bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyurethanes derived from caprolactone polyesters and diamines
Authors: Magnusson Alan B. 
Published: April 2003

AbstractThermoplastic, light‐stable polyurethanes have been prepared by the interfacial poly‐condensation of secondary diamines with the bischloroformates of polyester diols derived from ε‐caprolactones. A straight‐line relationship was obtained from a logarithmic plot of inherent viscosity versus Mn. The effect of some structural variations on the properties of the polyurethanes is discussed. These variations included the molecular weight of the polyester diol, the initiator used in preparing the polyester diol, the introduction of a methyl substitutent on the caprolactone ring, and the structure of the diamine. Polyurethanes prepared from polyester diols of Mn from 2000–4000 are opaque, stiff materials which undergo a melting transition at 40–50°C. characteristic of the polyester component. Polyurethanes which are flexible and translucent at room temperature are obtained either by using a low molecular weight polyester diol or a copolyester diol containing > 25% methyl ε‐caprolactone. The polyurethanes described are soluble in several common solvents and can be cold‐drawn to produce material of high tensile strength. Thermal studies using DTA and TGA Show an exothermic reaction starting above 300°C. Rapid weight loss beginning at 300–330°C. and leveling off near 500°C. accounted for 85–90% of the total sample and is attributed to decomposition of the polyester Chains.
Structural characterization of vulcanizates. Part V. Determination of degree of chemical crosslinking of natural rubber gum vulcanizate networks
Authors: Bristow G. M. , Porter M. 
Published: April 2003

AbstractA general treatment is given of the methods to be used in other parts of this series for calculating the degree of chemical crosslinking in natural rubber vulcanizates from stress–strain measurements in extension and from equilibrium volume swelling measurements. Corrections are required for the presence in the vulcanizate of appreciable quantities of particulate solids or soluble diluents and for the introduction of foreign atoms into the rubber network. For this purpose distinction is made between the rubber vulcanizate, the rubber matrix, the rubber network, and the rubber hydrocarbon component of the network. Expressions are derived, in terms of these concepts, for the Money‐Rivlin parameter, C1, measured on vulcanizates which have undergone various treatments.
Structural characterization of vulcanizates. Part VIII. The N‐cyclohexylbenzothiazole‐2‐sulfenamide‐accelerated sulfur vulcanization of natural rubber at 140–180°C. and of synthetic cis‐1,4‐polyisoprene at 140°C
Authors: Porter M. , Skinner T. D. , Wheelans M. A. 
Published: April 2003

AbstractVulcanization of natural rubber at 140°C. with a CBS‐accelerated sulfur system of conventional type gives rise to a structurally complex network in which the number of sulfur atoms combined per chemical crosslink present increases from 12 to 21 with increasing reaction time. The complexity of the network increases with increasing temperature of vulcanization. Crosslinking of a purified synthetic cis‐1,4‐polyisoprene proceeds more slowly and yields a slightly more complex network. Despite this overall similarity the natural rubber vulcanizates exhibit considerably higher tensile strengths.
Structural characterization of vulcanizates. Part IX. Comparison of the vulcanization of natural rubber and cis‐trans‐isomerized natural rubber with sulfenamide‐accelerated sulfur and dicumyl peroxide vulcanization systems
Authors: Elliott D. J. , Moore C. G. 
Published: April 2003

AbstractLarge variations in the microstructure of 1,4‐polyisoprenes, from ca. 100% cis‐trialkylethylene groups, as in natural rubber (NR), to ca. 40% cis‐ and 60% trans‐trialkylethylene groups, as in an equilibrium‐isomerized NR, have little influence on the overall chemistry of vulcanization of the polyisoprenes by a N‐cyclohexylbenzothiazole‐2‐sulfenamide‐accelerated sulfur system or by a dicumyl peroxide system. The peroxide crosslinks the equilibrium‐isomerized NR more efficiently than it crosslinks NR; this is attributed to the sulfur dioxide, which is used to isomerize the NR, scavenging some of the nonrubber constituents in the NR, which are known to compete with the rubber hydrocarbon for reaction with free radicals from the peroxide. By comparison with NR vulcanizates, the corresponding equilibrium‐isomerized NR vulcanizates have higher values of the C2 term of the Mooney‐Rivlin stress–strain equation and higher χ (polymer–swelling liquid interaction parameter) values of the Flory‐Huggins equation.
Preparation of organophosphorus polyurethane block copolymers
Authors: Łaszkiewicz Bogumił 
Published: April 2003

