bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of photoinitiated degradation of polycarbonate by cerium (III) overcoating
Authors: Klein Andrew J. , Yu Hyuk , Yen William M.
Published: April 2003

Photodownconversion of UV radiation incident on a polymeric substrate, polycarbonate, into visible and IR region is effected by coating the substrate with cerous chloride (CeCl3)/poly(vinyl alcohol) complex whereby photolytic degradation of the substrate is significantly inhibited. Thus it appears that cerous ion coating serves as an effective UV screener. The testing method consists of exposing the coated and naked substrate films to a medium intensity UV source with a cutoff filter below 280 nm for different intervals and determining their optical transmission characteristics. Some of the cerous ion coated films were further overcoated with polyvinyl acetate in order to prevent ion leaching by water. The final product retains the visible and IR transmittance of untreated polycarbonate film, and when the optimum composition of CeCl3 in poly(vinyl alcohol) is coated, its transmission spectrum is barely changed even after 24 hr of UV irradiation. The object is to develop inexpensive solar glazing materials which can last up to 20 years without deterioration of their optical and mechanical properties upon solar irradiation.
Phase separation behavior of rubber‐modified epoxies
Authors: Wang T. T. , Zupko H. M.
Published: April 2003

The compatibility and phase separation behavior of mixtures of the diglycidyl ether of bisphenol A and carboxyl‐terminated butadiene‐acrylonitrile copolymers were studied by means of light transmission, viscosity measurements, and optical microscopy. Cloud point measurements of the blends prior to curing showed a strong influence of acrylonitrile on the miscibility behavior, especially near the critical composition of the system. In addition, the cloud point curves showed a highly skewed shape which turned out to be particularly favorable to the formation of a rigid but tough two‐phase structure. Blends subjected to isothermal cure at 120°C were found to begin phase separation at a progressively shorter time with increase in the copolymer content. Furthermore, while the phase domains tended to cease growing at the time of gelation, the composition within the sample continued to change well beyond the gel point.
Studies on synthetic polymer plates with high surface energy. I. Diallyl phthalate‐unsaturated carboxylic acid system
Authors: Ohtsuka Yasuji , Kaneko Norio , Takami Fumio
Published: April 2003

A new preparation technique of the polymer plate with high water wettability and sufficient mar resistance was proposed. The gel plate resulting from the prepolymerization of diallyl compound (M1), diallyl phthalate (DAP), in a casting cell was immersed in an aqueous solution of unsaturated carboxylic acid (M2), acrylic acid (AA), and methacrylic acid (MAA), at a specific temperature for a specific time. M2 was copolymerized with the remaining M1 in the region near the surface of the gel plate, and polymer plates with the following characteristics were obtained: for DAP–AA system, θi (contact angle of the alkali‐treated plate) = 10.5° and mar resistance (for the alkali‐treated plate at a dry state) = 70 g; for DAP–MAA system, θi = 8.3°, and mar resistance = 65 g.
Grafting vinyl monomers into nylon‐6. II. Graft copolymerization of methyl methacrylate onto nylon‐6 by hexavalent chromium ion
Authors: Nayak Padma L. , Lenka Subasini , Mishra Munmaya K. , Tripathy Atanu K.
Published: April 2003

The feasibility of chromium(VI) to induce graft copolymerization of methyl methacrylate onto nylon‐6 was investigated in the presence of nitrogen. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, solvents, inorganic salts, and redox system. The graft yield increases significantly by increasing the monomer concentration. The graft yield increases with increase of [Cr(VI)] up to 0.025 mole/liter. With further increase of [Cr(VI)], the graft yield decreases. The increase of acid concentration up to 0.395 mole/liter results the increase in graft yield. Beyond this concentration the graft yield decreases. The graft yield increases with increase in temperature up to 55°C and thereafter it decreases. The graft yield is medium dependent. The graft yield increases with increasing thiourea concentration upto 0.0025 mole/liter but beyond this concentration, the percentage graft yield decreases. A suitable kinetic scheme has been proposed and the rate equation has been evaluated.
Spontaneous ignition of styrene‐butadiene rubber
Authors: Emmons Howard W.
Published: April 2003

Laboratory experiments with small samples of styrene‐butadiene rubber show a complex thermal history which suggests the presence of both endothermic and exothermic processes. The suggested mechanisms are shown to be qualitatively correct by computer simulation. Both the laboratory tests and two larger scale tests show that styrene‐butadiene rubber of the present composition will not spontaneously ignite if its surroundings are held at a sufficiently low temperature below about 220°C (428°F).
Thermally stimulated depolarization current studies on strain‐induced relaxations in polymers
Authors: Hong Jauwhei , Brittain J. O.
Published: April 2003

Thermally stimulated depolarization current (TSD) method has been used to study the molecular relaxation from room temperature up to the glass‐transition temperature for three plastically deformed polymers. A well‐defined distinct α′ peak has been observed in the vicinity of 70°C for polycarbonate, polysulfone, as well as poly(ethylene terephthalate), that had been annealed above Tg and subsequently cold‐rolled. Since this relaxation is not observed after the initial measurements, it is a nonequilibrium relaxation. In the case of polycarbonate, the nonreversible α′ process had an activation energy ranging from 1.22 to 1.75 eV and an intensity proportional to the degree of deformation resulting from cold‐rolling. The spontaneous polarization in the rolled material was believed to originate from the initial anisotropy which was subsequently enhanced by the rolling process. Density measurements, as well as the birefringence observation, have been performed on the rolled specimens. All the studies led to the conclusion that the molecular motion responsible for this α′ peak was the disorientation of local chain segments from their aligned conformation frozen in during the cold‐work.
Dual permeation of acid dyes through nylon 6 membrane
Authors: Tak Tae‐Moon , Sasaki Tamotsu , Komiyama Jiro , Iijima Toshiro
Published: April 2003

