bluuebunny/crossref_metadata_2025 huggingface dataset:
Settling behavior of fillers in thermosetting epoxy casting resins during cure
Authors: Fukushima Jiro , Yasuda Kazuo , Teratani Hiroshi , Nishizaki Shunichiro
Published: April 2003

Using a theory based on a modified Stokes' law equation, the settling behavior of fillers was investigated (glass beads and silica powder) in thermosetting epoxy casting resins during cure. In this study a suspension (a thermosetting epoxy casting resin) containing a large amount of filler particles is assumed to be a homogeneous fluid, and the settling phenomena are treated such that one or more particles of the filler settle into the homogeneous fluid under gravity without interference from other particles. The viscosity increase of the fluid during cure is taken into consideration. The experimental results agree well with the theoretical predictions when the settling distances are small and the particle size distribution is narrow. When these conditions are not satisfied, various effects are observed such as convection, filtering, combination, bottom effect, and a broad particle size distribution. In addition, the formation of a compression zone and of a compaction zone are clearly observed.
Pressure drop through tapered dies
Authors: Lenk R. S.
Published: April 2003

A simple method is presented for calculating the pressure drop for the flow of power law liquids in dies with a wide slit profile and with vertical and/or lateral tapers, as well as in dies with the shape of a circular truncated right cone. Tapered dies are known to give improved extrudate quality and/or higher output rates without encountering extrudate defects which occur in dies with parallel channels at similar extrusion pressures. A possible ultimate optimization of the extrusion process—as far as die design is concerned—is discussed. It is suggested that this be based upon an extension of the method from dies with a rectilinear convergent taper to dies with a curvilinearly converging channel aspect the generation of which latter is indicated.
The kinetics of polyesterification. III. A mathematical model for quantitative prediction of the apparent rate constants
Authors: Lin Chen Chong , Yu Ping Chang
Published: April 2003

A mathematical model for the apparent constants k1 and k2 which presents a quantitative explanation of the observed kinetic behavior in both uncatalyzed and acid‐catalyzed polyesterification between ethylene glycol and a dibasic acid in different initial molar ratios was developed. This model consists of two types of similar semiempirical equations, one of which applies to the uncatalyzed reaction and the other to the acid‐catalyzed reaction. They are both based on the same apparent dissociation coefficient, kh, of a dibasic acid in ethylene glycol, which can be expressed as kh = K ear at constant temperature. The symbol a in the equation represents the sensitivity constant to change in the initial molar ratio r = [OH]0/[COOH]0. The value of the true rate constant for polyesterification between succinic acid and ethylene glycol at 195°C was estimated to be 3.02 × 10−3 [in kg2/(equiv. moles)2·min] based on this model.
Poly(methyl methacrylate) membranes
Authors: Sakai Yoshitada , Tanzawa Hiroshi
Published: April 2003

Uniform and symmetric membranes were formed from poly(methyl methacrylate) (PMMA) by making use of the stereocomplex phenomenon which characteristically occurs in the solution of a mixture of isotactic PMMA and syndiotactic PMMA. The water permeability of the membrane was very high compared to a commercially available cellulosic membrane, whereas their NaCl permeabilities were the same. The permeabilities of the membranes are explained by a simple capillary model. By varying the tacticity of the polymer it was found that the finest membrane structure is formed at the isotactic polymer ratio of ca. 30%. This shows the close relationship between complex formation and membrane permeability.
Utilization of lignins in rubber compounding
Authors: Kumaran M. G. , De Sadhan K.
Published: April 2003

Lignin in the form of lignosulfonate containing about 33% moisture was found to be dispersible in natural rubber by dry mixing. Properties such as tear resistance, abrasion resistance, flex crack resistance, and crack growth resistance improved upon addition of lignin, irrespective of the nature of filler added. This lignin was found to have negative effects on modulus, tensile strenght, resilience, heat buildup, and compression set, which showed, however, remarkable improvement upon aging.
Controlled drug release by polymer dissolution. I. Partial esters of maleic anhydride copolymers—properties and theory
Authors: Heller J. , Baker R. W. , Gale R. M. , Rodin J. O.
Published: April 2003

The kinetics of drug release from a series of partial esters of vinyl acetate–maleic anhydride has been investigated. These polymers in their un‐ionized forms are hydrophobic and water insoluble, but in their ionized forms they are water soluble. Polymer dissolution is pH sensitive, and different half‐esters have a characteristic pH range above which they are soluble and below which they are insoluble. When films are placed in buffered media, they erode at a constant rate that depends on the pH of dissolution of the polymer and on the pH of the buffered medium. Dissolution of the polymer is limited to the polymer–buffer medium interface, and drugs dissolved or uniformly dispersed in the polymer are released by zero‐order kinetics. A detailed model has been developed that successfully correlates dissolution behavior and various experimental parameters.
Effect of notches and glass fiber reinforcement on fatigue behavior of polycarbonate
Authors: Misaki Toshikazu , Kishi Junji
Published: April 2003

