bluuebunny/crossref_metadata_2025 huggingface dataset:
Some observations on the shrinkage of jute
Authors: Roy S. C.
Published: April 2003

Measurements have been made of the shrinkage in alkali and of the permanent contraction resulting from alkali treatment. The results supported by x‐ray evidence following the changes in orientation and degree of mercerization show that the shrinkage of jute is subject to a similar restraint as swelling, and the shrinkage behavior of jute compared to ramie is as that of a yarn compared to that of its constituent fibers. Unlike swelling, the shrinkage of jute at dilute alkali is less than that of ramie and the corresponding region of the shrinkage curve is conspicuous by the smoothness of swelling curve, indicating that the shrinkage refers primarily to the structural framework of the fiber, whereas an extrastructural material may contribute to swelling. Although the crystallinity of jute is comparable to that of rayon, no appreciable permanent contraction occurs in the fiber treated in dilute alkali, and this points to a restraint in the structure of jute similar to that exercised by the crystallites in ramie. Whereas the resistance in ramie is completely neutralized in mercerizing alkali and the whole of the alkali shrinkage remains as permanent contraction, the restraint still operates in jute, and the permanent contraction is in deficit of the alkali shrinkage. The respective disorientations are also of the same order. Both permanent contraction and crystalline disorientation continually increase on repeated alkali treatments of jute and ramie; the additional effect found in jute is its complete mercerization after a number of treatments. The shrinkage as indexed by its maximum value is strongly correlated with the oriented state of the fiber, and the disorientation produced in jute on dilute alkali treatment is followed by a lower maximum shrinkage. Incomplete disorientation of mercerized jute shows up in positive shrinkage and its proportion is the same as that of unconverted cellulose I residue. In spite of a very high degree of orientation, the reoriented fiber shows a considerably low maximum shrinkage compared to the native. This is suggested to have been due to the formation of some junction points when the freely swollen plasticized fiber is mechanically strained.
Anisotropy of swelling of jute
Authors: Roy S. C.
Published: April 2003

The use of swelling anisotropy as a means of determining the orientation of cellulose fibers has been critically reviewed, and it has been shown that the method should be suitable for highly oriented fibers within a certain range of orientation. The application of the method to untreated and variously treated jute fibers reveals certain structural differences with ramie, of which the following are noteworthy. Both noncrystalline and crystalline orientations of jute are influenced by treatments which can be regarded as being confined to the intercrystalline regions only and which do not affect ramie. As compared with ramie, the ultimate maximum disorientation, produced on mercerization treatment is markedly less in jute, and this holds for both the crystalline as well as the noncrystalline components of the fiber.
Role of hydrogen ion concentration in retrogradation of starch sols
Authors: Kalb A. Joseph , Sterling Clarence
Published: April 2003

Cornstarch sols were prepared with pH adjusted to various values both before and after gelatinization. Retrogradation was ascertained by measurement of crystallinity (x‐ray), enzymatic digestibility, and cold water solubility. When the starch was gelatinized after pH adjustment, maximum retrogradation was at a pH value of about 5, with diminishing retrogradation at higher and lower values. When the starch was gelatinized before pH adjustment, maximal retrogradation occurred at pH values 1–2, with diminishing retrogradation at higher values. After an initial period of rapid retrogradation, retrogradation at all pH values studied follows first‐order kinetics. The data are explained in terms of molecular size, role of pH in hydrogen bond rupture, the weakly acidic character of starch, and changes in the configurational entropy of starch molecules.
Anionic polymerization of epichlorhydrin
Authors: Zilkha Albert , Weinstein Meir
Published: April 2003

The anionic polymerization of epichlorhydrin with potassium hydroxide was studied at 110–120°C. in bulk and in solution. Large molar equivalent ratios of catalyst were needed for polymerization and even when using 150 mole‐% catalyst, the conversion was only about 50%. The polymers obtained were crosslinked and had a low chlorine content. Crosslinking may be due to attack of a propagating chain end on the partially positive carbon attached to the chlorine atom in a polymer, or on a terminal epoxide formed by an intramolecular elimination of chlorine. The water of hydration in the catalyst influenced the polymerization in that it was released on consumption of catalyst causing termination of the polymerization, relatively low conversion, and low chlorine content of the polymers. The polymers had infrared absorptions for both carbonyl and carbon double bonds and gave dinitrophenyl hydrazones that indicate the presence of aldehydes or ketones. Preliminary experiments showed that the crosslinked polyepichlorhydrins obtained can be converted to exchange resins by utilizing either the hydroxyl or the chlorine functions of the polymer. Thus sulfonation and phosphorylation of the polyhydroxy polymer obtained by alkaline hydrolysis of residual chlorine in the polyepichlorhydrin gave inorganic esters that had free acid groups and served as reversible cation‐exchange resins. Amination of the polymers with sodamide gave an anion‐exchange resin, while replacement of the chlorine with cysteine gave a resin that can be used as a chelating agent for heavy metals.
An X‐ray crystallinity index method with application to poly(ethylene terephthalate)
Authors: Statton W. O.
Published: April 2003

