bluuebunny/crossref_metadata_2025 huggingface dataset:
Compatibilizing effect of a diblock copolymer of isotactic polystyrene and isotactic polypropylene in blends of the corresponding homopolymers
Authors: Giudice L. Del , Cohen R. E. , Attalla G. , Bertinotti F.
Published: April 2003

A high molecular weight polymer mixture was obtained from a sequential Ziegler–Natta polymerization of styrene and propylene. After removing unwanted homopolymers from the reaction product, the remaining copolymer was subjected to extensive molecular and morphological characterization. The results of these experiments indicate that the purified material is a diblock copolymer of isotactic polystyrene and isotactic polypropylene, with each block having a molecular weight in the range of 225,000 g/mol. This block copolymer was incorporated in varying amounts into blends of isotactic polystyrene and isotactic polypropylene homopolymers. At low concentrations of copolymer (<20 wt %), the diblock functions as a dispersing agent, significantly reducing the size of domains in the heterogeneous blends. At higher copolymer concentrations, a dramatic improvement in the adhesion across the domain boundaries is also observed. The favorable effects of the copolymer on mechanical properties are demonstrated in the results of tensile impact experiments.
Effect of heat treatment on nylon‐6 tire cords
Authors: Mukherjee A. K. , Gupta B. D. , Kulkarni S. G. , Chauhan D. S. , Chakravarty S. N.
Published: April 2003

The behavior of nylon‐6 tire cords at elevated temperature has been evaluated. The heat treatment of cords at 200°C for 16 h was found to reduce their tensile properties considerably. This has been attributed to the decrease in average molecular weight and change in molecular weight distribution as ascertained by fractionation studies. Heat setting of cords in the temperature range of 180–210°C without any applied tension showed some decrease in tensile properties. This has been ascribed to the higher degree of shrinkage of the cords and hence increased chain folding in the molecular structure. However, irrespective of time and temperature of heat treatment, shrinkage was reduced with increasing tension on the cord. Effect of heat setting on density and crystallinity was also evaluated.
Dissolution rates of poly(methyl methacrylate) films in mixed solvents
Authors: Cooper Wendy J. , Krasicky Philip D. , Rodriguez Ferdinand
Published: April 2003

A laser interferometer has been used to measure in situ the dissolution rates of thin films of poly(methyl methacrylate) (PMMA). The most significant finding is that addition of small amounts of a low‐molecular weight nonsolvent can increase the rate obtained with a higher molecular weight solvent. In this study, silicon wafers were coated with polymer (about 1 μm thick) and annealed at 155°C for 1 h. The dissolution rates were measured at 17.5, 22.5, and 27.5°C. All the mixtures contained methyl ethyl ketone (MEK) (2‐butanone), as the major component. The minor component was water, methanol, ethanol, 1‐propanol, 2‐propanol, or ethylene glycol. Water and methanol showed the greatest effects. Both were able to increase the dissolution rate as much as two‐fold. All the mixtures exhibit the same activation energy (25 kcal/mol) despite their wide differences in dissolution rate.
Grafting of cellulose–thiocarbamate with vinyl monomers: Antimicrobial activity
Authors: Nagieb Zenat A. , El‐Gammal Amira A.
Published: April 2003

Grafting of vinyl monomers onto cellulose‐thiocarbamate was carried out using ceric ammonium sulfate (CAS) as an initiator. The graft yield was found to depend on the amount of thiocarbamate groups, initiator, and monomer concentrations as well as temperature. The graft yield increased with increasing (CAS) concentration. The reactivity of vinyl monomers studied followed the order ethyl acrylate>acrylonitrile. A comparison between the graft yields obtained with the modified cullulose indicated that cellulose thiocarbamates having less than 1.1% nitrogen showed lower graft yields than the unmodified cellulose. Above this, cellulose thiocarbamate was much more amenable to grafting than the unmodified cellulose. The grafted cellulose thiocarbamates exhibited high antifungal activity and had no effect on gram‐negative, gram‐positive bacteria and yeast. The maximum zone of inhibition was obtained after grafting with 2 h which resulted in 43 and 50% add‐on polymer in the cases of acrylonitrile and ethyl acrylate, respectively. Grafted cellulose thiocarbamates with acrylonitrile had higher potency for antifungal activity than that grafted with ethyl acrylate.
Effects of die temperature on extrudate swell in screw extrusion
Authors: Henderson A. M. , Rudin Alfred
Published: April 2003

Extrusion of a hot polymer melt through a cooler die zone substantially increases the extrudate swell of some thermoplastics. This effect was examined for commercial samples of low‐density polyethylene, polypropylene, and polystyrene. Two conflicting effects come into play during extrusion of a thermoplastic. Colder melt temperatures promote increased extrudate swell, but the same conditions also facilitate molecular disentanglement and reduced melt elasticity and die swell. Since the extrusion process itself may affect the relation between die swell and melt temperature, laboratory‐scale measurements for the design of processes like blow molding are better carried out with small‐scale screw extruders than with capillary rheometers. For some applications it may be advantageous to use a polymer whose die swell is particularly responsive or unresponsive to die temperature variations. The procedure described in this article can be used effectively to monitor this characteristic.
Membrane potentials and permeation of NaCl in poly(vinyl alcohol‐co‐itaconic acid) membranes
Authors: Higuchi Akon , Iijima Toshiro
Published: April 2003

