bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Vulcanization 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

Large 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

The 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

The 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

The 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

An 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

Stress‐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

Tensile 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

α‐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

Four 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

The 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

Visible 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

The 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

The 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

Cotton 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

Anhydrous 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

Viscosities 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

Several 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

The 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

A 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

The 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

Flammability 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

This 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.
ESR spectra of copper complexes of cellulose
Authors: Baugh Peter J. , Hinojosa Oscar , Arthur Jett C. , Mares Trinidad
Published: April 2003

The ESR spectra of complexes of fibrous cotton cellulose and cupriammonia dihydroxide or cupriethylene diamine dihydroxide under various experimental conditions were determined. The spectra of both complexes with cotton cellulose were almost identical at −100 and 25°C. The spectrum of the complex of cupriethylene diamine dihydroxide with cellulose was stable to temperatures as high as 100°C. The sum of the linewidths of the hyperfine components of the spectra for each complex was about 180 gauss. Cotton fibers were combed and aligned with their axes (lengths) parallel to the magnetic field (B∥); after formation of either of the complexes with cellulose a minumum of hyperfine structure of components centered at H∥ was observed. A maximum of hyperfine structure of these components was observed when the complexed fibers were aligned with their axes perpendicular to the magnetic field (B⊥). The opposite was true of components centered at H⊥. For a complex of cupriethylene diamine dihydroxide and cellulose at 25°C. and at high pH the g∥ was 2.2127 and the g∥ was 2.0476. It was suggested that the alignment of most of the complex was its axis of symmetry at a maximum angle to the axes of the cotton fiber, when the axes of the fibers were in the parallel alignment with the magnetic field. At high pH these observations were even more marked. When ramie was used with cupriethylene diamine dihydroxide at high pH, the contribution of components centered at H∥ to the spectra was zero. Spectra for the copper compounds alone and complexed with cellobiose are also reported.
Flow properties of molten ethylene–vinyl acetate copolymer and melt fracture
Authors: Fujiki Tokio , Uemura Masaru , Kosaka Yujiro
Published: April 2003

In an investigation of the behavior and formation mechanism of melt fracture the flow properties of molten ethylene–vinyl acetate (EVA) copolymer in the region of high shear rate were measured with a capillary‐type rheometer. EVA copolymer differs slightly in flow curve from low‐density polyethylene (LDPE); it seems, however, that the difference is due to the difference in molecular weight distribution (MWD) rather than to the materials themselves. The fluidity of molten EVA copolymer having a narrow MWD is equivalent to that of LDPE having a broad MWD and, generally, EVA copolymer has a higher fluidity than LDPE. It is expected that the fluidity increases with incorporation of vinyl acetate at the same MWD and the same M̄w. The critical shear rate increases with melt index and temperature. It cannot be found that the materials themselves and the MWD directly influence the critical point of melt fracture formation when the melt index is taken as a parameter. The critical viscosity (ηc) at which melt fracture forms decreases in an almost straight line with an increase of melt index. It was found from the studies of end correction and behavior of melt fracture formation that melt fracture occurs at the inlet of the die, and it is supposed that the melt fracture formation is caused by the elastic turbulence in the flow pattern due to a failure of recoverable shear strain at the die inlet.
Abrasion, fatigue, and smearing of rubber
Authors: Schallamach A.
Published: April 2003

The abrasion of rubber on tracks without sharp‐pointed asperities is dominated by fatigue failure. This is demonstrated by the effect of certain antioxidants on the abrasion of natural rubber compounds in air, which largely disappears in nitrogen. The experimental results obtained in air can be obscured by smearing which seems to originate from the abrasion process itself. In addition, the relative humidity of the surrounding atmosphere has a great, and little‐understood influence on the rate of abrasion. The bearing of these findings on the interpretation of road test results is discussed.
Oxidative aging of natural rubber vulcanizates. Part III. Crosslink scission in monosulfidic networks
Authors: Colclough T. , Cunneen J. I. , Higgins G. M. C.
Published: April 2003