Permeation of acid dyes in nylon 6 membrane was measured and analyzed by the dual sorption and diffusion mechanism, comprising partition and Langmuir‐type modes. The results were compared with our previous work on diffusion in the same system by the film roll method. Diffusion coefficients of both dye species were found to be similar in magnitude.
Thermal properties of photo‐oxidized nylon 6 fibers
Authors: Fujiwara Yasuharu , Zeronian S. Haig
Published: April 2003

Nylon 6 fiber begins to increase in weight at about 180°C when heated in oxygen. The increase is attributed to an uptake of oxygen resulting from thermal oxidation. A similar weight increase is not found in photo‐oxidized nylon 6 on heating in oxygen. It appears that nylon 6 tends to form volatile compounds more easily on heating after photodegradation. Changes detected by differential thermal analysis and also by thermomechanical analysis after nylon 6 has been exposed to sunlight are discussed primarily in terms of the supramolecular structure of the fiber.
Cresylic soluble polyimides
Authors: Sheffer Howard
Published: April 2003

Polyimides are prepared by reaction of dianhydrides with aromatic diamines under dehydrating conditions to insure conversion of the polyamic acids to polyimides. Cresylic acid solubility is observed only for cyclopentane dianhydride and benzophenone dianhydride. Most of the batches are made from BPDA, since it is the preferred dianhydride for thermal stability. Of 19 aromatic diamines only 2,4‐ and 2,6‐diaminotoluene, 2,4‐diaminoanisole, 4,5‐dimethyl‐1,2‐phenylene diamine and 1,5‐diamino‐4,8‐dihydroxyanthraquinone contribute a great deal toward making soluble polyimides of BPDA. 2,4‐Diamino‐acetanilide when used as the only diamine also gives a soluble polyimide with BPDA. The solubility of polyimides can be correlated with their solubility parameters, their symmetry, and their tendency to hydrogen bond.
Effect of a methyl substituent in the polymerization–crosslinking treatment of cotton with NMMA and NMA
Authors: Shih Frederick F. , Rowland Stanley P.
Published: April 2003

An estimation of structures of reagent residues in cotton fabrics treated with N‐methylolmethacrylamide (NMMA) and N‐methylolacrylamide (NMA) and comparison of textile performance of the NMMA–cotton and NMA–cotton provide the basis for insight into the structure–performance relationship in these fabrics. The α‐methyl substituent, which constitutes the difference between NMMA and NMA, accounts for an altered composition of reagent residues in the treated cotton. The more attractive balance of strength–abrasion resistance with resilience for the NMMA–cotton seems to be a result of a lower degree of covalent crosslinking, which appears compensated by a higher elastic modulus in the NMMA network polymer.
Sulfonation studies of copolymers, graft copolymers, and polymeric gels using phase transfer catalysts
Authors: Paul Swaraj , Rånby Bengt
Published: April 2003

A new sulfonation method using phase transfer catalysts was applied to sulfonate a number of polymer matrices in an aqueous two‐phase system. The polymer matrices included in this study are (1) styrene (Sty) and acrylonitrile (AN) copolymers with glycidyl methacrylate (GMA), (2) graft copolymers of cellulose with GMA, and (3) polystyrene and polyacrylate gels containing GMA as comonomer. The presence of polar groups such as AN in the polymer matrix makes the sulfonation easier. For cellulose graft copolymers, the extent of sulfonation was not much affected by the phase transfer catalysts, presumably due to the high polarity and high water uptake capacity of the cellulose base. For other polymer gels, the following factors influence the extent of sulfonation: (1) the method of gel synthesis, i.e., gels synthesized by delayed addition of GMA give a higher degree of sulfonation; (2) the nature of the crosslinking agent, i.e., gels with ethylene glycol diacrylate (EGDA) gives a higher degree of sulfonation than gels with divinylbenzene (DVB); (3) the pore size of the gels, i.e., gels with larger pore sizes gave higher degree of sulfonation; (4) increasing polarity of the backbone structure of gels favors increased sulfonation, e.g., MMA–GMA–EGDA gels give 54% sulfonation, whereas Sty–GME–EGDA gives only 38%.
Flow through regular polygonal channels
Authors: Frenkel R. A. , Lenk R. S.
Published: April 2003

A general method for analyzing viscous flow through regular polygonal channels is presented, based upon the assumption that the flow rate through regular polygonal sections equals that through circular sections of the same area. In addition we offer alternatives which apply specifically to equilaterial triangles and to squares.
Novel oxidatively drying urea resin. II. Surface coating properties of N,N′‐bis(methoxymethyl) urea‐based air‐drying resins
Authors: Toivonen Hannu
Published: April 2003