In order to investigate the effect of a notch on the tensile properties of polycarbonate and 30% glass fiber‐reinforced polycarbonate, two types of notched specimens were prepared. These notches were a sharp 60° notch and a dull notch with rounded tip 1.5 mm in radius at the base of the 60° notch. The notches decreased the tensile strength of polycarbonate. The sharp notch reduced tensile strength more effectively than the dull notch. In 30% glass fiber‐reinforced polycarbonate, even the dull notch decreased the tensile strength considerably. Unnotched polycarbonate was subjected to cyclic tensile loading of 104 cycles at 10 Hz, with varying cyclic stress. It was found that the elongation at break decreased rapidly with increase in cyclic stress. The notches considerably decreased the tensile fatigue strengths of polycarbonate and glass fiber‐reinforced polycarbonate in 104 cycles at 10 Hz.
Thermal degradation of polymers. Part XVIII. The synthesis and characterization of quinazolone pre‐polymers
Authors: Chan H. S. O. , Still R. H.
Published: April 2003

A series of quinazolone pre‐polymers have been prepared from 4,4′‐diaminodiphenyl‐3,3′‐dicarboxylic acid and aromatic diacetamido compounds by melt polycondensation. The pre‐polymers have been characterized by combustion analysis, viscometry, vapor pressure osmometry, and thermal analytical methods (TG, DTA, and DSC). Structures have been elucidated by spectroscopic methods (IR and NMR). The thermal cyclization of these pre‐polymers to the partial ladder polyquinazolone has been studied and optimized using IR, DSC/DTA, TG, and evolved gas analysis. The cyclization behavior of these systems has been resolved in terms of concurrent dehydration and decarboxylation.
Redox‐initiated graft copolymerization onto wool with thiourea as reductant. IV. Grafting of vinyl sulfone dyes onto wool using thiourea–H2O2 redox system
Authors: Hebeish A. , Abdel‐Fattah S. H. , El‐Rafie M. H.
Published: April 2003

Wool samples were dyed with a vinyl sulfone dye in the presence of thiourea and H2O2 under a variety of conditions. Increasing the H2O2 concentration from 2.5 mmole/l. to 20 mmole/l. caused a significant enhancement in the rate of the dyeing, whereas increasing the thiourea concentration from 1.25 mmole/l. to 10 mmole/l. brought about an increase in the rate of dyeing. Further increase in the thiourea concentration (i.e., up to 15 mmole/l.) caused a significant decrease in the rate of dyeing. Raising the dyeing bath temperature from 30°C to 70°C accelerated appreciably the rate of dye uptake. With respect to dye concentration, complete exhaustion occurred at dye concentrations of 0.5% and 1% (owf) when dyeing was performed at 70°C and pH 6 over a duration of 2 hr. This contrasts with 90% and 55% exhaustion for dye concentrations of 3% and 5% (owf), respectively. The rate of dyeing obtained at different pH's follows the order pH 2 < pH 4 < pH 6 < pH 8. A dye fixation of approximately 68%, 64%, and 50% could be achieved at pH 4, 6, and 8, respectively, if dyeing was performed at 70°C for 2 hr in a bath containing a dye concentration of 3% (owf) in the presence of thiourea (10 mmole/l.) and H2O2 (15 mmole/l.). The mechanism of dyeing is believed to be grafting by vinyl addition to wool radical formed under the influence of the decomposition products of thiourea and H2O2. Evidence of this mechanism is presented.
The influence of nucleation density and cooling rate on crystallization of polyethylene from the melt
Authors: Fraser G. V. , Keller A. , Odell J. A. , Wills H. H.
Published: April 2003

Different samples of high‐density polyethylene provided different nucleation densities which were assessed by optical microscopy and light scattering. Crystallizations were carried out under controlled cooling rates using a microscope hot stage and DSC from which crystallization temperatures were obtained. It is shown that the effective crystallization temperature is a function of the nucleation density, and a quantitative fit is found with theoretical predictions based on crystallization kinetics. The melting point was, in turn, found to be dependent on nucleation density, through the agency of lamellar thickness as assessed by low‐frequency Raman spectroscopy. The effect of cooling rate on melting point is also explained in terms of variation of supercooling. The implications of these effects together with considerations of surface and interior nucleation and sample size are discussed for the industrial processing of polyethylene.
Instabilities and failure in elongational flow and melt spinning of fibers
Authors: White James L. , Ide Yoshiaki
Published: April 2003

A theoretical and experimental study of instability and failure behavior during melt spinning is presented. From an analysis of system dynamics, draw resonance is shown to be a continuous processing analogue of ductile failure. Using viscoelastic fluid mechanics and the White‐Metzner constitutive model, it is shown that melts which exhibit ductile failure in elongational flow tend to show draw resonance in melt spinning. Deformation hardening melts exhibit cohesive fracture in elongational flow and melt‐spinning processes.
Crosslinking and mechanical property of liquid rubber. II. Curative effect of aromatic diols
Authors: Minoura Yuji , Yamashita Shinzo , Okamoto Hiroshi , Matsuo Tadao , Izawa Michiaki , Kohmoto Shun‐ichi
Published: April 2003

The relationships between the properties and structure of polyurethane elastomers derived from hydroxyl‐terminated liquid polybutadiene (HT‐BD), several low molecular weight aromatic diols, and diisocyanates were studied. The curative effects of the diols were examined by such means as tensile properties, dynamic viscoelasticity, x‐ray diffraction, and others. It was found that the properties of the elastomers derived from HT‐BD were greatly affected by the structure of low molecular weight chain extender diol. These results were interpreted by the steric effect, crystallinity, and the concentration of polar groups.
Polymerization mechanisms and molecular weight distribution. II. AIBN‐initiated polymerization of styrene at 60°C
Authors: Braks Jorma G. , Huang Robert Y. M.
Published: April 2003

