bluuebunny/crossref_metadata_2025 huggingface dataset:
Reverse osmosis separations of some organic and inorganic solutes in aqueous solutions using aromatic polyamide membranes
Authors: Dickson J. M. , Matsuura Takeshi , Blais P. , Sourirajan S.
Published: April 2003

The reverse osmosis separations of some ethers, ketones, aldehydes, monocarboxylic acids, and inorganic salts in single‐solute (55–454 ppm) aqueous solution systems using aromatic polyamide membranes have been studied at 250 psig. It was found that reverse osmosis separation was essentially a function of steric parameter for ethers, and of both polar and steric parameters for ketones, aldehydes, and alcohols. Solute separations for monocarboxylic acids passed through a minimum at a pKa value of ∼4.8. The values for the free‐energy parameter for Li+, Na+, K+, Rb+, Cs+, and F−, Cl−, Br−, I−, and IO3− ions have been calculated for the polyamide membranes used. The above values for cations are negative and those for anions are positive, suggesting that the polyamide membrane surface behaves as if it is positively charged. Further, the data show that the polyamide membrane material is only about 40% as polar as that of the cellulose acetate membrane material studied earlier.
Insoluble starch xanthate: Use in heavy metal removal
Authors: Wing R. E. , Doane W. M. , Russell C. R.
Published: April 2003

Water‐insoluble starch xanthates were prepared by xanthation of highly crosslinked starches under various conditions. After isolation of the products by solvent dehydration, freeze drying, or spray drying, their properties were determined. These products were very effective in removing heavy metals from water.
Effects of ozone and UV on tire cord adhesion
Authors: Iyengar Y.
Published: April 2003

Ozone exposure of resorcinol‐formaldehyde‐latex (RFL) dipped tire cords reduces adhesion because ozone attacks the double bonds in the butadiene component of the rubber latex in RFL and impairs its cocuring with the solid rubber compound. This mechanism also explains: (a) the ineffectiveness of chemical antiozonants or chloroprene latex as RFL additives, (b) the increased ozone sensitivity of RFL adhesion with progressive curing of RFL dip, and (c) the insensitivity to ozone of adhesion with RF‐EPDM adhesives. A major reduction in the rate of adhesion loss in either ozone (50 pphm, 50% RH) or UV (carbon arc, 4 hr) was demonstrated when small amounts of waxes (3% solids basis) were added to the RFL dip. The waxes protect the RFL adhesive by blooming to the surface of the adhesive treated cord.
Bis(diisopropyl) thiophosphoryl disulfide in cis‐1,4‐polyisoprene vulcanization reactions. I. As a sulfur donor
Authors: Pimblott J. G. , Scott G. , Stuckey J. E.
Published: April 2003

Bis(diisopropyl)thiophosphoryl disulfide (DIPDIS) is used as a sulfur donor vulcanizing system for cis‐1,4‐polyisoprene. It is shown that the network structure consists of poly‐ and disulfidic crosslinks at early stages of cure, simplifying at optimum cure to monosulfidic crosslinks. It is thought that pendent accelerator groups are bound to the rubber molecule at early stages of cure, but are subsequently replaced by cyclic sulfidic groups. The good thermal and thermal oxidative aging behaviour of the vulcanizate is due to the formation of zinc diisopropyldithiophosphate (ZDP) in situ.
The effects of fillers, crosslinking agents, and domain size on the physical properties of PE–PCV blends
Authors: McGill W. J. , Fourie J.
Published: April 2003

Blends of polyethylene and poly(vinyl chloride) were prepared on a Brabender Plasticorder, and attempts were made to improve the very inferior physical properties of the product. The blends were found to have domain structures, and it was shown that their physical properties could be improved very considerably if the domain sizes could be reduced drastically. However, in melt blending, there was a limit to the reduction of domain sizes. A noticeable improvement in properties was achieved through the use of various fillers and crosslinking agents. Small changes in crystallite size and percentage crystallinity were observed where certain additives were used. It appeared that the additives that were most effective in enhancing physical properties acted by improving load transfer at the interface between the two polymer phases.
Photodegradable polyethylene
Authors: Pozzi Vittorio , Silvers Arthur E. , Giuffrè L. , Cernia E.
Published: April 2003

Polymer photodegradation can be achieved by introducing carbonyl groups which absorb radiations above the 300 mμ wavelength and thus are sensitized by solar or atmospheric radiations.

We introduced these groups in polyethylene by oximation of aliphatic chain with photoactivated NOCI and hydrolysis of the oxime.