The membrane potential and permeability of NaCl were measured for six crosslinked poly(vinyl alcohol‐co‐itaconic acid) membranes having various water contents [0.25≤H≤0.83 H2O (g)/swollen membrane (g)] and interpreted by means of an equation derived from Schlögl′s theory. Both results of the membrane potential and the permeability of the membranes having H≥0.34 could be satisfactorily interpreted by the theory. The permeability of NaCl in the membrane of H=0.25 gave, however, an increasing tendency with the decrease of the upstream concentration lower than 0.04 mol/L. It was considered that the concentration dependence reverse to what was caused by the Donnan exclusion might be due to the concentration dependence of the thermodynamic partition coefficient in nonfreezing water of the membrane. By the equation thus derived the membrane potential and the permeability of NaCl in the membrane of H=0.25 were expained qualitatively. The mobility ratios of Na+ and Cl− and the effective charge density in the membranes were discussed.
Dielectric properties and stress–strain measurements of chloroprene rubber based on different carbon black fillers
Authors: Lawandy S. N. , Abd‐El‐Nour K. N.
Published: April 2003

A systematic dielectric study of 1 kHz was carried out on chloroprene rubber, mixed with different types of carbon black and different concentrations. The measurements were carried out at room temperature (25°C). It was found that better dielectric properties cannot be achieved when the carbon black concentration exceeds 60% for MT, 40% for SRF, and 20% for both HAF and SAF. In addition, the relation between the dielectric constant ε and the modulus of elasticity E for the different mixes were studied. From this study it was found that, up to certain carbon black volume concentration (depending on the filler type), the modulus equation Ef = E0 (1 + 0.67φC + 1.62φ2) can be used to relate the dielectric properties εf and εo of carbon black filled and unfilled rubber compounds. The dielectric measurements were also related to the particle size and the structure of carbon black.
Effect of the chemical modification of cotton fabric with propane sultone and through grafting with acrylonitrile on the dyeability with basic dyes
Authors: Sabaa M. W. , Watamoto H. , Sakamoto M. , Furuhata K.
Published: April 2003

The sulfonated cotton fabrics (sulfur content: 0–0.52%), obtained by the treatment with propane sultone, were subjected to graft copolymerization with acrylonitrile. The values of the % graft of the sulfonated cotton fabrics were higher than those of untreated cotton fabrics. The sulfur contents of the sulfonated cotton fabrics, however, affected little the % graft. The sulfonated and grafted cotton fabrics absorbed basic dyes, Methylene Blue, Diamond Green, and Cathilon Red. The color fastness of these dyes towards light from a Xenon lamp and towards ultraviolet radiation was significantly improved by the introduction of polyacrylonitrile onto cotton.
Infrared and liquid chromatographic characterization of epoxy cresol novolac‐phenol formaldehyde novolac‐tertiary amine resin systems
Authors: Belton D. J. , Sullivan E.
Published: April 2003

The subject of this paper is an infrared and liquid chromatographic characterization of epoxy molding compounds of importance in the microelectronic manufacturing industry. A complete infrared description of resin extracts from 4000 to 700 cm−1 is given for three nondisclosed commercial extracts via comparisons with model epoxy cresol novolac and phenol formaldehyde novolac resins and by observing those spectral alternations affected during cure. In addition, both the molecular weight distributions and the methodology of obtaining such for the resin and hardener components of the extracts are described. These results are based upon reversed phase liquid chromatography and infrared spectroscopic measurements. The analysis described in this paper demonstrates significant differences among materials that, by chromatography alone, appear to have only subtle variations in both the resin and hardener molecular weight distributions. These differences include not only the quantity of resin or hardener of a particular oligomeric molecular weight, but also the apparent resin‐to‐hardener stoichiometry of the combined system.
The effects of morphology and hygrothermal aging on water sorption and transport in Kapton® polyimide
Authors: Yang D. K. , Koros W. J. , Hopfenberg H. B. , Stannett V. T.
Published: April 2003

A comparison of water sorption and diffusion behavior in 2 mil, as‐received, Kapton

= Trademark of E.I. Dupont de Nemours Inc.

film, and in otherwise identical but hygrothermally aged samples, suggests chemical differences between the samples. These differences can be related to known polyimide chemistry and the specific history encountered by the samples. Although the sorption isotherms are similar for an as‐received 0.3 mil sample studied earlier and for the as‐received 2 mil samples studied here, the diffusion coefficient of water in the as‐received 2 mil sample is approximately 300% larger than in the as‐received 0.3 mil sample. This large effect is believed to be related to the presence of small, paracrystalline aggregates with large aspect ratios. Differences in orientation measured by birefringence for the two samples suggest that the barrier properties of Kapton® are strongly affected by the detailed morphological organization of the ordered aggregates. Comparison of the sorption isotherms for the as‐received and hygrothermally aged 2‐mil films suggests a significant increase in the hydrophillic nature of the aged film. This change is consistent with an apparent chemical reaction between water and uncyclized amic acid residues in the film. The tendency for water to cluster in as‐received Kapton® is essentially eliminated by the chemical modification associated with hygrothermal aging. The hygrothermal aging produces a dramatic reduction in the water vapor diffusion coefficient at low vapor activities but a rather modest change at high activities.
Polymer complex from copolymers of acrylonitrile and ionic vinyl benzyl compounds
Authors: Senuma Masao , Kuwabara Shigeru , Kaeriyama Kyoji , Hase Fumio , Shimura Yukio
Published: April 2003