An experimental study was carried out on the AIBN‐initiated polymerization of styrene at 60°C. The kinetic rate constants were determined by the method of moments and the MWD method, which was proposed in a previous paper. The results compared favorably with the data in the literature and the MWD method was noted to yield more consistent results than the method of moments, which indicates the importance of considering the whole molecular weight distribution. The theoretical MWD was found to approximate the experimental MWD well. The chain‐transfer constant to AIBN was found to be between 0.09 and 0.14.
Mechanical α‐dispersion and interaction in filled polystyrene and polymethylmethacrylate
Authors: Iisaka K. , Yama K. Shiba
Published: April 2003

Dynamic mechanical properties of polystyrene (PS) and polymethylmethacrylate (PMMA) filled with glass beads and mica flakes have been investigated. The α‐dispersion temperature (Tα) increases with filler content in each system. The increase in Tα is larger for PMMA than for PS in the case of the same filler; the increase in Tα is larger for mica than for glass in the case of the same polymer. Polymer‐filler interaction energies have been estimated from heats of adsorption of the monomers of the filler surfaces determined by solid gas adsorption chromatography. The increase in Tα can be related to the extent of polymer‐filler interaction energy. The thickness of the partially immobilized layer on the filler surface has been estimated to be the orders of 0.1 and 1.0 μm, respectively, for the mica and the glass‐filled systems.
Graft copolymerization of hydrophilic monomers onto irradiated polypropylene fibers
Authors: Sundardi F.
Published: April 2003

A method of graft copolymerization of hydrophilic monomers, such as 1‐vinyl‐2‐pyrrolidone, acrylonitrile, acrylic acid, and acrylamide, onto irradiated polypropylene fibers has been studied. γ ray as well as electron beam were employed for the irradiation processes. Graft‐copolymerization kinetics and the properties of grafted fibers have been investigated. Moisture regain, dyes absorption, and melting point of the grafted fibers were found to increase with the increasing of the degree of grafting. Polypropylene for 1‐vinyl‐2‐pyrrolidone grafted fibers showed excellent dye absorption for almost all kinds of dyes such as direct, basic, acid, reactive, disper, and naphthol dyes. However, for polypropylene acrylic acid grafted fibers, the colorfastness to washing was found to be unsatisfactory. The colorfastness to washing for polypropylene 1‐vinyl‐2‐pyrrolidone grafted fibers was found to be fairly good for certain types of dyes such as vat and naphthol dyes.
The preparation and tensile properties of polyethylene composites
Authors: Mead W. T. , Porter Roger S.
Published: April 2003

Single polymer composites have been prepared using different morphologies of polyethylene as matrix and as the reinforcement. Depending on annealing conditions, the ultraoriented fibers used as reinforcement can have higher melting points (ca. 139°C) than the matrix made from the same conventionally crystallized high‐density polyethylene (ca. 132°C) or from low‐density polyethylene (ca. 110°C). The optimum temperature has been assessed for bonding to occur by growth of transcrystalline regions from the melt matrix without considerable modulus reduction of the annealed ultraoriented and reinforcement fiber or film. Pullout tests have been used for determining the interfacial shear strength of these single polymer composites. The interfacial shear strength for the high‐density polyethylene films embedded in a low‐density polyethylene matrix is 7.5 MPa and for high‐density polyethylene self‐composites is 17 MPa. These values are greater than the strength for glass‐reinforced resins. The strength is mainly due to the unique epitaxial bonding which gives greater adhesion than the compressive and radial stresses arising from the differential shrinkage of matrix and reinforcement. The tensile modulus of composites prepared from uniaxial and continuous high‐density polyethylene films embedded in low‐density polyethylene obeys the simple law of mixtures and the reinforced low‐density polyethylene modulus is increased by a factor of 10. High strength cross‐ply high‐density‐polyethylene—low‐density‐polyethylene laminates have also been prepared and the mechanical properties have been studied as the film orientation is varied with respect to the tensile axis.
Radiation‐induced polymerization of water‐saturated styrene in a wide range of dose rate
Authors: Takezaki J. , Okada T. , Sakurada I.
Published: April 2003

Radiation‐induced polymerization of water‐saturated styrene (water content 3.5 × 10‐2 mole/liter) was carried out in a wide range of dose rate between 1.2 × 103 and 1.8 × 107 rad/sec, and compared with the polymerization of the moderately dried styrene (water content 3.2 × 10‐3 mole/liter). Molecular weight distribution curves of the polymerization products showed that they were generally consisted of four parts, namely, oligomers, radical, cationic, and super polymers. Contributions of the four constitutents to the polymerization and the number average degrees of polymerization (DP) of the four kinds of polymers were calculated by the graphical analysis of the curves. The rate of radical polymerization and DP of radical polymers are independent of the water content; the dose rate dependences of the polymerization rate and DP agree with the well known square root and inverse square root laws, respectively, of the radical polymerization of styrene. The rate of ionic polymerization is directly proportional to the dose rate, but it decreases, at a given dose rate, inversely proportional to the water content of styrene. DP of ionic polymer is independent of the dose rate but decreases with increasing water content. The super polymer of DP about 104 is not formed in the case of the moderately dried styrene. G values for the initiating radical and ion formation are calculated to be, independently of the dose rate and water content, 0.66 and 0.027, respectively. It was suggested that oligomer was formed in the early stage by the interaction of cation with anion and only those cations which had survived underwent polymerization.
Mechanism and evaluation in electroinitiated copolymerization coatings of acrylonitrile and acrylic acid
Authors: Teng F. S. , Mahalingam R.
Published: April 2003

