bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of thermal pretreatment on the strength of polycarbonate
Authors: Golden J. H. , Hammant B. L. , Hazell E. A.
Published: April 2003

The effect of preheat treatment at temperatures below the glass transition for various periods of time on selected properties of molded polycarbonate has been studied. Changes in tensile and flexural strength as functions of time and preheat temperature (80–140°C.) were determined and these are discussed in relation to changes in the nature of the β‐transition region and the influence of the glass transition region. It is suggested that the preheat treatment produces a greater degree of order within the amorphous region of the polymer, resulting in an increase in strength at temperatures up to 132°C. The strength of the polycarbonate before and after heat treatment appears to be independent of the presence of the equilibrium water content.
A modified balance‐type stress relaxation apparatus for chemical relaxation under liquid phase
Authors: Nisizawa Mizuho
Published: April 2003

A relatively simple and inexpensive automatic apparatus for chemical relaxation giving good accuracy has been developed for measurement of chemical relaxation in the gaseous phase in high polymers. The apparatus is based on a previously described balance‐type stress relaxation apparatus intended for automatic operation.
Determination of rates of thermal decomposition of polymerization initiators with a differential scanning calorimeter
Authors: Barrett K. E. J.
Published: April 2003

A commercial differential scanning calorimeter has been used to determine thermal and kinetic data of some typical polymerization initiators. Since the rate of heat change due to decomposition is directly related to the rate of decomposition at a given temperature, suitable analysis of the differential thermal curve can yield the Arrhenius parameters of a reaction from a single run. In order to test the method, the well‐established first‐order decomposition of azobisisobutyronitrile was determined in di‐n‐butyl phthalate as solvent. Reproducible results were obtained which accorded with published data by orthodox determinations. The rates of thermal decomposition in solution of benzoyl peroxide and diisopropyl peroxydicarbonate were also determined. The method provides a rapid means for the direct determination of fast rates not possible with orthodox analytical determinations.
A modified capillary dilatometer for polymerization
Authors: Nisizawa Mizuho
Published: April 2003

A relatively simple and inexpensive instrument giving good accuracy and easy operation has been developed for the measurement of volume change in monomer polymerizations. The instrument is based on a previously described capillary dilatometer intended for automatic operation.
Polymerization of asymmetric tetrafunctional monomers. I. The study of radical bulk polymerization of acrylic and methacrylic esters of 2‐allylphenol
Authors: Solomon O. F. , Corciovei M. G. , Tărărescu V.
Published: April 2003

The bulk polymerization of 2‐allylphenylacrylic ester and of 2‐allylphenylmethacrylic ester at 60–80°C. was studied. It was observed that under these conditions azobisisobutyronitrile, lauroyl peroxide, and benzoyl peroxide have satisfactory activity as initiators. The influence of atmospheric oxygen on AOAF and MOAF polymerization was proved. The peculiarities of AOAF and MOAF polymerization (low molecular weight of the soluble polymers which are formed, the absence of gel effect, relatively low critical conversions) may be explained on the basis of chain transfer reactions by the allylic groups.
Thermal degradation in oxygen of polymers with aromatic rings in the chain
Authors: Lancaster Joyce M. , Wright W. W.
Published: April 2003

The thermal degradation in oxygen of fifteen polymers containing aromatic rings in the chain has been studied by a weight loss method. The relative thermal stabilities of the different polymers have been determined and, where possible, the overall activation energy for breakdown. The results have been compared with those for samples of the same polymers degraded in vacuum. The most thermally stable of the polymers examined under oxidizing conditions was poly(2,6‐dichlorophenylene oxide), with a stability comparable with that of a copolymer of tetrafluoroethylene and hexafluoropropylene.
Wool–polymer systems: Effect of vinyl polymers on water absorption
Authors: Leeder J. D. , Pratt A. J. , Watt I. C.
Published: April 2003

Acrylamide, acrylic acid, and acrylonitrile have been polymerized in situ within wool fibers and the water‐absorption properties of the resultant wool–polymer systems compared with those of wool and the polymers measured separately. At high humidities, polyacrylamide and, to a lesser extent, poly(acrylic acid) caused increased water uptakes when expressed as a function of the original weight of wool, due to the hydrophilic nature of these polymers. This increase was less than that expected from the water contents of the wool and polymers measured as separate entities. Chain entanglements in the polymer–keratin network may be responsible for some reduction of water content. The presence of polyacrylonitrile in wool reduced the water content at high humidities to less than that of wool alone, indicating that “volume exclusion” of water by the polymers is also a contributing factor. At low humidities, the water content of the wool–polyacrylamide system is equivalent to the sum of the water contents of wool and polymer taken separately; in the case of poly(acrylic acid) the water content is less than that of wool and polymer considered separately, and this is attributed to ionic bonding. For wool containing polyacrylonitrile there is a reduction in water content at low humidities, indicating interaction between the polymer and polar sorption sites in the wool.
Relation between impact strength and dynamic mechanical properties of plastics
Authors: Wada Yasaku , Kasahara Tetsuo
Published: April 2003