Copolymerization of sodium vinyl benzyl sulfonate (VBS) or vinyl benzyl trimethyl ammonium chloride (VBQ) with acrylonitrile (AN) gave polyelectrolytes of preferable solution viscosities. The blending of these two copolymers in N,N‐dimethyl formamide (DMF) produced polymer complexes with ionic linkages, of which the following properties were examined. The maximum in the tan δ temperature was increased by complex formation. Freundlich‐type dye adsorption and much better dyeability than on polyacrylonitrile was observed. Electric resistivity decreased with the introduction of ionic moiety. Permeability of water increased with the number of ionic sites. Homogeneous films could be cast from DMF and dimethyl sulfoxide (DMSO) solutions.
Changes of spin–spin relaxation time for EPR composites during mixing process
Authors: Furuta Motonobu , Hikasa Tadashi , Kato Eiichi
Published: April 2003

The changes of the mobility of rubber molecules for carbon black‐filled EPR composites during mixing process in an internal mixer have been elucidated from T2 measurement using pulsed nuclear magnetic resonance (NMR). The thickness of the tightly bound region which is formed by the direct interaction with carbon black was stabilized with mixing but the restriction of the molecular mobility increased with further mixing. The amount of the loosely bound region increased considerably throughout the mixing, indicating that this region is formed by entanglement and crosslinking of the molecules. T2 of the mobile region which is a predominant part in the composites is independent of the mixing time. EPR has the thinner tightly bound shell and longer T2s compared with EPDM, showing the effect of unsaturated bond in EPDM which can become a strong bond site with carbon black.
Physical properties of vinyl chloride‐propylene copolymers
Authors: Langsam Michael , Mango Philip A.
Published: April 2003

The polymerization conditions that control the physical properties of vinyl chloride‐propylene copolymers have been examined, and the interaction between these polymerization conditions and the melt rheology, intrinsic viscosity, and bound propylene level of the copolymer have been quantified into a series of process control relationships. The interaction between primary and secondary suspension systems have been optimized for these copolymers to maximize the resin porosity. Binary initiator systems have been identified to overcome the degradative polymer kinetics associated with propylene comonomer.
Gas transport in poly(vinylidene fluoride): Effects of uniaxial drawing and processing temperature
Authors: El‐Hibri M. J. , Paul D. R.
Published: April 2003

This paper reports on the gas sorption and transport properties of poly(vinylidene fluoride) (PVF2) and on the effects uniaxial drawing and processing temperature have on these properties. Sorption and transport were first examined for “as‐received” commercial Kynar PVF2 film at 35°C. This film was 54% crystalline by weight. Solubility, diffusion, and permeability coefficients were measured for He, H2, Ar, O2, N2, CH4, and CO2. The solubility coefficient and the diffusion coefficient D were correlated with the Lennard–Jones potential and mean molecular diameter of the gas, respectively. Uniaxial drawing of PVF2 films was performed up to a draw ratio of 3.7 and over the temperature range 75–140°C. Transport properties were correlated with the extent of draw and drawing temperature. The permeability P and D were found to significantly decline with uniaxial drawing; the magnitude of this effect was dependent on both the drawing temperature and the molecular size of the penetrant considered. Roduetions in P and D became progressively more pronounced with increasing molecular diameter and with decreasing drawing temperature (down to a limit of about 75°C), which reflects an increase in effectiveness of drawing at low temperatures. PVF2 films annealed above 75°C showed an increase in P and D as opposed to the effect of drawing. The solubility of various gases in PVF2 was not found to be sensitive to processing treatments such as drawing and annealing, in agreement with the relatively small changes observed in free volume. PVF2 films subjected to various treatments were characterized by DSC, density, birefringence, and dynamic mechanical measurements. Gas transport measurements appear to provide a more sensitive and hence more viable measure of the effectiveness of drawing than these other techniques. Drawing PVF2 in the melt state was found to increase P and D, in contrast with the effects observed for solid‐state drawing. The results have been interpreted in terms of existing theories on morphology and microstructure in semicrystalline polymers.
Polyethlene‐modified bitumen for paving applications
Authors: Jew P. , Shimizu J. A. , Svazic M. , Woodhams R. T.
Published: April 2003