Modified polymers show, during accelerated aging in Weather‐O‐Meter, a constant molecular weight decrease, which is directly proportional to the concentration of carbonyl groups.
Behavior of unstretched nylon 6 fibers subjected to longitudinal and transverse impact
Authors: Cernia E. , Conti W.
Published: April 2003

The impact resistance of unstretched fibers of nylon 6 has been measured at impact velocities in the range of 10–20 m/sec by means of a freely falling dart of variable weight. The analysis was made on fibers with a high moisture content, since samples with low moisture content were brittle, as were unstretched fibers of poly(ethylene terephthalate). The observed impact behavior is in line with that predicted by the stress–strain curves obtained on a dynamometer, although it deviates somewhat in the ultimate properties and when the extent of deformation is small. The behavior for small deformation is discussed and a model is proposed.
Thermal degradation of polymers. VII. Ablation studies on a series of composite specimens containing asbestos fiber with various high‐temperature resin binders
Authors: Kershaw D. , Still R. H. , Bashford V. G.
Published: April 2003

The use of a laboratory ablation test ring for the assessment of tubular asbestos‐reinforced composites is described. Ablation resistance, char depth, smoke, and flash measurements have been made on a series of composites produced using asbestos fiber with a variety of commercially available high‐temperature resin binders. The results have been compared with those obtained from a standard asbestos/phenolic composite and are discussed in terms of the properties of the composite and its components.
Thermal degradation of polymers. VIII. Ablation studies on a series of fiber‐reinforced phenolic resin composites
Authors: Kershaw D. , Still R. H. , Bashford V. G.
Published: April 2003

The use of a laboratory ablation test rig for the assessment of tubular fiber‐reinforced composites is described. Ablation resistance, char depth, smoke, and flash measurements have been made on a series of composites based on a standard phenol–formaldehyde resin incorporating various fibrous reinforcing agents. The results have been compared with those obtained from a standard asbestos‐reinforced composite prepared from the same resin. Results are discussed in terms of the properties of the composite and of the fibrous reinforcing agent.
Thermal degradation of polymers. IX. Ablation studies on composites: Comparison of laboratory test methods with tethered rocket motor firings
Authors: Kershaw D. , Still R. H. , Bashford V. G.
Published: April 2003

The use of a novel laboratory ablation test rig for material selection is described. The results obtained are compared with those obtained from differential thermal analysis, thermogravimetry, and tethered rocket motor test firings.
The influence of gum on the crystalline structure in ramie fiber
Authors: Ray P. K. , Bag S. C. , Chakravarty A. C.
Published: April 2003

The fine structure of decorticated and degummed ramie fibers was studied by x‐ray and optical methods. It has been found that while crystallinity increases, crystallite orientation deteriorates with gradual removal of gum. Optical orientation falls at a more rapid rate, indicating that the major part of the gum resides in the amorphous regions and these regions are more sensitive to the process of extraction of gum.
Contribution to the mechanism of the thiuram vulcanization. I. Polymerization of styrene in the presence of tetramethylthiuram disulfide and natural rubber
Authors: Beniska J. , Kyselá G. , Štaudner E.
Published: April 2003

The influence of the concentration of tetramethylthiuram disulfide (TMTD) on grafting of natural rubber by styrene at 80°, 95°, 115°, and 130°C and constant molar ratio of rubber and styrene was studied. It was found that the dependence Rp = f([TMTD]½) at all followed temperatures goes through a maximum and that TMTD substantially decreases the amount of bound rubber in the graft copolymer. The analysis of the kinetic data and the results of separation of polymer mixtures showed the significant role in the process of the termination reactions of the growing polymer and the rubber radicals with the RS radicals. The derived kinetic relation is in good agreement with the experimental, results and allows calculation of the transfer rate constants of RS radical on rubber.
Studies on physical properties and structure of silk. Glass transition and crystallization of silk fibroin
Authors: Magoshi Jun , Nakamura Shigeo
Published: April 2003

Amorphous silk fibroin with random coil conformation shows endothermic and exothermic peaks and endothermic shift on the DSC (differential scanning calorimetry) curve. The endothermic shift observed at 175°C was due to the glass transition. The exothermic peak at 212°C is recognized to be the crystallization, which later was confirmed by x‐ray diffraction pattern. The endothermic peak at 280°C is shown to be the degradation.
The water curing of a polyurethane resin used as a wool fiber coating
Authors: Beevers R. B.
Published: April 2003

In the industrial application of polyurethane resins to form surface coatings on wool fabrics, the prepolymer resin Synthappret is curred by reaction with water, either as steam or as atmoshpheric water vapor, to form the rubber network. This paper examines changes in the mechanical properties of the resin with cure conditions. It is shown for steam‐cured resin that the initial modulus, the equilibrium swelling in tetrachloroethylene, the Mooney‐Rivlin constant C1, and the average molecular weight of chain segments between crosslinks all reach constant values after 1 hr. However, the resin density and the Mooney‐Rivlin constant C2 show a linear dependence on cure time with no indication of reaching an equilibrium value. It is concluded that although the network is substantially complete after 1 hr of steam cure, there is a continuing pattern of reorganization. The mechanical properties of resin produced by air curing, a much slower process, are consistent with those of a network which has had a longer period of reorganization. The density of air‐cured resin is significantly higher than that of resin prepared by steam curing. Stereoscan electron micrographs of the resin surface reveal a texture which coarsens with prolongation of cure time and also reveal a difference for the two methods of cure.
The effects of melt history, crystallization pressure, and crystallization temperature on the crystallization and resultant structure of bulk isotactic polypropylene
Authors: Reinshagen J. H. , Dunlap R. W.
Published: April 2003

