bluuebunny/crossref_metadata_2025 huggingface dataset:
Tensile response of polyacrylonitrile fibers during air heating
Authors: Layden George K.
Published: April 2003

Axial stresses generated by polyacrylonitrile filaments heated in air at constant length and length changes of filaments heated at constant load were measured. Fibers subjected to loads less than about 0.1 gpd shrank in the temperature range from about 40°C to 160°C. At about 160°C they began to stretch. Fibers that stretched out again to about their original lengths stiffened temporarily before undergoing a further elongation. At a temperature where the oxidation reaction begins to proceed with appreciable rate, elongation was retarded and finally reversed. Shrinkage was recorded during isothermal heating at 270°C, and a final length was approached when the oxygen content approached about 10 wt‐%. The tension generated when the fibers were restrained from shrinking increased as temperature increased to 160°C but dropped in the temperature range of 160° to 250°C. Tension again built up during isothermal oxidation at 270°C. In the case of one of the samples, the tension generated below 160°C exceeded the ultimate tensile strength of the fibers above 200°C. This condition leads to tensile failures when the filaments are heated in a steep thermal gradient. The tensile behavior of the filaments is discussed in terms of the helical molecular model.
Copolymerization of ethylene with vinyl acetate. I. Effect of polymerization temperature on degree of branching
Authors: Wisotsky M. J. , Kober A. E. , Zlochower I. A.
Published: April 2003

The degree of branching of a series of ethylene–vinyl acetate copolymers was found to be strongly dependent upon polymerization temperature. The copolymers were prepared by free‐radical polymerization and had low molecular weights and molar ratios of ethylene: vinyl acetate greater than 3:1. Nuclear magnetic resonance and infrared studies showed that copolymers prepared at 150°C were highly branched and had little crystallinity. Branches were mainly alkyl groups on the polymethylene backbone segments. There was no evidence of δ‐acetoxyalkyl branches. Long branches originating by intermolecular H abstraction from the acetylmethyl groups were also expected but could not be detected. These results were consistent with an intramolecular “backbiting” mechanism similar to that found in ethylene homopolymerizations. There was little or no participation by the vinyl acetate moiety in the branching scheme. Copolymers prepared at about 90°C had very few long or short branches and were more crystalline. Copolymers prepared between these temperatures had intermediate degrees of branching and crystallinity.
Preparation and purification of bisacid A2 (2,2‐diphenylolpropane 4,4‐dioxyacetic acid). II
Authors: Lenk R. S.
Published: April 2003

In an earlier communication1 the preparation of Bisacid A2 was described. This paper describes the attempts at spotting impurities in the products so obtained by subjecting them to thin‐layer chromatography. No traces of impurities could be detected since no separation whatever was observed. Infrared spectra of pure Bisacid A2 were found to be identical with the spectrum of Nanu and Boboescu.2 It was also seen that the product obtained by the standard preparation in 70–73% yield with a minimum melting point of 173°C could not be demonstrably improved by esterification and rehydrolysis. Second crops from first mother liquors from the aqueous acetic acid recrystallization of the crude precipitated product of the condensation reaction (as well as ether extracts from these mother liquors) showed that both contained material with phenolic OH groups. These are the inpurities in the crude product which must be completely removed during purification if the final material is to be used for the synthesis of unsaturated polyester resins for ultimate use as crosslinked reinforced plastics, as alkyd varnish bases, or as fiber‐forming saturated polyesters and polyamides. The need for adhering to the standard synthetic procedure was confirmed, in particular the need for multistage condensation, giving an effective yield of 70–73% of pure material
Solubility parameters and some structural characteristics of chlorinated poly(vinyl chloride)
Authors: Krozer S.
Published: April 2003

Measurements of solubility parameters of a series of chlorinated poly(vinyl chloride) (CPVC) samples were carried out. A maximum value of solubility parameter occurs at a chlorine content of 63–65% and is related to optimum packing.
Correlation between some solution and mechanical properties of poly(vinyl chloride) and chlorinated poly(vinyl chloride)
Authors: Krozer Shimon , Schneier Bernard
Published: April 2003

Correlations have been found between solubility parameters and some mechanical properties of a series of vinyl polymers containing 56.6–69.9% chlorine when tested below their glass transition temperature. It is shown that stress at yield increases similarly with chlorine content and with the volume occupied by a monomer unit in the polymer. Using the Reiner‐Weissenberg theory of the dynamic strength of materials as a criterion and a rheological model based on a pair of Maxwell bodies in parallel with a Hooke spring, the amount of dissipated and conserved work to yield point was calculated. A parameter, defined as the ratio of work to cohesive energy density, describes the efficiency of the system. The overall efficiency of the system, based on work to break, and proportional efficiency, based on work to yield point, are affected by chlorine content and strain rate. In addition, a potential energy parameter is defined which describes the cohesive energy per volume occupied by monomer unit of the polymer. This parameter is proportional to the total work to break as well as to the ratio of the residual work after yield to total work at all strain rates tested. The major portion of work is conserved up to yield; only a small portion is dissipated. From the yield point to break, after the onset of viscous flow, the major part of this work is dissipated.
Graft polymerization of some vinyl monomers onto acrylic rubber. I. Chain transfer and grafting reaction
Authors: Ide Fumio , Sasaki Isao , Deguchi Seiji
Published: April 2003