The surface coating properties of the air‐drying urea resins prepared by polycondensating N,N′‐bis(methoxymethyl) urea (BMMU) with trimethylolpropane diallylether (TMPDA) and 2‐ethylhexanol (2EH) were studied. It was found that the thinnability of the ethanolic resin solutions with water decreased with increasing molecular weight and the degree of modification of the resins with TMPDA and 2EH. The viscosity of the ethanolic resin solutions increased with the molecular weight but was independent on the resin's degree of modification. The drying performance was improved with increasing molecular weight and decreasing modification with 2EH. The hardness of the paint films was proportional to the modification of the resins with TMPDA and the molecular weight. 2EH led to the plasticization of the coatings. The water resistance of the paint films was improved with increasing modification with 2EH and molecular weight of the resin. The analysis of the elastic properties of the hardened films was not possible due to the scatter of the experimental data. The comparison of the amino resin paints to some commercial paint products indicated that BMMU‐based resins having good drying performance and adequate water resistance at the same time can be prepared. Neutral ethanolic and aqueous ethanolic resin solutions were found to have a good storage stability as determined by following the viscosities of the solutions and the hydrolysis resistance of the resins.
The accessibility of sulphonic acid groups in basic dyeable polyester fibers. II. The influence of plasticization on the ion exchange process
Authors: Ingamells W. , Lilou S. H. , Peters R. H.
Published: April 2003

The exchange of the sodium ions of the sodium sulphonate group in anionically modified polyester fibers has been measured. The accessibility of the sulphonate groups in the polymer is greatly improved by plasticization and is independent of the size of the exchanging ion.
Void formation in a filled SBR rubber determined by small‐angle X‐ray scattering
Authors: Kaneko S. , Frederick J. E. , McIntyre D.
Published: April 2003

Two commercial styrene‐butadiene (SBR) latexes were used to prepare a model filled material consisting of glassy SBR filler particles about 1000 Å in diameter embedded in a rubbery SBR matrix crosslinked by γ‐radiation. When transparent specimens of this material were extended, voiding occurred, as evidenced by stress whitening and greatly enhanced X‐ray scattering intensity. More voids were formed at higher rates of extension, but voids disappeared when specimens were relaxed. The effects of filler content and cure time of the matrix on the size and number of voids formed were determined by low‐angle X‐ray scattering for a constant extension rate and a constant extension ratio λ = 1.6. The number of voids measured by X‐ray scattering intensity decreased rapidly with time over the 3‐h period of measurement. The number of voids remaining 1 h after extension increased about 40 times as filler content was increased from 15% to 50%. Increasing the cure time from 24 to 96 h increased the number of voids about four times. In contrast, the radius of gyration of the voids formed (250–350 Å) did not depend strongly on time, nor did it depend strongly on the filler content or the cure time of the matrix. Stress relaxation measurements made under the same conditions as X‐ray scattering measurements showed effects typical of filled materials. However, the relaxation of stress (which followed a power law decay) was much slower than the decay of the number of voids as measured by X‐ray scattering intensity.
Dynamic mechanical properties of an acetylene‐terminated quinoxaline system under air/nitrogen cure
Authors: Lee C. Y.‐C.
Published: April 2003

Torsional impregnated cloth analysis (TICA) temperature scan results of an acetylene‐terminated quinoxaline system indicated the presence of two different reactions with different activation energies. Two additional effects are delineated when cure is carried out in the presence of air. Curing at low temperature in the presence of air will lower the final Tg, but at high temperature it will have the opposing effect. The two reactions that can occur under nitrogen are affected differently by air curing. It appears that one is prohibited by the lower temperature curing in air while the other is not.
The flowing‐afterglow technique, and approach to the study of polymer thermal degradation
Authors: Matuszak Michael L. , Taylor Gene W.
Published: April 2003

We describe here a relatively new analytical method1–3 for following the thermal reaction history of polymers by quantitatively detecting the evolution of gases and some volatiles by flowing‐afterglow spectroscopy. The thermal and oxidative stability of common plastics in many industrial and defense applications is of wide interest. We have studied the evolution of moisture and carbon dioxide from Li2CO3/Orlon‐filled diallyl phthalate (DAP) composites and have briefly examined the thermal stability of Estane 5703, a polyester‐based thermoplastic polyurethane. The results of these preliminary studies have shown the utility of FLAG spectroscopy as a means toward our understanding polymer stability and lifetimes in specified environments. FLAG data, combined with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) data, have extended our knowledge of Li2CO3/Orlon/DAP and Estane aging processes. The DAP composites evolve H2O and CO2 at near ambient temperatures, and we have described the kinetics of gas evolution and have attempted to describe the mechanism of thermal degradation. In the 25–120°C temperature range Estane 5703 evolves CO2 as a decomposition product and some adsorbed moisture.
Graft polymerization of methyl methacrylate onto wool using dimethylaniline/copper(II) system
Authors: Khalil M. I. , El‐Rafie M. H. , Bendak A. , Hebeish A.
Published: April 2003