In cold regions, transverse cracking of asphaltic paving materials is a serious problem which has not been completely resolved despite much effort. In this investigation, the low temperature stress–strain properties of bitumen containing dispersed polyethylene were measured over the temperature range from −40 to 0°C and compared with unmodified bitumen in an attempt to develop a tougher, more ductile crack‐resistant binder for paving materials. Several grades of polyethylene were individually dispersed in liquid, heated bitumen to produce therein colloidal suspensions of polyethylene. The viscosities of these suspensions were determined at various temperatures and concentrations for each grade of polyethylene. Despite rather large differences in composition, molecular weight, and crystallinity of the polyethylenes, the differences in viscosity at the same concentration were relatively minor. However, the viscosity was very sensitive to the polyethylene concentration and the mixture became difficult to process at concentrations greater than 10 percent by weight. Thesee hot mixtures were then cast into rectangular beams for flexural testing at temperatures below zero degrees Celsius. Near the optimum polyethylene concentration of 8 percent by weight, the bitumen mixture possessed increased flexural strength, increased flexural modulus, increased elongation, and increased fracture energ at temperatures near −30°C. In one example the energy to fracture was increased ninefold compared to a standard 80/100 pen. bitumen control at −20°C. Mix design results are presented for a typical aggregate and compared with a MTC HL4 hot‐mix paving formulation which is used extensively throughout Ontario. The polyethylene‐modified asphalt concrete mix displayed a curious increases in both the Marshall flow and the Marshall stability values. Dynamic mechanical measurements confirmed the expected increase in resilient modulus at temperatures above zero degrees Celsius. The Marshall briquets containing polyethylene also exhibited slightly greater wet strength retention after prolonged immersion in water. These observations are consistent with the published data for commercial Novophalt paving materials developed in Austria and predict that the use of polyethylene in asphaltic hot‐mix paving materials can extend service temperature range at both high and low temperatures, thereby simultaneously reducing both pavement distortion (rutting) and low‐temperature cracking, so that pavement lifetimes can be more than doubled. The cost of such modification can be substantially reduced if scrap or reclaim polyethylene is employed instead of virgin polyethylene. Dispersing agents, such as Shell Chemical Kraton G block copolymers were advantageously employed to control the emulsion stability, particle size, and compatibility of the dispersed polyethylene phase.
Phase behavior of blends of aliphatic polyesters with a vinylidene chloride/vinyl chloride copolymer
Authors: Woo E. M. , Barlow J. W. , Paul D. R.
Published: April 2003

A series of aliphatic polyesters having CH2/COO ratios from 2 to 14 in their repeat units were blended with a copolymer of vinylidene chloride containing 13.5% by weight of vinyl chloride. Blends of polyesters having CH2/COO < 4 did not form completely miscible amorphous phases, whereas polyesters having CH2/COO ≥ 4 did form completely homogeneous amorphous phases for all temperatures below the decomposition point except for the polyester with CH2/COO = 14 which showed reversible phase separation on heating, i.e., lower critical solution temperature behavior. Interaction parameters were estimated by melting point depression and by analog calorimetry. The behavior reported here is qualitatively similar to that reported earlier for blends of aliphatic polyesters with poly(vinyl chloride), polyepichlorohydrin, polycarbonate, styrene–allyl alcohol copolymers, and the hydroxy ether of bisphenol A.
Mechanism and kinetics of the reaction of acrylic polyols with hexa (methoxymethyl) melamine
Authors: Collette J. W. , Corcoran P. , Tannenbaum H. P. , Zimmt W. S.
Published: April 2003

New procedures have been developed to study the mechanism and kinetics of the crosslinking of acrylic polyols with hexa (methoxymethyl) melamine. Both the rate of gel formation and alcohol release are found to be affected by the concentration and the nature of the catalyst and to be proportional to the hydrogen ion concentration. The rate of gel formation can be modeled by using the Miller and Macosko procedure with the input consisting of the polymer composition and the rate of release of reaction products. The correlation between calculated and experimentally determined quantity of gel formed is good when the reactions are slow, but becomes poor when gel formation is rapid, suggesting that the formation of large rings is favored by rapid reaction. The rate of gel formation shows much less variation among different polymer systems than does the rate of release of reaction products from the crosslinking reaction.
Epoxy thermosetting systems based on cycloaliphatic diamines
Authors: Sabra A. , Pascault J. P. , Seytre G.
Published: April 2003

We have investigated the reaction kinetics of a liquid prepolymer DGEBA with isophorone diamine (IPD) and menthane diamine (MNDA). IPD is 10 times more reactive than MNDA. With mixtures of these two hardeners we have the possibility to control the reactivity of the curing agent and the pot life of the system. The kinetic results can be described with a single conversion temperature‐phase diagram and interpreted with the classical autocatalytic epoxyprimary and secondary amine hydrogens addition. The differences between IPD and MNDA can be explained by the steric hindrance around the amine group of MNDA and also by the difficulty to obtain pure MNDA without oxidation.
Thermoinitiated cationic polymerization of epoxy resins by sulfonium salts
Authors: Morio Kazuhiko , Murase Hisashi , Tsuchiya Hiroshi , Endo Takeshi
Published: April 2003

Catalytic activities of benzyl sulfonium salts with nonnucleophilic anions (BF4−,PF6−,AsF6−,SbF6−) for epoxy polymerization were examined. The order of reactivities correlated well with nonnucleophilicity of anions. Epoxy resins catalyzed by these salts are characterized by longer shelf‐life and shorter gel time at high temperature. Some physical properties of cured product were compared with those cured by a commonly used BF3 amine complex.
Rheological study of the isothermal reticulation of an epoxy resin
Authors: Harran Daniel , Laudouard Annie
Published: April 2003

The complex modulus of shearing G* = G' + jG″ was measured during the isothermal hardening of several epoxy resins. The gelation induces a slowing down of the rate of growth of viscous modulus ν″ = d(log G″)/dt between two zones where this rate is constant. This slowing down of growth rate varies with the temperature and is null for T = TC gel: ν″2 −ν″1 = K(1/TC gel −1/T). We have shown that the two phenomena of gelation and vitrification stay perfectly distinct at all temperatures and in particular at TC gel. So the decrease of the rate ν″ associated with gelation disappears at this temperature without the vitrification being responsible.
Thermophysical analysis of thermal polymerization of silica‐organic cladding for silica fibers
Authors: Ionov V. N. , Kashin V. V. , Perminova V. N. , Rusanov S. Ya. , Sysoev V. K.
Published: April 2003