Wakelin's method of correlation analysis of x‐ray diffraction patterns was adapted for fibers, films, and polymer samples of poly(ethylene terephthalate). This method gives a number called a crystallinity index, which is a measure of how far an unknown sample is between the extremes of the most amorphous and most crystalline samples obtainable for a polymer species. By being relative, this index eliminates the controversial assumptions of absolute crystallinity determinations. It is especially suited for routine studies since the calculations are readily adapted to the use of a computer and since the total time needed to obtain an index is short. A study of the indices of a variety of poly(ethylene terephthalate) materials produced the following conclusions:

(1) Maximum crystallization is achieved only by starting with an unoriented amorphous film. This is contrary to the view that orientation helps crystallization. Also, this shows that the act of spinning a fiber sets up an apparently strained state which will not crystallize to the same high level as a cast film. (2) Time of heating can be exchanged for temperature of heating, since the rate of crystallization is slow for this polymer. Thus, a longer time at a lower temperature is the equivalent of a shorter time at a higher temperature in producing equivalent crystallinities. (3) The crystallinity measured by density is not the same as the crystallinity measured by x‐rays. (4) A preordered state must exist in fibers in which segments of molecules have lost their complete randomness and are densely packed, yet the segments are not perfectly enough placed to produce x‐ray diffraction. Or, it can be concluded that spinning or drawing disrupts the fiber's perfect lattice so that less x‐ray diffraction is produced than the high density would indicate.
Acrylonitrile copolymerization with a NaClO3/Na2SO3 catalyst. Part I. Effect of 2‐methyl‐5‐vinylpyridine
Authors: Wishman M. , Detoro F. E. , Botty M. C. , Felton C. , Anderson R. E.
Published: April 2003

Batch copolymers, made by polymerizing acrylonitrile, vinyl acetate, and 2‐methyl‐5‐vinylpyridine (MVP) with a chlorate‐sulfite redox catalyst, are fractionated with respect to MVP content when they are fractionated with respect to molecular weight or polymer grain size. Polymer fractions of lowest molecular weight or smallest grain size contain the most MVP. A mechanism is proposed to explain these facts. To test the proposed mechanism, both ultraviolet and electron microscopes are used to study polymer formed during the early stages of batch polymerization. The effects of adding MVP, and of total monomer concentration, on the particles formed are determined. Interpretations of the microscopical observations are compared with the chemical interpretation. When MVP is present, the initial particles formed are more soluble, form colloidal particles less readily, and stabilize the colloidal particles, if formed, due to the charges on the polymer Initial particles with highest MVP content form polymer of lowest molecular weight and aggregate into the smallest polymer grains.
Investigation of the catalyst in the cellulose–DMEU reaction. Part II. Physicochemical studies of the reaction
Authors: Ziifle Hilda M. , Berni Ralph J. , Benerito Ruth R.
Published: April 2003

In a continuation of a previously reported investigation into the effect of the catalyst in the cotton cellulose–DMEU reaction, experiments were performed in which the four inorganic salt catalysts originally studied, MgCl2, Mg(NO3)2, ZnCl2, and Zn(NO3)2, were employed at the higher metal ion concentration of 0.1M, and CuCl2and CdCl2were employed at 0.03Mconcentration. Data from infrared absorption spectra of the treated cotton products were in agreement with those obtained at the 0.03Mcatalyst concentration, again indicating that the catalyst entered into the reaction, forming a coordination complex through the formation of nitrogen‐to‐metal bonds between the catalyst and the DMEU molecule. Similarly, it was again indicated that reaction with DMEU takes place preferentially at the primary alcohol group of the anhydroglucose unit. Analyses of IR data indicated a higher degree of crosslinking, and thus fewer terminal OH or NH groups at the 0.03Mcatalyst than at the 0.1Mcatalyst concentration. Further evidence of complex formation was obtained from infrared spectra of the product of the CdCl2–DMEU reaction carried out in the absence of cellulose. Supplemental physical data obtained on products of reactions catalyzed with CdCl2and CuCl2at the 0.03Mlevel, when compared with those obtained on products catalyzed with MgCl2and ZnCl2, supported the earlier hypothesis that chlorine damage during heating was dependent upon the ability of the metallic complex to act as a free‐radical trap. Additional support for the free‐radical mechanism was obtained when treated cloth subjected to chlorination and exposed to ultraviolet radiation suffered the same discoloring and degradative effect as cloth chlorinated and subsequently scorched according to the usual AATCC method. Reaction rates of the cellulose–DMEU reaction at 45, 55, and 65°C. with each of the four catalysts at the 0.03Mconcentration were determined by following changes both in nitrogen and formaldehyde content as well as in crease recovery properties. The reaction was found to be pseudo first order when followed to 2/3 completion, and the catalysts, when ranked according to greatest to least effect upon the reaction rates, followed the order: Zn(NO3)2> ZnCl2> MgCl2= Mg(NO3)2. Enthalpies, entropies, and free energies of activation have confirmed the earlier hypothesis that the metal ion enters into the reaction, forming a transition state complex.
The mechanism of ozone cracking. I. Ozone cracking of plastic films
Authors: Salomon G. , Van Bloois F.
Published: April 2003