Dimethylaniline (DMA)/CuII‐induced grafting of methyl methacrylate (MMA) onto wool fibres was studied under different conditions. The grafting reaction was found to be influenced by CuII, DMA, and MMA concentrations as well as polymerization temperature, reaction time, and polymerization medium. While the graft yield increased by increasing the amount of MMA from 100 to 500 mmol/L, maximum grafting occurred at 0.5 mmol/L CuSO4, 10 mmol/L DMA. The graft yield increased by increasing the reaction time from 15 to 150 min and by raising the polymerization temperature from 60 to 80°C. Using dimethylformamide/water and ethyl alcohol/water mixture as a medium for grafting decreased the graft yield, while using isopropyl alcohol/water mixtures increased the graft yield as compared to pure aqueous medium.
The study on radiation grafting of acrylic acid onto fluorine‐containing polymers. III. Kinetic study of preirradiation grafting onto poly(tetrafluoroethylene–hexafluoropropylene)
Authors: Hegazy El‐Sayed A. , Ishigaki Isao , Dessouki Ahmed M. , Rabie Abdelgawad , Okamoto Jiro
Published: April 2003

A kinetic study has been made on the preirradiation grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene–hexafluoropropylene) (FEP) film. The effect of grafting conditions was investigated. The dependencies of the grafting rate on preirradiation dose and monomer concentration were found to be 0.58 and 1.25 order, respectively. The overall activation energy for the graft polymerization was 7.4 kcal/mol. The final degree of grafting increased with preirradiation dose and monomer concentration and slightly decreased as the grafting temperature was elevated. The relationship between the grafting rate and film thickness gave a negative first‐order dependency, which is in agreement with that obtained for polytetrafluoroethylene—AAc grafting system. It was reasonably concluded that this grafting proceeds from the surface to the center of film with progressive monomer diffusion through the grafted layer which swells in the monomer solution.
Miscibility of poly(caprolactone)/chlorinated polypropylene and poly(caprolactone)/poly(chlorostyrene) blends
Authors: Allard Danielle , Prud'homme Robert E.
Published: April 2003

Poly(caprolactone) (PCL) was blended with poly(chlorostyrene) (PSCI) and chlorinated polypropylene (PPCl). A single glass transition temperature Tg was found for these mixtures, indicating their miscibility. PCL crystallizes in these blends when the chlorinated polymer content is not too high. Otherwise, Tg becomes higher than the melting point of PCL and the high viscosity of the medium hinders the crystallization. The miscibility of PCL/PPCI blends cannot be due to hydrogen bonding between the α‐hydrogens of the chlorinated polymer and the carbonyl group of the polyester since PPCI does not have available a large number of α‐hydrogens. It is suggested that a dipoledipole CO…ClC interaction is responsible for the observed miscibility phenomenon and that this interaction is probably also responsible for the miscibility between all other polyesterchlorinated polymer mixtures. Finally, it was observed that poly(α‐methyl‐α‐n‐propyl‐β‐propiolactone), poly(α‐methyl‐α‐ethyl‐β‐propiolactone) and poly(valerolactone) are not miscible with PSCI or PPCl, despite the fact that they are miscible with poly(vinyl chloride).
Reverse osmosis rejection by hydrous inorganic precipitate–cellulose composite membrane
Authors: Kurokawa Yōichi , Ueno Kaoru
Published: April 2003

Composit membranes were prepared by impregnating hydrous inorganic precipites (Fe and Cr oxides, nickel chromate or molybdate) into a cellulose acetate membrane which serves as a support. In these membranes, the hydrous iron oxide composite membrane showed high reverse osmosis properties. The permeability of the composite membrane did not decline with time, and the rejection of organic solute was not appreciably affected by impregnation. However, the rejection of electrolyte increased with impregnation. The measurements of membrane potential revealed that salt rejection is primarily attributable to the effect of membrane charge, i.e., to ion exclusion effect. In electrolyte solutions of 1:1 and 2:1, the membrane was anion selective; on the other hand, in electrolyte solution of 1:2, the membrane was cation selective. These results are characteristic of impregnated hydrous metal oxide.
Polyelectrolyte behavior of chemically modified cotton cellulose
Authors: Shet R. T. , Yabani A. M.
Published: April 2003

Ion exchange and sorption of charged molecules such as dyes, crosslinking agents, etc., by cotton cellulose very much depend on the charge on cellulose, which in turn is known to depend on the external pH of the medium. In order to understand the role of various fixed groups in cellulose in its polyelectrolyte behavior, the standard cellulose was deliberately oxidized with nitrogen dioxide and sodium periodate, and the sorption of formaldehyde and dimethylol dihydroxyethylene urea by these oxycelluloses as well as by alkali‐treated nitrogen dioxide–oxycellulose was investigated. The results obtained are interpreted in terms of polyampholyte behavior of oxycellulose. The nitrogen dioxide–oxycellulose is positively charged and is a polycation in acidic medium due to protonation of aldehyde groups while it is negatively charged and acts as a polyanion in slightly acidic to alkaline medium due to dissociation of carboxyl groups.
Influence of thermal and mechanical histories on the viscoelastic behavior of drawn polyethylene
Authors: Pereña J. M. , Benavente R. , Fatou J. M. G.
Published: April 2003

Storage and loss elasticity complex moduli E′ and E″ and temperatures at which the α relaxation takes place are studied with respect to thermal history, deformation speed, and molecular weight distribution of drawn linear polyethylene. Maximum values of E′ and E″ increase with draw ratio of the hot‐drawn samples, and the α relaxation temperatures increase by around 10°C when the polyethylene filaments are annealed at 110°C. The activation energy of the process, considered as a single one because the symmetrical shape of the maxima, increases with draw ratio, and this increase is less pronounced when the filaments are annealed. Annealing of the filaments produces a decrease in their E′ values, but this decrease is almost negligible for filaments obtained from polyethylene with a broad molecular weight distribution. The final crystallinity of the filaments drawn at room temperature and subsequently annealed is higher for the filaments obtained at lower drawing speed.
Gas diffusion in polymer solutions: A double‐cone flow technique
Authors: Mashelkar R. A. , Soylu M.
Published: April 2003