A natural rubber vulcanizate containing almost entirely monosulfidic crosslinks was oxidized in oxygen and with tert‐butyl hydroperoxide. The changes in physical properties due to oxidation were followed by stress–strain measurements, and the changes in chemical structure were investigated with chemical probes, and by spectroscopic methods. The results show that when the oxidized vulcanizates are heated at 75°C., the monosulfidic crosslinks are broken, that crosslinks containing two sulfur atoms are formed, and that conjugated diene and triene structures are introduced into the main polyisoprene chains.
Kinetics of continuous addition emulsion polymerization
Authors: Wessling Ritchie A.
Published: April 2003

An analysis of the kinetics of continuous addition emulsion polymerization is presented. For systems that follow the Smith‐Ewart mechanism, this analysis predicts that the reaction will approach a steady‐state condition if the rate of monomer addition Ra is constant. In the steady state, the rate of polymerization depends on Ra according to a reciprocal relationship, 1/Rp = (1/K) + (1/Ra), where K depends on the number of particles and the propagation rate constant. Above a critical value of Ra, the particles will become saturated with monomer and Rp will be constant and independent of Ra.
Radiation chemical studies of protein reactions: Radiation dose and viscosity change
Authors: Nisizawa Mizuho
Published: April 2003

When protein was irradiated by gamma rays from a cobalt 60 source, an activated state was caused. An empirical equation for the viscosity change was obtained, and the phenomena were explained on the basis of the molecular mechanism. The general equation for the viscosity change is given by ηred = (b + a log R)(1 − e−kt), where ηred is the reduced viscosity of the solution, R is the gamma radiation dose, and t is time.
Separation and characterization of the vinyl side chains from grafted polyacrylonitrile–cotton copolymers
Authors: Morris Nelle J. , Blouin Florine A. , Arthur Jett C.
Published: April 2003

A method of separation of polyvinyl side chains from grafted polyacrylonitrile–cotton copolymers was developed in order to study the effect of length of side chain on copolymer properties. The method consists of dispersion of the copolymer (1 g.) containing 20% polyacrylonitrile in 75% aq. ZnCl2 (100 ml.), addition of 6N HCl (100 ml.), heating for 1 hr. at 100°C., and precipitation and purification of the resulting vinyl polymer. The effect of hydrolysis on the intrinsic viscosity, the nitrogen content, and the infrared absorption spectra of the polyacrylonitrile polymers was investigated. It was concluded that this method of separation of the grafted polymers permitted a comparison of samples grafted by various techniques. A series of grafted copolymers was hydrolyzed, and the molecular weights of the isolated products were determined by measurements of intrinsic viscosity. Copolymer samples prepared by a post‐irradiation grafting technique had the longest polyacrylonitrile side chains (molecular weight, 1 × 106). Samples grafted by a simultaneous irradiation technique varied in side‐chain length, depending upon the monomer‐solvent system used in the preparation of the copolymer (molecular weight, 3 × 104−5 × 105). Chemically initiated grafting to cotton resulted in a copolymer containing relatively short side chains (molecular weight, 9 × 104).
Preparation and properties of films and fibers of disordered cellulose
Authors: Jeffries R.
Published: April 2003

The preparation and properties of films and fibers of highly disordered cellulose are described; the basis of the preparation is the regeneration of cellulose from cellulose derivatives in non‐aqueous media. These cellulose are at least 97% hydrogen‐bond disordered (as measured by the infrared‐deuteration technique), give x‐ray diagrams showing poor three‐dimensional order, and are practically completely accessible to swelling agents such as water and formic acid. The crystallization of these disordered celluloses is described. The effects on native cellulose of ball milling, mercerization, amine treatment, swelling in acid and salt solutions, and swelling in solutions of potassium hydroxide in non‐aqueous solvents are described with reference to changes in fine structure as measured by the infrared‐deuteration technique.
The alcoholysis of cellulose
Authors: Heath J. E. , Jeffries R.
Published: April 2003