A simple theory is developed which correlates the Izod impact strength of polymers with (G′100‐G′300)2/G′100, where G′100 and G′300 are dynamic shear moduli at 100°K. and 300°K., respectively. The theory assumes the Maxwell element for the material and the fracture time smaller than the relaxation time. The theory is verified by experimental data for numerous polymers. Another approach which correlates the impact strength with the integrated loss factor from 0 to 300°K. is also proved valid.
Oil well sand consolidation. I. Resins for a three‐step process
Authors: Parker P. Harold , Treadway B. R. , Brandt H.
Published: April 2003

Oil‐bearing formations often consist of loose sandy material. In the production of oil from these formations sand tends to be carried to the well bore along with the oil. The flow of sand can be prevented by consolidating or cementing together the sand particles of the formation around the well bore. The cementing has to be accomplished in such a manner that fluid flow channels between particles remain open. This paper describes a new three‐step process that was developed to consolidate oil well sand. The steps in the process involve injection of: (1) resin, (2) inert fluid, and (3) inert fluid containing a catalyst. In the first step of the process, resin in injected into the formation where it fully saturates the interstices between sand grains. Permeability is established in the second step by displacement of the excess resin from the interstices, thereby leaving a thin film of resin on the sand grains. In the third step, polymerization is activated by migration of catalyst from the inert fluid into the thin resin film on the sand. The process has the advantage that resin is placed and permeability is established before the resin is catalyzed. This avoids premature polymerization of the resin which might cause plugging of the formation or the tubing string used to inject resin. Desirable characteristics of a resin for the three‐step process are: (1) viscosity of 25–200 cp. at well bore temperature; (2) stability for several days at well bore temperature; (3) high adhesion to sand in the presence of an inert flushing fluid; (4) polymerization by less than 10% catalyst; (5) the polymerized resin binds sand together with a strong bond that is not affected by well fluids. Five different resin types have been tested for use in the three‐step sand consolidation process. These are: (1) epoxy–anhydride cured with a tertiary amine; (2) epoxy–epoxy diluent cured with a primary–tertiary amine mixture; (3) furan; (4) unsaturated polyester–vinylpyrrolidone; (5) unsaturated polyester–styrene. The two epoxy resins give strong, permeable consolidated sand which is resistant to well fluids such as brine and crude oil. The furan resin gives a weak consolidation. The unsaturated polyester–vinylpyrrolidone gives good strength and oil resistance but is sensitive to brine. The unsaturated polyester–styrene is difficult to apply. Many oil wells have been successfully treated in the Gulf Coast area and in California with the two epoxy resins. Almost all of these wells are producing free of sand, and, to date, more than five million barrels of oil have been produced from these wells.
Cellulose propionylpropionate as a side product in the reaction of cotton cellulose with propionyl chloride
Authors: Sircar Anil K. , Stanonis David J. , Conrad Carl M.
Published: April 2003

In the reaction of cotton cellulose fiber with propionyl chloride in pyridine–DMF medium, the degree of substitution based on weight gain was much higher than that based on saponification. Gas–liquid chromatograms of the pyrolysis products of the samples showed an extra peak. This was identified as 3‐pentanone, which arises from the pyrolysis of α‐propionylpropionic acid, a substance which was proposed by Malm and co‐workers as a possible side product. This conclusion was further confirmed by the infrared and NMR spectra of the liquid, collected fractionally on pyrolysis of the sample. Quantitative GLC showed that one òut of every four hydroxyl groups is substituted with an α‐propionylpropionyl moiety, the rest with propionyl groups. A possible mechanism for the side reaction has been proposed.
Epichlorohydrin–triethanolamine reaction in the preparation of quaternary cellulose anion exchangers
Authors: McKelvey John B. , Benerito Ruth R.
Published: April 2003

The reactions between cotton cellulose and a mixture of triethanolamine and epichlorohydrin in the presence of aqueous NaOH have been studied. It has been shown that cotton fabric pretreated with aqueous base and then reacted with a 3:1 mole ratio of epichlorohydrin to triethanolamine forms a strong base anion exchanger. Resultant properties differed from those of the product made by the conventional method of preparing ECTEOLA cellulose, a commercial product of the same reactants. Titration curves of the strong base cellulose exchangers were similar to that obtained with the product of the reaction between cotton and trimethylglycidylammonium chloride. Substitution of triethylamine for the triethanolamine also resulted in a quaternary base cellulose anion exchanger. A cyclic diquaternary salt, [2,5‐p‐dioxanylenebismethylene] bis[tris(2‐hydroxyethyl)ammonium chloride], has been isolated from the triethanolamine–epichlorohydrin mixture and a mechanism of the reaction has been proposed.
Reversible gelation of acrylonitrile–vinyl acetate copolymer solutions. II. Mechanical properties
Authors: Paul D. R.
Published: April 2003

Concentrated solutions of acrylonitrile polymers exhibit reversible gelation. The rate of gelation at 25°C. was determined for various solutions of an acrylonitrile copolymer containing 7.7% vinyl acetate in mixtures of dimethylacetamide (solvent) and water (nonsolvent) by measuring the shear modulus of the forming gel as a function of time. The mechanical properties were also measured on a series of gels formed by cooling solutions to −78°C. It was found that both the rate of gelation at 25°C. and the modulus of gels formed at −78°C. increase very rapidly as either the solids level of the solution of the water content of the solvent is increased. The gelation rate data wree correlated with the gel melting points of the gels. The results are discussed and compared with the analogous but limited data available for other systems.
Statistical description of the uniaxial creep behavior of polypropylene foam
Authors: Lepper Jay K. , Hetherington Norriss W.
Published: April 2003