A study of the effects of constant‐pressure isothermal crystallization on polymer structure was conducted in bulk isotactic polypropylene. The investigation was designed to determine the influence of pressure, temperature, and melt history variables on the structure of this bulk polymer. Results demonstrate that the effects of pressure and crystallization temperature can be quite adequately combined into one processing parameter, undercooling (defined as the melting temperature minus the crystallization temperature), by use of the Clausius‐Clapeyron equation. This parameter is demonstrated to be important in determining the kinetics of crystallization and the resultant structure. The moderate to high undercoolings involved in this study are representative of commercial injection‐molding processes, and a number of conclusions regarding commercial processing are made based on these laboratory investigations.
The effect of poly(vinyl bromide) on the layering of cotton fibers in flame‐retardant cotton/polyester blends
Authors: Boylston Eileen K. , Muller Linda L.
Published: April 2003

Cotton and cotton/polyester blends treated with phosphorus‐nitrogen polymers and poly‐(vinyl bromide) for flame retardance were examined in the electron microscope. A considerable amount of the poly(vinyl bromide) was retained by the cotton fibers. Expansion studies indicated that the poly(vinyl bromide) acted either as a morphologic adhesive or as a nonpolar matrix impervious to penetration by methacrylate before swelling.
Crystallization of macromolecular domains
Authors: Aharoni Shaul M.
Published: April 2003

A theory is presented explaining the crystallization of polymers into thin and flat crystals or lamellae. Following the physical cluster theory, the internal and surface free energy of the “amorphous” macromolecular domain is described. Crystallization proceeds through an internal ordering of the domain, the attachment of the partially ordered domain onto a growth face, and, finally, regularization and domain deformation leading to minimization of both internal and surface free energy of the attached domain and its immediate neighborhood. The resultant fold surfaces comprise adjoining intact or deformed domes composed from proximal‐reentry loops. Although arising from an adaptation of the physical cluster theory to describe the macromolecular domain, the free‐energy equations controlling the crystallization process are essentially the same as those describing the primary nucleation in the prevailing crystallization theories. Segregation according to molecular weight is shown to arise from the size‐dependent ability of the domains to improve their internal ordering. Lamellar thickening is shown to follow a critical‐exponent equation dependent on surface free energy. Experimental data from the literature, corroborating the model, are presented.
Some aspects of photo‐initiated grafting to poly(vinyl alcohol)
Authors: Ogiwara Yoshitaka , Yasunaga Toshio , Kubota Hitoshi
Published: April 2003

Three radicals showing singlet, triplet, and quartet, respectively, were observed in the photo‐irradiated poly(vinyl alcohol) (PVA). The signal intensity was increased by the ferric ion (Fe3+) sensitization and the formalization of samples. The triplet component radicals proved to keep fairly stable at room temperature, indicating a high stability of the radical toward warming. Since the Fe3+ sensitization and the formalization of samples brought about a very favorable graft copolymerization, the triple spectrum was assumed to have to do closely with the initiation of graft copolymerization. The spectra of singlet and quartet were assigned to alkoxy and methyl radicals, respectively, originated from the acetyl group remaining in PVA samples and the triplet spectrum to radicals on the α‐carbon of the hydroxyl group in the PVA molecule.
Surface differences and solute permeability in films of certain acrylic–methacrylic ester polymers
Authors: Abdel‐Aziz S. A. M. , Anderson W. , Armstrong P. A. M.
Published: April 2003

The influence of certain aspects of film surface on the diffusion of urea in aqueous solutions through films cast from two acrylic–methacrylic ester polymers has been investigated. Greater rate of permeation by urea occurred in films of both polymers when the lower surface (that in contact with the substrate during casting) was the entry surface for urea than when the upper surface (that in contact with the atmosphere during casting) was the entry surface. Furthermore, this difference between the upper and lower surfaces was more marked in film cast from one of the polymers; and scanning electron micrographs of films of the two polymers revealed differences in gross surface structure. Changes occurred in both upper and lower film surfaces during exposure to urea solution, the lower surface developing larger pores on exposure while smaller pores were observed on the upper side after exposure. The upper‐lower surface differences occurred in films of both polymers. The less hydrophilic film (Eudragit RS100) was associated with lower overall permeation rate for urea and smaller postpermeation mean pore size on both upper and lower surfaces than the more hydrophilic film (Eudragit RL100). The relationship between permeability and changing microscopic appearance of the surfaces is discussed and pictorial evidence of porous structure presented.
Determination of antioxidants in polypropylene by liquid chromatography
Authors: Wims Andrew M. , Swarin Stephen J.
Published: April 2003

Polyolefins, such as polypropylene, are subject to thermal and oxidative degradation and are not used in practical applications unless protected by several antioxidants. Liquid exclusion (LEC) and liquid adsorption (LAC) chromatography have been used to determine the antioxidants in commercial polypropylenes and molded parts. Although a LEC analysis takes as long as 3 hr, LAC separations can be obtained in less than 15 min. Prior to the chromatographic measurements, the antioxidants were extracted from the talc‐filled polypropylene using tetrahydrofuran (THF) and Methylene chloride (CH2Cl2) for the LEC and LAC separations, respectively. Room‐temperature extraction of the additives as a function of time showed that 24 hr was sufficient for THF. A comparison of the LEC chromatogram for a freshly molded part to that for a part which was heat treated showed not only the depletion of certain antloxidants but also showed that the antioxidant distearyl 3,3′‐thiodipropionate (DSTDP) thermally decomposed to give stearyl propionate. Mass spectrometry was used to confirm the identity of the additives in the polypropylene without extraction. The “life” af several polypropylenes was also measured by thermogravimetric analysis and compared to the concentration of DSTDP.
The synthesis and properties of several polypropargylpyridinium and polypropargylbipyridinium polyelectrolytes and their simple and complex tetracyanoquinodimethane ion‐radical salts. I. Electrophysical properties
Authors: Kabanov V. A. , Aliev K. V. , Richmond J.
Published: April 2003