The paper shows the advantages of graded furnaces for the thermal polymerization of a silica‐organic polymer cladding for silica fibers. Owing to the optimal longitudinal distribution of the heaters a fivefold increase of the fiber drawing speed can be achieved using heaters of the same lengths and power.
Flame retardation of poly(ethylene terephthalate) containing poly(4‐bromo styrene), poly(vinyl bromide), and poly(vinylidene bromide)
Authors: Day M. , Suprunchuk T. , Cooney J. D. , Wiles D. M.
Published: April 2003

The pyrolysis and gaseous combustion of poly(ethylene terephthalate) (PET) incorporating poly(4‐bromostyrene), poly(vinyl bromide), and poly(vinylidene bromide) has been studied using thermogravimetry, flammability limit evaluation, and hydrogen bromide (HBr) evolution techniques. The data obtained have been compared with limiting oxygen index (LOI) flammability data to elucidate flame retardation mechanisms. All the organo bromides studied (applied either via topical treatment or radiation grafting) released HBr on pyrolysis which is capable of inhibiting the gas phase combustion reactions. Condensed phase interactions were also detected which were capable of altering the gaseous pyrolysates. Thermal stability considerations suggest that, although the aliphatic bromides are excellent sources of HBr, they are not ideal flame retardants for PET.
Polyester molding compounds: Partial systems and related particulate composites
Authors: Danusso F. , Tieghi G. , Lestingi A.
Published: April 2003

Several binary of ternary systems, consisting of an unsaturated polyester resin and one or two additives which are currently considered in formulating polyester molding compounds (such as BMC and SMC) were studied in relation to some of their relevant properties as a function of their composition. The additives were: MgO as a thickening agent; a thermoplastic polymer (PS or PVAc); and a fine CaCO3 particulate filler. Measured quantities were, depending on the system physical state (fluid or crosslinked): viscosity, linear shrinkage, flexural modulus and strength, and fracture toughness and energy, besides SEM morphological characterization. Quantitative relations could in several instances be expressed; in particular, the relation between strength and filler volume fraction was found to follow the linear equation of the simplest area reduction “random model”.
A kinetic and equilibrium model for nylon 6,6 polymerization
Authors: Steppan D. D. , Doherty M. F. , Malone M. F.
Published: April 2003

A simple, activity‐based solution model is used to develop thermodynamically proper correlation forms for the description of the rate and equilibrium behavior of nonideal polyamidations. The approach is especially useful in systems for which limited equilibrium and kinetic data are available. This model is applied to the nylon 6,6 system. the resulting correlation is valid for water concentrations from 1 to 90 mol% and for temperatures from 200 to 265°C. The equilibrium correlation is a function of the water mole fraction and temperature. At a fixed temperature, there is a maximum in the apparent equilibrium constant at a water concentration of approximately 10 mol%. There is an apparent inversion in the sign of the heat of amidation, as well as a continuous change in the apparent rate of polymerization from second to third order in carboxyl concentration at low water content.
Thermal stability of copolymer acrylamide–maleic anhydride
Authors: Vîlcu Rodica , Bujor Ingrid Ionescu , Olteanu Mihaela , Demetrescu Ioana
Published: April 2003

The thermal degradation of copolymer acrylamide–maleic anhydride prepared in various solvents (benzene, dioxane, methylethyl ketone) and different monomer ratios was investigated. The techniques of thermogravimetry (TG and DTG) and differential scanning calorimetry (DSC) were used. The IR spectra of degraded copolymers are discussed.
Effects of polymer‐filler adhesion on the properties of polychloroprene elastomers filled with surface‐treated fillers
Authors: Lee Michael C. H.
Published: April 2003

A new analytical method has been employed to determine values for the surface‐energy properties, such as the solid/vapor surface energy and the equilibrium work of adhesion, of several polychloroprene compositions filled with organosilane‐treated wollastonite fillers. The equilibrium work of adhesion, which represents the amount of energy stored in the interface formed between polymer and filler, has been used as a key material parameter to correlate changes in the mechanical and rheological properties of wollastonite‐filled polychloroprene compositions. Experimental results show that some properties such as tear strength, tensile modulus, shear viscosity, and compression set, which depend on polymer‐filler adhesion to varying degrees, increase as the equilibrium work of adhesion increases. On the other hand, properties such as tensile strength and ultimate elongation, which largely depend on the degree of mixing of filler particles and such defect structures as microvoids, decrease with the increase of the equilibrium work of adhesion. A power‐law relationship between the tensile modulus and the equilibrium work of adhesion has also been established. This relationship can be used for selecting organosilane‐treated fillers in order to achieve optimum properties.
A simple technique for measuring the refractive index of polymer latexes at various wavelengths
Authors: Devon Michael J. , Rudin Alfred
Published: April 2003

The refractive index of emulsions of polymers and copolymers may be estimated from absorbance readings with a UV‐visible spectrophotometer. Other information needed is the weight‐average particle diameter, from other techniques such as gradient disc centrifugation. A simple computer program matches the refractive index parameter so that calculated and experimental absorbances are equal at the given wavelength. The wavelength dependence of the polymer refractive index is readily obtained.
Influence of reagent residues and catalysts on formaldehyde release from DMDHEU‐treated cotton
Authors: Pasad Dilip M. , Beck Keith R. , Vail Sidney L.
Published: April 2003

