medium, lignin/monomer ratio, and initiator concentration) on the copolymerization efficiency and on the copolymer characteristics. Lignosulfonate having bivalent counterions yielded better copolymerization results than that having univalent cations. Aqueous solutions of graft copolymers displayed high viscosities, and exhibited promising stability during storage and against shearing, suggesting the potential use of copolymers as water‐thickening agents.
Stress–strain properties of linear aromatic polyesters in the nonlinear viscoelastic range
Authors: Ng Tie Hwee , Williams H. Leverne
Published: April 2003

The stress–strain curves for a series of linear aromatic polyesters were curve‐fitted to yield constant parameters for the one‐dimensional and three‐dimensional constitutive equations for nonlinear viscoelastic properties. Using these constants, the stress–strain curves could be reconstituted somewhat better by the one‐dimensional equations, but the agreement with the three‐dimensional curves was good. The same constants can be used to predict creep and stress–relaxation, the data for which are in a companion paper.
The reversible plasticization of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p‐acetoxybenzoic acid with 1,1,1,3,3,3‐hexafluoro‐2‐propanol
Authors: Shih H. H. , Hornberger L. E. , Siemens R. L. , Zachariades A. E.
Published: April 2003

In recent mechanooptical studies with solution cast films of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p‐acetoxybenzoic acid from 1,1,1,3,3,3‐hexafluoro‐2‐propanol, a volatile solvent with bp 59°C, we observed that the solvent plasticizes and affects considerably the stress–strain behavior of the copolyester at ambient temperature. Whereas a dry copolyester film is typically brittle failing at ≤ 10% strain, a film containing 12% w/w 1,1,1,3,3,3‐hexafluoro‐2‐propanol can be stretched readily to ≥ 300% strain. When the solvent is removed by evaporation or by heating at an elevated temperature (≥ 120°C), the films lose their ductility, indicating that the plasticization is reversible.
Optimization of polymer‐solvent interaction in a multisolvent system by the UNIFAC group‐contribution method
Authors: Tseng Chi‐Ming , El‐Aasser Mohamed S. , Vanderhoff John W.
Published: April 2003

The solubility parameter scheme is an exceptionally useful tool for predicting the solubility behavior of simple polymer systems. However, this scheme is unable to handle well enough complicated systems, such as those involving donor‐acceptor interactions and those containing more than two solvents. More advanced thermodynamic treatments and computer techniques, such as UNIFAC, can be a key to solving these kinds of problems.

The UNIFAC group‐contribution method utilizes a volume parameter and a surface‐area parameter for each structural group and a pair of interaction‐energy parameters for each pair of groups, which can be deduced from experimental activity data. The method was originally derived for mixtures of ordinary liquids and has been extended to polymer solutions by adding a free‐volume correction. The modified UNIFAC method can be used to estimate the activities of solvents in a polymer solution, even when no experimental data are available for the mixture.

In the present study, the UNIFAC method was applied to optimize polymer‐solvent interactions in three‐solvent systems. A three‐dimensional plot, displaying polymer activity as a function of the solvent composition, was constructed for each polymer system. The minimum in polymer activity was used as the criterion for maximum polymer‐solvent interaction. Dissolution rate and solution clarity were used to test the polymer‐solvent interaction experimentally. Comparison of theoretical predictions with experimental results indicated that a better agreement could be obtained by using the UNIFAC method rather than the solubility parameter method.
Short fiber‐reinforced thermoplastic elastomers from blends of natural rubber and polyethylene
Authors: Akhtar S. , De P. P. , De S. K.
Published: April 2003