Poly(propargylpyridinium chloride), poly(propargy1‐4‐vinylpyridinium chloride), poly(propargyl‐2,2‐bipyridinium chloride), poly(propargyl‐1‐methyl‐2,2‐bipyridinium methylsulfate chloride), poly(N‐ethyl‐vinylpyridinium bromide), and poly(propargyl‐2‐hydroxyquinolium chloride) were synthesized and a number of simple and complex, tetracyanoquinodimethane ionradical polyelectrolytes were prepared from them. An attempt was made to understand how the molecular structure of these compounds manifests itself in their observed electrophysical properties. Our results show increased electroconductivity in cases of simple and complex ion‐radical polyelectrolytes where the conjugated bond polymer “backbone” is in close proximity to dipyridyl polarizing side groups.
Copolymers of maleic anhydride‐14C and vinyl acetate as standards in an automated titration method for combined anhydride
Authors: Campbell D. R.
Published: April 2003

Copolymers of maleic anhydride and vinyl acetate containing 6 to 54 wt‐% maleic anhydride were prepared in both toluene and methyl ethyl ketone by employing carboxyl‐14C‐labeled anhydride of demonstrated radiochemical purity. The standard copolymers thus prepared were used as reference materials in development of an automated titrimetric method for combined anhydride that had a standard deviation of 1.7 wt‐% at an anhydride level of approximately 50%. The semimicrotechnique described is based on dissolution of the polymer in methyl ethyl ketone–aqueous alkali, addition of an aliquot of this solution to a slight excess of hydrochloric acid, and back titration of the excess of acid with standard alkali. The technique effectively prevents hydrolysis of the acetate groups of the copolymer.
Photo‐induced radicals in glucose and cellobiose
Authors: Kubota Hitoshi , Ogiwara Yoshitaka , Matsuzaki Kei
Published: April 2003

Photo‐induced radicals in glucose and cellobiose, the model compounds of cellulose molecule, were studied by ESR spectrometry. Very poor formation of radicals in glucose as compared to those in cellobiose was observed. However, a spectrum showing a singlet line was easily produced by the use of light involving shorter wavelengths. It was estimated to be due to the radical formed at the reducing C1 position of glucose molecule. By paper chromatography, the photo‐irradiated cellobiose was confirmed to split into glucose through scission of glucosidic bonds in the molecule. The ESR spectrum of the acid‐hydrolyzed cellulose similar to that of the unhydrolyzed sample was a seven‐line spectrum, but the relative signal intensity was here markedly low. This phenomenon seems to be caused by the reduction of amorphous portion in the samples due to acid hydrolysis. It was concluded that the glucosidic bonds in cellobiose and cellulose molecules are very active toward light and play an important role in the radical formation in photo‐irradiated samples.
Shrinkage behavior of oriented PVC by thermomechanical analysis
Authors: Tobias John W. , Taylor Lynn J.
Published: April 2003

This paper describes a novel application of thermomechanical analysis. Observation and measurement of the thermal recovery of stresses induced in oriented PVC by stretching at elevated temperature is achieved by the modification of a commercial TMA instrument. Employment of an electronic signal differentiation system, in combination with this instrument, permits the simultaneous recording of the rate of shrinkage as a function of temperature. Specific examples are given which demonstrate the performance of the instrument and illustrate its application to problems of practical interest, such as effects of stretching and annealing conditions on shrinkage behavior.
Composites obtained by encapsulation and collimation of glass fibers within a thermoplastic matrix by means of polymerization
Authors: Baer Massimo
Published: April 2003

Styrene and acrylonitrile monomers are polymerized in an aqueous suspension system in the presence of chopped glass strands. Under certain conditions, in the course of SAN polymerization, it is possible to align the glass strands in a parallel array (collimate) to form capsules varying in shape from tapes to cylinders. The parallel stacking of glass strands within the capsules allows for high glass loadings and results in glass microfibers completely wetted and imbedded in the polymeric matrix. The mechanism of encapsulation and collimation is discussed and is shown to be critically affected by several factors, the most important being: the preferential wetting of the strands by the monomers, the nature of the glass surface, the monomer composition, the type and concentration of protective colloid used in the suspension polymerization, and the type and intensity of agitation. The fiber glass composites obtained by encapsulation are found to have mechanical properties superior to those obtainable by conventional commercial routes.
Gas permeation of polymer blends. I. PVC/ethylene–vinyl acetate copolymer (EVA)
Authors: Shur Young J. , Rånby Bengt
Published: April 2003