Adherent films of copolymers on different metal surfaces were formed by an electrolytically initiated polymerization of acrylonitrile (AN) and acrylic acid (AA) in 0.05N H2SO4 aqueous solution. The electrolysis was carried out under a constant current. Hydrogen overvoltages for five different metals used as the cathode were measured in order to interpret the nature and quality of the coating. Solutions containing varying volume fractions of AN and containing different electrolytes gave rise to coatings of varying film thickness. Based on the analyses of copolymer compositions, it is believed that the polymer was formed at the cathode by a free‐radical propagation mechanism. The film hardness and the adhesion between the polymer and the metal surface were measured with an Arco microknife. Furthermore, the scanning electron microscope (SEM) was used to examine the structure of the film surface and cross section. The corrosion rates of the coated and uncoated metals in substitute ocean water were also measured for purposes of evaluation of the coatings.
Graft polymerization of vinyl acetate onto starch. Saponification to starch–g–poly(vinyl alcohol)
Authors: Fanta George F. , Burr R. C. , Doane W. M. , Russell C. R.
Published: April 2003

Graft polymerizations of vinyl acetate onto granular corn starch were initiated by cobalt‐60 irradiation of starch‐monomer‐water mixtures, and ungrafted poly(vinylacetate) was separated from the graft copolymer by benzene extraction. Conversions of monomer to polymer were quantitative at a radiation dose of 1.0 Mrad. However, over half of the polymer was present as ungrafted poly‐(vinyl acetate) (grafting efficiency less than 50%), and the graft copolymer contained only 34% grafted synthetic polymer (34% add‐on). Lower irradiation doses produced lower conversions of monomer to polymer and gave graft copolymers with lower % add‐on. Addition of minor amounts of acrylamide, methyl acrylate, and methacrylic acid as comonomers produced only small increases in % add‐on and grafting efficiency. However, grafting efficiency was increased to 70% when a monomer mixture containing about 10% methyl methacrylate was used. Grafting efficiency could be increased to over 90% if the graft polymerization of vinyl acetate‐methyl methacrylate was carried out near 0°C, although conversion of monomers to polymer was low and grafted polymer contained 40‐50% poly(methyl methacrylate). Selected graft copolymers were treated with methanolic sodium hydroxide to convert starch–g–poly(vinyl acetate) to starch–g–poly(vinyl alcohol). The molecular weight of the poly(vinyl alcohol) moiety was about 30,000. The solubility of starch–g–poly(vinyl alcohol) in hot water was less than 50%; however, solubility could be increased by substituting either acid‐modified or hypochlorite‐oxidized starch for unmodified starch in the graft polymerization reaction. Vinyl acetate was also graft polymerized onto acid‐modified starch which had been dispersed and partially solubilized by heating in water. A total irradiation dose of either 1.0 or 0.5 Mrad gave starch–g–poly(vinyl acetate) with about 35% add‐on, and a grafting efficiency of about 40% was obtained. A film cast from a starch–g–poly(vinyl alcohol) copolymer in which homopolymer was not removed exhibited a higher ultimate tensile strength than a comparable physical mixture of starch and poly(vinyl alcohol).
Continuous emulsion polymerization. Modeling oscillations in vinyl acetate polymerization
Authors: Kiparissides C. , MacGregor J. F. , Hamielec A. E.
Published: April 2003

A theoretical investigation of the emulsion polymerization of vinyl acetate in a continuous stirred tank reactor operating under conditions of sustained oscillations is reported here. Models of two levels of sophistication are developed: a comprehensive model that solves for the age distribution function of polymer particles and a simplified model that assumes discrete nucleation periods. The latter model should find use in adaptive control of latex reactors. These models adequately simulate experimental data after Greene et al.2 for the emulsion polymerization of vinyl acetate under conditions of sustained oscillations.
Mechanical relaxation processes in polyacrylonitrile polymers and copolymers
Authors: Kenyon A. S. , Rayford McC. J.
Published: April 2003

The dynamic mechanical properties of molded and cast polyacrylonitrile and copolymers have been measured by an automatic Rheovibron. The transitions are described for the amorphous, “paracrystalline,” and crystalline phases. Based upon a number of polymer theories of multiple phases in polymeric systems, the transitions have been assigned to specific polymer motions. Three transitions are defined for the alpha transition region. The mechanical response is compared to x‐ray diffraction and infrared to ascertain the transition assignments in decreasing order beginning with the highest temperature transition as (1) the main transition for the amorphous phase (T1), (2) dipole–dipole interaction which is related to the “paracrystalline phase” (T2), and (3) secondary transition for the amorphous phase (T3).
Pulsed‐field gradient NMR measurements of diffusion of oil in rubber
Authors: von Meerwall E. , Ferguson R. D.
Published: April 2003

The pulsed‐gradient NMR method of Stejskal and Tanner was used to measure the diffusion of oil in synthetic cis‐polyisoprene. The diffusion encounters no barriers with spacings at least up to several μm and generally displays free‐volume behavior, obeying the WLF temperature dependence between −10°C and +130°C, and the Fujita‐Doolittle concentration dependence between 10 and 90 vol‐% oil.
Effects of water and moisture on strengths of optical glass (silica) fibers coated with a UV‐cured epoxy acrylate
Authors: Wang T. T. , Vazirani H. N. , Schonhorn H. , Zupko H. M.
Published: April 2003