The alcoholysis of cellulose in solutions of sulfuric acid in ethanol and n‐butanol is described; emphasis is placed on the reactions of a cellulose that is 97% disordered, as measured by an infrared‐deuteration technique, but the reactions of several partially ordered celluloses are also investigated. Alcoholysis produces only very slight increases in hydrogen‐bond order, and the rate of reaction is roughly related to the degree of hydrogen‐bond disorder in the starting material. The reactivity of the 97% disordered cellulose is dependent upon the method of freeing the film from the non‐aqueous media used in its preparation. This variable reactivity is not associated with differences in hydrogen‐bond order or in the surface area of internal voids, capillaries, etc., as measured by nitrogen sorption and a nonswelling oxidation technique, but could be due to the existence of a very fine pore structure in some of the films.
Transition‐metal complex formation with phenyl isocyanate
Authors: Rand Leon , McLean John A.
Published: April 2003

Complex formation between phenyl isocyanate and cobalt or manganese naphthenate in benzene was determined by the mole ratio method. Complex of 3:1 for cobalt and 2:1 for manganese were found. The method of analysis in this study utilized the characteristic transition‐metal visible absorption spectra. Effects of time and metal‐salt solution stability are noted.
Effect of orientation and trace crosslinking on the properties of high wet‐modulus rayon
Authors: Daul G. C. , Muller T. E.
Published: April 2003

Technology is now available to produce superior quality rayon fibers with a wide range of tenacity, elongation, and modulus. In‐process modification results in rayon fibers suitable for a great variety of end uses as continuous filament yarn or staple, either in 100% construction or blended with synthetics. In addition to versatility, such modified rayons have unique dimensional stability and chemical resistance. The developments leading to a method for preparation and the characteristics of such a highly oriented rayon, modified through trace crosslinking, are described here. The discovery of a triple modifier system utilizing poly(ethylene glycol)–dimethylamine in the viscose and small amounts of formaldehyde in a low zinc sulfate‐containing acid spin bath, has made possible the production of rayon fibers with high strength (ca. 6 g./den.) and adequate elongation (ca. 10%) for good processability and which are highly resistant to caustic soda. Among the variables studied were spin bath composition, especially the relationship between formaldehyde and zinc sulfate concentration, and bath temperature. Optimum modifier concentrations are defined with regard to particular fiber properties desired. The effects on orientation and fiber physical properties of spinning modified viscose into formaldehyde‐free and formaldehyde‐containing spinning systems are described. High orientation coupled with trace crosslinking provides greatly improved resistance to caustic soda over that resulting from orientation alone.
Sorption and diffusion of water in a rubbery polyurethane
Authors: Schneider N. S. , Dusablon L. V. , Spano L. A. , Hopfenberg H. B. , Votta F.
Published: April 2003

Unsteady‐state water sorption measurements have been carried out over the temperature range 27–40°C. on a polyurethane elastomer composed of MDI, 1,4‐butanediol, and polybutylene adipate (MW 2000) in the mole ratios 3.2:2:1. The sorption isotherm is concave upward above an activity of 0.6, reaching a saturation water concentration of 1.6 g./100 cc., the heat of mixing is zero, and the diffusion constant decreases slowly and linearly with increasing water concentration. The overall behavior is attributed to the immobilization of sorbed water in clusters. Analysis of the sorption process in terms of the cluster integral reveals that the interaction of water with specific polymer sites occurs at the lowest concentrations but that clustering dominates for water activities greater than 0.45. Since the activation energy for diffusion decreases with increasing water concentration, from 11,000 cal./mole at zero concentration to about half that value at saturation, plasticization of the polymer also affects the transport process.
Mechanism of reinforcement in rubber‐modified polystyrene systems studied by use of a miniature dart drop test
Authors: Schmitt J. A.
Published: April 2003