The basis of a statistical method for the analysis of creep data is described. The method consists of response surface fitting to a Taylor series expansion of a function about a point. The method is capable of treating multiaxial stress data and includes other variables, such as temperature, without undue mathematical complications. In addition, the statistical approach can account for such things as experimental error and sample variation. The uniaxial compressive creep‐recovery behavior of a newly developed polypropylene foam was measured under loads of 140–705 g./cm.2and temperatures of 23–74°C. The foam has a nominal density of 0.07 g./cc. and a mean molecular weight between crosslinks of 10,000. The creep behavior is described by a Taylor series expansion through the second order of a function of applied load, test temperature, foam density, and log time.
Preparation and properties of polymers of secondary alkyl crotonates and related monomers
Authors: Graham Roger K. , Moore James E. , Powell John A.
Published: April 2003

The anionic polymerization of a variety of secondary alkyl crotonates and related monomers initiated by fluorenyllithium (complexed with tetrahydrofuran) in toluene at −78°C. is reported. No crystallinity could be developed in any of the samples, and nuclear magnetic resonance was uniformative about possible tacticity. The polymerization techniques were ineffective when applied to n‐alkyl esters. Polymer was obtained from isopropyl cinnamate and N,N‐dimethyl crotonamide, but not from isopropyl thiocrotonate or isopropyl 2‐pentenoate. The physical properties of injectionmolded specimens of polymers of isopropyl, s‐butyl and cyclohexyl crotonate were examined in some detail; the polymers exhibited a desirable combination of high service temperatures and good impact resistance for a vinyl homopolymer but were extremely difficult to mold. Poly(isopropyl crotonate) had a heat distortion temperature of 125°C. at 85 psi, a notched Izod impact of 2.4 ft.‐lb./in. of notch, and a flexural modulus of 274,000 psi.
Phenol transport in cellulose acetate membranes
Authors: Lonsdale H. K. , Merten U. , Tagami M.
Published: April 2003

Past detailed studies of solute transport through reverse‐osmosis membranes have been conducted only with simple salts. The present work with phenol was undertaken largely because of the practical observation that the transport of low molecular weight organics is much more rapid than that of the salts. Studies of phenol sorption from dilute aqueous solution indicate that the diffusion coefficient for phenol in water‐saturated 39.8 wt.‐% acetyl cellulose acetate is 9.6 × 10‐10 cm.2/sec., and the equilibrium distribution coefficient between the acetate phase and water is 42. Thus, the diffusion coefficient is quite close to that measured for sodium chloride, and the higher permeability of the membranes to phenol can be attributed entirely to their greater sorption of this solute. In direct osmosis experiments performed with significant water flow a measurable interaction or positive coupling between water and phenol flows has been observed. Further evidence of flow coupling is derived from reverse osmosis experiments in which significant negative solute rejection is observed; i.e., the permeate is enriched in phenol by as much as 20%. It is shown that a solution‐diffusion transport model is not adequate to rationalize the results, and a more complex transport model is apparently required.
Dynamic behavior of natural rubber during large extensions
Authors: Harwood J. A. C. , Schallamach A.
Published: April 2003

The stresses and energy losses during simple extension cycles up to a maximum elongation of 530% have been determined for an unfilled vulcanizate of natural rubber as a function of the temperature and extension rate. At sufficiently short elongation times and low temperatures, the rate and temperature dependence of the ascending stresses are connected by the Ferry transform, and the superposition principle can be applied to them. Outside this experimental range, the stresses are increased by crystallization. The validity of the Ferry transform for the energy losses and the energy loss ratio is more restricted than for the stresses, and the losses are always higher than can be expected from a purely viscoelastic mechanism. The additional losses are tentatively ascribed to incipient crystallization and stress‐softening effects. At short elongation times and low temperatures, the losses approach the values predicted by viscoelasticity, and the loss ratio becomes independent of the maximum extension of the strain cycle.
Delayed yielding of epoxy resin. II. Behavior under constant stress
Authors: Ishai Ori
Published: April 2003

Creep tests were carried out on epoxy resin specimens at room temperature and at different high stress levels under tension, compression, and flexure. Compared with the behavior at constant strain rate (CSR) reported in Part I of this work, creep strain–time curves revealed a distinct delayed yielding region of constant minimum rate (secondary creep) followed by a post‐yielding region of increasing slope (tertiary creep). In all cases, results indicate linearity between creep stress and log secondary creep rate, which is almost coincident with the corresponding relationship between yield stress and strain rate obtained in subsequent CSR loading cycles with the same specimens. The similarity in behavior under both the creep and CSR modes conforms to Eyring's theory of non‐Newtonian viscous flow at high stress levels and low temperature. Theoretical analysis yields reasonable values of the activation volume, which is unaffected by the loading and test modes or by loading history, and could thus be regarded as an intrinsic parameter of the microstructure, inherently related to the viscoplastic process involved. The above considerations indicate a deviatoric stress‐biased diffusional mechanism as the predominant factor in the yielding of an amorphous glassy epoxy system.
Regulation of molecular weight of styrene—butadiene rubber. I. Choice of regulator from the homologous series of xanthogen disulfides
Authors: Václavek Vladimír
Published: April 2003