AbstractThe preparation of an organophosphorus polyurethane block copolymer of poly‐(ethylene oxide) (PEO) and poly(bis‐p‐carboglycoxyphenyl phenyl phosphine oxide) (PCGPPO) as well as the respective homopolyurethanes is described. The properties of the prepared polymers (melting point, intrinsic viscosity, solubility, and chemical composition) have been determined. Results of thermal and infrared analyses of these polymers are also reported.
Separation of water‐soluble polymer from emulsion by gel filtration
Authors: Muroi Soichi , Hosoi Keizo 
Published: April 2003

AbstractThe separation of poly(acrylic acid) from its mixtures with polystyrene emulsion by gel filtration, without destroying the state of dispersion, was undertaken. It was found that the poly(acrylic acid) not absorbed on the polymer surface is almost completely seperated by gel filtration, if the ionic strength, in this emulsion is not so high. Furthermore, the gel filtration study revealed that poly(acrylic acid) molecules are not adsorbed on the polymer surface saturated with surfactant molecules, whereas poly(acrylic acid) molecules, when already adsorbed on the polymer surface, are not easily desorbed by adding another surfactant.
Isothermal crystallization measurements on poly(ethylene terephthalate) by differential enthalpic analysis
Authors: Miller Bernard 
Published: April 2003

AbstractThe process of solid‐phase crystallization in poly(ethylene terephthalate) has been followed by means of differential enthalpic analysis. Kinetic data for the process has been obtained for isothermal annealing from 100 to 115°C., showing induction times and first‐order rate dependence. For the material studied, undrawn polyester filaments, an activation energy of 44 kcal./mole was determined. The technique used provides more direct monitoring of the crystallization phenomenon than that achieved with other methods.
Microstructure of some rubber‐reinforced polystyrenes
Authors: Keskkula Henno , Traylor P. A. 
Published: April 2003

AbstractAn electron‐microscope technique is presented to permit detailed examination of the fine structure of the rubber particles in reinforced polystyrenes. Several rubber‐modified polystyrenes, prepared by different methods, have been examined by this technique, and the resulting photomicrographs compared with those of the previously used phase contrast method. Polymers produced by the agitated‐solution process are examined in more detail. It is shown that the rubber particle fine structure is basically unaltered as the amount or type of rubber is changed or if the polymer is diluted by mechanically blending with polystyrene. It is characterized by the presence of numberous polystyrene occlusions within the particle.
Viscoelastic study of ionomers
Authors: Ward Thomas Carl , Tobolsky Arthur V. 
Published: April 2003

AbstractStress‐relaxation curves were obtained for ionomers containing different cations, per cents of ionization, and thermal treatments. Differences in the rheological behavior were found to depend more on the ionization level than on the ion. A recently proposed model for ionomers is discussed and found to be consistent with these results. In terms of this model the degree of ionization in the polymer acts as a regulator for the growth of small oriented lamellar (crystalline) regions. In the most general terms, the mechanical behavior and strength of ionomers appears dominated by the existence of “hard” regions interspersed among “soft” regions. In the polymers studied here there was some slight crystallinity; however, similar effects and explanations are probably suitable for amorphous “ionomers.” Toughness was also found in some completely amorphous carboxylcontaining copolymers without added ionic salts. The same explanation of “hard” regions interspersed among soft regions is also valid here. The “blocky” nature of the copolymerization may play a role in setting up this type of structure.
Prediction of mechanical properties of polymers. Tensile strength of several thermoplastics
Authors: McAbee Elise , Levi David W. 
Published: April 2003

AbstractTensile strength data for five thermoplastics [polycarbonate, phenoxy, poly(methyl methacrylate), polyethylene, and ethyl cellulose] are analyzed according to a modified rate equation. The agreement of the test results with the behavior described by the equation is excellent. Treatment of this type may be used to predict behavior of polymers from limited test data.
Reaction of α‐cellulose with SbCl3–KOH–AsCl3
Authors: Szymanski Herman A. , Yelin Robert 
Published: April 2003