A miniature dart drop test was used in a study of the mechanism of reinforcement in impact resistant rubber‐modified polystyrene. A typical SBR‐polystyrene system was diluted with varying amounts of polystyrene, and thin compression moldings were made from each blend. The impact‐whitened areas were observed directly under the microscope and photomicrographs are presented. The whitening is caused by scattering of light from interfacial separation of portions of many rubber particles from polystyrene and by formation of a multitude of microcracks and/or crazes, starting at the partially separated particles. The absorption of energy by this mechanism can be very large. The driving force for the initial separation appears to be the triaxial tension under which the rubber particles exist, and this results from the higher volume shrinkage rate of rubber compared to that of polystyrene. Included also are photomicrographs taken of specimens after tensile stretching, and the mechanism derived from the impact case is extended to explain the increased elongation and corresponding whitening.
Effect of proccessing on flow properties of some linear polyethylene resins
Authors: Ford R. W. , Scott R. A. , Wilson R. J. B.
Published: April 2003

Changes in flow properties of polyethylene resins have often been observed during processing operations. Studies in this laboratory show that melt viscosity of polyethylene normally increases when the resin is heated in a compression mold at temperatures below 300°C. At the same time, the solution viscosity actually decreases in some cases. During extrusion, on the other hand, both melt viscosity and solution viscosity are shown to decrease. In addition, the logarithm of melt flow rate is seen to deviate markedly from the expected linear dependence on reciprocal of absolute temperature. The results suggest that both crosslinking and chain‐scission reactions occur during processing, the former predominating at low or zero shear, the latter at high shear.
Dependence of the thermal conductivity on mechanical stress in polymers
Authors: Fox J. S. , Imber M.
Published: April 2003

An examination of the theory of thermal conductivity of amorphous dielectrics as applied to polymeric materials indicates that it is reasonable to expect that the conductivity is stress dependent. An experimental investigation was undertaken to determine the validity of this hypothesis for a number of plastics at temperatures below their respective glass transition points. Poly(methyl methacrylate), nylon, and Delrin were chosen as representative of a wide range of percentage crystallinity and were tested at compressive stresses up to 140 kg./cm.2 and temperatures between 4 and 38°C. The results indicate that the conductivity may increase as much as 20% and that the dependence on stress is a function of temperature and the type of polymer examined.
Novel thermally stable and chemically resistant epoxy polymers derived from phenylene oxides
Authors: Neville Roy G. , Mahoney John W. , MacDowall Kenneth R.
Published: April 2003

Thermogravimetric and differential thermal analysis data are presented for three novel bisepoxy monomers and formulated coatings derived therefrom. The coatings were insensitive to impact in liquid oxygen and showed excellent resistance to liquid nitrogen tetroxide, concentrated nitric acid, and a variety of organic solvents. All coatings showed excellent adhesion to metals and oxidation resistance superior to any known commercial epoxy polymer. Thermal resistance was excellent at 500°F. for periods of at least 500 hr. in air. Other data on these novel epoxy polymers are also presented.
Sur la dégradation thermique du polychlorure de vinyle. V. Stabilité thermique de polyméres semicristallins
Authors: Guyot A. , Bertet M. , Tho Pham Quang
Published: April 2003

The thermal dehydrochlorination of semicrystalline, but rather low molecular weight, PVC fractions, prepared by ionic polymerization catalyzed by tert‐butylmagnesium chloride was studied under an inert atmosphere and compared with that of commercial polymer. When the samples are in powder form, the crystallinity of some fractions, which are insoluble at room temperature in all the usual solvents for PVC, induces a tremendous thermal stability, which is observed so long as the temperature is under the melting point of the sample. In dilute solution, the dehydrochlorination of all the samples is much slower, but the differences between the samples are less important; besides, a catalytic effect of some metallic impurities is observed. This catalytic effect is chiefly relative to a process of intermolecular condensation which causes the formation of a labile tertiary chlorine structure and so initiates or accelerates the purely thermal chain dehydrochlorination. It is suggested that, besides the crystallization and the catalytic effects, the configuration of the structural units could be an important factor in the course of the dehydrochlorination process.
Preparation of polysaccharide solutions for electron microscope investigations of supermolecular morphologic formations of the solid component
Authors: Rak J.
Published: April 2003