The grafting reactions of styrene (St), methyl methacrylate (MMA), and vinyl acetate (VAc) were investigated in the presence of n‐butyl acrylate–acrylonitrile copolymer. Results showed that the nature of monomer and initiator were the major factors influencing the grafting activity. The grafting efficiency was 0.87 for St, 0.26 for MMA, and 0.18 for VAc under the most favorable conditions. Acrylic rubber reduced the rate of polymerization, and the retarding effect increased in the order St, MMA, VAc. The chain transfer constants for acrylic rubber were evaluated to be 4.8 × 10−4 for St, 1.27 × 10−3 for MMA, and 1.45 × 10−3 for VAc. The rate of polymerization and the grafting efficiency decreased with increasing acrylonitrile content in acrylic rubber, while the chain transfer constant of St for acrylic rubber remained practically unchanged.
Characterization of NBR networks from stress–strain and swelling equilibrium measurements
Authors: Hassan A. M. , Ray L. N.
Published: April 2003

An improved stress–strain (S/S) method based on rubber elasticity theory and swelling equilibrium measurements was used to investigate the S/S behavior and the solvent swelling properties of nitrile–butadiene rubber (NBR) and also to study the effects of varying the cure agent and the curing conditions on the crosslinking efficiency in NBR vulcanizates. The S/S curve of completely swollen NBR vulcanizates is, as expected, in agreement with rubber elasticity theory, while that of dry or partially swollen vulcanizates is well described by the Mooney‐Rivlin equation. Determined in benzene, χ was 0.494, compared to 1.338 in cyclohexane and 2.124 in n‐heptane. The degree of crosslinking and the crosslinking efficiency in the NBR vulcanizates, moles of crosslinks produced per mole of crosslinking agent employed in the formula, are largely dependent on the nature of the crosslinking agent used and increase in the following order: peroxide, sulfur tetramethylthiuram disulfide, sulfur N‐cyclohexyl‐2‐benzothiazolesulfenamide, sulfur benzothiazyl disulfide, and finally tetramethylthiuram disulfide.
Preparation and properties of a diaryl sulfone‐containing unsaturated polyester
Authors: Spitsbergen J. C. , Loewrigkeit P. , Kim Y. K. , Lauzé W. L.
Published: April 2003

Thermoset poly(dipropoxylated bisphenol S–fumarate) showed an increase in heat deformation resistance over thermoset poly(dipropoxylated bisphenol A–fumarate). However, the poly(dipropoxylated bisphenol S–fumarate) required the incorporation of about 20 mole‐% of dipropoxylated bisphenol A into the polyester molecule to be styrene compatible. Condensation polymerization of various ratios of the dipropoxylated bisphenols with fumaric acid was employed to prepare the polyesters. The polyesters were then thermoset by crosslinking with styrene using a peroxide initiator. The thermoset of a poly(dipropoxylated bisphenol S–fumarate), into which 20 mole‐% of the dipropoxylated bisphenol A had been incorporated, had a heat distortion temperature 13°C higher than the poly(dipropoxylated bisphenol A–fumarate) thermoset.
Asymmetric oxidation of poly(vinyl sulfides) with percamphoric acid, aspergillus niger, and penicillium notatum
Authors: Yamaguchi Hidemasa , Minoura Yuji
Published: April 2003

The asymmetric oxidation of poly(phenylvinyl sulfide) (poly‐Ph VS) and poly(t‐butylvinyl sulfide) (poly‐t‐BuVS) was carried out with optically active percamphoric acid, and the optically active polysulfoxides were obtained. The values of the specific rotation for the oxidation products of poly‐PhVS and poly‐t‐BuVS were + 1.0 (having 56% of sulfoxide unit contents) and +9.1 (49%), respectively. The specific rotation of the product increased with increasing the contents of sulfoxide units. The optical rotatory dispersion curves of the oxidation products of poly‐PhVS and poly‐t‐BuVS were positive curves and were found to fit the simple Drude equation. The λc values of the oxidation products (poly‐PhVS, 271 mμ; poly‐t‐BuVS, 212 mμ) suggested that the chromophore which caused optically activity was the sulfoxide group. Similarly, the asymmetric oxidation of t‐BuVS–MMA copolymer, t‐BuVS–styrene copolymer, and PhVS–MMA copolymer was carried out, and the optically active copolysulfoxides were obtained. Furthermore, the biosynthetic oxidation of poly‐PhVS and PhVS–maleic anhydride copolymer treated with aqueous KOH was carried out using Aspergillus niger or Penicillium notatum in Czapeck solution, and the optically active polymers were obtained.
Preparation and properties of some poly(alpha‐olefin sulfones)
Authors: Crawford James E. , Gray Don N.
Published: April 2003

The properties of alpha‐olefin–sulfur dioxide copolymer prepared from the series C8–C18 (even‐numbered) alpha‐olefins and sulfur dioxide are described. These polymers undergo clean thermal degradation and have high permeabilities to oxygen and carbon dioxide. Maximum permeabilities, maximum per cent elongation at the yield point, and minimum density are obtained with the C16‐based polymer. An explanation is proposed involving a competitive plasticizing/side chain crystallization effect.
Graft copolymers of starch with mineral acid salts of dimethylaminoethyl methacrylate. Preparation and testing as flocculating agents
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E.
Published: April 2003