The regulating efficiency of 14 dialkyl xanthogen disulfides in emulsion copolymerization of butadiene with styrene at +5°C. with the use of a diisopropylbenzene hydroperoxide–complexed ferrous iron–sodium formaldehyde sulfoxylate redox system in the presence of sodium soap of disproportionated rosin as an emulsifier, was evaluated. The apparent chain transfer constants of n‐alkyl and isoalkyl derivatives decreased logarithmically with increasing length of the alkyl group, which seems to be related to the analogous dependency of their solubilities in water. The dialkyl xanthogen disulfides, especially the lower homologs, acted as retarders of polymerization. The retardation did not affect their regulation efficiency. On the basis of values of the apparent chain transfer constants it is possible to predict the molecular weight of polymers, except for the region where the regulation is poor and where the deteriorative influence of termination and crosslinking reactions takes place. The diisopropyl xanthogen disulfide has been selected as the most convenient of the compounds studied for molecular weight regulation of emulsion copolymerization of butadiene with styrene in the system mentioned.
Transparency measurement of plastic sheet and film
Authors: Binsbergen F. L. , Van Duijn J.
Published: April 2003

Available methods for testing the transparency of plastic sheet and film have been found inadequate as regards the correlation between measurement and visual observation. A newly developed procedure, based on the determination of light transmission within a very small angle, gives good correlation. The application of the method and its limitations, due to the difference in optical effect of small‐angle and large‐angle scattering, are discussed. A description is given of the instrument, a special feature of which is that it gives direct readings of optical density and transparency.
Dilute solution properties of hydroxyethyl starch
Authors: Cerny L. C. , Graham R. C. , James H.
Published: April 2003

The dilute solution properties of hydroxyethyl starch (HES) were examined by using the techniques of osmometry, light scattering, and viscometry. The molecular weight range was approximately 2 × 106–0.06 × 106. Since HES is a branched molecule, its properties were compared with those of two linear counterparts, ethyl hydroxyethyl cellulose and hydroxyethyl cellulose. The branching index g was estimated to be about 0.3 when calculated from the intrinsic viscosity, radii of gyration, and second virial coefficients.
Supramolecular structure of propionylated cotton cellulose
Authors: Sircar A. K. , King Walter D. , Conrad Carl M.
Published: April 2003

Heterogeneous propionylation of cotton cellulose, in the form of yarn, was carried out by reaction with propionyl chloride, in a medium of pyridine and dimethylformamide (DMF). The product was a mixed propionate–α‐propionylpropionate ester of DS varying from 0.24 to 2.94. The supramolecular structure of these esters was studied by kinetic analysis as well as by the measurements of density, refractive index, and x‐ray diffraction. The Sakurada plot of DS against time of reaction showed a discontinuity at a DS of about 2.0, where the x‐ray diffraction pattern shows almost complete loss of crystalline structure. The interpretation, based on the assumption that the Sakurada curve actually represents the sum of two simultaneous rate processes acting in the amorphous phase and at the crystalline surfaces, seems to explain the data adequately. The density showed a continuous decrease, consistent with the idea of continuous destruction of crystalline structure with progressive substitution. Refractive indices showed a continuous decrease with substitution and birefringence was almost absent at complete substitution. The calculated value of molar refraction for the sample of DS 2.94 agreed closely with the experimentally observed value. The x‐ray diffraction intensity traces gave convincing evidence of the progressive decrystallization of cellulose with the degree of substitution. Decrystallization seems to be more or less complete at about a DS of 2.0.
Nitric acid digestion and crystallinity of ethylene–vinyl acetate copolymers
Authors: Barlow A. , Campbell R. C.
Published: April 2003

Nitric acid digestion studies of ethylene–vinyl acetate copolymers indicated that copolymers containing identical amounts of vinyl acetate but varying in melt index differed in crystallinity. These results were confirmed by x‐ray analysis. The differences in crystallinity were interpreted as showing a variation in the degree of short‐chain branching in the polyethylene segments of the copolymer chain. This variation was correlated with the conditions of synthesis.
The desorption of ethane–butane mixtures from polyethylene
Authors: Robeson Lloyd M. , Smith Theodore G.
Published: April 2003

The desorption of mixtures of ethane and butane at atmospheric pressure from low‐density polyethylene was investigated over the temperature range from 20 to 60°C. Desorbed penetrants were continuously trapped in glass tubes immersed in liquid nitrogen, and composition was determined as a function of time by means of gas chromatography. The ratio of the quantity of desorbed gas at any time t, qt, to the quantity at complete desorption, q∞, was used to determine diffusion coefficients and solubility constants. The diffusion coefficients for both ethane and butane increase with increasing butane concentration in the temperature interval investigated. The solubility of both penetrants can be correlated by Henry's law at 40, 50, and 60°C. However, at 20 and 30°C. the solubility constant for both penetrants increases with increasing butane concentration. This trend is consistent with experimental observations for single‐component diffusion and solubility of several hydrocarbons in polyethylene, where increasing concentration of penetrant plasticizes the polymer, resulting in increasing diffusion coefficients and solubility constants.
Bis[4(1‐methyl‐1,2‐epoxyethyl)] derivatives of phenyl ether, 1,4‐diphenoxybenzene, and bis(4‐phenoxyphenyl) ether
Authors: Neville Roy G. , Mahoney John W.
Published: April 2003

