bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of aromatic groups on localization of high energy in cellulose
Authors: Arthur Jett C. , Stanonis David J. , Mares Trinidad , Hinojosa Oscar 
Published: April 2003

AbstractWhen γ‐radiation from 60Co interacted with fibrous cotton cellulose, the localization of at least part of the high energy resulted in cellulosic chain cleavage and loss in breaking strength of the irradiated fibers. The substitution of aromatic groups on the cotton cellulose molecule affected this localization of energy and decreased the radiation degradation of the fiber. The nature of the linkage of the aromatic group to the cellulose molecule was not as important as the radiation stability of the linkage. For example, if localization of energy occurred which cleaved the aromatic group from the cellulose molecule, the radioprotection of the cellulosic molecular chain by the aromatic group was not effective. If the aromatic group was so modified that the effective number of π‐electrons was decreased, the radioprotection of the cellulosic chain was also decreased. The radioprotection of the cellulosic molecular chain by benzhydryl, trityl, benzoyl, and cinnamoyl groups was effective over distances equivalent to several cellobiose units. The radioprotection of the cellulosic chain by naphthoyl groups was significant but not as effective as the listed groups. Due to the sharing of π‐electrons in the naphthoyl group, the effective number of π‐electrons was reduced, and consequently the radioprotective effect of the group was also reduced. Benzyl groups were cleaved from the cellulose molecule on irradiation and offered no radioprotection to the cellulosic chain, at least at the high radiation dosages used. The ESR spectra of the irradiated celluloses, both substituted and unsubstituted, were similar. This indicated that the presence of aromatic groups did not change the nature of the long‐lived free radicals induced in cellulose on irradiation. It was suggested that selective energy absorption by the aromatic group from the spur of high‐energy electrons produced on interaction of γ‐radiation with the cellulose molecule could account for the radioprotection of the cellulosic molecular chain.
ESR study of post‐irradiation reactions of cellulose and acrylonitrile
Authors: Baugh Peter J. , Hinojosa Oscar , Arthur Jett C. 
Published: April 2003

AbstractAn ESR study of the free‐radical mechanisms of the post‐irradiation reactions of cotton cellulose with acrylonitrile is reported. The effects of atmosphere, moisture content, and solutions of acrylonitrile on the yield and stability of free‐radical sites in irradiated cellulose were determined. On interaction of γ‐radiation from a 60Co source with cotton cellulose, long‐lived free‐radical sites were found within the molecular lattice. Short‐lived free‐radical sites were apparently also formed on chain cleavage, gave strong singlet spectra, and were readily accessible to interaction with water. Other free‐radical sites were formed within regions of the cellulosic fiber which were inaccessible to moisture or aqueous solutions even after contact times as long as three days. It was suggested that long‐lived free‐radical sites in cellulose I (containing regain moisture) resulted from dehydrogenation at C5, and in cellulose II (containing regain moisture) resulted from dehydrogenation at C5 and dehydrogenation of the OH group or dehydroxylation at C6. When irradiated cellulose was contacted with a solution of acrylonitrile (15%) in 75% aqueous zinc chloride, the initial rate of decrease in spin concentration was higher than the rate of decrease as the time of contact increased. The ESR spectrum of the reacted cellulose, observed at −100°C., as compared with the spectrum for the irradiated cellulose, had decreased in signal strength with increase in time of contact and changed from a three‐line spectrum to an ill‐defined spectrum. The free radical being observed was probably due to unreacted sites in the cellulose. The extent of the graft copolymerization reaction was directly related to the initial spin concentration in the irradiated cellulose.
Diethylaminoethyl cellulose–epoxide reactions
Authors: Soignet Donald M. , Benerito Ruth R. , McKelvey John B. 
Published: April 2003