Mineral acid salts of dimethylaminoethyl methacrylate (DMAEMA) have been graft polymerized onto starch with ferrous ammonium sulfate–hydrogen peroxide initiation. The nitric acid salt was used in most reactions, and graft polymerizations were run in both water and aqueous–organic solvent systems. Increased monomer concentration in water led to an increase in both the percentage of poly(DMAEMA · HNO3) in the graft copolymer (percent add‐on) and the molecular weight of grafted branches. Variations in initiator concentration altered the percent add‐on only slightly but affected the molecular weight of grafted polymer significantly. When swollen starch, in contrast with unswollen starch was used in graft polymerization reactions run in water, the product had a higher per cent add‐on and a larger number of grafted branches of lower molecular weight. The efficiency of starch–poly(DMAEMA · HNO3) graft copolymers as flocculants for diatomaceous silica increased with per cent add‐on; however, variations in grafting frequency and graft molecular weight had less effect on the behavior of these materials as flocculants.
NMR studies of urea–formaldehyde resins
Authors: Kambanis S. M. , Vasishth R. C.
Published: April 2003

A procedure used for analyzing urea–formaldehyde resins by NMR spectroscopy was developed. Using this procedure, the condensation of dimethylolurea under acidic and alkaline conditions was sudied. It was confirmed that polymerization under acidic conditions proceeds via the formation of methylene linkages and under alkaline conditions, via the formation of dimethylene ether groups. The more highly condensed water‐soluble urea resins were found to contain hemiformal groups, which could be quantitatively determined. Two butylated urea–formaldehyde resins with varying degrees of butylation were also studied and were found to differ in the number of methylene and dimethylene ether groups and degree of butoxylation. Both were found to contain hemiformal groups. The resin with lower degree of butylation was also found to contain dimethyl ether linkages. None of the resins studied showed any detectable amounts of fully substituted amide groups.
Influence of hysteresis on tensile and fatigue failure in rubbers
Authors: Payne A. R. , Whittaker R. E.
Published: April 2003

The failure criterion developed by Harwood et al. between energy input to break and hysteresis at break for amorphous rubbers has been related to the fatigue and cut growth properties of the rubber which are based on the tearing energy theory. It is found that the constant K in the hysteresis failure criterion is a function of the cut growth constant G and the inherent flaw size C0. The effect of adding fine particulate fillers to amorphous rubbers on the hysteresis and fatigue properties is considered and shown to be in agreement with the theory.
Thermal analysis of polymers. VIII. Dilatometric and thermal optical behavior of sulfur
Authors: Miller Gerald W.
Published: April 2003

The use of combined modes of thermal analysis by differential thermal analysis (DTA), thermomechanical analysis, and thermal depolarization analysis (TDA) presents a more illustrative picture of the phase transitions and behavior of the allotropes of sulfur. Volumetric changes suggest the Tg of polymeric sulfur to occur at 35°C. Changes in depolarized light level and an abrupt change in volume at 77°C identify this change as a first‐order fusion. The depolarized light behavior of sulfur, which has been quenched from 200°C to −190°C, illustrates the probable existence of a mesomorphic state of sulfur between 100° and 122°C. Polymeric sulfur is thermally bleached near −150°C.
Compatibility of polystyrene and poly(methyl methacrylate) in benzene. Effects of molecular weight and temperature
Authors: Hong S.‐D. , Burns C. M.
Published: April 2003

The incompatibility of polystyrene and poly(methyl methacrylate) in benzene was examined at 20.1°, 40.0°, and 60.2°C. The incipient cloud points of solutions of equal weights of the two polymers were determined by a novel photometric method. Polystyrene samples with weight‐average molecular weights in the range of 3.27 × 105 to 6.43 × 104 and poly(methyl methacrylate) samples with weight‐average molecular weights in the range of 8.97 × 105 to 8.76 × 104 were used. Models describing the dependence on molecular weight of the critical concentration of a ternary polymer–polymer–solvent system, presented by Fuchs and by Kuhn et al., were examined in light of the experimental data. A modified model is proposed which gives an improved correlation of these results.
Rheology of concentrated suspensions
Authors: Chong J. S. , Christiansen E. B. , Baer A. D.
Published: April 2003

The dependence of the viscosities of highly concentrated suspensions on solids concentrations and particle size distributions is investigated by using an orifice viscometer. Based on the extensive amount of data on pertinent systems, an empirical equation which correlates the relative viscosities of suspensions (or relative moduli of filled polymeric materials) as a function of solids concentrations and particle size distributions is proposed. The equation has a constant which characterizes size distributions of spherical particles and can be determined experimentally without measuring viscosities. For uniform‐size spherical particles, it reduces to the well‐known Einstein equation at dilute solids concentrations.
Unusual film‐forming properties of aromatic heterocyclic ladder polymers
Authors: Arnold F. E. , Van Deusen R. L.
Published: April 2003

A new method of obtaining films of aromatic heterocyclic ladder polymers has been found which circumvents casting from high‐boiling acidic solvents. The BBL ladder polymer has been formed into tough, durable films by collecting suspensions of the polymer obtained from acid reprecipitations upon a fritted glass funnel. After drying, the polymer can be removed as film, with thickness dependent upon the amount of material used. Such a film has a tensile strength of 9,600 lb/in.2 as compared to a tensile strength of 16,000 lb/in.2 obtained from the same polymer when cast from methanesulfonic acid solution.
The rapid identification method of additives in polypropylene by mass spectrometry
Authors: Yoshikawa T. , Ushimi K. , Kimura K. , Tamura M.
Published: April 2003