Abstractα‐Cellulose dissolves in a mixture of SbCl3, KOH, and AsCl3. The resulting product as identified by PMR and infrared spectroscopy is α‐D‐glucose. This product is unexpected, and an explanation for its formation is suggested.
Modification of nylon 66 with diisocyanates and diacid chlorides. I. Chemical reaction
Authors: Perry Eli , Savory John 
Published: April 2003

AbstractFour α,ω‐diisocyanates (tetramethylene, hexamethylene, decamethylene, and eicosane) and six α,ω‐diacid chlorides (succinyl, adipyl, pimeloyl, sebacyl, dodecane, and docosane) were allowed to react with two types of nylon 66 yarn made from polymers of 14,800 and 21,000 number‐average molecular weights. The higher molecular weight yarn had a more ordered structure initially, as indicated by density measurements. Both diisocyanates and diacid chlorides crosslinked the yarn as shown by insolubility in 90% formic acid. Isocyanates were more efficient crosslinking reagents than diacid chlorides. Diacid chlorides caused simultaneous degradation of the yarn. The overall rate of reaction of the reagents with the yarn responded to temperature, reagent concentration, and time as expected for low molecular weight materials bearing the same functional groups. Catalysts had only a small effect on the rate of reaction. The reaction occurred in the less ordered regions of the yarn, as indicated by (1) a faster rate of reaction with the less ordered yarn, (2) the accelerating effect of swelling solvents on the rate, and (3) the reduction in extent of reaction with increase in molecular size of the reagent even though the reaction was not limited by diffusion. Both diisocyanates and diacid chlorides reduced the dyeability of yarn with acid dyes. Diacid chlorides increased the dyeability of yarn with basic dyes and diisocyanates decreased this dyeability.
Modification of nylon 66 with diisocyanates and diacid chlorides. II. Physical properties
Authors: Perry Eli , Savory John 
Published: April 2003

AbstractThe physical properties of nylon 66 yarn treated with α,ω‐diisocyanates (tetramethylene, hexamethylene, decamethylene, and eicosane) and diacid chlorides (succinyl, adipyl, pimeloyl, sebacyl, dodecane, and docosane) were compared to the properties of a control exposed to the same reaction conditions but without the reagent being present. Two types of yarn were used: (1) a highly ordered yarn, as judged by density and x‐ray, from polymer of number‐average molecular weight 21,000; and (2) a less‐ordered yarn from polymer of molecular weight 14,800. Treatment was carried out with yarn in both constant‐length and relaxed conditions. The properties were changed most by constant‐length treatment and by the use of less‐ordered yarn. Treatment with diisocyanates resulted in an increase in the tenacity and modulus simultaneously. The strength properties often went through a maximum as a function of the degree of reaction. Treatment with diacid chlorides degraded the physical properties as a result of polymer chain scission and weakening of the interchain forces. Treatment with either type of reagent lowered the zero strength temperature, but had little effect on the moisture regain or ability of the yarn to dissipate static electricity.
Over‐dyeing phenomenon and dichroism of dyed polymer
Authors: Kobayashi Yasuji , Okajima Saburo , Nakayama Kazuo 
Published: April 2003

AbstractVisible dichroism reflects the orientation of the amorphous region of a polymer. Thus the dichroism of a polymer must be constant irrespective of the amount of dye on the polymer. It is generally believed, however, that a fiber specimen must not be over‐dyed if the dichroism is to be measured quantitatively. The dichroism of cellulose and poly(vinyl alcohol) dyed with Congo Red was measured carefully, and the causes of this phenomenon were investigated. The “over‐dyeing” phenomenon is apparent. When the correct absorbance is measured, Lambert‐Beer's law holds good over the range of the possible dye content. The orientation of the dye molecules in polymer is independent of the dye content up to saturation.
Use of the farol‐weissenberg rheogoniometer to follow the early stages of cure of a polyester resin
Authors: Henson J. H. L. , Lovett A. J. , Learmonth G. S. 
Published: April 2003