Furnace‐drawn optical silica fibers coated with a uv‐curable epoxy acrylate (V1F) were subjected to long‐term tests in water and in humid environments. Results of stress‐free aging tests showed a progressive reduction of strength both in water and in the atmosphere of 90% r.h. at 32.6°C. Stressing the fibers up to 517 MN/m2 (75 kpsi) during aging did not result in additional loss of strength. Static fatigue tests in 90% r.h., 32.6°C, showed that the fatigue strength decreased monotonically with time of exposure in accordance with the power law of Charles. However, there were indications that Charles' theory might not be obeyed over an extended test period.
Effect of carboxylic monomers on acid distribution in carboxylated polystyrene latices
Authors: Vijayendran B. R.
Published: April 2003

A study was made of the effect of carboxylic monomers, such as itaconic acid, acrylic acid, and methacrylic acid, on the relative distribution of acid in the aqueous serum phase to that on the latex surface to that buried in the particle of carboxylated polystyrene latices prepared by emulsion polymerization. The relative acid distribution of the carboxylated latices was determined by the conductometric titration method of Hen. Effect of carboxylic monomer levels and latex particle size on acid distribution ratio are given. It is shown that itaconic acid, being the most hydrophilic and having the least solubility in styrene, tends to distribute itself in favor of the aqueous serum phase, while acrylic acid, which has limited solubility in styrene and being sufficiently hydrophilic, tends to prefer the particle surface predominantly. Methacrylic acid, being the most hydrophobic of the three carboxylic monomers studied and having good solubility in styrene, is shown to be concentrated inside the particle core. The observed results are compared with other similar findings in the literature and analyzed in the light of accepted mechanisms for emulsion polymerization of carboxylated styrene systems.
Effect of coagulation conditions on crystal modification of poly(p‐phenylene terephthalamide)
Authors: Haraguchi Kazutoshi , Kajiyama Tisato , Takayanagi Motowo
Published: April 2003

Poly(p‐phenylene terephthalamide)(PTTA) films were prepared from sulfuric acid solution with various coagulants. X‐ray diffraction and infrared absorption measurements revealed that the crystal structure of the film coagulated with water showed a new crystal modification II, which was different from the one previously reported by Northolt and Tadokoro et al. The latter structure is called here modification I. Modification II coagulated with water from a solution of lower polymer concentration irreversibly transformed to modification I upon annealing, whereas modification II prepared from highly concentrated solution was thermally stable and scarcely transformed to modification I upon annealing. A liquid crystal‐like swollen structure was found in the intermediate stage of the formation of modification II. In this swollen state, x‐ray diffraction revealed that water molecules are included in hydrogen‐bonded planes and the intermolecular spacing along the van der Waals force direction was unaffected by the existence of the water and remained constant throughout the process of regeneration. Both modifications I and II were found to be stable on treatment with boiling solvents. The transformation of the swollen structure to modification I took place in boiling methanol and acetone.
Bulk polymerization of acrylonitrile. I. An experimental investigation of the kinetics of the bulk polymerization of acrylonitrile
Authors: Garcia‐Rubio L. H. , Hamielec A. E.
Published: April 2003

A comprehensive experimental investigation is reported of the bulk polymerization of acrylonitrile (AN) to limiting conversion using 2,2′‐azobisisobutyronitrile (AIBN) as initiator at 40°, 60°, and 80°C. Molecular weight development was followed by gel permeation chromatography (GPC).
Thermal degradation of cellulose in air and nitrogen at low temperatures
Authors: Shafizadeh F. , Bradbury A. G. W.
Published: April 2003

Thermal analysis and kinetic studies have shown that oxidative reactions are responsible for acceleration in the rates of weight loss and depolymerization of cellulose on pyrolysis in air at temperatures below 300°C. The oxidative reactions include production of hydroperoxide, carbonyl, and carboxyl groups, which have been investigated at lower temperatures along with the rates of depolymerization and production of carbon monoxide and carbon dioxide. The experimental results are consistent with an autoxidation mechanism involving initiation, propagation, and decomposition reactions. At temperatures above 300°, the rate of pyrolysis is essentially the same in both air and nitrogen, indicating that thermal degradation is independent of the oxidative reactions.
Characterization of polyethyleneimine modified with organotin halides. Thermal, solubility, and fungal properties
Authors: Carraher Charles E. , Giron David J. , Woelk William K. , Schroeder Jack A. , Feddersen Mary F.
Published: April 2003

Modified polyethyleneimine products are hydrophobic with products from monohalotin reactants soluble in HMPA, DMSO, CHCI3 and 2,4‐pentanedione, while products from dihalotin reactants are insoluble in all solvents. Antifungal activity varies markedly with the nature of the tin moiety. For products from triphenyltin chloride, antifungal activity is widespread and suitable to about 40 ppb of the polymer, which is clearly acceptable for medical and industrial uses. Thus, such modified polymers can be used as retarders of fungi related rot and mildew. The products show moderate high‐temperature stabilities.
A novel approach to viscometric parameters of polymer solutions
Authors: Chee K. K.
Published: April 2003