For the rapid identification of additives such as antioxidant, ultraviolet absorber, and slipping agent, polypropylene containing such additives was heated in a tube connected directly to the inlet system of a mass spectrometer. The vapor of the additives evaporating out of the polypropylene was led to the reservoir and then submitted to mass spectrometry to give spectra for identification.
Hymatomelanic acids as polyelectrolytes. I. Viscometric and osmometric studies
Authors: Ghosh Kunal , Mukherjee S. K.
Published: April 2003

The polyelectrolyte character of four natural and ten synthetic hymatomelanic acids, synthesized from possible monomers both in the presence and absence of catalysts, was established by means of viscosity measurements. Intrinsic viscosities were evaluated for the purpose of comparison. The number‐average molecular weights of some typical natural and synthetic hymatomelanic acids were determined from osmotic pressure measurements. Using the Flory‐Fox relationship in an approximate manner, the root‐mean‐square average end‐to‐end separations were also evaluated.
Kinetics of sulfur‐free thiuram vulcanization
Authors: Ducháček Vratislav
Published: April 2003

Sulfur‐free thiuram vulcanization has been investigated at temperatures from 160° to 190°C over 0.5 to 600 min. Continuous measurements in a VUREMO curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Simultaneously the values of the network chain density were calculated from swelling measurements on the vulcanizates. The cure curves show clearly an induction period (ti), then fast crosslinking, a partial degradation, a “long‐time” crosslinking, and finally a slow, limited degradation. Apart from the induction period, the kinetic graphs are satisfactory represented by a rate equation assuming three independent first‐order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for fast crosslinking, for degradation, for slow crosslinking, and for t. Due to the presence of thiourea, the values of the induction period, the rate constant, and the extent of slow crosslinking are decreased. Simultaneously the activation energies calculated from degradation and slow crosslinking are significantly increased. On the basis of the above results, the mechanism of the sulfur‐free thiuram vulcanization, in which ionic and radical reactions take place, is discussed.
Particle production by polymer pyrolysis: Effect of carbon monoxide
Authors: Fischer Wm. H. , Lodge J. P.
Published: April 2003

The effects of carbon monoxide and water vapor on the production of condensation nuclei during the pyrolysis of various polymers were investigated. Carbon monoxide reduced nuclei production while H2O increased it. The effect of the two combined was variable and unpredictable. The necessity for and the possible direction of additional investigation is pointed out.
Aromatic rings as cure sites for EPM elastomers
Authors: Holmquist H. E. , Proskow S. , Barney A. L.
Published: April 2003

Terpolymers of ethylene and propylene with 4‐phenyl‐, 4‐o‐tolyl, 4‐p‐tolyl, and 4‐(1‐naphthyl)‐1‐butenes were vulcanized with bisbenzylic halides in the presence of highly acidic clays. The halides include bischloromethyldurene, p‐bischloromethylbenzene, and p‐bisbromomethylbenzene. Since the polymers contain no olefinic unsaturation, the crosslinking is achieved by electrophilic attack of the halide on the pendant aromatic rings. The order of activity is naphthyl > tolyl > phenyl. The new curing system also reacts with olefinic unsaturation. Thus, an EPDM elastomer and SBR rubber, the latter containing both aromatic rings and double bonds, were also readily crosslinked.
Ultraviolet stability of polyimides and polyamide–imides
Authors: Alvino W. M.
Published: April 2003

The ultraviolet stability of polyimides and polyamide–imides was determined in both a wet and dry environment. Films have been exposed to these environments for 3000 and 6000 hr, respectively. The polymers are not stable to UV radiation (2900–4000 Å); serious deterioration of the mechanical properties occurs under both wet and dry conditions with the former giving rise to greater damage. The polyamide–imide polymer is more unstable to UV radiation than the two polyimides evaluated; however, it is more resistant to hydrolysis as indicated from rate data obtained from a kinetic analysis of the mechanical property degradation curves. The electrical properties of the polymers are relatively unaffected in the dry environment but begin to deteriorate as the polymer becomes brittle. In the wet environment these properties begin to deteriorate more rapidly. Dissipation factor and dielectric strength are the properties most affected.
A study of the thermal behavior of graft copolymers of wool and methyl methacrylate
Authors: Varma D. S. , Sarkar R. K.
Published: April 2003

Thermal behavior of the natural and chemically modified wool fibers (treated with sodium hydroxide and formic acid and reduced with sodium bisulfite and thioglycollic acid) and of the graft copolymers of natural and modified wool with methyl nethacrylate (MMA) monomer was studied using dynamic thermogravimetry in air at a heating rate of 6°C/min to 600°C. The thermograms showed three distinct regions of weight loss for all the cases. A comparison of the temperatures of various percentage decompositions reveals that the thermal stability increased slightly with chemical modification of wool as compared to natural wool. Caustic soda and sodium bisulfite probably forms more stable lanthionine linkages, whereas formic acid improves the thermal stability perphas by modifying the noncrystalline region of the fiber. In the case of natural wool after graft copolymerization with MMA, thermal stability improves up to 325°C probably owing to the formation of new crosslinks, but after 325°C the thermal stability decreases owing to early decomposition of the polymer as compared to wool fiber. Similar effects are observed in all the chemically modified fibers except in wool reduced with sodium bisulfite, where thermal stability is found to increase after grafting even at higher temperature. The thermal stability was also computed from the primary thermograms by calculating the integral procedural decomposition temperature; the results show that thermal stability increases slightly with chemical modification of wool as compared to natural wool. In the case of natural wool with graft copolymerization with MMA, the overall thermal stability decreases, because the decrease of thermal stability after 325°C seems to be more prominent than the increase in thermal stability before 325°C. The same effects are observed in all the chemically modified fibers, except for fibers reduced with sodium bisulfite, where the overall thermal stability increases slightly with increase in graft‐on.
The mechanism of liquid transport through swollen polymer membranes
Authors: Paul D. R. , Ebra‐Lima O. M.
Published: April 2003