A new double‐cone flow technique for an experimental investigation of gas diffusion in polymer solutions is described. A theoretical development of the pertinent convective diffusion problem for the flow of a non‐Newtonian fluid over the double cone is presented. Experimental investigation of diffusion of carbon dioxide in aqueous solutions of certain polymers was carried out. The diffusion coefficient deduced from this work shows a marginal enhancement over its value in pure solvent. Possible mechanistic explanations for this phenomenon are explored.
Synthesis of transparent fluorocarbon elastomers: Effect of crosslinker type and electron beam irradiation level on physical and mechanical behavior
Authors: Kaiser R. J. , Miller G. A. , Thomas D. A. , Sperling L. H.
Published: April 2003

Saturated fluorocarbon elastomers are very resistant to chemical reactions, including those of a crosslinking nature. In order to study proper methods of preparing these materials, Viton GLT was mixed with various levels of trimethylol propane trimethacrylate, TMPTM, and triallyl isocyanurate, Diak #7. After molding, the materials were subjected to electron beam irradiation. The glass transition, rubbery modulus, viscoelastic behavior, and equilibrium swelling were used to characterize the materials as a function of crosslinker and irradiation level. In general, the modulus and gel fraction increased with both crosslinker content and irradiation level. Mixtures of both crosslinking monomers produced an unexpected synergism, yielding higher tensile strength, and earlier onset of gelation.
Evaluation of the types of emission systems observed in aqueous media with controlled‐release formulations
Authors: Sherman Larry R.
Published: April 2003

Three types of release systems have been observed for controlled release formulations (CRF) of biocides in aqueous media. A type I system, which is concentration dependent, can be divided into a IA system whose concentration maximum is dependent upon sample size and degradation, and a IB system whose concentration is dependent upon the solubility of the biocide in the solvent. A type II system, which is time dependent, can be divided into a IIA system whose release rate is dependent upon t1/2 and a IIB system whose emission is zero order or dependent only upon time. A type III system, which is a failure system, can be divided into a IIIA system whose concentration decreases to a nondetectable range as a function of t1/2 and a IIIB system whose decreasing concentration is first order. Equations relating the theoretical life of the CRF to its bioactive life are also presented.
Graft copolymerization of vinyl monomers on cellulose using peroxyacetic acid–ferrous ion redox initiator system
Authors: Hirose Shigeo , Hatakeyama Hyoe
Published: April 2003

Graft copolymerization of vinyl monomers such as methacrylate, acrylamide, and acrylic acid on cellulose using the peroxyacetic acid–ferrous ion redox initiator system was studied. Filter paper was chosen as cellulosic material. The effect of the experimental conditions on grafting ratio, grafting efficiency, total conersion and number of branches, and other factors was studied by varying the concentration ratio of peroxyacetic acid to ferrous salt, reaction time, reaction temperature, the addition of disodium ethylenediaminetetraacetate (EDTA), pH, and so on. It was found that there is an optimum range of initiator concentration, that at a higher temperature the copolymerization proceeds more rapidly and more efficiently, and that the addition of EDTA enables the copolymerization to proceed at a higher pH.
Effect of reactant ratio and temperature on the characteristics of phenol–formaldehyde foams
Authors: Singh Daljit , Ohri Suneeta
Published: April 2003

This study presents experimental results on the preparation and characteristics of high‐density phenol–formaldehyde foams and compares their characteristics with the available patent literature. An extrapolation of the data has been used to identify the relevant process parameters used for the preparation of lower‐density foams. The effect of catalyst combination and phenol formaldehyde molar ratio on the ease of foaming and its ultimate strength has been investigated. A total solids refractive index correlation has been developed for following the reaction. The effect of foaming temperature on the density and strength of the foam was also studied.
Use of a dynamic mechanical analyzer to study supported polymers
Authors: Starkweather Howard W. , Giri Mylar R.
Published: April 2003

The real and imaginary parts of the complex modulus of polymers which must be supported can be determined with the Du Pont Dynamic Mechanical Analyzer. Polymer coatings of equal thickness are laminated on both sides of a thin metal sheet. The flexural modulus of the laminate is given by E = E1X3 + E2(1 − x3) where E1 and E2 are the moduli of the metal and the polymer, respectively, and x is the thickness fraction of metal. Under some conditions, the dynamic viscosity of the polymer can also be determined.
Behavior of cellulose graft copolymer towards persulphate oxidation. III. Poly(acrylonitrile) graft copolymers
Authors: Khalil M. I. , Aglan O. I. , Hebeish A.
Published: April 2003