Observations and conclusions drawn from a model N‐methylol reactant system have been used to study formaldehyde release from cotton fabric treated with N,N′‐dimethylol‐4,5‐dihydroxy‐ethyleneurea (DMDHEU). Reagent residues produced by DMDHEU in the presence of sodium bisulfate or zinc nitrate were found to be more complex than those formed from the N‐methylolpyrrolidone (NMP) reactant system, and the exact nature of some of the residues from DMDHEU could not be established. Zinc nitrate produces higher fixation of DMDHEU on cotton as compared to sodium bisulfate and also reduces formaldehyde release. As is the case with the NMP system, the lower amount of formaldehyde release with zinc nitrate catalyst is believed to be at least partially due to the formation of a complex between the N‐methylol reactant, DMDHEU, and zinc nitrate. The COCell bonds in both finishes resist acid‐catalyzed cleavage but cleavage of the NC bonds in N‐methylol groups (to release formadehyde) in the presence of acid is greater for the DMDHEU system than for the NMP system. Results with the DMDHEU and NMP systems are similar, but because of the complex nature of the products formed in the DMDHEU system it is very difficult to correlated formaldehyde release with specific chemical structures of residues or reactants.
The effect of sorbed penetrants on the aging of previously dilated glassy polymer powders. II. n‐propane sorption in polystyrene
Authors: Stewart M. E. , Hopfenberg H. B. , Koros W. J. , McCoy N. R.
Published: April 2003

Both the rate and apparent equilibrium of propane sorption in glassy polystyrene were increased after swelling the polymer by exposure to a highly sorbing vapor. Cyclic sorption experiments revealed that the increase in rate and apparent equilibrium of sorption due to the preswelling treatment decayed only during vacuum aging. The presence of low levels of propane in the polymer during aging, however, appeared to arrest the decay in sorption capacity. These composite results, taken in conjunction with the results of previous work in our laboratory, suggest that the component of the total sorption which resides in nonequilibrium, distended interchain gaps retards the chain motions which otherwise lead to consolidation of the dilated glass.
Thermal behavior, morphology, and the determination of the Flory–Huggins interaction parameter of polycarbonate–polystyrene blends
Authors: Kim Woo Nyon , Burns Charles M.
Published: April 2003

Blends of bisphenol‐A polycarbonate (PC) and polystyrene (PS) prepared by screw extrusion and solution casting have been investigated with weight fractions of PC in the blends varying from 0.95 to 0.05. From the measured glass transition temperatures (Tg) and specific heat increments (ΔCp) at the Tg, the polystyrene appears to dissolve more in the PC phase than does the PC in the PS phase. The blend appears to be near eqilibrium under extrusion conditions so that the polymer–polymer interaction parameter of PC/PS blends was calculated and found to be 0.038±0.004 for extruded blends at 250°C. Scanning electron microscopy supports the conclusion that the compatibility increases more in the region of PS‐rich compositions than in the regions of PC‐rich compositions of the PC/PS blends.
Gas permeation in miscible homopolymer–copolymer blends. I. Poly(methyl methacrylate) and styrene/acrylonitrile copolymers
Authors: Chiou J. S. , Paul D. R.
Published: April 2003

Gas transport properties in homogeneous blends of PMMA with each of two SAN random copolymers, containing 13.5 and 28% by weight of acrylonitrile respectively, have been measured at 35°C for He, H2, O2, N2, Ar, CH4, and CO2. For all cases, the permeability and diffusion coefficients are higher than that expected from the semilogarthmic additivity rule. On the other hand, the solubility coefficients and the ideal gas separation factors follow this rule well. These results for PMMA/SAN blends differ from those observed recently for other miscible blend systems; however, they agree well with recent theories proposed to describe gas sorption and permeation behavior in polymer mixtures. The composition dependence of gas transport properties observed in PMMA/SAN blends is attributed to the very weak net interactions between PMMA and SAN produced by repulsions between styrene and acrylonitrile units in the SAN random copolymers. Gas transport properties in phase‐separated PMMA/SAN blends have also been studied. The phase‐separated blends show sorption and permeation properties very similar to the corresponding homogeneous blends which can be explained by an isotropic, interconnected, two‐phase model proposed by Kraus and Rollmann. Gas permeabilities for the solution cast PMMA films used here are compared with melt‐extruded specimens used previously, and the differences are attributed to molecular orientation.
Strain birefringence of Kevlar aramid fibers
Authors: Yang H. H. , Chouinard M. P. , Lingg W. J.
Published: April 2003

We have measured the strain birefringence of Kevlar aramid fibers under static loading via a spectrophotometric method. At very low strain rates, the birefringence of Kevlar fibers increases markedly with increasing strain. On initial straining, the birefringence increases even at relatively constant modulus. This is attributed to the orientation of macroscopic species in the fiber which were observed by visible light microscopy. Such behavior is supported by the experimental observation of laser diffraction patterns and optical transmission images of Kevlar fibers under load. In the final stage of straining where the fiber modulus increases rapidly, the birefringence increase is attributable to crystalline orientation. The spectrophotometric method is useful for the simultaneous measurement of stress, strain, and birefringence of highly oriented, highly crystalline fibers such as Kevlar aramid. It is particularly useful to study the morphological inhomogeneity of a fiber which is undetectable by the conventional tensile test.
Influence of emulsifiers on film formation from cellulose acetate latexes experimental study of phase separation phenomena due to sodium dodecyl sulfate. I
Authors: Bindschaedler C. , Gurny R. , Doelker E.
Published: April 2003