Stretched films from partly unsaturated natural rubber hydrochloride develop cracks and fracture in ozonized oxygen. Cracking occurs only above a minimum stress level of about 70 kg./cm.2. Ozone sensitivity increases exponentially with stress, but goes through a maximum near the yield point of the thermoplastic films. Contrary to rubbers, these high‐modulus materials do not undergo overall stress relaxation prior to fracturing induced by ozone. The rate of surface ozonization of an unstretched film is estimated gravimetrically and volumetrically; it is found to be similar to that of rubber surfaces. Physical and chemical changes of the ozonized surface are reported. Results are briefly compared with ozone attack on other (nonrubber) materials.
The fine structure of fibers and crystalline polymers. II. The growth of crystalline regions in fibers
Authors: Hearle J. W. S.
Published: April 2003

The ideas of spherulitic crystallization as found in bulk polymers are applied to crystal growth in a moving medium such as an extruded fiber. It is shown that the structure will depend on the velocity of motion and the crystalline growth and nucleation rates. If growth proceeds from a single nucleus a sector of a giant spherulite will form, growing at a front where the crystalline growth rate equals the velocity of motion but, if nucleation is predominant, then a structure of small spherulites or micelles will form. The effects of orientation and drawing are considered. A detailed mechanism of crystal formation in an oriented structure by means of a screw dislocation is discussed.
Failure criteria for some polyurethane propellants
Authors: Milloway Warren T. , Wiegand James H.
Published: April 2003

Experimental and theoretical studies were made on failure criteria applicable to simple case‐bonded hollow cylindrical grains. The minimum strain at break at −75°F. for uniaxial tensile test was found to be at least twice the hoop strain at −75°F. of a thermally cycled, case‐bonded hollow cylinder of propellant when no failures were observed, whereas, when the minimum strain at break was equal to or less than the hoop strain of the cycled cylinder, the grain always cracked. For uniaxial tension, where the rate of elongation and temperature are controlled variables, the failure elongation varies from specimen to specimen and from batch to batch. A study of batch variability of the uniaxial test showed that a test at any test temperature from −40 to 180°F. could be used to characterize batch quality. The correlation of breaking strain at different rates and temperatures with the use of the WLF technique on one batch was found to be improved if an additional vertical shift factor was added to account for the lowering of the maximum failure elongation for temperatures below 0°F. However, by using a diagonal shift with rate, a graph of failure elongation versus temperature shows lower variability than does the WLF analysis.
Characterization of small gels in viscose
Authors: Sperling L. H.
Published: April 2003

The small gels present in cotton linters viscose, prehydrolyzed sulfate wood pulp viscose, and sulfite wood pulp viscose were examined by light scattering, electron microscopy, and chemical methods. In all cases a population of nearly monodisperse, spherical gels was found. The diameters are 0.3–0.6 μ by light scattering techniques, while the diameters of the dry gels by electron microscopy are near 0.1 μ. The difference is attributed to the swelling of the possibly crosslinked gels. The number of these inhomogeneities is very high, of the order of magnitude of 1011 gels/g. cellulose, yet they comprise less than 0.1% of the total mass involved. Chemically, the wood pulp viscose small gels appear to be about half cellulose II of a very low degree of substitution and about half of unknown composition. The cotton linters viscose gels contain xylan and some silica. These gels bear a striking resemblance to those studied in a previous acetate gel investigation, for both the cotton linters and the wood pulps. It is speculated that they may have a common origin.
Polymeric ligands. IV. Vinyltriacylmethanes
Authors: Degeiso R. C. , Donaruma L. G. , Tomic E. A.
Published: April 2003

Methacrylylacetylacetone and acrylylacetylacetone were prepared by acylation of acetylacetone enolate salts with methacrylyl chloride and acrylyl chloride, respectively. Both monomers yielded poor homopolymers. Methacrylylacetylacetone formed copolymers with styrene and methyl methacrylate without difficulty.
Polystyrene modifications. III. Copolymers and terpolymers of 2,5‐dichlorostyrene and 3,4‐dichlorostyrene
Authors: Dunham K. R. , Vandenberghe J. , Faber J. W. H. , Fowler W. F.
Published: April 2003

Thermal properties and resistance to crazing of copolymers and terpolymers of 2,5‐dichlorostyrene and 3,4‐dichlorostyrene have been studied. Copolymers based on 2,5‐dichlorostyrene showed little or no improvement over polystyrene in craze resistance or glass transition temperature. Although copolymers of 3,4‐dichlorostyrene were generally brittle and crazed readily, poly(3,4‐dichlorostyrene‐co‐2‐ethylhexyl methacrylate) and poly(3,4‐dichlorostyrene‐co‐n‐hexyl methacrylate) crazed less readily than polystyrene.
Investigation of the protective ultraviolet absorbers in a space environment. III. Protective effectiveness
Authors: Schmitt Richard G. , Hirt Robert C.
Published: April 2003

The effectiveness of the ultraviolet absorbers in protecting organic coatings exposed to an extraterrestrial environment from photochemical degradation was studied for the commercially available absorbers and certain errocene derivatives. The change in solar absorptivity of the coatings was used as a measure of the degradation incurred, these data being obtained from the ultraviolet, visible, and near‐infrared absorption spectra of the polymers. Ultraviolet absorbers of the benzophenone and benzotriazole type used for terrestrial applications were found to be considerably less effective in a space environment. This was attributed to the strong ultraviolet absorption of the polymers at the shorter wavelengths, which competes with the absorber for the incident radiation. Certain benzoyl‐substituted ferrocene compounds were found to be extremely effective in protecting many types of polymeric coatings. The benzoylferrocenes are highly colored materials (red to orange) whose absorbing properties are extremely stable to ultraviolet radiation.
The use of tensile measurements in following cellophane degradation
Authors: Meltzer T. H. , Weiss E. , Garvin C. M.
Published: April 2003