The syntheses of three new α‐methyl‐substituted bis(epoxyethyl) derivatives of phenyl ether, 1,4‐diphenoxybenzene, and bis(4‐phenoxyphenyl) ether are reported. Improved procedures for preparing 1,4‐diphenoxybenzene and bis(4‐phenoxyphenyl) ether by the Ullmann method are described. Infrared spectral data for the bisepoxides and their precursors are given, as are some reactions of the bisepoxides.
Permeation of water and sodium chloride through cellulose acetate
Authors: Rosenbaum Shlomo , Mahon H. I. , Cotton O.
Published: April 2003

The factors contributing to the selective permeation of water and sodium chloride through cellulose acetate membranes have been examined by the use of radioactive tracers. With decreasing acetyl content both the partition coefficient (solubility) and diffusion coefficient of water increased, the latter the more sharply. The effect was even more pronounced for salt, indicating that increasing selectivity with acetyl content stems mainly from increasingly preferential restrictions on salt mobility. Trends identical with those mentioned for decreasing acetyl content were found for increasing amounts of cellulose acetate solvents that had been extracted with water to yield more highly swollen membranes. A free‐volume treatment for diffusion of small molecules below the glass transition temperature with the aid of subgroup motion in the polymer is used for both components. The water content of the membrane at (or near) saturation emerged as the predominant factor in the permeation behavior. In view of the similarity in the activation energies of water and salt diffusion the far steeper dependence of the salt diffusion coefficient on water content could not be accounted for by size differences between the diffusing species and has been attributed to confinement of salt ions to locations at which multiple water contacts are feasible.
Infrared–deuteration study of regenerated cellulose fibers
Authors: Cumberbirch R. J. E. , Jeffries R.
Published: April 2003

This paper describes a study by infrared, deuteration, and other techniques of the fine structure of three regenerated cellulose fibers (Fortisan, a super tire yarn, and a fiber of high wet modulus). The infrared and deuteration measurement provide information on the amount and perfection of the hydrogen‐bond ordered material in these celluloses. The three fibers are markedly different in structure: the Fortisan contains about 40% ordered cellulose of a high average degree of perfection, whereas the super tire yarn contains a smaller amount (about 20%) of ordered cellulose of a lower average degree of perfection: the yarn of high wet modulus contains about as much ordered material as the Fortisan, but of an average degree of perfection more similar to that of the super tire yarn. Infrared‐dichroism measurements on the fibers are described. The infrared and dichroism studies are discussed in relation to the results of x‐ray, moisture regain, acid hydrolysis, and birefringence measurements on the fibers. The infrared‐deuteration behavior of acid hydrolysis residues prepared from the three fibers is described; these residues are more highly ordered than the patent fibers, but yield no information of any value in characterizing the structures of the parent fibers.
Synthesis and polymerization of tris(alkylamino)‐silance with epoxy prepolymers
Authors: Bilow N. , Murphy R. F. , Patterson W. J.
Published: April 2003

Phenyltris(methylamino)silane, phenyltris(ethylamino)silane, and vinyltris(hexylamino)silane were synthesized and evaluated as curing agents for epoxy resins. Cured resins derived therefrom have very good physical and dielectric properties. The moisture resistance of the resins evaluated was especially good for those derived from the vinyltris(hexylamino)silane. Typical dielectric properties of a phenyltris(ethylamino)silane‐cured epoxy specimen include a dielectric constant of 3.7 at 25°C. and a dissipation factor of 0.8%. Elevated temperature data are also presented.
Characterization of the structure of cellular plastics
Authors: Schael George W.
Published: April 2003

Equations are presented which allow calculation of the average cell volume, number of cells per unit area, cross‐sectional area, and average axial lengths of cells in formed plastics. The equation for the average volume of a group of cells has been derived to include terms which adjust for the effect of cellular anisotropy. This adjustment is made by including in the equation terms defining the number of cells (in terms of air displacement volumes) which occur in three planes of the specimen. Average cell volumes calculated with the derived equation were found to agree well with average volumes determined by measuring the volume of a known number of cells.
Preparation of ultrathin reverse osmosis membranes and the attainment of theoretical salt rejection
Authors: Riley R. L. , Lonsdale H. K. , Lyons C. R. , Merten U.
Published: April 2003

Cellulose acetate reverse osmosis membranes, 600–2800 A. thick, have been prepared on glass surfaces by dipping a clean glass plate into a dilute solution of cellulose acetate. After drying, the membranes are floated of onto a water surface and placed on molecular filter supports. Theoretical salt rejections, as calculated from the solution‐diffusion model of membrane transport for cellulose acetate, were obtained with imperfection‐free membranes.
Practical evaluation of the [η]–M relationship. III. Estimation of the exponent a
Authors: Van Krevelen D. W. , Hoftyzer P. J.
Published: April 2003