AbstractThe Farol‐Weissenberg rheogoniometer has been used to investigate the early stages of cure of a polyester resin. By using the oscillatory facility of the rheogoniometer it is possible to follow the response of the resin system to torsional shear from the time of gelation into the early region of the gel state. Measurements of torsional forces made possible the determination of a modulus of elasticity (γM) at intervals of time during the cure and this parameter is shown to increase with increasing degree of crosslinking.
Dynamic‐mechanical study of the secondary transition of poly(vinyl chloride)
Authors: Pezzin G. , Ajroldi G. , Garbuglio C. 
Published: April 2003

AbstractThe influence of crystallinity, thermal history, plasticization, copolymerization, and chemical modifications on the dynamic‐mechanical properties of poly(vinyl chloride) has been studied by means of a free‐oscillation torsional pendulum. It was found that the secondary dispersion maximum is not affected by free volume, crystallinity, or head‐to‐head microstructure, but is modified by post‐chlorination, copolymerization, and plasticization. These results show that the molecular motions responsible for the PVC β peak are not influenced by local differences in the distribution of the Cl atoms along the chain, so that they seem to be largely of a cooperative type.
Crosslinking cotton with formaldehyde in phosphoric acid
Authors: Pierce A. G. , Frick J. G. 
Published: April 2003

AbstractCotton print cloth was treated with a solution of formaldehyde in concentrated orthophosphoric acid (a strong cellulose swelling agent). The treatment produces a crosslinked cotton with extremely high wet wrinkle recovery and moisture absorptivity, and very low dry wrinkle recovery. The variations in physical properties are explained in terms of crosslink distribution throughout the fiber and specifically by differences in interlamellar and intralamellar crosslinking. Data on the chemical and physical properties of the fabric as well as electron micrographs of fiber cross‐sections are presented and compared or contrasted with data from similar treatments employing other solvents such as water (a moderate swelling agent), acetic acid (a weak swelling agent), and sulfuric acid (a solvent which restricts crosslinking to the periphery of the fiber). Although the treatment causes extensive fiber swelling, it produces very little change in crystallinity and no change in crystal lattice type. Also discussed are the effects of combining this wet crosslinking and conventional dry‐cure crosslinking with methylol amides in a two‐stage process, in which the wet crosslinking is used either as a pretreatment or as an aftertreatment.
Stress relaxation of anhydrous gelatin rubbers
Authors: Yannas I. V. , Tobolsky A. V. 
Published: April 2003

AbstractAnhydrous gelatin–glycerol compositions exhibit rubbery behavior in the temperature region −40 to +40°C. and in the gelatin weight fraction range 0.1–0.4. These rubbers are capable of sustaining considerable stress over several decades of time at room temperature or below but flow rapidly in the region 45–60°C. Stress relaxation moduli at 25°C. appear to be insensitive to the substitution of glycerol with water but shear viscosity data indicate that gelatin–glycerol rubbers flow at temperatures about 15°C. higher than their aqueous counterparts.
Viscosity of concentrated styrene solutions of polystyrene
Authors: Hirose M. , O'Shima E. , Inoue H. 
Published: April 2003

AbstractViscosities of concentrated solutions of polystyrene of different intrinsic viscosities were measured at varying polymer concentration and temperature. By modifying Martin's equation, an empirical equation correlating the viscosity of the solution as a function of the polymer concentration, the intrinsic viscosity of the polymer, and temperature was obtained.
Preparation and stress–strain properties of ABA‐type block polymers of styrene and isoprene or butadiene
Authors: Cunningham Robert E. , Treiber Marion R. 
Published: April 2003

AbstractSeveral series of ABA‐type “tapered” block polymers of styrene (monomer A) with isoprene or butadiene were prepared with the use of n‐butyllithium or sec‐butyllithium as initiators in benzene solution. The stress‐strain curves of the raw polymers are reported, showing that many of them behave at ambient temperature like vulcanized elastomers. These polymers consist, however, of completely linear chains, with no chemical crosslinks between them; they are thermoplastic, can be easily molded, and are soluble in common solvents. Hence, they may be classed as pseudo‐crosslinked elastomers. Better stress‐strain properties are obtained from polymers made with sec‐butyllithium than with n‐butyllithium; in turn, polymers from butadiene have better properties than those from isoprene. Stress–strain curves most closely resembling those of crosslinked elastomers are obtained in general from polymers containing about 30–45% styrene. It was found that AB‐type block polymers have very poor tensile strengths and low elongations. The microstructures of polybutadienes and polyisoprenes of various molecular weights, prepared in benzene solvent with alkyllithium initiators, were also determined and compared with literature data for like polymers prepared in cyclohexane solvent.
Alkaline hydrolysis of aqueous polymer dispersions, particularly vinyl acetate copolymers
Authors: Davies R. F. B. , Reynolds G. E. J. 
Published: April 2003