The transport behavior of O2 and N2 were studied for series of physical blends of PVC with EVA having different vinyl acetate (VAc) contents in the EVA (45 and 65 wt‐%) and using different milling temperatures (160° and 185°C). The polymer blends were further characterized by dynamic mechanical measurements, density measurements, and x‐ray diffraction. At higher VAc content in EVA and with higher milling temperature, the rate of permeation (P) and the rate of diffusion (D) decrease, and the activation energy of D (from Arrhenius plots) increases. Furthermore, the experimental density values of PVC/EVA‐45 blends agree well with calculated values, assuming volume additivity of the two components, while those of PVC/EVA‐65 blends are higher than the calculated densities. These results are interpreted as due to denser packing of polymer molecules and increased PVC‐EVA interaction at higher VAc content and with higher milling temperature, indicating better compatibility between the blend components. The x‐ray diffraction data give no evidence of crystallinity. Sharp increases in P and D values at about 7.5% EVA (by weight) are found for PVC/EVA‐45 blends (in agreement with our previous work) but not for PVC/EVA‐65 blends. This is interpreted as due to a phase inversion at increasing EVA content in the former blends but not in the latter blends. The dynamic mechanical measurements show that the PVC/EVA‐65 blends milled at 160°C behave largely as semicompatible systems with maximum interaction between the two polymers at compositions of about 50/50 by weight.
Removal of alcohols, amines, and aliphatic acids in aqueous solution by NS‐100 membrane
Authors: Fang Herbert H. P. , Chian Edward S. K.
Published: April 2003

Removal of alcohols, amines, and aliphatic acids in single‐solute aqueous solution in the concentration range from 0.001 to 0.01M have been studied using the NS‐100 membrane. All the tests were conducted at 600 psig, 25°C, and a flow rate of 0.30 gpm. The mechanism of solute separation by the NS‐100 membrane differs from that of the cellulose acetate membrane. There was no significant correlation between the removal and the hydrogen bonding ability of the organic solute. Instead, for a given organic solute, its removal increases with the increases in the degree of crosslinkage of the skin layer of NS‐100 membrane, and is proportional to its degree of ionization (or degree of dissociation). For organic compounds having a same functional group, the removal of a compound increases with the increase in molecular weight and/or molecular branching. All of these are attributable to the relative nonpolarity and the anion exchanger characteristics of the membrane as well as to the steric resistance for the solute to permeate through the membrane.
Electric field‐induced piezoelectricity in polymer film
Authors: Zimmerman R. L. , Suchicital C. , Fukada E.
Published: April 2003

An apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d′ − id″ for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (ϵ + κ)/G where ϵ is the dielectric constant, κ is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field‐induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95°C followed by cooling to room temperature, maintaining a constant d.c. basis on a poly(vinyl chloride) film, piezoelectricity is observed at null d.c. field, which suggests the introduction of a residual polarization in the films.
Polymerization of organic compounds in an electrodeless glow discharge. V. Amines and nitriles
Authors: Yasuda H. , Bumgarner M. O. , Hillman J. J.
Published: April 2003

Polymerizations of amines and nitriles in a glow discharge generated by inductive coupling of 13.5‐MHz radio frequency are investigated by employing the measurement of closed‐system pressure change. It is found that nitrogen in those compounds are incorporated into polymer in a nearly stoichiometric manner and that the polymerization of those compounds are very much similar to that of hydrocarbons. Hydrogen detachments, opening of double bond and/or cyclic structure, opening of triple bond including CN, and opening of aromatic and heteroaromatic structures contribute to polymerization of amines and nitriles.
The effect of photodegradation of polystyrene on its permeability characteristics
Authors: Greenwood R. , Weir N. A.
Published: April 2003

The diffusion (D) and permeability (P) coefficients for 14CO2 in polystyrene films which had been irradiated by short‐wave ultraviolet (253.7 nm) radiation under vacuum and in oxygen were determined in the temperature range of 20° to 55°C. Both D and P decreased with increasing exposure, the vacuum‐irradiated sample showing significantly greater decreases, presumably on account of a larger extent of crosslinking which was possible in the absence of oxidation. A good correlation was observed between crosslinking and decreasing P and D values. The solubility coefficients for all irradiated samples increase with increasing dose. Activation energies for diffusion increase with increasing irradiation, particularly for the vacuum‐irradiated samples. Reductions in P and D values are interpreted in terms of free‐volume decreases due to crosslinking and other modifications, while the increasing activation energies are attributed to the increasing energy requirements for creation of free volume in modified polymers.
Rheogoniometry of molten blends of polystyrene and styrenic ionomers
Authors: Iwakura Kenji , Fujimura Toshikazu
Published: April 2003

The rheological properties of the molten blends between polystyrene (PS) and styrenemethacrylic acid copolymer (S‐MAA) or its metallic salts were determined with a Weissenberg rheogoniometer, and the mixed structure and the processability were discussed. Results were as follows. (1) The viscosities of the salts increased and the compliances decreased with increasing density of ionic crosslinkings. (2) The viscosities of the molten blend between PS and S‐MAA or its salt increased steeply even at lower shear rate and the Newtonian flow region was not observed. (3) This shear‐sensitivity of viscosity in low shear rate region increased with increasing temperature. (4) The effect of temperature on the viscosity of these blends deviated from the simple Arrhenius plot. (5) Some network structures are suggested for the blends between PS and S‐MAA salts but they may be broken eventually under high shear rate or at high temperature. Therefore, the mixed structures and the flow mechanisms of these molten blends seem to change with shear or temperature.
Surface fluorination of transparent polymer film
Authors: Shimada Junichi , Hoshino Mitsutoshi
Published: April 2003