Cotton cellulose was graft copolymerized with poly(acrylonitrile) to different levels. The copolymers so obtained together with the nongrafted cellulose were oxidized at different pH's (4–10) and temperatures (50–70°C) with potassium persulphate. The oxidation reaction was studied with respect to oxygen consumption, mass loss, and changes in copper number and carboxyl content of the cellulosic materials. It was found that the rates of oxidation at pH 4 for the copolymers are substantially higher than that of the nongrafted cellulose and the rate of oxidation is higher the higher the level of grafting. The reverse is the case at pH 10. The mass loss increases as the oxygen consumption increases irrespective of the substrate used and the pH employed. The magnitude of the mass loss is substantially lower in the case of grafted cellulose than in the case of nongrafted cellulose. The cellulosic copolymers with higher graft levels show lower mass loss than those having lower graft levels. However, the copper number and carboxyl content of the oxidized grafted cellulose are higher than those of the nongrafted cellulose at the same oxygen consumption. It is believed that the presence of poly(acrylonitrile) graft in the molecular structure of cellulose impedes cellulosic chain scission without necessarily preventing oxidation of cellulose hydroxyls.
Grafting onto wool. XVI. Graft copolymerization of vinyl monomers by use of TBHP–FAS as redox initiator
Authors: Misra B. N. , Sood D. S.
Published: April 2003

Methyl acrylate (MA), methyl methacrylate (MMA), and n‐butyl vinyl ether (n‐BVE) have been graft‐copolymerized onto Himachali wool in an aqueous medium by using tertiary butyl hydroperoxide ferrous ammonium sulfate (TBHP‐FAS) redox system at 40°C, 50°C, 60°C, and 70°C for various reaction periods. Percentage of grafting and percent efficiency have been determined as functions of concentration of monomers, molar ratios of [TBHP]/[FAS], time and temperture. Molar ratios of [TBHP]/[FAS] were found to influence grafting of different monomers studied. Chemical evidence indicates that a covalent bond formation occurs between grafted polymeric chain and backbone polymer. The rate of grafting (Rp) and induction period (Ip) of different monomers towards graft copolymerization were determined as function of total initial monomer concentrations. Rp and Ip of n‐BVE are independent of total initial monomer concentrations while Rp and Ip of both MA and MMA were found to depend on the total initial monomer concentrations. MA, MMA, and n‐BVE were found to differ in reactivity towards grafting onto wool in the presence of (TBHP‐FAS) redox system; the following reactivity order was observed: MMA > MA > n‐BVE.
Interlaminar shear properties of some glass‐fiber‐reinforced phenolic and polyester laminates
Authors: Kaminski A.
Published: April 2003

Chopped strand mat and glass‐fabric‐reinforced thin and thick laminates were made from phenolic and polyester laminating resins using three modifications of a hand lay‐up method. Short‐beam interlaminar shear strengths were determined in three‐point bending at a span‐to‐depth ratio 3:1. Plane and perpendicular specimens were used. It was found that the perpendicular specimens were more useful. Interlaminar delamination energies were determined statically and dynamically. It was found that the results for the phenolic and polyester laminates cannot be simply compared because of differences in the fracture mechanism.
Comparison of dynamic and static degradation of poly(vinyl chloride)
Authors: Pukánszky Béla , Nagy Tibor T. , Kelen Tibor , Tüdõs Ferenc
Published: April 2003

The thermal degradation of PVC was measured under dynamic and static conditions. The UV and IR spectra, as well as the molecular weight distribution of the PVC samples, taken after different time intervals were measured. It was established that during the dynamic PVC degradation, performed in a mixing chamber, two stages with different degradation rates can be distinguished both in extinction and torque vs. time curves. While oxygen does not, dissolved HCl does play an important role in the dynamic degradation: HCl steps into reaction with the formed polyenes and has a catalytic action. The chemical degradation, particularly the crosslinking, produces the changes in the rheological behavior of the material. Results were compared with those obtained under static conditions in argon, air, and HCl atmosphere.
Physical properties of oriented poly(butylene terephthalate)
Authors: Leung W. P. , Choy C. L.
Published: April 2003

The effect of orientation on the low‐strain mechanical properties, dielectric relaxation, and thermal expansivity of poly(butylene terephthalate) has been studied. The α relaxation at 50°C (1 Hz), which involves large‐scale chain motion in the amorphous regions, is reduced in magnitude and shifted to higher temperature after drawing. In contrast, the localized motions of the carbonyl and glycol groups associated with the β process at −90°C (1 Hz) is not much affected by orientation. At low temperature, a large difference along and normal to the draw direction is observed for both Young's modulus and thermal expansivity. The anisotropy, however, diminishes with increasing temperature and becomes nearly zero above the α relaxation. This feature can be understood on the basis of the Takayanagi model.
Sorption of diethyl phthalate by nitrocellulose fibers
Authors: Lewis T. J. , Roberts G. M.
Published: April 2003

The manner in which diethyl phthalate (DEP) is absorbed into nitrocellulose (NC) fibers has been observed microscopically. The movement of pure DEP into dry fibers proceeds by capillary motion up the central canal (lumen) and through microcracks between fibrils. Attack, measured by a large change in birefringence, spreads from these foci, and within the time scale of the experiment there is little interaction with the primary (outer) wall of the fiber. If, however, the lumen and other capillary passages are blocked by water or other liquid, then attack proceeds evenly from the outer wall and a sharp boundary between swollen and unswollen material moves at a uniform speed towards the center of the fiber and appears to be unaffected by the fibrillar structure (Case II swelling). If the supply of DEP to the surface is interrupted, this boundary becomes immobile, and the concentration of DEP in the swollen layer is that which is just sufficient to saturate residual un‐nitrated hydroxyl groups on the NC. Reducing the activity of the DEP by admixture with benzene results in similar sharp boundaries, presumably because capillaries become blocked with spent diluent. Apart from capillary action, movement is always perpendicular to the fiber axis.
Formation of cracks on photodegraded nylon 6 filaments
Authors: Fujiwara Y. , Zeronian S. H.
Published: April 2003