AbstractReactions of various monoepoxides and diepoxides with diethylaminoethyl (DEAE) cellulose in the absence and presence of external catalysts have been studied. In the absence of additional catalysts, many epoxides which did not react with the unmodified cotton reacted with DEAE‐cotton. Others, which reacted with unmodified cotton in the presence of external bases, imparted different properties when catalyzed by the builtin tertiary amino groups of DEAE‐cotton. For example, epichlorohydrin reacted with DEAE‐cotton to produce a fabric with excellent conditioned recovery, good wet recovery, and strong‐base anion exchange properties. The same epoxide imparted only wet crease recovery to cotton when the reaction was catalyzed by external bases. Phenyl glycidyl ether and styrene oxide reacted with DEAE‐cotton to produce a fabric with twentyfold improvement in resistance to flex abrasion. With 8% aqueous NaOH as an external catalyst, the DEAE‐cotton displayed greater reactivity with all epoxides than did the unmodified fabric. DEAE‐cotton–diepoxide reactions with added base catalyst generally resulted in a decrease in the conditioned recovery angle and an increase in the wet recovery angle. When Zn(BF4)2 was used as an additional catalyst, again the DEAE fabrics displayed the greater reactivity toward the monoepoxides; but the unmodified cotton was more reactive toward the diepoxides than was the DEAE‐cotton. The Zn (BF4)2–monoepoxide‐treated DEAE fabrics had higher wet recovery angles but lower dry recovery angles than the corresponding epoxide‐finished control cottons. Butadiene diepoxide was the only diepoxide investigated which imparted higher dry recovery angles to the DEAE‐cotton than to the unmodified cotton control in the presence of Zn(BF4)2. Tertiary amino groups in DEAE‐cottons act as an internal catalyst for the opening of the oxirane rings, direct the site for reaction in the absence of additional catalysts, and react with some epoxides to form quaternary nitrogen groups.
DTA evidence for physical orientation (crystallinity) in PVC
Authors: McKinney Paul V. , Foltz Carl R. 
Published: April 2003

AbstractA difference has been observed in the DTA and DSC curves for the glass transition of both PVC homopolymer and acetate copolymer, depending on the rate of quenching or annealing below the glass transition temperature. The difference has the appearance of an endothermal peak added to the glass transition curve and is attributed to an alignment of stereoregular chain segments of adjacent polymer molecules. The lengths of chain segments are assumed to be so short that no x‐ray evidence of crystallinity was obtained. The orientation process involved has an activation energy of 47.8 kcal./mole in the homopolymer and 43.6 kcal./mole in the copolymer. The measured rate of the process agrees with the principle of time–temperature superposition, the rates becoming equal for homopolymer and copolymer at equal temperatures below their glass transition temperatures.
Sorption of water vapor by B pattern starch
Authors: Morsi M. K. S. , Sterling C. , Volman D. H. 
Published: April 2003

AbstractWater vapor sorption isotherms of cotton cellulose and B pattern starch preparations, potato starch, corn amylose, amylomaize, and retrograded potato starch, were determined at 5 and 25°C. The crystallinity fraction of these materials equilibrated with water vapor at various partial pressures was determined by x‐ray diffraction. The thermodynamic functions of adsorption were calculated, and B.E.T. constants were determined.
The effect of humidity on the tensile properties of TiO2‐filled poly(vinyl acetate)
Authors: Galperin I. , Arnheim W. 
Published: April 2003

AbstractThe tensile properties of TiO2‐filled poly(vinyl acetate) were studied at strain rates of 100%/min. to 5,000%/min. at 25°C. after exposure to relative humidities of 10, 25, 51, 70, and 90% for 160 hr. Filler concentrations studied were 0, 10, 20, 30, and 40 wt.‐% TiO2. The change in tensile properties with greater humidity was dependent on filler content. As the filler content increased, strength was lowered, elongation increased, and stiffness decreased with greater humidity. Generally, changes in tensile properties with humidity were less pronounced at higher strain rates. A mechanism is proposed where H2O alters the packing of polymer chains and affects the interaction of filler with polymer.
Polyolefin waxes
Authors: Coover H. W. , Combs R. L. , Guillet J. E. , Weemes D. A. 
Published: April 2003