Transparent polymer film was fluorinated by contacting with fluorine gas. The fluorinated layer depth was determined from the visual spectrum. The relation between fluorinated depth d and reaction time t was represented by d = k·t½. This result indicates that fluorine diffusion plays a predominant role in forming the diffusion profile. The apparent activation energy of fluorine gas diffusion into polystyrene (PS) and polycarbonate (PC) was 2.8 kcal/mole and 6.6 kcal/mole, respectively. The refractive index distribution from surface to center, which corresponds to the fluorine content in the layer, was determined by interference microscopy. PS and PC showed nearly stepwise change of refractive index. On the other hand, poly(methyl methacrylate) showed a gradual change. These results are compatible with fluorine analysis data and IR spectra of the fluorinated polymers. On the basis of these results, antireflecting layers on plastic lens or plate, plastic optical fiber, or fiber sheet were formed.
Absorption of water by graft copolymers of cotton with methyl methacrylate using high‐resolution NMR
Authors: Mousa A. M. , Aziz Akram
Published: April 2003

Graft cotton fibers containing poly(methyl methacrylate) were initiated by ultraviolet radiation. High‐resolution NMR was used to study the nature of water absorption by these graft copolymers and also by mixtures of cotton fibers with the corresponding homopolymers. Results obtained help in investigating the structure of the copolymers and to differentiate, in a simple way, between true graft copolymers and mechanical mixtures or coated fibers.
Chemical modification of acrylonitrile copolymers: Reaction of cationic copolymers with ethylene oxide
Authors: Courtney J. M. , Gilchrist T.
Published: April 2003

Copolymers of tertiary amines have been reacted with ethylene oxides gas. The reaction induces low temperature cyclization and increases polymer hydrophilicity. When the co‐polymer is in film form, water permeability is dependent on ethylene oxide processing time and temperature.

The behavior of the copolymer films when treated with ethylene oxide is contrasted with the effects due to thermal treatment of acrylonitrile copolymers.
Stress wave‐initiated fracture in amorphous thermoplastics
Authors: Hagerman E. M. , Mentzer C. C.
Published: April 2003

Several brittle thermoplastic materials, including polystyrene, SAN, and PMMA, were tested in tension using a spectrum of testing rates up to 15,000 in./min (630 cm/sec). At test velocities below 7000 in./min (294 cm/sec), the materials behaved “classically” with strength properties increasing, elongation decreasing, and single fractures generally forming. At rates between 7000 and 9000 in./min (294 and 378 cm/sec), a transition from classical to stress wave‐initiated fracture was observed. The mechanical properties, the nature of the fracture, and the nature of the crazing preceding fracture were shown to be profoundly affected when the materials were strained at rates sufficient to initiate stress wave fracture. Under these conditions, the apparent load‐carrying capabilities of the materials were reduced by an order of magnitude.
Changes in the morphology of cast nylon 6 through copolymerization
Authors: Kubota Hideo , Nowell Joseph B.
Published: April 2003

Correlations were made between several physical and mechanical properties and crystal morphology for copolyamides composed of caprolactam and either capryllactam or laurolactam as a minor comonomer. Incorporating a comonomer into the nylon 6 chain decreases the crystallinity and crystal size and, in addition, depresses the melting point of the polymer much more than predicted by the classical Flory theory on random copolymers. This fact, along with the change in the x‐ray diffraction patterns, indicates that small amounts (up to 10 mole‐%) of comonomer can enter the polymer crystals without any basic change in the α‐form crystal structure. The variation of copolyamide densities with comonomer content also supports this theory. The initial moduli of the copolyamides, when tested above their glass transition temperatures, obey a linear relationship with the reciprocal of the amorphous content of the polymers. The impact strength increases dramatically with decreases in crystallinity and crystal size. Some of these materials have extremely large ultimate elongations and have glass transition temperatures below room temperature.
The mechanism of the thermal degradation of aromatic amine‐cured glycidyl ether‐type epoxide resins
Authors: Paterson‐Jones J. C.
Published: April 2003

A mechanism is proposed for the thermal degradation of aromatic amine‐cured glycidyl ether‐type epoxide resins which is based on the results of previous work in this field. The significance of the degradation mechanism to the thermal stability of aliphatic amine‐cured epoxides and aromatic amine‐cured cycloaliphatic epoxides is discussed.
The mechanical properties of single wood pulp fibers. III. The effect of drying stress on strength
Authors: Kim C. Y. , Page D. H. , El‐Hosseiny F. , Lancaster A. P. S.
Published: April 2003

An experimental study has been made of the effect of drying tension on the tensile strength of single fibers from several wood species pulped in various ways. Some pulps are strengthened by drying stress, whereas others show no response. These apparently contradictory results are explained in terms of the effect of drying stress on the morphologic features responsible for strength. In part I of this series, it was shown that fiber strength is controlled by the fibril angle of the S2 layer and the extent and severity of defects. These defects are mostly the local disturbances of fibril alignment termed “dislocations”, “slip‐planes”, or “microcompressions”. It appears that drying stress strengthens fibers both by reducing the fibril angle and by aligning the fibrils in the dislocated regions. This is only possible, however, if the matrix between the fibrils can flow in shear under the applied stress. Thus, strengthening is possible for fibers of high hemicellulose content, the matrix of which flows readily in the water swollen state. Strengthening does not occur, however, for predried kraft fibers or alkali‐extracted holocellulose, for which the matrix is well bonded and insufficiently swollen.
The xanthate method of grafting. III. Effect of lignin content on the graftability of wood pulp
Authors: Hornof V. , Kokta B. V. , Valade J. L.
Published: April 2003