Thermoplastic elastomer blends of natural rubber (NR) with high density polyethylene (HDPE) and with low density polyethylene (LDPE) were reinforced with short silk fiber. Processing characteristics such as torque and temperature developed during mixing and the effect of processing parameters such as nip gap and number of passes in the mill necessary to secure maximum orientation of the fibers in the blends were studied. A small nip gap and a single pass in the mill were found to give best results. Of the different mixing sequences studied, the sequence where short fibers followed by rubber were added to the molten thermoplastic was found to give a uniform dispersion of fibers. Fiber breakage and the change in aspect ratio of the fibers after mixing were also examined. It was observed that, as a direct consequence of the mixing sequence, each fiber was coated with a layer of thermoplastic. Although the properties improved on the addition of the dry bonding system of silica–resorcinol–hexamethylenetetramine, the comparatively long curing time required for full development of adhesion between the fibers and the matrix proved to be a major disadvantage associated with the incorporation of the bonding system. The tensile and tear properties were substantially enhanced, but the ultimate elongation decreased sharply with increasing loading of short fibers in the blends. The effect of fiber orientation and the development of anisotropy in the properties was also noted. Scanning electron microscopy (SEM) studies of the benzene‐extracted surfaces of the NR/HDPE (high density polyethylene) blends substantiated the theory of fibers behaving like “mechanical anchors” between the rubber and thermoplastic phase. The effect of fiber loading on the tear and tensile properties of the blends of NR/LDPE with varying blend ratios was studied. Most pronounced improvement in the properties on the addition of short fibers was observed in the high rubber blends. As the plastic content in the blends increased, the short fibers were found to have a lesser influence on the properties. SEM photomicrographs of the tensile and tear fracture surfaces indicated the fiber orientations and the effect of orientation, fiber loading, and blend ratios on the nature of fracture.
Environmental degradation of an epoxy resin matrix
Authors: Luoma G. A. , Rowland R. D.
Published: April 2003

With the increased use of graphite‐reinforced composites as replacements for metals has come concerns about durability under harsh environmental conditions. Degradation is expected to begin on the surface and progress toward the center of the resin as a function of time, and reflectance infrared techniques are ideal for monitoring structural changes on surfaces. The present paper describes the application of Fourier transform infrared spectroscopy using internal reflectance elements to the determination of the degree of environmental aging of Hercules 3501−6 resin. The results indicate that degradation occurs via hydrolysis, oxidation, and dehydration reactions at specific locations in the polymer chain. Of special interest is the unique reaction of the tertiary amine of the epoxy portion of the molecule.
Thermal and crystallization behavior of alloys of polyphenylene sulfide and high‐density polyethylene
Authors: Nadkarni V. M. , Jog J. P.
Published: April 2003

The thermal and crystallization behavior of alloys of two semicrystalline thermoplastics, namely, polyphenylene sulfide (PPS) and high‐density polyethylene (HDPE) were studied by differential scanning calorimetry (DSC). The presence of a second component in the alloy was found to influence the nonisothermal crystallization process of both the component polymers. The crystallization temperature of PPS in the DSC cooling scan is significantly affected, whereas there is little variation in case of HDPE in the composition range studied. The morphological changes observed in both PPS and HDPE are similar. These include larger crystallite size, a narrower crystallite size distribution, and a lower degree of crystallinity in the alloys as compared to the homopolymers. The isothermal crystallization of the component polymers in the alloys is significantly different from that of the homopolymer. The composition dependence of the overall rate of isothermal crystallization is explained in terms of the competing processes of nucleation and crystal growth. The results show that blending of a high melting polymer with a low melting polymer accelerates the crystallization of the high melting polymer, even at low levels of about 10% of the lower melting component.
Compatibility studies on blends of poly(ethylene ortho‐phthalate) and poly(vinyl acetate)
Authors: Vazquez‐Torres H. , Cruz‐Ramos C. A.
Published: April 2003

Blends of poly(ethylene ortho‐phthalate) (PEOP), and poly(vinyl acetate) (PVAc), appear to be compatible at all compositions, from visual examination at room temperature and differential scanning calorimetry tests. Both low‐ (PEOP‐1) and high‐molecular weight (PEOP‐2) alloys with PVAc show a single composition‐dependent glass transition temperature (Tg). Some blends show Tg values that are below the Tg for either of the pure polymers. Couchman's equation, with a slight modification, can be used to model Tg behavior. All PEOP‐2 blends with PVAc, phase separate at high temperatures, whereas PEOP‐1–PVAc blends remain miscible under the same conditions. The composition dependence of the blends refractive index shows a deviation from simple additivity rules, and a similar trend is observed in density measurements. When comparing Flory's characteristic parameters for the polymers, compatibility is predicted for PVAc–PEOP blends. In contrast, blends of PEOP and poly(methyl methacrylate) (PMMA), which has a similar chemical structure to that of PVAc are predicted to be incompatible, in agreement with experimental evidence. It is suggested that compatibility is produced because of possible specific interactions between the aromatic group of PEOP and the ester carbonyl on PVAc, which is not sterically hindered as is the corresponding moiety on PMMA.
Drag reduction characteristics of graft copolymers of xanthangum and polyacrylamide
Authors: Deshmukh S. R. , Singh R. P.
Published: April 2003