The pressure‐driven transport of liquids employed in reverse osmosis has been shown to occur by a solution‐diffusion mechanism in highly swollen polymer membranes. A theory based on this mechanism was successfully used earlier to correlate permeation fluxes for such membranes. Positive confirmation of this theory is provided here by direct measurement of the proposed concentration gradient. A study of the temperature dependence of the liquid diffusion coefficient in the polymer membrane has provided additional evidence of a hydrodynamic regime of diffusion in highly swollen membranes. It is also shown that the proposed ceiling flux in reverse osmosis is equal to the pervaporation flux.
Hydroboration of diene polymers
Authors: Minoura Yuji , Ikeda Hiroharu
Published: April 2003

Diene polymers (i.e., polyisoprene, polybutadiene, and butadiene—styrene copolymers) were hydroxylated in tetrahydrofuran by hydroboration with diborane and subsequent alkaline oxidative hydrolysis. The strong, broad infrared absorption of the product at 3340 cm−1 shows the introduction of hydroxyl group. The properties of hydroxylated diene polymers depend upon the extent of hydroxylation. The less hydroxylated polymers are rubbery. As the extent of hydroxylation increases, the product becomes a white thermoplastic which is soluble in alcohol. The hydroboration of diene polymers with diborane is very rapid. However, if the reaction is continued further, the extent of hydroxylation decreases because of side reactions. The results of acetylation and formylation of the hydroxylated products and the grafting of vinyl monomers onto hydroborated diene polymers are also presented.
ESR studies on the effect of lignin and gases on UV photodegradation of cellulose
Authors: Nanassy A. J. , Desai R. L.
Published: April 2003

Aspen wood pulp and aspen dioxane‐lignin were irradiated by ultraviolet light under vacuum employing a special technique for uniform irradiation of the powdered samples. Examination of the effect of various gases and lignin contents of the pulps on the ESR spectra showed that the spin concentration was reduced by oxygen and lignin content, while atomic hydrogen reduced it to zero. The width and shape of the line were unaffected by oxygen, while lignin content reduced the width. A resolution for the hyperfine component of the spectrum yields an average distance of 1.3 Å between the free spin at C‐5 and the protons at C‐6 of the cellulose.
Gel permeation chromatography: The effect of pore size distribution on separation efficiency
Authors: Cooper Anthony R. , Johnson Julian F.
Published: April 2003

Columns packed with Bio‐Glas (porous glass manufactured by Bio‐Rad Laboratories, Richmond, California) of varying porosities were made which had the same cumulative pore volume. The pore radii were equal to or larger than the mean end‐to‐end distance of the 160,000 molecular weight polystyrene molecule in carbon tetrachloride. The efficiency of these columns was studied for the elution of polystyrene Mw = 160,000 and two sharp polyisobutene fractions having Mn = 114,700 and 145,700. Elution volume was found to be independent of flow rate below a flow rate of 1 ml/min for all columns studied. Two pairs of columns with the differing cumulative pore volumes were compared, and only small differences were found in their efficiencies, as measured by the number of theoretical plates per foot. The pore size distribution is important in that it determines elution volumes and the effective separating range of the column, but it does not appear to materially affect the efficiency of the separation process.
Cellulose graft copolymers. IV. Graft copolymerization of methacrylonitrile with γ‐irradiated cellulose from DMSO–, acetone–, and methanol–water systems
Authors: Mares Trinidad , Hinojosa Oscar , Nakamura Yoshio , Arthur Jett C.
Published: April 2003

Methacrylonitrile was graft‐copolymerized from DMSO–, acetone–, and methanol–water systems with γ‐irradiated, purified cotton cellulose. The relative extents of scavenging of the free radicals in the irradiated cellulose after immersion in the solvents for 3 min at 25°C, as determined by electron spin resonance spectroscopy, were: methanol (77%) > water (70%) ≫ acetone (5%) > DMSO (0%). After immersion of irradiated cellulose in the solvents for 60 min at 25°C, the relative extents of scavenging of the radicals were: methanol, water (80–85%) > DMSO (80%) > acetone (62%). From these data, it would appear that the overall rates of diffusion of methanol and water into the fibrous macrostructure were greater than the rates of diffusion of DMSO and acetone into the structure. The relative radiochemical yields of the graft copolymerization reactions of methacrylonitrile with irradiated cellulose in the different solvents were: water ≫ DMSO > methanol ≫ acetone. The addition of water to the systems increased the yields of the reactions.
Viscoelastic properties of epoxy resin. I. Effect of prepolymer structure on viscoelastic properties
Authors: Hata Naoaki , Kumanotani Ju
Published: April 2003