Several commercial wood pulps of different chemical origin and with various lignin content were copolymerized with acrylonitrile using the xanthate grafting process. A number of experiments were carried out to evaluate the effects exerted by the residual lignin and by other wood components on the grafting reaction. The results obtained show that graft copolymers can be prepared in good yields with pulps containing as much as 23% lignin. With the aim to investigate the effect of lignin in more detail, two series of pulps were prepared by delignification of a crude sulfite pulp and a crude Kraft pulp to different levels of lignin content. Sodium chlorite was used as a bleaching agent. Copolymerization results obtained with these pulps indicate some fundamental differences in behavior between sulfite and Kraft pulps. In both cases, the copolymerization is afflicted by a short inhibition period whose duration, however, does not depend on the lignin content in the pulp.
The coupling of deformations in a class of viscoelastic solids to temperature changes
Authors: Rigbi Zvi
Published: April 2003

A class of viscoelastic materials is defined by the parametric constitutive equations σ = σ(ε,t) and T = T(ε,t). It is shown that the creep rates and relaxation rates of such materials are determined by their thermal properties and the ambient temperature, and that the assumptions of constant stress of strain respectively and constant temperature are incompatible.
Morphologic changes on processing of polyblends of saturated rubber‐reinforced plastics
Authors: Koiwa Seiji
Published: April 2003

Laminar peeling is often observed on the injection‐molded surface of the saturated rubbermodified plastics (EVASTAN), which are prepared by copolymerizing styrene and acrylonitrile in the presence of ethylene–vinylacetate copolymer (EVA). However, the delamination rarely occurs upon higher grafting and crosslinking EVASTAN with preactivated EVA, which has pendent unsaturation. The microstructure of these EVASTAN resins was observed by electron microscopy at the end of polymerization and after processing. It was found that the delamination is caused by the agglomeration and deformation of the EVA particles and is prevented by increasing the stability of the particles by grafting and crosslinking.
Protein ultrafiltration: an experimental study
Authors: Bellucci Francesco , Drioli Enrico , Scardi Vincenzo
Published: April 2003

An experimental study was carried out on the ultrafiltration (UF) of protein‐containing solutions under different conditions, as compared with a solution of a linear synthetic polymer. Three different fluidynamic regimes were investigated, namely, unstirred batch system, stirred batch system, and recirculating system. The results obtained substantially agree with the predictions of the gel polarization model. A significant effect of the electrolytes on the UF flux has been observed, which can be attributed to solute–solute interaction. The influence of different UF membranes has also been investigated.
Azobisisobutyronitrile‐induced vinyl graft polymerization onto nylon 66
Authors: El‐Rafie M. H. , Khalil M. I. , Hebeish A.
Published: April 2003

The presence of nylon 66 during polymerization of methyl methacrylate (MMA) under the influence of azobisisobutyronitrile (AIBN) produces a nylon‐PMMA graft copolymer. The copolymerization reaction is greatly influenced by the reaction medium, temperature and time of the reaction, concentration of MMA, and addition of metallic ions. Polymerization in pure organic solvents brings about little or no grafting. Incorporation of water into the polymerization system enhances grafting significantly. A reaction medium of a water/solvent mixture in a ratio of 75:25 constitutes the most favorable medium for the grafting reaction in question. Of the solvents examined, methanol, ethanol, propanol, isopropanol, and acetone work extremely well. Increase in reaction time is accompanied by an increase in the graft yield. The same holds true for the reaction temperature; the graft yield is much higher at 70 than at 50°C and follows the order 70°C > 60°C > 50°C. Increasing MMA concentration also causes considerable enhancement of the graft yield. The presence of 0.01M cupric sulfate in the polymerization system brings about an eightfold increase in the graft yield, whereas the presence of ferric sulfate at the same concentration causes a sixfold increase. The mode of initiation of grafting seems to be different in the presence of metallic ions than in their absence. A mechanism for the reactions involved in the both cases has been proposed.
The effect of skin‐core morphology on the impact fracture of poly(butyline terephthalate)
Authors: Hobbs S. Y. , Pratt C. F.
Published: April 2003

Variations in the skin‐core morphologies of injection‐molded poly(butylene terephthalate) samples have been characterized as a function of molding conditions by optical microscopy, x‐ray diffraction, and density measurments. Samples molded from 450 and 510°F melts at mold temperatures ranging from 70 to 250°F were found to have nonspherulitic skins whose thicknesses varied inversely with processing temperature. Very little orientation was observed in the skin or core regions of the molded bars. Density profiles are presented.

Impact data obtained on bars with molded‐in notches demonstrate that significant increases in impact strength are observed with increasing skin thickness, although the maximum skin thickness remains less than a few hundred microns. This behavior persists through the ductile brittle transition which is centered at ∼50°C.