Comparisons were made of changes in molecular weight and in tensile strength of regenerated cellulose after exposure to 40% KOH at 90°C., for varying lengths of time. In the absence of air, both parameters decreased in a fairly consistent manner. In the presence of air, an initial steeper drop was followed by an irregular up‐and‐down pattern. The theory is advanced that the increase in tensile strength was caused by increased crystallinity.
Some relationships between water vapor permeability and chemical/physical structure in rigid urethane foams
Authors: Hilado C. J. , Harding R. H.
Published: April 2003

Low density rigid foams, reaction products of polyether polyols with tolylene diisocyanate, may transmit moisture vapor at rates from 0.3 to more than 8 perm‐inches at 23°C. Analysis of experimental data provided conservative design correlations showing that rate constants could be predicted only when a foam's polymer composition and physical structure were considered jointly. Among commercially acceptable rigid foam systems, cell structure and polymer aromaticity dominated the control of permeability levels. Permeabilities were lowest when transfer was directed perpendicular to the rise of highly orthotropic closed‐cell foams based on aromatic polyols of low equivalent weight. Permeabilities increased with effective cell diameter and also as foam density and closed‐cell content were reduced.
Dielectric loss features of some epoxy resins
Authors: Cohen Merrill , Kohn Leo S. , MacDonald David I.
Published: April 2003

At temperatures far below the heat distortion point, the dissipation factor (and therefore power factor) of epoxy resins is comparably low—in the order of 0.001–0.01. Internally flexibilized, polyester‐modified resins may have higher loss tangents, in the order of 0.01–0.10, even at room temperature. At temperatures far above the heat distortion point, anhydride curing agents give lower dissipation factors than do amines or acids. With anhydride cures, the higher molecular weight resins investigated cure faster than the lower molecular weight resins, give lower elevated temperature power factors and loss tangents, and are tougher. With any hardener–epoxy resin system, the optimum elevated temperature power factor, weight loss on aging and heat distortion point will probably depend on a close examination of the optimum hardener/resin ratio.

With certain anhydride‐cured low molecular weight epoxy resin systems, an increased rate of cure and lower elevated temperature power factor may be obtained by use of a small amount of higher molecular weight (polyhydroxy) epoxy resin. Attempts to compare the effect on power factor of changing the hydroxyl groups to less mobile dipoles by acetylation were unsuccessful, since the resulting acetoxy groups changed the cure mechanisms. However studies with resins of different molecular weights indicated that the effect of hydroxyl content on elevated temperature power factor is subordinate to other effects such as the rigidity of the cured resin system, rate of cure and ionic impurities. Acetylation of hydroxyl‐containing epoxy resins may inhibit cure with some curing agents, due to side reactions of the resulting acetoxy group with specific hardeners.
Nucleophilic displacements upon poly(vinylbenzyl chloride)
Authors: Lloyd W. G. , Durocher T. E.
Published: April 2003

High molecular weight poly(vinylbenzyl chloride) fails to undergo many classical organic reactions, but may be reacted essentially quantitatively with a variety of tert‐amines to yield the corresponding quaternary polymers. With dimethyl‐n‐alkylamines, polymers of the type are formed; these are water‐soluble through R = n‐decyl and methanol‐soluble through R = n‐hexadecyl. A number of polyridines and dialkyl sulfides react similarly to yield the corresponding polycationics. These reactions are controlled by several factors not operative in small‐molecule reactions: nucleophile partitioning in the initially heterogeneous systems, swelling power of the medium for the reactant polymer, and a sharp steric limitation imposed by the configuration of the high polymer. This steric effect may be exploited by using certain hindered primary and secondary amines to prepare substituted poly‐(vinylbenzylamines) which are soluble and noncrosslinked.
Sorption of liquids by wool. Part IV. Sorption of ethanol by modified wool
Authors: Leeder J. D. , Lipson M.
Published: April 2003

Experimental results for the sorption of liquid ethanol by a variety of modified wools are described. Even slight changes in the chemical and physical structure of wool produced large changes in ethanol sorption rate. Blocking of amino groups decreased the sorption rate due to removal of primary sorption sites, but, surprisingly, carboxyl group modification greatly increased the rate. Modification of disulfide crosslinks increased the rate, while in most cases surface modification decreased it, which is contrary to expectation if a surface barrier to diffusion of penetrants is assumed. Theories are advanced for the observed changes in sorption properties and for the small changes found when water if used as sorbate. Saturation sorption values showed only slight changes from that for untreated wool. The largest increases resulted from disulfide bond modification, which is explained as due to lower resistance of the treated wool to swelling forces, allowing greater swelling and sorption.
A study on the thermal degradation of rubber in dilute solutions
Authors: Sarfare P. S. , Bhatnagar H. L. , Biswas A. B.
Published: April 2003