AbstractThe influence of comonomer species and concentration on the ease of alkaline hydrolysis of vinyl acetate copolymers in the aqueous dispersion form is reported. The comonomers studied include higher vinyl esters, acrylic esters, a fumaric diester, and ethylene. The significance of the emulsion polymerization formulation has also been considered. The rate of hydrolysis is reduced with increasing proportions of comonomers and with increasing length and branching of the alkyl side chain originating from such comonomers. Branched long‐chain tertiary vinyl esters reduce not only the rate but also the extent of hydrolysis, being resistant to hydrolysis themselves and also protecting part of the more susceptible vinyl acetate; inhomogeneous copolymers, specially prepared, were less resistant than the more homogeneous copolymer of the same overall composition. The inclusion of quite small amounts, such as 1% by weight, of acid comonomers has a relatively large effect, increasing ease of hydrolysis. For comparison, the behavior of higher vinyl ester homopolymers and methyl methacrylate copolymers with acrylic esters is included. It is concluded that the major factors influencing ease of hydrolysis are steric and other environmental effects arising from the copolymer microstructure.
Transient behavior of viscoelastic fluid in an extruder
Authors: Chan R. K. S. , Lee C. W. M. , Biggs R. D. 
Published: April 2003

AbstractA simplified model is used for calculating the time‐dependent velocity of polymeric fluid in an extruder. The flow properties of the fluid are characterized by a simple constitutive equation based on two parameters: a constant viscosity μ and a constant elasticity modulus G. It was found that the transient velocity fluctuates periodically, and the time tt needed to restore the steady‐state velocity from a disturbance varies with the ratio G/μ and the dimensionless group ρH2G/μ2, where ρ is the density of the fluid and H is the screw depth of the extruder.
Determination of true flow curves from capillary rheometer data
Authors: Negami S. , Wargin R. V. 
Published: April 2003

AbstractThe evaluation of polymer melt viscosity versus shear rate has been customarily done by a time‐consuming graphical method, which corrects for non‐Newtonian behavior and pressure losses at flow transitions. It is shown by mathematical analysis that the flow data in terms of applied pressure and apparent shear rate can be treated by a semigraphical method, in which calculation of the true flow curve can be done with a computer. Moreover, it is possible in some cases to program the data treatment entirely for computer calculation. Results obtained by the proposed method are in excellent agreement with those obtained by the older graphical method.
Flammability of epoxy resins
Authors: Martin F. J. , Price K. R. 
Published: April 2003

AbstractFlammability determinations have been made for epoxy resin formulations. The oxygen index, defined as the volume fraction of oxygen in an oxygen/nitrogen atmosphere that is required just to sustain steady candlelike burning of a stick of the material, has been used as the measure of flammability. The formulations selected for study were those for which the chemical composition of the ingredients was known at least approximately and for which uniform cast slabs (1/8 in. thick) could be readily prepared. They covered a range of compositions of commercial interest. The results have been interpreted in terms of a proposed model for candlelike burning. Effects due to resin composition, cure conditions, fillers, and flame‐retardant additives are discussed.
Molecular heterogeneity characterization in polyglycols
Authors: Baijal M. D. , Blanchard L. P. 
Published: April 2003

AbstractThis paper deals with polydispersity coefficient characterization in poly(propylene glycols) (PPG 425, 750, 1025, 1200, and 2025) and poly(ethylene glycols) (PEG 200, 600, and 1000). The methods used involved ratio of 50% solution to intrinsic viscosity and ratio of weight‐average to number‐average molecular weight, as determined by gel permeation chromatography, light‐scattering photometry, and vapor pressure osmometry. The methods used assigned the same value to this coefficient. Polydispersity in polyglycols, which have low molecular weights (≤2200) and narrow distributions (≤1.1), may thus be determined from viscosity measurements.