A method is proposed for predicting the exponent a of the Mark‐Houwink equation, [η] = KMa. This method makes use of the solubility parameters of polymer and solvent.
Oxidative aging of natural rubber vulcanizates. Part II. Effect of vulcanizate structure
Authors: Bell C. L. M. , Cunneen J. I.
Published: April 2003

The oxidation characteristics of protected and unprotected vulcanizates from natural rubber have been examined. With unpurified rubber (RSS1) in the presence or absence of added antioxidants the rate of oxidation of the vulcanizates is: unaccelerated sulfur > accelerated sulfur > TMTD sulfurless or EV > peroxide. This order is obtained because the sulfur compounds present in the sulfurated vulcanizates are antagonistic towards both natural and added antioxidants. The antagonism is greatest with polysulfides, and when they are present they dominate the aging behavior of vulcanizates.
Structural characterization of vulcanizates. Part VI. The 2‐mercaptobenzothiazole‐accelerated natural rubber–sulfur system
Authors: Moore C. G. , Porter M.
Published: April 2003

The crosslinking efficiency of sulfur in the vulcanization of natural rubber in the presence of 2‐mercaptobenzothiazole, zinc oxide, and lauric acid has been determined as a function of cure time, cure temperature, and lauric acid concentration. With a low concentration of lauric acid structurally complex networks are formed, which contain 11–19 combined sulfur atoms per chemical crosslink present. The complexity increases with time of vulcanization. With a high lauric acid concentration much simpler networks are formed, which become progressively more simple as reaction proceeds (6 network‐combined sulfur atoms per chemical crosslink, decreasing to 2.4 with time). Increasing the cure temperature from 100 to 140°C. reduces the efficiency of crosslinking in both cases. The changes in efficiency are attributed to the influences of the reaction variables (in particular, the concentration of rubber‐soluble complexes of the zinc laurate with zinc benzothiazolyl mercaptide) on the structure and subsequent reactions of initially formed polysulfidic crosslinks.
Structural characterization of vulcanizates. Part VII. The N‐cyclohexylbenzothiazole‐2‐sulfenamide‐accelerated natural rubber–sulfur system
Authors: Porter M.
Published: April 2003

The crosslinking efficiency of sulfur in the vulcanization system comprising (in parts by weight) natural rubber (100), sulfur (1.5), N‐cyclohexylbenzothiazole‐2‐sulfenamide (2.37), zinc oxide (5), and lauric acid (1–10) is relatively insensitive to the lauric acid concentration and to the temperature of vulcanization (between 100 and 140°C.). The networks formed contain initially 8–11 combined sulfur atoms per chemical crosslink present, but this number falls progressively to about 4 as the reaction proceeds. The results are consistent with the intermediate formation of a rubber‐soluble complex of cyclohexylamine with zinc benzothiazolyl mercaptide. This complex is believed to be responsible also for the further slow crosslinking which the vulcanizates undergo on standing at room temperature.
Physical characteristics of plasticized epoxy system in the post‐yield stage
Authors: Steg I. , Ishai O.
Published: April 2003

Thermo‐rheological analysis was conducted on epoxy–Versamid specimens drawn from different portions of beams subjected to a yield test. Mc values, characterizing the crosslink density and determined by a special method, show insignificant variation for unstressed (virgin), pre‐yield, and post‐yield zones of the material. It was concluded that the yielding process in the plasticized epoxy system consists mainly in disruption of physical bonds.
Role of adhesive–substrate compatibility in adhesion
Authors: Iyengar Y. , Erickson D. E.
Published: April 2003

For substrates such as polyesters having limited capacity for hydrogen bonding or other specific interactions, thermodynamic compatibility of the substrate and adhesive is shown to be a key factor in promoting bondability to the substrate. Such compatibility occurs, as shown by Abere, when the cohesive energy densities (CED) or solubility parameters (δ = √CED) of substrate and adhesive are matched. Investigations with polyester film‐adhesive‐film model systems with the use of a variety of nonpolar (hydrocarbon) and polar (chlorinated compounds, ethers, esters) adhesives illustrate how compatibility promotes bondability to poly(ethylene terephthalate). The poor adhesion of polyester fibers to resorcinol–formaldehyde–latex (RFL) adhesives is attributed to the incompatibility of resorcinol (δ = 16.0) with the polyester (δ = 10.3). Adhesion to RFL was improved by substituting the more compatible n‐hexyl resorcinol (δ = 12.5) for resorcinol in RFL adhesives. Currently, the best adhesive systems for polyester tire yarns are those (e.g., isocyanate–epoxy) involving formation of urethane polymers having matching δ values with poly(ethylene terephthalate).
Influence of thermal history on fusion curves of polyethylene
Authors: Ford R. W. , Scott R. A.
Published: April 2003

The effect of thermal history on the melting behavior of several linear polymer and copolymers of ethylene has been studied by using a Perkin‐Elmer DSC‐1 differential scanning calorimeter. Samples of film were heated above their melting point and then cooled at various rates in order to establish a known thermal history. During melting, homopolymers showed one peak and the copolymers two peaks in the DSC scan. The positions and relative sizes of the peaks were dependent on the prior cooling rate. It is suggested that two crystal types occur in the case of copolymers because of entanglements in the branched segments of the molecules. The position of the lower melting endotherm in blown films suggests that cooling rates of about 500°C./min. are achieved in this process.
Fractionation of polymers on a preparative scale by precipitation chromatography
Authors: Henderson J. F. , Hulme J. M.
Published: April 2003