The kinetics of low‐temperature (60–100°C.) thermal degradation of deproteinized and deresinified petroleum ether soluble fraction of natural rubber in two chemically inert solvents, cyclohexane and trans‐decalin, have been studied. The changes in Mw, A2, and (r2)1/2 at various stages of degradation have been obtained from the lightscattering data. The rate constants and the energy of activation for chain scission have been calculated from the observed variation in Mu. The scission has been found to be random and the average energy of activation is 25.8 kcal./mole. This low‐energy requirement suggests the presence of weak links in the rubber molecule which get ruptured at low temperature.
A medium‐speed tensile testing machine and some dynamic data produced thereby
Authors: Anderson A. G. H.
Published: April 2003

A pneumatic tensile tester, recently designed and built at Watertown Arsenal Laboratories, has a load capacity of 15,000 lb. and an idling speed of about 300 in./sec. over a 3‐in. stroke, at 500 psi nitrogen or one‐third the allowable maximum pressure. Loads and strains may be recorded by oscillographs or oscilloscopes. The scope can be triggered through an electric circuit by an internal, automatic poppet valve in the main gasport. External, auxiliary diaphragm valves are actuated by solenoids. Excess energy of piston assembly, after a tensile rupture, is absorbed through rapidly damped oscillations between two air cushions at opposite ends of the cylinder. The machine is mounted on a carriage resting on springs and Barrymounts so that operation at full load transmits negligible vibrations to the floor. Weight of machine and carriage is 700 lb.; base, 600 lb.; and steel safety cabinet, 400 lb. Short descriptions and a number of illustrations are presented which show typical actions of the machine and results of various tests recently performed on structural materials.
Adaptation of a ballistic tool for obtaining strain rates above 20,000 inch/inch/minute
Authors: D'Amato D. A.
Published: April 2003

A low cost, dynamic tensile tester was designed and developed, using a simple ballistic piston tool as the driving force. The principal purpose of the device was to provide performance data on the response of high molecular weight, linear polyethylene subjected to strain rates between 20,000 and 50,000 in./in./min. at temperatures ranging from 75 to −40°F. Tests were made on samples of linear polyethylene, conventionally formed, and of linear polyethylene, formed by a special process, to produce a highly oriented, highly crystalline structure. Both materials were tested in the direction of forming and at right angles. Basically, the unit consists of a ballistic tool that fires a captive piston against a block to which a specimen is attached. A load cell, in series with the sample, records the developed force and a simple cantilever beam strain gauge is used to record the cross head travel. The rate of strain is controlled by the propellant charge (piston velocity) and a buffer device. The unit is relatively light and protable. For cold temperature firing, the whole unit is placed in a cold box and both the samples and the device are soaked to the desired temperature. Firing takes place in the cold box to insure uniformity of sample temperature.
The tensile properties of textile yarns at very high strain rates
Authors: Hall I. H.
Published: April 2003

Stress‐strain curves have been determined at a very high rate (330 sec. −1) and at a normal rate (8.3 × 10−3 sec.−1) of straining for a range of lightly twisted yarns covering all commercially important fiber‐forming polymers. From these curves breaking stress and extension, energy to rupture, initial modulus, and critical velocity have been obtained. Results are presented in detail to assist selection of fibers for applications where rapid extension is likely. At the high rate the breaking stress is always greater and, with one exception, the breaking extension less than at normal rates. The energy to rupture increases with rate for the wet‐spun fibers and, with one exception, decreases for the thermoplastic. The variation in magnitude of these changes is considerable even among fibers from the same polymeric base, emphasizing the importance of testing at a rate comparable to that encountered in use. Similar experiments performed with three of the yarns highly twisted showed that the ranking of the yarns according to a particular property could be altered by the insertion of twist. The stress‐strain curves of the material were used to predict the curves for the twisted yarn, following a theory of Treloar and Riding. At the normal rate agreement with experiment was fairly good, but it was much worse at the high rate.
Crosslinking reactions of acrylic polymers containing carboxyl groups with melamine resins
Authors: Saxon Robert , Daniel John H.
Published: April 2003

The mechanism of cure has been studied in coating systems comprising blends of ammonium salts of acrylic acid–acrylic ester copolymers and alkoxymethylmelamines. Experiments were conducted both on the resin components themselves and on model compounds having analogous chemical structures. Curing of the resin begins with loss of ammonia to regenerate free carboxyl groups, rather than loss of water to form amides. The alkoxy group is eliminated, and ester crosslinks are formed between the carboxyl and the methylolmelamine. Base binding studies on cured films show that the extent of crosslinking depends on the exact composition of the resin system and the presence or absence of an acidic catalyst. These variables can be adjusted to provide essentially quantitative crosslinking in the cured coating, as shown by the complete disappearance of unreacted carboxyl groups.
New catalysts for the polymerization of diisopropenylbenzenes
Authors: D'Onofrio A. A.
Published: April 2003

Linear, high molecular weight, soluble, catalyst‐free polyindanes have been prepared by the polymerization of p‐diisopropenylbenzene with a series of insoluble complex catalysts. A new synthesis of p‐diisopropenylbenzene is reported.
Monomer reactivity ratios of N‐octadecylacrylamide and N‐allylstearamide
Authors: Jordan Edmund F. , Wrigley A. N.
Published: April 2003