A new preparation process, which preserves the original morphological state of polysaccharides in solution during removal of the solvent and so makes possible direct electron microscope investigations, has been developed. The process consists of lyophylization of the sample (in very low concentration of water solution) by freeze‐drying, modified for the purpose of electron‐microscopic examination. Water‐soluble mixture of the polysaccharides of hemicelluloses isolated from the wood tissues of beech and the water solution of the mannan from Saccharomyces cerevisieae treated by means of the new preparation process (preparation with freeze‐drying) and, for comparison, these same samples treated without the application of freeze‐drying (by means of drying at laboratory temperature and atmospheric pressure, standard preparation process) are introduced as instance from many polysaccharides electron microscopic examined after this preparation process. This method allows one to make direct electron microscope investigations of the water‐soluble polysaccharides in no way stained or otherwise shadowed with good resolutions of details in the supermolecular range.
Relationships between surface wettability and glass temperatures of high polymers
Authors: Lee Lieng‐Huang
Published: April 2003

The adhesion between a polymer and a solid substrate may be considered to be one type of complex liquid‐solid interaction. Relationships between surface wettability and bulk properties of liquidlike polymers are discussed. A new and direct empirical relationship between the glass temperature (Tg) and critical surface tension of a polymer (γc) is established:

where n = degree of freedom, defined by Hayes, Vm = molar volume, and Φ = interaction parameter, or the ratio between reversible work of adhesion and geometrical mean of the work of cohesion. The effect of polarity and hydrogen bonding on this relationship is also discussed. The calculated γc's are much closer to the observed values than those calculated on the basis of parachor. With this new wettability relationship the wettability of polymers, especially of those forming no hydrogen bonds, can be related to thermal, rheological, mechanical, and relaxational properties.
The effect of strain rate on the stress–strain curve of oriented polymers. II. The influence of heat developed during extension
Authors: Hall I. H.
Published: April 2003

The temperature changes which take place in a yarn during extension are considered. From thermodynamical considerations and the heat‐transfer coefficient it is shown that extension of the yarns studied will take place isothermally at strain rates below 0.04 sec.−1 and adiabatically at rates above 4 sec.−1 It is not possible to make an accurate estimate of the magnitude of the temperature rise during adiabatic extension, because of the lack of information on internal energy changes during irreversible extension, but by assuming these to be zero it is estimated that the temperature is likely to rise by 20–30°C. at strains above 10%. Results from a study of the effect of strain rate on the stress‐strain curves of five different yarns show in all these materials a range of strain rate in which the stress that produces a given strain increases less rapidly with strain rate than elsewhere. For viscose and poly(ethylene terephthalate) this effect occurs in the expected range of strain rate, and its magnitude is of the correct order for it to be attributed to the temperature rise resulting from the transition from isothermal to adiabatic extension. For the other materials the transition does not seem likely to provide a complete explanation of this effect. There is no evidence that the transition significantly affects the breaking properties.
Melting points of cellulose nitrates
Authors: Colborne R. S.
Published: April 2003

Fresh determinations and estimations of the melting temperatures of cellulose nitrates have been found to be much lower than previously reported and to be in line with those of other cellulose derivatives, varying from 200°C. for the dinitrate to 280°C. for a sample approaching the trinitrate in composition. The heat of fusion of at least 3000 cal./unit is also similar to values of other cellulose derivatives. The paper contains some observations on the applicability of Flory's theory of the effect of diluents on the crystalline melting temperature of polymers.
Prediction of long‐term ABS relaxation behavior
Authors: Malpass V. E.
Published: April 2003