Graft copolymers of xanthangum and polyacrylamide have been prepared by grafting acrylamide onto xanthangum using ceric‐ion‐initiated solution polymerization technique. These graft copolymers have been tested for their drag reduction effectiveness, shear stability, and biodegradability. It has been shown that the grafting enhances the drag reduction effectiveness and biodegradation resistance of xanthangum considerably.
Characterization of epoxy coatings on steel by reflection/absorption fourier transform infrared spectroscopy. I. Effects of film thickness and angle of incidence
Authors: Nguyen T. , Byrd E. , Tsao A.
Published: April 2003

Films of amine‐cured epoxy coating of varying thicknesses from 100 Å to 2.5 μm on steel have been studied by reflection/absorption Fourier transform infrared spectroscopy (FTIR‐RA). The shape and frequency of several strongly absorbed bands of epoxy have been examined as a function of film thickness and angle of incidence. Compared to transmission spectra, reflection/absorption spectra of epoxy coating on steel show band shifts and distortions of the bands at 1510, 1247, and 1040 cm−1. These effects are more pronounced at increased thickness and at grazing angles. For thin films ( < 100 nm), RA spectral intensity increases with increasing angle of incidence. For thicker films, the relationship is quite complex. The relationship between film thickness and FTIR‐RA spectral peak height of an amine‐cured epoxy coating on steel has also been established.
Microcrystalline chitosan. I. Preparation and properties of microcrystalline chitosan
Authors: Struszczyk Henryk
Published: April 2003

A new type of microcrystalline polymer prepared by aggregation has been discussed. The effect of the parameters of the preparation process on the properties of microcrystalline chitosan in hydrogel and solid forms has been studied using also microscopy and spectroscopy. The product obtained according to the method discussed shows the average molecular weight within a range 2.2–5.0 X 105, WRVs ≈ 260–520%, WRVg ≈ 700–1000%, and CrI up to 95%.
Synthesis, characterization, properties, and derivatives of poly(starch‐g‐(1‐amidoethylene)). II. Measurement of molecular weights by ultracentrifugation
Authors: Meister John J. , Sha Mu Lan , Richards E. Glen
Published: April 2003

Weight‐average molecular weights of samples of poly(starch‐g‐(1‐amidoethylene)) determined by ultracentrifugation range from 0.19 to 3.7 × 106. These data show the copolymer to be a partially permeable coil in aqueous solution and to be formed at significantly higher molecular weights as the mole ratio of cerium(+ IV) to 2‐propenamide in the reaction mixture decreases. Sedimentation coefficients show no indications of distribution broadening from aggregation of copolymer molecules. Buoyancy factor and partial specific volume of the copolymers bracket the values of these variables for the backbone and sidechain.
On the long‐term strength of specimens made of phenol‐formaldehyde press powders
Authors: Natov M. , Vasileva S. , Kotsev G.
Published: April 2003

The study of the long‐term strength (LTS) of polyethylene, poly(vinyl chloride), and polyoximethylene shows that the In τ–σ relation for specimens, undergoing tension, is S‐shaped. Structure changes during the process of deformation may occur in these polymers. However, the structure of spatial‐grid polymers (solidifying phenol–formaldehyde resins, for instance) does not prove to be stress‐sensitive and experiments show that the In τ–σ relation can be described with sufficient accuracy by employing an equation of the form τ = τ0 exp[(U − γσ)/(RT + ασn)].
New aspects in cationization of lignocellulose materials. V. Modification of rotten aspen wood meal with quarternary ammonium groups
Authors: Šimkovic Ivan , Ebringerová Anna , Antal Miroslav , Micko Michael M.
Published: April 2003

Holocelluloses prepared from clear and rotten aspen wood were gradually fractionated with 2.5% NH4OH, 4.5% NaOH, and 17.5% NaOH, respectively. A higher yield of polysaccharides (24.4%) was obtained from the rotten sample in comparison with clear wood (20.9%). Trimethyl ammonium‐2‐hydroxypropyl (TMAHP) derivatives of rotten aspen were prepared by the reaction of wood with 3‐chlor‐2‐hydroxypropyltrimethylammoniumchloride (CHMAC) in alkaline medium. The quantity of TMAHP—hemicelluloses (yield 14.1%) is only slightly lower in comparison with TMAHP—hemicelluloses (yield 15.8%) obtained by modification and subsequent extraction from clear aspen wood meal. The hemicelluloses isolated from the rotten aspen wood meal are contaminated with low molecular cellulose fraction, the degradation products of cellulose attacked by fungi. The lignin component of rotten wood is less intensively attacked by fungi than the polysaccharidic one.