Cellulose acetate membranes prepared from latexes containing sodium dodecyl sulfate as a stabilizer were found to undergo phase separation. This phenomenon was studied by different techniques including autoradiography, optical and scanning electron microscopy, mechanical testing, and liquid water permeation. The concentration of sodium dodecyl sulfate in the dry membranes was found essential in controlling their structure and properties, as well as the nature and amount of plasticizer incorporated in the latex system. The method of preparation and the drying duration were also relevant. Depending on whether films were produced by casting or spraying, tensile and permeation values exhibited quite different responses to variations of the sodium dodecyl sulfate content. In Paper II, a thermodynamic framework is proposed that accounts for the redistribution of sodium dodecyl sulfate into small islets, and thus for phase separation.
Crystallization behavior of polybutene‐1 in the anisotropic system blended with polypropylene
Authors: Takahashi T. , Nishio Y. , Mizuno H.
Published: April 2003

Development of supermolecular structure in drawn polypropylene (PP)/polybutene‐1 (PB‐1) blends was studied. PP (matrix)/PB‐1 (70/30) blend films were drawn and heat‐treated at fixed length or free ends at temperatures above the melting point of PB‐1. It was found that a long axis of the PB‐1 lamella is aligned perpendicular to the draw direction, and the c‐axis of the PB‐1 crystal is oriented perpendicular both to the draw direction and the plane of the surface of the blend film. Drawn, then heat‐treated PP/PB‐1 blend films gave a SAX pattern having a cross type scattering maximum on the meridian. It was confirmed that vertical scattering originates from the PB‐1 crystal developed during melt recrystallization. It was proposed that the structural development of PB‐1 in drawn PP/PB‐1 film can be explained on the basis of transcrystallization of PB‐1 in the confined 2‐dimensional space in the PP matrix. The kinetics of isothermal crystallization of PB‐1 was examined by use of a DSC technique. The result supports the conclusion that the heterogeneous nucleation of PB‐1 followed by 2‐dimensional crystal growth prevailed in oriented PP/PB‐1 blend film.
Influence of molecular weight distribution on the linear viscoelastic properties of polymer blends
Authors: Han Chang Dae
Published: April 2003

Literature data for the dynamic viscoelastic properties of binary blends of nearly monodisperse polybutadienes, polystyrenes, and poly(methyl methacrylate)s was analyzed using logarithmic plots of dynamic storage modulus G′ versus loss modulus G″, based on a recent theoretical study by Han and John.28 It has been found that for binary blends of monodisperse polymers with molecular weights M much greater than the entanglement molecular weight Me, the value of G′ in log G′ − log G″ plots becomes independent of molecular weight, increases sharply as small amounts of a high‐molecular‐weight component are added to a low‐molecular‐weight component, and passes through a maximum G′max at a critical blend composition (ϕ2)max, and that G′max becomes larger and (ϕ2)max becomes smaller as the ratio of component molecular weights increases. However, as the molecular weight distribution of the constituent components becomes broader, the effect of blend composition on G′ in log G′ − log G″ plots becomes less pronounced. This observation has enabled us to explain why log G′ − log G″ plots of binary blends of commercial polymers, namely, blends of two low‐density polyethylenes, blends of poly(ϵ‐caprolactone) and poly(styrene‐co‐acrylonitrile), and blends of poly(methyl methacrylate) and poly(vinylidene fluoride), all having broad molecular weight distributions, give rise to values of G′ between those of the constituent components. When one of the constituent components has molecular weight smaller than Me, while the other has molecular weight larger, and as small amounts of the high‐molecular‐weight component are added to the low‐molecular‐weight component, log G′ − log G″ plots of binary blends give rise to values of G′ larger than those of the constituent components at low values of G″, but approaches the value of G′ for the low‐molecular‐weight component as the value of G″ is increased. However as the amount of the high‐molecular‐weight component is increased above a certain critical composition, binary blends give rise to values of G′ close to that of the high‐molecular‐weight component at all values of G″. The experimentally observed dependence of G′ on blend composition in log G′ − log G″ plots is favorably compared to the theoretical prediction of a blending law proposed by Montfort and co‐workers.14,15
Polymer compatibility and interpolymer association in the poly(acrylic acid)–polyacrylamide–water ternary system
Authors: Eustace D. J. , Siano D. B. , Drake E. N.
Published: April 2003

Polyacrylamide and poly(acrylic acid) form a water‐insoluble phase when solutions of the two having concentrations that are not too low are mixed. The insoluble complex contains nearly stoichiometric 1 : 1 ratios of acrylamide and acrylic acid. The phase behavior of the ternary system was studied as a function of the degree of neutralization, α, of poly(acrylic acid). The complex is not formed when α is high. The formation of the complex was studied by measurement of pH increases observed when poly(acrylic acid) was titrated with polyacrylamide to infer a degree of linkage, θ, between the two polymers. A Hill plot of the data showed that the association was cooperative when the molecular weight was high.
Quantitative size exclusion chromatography of polypropylene I: Method development
Authors: Lew R. , Suwanda D. , Balke S. T.
Published: April 2003