The monomer reactivity ratios and the corresponding copolymerization parameters for the copolymerization of N‐octadecylacrylamide (M1) and several monomers in tert‐butyl alcohol at 60 ± 0.1°C. were determined and were: with acrylonitrile, r1 = 1.44 ± 0.019, r2 = 1.10 ± 0.035; Q1 = 0.60, e1 = 1.20; with vinylidene chloride, r1 = 1.37 ± 0.008, r2 = 0.438 ± 0.008; Q1 = 0.65, e1 = 1.08; with vinyl acetate, r1 = 6.11 ± 0.045, r2 = 0.027 ± 0.009; Q1 = 0.72, e1 = 1.12. The mean copolymerization parameters, therefore, were Q1 = 0.66, e1 = 1.13. The reactivity ratios and the corresponding copolymerization parameters for the copolymerization of N‐ally lstearamide (M1) and several monomers, polymerized in tert‐butyl alcohol at 80 ± 0.1°C. (except for vinyl acetate, polymerized in bulk at 70 ± 0.1°C.) were determined and were: with acrylonitrile, r1 = 0.118 ± 0.084, r2 = 3.61 ± 0.087; Q1 = 0.058; e1 = 0.21; with vinylidene chloride, r1 = 0 ± 0.136, r2 = 5.23 ± 0.067; Q1 = 0.028, e1 = −0.80; with vinyl acetate, r1 = 0.0532 ± 0.012, r2 = 0.740 ± 0.087; Q1 = 0.043, e1 = −1.18. The mean copolymerization parameters for N‐allylstearamide were, therefore, Q1 = 0.043, e1 = −0.59.
Zone fractionation of cyclohexane‐rich polystyrene–cyclohexane solid solutions
Authors: Ruskin A. M. , Parravano G.
Published: April 2003

Experimental results on the application of zone melting techniques to dilute solutions of polystyrene in cyclohexane under various operating conditions are reported together with observations on static solidification tests on the solutions. The variables investigated were: polymer concentration, number of zones passed, zone length, and zone travel rate. The results showed that at slow zone travel rates (ca. 4.01 cm./hr.) redistribution of solute species occurs in conformity with thermodynamic predictions. In this case, a cyclohexane‐rich liquid and a polymer‐rich liquid, which coexist at temperatures just above the solidification range, react to form a cyclohexane‐rich solid solution upon solidification. The solid solution contained a higher concentration of all polymer species than the cyclohexane‐rich liquid, with the ratio of the concentration in the solid to the concentration in the liquid increasing exponentially with molecular weight of the solute. The net result was the accumulation of all solute species toward the head (i.e., first melted and first frozen) end of the zone melted ingot, with the higher molecular weight species enjoying the greatest redistribution in this respect. At moderately faster speeds of zone travel (ca. 4.83 cm./hr.), a reversal in the accumulation trend with molecular weight was found; the higher molecular weight species were carried increasingly to the tail (i.e., the last frozen) end of the sample. Increases in total polymer concentration enhanced this effect. These facts have been interpreted as suggesting that resorption of some of the higher molecular weight species from the polymer‐rich phase was not sufficiently fast compared to the rate of freezing, and part of the polymer‐rich phase was carried in the moving liquid zone. At significantly faster speeds of zone travel (ca. 9.66 cm./hr.) a decreased redistribution of solute species was found. Increased total polymer concentration reduced the selectivity of fractionation. This effect was interpreted as being the result of the lesser extent to which the resorption reaction in these experiments occurred in relation to the rate of movement of the interphase. Qualitative considerations on the thermodynamic characteristics of the polymer–solvent system most suitable for effective zone fractionation are discussed. The effect of zone fractionation upon the distribution of molecular weight for some of the samples is reported.
Cut growth and fatigue of rubbers. II. Experiments on a noncrystallizing rubber
Authors: Lake G. J. , Lindley P. B.
Published: April 2003

Tensile fatigue failure of a gum vulcanizate of noncrystallizing SBR can be accounted for by the growth of small flaws initially present in the rubber. Fatigue of crystallizing natural rubber was shown in Part I to be attributable to the same cause. Cut growth results are interpreted in terms of the tearing energy theory of Rivlin and Thomas. SBR exhibits cut growth under both static and dynamic conditions; in each case the rate is approximately proportional to the fourth power of the tearing energy. Variation of the dynamic cut growth rate with frequency can be explained by the summation of a timedependent static component of growth and a cyclic component not dissimilar to that occurring in natural rubber. Fatigue failure, under both static and dynamic conditions, is predicted from the cut growth results. These predictions are found to account quantitatively for experimentally observed fatigue lives when a suitable value is assumed for the initial flaw size. Fatigue lives at different temperatures correlate well with cut growth results obtained by Greensmith and Thomas over the same temperature range. The results are compared to those obtained previously for natural rubber, and possible reasons for the differences in fatigue behavior of crystallizing and noncrystallizing rubbers are discussed.
Eddy current drive and gas bearing bob suspension for use in viscometry
Authors: Myers W. Thomas
Published: April 2003