Cracks were found on the surface of drawn nylon 6 filaments irradiated with ultraviolet (UV) light from a mercury lamp under various humidities at room temperature. The cracks were formed perpendicular to the fiber axis and were of varying sizes. No cracks were observed on undrawn filaments or drawn filaments exposed to UV light in a dry atmosphere. Considerable shrinkage was found in drawn samples by thermomechanical analysis indicating the presence of residual stress in the material. The cracking is explained in terms of the residual stress and plasticization by moisture.
An unusual visual microcracking/healing phenomenon in polycarbonate at room temperature
Authors: Narkis M. , Bell J. P.
Published: April 2003

Polycarbonate samples show no visible changes upon removal from boiling water. However, during a subsequent storage stage at room temperature they begin to develop visible disc‐shaped microcracks whose number and size increase with time. At a certain time during the room temperature storage period a healing process begins leading in many cases to a complete visual disappearance of the microcracks. The cracking/healing phenomenon is explained in terms of water‐supersaturated systems undergoing water phase‐separation creating water filled microcracks. These thin water filled microcracks then lose their water to the environment during drying at room temperature, close, and visually heal.
Activating pulp toward acetylation by chemical or mechanical means
Authors: Heikal Salwa O. , El‐Kalyoubi Samira F.
Published: April 2003

Activation of pulps during acetylation, by prior mechanical or chemical treatment, has been investigated. The effect of degree of beating on the acetylation rate of wood and bagasse pulps has been studied. It is found that the acetylation rate of pulps increases when the degree of beating of pulps is increased to a definite degree, after which it slows down. The maximum reactivity of bagasse pulp is obtained at 50°SR, while that of wood pulp is observed at 30°SR. The effect of grafting of acrylonitrile onto bagasse and wood pulps on their reactivity during acetylation has been also studied. The results indicate that grafting of acrylonitrile onto pulps has a favorable effect on their acetylation rate. This is dependent on the degree of grafting as well as the origin of pulp fibers. The most suitable method of activation during acetylation reaction is dependent on the origin of the pulp. The reactivity of bagasse pulp during acetylation is influenced more by beating of pulp, prior to the reaction, than by the grafting of acrylonitrile onto pulp. On the other hand, the acetylation reaction of wood pulp is activated by grafting rather than by beating. Also the effect of the activation process, mechanical or chemical, on the strength properties of the paper sheets produced from acetylated pulps has been investigated. Chemical activation of wood pulp prior to acetylation resulted in pulp with slightly higher strength properties than that activated by mechanical means. But, in the case of bagasse pulp, mechanical activation resulted in a pulp with strength superior to that produced by chemical activation.
Process for the formation of biaxially oriented films of poly(p‐phenylene terephthalamide) from liquid crystalline solutions
Authors: Flood John E. , White James L. , Fellers John F.
Published: April 2003

A new process for making equal biaxially oriented films from liquid crystalline solutions of poly(p‐phenylene terephthalamide) (PPD‐T) is described. The process involves extruding solutions of PPD‐T/H2SO4 through an annular die and over an oil‐coated mandrel into a coagulation bath. The films were studied using wide angle X‐ray diffraction (WAXS) and scanning electron microscopy (SEM). Tensile stress–strain properties were obtained on samples cut at various directions in the plane of the film. Biaxially oriented films which possess equal properties in the various directions in the plane of the film were produced. Moduli of 2.3 × 109 Pa and tensile strengths of 9.6 × 107 Pa were obtained in the plane of the film. Films with unequal biaxial orientation were also produced. These tend to have higher modulus/tensile strength in the direction of major orientation, the machine direction (up to 8.3 × 109 Pa/2.5 × 108 Pa), but become brittle in the transverse direction.
Vapor–liquid equilibria for benzene/polybutadiene and cyclohexane/polybutadiene systems at 333, 355, and 373 K using gas chromatography
Authors: Lau W. Robbie , Glover Charles J. , Holste James C.
Published: April 2003

A perturbation chromatography apparatus has been designed and constructed for determining the vapor–liquid equilibrium between a two‐component (solvent/helium) vapor phase and a two‐component (polymer/solvent) liquid phase. The apparatus performed very well, giving reproducible and reliable results that agree with independent, previously reported studies. All tests of the equipment indicated that it was successful in meeting the conditions of low column pressure drop, small perturbations, and slow flow rate that are required for perturbation chromatography. Binary polymer/solvent data were obtained for polybutadiene (PBD)/benzene or polybutadiene/cyclohexane systems at solvent partial pressures to 40 kPa and for n‐hexane at infinite dilution, all at the three temperatures of 333.15, 355.00, and 373.15 K. The experimental data for each system can be represented within experimental error by the Flory–Huggins polymer solution theory using a single binary interaction parameter that is independent of temperature and concentration.
Rheological and solid wall boundary condition characterization of unvulcanized elastomers and their compounds
Authors: Toki Shigeyuki , White James L.
Published: April 2003