Polypropylene was analyzed by size exclusion chromatography (SEC) at 145°C using a single‐differential refractometer detector. The objective was to provide data for characterization of polypropylene degradation during a reactive extrusion process. Two antioxidants [tetrakis(methylene(3,5‐di‐tert‐butyl‐4‐hydroxyhydrocinnamate)) methane (I) and octadecyl 3,5‐di‐tert‐butyl‐4‐hydroxyhydro cinnamate (II)] were tested for their ability to prevent thermal degradation of the polypropylene during sample preparation. The use of 0.20 wt% of (I) was effective during the 36–48 h required to completely dissolve the samples in trichlorobenzene for SEC analysis. “Reshaping” of the chromatograms by resolution correction demonstrated that, while the molecular weight averages were changed by 8% because of axial dispersion, most of the individual heights of the distributions were changed by less then 2%. Tail heights of the distributions were more affected but were also shown to be highly imprecise. Selecting individual heights of the distributions rather than molecular weight averages therefore minimized axial dispersion error and also circumvented errors in molecular weight averages originating from dilution of distribution tails below detector sensitivity limits. Various forms of distributions were examined and the equations linking the chain length distribution predicted by polymerization kinetic models to the SEC chromatogram are presented. The analytical method developed provided precise data for kinetic modeling. However, absolute accuracy requires further assessment.
New model for the high modulus and strength performance of ultradrawn polyethylenes
Authors: Zachariades Anagnostis E. , Kanamoto Tetsuo
Published: April 2003

A new morphological model is discussed which is based on the relation of tensile modulus and strength to the macrofibrillar dimensions (aspect ratio) and the shear modulus of ultrahigh molecular weight polyethylene fibrillar structures of draw ratio DR ≤ 200–300. Such structures were obtained by solid state deformation of the as‐received powder and solution grown crystals using an extrusion‐drawing process. According to this model, the highest tensile modulus and tensile strength values that can be obtained are 212 GPa and 13.3 GPa, i.e., significantly close to the theoretically calculated values.
Thermal and dynamic mechanical properties of polyurethaneureas
Authors: Hartmann Bruce , Duffy James V. , Lee Gilbert F. , Balizer Edward
Published: April 2003

Measurements were made of the thermal and dynamic mechanical properties of 22 polyurethaneureas of varying diol molecular weight, type of aromatic chain extender, diol molecular weight distribution, and chain extender stoichiometry. The dynamic mechanical data, obtained as a function of temperature and frequency (in the kHz region), were used to construct master curves of shear modulus and loss factor over a wide range of reduced frequencies. Based on these master curves, interpreted in conjunction with the thermal analysis results, it was found that: Soft segment crystallization occurs at the higher diol molecular weights, dynamic mechanical properties are well correlated with the soft segment glass transition, diol molecular weight influences dynamic mechanical properties by affecting the degree of phase separation and hence glass transition temperature, and neither diol molecular weight distribution nor chain extender stoichiometry have a significant effect, in the ranges studied, on transition temperatures or dynamic mechanical properties.
Charged ultrafiltration membrane for permeation of proteins
Authors: Miyama Hajime , Tanaka Kouichi , Nosaka Yoshio , Fujii Nobuyuki , Tanzawa Hiroshi , Nagaoka Shoji
Published: April 2003

Polyacrylonitrile‐g‐poly(N,N‐dimethylaminoethyl methacrylate) was synthesized photochemically and quaternized. The positively charged membranes made from the quaternized graftcopolymer showed high ultrafiltration rate for water by adding poly(vinyl alcohol) to casting solution and washing it out after the casting. In buffered saline solution, the permeability of the membranes was very small at pH below isoelectric point of albumin but increased markedly at higher pH. On the other hand, the permeability for γ‐globulin was very small and did not show any pH dependence.
Studies on the solvent exchange technique for making dry cellulose acetate membranes for the separation of gaseous mixtures
Authors: Lui A. , Talbot F. D. F. , Fouda A. , Matsuura T. , Sourirajan S.
Published: April 2003

The effect of the pore size on the surface of the water‐wet reverse osmosis membrane and the solvents used in the solvent exchange process on the pore size of the resulting dry cellulose acetate membrane was studied with respect to the separation of a CO2/CH4 mixture. It has been found that there is a critical pore size on the surface of wet membrane that results in the smallest pore size on the dry membrane and, consequently, in the highest separation factor. Such critical pore sizes become greater when the boiling point of the second solvent is increased.
Diffusion of organic penetrants through low density polyethylene (LDPE) films: Effect of size and shape of the penetrant molecules
Authors: Saleem M. , Asfour Abdul‐Fattah A. , De Kee D. , Harrison Brian
Published: April 2003

The diffusion coefficient at zero penetrant concentration D0 of dichloromethane, chloroform, carbon tetrachloride, cyclohexane, benzene, o‐xylene, m‐xylene, and p‐xylene, and n‐hexane in LDPE were measured at 25°C, using the desorption method. The D0 values obtained in this way are correlated with the size, shape, and chemical nature of the penetrant molecules. The temperature dependence of the diffusion coefficients of toluene and n‐hexane in LDPE are also reported in the limited temperature range of 25–45°C. It indicates that, in spite of a size larger than that of toluene, n‐hexane has a lower activation energy of diffusion.