bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric loss features of some epoxy resins
Authors: Cohen Merrill , Kohn Leo S. , MacDonald David I. 
Published: April 2003

AbstractAt 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

AbstractHigh 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

AbstractExperimental 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractStress‐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

AbstractThe 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

AbstractLinear, 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

AbstractThe 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

AbstractExperimental 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

AbstractTensile 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

AbstractA 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

AbstractAn 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

AbstractPolyesters 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

AbstractHigh 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

AbstractA 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

AbstractLow 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

AbstractThere 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

AbstractThe 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

AbstractThe 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.