Fracture surface micrographs and high‐speed stress‐strain curves are presented and used to give a qualitative description of the fracture process. At room temperature the samples appear to deform elastically up to the point of fracture, while at higher temperatures extensive shear deformation is observed. In each case failure ultimately occurs via a craze–crack mechanism.
Use of solubility parameters for the preparation of hemodialysis membrances
Authors: Chawala A. S. , Chang T. M. S.
Published: April 2003

The Solvent mixtures of acetone and ethanol (swelling agent) were selected for the preparation of cellulose acetate dialysis membranes using the solubility parameter concept. Increased concentration of ethanol or decreased concentration of cellulose acetate in the formulation resulted in membranes with higher dialysis rate constants but with decreased tensile strengths. The membranes prepared from 20 g of cellulose acetate per 100 ml of mixed solvent of 59.9 mole‐% acetone and 40.1 mole‐% ethanol were comparable to Cuprophane membrane but were better than those prepared by using formamide as a swelling agent.
Noise and vibration damping with latex interpenetrating polymer networks
Authors: Grates J. A. , Thomas D. A. , Hickey E. C. , Sperling L. H.
Published: April 2003

Damping systems based on interpenetrating polymer networks (IPN's) provide noise and vibration attenuation over broad temperature and frequency ranges. Semicompatible latex IPN's are employed in both extensional and constrained layer configurations. The damping behavior of IPN's of compositions poly(ethyl methacrylate)/poly(n‐butyl acrylate) [PEMA/PnBA], poly(ethyl methacrylate–co–ethyl acrylate)/poly(n‐butyl acrylate–co–ethyl acrylate) [P(EMA–co–EA)/P(nBA–co–EA)], and poly(vinyl chloride)/poly(butadiene–co–acrylonitrile) [PVC/P(B–co–AN)] were investigated and compared to both commercially available materials and to theory. The damping of both the PEMA/PnBA and the P(EMA–co–EA)/P(nBA–co–EA) IPN's in a constrained layer configuration was significantly better, over a broad temperature range of −10° to 60°C, than the commercial materials. In addition, the P(EMA–co–EA)/P(nBA–co–EA) IPN was found to be effective in damping phenolic‐impregnated Kevlar cloth laminates. A reduction of 10 dB in impact noise resulted with a 6–8% by weight layer inserted between the Kevlar‐phenolic panels. The relationship between the peak damping temperature of a constrained layer system to maximum tan δ along with that of an extensional damping system to maximum E″ was also demonstrated. Although the amount of damping predicted by the theory approached that found experimentally, sufficient differences existed such that the exact detail of the damping curve was not described.
Diffusion of stabilizers in polymers. II. 2‐hydroxy‐4‐octoxybenzophenone in polyolefins
Authors: Johnson M. , Westlake J. F.
Published: April 2003

The migration of radioactively labeled 2‐hydroxy‐4‐octoxybenzophenone in a number of polyolefins was investigated over the temperature range 36–75°C. The rates of diffusion in the polymers studied were found to decrease in the order low‐density polyethylene > high‐density polyethylene ∼ isotactic polypropylene, the activation energies being approximately 17, 36, and 24 kcal/mole, respectively. The results of the present study were found to be in qualitative agreement with those previously determined for the same stabilizer/polymer systems, quantitative differences being attributed to the different methods of sample preparation and the resulting differences in the morphological structures of the test specimens. The calculated solubilities of the substituted 2‐hydroxybenzophenone in the various polymers were substantially higher, at a particular temperature, than the corresponding values previously determined for 2,4‐dihydroxybenzophenone, being 1.4, 0.4, and 0.8 wt‐% for low‐density polyethylene, high‐density polyethylene, and polypropylene, respectively at 75°C. Studies to determine the rate of loss of the stabilizer from polymer samples immersed in water resulted in extremely low rates of extraction, in contrast to those found for 2,4‐dihydroxybenzophenone, as a result of the octoxy substituent and the resulting increase in compatibility between the stabilizer and polymer.
Graft copolymerization of nylon 6 with methyl methacrylate using dimethylaniline/Cu2+ ion system
Authors: El‐Rafie M. H. , Hebeish A.
Published: April 2003

The ability of dimethylaniline (DMA)/Cu2+ ion initiator to induce grafting of methyl methacrylate (MMA) onto nylon 6 was investigated under a variety of conditions. It was found that the graft yield is dependent on the concentration of the Cu2+ ion, of DMA, and of MMA. While the graft yield increases as the monomer concentration increases, there are optimal concentrations of DMA and Cu2+ ion. Below or above these concentrations, lower grafting occurred. The type of cupric salt also affects grafting to varying degrees. While the presence of CuSO4 and Cu(NO3)2 accelerates grafting, the presence of CuCl2 offsets the reaction. Increasing the reaction temperature and reaction time favorably influences grafting. Addition of acetic acid enhances grafting, whereas formic acid decreases grafting. Preswelling of nylon with formic acid leaves the susceptibility of nylon toward grafting practically unaltered. Studies of the copolymerization reaction was not confined to the graft yield but was extended to homopolymer formation and total conversion.
Permeability of polymer films to sulfur dioxide at low concentration
Authors: Davis E. G. , Rooney M. L. , Larkins P. L.
Published: April 2003

A new apparatus is described for measuring the permeability of polymer films to sulfur dioxide at partial pressures down to 2 Pa. It employs a permeation tube technique for establishing the partial pressure gradient and a detection system based on the absorption of light at 213.8 nm. Data on the permeability to sulfur dioxide of a range of polymer films are presented and discussed.