A sensitive concentric cylinder viscometer was developed capable of measuring viscosities of liquids with a precision of 0.2% and an accuracy of 1%. The essential features of this apparatus were a nearly frictionless gas bearing suspension for the viscometer bob and and eddy current torque‐sensing device. The viscometer was tested by measuring viscosities of liquids in the centipoise range and determining the elastic behavior of fiber networks suspended in solutions; a torque range of 1–250 dyne‐cm. was studied. Based on the results of this work, the apparatus would appear to be an ideal instrument for the study of polymer solutions and particle suspensions exhibiting unusual flow behavior at low shear stresses.
A simple stress relaxometer and its use with vulcanized nitrile rubber/PVC compounds
Authors: Outhwaite R. I. , Singleton G. , Ross J. A.
Published: April 2003

An easily constructed, cheap and compact stress relaxometer has been designed for aging tests on elastomers. Its construction is such as to allow it to fit inside a multicavity metal block oven commonly used for aging tests. The instrument works well on continuous and intermittent cycles and its action is illustrated by a brief examination of the stress relaxation properties of vulcanized nitrile rubber/PVC blends. The presence of PVC increases the initial (physical) relaxation both at high and normal temperatures under conditions of continuous stress. The rate of relaxation thereafter increase with increase in PVC content. Under intermittent conditions the PVC seems to encourage a crosslinking reaction, as does carbon black.
Linear polymers of 4,4′‐(2,2‐butylidene)dibenzoic acid
Authors: Schiller Arthur M. , Petropoulos John C. , Chen Catherine S. Hsia
Published: April 2003

Polyesters and polyamides have been prepared and characterized from 4,4′‐(2,2‐butylidene)dibenzoic acid. The polymers are amorphous with the exception of the piperazine polyamide. This novel diacid yields hard, tough polymers. The properties of the ethylene glycol and bisphenol A polyesters have been thoroughly investigated and are reported.
High resolution electron microscopy of sodium lignin sulfonate
Authors: Rezanowich A. , Yean W. Q. , Goring D. A. I.
Published: April 2003

High resolution electron microscopy of sodium lignin sulfonates revealed a granular microstructure of spherical particles of diameters ranging from 30 to 90 A. The weight average particle weight, Pw was computed from the dimensions measured on the electron micrographs and the density of lignin. For a fraction of intermediate molecular weight, the particle diameter derived from Pw was 64 A., in fair agreement with a value of 49 A. computed from the sedimentation equilibrium molecular weight. A high molecular weight fraction contained, in addition to the granular moiety, larger structures which appeared to be aggregates of the granules. The particle weight distribution for the high molecular weight fraction was similar to the distribution of sedimentation constants previously found for alkali lignins. The spherical shapes for both the granules and the aggregates was in accord with the compact spherical configuration previously proposed for lignin sulfonates in aqueous solution.
Determination of hydroxyl number of polyoxyalkylene ethers by reaction with toluene diisocyanate
Authors: Otey F. H. , Zagoren Bonnie L. , Mehltretter C. L.
Published: April 2003

A new method for hydroxyl analysis is described in which excess toluene diisocyanate is reacted with a hydroxy compound, preferably in the presence of a catalyst, and the unreacted isocyanate is determined with dibutylamine reagent. The method is particularly applicable to polyethers intended for urethane foam preparation. It is rapid, is accurate, and has the added advantage of including such impurities as would be expected to consume isocyanate during a foam preparation.
Some relationships among strength, temperature, and chemical/physical structures in rigid urethane foams
Authors: Harding R. H. , Hilado C. J.
Published: April 2003

Low density rigid foams, produced by reacting polyether polyols with tolylene diisocyanate in the presence of fluorotrichloromethane, offer mechanical properties at levels which can have commercial utility. Compressive strength was selected as a representative subject for empirical analysis at temperatures from 25 to 120°C. The resultant correlation indicates that mechanical performance can be optimized only when foam formulation, manufacturing technology, and conditions of service are considered jointly. At moderate temperatures, strength is controlled most conveniently through the foam's effective physical structure. The relative importance of polymer chemistry tends to rise with temperature. Strengths are generally highest in foams based on highly functional aromatic polyols of low equivalent weight.
Heat and entropy of fusion of polypropylene
Authors: Kirshenbaum I. , Wilchinsky Z. W. , Groten B.
Published: April 2003

There are wide discrepancies in the literature values for the heat of fusion (ΔHu) of isotactic polypropylene. A study was therefore made of the variables affecting ΔHu as determined by differential thermal analysis. The results of this study show ΔHu for 100% “crystalline” polypropylene to be 2400 cal./mole repeating unit with 2σ = 300. The entropy of fusion is 5.4 e.u./repeating unit (2σ = 0.3). Thermal history, potential errors in sample–sensor contact as well as uncertainties in x‐ray analysis for per cent crystallinity are discussed.
Extracellular polysaccharide produced from glucose by cryptococcus laurentii var. flavescens NRRL Y‐1401: Chemical and physical characterization
Authors: Jeanes Allene , Pittsley J. E. , Watson P. R.
Published: April 2003