The intermolecular cyclization reaction is investigated in highly crosslinked epoxy systems, where diepoxides with different mobilities between terminal epoxy groups were crosslinked with ethylene diamine. Based on the measured values of the Clash‐Berg 10‐sec modulus in the rubbery region, the correlation between the mobility and the cyclization reactivity of the diepoxides is discussed. The epoxide with higher mobility is found to have a higher rubbery modulus than that with lower mobility, as was expected. This is tentatively explained by the difference in the reactivity of the formation of the 11‐membered ring. Dynamic mechanical measurements were also run on a forced vibration apparatus. The higher β‐transition peak of the polymer of bisphenol‐A diglycidyl ether was interpreted in terms of its higher free volume as well as lower density and lower glassy modulus. The higher modulus in the glassy region of ethylene glycol diglycidyl ether–ethylenediamine was explained on the basis of hydrogen bonding.
Energy absorption in polymeric foams. II. Prediction of impact behavior from instron data for foams with rate‐dependent modulus
Authors: Schwaber David M. , Meinecke Eberhard A.
Published: April 2003

Impact behavior can be predicted for rate‐dependent foams from constant rate of strain response. The response must be factorized into a rate‐dependent modulus function and a strain‐dependent function. In this way the rate‐dependent modulus can vary throughout the impact as the velocity of the impacting object decreases.
Starch graft polymers. I. Graft Co‐ and terpolymers of starch with 2‐hydroxy‐3‐methacryloyloxypropyl‐trimethylammonium chloride and acrylamide: Preparation and evaluation as silica depressants
Authors: Jones Duane A. , Jordan Wesley A.
Published: April 2003

The title monomers have been grafted onto wheat starch by γ‐radiation‐induced polymerization in water providing three graft polymers containing poly[2‐hydroxy‐3‐methacryloyloxypropyltrimethylammonium chloride (I)] and two graft polymers containing poly[I and acrylamide (II)]. Characterization is discussed together with their utility as silica depressants in flotation‐beneficiation of siliceous ores. Results are provided to illustrate that a starch graft copolymer containing 15% poly(I) graft and a graft terpolymer containing 30% poly(I, II) in the ratio 1:2 are effective as selective depressants for silica in flotation‐beneficiation of Florida pebble phosphate ore using special flotation conditions.
The gel permeation chromatography of phenolic compounds
Authors: Yoshikawa T. , Kimura K. , Fujimura S.
Published: April 2003

Gel permeation chromatography, using polystyrene gel and tetrahydrofuran as solvent, has been applied to hydroxybenzophenones, esters of salicylic acid, alkylphenols, alkylated methylenediphenols, and phenol–formaldehyde condensation products. The difference between the calculated molecular volume of these phenolic compounds and that obtained by actual determination with GPC has been ascribed to tetrahydrofuran solvation of the phenolic hydroxyl group. Furthermore, it has become clear that THF solvation is affected by the steric hindrance of ortho‐substituted phenol and by inactivation of the phenolic hydroxyl group resulting from internal hydrogen bonding.
Effects of monomer impurities on the emulsion polymerization of chloroprene and properties of polychloroprene. IV. Effect of 1‐chloro‐1,3‐butadiene
Authors: Sufčák Miloslav
Published: April 2003

The influence of small amounts of 1‐chloro‐1,3‐butadiene on the kinetics of the emulsion polymerization of 2‐chloro‐1,3‐butadiene and on properties of the resulting polychloroprene has been studied. Some changes in the properties of the chloroprene polymers were observed at 1‐chloro‐1,3‐butadiene concentrations in monomer as relatively high as about 5%. Polymer prepared in the presence of 5% 1‐chloro‐1,3‐butadiene had decreased tensile strength, and also its crystallization tendency was somewhat lowered. At 1‐chloro‐1,3‐butadiene concentrations near 1% or higher, the polychloroprene obtained had worsened thermo‐oxidation stability which resulted in crosslinking during aging. The kinetics of emulsion polymerization of chloroprene are not influenced by 1‐chloro‐1,3‐butadiene up to 5%.
Effects of monomer impurities on the emulsion polymerization of chloroprene and properties of polychloroprene. V. Effect of 1,3‐dichloro‐2‐butene
Authors: Sufčák Miloslav
Published: April 2003

The emulsion polymerization of chloroprene in the presence of 1,3‐dichloro‐2‐butene in various concentrations up to 5% was studied. In contrast to all other common chloroprene impurities, no influence of this compound on the kinetics of chloroprene polymerization and the properties of polychloroprene was found. 1,3‐Dichloro‐2‐butene does not cause polymer chain transfer and it is not able to copolymerize with chloroprene under the given polymerization conditions.
The graft photopolymerization of acrylates and methacrylates on wool in dimethyl sulfoxide
Authors: Needles Howard L.
Published: April 2003

Irradiation of wool by short‐wavelength ultraviolet light in the presence of acrylate or methacrylate esters in dimethyl sulfoxide causes intermediate grafts (2%–10%) of polymer on the surface of the wool. The amount of grafting and homopolymerization and the evenness and regularity of photografted polymer are dependent upon the monomer used. With methyl acrylate, the reaction time, monomer concentration, and introduction of water as cosolvent affect the degree of fiber grafting and the amount and molecular weight of accompanying homopolymer. Polymers grafted onto wool by this technique change the tensile properties and the water desorption characteristics of the wool.
Measurement of the rheological properties of polymer melts with slit rheometer. II. Blend systems
Authors: Han Chang Dae
Published: April 2003