The applicability of time–temperature superposition to tensile stress relaxation of ABS plastics has been verified at strains from 0.5 to 5% for temperatures in the range of 10–50°C. Master curves have been compiled to predict the long‐term stress relaxation at 23°C. and a stress–strain–reduced time surface has been constructed. A comparison of relaxation times and activation energies has confirmed that a strain increase facilitates stress relaxation up to yield. The decay of relaxation modulus at linear viscoelastic strains was shown to be equivalent to that of tensile creep modulus. By normalizing the master curves to originate at yield stress and then converting them into multiaxial from the strain which gives the best data fit with long‐term hydrostatic pipe‐burst strength was shown to be at yield or beyond. The ABS yield‐strain master curves at 23°C. were shown to match satisfactorily the long‐term pipe‐rupture data. Activation energies for ABS relaxation have been compared below and above the rigid matrix Tg, to assess the degree of stiffening of the polymer in the solid state.
Thermodynamic interactions of branched polyethylene in polar and nonpolar systems
Authors: Cernia Enrico M. , Mancini Corrado , Saini Alberto
Published: April 2003

The thermodynamic properties of polymer solutions are frequently described in terms of the Flory‐Huggins equation. This equation includes a parameter χ, which depends upon the intermolecular forces acting between the molecules in a solution. The experimental determination of χ was performed by an improved microtechnique and extended to a wide range of polar and nonpolar diluents of polyethylene. Careful correlations are prescribed for calculating χ from pure‐component properties; they are based on an extension of the Hildebrand‐Scatchard theory of solutions and on the theory of intermolecular forces. Polar (τ) and nonpolar (δ) solubility parameters are presented for a variety of solvents. For polyethylene—nonpolar solvent systems we have emphasized the factor deciding the sign of heat of mixing, while for polyethylene‐polar solvent systems we have determined the contribution of dipole‐induced dipole interactions ψ (δτ) in interchange‐energy density B and, hence, χ.
Aromatic imide polymers for high‐temperature adhesives
Authors: Burgman H. A. , Freeman J. H. , Frost L. W. , Bower G. M. , Traynor E. J. , Ruffing C. R.
Published: April 2003

During the past decade the aerospace industry has sought materials for bonding stainless‐steel and titanium alloys that have a high degree of thermal and oxidative stability. The Air Force Materials Laboratory has anticipated these requirements and sponsored many development programs aimed at achieving these goals. This paper describes the results of one such program devoted to development of high‐temperature adhesives from aromatic imide polymers. The family of polymeric materials known as aromatic polyimides possess excellent thermal and oxidative resistance at temperatures up to 650°F. Mechanical and electrical properties of glass‐fiber‐reinforced laminates prepared with these polymers have been reported. This work has been extended to the development of structural adhesives that will withstand long‐time exposure in air at 600°F. Stainless steel and titanium have been successfully bonded with adhesives made from aromatic imide and benzimidazole imide polymers. Bonds made with stainless steel have retained approximately 80% of their original strength at 600°F. after 1000 hr. of aging at 600°F. Adhesives made with benzimidazole imide polymers are the prepared materials for bonding titanium. Initial bond strengths of 1300 psi have been measured at 600°F. After 1000 hr. at 600°F. the bond strengths drop to 800 psi. The processing conditions for making a bond are quite moderate, except that a high temperature is required. The preparation and processing conditions associated with these adhesives are described. A large number of aromatic imide and amide‐imide polymers have been prepared and adhesives formulated. By comparing the bond strengths obtained with these adhesives it is possible to deduce the effect of molecular weight and various molecular components on bond strength.
Thermal degradation of polymer mixtures. I. Degradation of polystyrene–poly(methyl methacrylate) mixtures and a comparison with the degradation of styrene–methyl methacrylate copolymers
Authors: Grassie N. , McNeill I. C. , Cooke I.
Published: April 2003

The degradation behavior of mixtures of polystyrene and poly(methyl methacrylate) in the form of thin films cast from a solution containing both polymers has been compared with that of the individual polymers and of copolymers of the same monomer pair by means of thermal volatilization analysis (TVA) together with product analysis by gas‐liquid chromatography determinations of the molecular weight of the solid polymer residues. The results indicate no interaction between the polymers when degraded together. The polymer mixtures are readily distinguished from copolymers of the same overall composition by TVA.