A three‐parameter equation is put forward to evaluate the [η] of polymer solution from a wide range of concentrations, up to a relative viscosity of 100. The equation is tested by viscometric data of polystyrene, poly(vinyl chloride), poly(1‐vinylnaphthalene), poly(2‐vinylnaphthalene), and poly(4‐vinylbiphenyl) at different temperatures and in a variety of solvents including mixed solvents. A statistical method is employed to analyze the experimental data. It is found that the values of [η] obtained by the new equation are consistently lower than those derived from the Huggins equation. However, the discrepancy is not more than 3% on average, and it does not affect the values of Mark‐Houwink constants significantly. Other parameters of the equation are also computed.
The characterization of nylon 6 filaments by x‐ray diffraction
Authors: Stepaniak R. F. , Garton A. , Carlsson D. J. , Wiles D. M.
Published: April 2003

A method is described for calculating crystallinity indices and crystalline orientation functions for the α and γ components of the crystalline phase of nylon 6 filaments using wide‐angle x‐ray diffraction (WAXS) analysis. The method is shown to be applicable to a wide range of filament samples (“conventional” as‐spun, fast spun, drawn, and annealed) even when only a single broad diffraction maximum is observable from the WAXS photograph. The component indices can be used to illustrate differences present in the filament microstructure which would be unobservable if a total crystallinity index, such as that determined by density, were determined alone. For example, the initially mixed α–γ structure is retained in low‐temperature drawing (75–150°C) of nylon 6 fiber, but the predominantly α form is produced at higher draw temperatures.
Durable flame resistance via reaction of cotton cellulose bearing aromatic amino groups with tetrakis(hydroxymethyl)phosphonium chloride
Authors: Hebeish A. , Waly A. , El‐Kashouti M. A.
Published: April 2003

Chemically modified cotton fabric samples having different amounts of aromatic amino groups were prepared. These modified samples were reacted with tetrakis(hydroxymethyl)phosphonium chloride (THPC) under a variety of conditions using the pad‐dry–thermofixation technique. The extent of the reaction (expressed as %P) was dependent of the degree of chemical modification of cotton, temperature and time of heating, and pH of the treating bath as well as incorporation of Lyofix CHN (N‐methylol finishing agent), MgCl2·6H2O (catalyst), and urea at various concentrations. THPC did react with the modified cotton having a nitrogen content over a range of 0.4%–1.3% even in the absence of catalyst at a temperature as low as 30°C for 10 min to impart durable flame resistance to cotton. Increasing the temperature up to 80°C enhanced considerably the extent of reaction; he latter remained practically constant upon further increase in temperature. The reaction was favored in acidic media (pH 4–6), whereas alkaline media (pH 9–11) inhibited it. Incorporation of Lyofix CHN (9%), MgCl26H2O (1%), and urea (5%) along with THPC (25%) in the treating bath required a curing temperature of 120°C and a curing time of 5 min to achieve a fabric containing as much as 2.7% phosphorus with excellent durable flame resistance. A tentative mechanism of the reaction between THPC and the modified cotton was also elicited.
Comparisons of the cure of phenol–formaldehyde novolac and resol systems by differential scanning calorimetry
Authors: Chow S. , Steiner P. R.
Published: April 2003

Comparisons were made of differential scanning‐calorimetric (DSC) thermograms of both liquid and powdered commercial phenol–formaldehyde resins. By a combination of the results from analyses under a variety of conditions, such as ambient pressure, high pressure, using freeze‐dried samples, and also by direct observation of the resin‐curing process in wood‐veneer assemblies, the curing reactions of phenol–formaldehyde resins were found to differ for resol and novolac systems. At a heating rate of 10°C/min, the resol resin showed endothermic curing reactions at temperatures of about 150°C, while the novolac‐type resin showed an exothermic peak maximum at about 160°C. Results are presented to show how DSC can be used to differentiate between a resol and novolac system.
Thermoelastic properties of urethane elastomers
Authors: Nierzwicki W. , Szpilewicz E.
Published: April 2003

Several polyurethanes based on poly(ethylene adipate), 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol, and 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane were prepared. The thermoelastic properties of these polyurethanes depend on compositional variables and are interpreted in terms of the extent and stability of microphase separation.
Kinetics of the base‐catalyzed reactions of cyclo‐octameric and catenapolymeric sulfur with dithiol
Authors: Bordoloi Binoy K. , Pearce Eli M.
Published: April 2003

The base‐catalyzed sulfur‐1,2‐ethanedithiol reactions appear to follow pseudo first‐order kinetics as determined by TGA. The activation energy has been determined to be 26.1 kcal/mol with either cyclo‐octameric or catenapolymeric sulfur.
Polymers with pendant isocyanate groups. III. Synthesis and properties of poly(styrene‐co‐acrylonitrile‐co‐styrylisocyanate)
Authors: Liebersohn Aharon , Kohn David H.
Published: April 2003

The terpolymer poly(styrene‐co‐acrylonitrile‐co‐styrylisocyanate) was synthesized by radical initiation directly from styrene, acrylonitrile, and cinnamoyl azide. The monomer feed–terpolymer composition relationship was determined by Slocombe's triangular graph. The solubility, intrinsic viscosity, and melting range of the various terpolymers and the chemical reactions of the pendant isocyanate groups toward alcohol and amines were investigated.
Composite reverse osmosis membranes prepared by plasma polymerization of allylamine. Evaluation of membrane performance for the treatment of washwater and its components
Authors: Hinman P. V. , Bell A. T. , Shen M.
Published: April 2003