A slit rheometer described in part I of this series was used for characterizing two blend systems by their viscous and elastic properties in the molten state. The blend systems chosen for study were blends of two high‐density polyethylenes having widely different molecular weight distributions and blends of polystyrene and polypropylene which are incompatible in the molten state. The present study shows that blends of two high‐density polyethylenes and blends of polystyrene with polypropylene exhibit a minimum in melt viscosity and a maximum and minimum in melt elasticity (in terms of “exit pressure”) at certain blending ratios. These results confirm the author's earlier findings, which were obtained with a capillary rheometer.
Measurement of the rheological properties of polymer melts with slit rheometer. III. Two‐phase systems—high‐impact polystyrene and ABS resin
Authors: Han Chang Dae
Published: April 2003

Measurements were made of the rheological properties of commercially available rubber‐reinforced two‐phase polymer systems. The polymers chosen for study were two high‐impact polystyrenes (Union Carbide Corp., TGDB9500 and TGDB2100) and an acrylonitrile–butadiene–styrene (ABS) resin (Monsanto Co., Lustran I240 Natural). For the study, a slit rheometer was used, which was described in part I of this series. The present paper, the third of this series, clearly demonstrates the usefulness of the slit rheometer for characterizing polymer systems of industrial importance by means of their viscous and elastic properties in the molten state.
Structural characterization of vulcanizates. XII. Efficient vulcanization using a sulfenamide–thiuram disulfide accelerator system
Authors: Campbell D. S.
Published: April 2003

Vulcanizates obtained from the sulfur vulcanization of natural rubber using a combination of the accelerators N‐cyclohexylbenzothiazole‐2‐sulfenamide (CBS) and tetramethylthiuram disulfide (TMTD) have been analyzed in terms of the numbers of poly‐, di‐, and monosulfide crosslinks, network‐bound accelerator residues, and cyclic sulfide chain modifications as a function of cure time. The vulcanization system produced mainly monosulfide crosslinks at optimum cure, although there were differences in detail between this mixed system and a previously reported efficient sulfur vulcanization (EV) system using a high ratio of CBS to sulfur.
The determination of adjacent oxypropylene–oxyethylene units in propylene oxide–ethylene oxide adducts by infrared spectroscopy
Authors: Gibson U. H. , Quick Q.
Published: April 2003

A study of several base‐catalyzed propylene oxide—ethylene oxide adducts of glycerin and certain model compounds has shown that an infrared absorption band at 10.30 μ can be associated with a structural entity represented by an oxyethylene unit attached to an oxypropylene unit at the secondary position. Coupled with other information such as total oxyethylene content and primary hydroxyl content, this finding has proved most useful in differentiating average molecular structure for commercial polyether polyols used in the manufacture of polyurethanes.
Effect of concentration of atactic polypropylene on its rate of autoxidation
Authors: Jadrnicek B. R. , Stivala S. S. , Reich Leo
Published: April 2003

A general scheme previously reported for the autoxidation of polyolefins is further substantiated by results obtained for the uncatalyzed and catalyzed autoxidation of various concentrations of atactic polypropylene (APP) (by admixture with polyisobutylene) under various experimental conditions. Thus, rates of maximum carbonyl formation were measured as a function of APP concentration at 120°C, oxygen concentrations ranging from 0.5%–100% by volume and cobaltic acetylacetonate catalyst concentrations (3 and 17) × 10−7 mole/7.5 mg sample. Good agreement was found between experimentally observed and theoretical dependencies of the maximum carbonyl formation rate on APP concentration derived from the combined reaction scheme.
X‐ray low‐angle scattering from oriented poly(ethylene terephthalate) films
Authors: Heffelfinger C. J. , Lippert E. L.
Published: April 2003

Low‐angle x‐ray scattering data are used to deduce the morphology of oriented polymeric films. Generally, the structural models proposed to explain these patterns have been extrapolations of observations made from solution‐grown polymer single crystals or from highly crystalline bulk polymers. These models and explanations may not be applicable broadly to oriented systems having only modest amounts of crystallinity or to those generated from precursor states that are grossly different. Poly(ethylene terephthalate) (PET) was chosen as a model polymer system for study. A systematic series of uniaxially and biaxially deformed films were produced from this polymer, made from the initially glassy or crystalline states. The low‐angle x‐ray scattering patterns generated from these films were studied as a function of (a) the sequence of deformation, (b) the precursor structure, (c) molecular orientation, and (d) the direction of observation. Optical diffraction and model structures were used to aid in the interpretation of the morphology produced. At least three different‐sized domains are developed upon deformation, ranging from that of the unit cell (about 10 Å) to large laminar domains of average size 2,000 Å × 10,000 Å. This structure is shown to be substantially different from that developed in an oriented polyethylene film.
Effect of wavelength region on photo‐induced graft copolymerization onto cellulose
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

The effect of wavelength region of ultraviolet light was examined on the unsensitized photo‐induced graft copolymerization of methyl methacrylate onto cellulose. When the quartz tube system was compared to the glass tube system, there was no induction period of copolymerization, the rate of reaction was a little larger, the homopolymerization of methyl methacrylate was increased causing interference with graft copolymerization, and the depolymerization of grafts and the scission reaction of cellulose chains occurred easily. The number of grafts was hardly improved by varying the reaction conditions, and the copolymers obtained generally exhibited low per cent grafting and contained grafts with lower degree of polymerization.
Calculation of molecular weight for polymers produced in continuous‐flow stirred reactors
Authors: Cozewith Charles
Published: April 2003