The polysaccharide that occurs freely dispersed in culture fluids in which the nonpathogen, Cryptococcus laurentii var. flavescens NRRL Y‐1401, has been grown on the carbohydrate substrate, glucose, has been isolated, purified, and characterized. This macromolecular polysaccharide is composed of D‐mannose, D‐xylose, and D‐glucuronic acid (as the potassium salt) and a small proportion of O‐acetyl groups. Factors favorable to practical application of this hydrocolloid are its adaptability to large‐scale production, its stability in storage, and the properties of its homogeneous dispersions. Dispersions in water or aqueous alcohol are highly viscous and tend to soft gelation. Dispersions in water show plastic rheological characteristics and thixotropy with rapid regain of viscosity after shear. Moderate decreases in viscosity result from the presence of electrolytes or from heating, and only small differences in viscosity occur in the pH range 4–11. Indications have been presented that variation in properties of the polysaccharide product may depend upon fermentation conditions.
Kinetics of polyether polyols–diisocyanate reactions
Authors: Wissman H. G. , Rand L. , Frisch K. C.
Published: April 2003

The reaction rates for the uncatalyzed as well as the dibutyltin dilaurate‐catalyzed reactions between polyether polyols and tolylene diisocyanate (80/20 mixture of 2,4 and 2,6 isomers) are reported. Titration and infrared absorption methods were used for the determination of the residual isocyanate content, to follow the progress of the reactions. At equivalent reactant concentrations, the rate constants were found to be essentially independent of the chain length and the functionality of the polyether polyols studied. The reaction rates of polyether polyols containing terminal primary hydroxyl groups (e.g., Pluronic polyols) were greater than those of polyols with secondary hydroxyl groups and were greatly accelerated in the presence of the tin catalyst.
Thermal expansion coefficient of polytetrafluoroethylene in the vicinity of its glass transition at about 400°K
Authors: Araki Yoshio
Published: April 2003

The linear thermal expansion of molded PTFE samples of various crystallinities was measured in the vicinity of the transition at about 400°K. In the plot of length of the specimen versus temperature, an inflection of the straight line was observed in the temperature range from 388 to 402°K., the mean value being 396°K. (123°C.) The change of the coefficient of linear thermal expansion at this temperature represents a typical feature of the second‐order transition or the glass transition, designated as Tg. The ratio Tg/Tm is equal to 0.66, in accordance with the so‐called ⅔‐rule between the glass transition temperature (Tg) and the melting point (Tm) of many polymers. The coefficients of linear thermal expansion, below and above Tg, designated α1 and α2 respectively, increased with increasing amorphous fraction, A. The extrapolated values of α1 and α2 at A = 0 were both 0.6 × 10−4 deg.−1, and those at A = 1 were 2 × 10−4 deg.−1 and 3 × 10−4 deg.−1, respectively. The value of TgΔβ/A, where Δβ = 3(α2 – α1), was approximately 0.12 which was closely in agreement with the value of 0.08 or 0.113 predicted by the theories for amorphous high polymers. From these experimental facts, it may be concluded that the transition of PTFE at about 400°K. is the glass transition which occurs in the amorphous region.
Viscoelastic behavior of the polycarbonate of bisphenol A
Authors: Mercier J. P. , Aklonis J. J. , Litt M. , Tobolsky A. V.
Published: April 2003

The viscoelastic properties and thermal expansion properties of bisphenol A polycarbonate have been studied in the neighborhood of the major glass transition temperature. A discussion is given of the possible relation of these properties to the unusual impact resistance of this polymer in the glassy state.
Dielectric behavior and resistivities of polyacrylonitrile and some pyrolyzates
Authors: Van Beek L. K. H.
Published: April 2003

Dielectric losses in polyacrylonitrile (PAN) and three pyrolyzates were studied between 1 Hz. and 300 kHz. Pure PAN has at 20°C. a very broad loss region with a maximum at 70 Hz. which is ascribed to CN groups. Powdered PAN was pyrolyzed in a nitrogen atmosphere at 170, 220, and 300°C. PAN‐170 has the same loss maximum as the unpyrolyzed polymer, but the maximum had disappeared in PAN‐220. This is attributed to formation of conjugated chains by linking of CN groups above 200°C. However, this does not enhance the conductivity until hydrogen is eliminated above 350°C.
Penetration of water‐soluble solutes into cellulose films
Authors: Aggebrandt Lars , Samuelson Olof
Published: April 2003

Nonsolvent water determined in very dilute solutions of polymetaphosphate can be used as a measure of the true swelling of cellulose films. From these values and determinations of nonsolvent water under conditions permitting a penetration of the solute into the film, the average molality of trimetaphosphate, polymetaphosphate, and polyglycols inside the film has been determined under equilibrium conditions. With the electrolytes, the molality ratio (film: external solution) is strongly dependent upon the external concentration, which can at least partly be ascribed to the effect of the charged carboxyl groups inside the film. With polyglycols the molality ratio increases with decreasing molecular weight. With dense films there is no detectable penetration of high molecular weight polyglycols. A comparison between various films is made. It is shown that these contain areas of varying packing densities. The dialysis of trimetaphosphate and polymetaphosphate across the cellulose films has also been studied. In dialysis against water there is, within a wide range of concentration, a linear relationship between the rate of dialysis (flux) and the average internal concentration determined in equilibrium experiments. It is interesting to note that this simple relation holds true although the films are inhomogeneous.