Reverse osmosis membranes prepared by plasma polymerization of allylamine–nitrogen mixtures over a porous substrate were evaluated for the rejection of components present in washwater. The membranes exhibited high rejections for sodium chloride, potassium chloride, detergent, and dextrose. High rejections of urea could be achieved, but only at a sacrifice of water flux. Lactic acid could also be rejected but caused a degradation of the plasma‐deposited layer.
Influence of curing agent concentration and curing temperatures on the thermostability of styrene–acrylonitrile–acrylamide–trimethylolpropane trimethacrylate copolymer systems
Authors: Zeldin Arkady N. , Kukacka Lawrence E. , Fontana Jack J. , Carciello Neal R. , Reams Walter
Published: April 2003

Thermogravimetric (TGA) and infrared (IR) analyses were used to determine the thermal stability of a polymer system consisting of styrene–acrylonitrile–acrylamide–trimethylolpropane trimethacrylate. This study indicates that increases in curing temperature and the use of two initiators with different activities decreases the percentages of unreacted monomers. This increases the thermal stability of the polymer. To prove this, dynamic and isothermal TGA were used. The change in typical functional groups found by IR spectra also confirms this observation.
Compressive creep of flexible polyurethane foam
Authors: Campbell Gregory A.
Published: April 2003

The compressive creep rate of polyurethane foams was found to be a complex function of deflection and time. The complexity has been shown to be related to the buckling of the cell struts as the foam is compressed. Of the parameters normally varied in the foam formulation, both the polyol molecular weight and the water content of the foam formulation seemed to have a measureable effect on the creep rate.
Ionically crosslinked poly(acrylic acid) membranes. II. Dry technique
Authors: Habert A. Claudio , Burns Charles M. , Huang Robert Y. M.
Published: April 2003

The ionic crosslinking of poly(acrylic acid) for dialysis and reverse osmosis applications has been studied. A new dry technique has been developed that is faster than the wet technique reported in the previous paper to synthesize aluminum/poly(acrylic acid) membranes. It is based on casting a solution containing both the aluminum salt and the unneutralized poly(acrylic acid) (PAA) and subjecting the cast film to a heat treatment (curing step) to promote ionic crosslinking. Postcuring treatment in nonsolvents for PAA such as acetone induced structural modifications in the membrane. Membranes with optical clarity ranging from colorless and transparent to white and opaque were obtained and were characterized by their water and aluminum contents. Transport properties of these membranes were investigated and indicated a selective rejection of ionic solutes such as NaCl compared to organic solutes such as ethylene glycols. Typical results for reverse osmosis under static conditions at fluxes of 1250 g/hm2 (0.75 U.S. gallons/ft2‐day) gave rejections of 85% for a feed of 0.1% (by wt.) NaCl at 600 psi. Much lower rejection (28%) for ethylene glycol suggests the possible use of these membranes in the fractionation of mixtures of ionic and nonionic solutes by reverse osmosis.
Radiation‐induced polymerization of ethylene in a pilot plant. II. Development of wet‐wall process
Authors: Takehisa Masaaki , Watanabe Hiromasa , Kurihara Hirondo , Takasaka Yoshio , Maruyama Yoshio , Miyanaga Kazukiyo , Suwa Takeshi , Nakajima Hayato , Yamaguchi Kouichi , Tohei Masamichi , Kawakami Waichiro , Watanabe Terutaka , Senrui Shiro , Machi Sueo
Published: April 2003

Radiation‐induced polymerization of ethylene using tert‐butyl alcohol aqueous solution as a medium was carried out in a pilot plant with 10 liter reactor at pressures of 100 to 400 kg/cm2, ethylene feed rates of 1.2 to 11.8 kg/hr, medium feed rates of 0 to 100 liter/hr, dose rates of 0.6 × 105 to 1.4 × 105 rad/hr, and at room temperature. The space‐time yield and molecular weight of polymer were in the range of 1.2 to 16.7 g/liter hr and 6 × 103 to 2 × 105, respectively. The space‐time yield and molecular weight increased with pressure and mean residence time. The space‐time yield was the maximum at an ethylene molar fraction of 0.5. The produced polymer was continuously taken out from the high‐pressure system as a slurry. The amount of deposited polymer to the reactor wall was markedly decreased, and five full days continuous operation was successfully performed with the space‐time yield of 13.5 g/liter hr.
The kinetics of polyesterifications. IV. Polyol from BHET and adipic acid and its urethanes
Authors: Lin Chen‐Chong , Yu Ping‐Chang , Huang Li‐Chau
Published: April 2003

New polyol containing aromatic rings was prepared from BHET, or BHET/ethylene glycol mixtures and adipic acid. In this new system, the kinetics of polyesterification were investigated and were shown to follow the kinetic equations proposed by Lin and his co‐workers which were obtained by modifying Flory's theory. Polyurethane elastomers were prepared by reacting these polyols and toluene diisocyanate (TDI) in DMF solution with NaCN as a crosslinking catalyst at room temperature. Their physical properties such as density, gel fraction, swelling ratio, mechanical properties, etc., were measured. High values of elastic modulus are due to the rigid segment of BHET. By varying the molar ratio of diisocyanate and polyester, polyurethanes with different crosslinking densities can be obtained. The relationship between physical properties and crosslinking density was shown to follow the general theory of rubber elasticity.
Permeability of phenol through cellulose acetate membranes by reverse osmosis in various alcoholic systems
Authors: Nomura Hiroshi , Senō Manabu , Takahashi Hiroshi , Yamabe Takeo
Published: April 2003