For addition polymers produced in continuous flow stirred tank reactors, a method is described for deriving equations for the degree of polymerization directly from the equations for the polymerization kinetics. Through use of this technique, relationships are obtained for calculating the number and weight average degree of polymerization in both homo‐ and copolymerization.
Iodine treatment of nylon: Effect on metal plating of the polymer
Authors: Abu‐Isa Ismat A.
Published: April 2003

The iodine treatment of nylon surfaces consist essentially of dipping the nylon in an iodine—potassium iodide solution and quickly rinsing the absorbed iodine out of nylon surfaces using glycol—water—thiosulfate as a wash solution. The treatment was found to profoundly affect the adhesion between the nylon and an electrolessly deposited metal on its surface. The adhesion changes from no adhesion for an untreated nylon surface to a maximum of 28 lb/in. for a treated sample. The adhesion is dependent mainly on the nature of the nylon surface (crystallinity, molecular weight, etc.), the duration of the iodine treatment, and the nature and conditions of the wash solution. Electron microscope pictures of the nylon surface after the iodine treatment show a shallow etching pattern, and therefore mechanical keying between the metal and the polymer is not a probable factor of importance. Under certain experimental conditions, the iodine treatment changes the crystallinity from the α‐form predominant in the nylon before treating the sample to the γ‐form. It also decreases the overall crystallinity of the surface, softens the polymer, and improves its water wettability. All the above changes enhance a more intimate interaction between the deposited metal and the polymer.
Physicochemical criteria for reverse osmosis separation of alcohols, phenols, and monocarboxylic acid in aqueous solutions using porous cellulose acetate membranes
Authors: Matsuura Takeshi , Sourirajan S.
Published: April 2003

Reverse osmosis data of 32 different alcohols and phenols and 22 different monocarboxylic acids in aqueous solutions in the concentration range 0.0001 to 0.007M (∼100 ppm in most cases) have been studied using porous cellulose acetate membranes at 250 psig. Solute separation data for alcohols and phenols are correlated with Δνs (shift in the OH band maximum in the IR spectra), and those for the monocarboxylic acids are correlated with Ka (dissociation constant) and the degree of dissociation of the molecule. Solute separation decreases with increase in Δνs for alcohols and phenols. The solute separation‐versus‐Ka correlation for acids passes through a minimum, and solute separation always increases with increase in the degree of dissociation. The separation data are also correlated with Taft and Hammett numbers which represent the effect of the substituent group on the polar effect of the molecule. The product rate data show a general tendency to decrease with decrease in solute separation in all cases. These results show that, with respect to the systems considered, solute separation in reverse osmosis is governed by the hydrogen bonding ability of the organic molecule when it is essentially undissociated and by electrostatic repulsion of ions when the molecule is partially or completely dissociated. Thus, data on Δνs for alcohols and phenols, and those on Ka and degree of dissociation for monocarboxylic acids, constitute precise physicochemical criteria for reverse osmosis separation of the above solutes in aqueous solutions using porous cellulose acetate membranes.
The graft copolymerization of styrene and lignin. I. Hydrochloric acid lignin
Authors: Phillips R. B. , Brown W. , Stannett V. T.
Published: April 2003

The effects of methylation of phenolic hydroxyl groups and addition of solvent on the radiation and chemically initiated graft copolymerization of styrene and hydrochloric acid softwood lignin were studied. In the radiation‐induced experiments, methylation is found to increase the maximum per cent graft obtainable two or threefold, while methanol addition may increase the value tenfold. Chemically initiated experiments indicate that the main effect of methanol addition is to increase the accessibility of the lignin particles. A mechanism of graft copolymerization of polystyrene and lignin is proposed which requires the reaction to proceed primarily by chain transfer of a polystyrene chain radical to lignin and the subsequent reinitiation of polymerization (i.e., initiation of graft copolymerization) by the lignin radical. The grafting of lignin modifications is then dependent on the type of radical formation (i.e., phenoxy or benzylic) most favored, as well as the usual accessibility considerations.
Properties of hydroxyl‐terminated polybutadiene‐urethane systems
Authors: Consaga John P. , French David M.
Published: April 2003

The properties of liquid hydroxyl‐terminated polybutadiene (HTPB) stocks crosslinked with isocyanates of different functionalities were intensively investigated. The stocks were modified by inclusion of small proportions of various low molecular weight diols to increase the urethane concentration. The following studies were carried out: (1) the system functionality was varied at a low and relatively constant urethane concentration; (2) the system functionality was varied with the urethane concentration constant but at a higher level; (3) at a constant crosslink density, the urethane concentration was varied by adding low molecular weight diols; and (4) the structure of the diols used in the previous experiments was varied.

A correlation between the per cent functional groups reacted, the average functionality of the system, and the mechanical properties of simple HTPB stocks was attained. Furthermore, a correlation was found between mechanical properties and urethane concentration at constant crosslink density. The properties of the stocks could be varied enormously by addition of low molecular weight diols in relatively small proportions by weight. The structure and concentrations of these diols caused significant variations in the elongation‐at‐break and tensile strength values.