An extensive fundamental investigation of the rheological properties and solid wall boundary condition shear stress of elastomers and elastomer–carbon black compounds has been carried out. The elastomers were an emulsion butadiene–styrene copolymer (SBR 1500) and a polybutadiene. Shear flow rheological properties were measured using a newly designed sandwich rheometer, in both constant shear rate and creep modes as well as in a capillary rheometer. A constant elongation rate rheometer for elastomers was developed. Stress relaxation measurements were also carried out in the sandwich rheometer. The shear viscosity of the gum elastomers exhibits a constant very high shear zero viscosity (8 × 108 Pa.s for SBR 1500 at 100°C) and decreases with increasing shear rate. The compounds exhibit yield values of similar magnitude to carbon black compounds of molten plastics. Only the SBR 1500 and its compounds were studied in the elongational flow mode. It was not possible to achieve a steady state in these experiments. An apparatus for measurement of shear stress as a function of velocity (shear rate) at a specified pressure was developed. The instrument, which we call a friction tester, was used not only to determine wall shear stress but to investigate the regime of flow and potentially determine conditions for the onset of slip. Evidence of changing flow regimes were found, and the implications discussed.
Identification of two pass regimes for nylon‐66 based rods in the critical oxygen index test
Authors: Wharton R. K.
Published: April 2003

Critical Oxygen Index (COI) values for rods of a nylon‐66 based material of various diameters have been determined at 40°C. The existence of two discrete COI values has been identified for many sizes above a critical diameter: the two indexes correspond to clean burning and to burning with melting and dripping. The difference between the two indexes is dependent on rod diameter and can be greater than five units.
Synthesis of brominated acenaphthylenes and their flame‐retardant effects on ethylene–propylene–diene terpolymer
Authors: Morita Yohsuke , Hagiwara Miyuki
Published: April 2003

Bromoacenaphthylenes and their condensates as flame‐retardant reagents were synthesized by bromination of acenaphthylene using ZnCl2CF3COOH or FeCl3 as catalysts and subsequent dehydrobromination. The chief components were identified as bromoacenaphthylene monomers when ZnCl2CF3COOH were used, and as their condensates (mostly trimers) in the case of FeCl3. Their performance as flame‐retardant reagents for ethylene–propylene–diene terpolymer (EPDM) was evaluated by measuring the oxygen index of finished compounds, and flammability by a vertical flammability test based on UL‐94‐VO. Both the monomers and the condensates demonstrated high flame‐retardant effectiveness. The high efficiency was attributed to their excellent dispersity in the base polymer and their characteristic thermal decomposition behavior. In TGA, they decomposed in a very wide range of temprature (ca.200–560°C), which covers the decomposition range of EPDM. This was attributed to the existence of bromines of different thermal stabilities in one molecule.
Prediction of sedimentation coefficients of random coil polymers
Authors: Kok C. M. , Rudin Alfred
Published: April 2003

The concentration dependence of the radius of gyration and the equivalent hydrodynamic radius of polymers in solution is described well by a model developed in earlier work. The calculated hydrodynamic volumes of solvated polymers are combined with the statistical mechanical calculations of Burgers for hard spheres to predict sedimentation coefficients at finite concentrations. The predicted values are in good agreement with experimental results.
Smoke suppression by ammonium polyphosphate in poly(acrylonitrile) combustion
Authors: Ballistreri Alberto , Montaudo Giorgio , Puglisi Concetto , Scamporrino Emilio , Vitalini Daniele
Published: April 2003

The influence of ammonium polyphosphate (APP) on the smoke emission of poly(acrylonitrile) (PAN) has been examined, and its mechanism of action as a smoke suppressant agent has been investigated. Smoke density and corresponding residual char data, as a function of temperature, were obtained in order to characterize the smoke propensity of PAN. The amount of generated smoke, both in smoldering and flaming conditions, was considerably lowered by the presence of APP, and higher char yields were obtained. Beside the smoke suppression, flame inhibition effect of APP on PAN was evidenced. Thermogravimetry (TG), oxygen index (OI), and nitrous oxide index (NOI) experiments were also performed. On the basis of our data, APP appears to act as a char‐forming agent in PAN combustion. Both smoke suppression and flame inhibition effects can be considered a consequence of this action.
Experimental studies of the relationship of processing to the crack growth of carbon‐black‐loaded SBR—cis‐polybutadiene compounds
Authors: Lee Biing‐Lin
Published: April 2003

The crack growth of a highly carbon‐black‐loaded SBR—cis‐polybutadiene (BR) blend is investigated as a function of the distribution of carbon black in the individual rubber phases. The blend compound consists of SBR/BR/carbon black/oil = 60/40/85/60 by weight ratio and curatives. A new “old process” is devised to control the carbon black distribution in the individual rubber phases, that is, cross mixing the SBR and BR black master batches with different amounts of carbon black in the SBR and BR patches. The results show that crack growth is very sensitive to the carbon black distribution. A better crack growth resistance compound is seen containing proportionately more carbon black in the major rubber SBR phase. A simple analogy of rubber blends to the rubber‐modified thermoplastics is proposed to interpret these findings. The heat buildup of the blends is also affected by the carbon black distribution. A low heat buildup compound is observed in the system in which more carbon black is in the SBR batch, which is also a better crack growth resistance compound. It is not unexpected that the strength of rubbers decreases with increase of temperature, and so the rate of crack growth becomes faster as heat builds up.