A preparative‐scale elution chromatographic column is described which will fractionate 45 g. of polymer in a single operation. The size of the column is kept to manageable dimensions by reducing the temperature differential from 50 to 10°C. along the length of the temperature‐gradient section. It appears that this change limits the range of molecular weights that are in this section of the column at any one time which leads to a more uniform distribution of a polymer along the column. The net result is that the ratio of polymer load to cubic capacity of the column as a whole can be increased about tenfold over that for the conventional analytical column. It is shown that the equation derived by Caplan is valid under a variety of conditions and that this equation supports the arguments which lead to a reduced temperature differential in the column.
Photodegradation of poly(methyl methacrylate) in solution and the effect of added solutes
Authors: Fox R. B. , Price T. R.
Published: April 2003

Poly(methyl methacrylate) has been photolyzed with 2537 A. radiation in dioxane and in methylene chloride at about 25°C. in the presence and absence of air. In degassed solutions, quantum yields for random scission are only slightly affected by either intensity or polymer concentration. Oxygen is an apparent inhibitor for photodegradation. The inhibiting and sensitizing effects of a variety of added solutes, including aromatic hydrocarbons, aliphatic dienes, and ketones were investigated; the behavior is similar whether or not oxygen is present. The results are best explained on the basis of an electronic energy transfer mechanism involving the lowest excited triplet levels of the polymer and the added solutes.
Solution properties of lignin. Thermodynamic properties and molecular weight determinations
Authors: Brown W.
Published: April 2003

Number‐average molecular weights and the thermodynamic parameters ΔF̄1, ΔH̄1, and ΔS̄1 have been obtained for lignin in the solvents dimethylsulfoxide, dimethyl‐formamide, and dioxane. Widely different molecular weights were found in the different solvents and at the different temperatures as a consequences of molecular association. Analysis of the thermodynamic parameters revealed that these quantities are dominated by the change in solvent structure accompanying the solution process. A correlation between the “goodness” of a lignin solvent and the Hildebrand solubility parameter is consequently misleading in such systems.
Mass transfer during dry spinning of fibers
Authors: Fok Siu Yuen , Griskey Richard G.
Published: April 2003

The present investigation considered the transfer of mass during fiber formation with the dry spinning process, both experimentally and theoretically. Experimental data taken for the dry spinning of poly(methyl methacrylate)‐benzene solutions were treated with the equation of continuity of species. Two solutions of this equation were applied to the data. The first, an analytical solution with a number of restraints and assumptions, yielded good, semiquantitative results. The other solution determined by numerical analysis with fewer restraints yielded calculated data which predicted exactly the behavior of average fiber solvent concentration.
Kinetics of graft copolymerization of methyl methacrylate in wool fibers
Authors: Negishi Michiharu , Arai Kozo , Okada Sadayuki
Published: April 2003

The graft copolymerization of methyl methacrylate in wool fibers was investigated in the aqueous LiBr–K2S2O8 system without homopolymer. The rate of grafting and the degree of polymerization of graft polymer were determined on varying the extent of reduction of wool fibers and the concentration of monomer. From the graft copolymerization behavior observed at a given concentration of redox catalysts (LiBr and K2S2O8), the thiol groups in wool fibers were considered to play a role as a sort of catalyst of polymerization, not as the chain transfer agent, and also to give the grafting sites. So, the initiation process of grafting was assumed to be started by d[S·]/dt = ki[SH]eff, and the kinetic consideration was found to lead to the following expression in agreement with the experimental results: 1/DP = (kt/kp2[M]fib2)Rp, where d[S·]/dt is the rate of formation of thiol radicals by radicalotropy to SH from SO4−., OH·, or Br·; ki, kp, and kt are the rate constants of initiation, propagation, and termination, respectively; [SH]eff and [M]fib are the concentration of the effective thiol groups and the MMA monomers within the wool fibers, respectively; DP is the average degree of polymerization of graft polymers, and Rp the overall rate of grafting.
Crystallinity in secondary cellulose esters
Authors: Boy R. E. , Schulken R. M. , Tamblyn J. W.
Published: April 2003

Cellulose esters which have a high degree of esterification are readily crystallizable by simple heat treatments. Such esters include cellulose triacetate, cellulose tripropionate, and mixed cellulose triesters. X‐ray diffraction analysis shows distinct crystal patterns for these crystalline cellulose esters, and differential thermal analysis shows strong melting peaks. X‐ray diffraction analysis of secondary cellulose esters, that is, esters having a substantially lower degree of esterification, shows very diffuse patterns which are only slightly indicative of crystalline structure. Differential thermal analysis, on the other hand, shows strong endothermic peaks which appear to indicate melting of crystalline material. Once melted, secondary cellulose esters cannot be recrystallized easily by simple heat treatments, but it has been found that treatment with certain solvents will induce crystallization. For instance, precipitation of secondary cellulose acetate from acetic acid gave a material which showed two melting peaks by differential thermal analysis, and precipitation from acetone gave a material which showed a single melting peak. A secondary mixed ester, cellulose acetate butyrate, precipitated from acetone had three melting peaks. The coincidence of two of the peak temperatures of this ester with those of the separate triesters of acetic and butyric acids indicated a block rather than a random substitution into the cellulose chain.
Phase separation of some clear polyblends
Authors: Gesner B. D.
Published: April 2003