Reverse osmosis separation of phenol in various alcoholic solutions using porous cellulose acetate membranes was investigated. The permeation behavior of phenol was measured for cellulose acetate membranes having various pore size distributions which were prepared by annealing at four different temperatures. Some differences were found between the aqueous and the alcoholic solutions in solute permeabilities and product rates. Membranes annealed at 90°C showed higher permselectivity than membranes annealed at lower temperatures. The pore character was classified into two types according to the relation of the product rate of 1‐propanol and that of water. It was found in a series of alcoholic solutions that the permeability of phenol, the product rate, and the apparent partition coefficient are closely related to the carbon number of the alcohols, but the values of Jv × η (ca. 1.25 × 10−4 poise·m3/m2·day) and of the permselectivity coefficient (ca. 0.83) remain constant. The result was analyzed by using the three‐dimensional solubility parameter to obtain some information for the partition mechanism of solutes in aqueous and alcoholic solutions.
Quick identification and analysis of plasticizers in PVC by programmed‐temperature gas chromatography using the best stationary phases
Authors: Messadi Djelloul , Vergnaud Jean‐Maurice
Published: April 2003

A quick and safe identification method is shown for plasticizers in PVC using programmed‐temperature gas chromatography. Plasticizers were identified by their retention index values measured by using normal paraffins. Several stationary phases with quite different polarity are proposed: with silicone polymers (SE 30, OV 17, and QF 1) and a porous polymer such as Tenax. Operational conditions were optimized. The initial column temperatures was chosen at a low value of 100°C with the first three phases and 180°C for the fourth. The best rate of temperature increase with time seemed to be 10°C/min. The calculation method for retention values (temperature, time, indices) was chosen just because it needed no approximation. Thermodynamic values for the solution of plasticizers were measured by using isothermal chromatography with all the stationary phases. Our method allows the analyst to operational conditions (solvent, percent, temperature) for chromatography, to solve his own problem by making use of a pocket computer. Quantitative analysis of plasticizers was obtained with good accuracy after a previous extraction and the addition of normal paraffin as internal standard.
Phenolic and tannin‐based adhesive resins by reactions of coordinated metal ligands. I. Phenolic chelates
Authors: Pizzi A.
Published: April 2003

Bivalent and trivalent metallic ions, respectively, accelerate and inhibit the reaction of phenols with formaldehyde. The catalytic effect of these metallic ions is equivalent, though more marked, to that of hydrogen ions, and it is due to their stronger charge. Metallic ions/phenols/formaldehyde complexes are formed. The stability of these complexes and mainly their rate of metal exchange in solution are the determining factors in the accelerating or retarding action. Identified stable chromium (III)–resorcinol–formaldehyde and chromium (III)–phenol–formaldehyde complexes have slow rates of metal exchange and inhibit the resorcinol–formaldehyde and phenol–formaldehyde reactions. The opposite is valid for lead (II), zinc (II), and other bivalent metallic ions. A scale showing the order of the accelerating effect of a series of metallic ions is given. The presence of polymeric complexes has also been observed.
Humid aging of plastics: Effect of molecular weight on mechanical properties and fracture morphology of polycarbonate
Authors: Gardner Robert J. , Martin John R.
Published: April 2003

Polycarbonate tensile bars were aged up to 18 months at 0%, 75%, and 100% relative humidity and temperatures of 65–93°C. In the humid aged samples hydrolysis caused progressive reductions in molecular weight. Below a critical molecular weight (Mw = 33,800, Mn = 14,300) tensile strength dropped off rapidly. A transition from ductile to brittle failure was also observed at that point. Extrapolations indicate that the ductile–brittle transition at 38°C will be reached after 5 years at 100% relative humidity for the polycarbonate studied. Elongation was affected even in the early stages of hydrolysis. This suggests that whenever the degradation mechanism is a molecular weight reduction, toughness will be affected before the strength properties are lost. Mechanical properties are affected by annealing and antiplasticization which reduce localized stresses and increase short‐range order. The brittle fracture surfaces of polycarbonate consist of four distinct regions. The size of the regions and the prominence of the features changed as the molecular weight decreased.
Effects of phosphorus‐containing flame retardants on pyrolysis of cotton cellulose
Authors: Franklin W. E. , Rowland S. P.
Published: April 2003

Unmodified cotton and cottons finished with high levels of seven different phosphorus‐containing flame retardants were pyrolyzed in a temperature‐programmed solid probe of a mass spectrometer, and mass spectra were recorded continuously throughout the pyrolyses. The spectra at the maximum rates of volatiles evolution during the pyrolyses were analyzed to determine relative amounts of water, carbon monoxide, carbon dioxide, furfural, furyl hydroxymethyl ketone, hydroxymethylfurfural, levoglucosan, and 1,6‐anhydro‐β‐glucofuranose. These volatile materials accounted for 64% to 90% of the total ionization in the spectra. The flame retardants increased the fractions of nonfuel volatiles (water and carbon dioxide) and decreased those of anhydroglucoses, but had less effect on the carbon monoxide and furan derivatives. The flame retardant fabrics differed greatly in the fractions of anhydroglucoses (from 1% to 23%) and water (from 19% to 57%) in their pyrolysis products. These results indicate that mechanisms of flame retardant action differ among phosphorus‐containing finishes.