By using variations of elution and precipitation techniques, a clear ABS resin is found to be a mixture of a styrene–butadiene rubbery copolymer, a methyl methacrylate–styrene–acrylonitrile copolymer, and a graft of the methyl methacrylate–styrene–acrylonitrile copolymer onto the styrene–butadiene rubber. A clear impact acrylic is separated into a methyl methacrylate–styrene–acrylonitrile copolymer and a methyl methacrylate–butadiene rubbery copolymer. Photomicrographs indicate that clarity in the clear ABS and impact acrylic is achieved by matching refractive indices of the continuous and dispersed polymer phases.
Dichroism of an ideally oriented polymer chain
Authors: Kobayashi Yasuji , Okajima Saburo , Nakayama Kazuo
Published: April 2003

Visible dichroism can be utilized as a measure of the degree of orientation of an amorphous region in a polymer. But the relations between dichroism and states of dyes in polymer must be elucidated before dichroism can be used more widely as a reliable means for study of amorphous orientation. To calculate the orientation factor for visible dichroism, it is necessary to decide the dichroism of an ideally oriented polymer chain. For this purpose, a single crystal of Congo Red was prepared and the dichroic spectrum of the crystal was measured. It was found that the dichroism of the Congo Red molecule itself is unity in a suitable wavelength region. As a result, a simple means for the treatment of dichroic spectra was given. The angle between the polymer chain axis and the principal axis of the absorbed dye molecule was discussed.
Orientation factor of polypropylene film by infrared dischroism
Authors: Kobayashi Yasuji , Okajima Saburo , Narita Akiyoshi
Published: April 2003

The orientation factor by infrared dichroism of polypropylene film was compared with the other orientation factors. After the correction of imperfect polarization and the suitable choice of the base line, it was found that infrared dichroism is a reliable indicator of the orientation factor. Orientation factors obtained from the 998 and 842 cm.−1 bands agreed with the x‐ray orientation factor, and that from the 975 cm.−1 band agreed with the optical orientation factor.
Change of orientation by thermal contraction of polyacrylonitrile fiber
Authors: Kobayashi Yasuji , Okajima Saburo , Kosuda Hiroyuki
Published: April 2003

Polyacrylonitrile polymer powder was dissolved in 70% nitric acid and spun into isotropic filament through a glass nozzle of 0.5 mm. diameter in a coagulating bath of 30% nitric acid. Stretching was carried out in two stages: the first stretching was done in water at 20°C. followed by drying, and the second stretching was done in a boiling saturated solution of ammonium sulfate. The total stretching ratio was 23. These filaments were shrunk freely in water at 70–180°C. The change in orientation factors was traced by x‐ray, infrared dichroism, visible dichroism, and sonic modulus methods. The relation between the reciprocal absolute temperature of thermal contraction and the logarithm of fiber length is a straight line which has two inflection points at 93 and 175°C. The orientation factors by x‐ray and infrared dichroism remain unchanged up to 175°C. On the contrary, the orientation factors by visible dichroism and sonic modulus drop suddenly at about 90°C. This indicates the occurrence of relaxation of the amorphous chain at the glass transition temperature and shows the polymer is not perfect single‐phase material. Orientation of crystalline and amorphous phases is stable from 100 to 170°C. in spite of considerable thermal contraction. The stability of orientation can be explained by the growth of a folded structure in the polymer.
Reactions catalyzed by minerals. Part II. Chain termination in free‐radical polymerizations
Authors: Solomon D. H. , Swift Jean D.
Published: April 2003

The influence of aluminosilicates and magnesium silicates on the free‐radical polymerization of methyl methacrylate is discussed. The relationship between the structure of the mineral and its ability to inhibit radical reactions is considered, and it is concluded that aluminum in octahedral coordination is mainly responsible for the inhibition. Mechanisms which account for the termination reaction are proposed and supported by studies of the reaction of stable free radicals with the minerals.
Water‐containing resin based on unsaturated polyester
Authors: Horie Kazuyuki , Mita Itaru , Kambe Hirotaro
Published: April 2003

Unsaturated polyester resins containing water were prepared through two steps: formation of a stable W/O emulsion of polyester prepolymer and subsequent polymerization of the emulsion. In this paper, conditions for formation of the resins from the W/O type emulsion and the heat‐protection properties of the resulting water‐containing resins are reported. The stability of the emulsions was measured, and the results are discussed in relation to the gelation time, since the polymerization of the emulsions is required to proceed faster than their disintegration. It was found that with increasing viscosity of the emulsions their stability increases and the gelation time shortens. The above requirement is fulfilled at almost all regions of emulsifier concentration where stable W/O emulsions are formed. Water‐containing unsaturated polyester resins exhibit a remarkable heat‐protection effect at elevated temperatures (500 and 2500°C.) in comparison with polyester resins not containing water.