AbstractThe properties of polylefin waxes derived from polypropylene, polybutene, and their copolymers are described, with particular references to those which are useful as coatings and barrier materials. These products can be applied with conventional melt‐ and curtain‐coating machines on paper and other substrates to give coatings with properties comparable to those of extrusion‐coated, plastic‐grade polyolefins. Because of their low melt viscosity and consequent ease of application, they should find wide application in the packaging industry.
Oxidative aging of natural rubber vulcanizates. Part I. The scission of peroxide vulcanizates
Authors: Bell C. L. M. , Tiller R. 
Published: April 2003

AbstractA new method has been developed for measuring the number of molecules of oxygen required (ϵ) to cause a main chain scission in peroxide vulcanizates of natural rubber. This method is based on experimentally derived relationships and is not dependent on statistical theories of rubber elasticity. The value ϵ is only slightly temperature dependent, ranging from 28 at 65°C. to 22 at 100°C. The effects of several types of antioxidant have been examined, in all cases ϵ was greatly reduced. The effect of antioxidant 2246 has been studied in more detail and the results indicate that there is a high probability of scission occurring at the termination step in the oxidation chain.
A microscopic study of fracture in regenerated cellulose film
Authors: Hilyard N. C. 
Published: April 2003

AbstractThe fracture edge of a strip of regenerated cellulose film broken under tension can usually be divided into three regions: (A) the site of the initial failure, (B) the slow‐tear region, and (C) the fast‐tear region. Photomicrographs showing these regions are presented and discussed. Three different types of initial failure are described and some data presented relating the breaking strain to the type of initial failure.
Aliphatic heterocyclic polymers
Authors: Trischler Floyd D. , Kjoller Kendall J. , Levine Harold H. 
Published: April 2003

AbstractAliphatic polybenzoxazoles, polybenzothiazoles, and polybenzimidazoles have been prepared by three methods: in poly(phosphoric acid), by the polyamide precursor, and by melt polymerization. The melt polymerization method was found to be the most satisfactory. All of the aliphatic heterocyclic polymers had excellent thermal stability, resistance to alkaline hydrolysis, high glass transition temperatures, and a high degree of flexibility. The only class of polymer found having any degree of solubility, however, was the polybenzimidazoles. Aliphatic polybenzimidazole films were prepared by solution casting. These films were found to be extremely flexible at ambient and cryogenic temperatures. The films were unaffected by alkaline hydrolysis, even in an oxidizing medium. A molding prepared from the aliphatic polybenzimidazole had excellent physical properties at both cryogenic and room temperature.
Kinetics of heterogeneous cellulose reactions. II. Reaction with propionyl chloride
Authors: Chatterjee Pronoy K. , Conrad Carl M. 
Published: April 2003

AbstractA heterogeneous cellulose reaction was studied by reacting cotton fiber in pyridine medium with propionyl chloride at different initial molar concentrations and at different temperatures. It has been observed that the kinetics of reaction does not follow Sakurada's diffusion equation closely, and the deviation is more noticeable at lower initial concentrations of the reagent and at lower temperatures. A non‐uniform reaction rate is also evident from the time–substitution curve. The rate of substitution changes twice during the reaction, the latter change being associated with the loss of cellulose I crystal structure. In an attempt to treat the data according to simple chemical kinetics, the order has been found to decrease continuously from the beginning, suggesting thereby an autocatalytic type of behavior. However, at the finàl stages of the reaction, when the cellulose I structure was completely lost, the reaction behaved as a pseudo first‐order type. The x‐ray diffractograms of the reacted samples indicate that cellulose I crystallinity decreases from the beginning of the reaction and that a new crystalline lattice develops gradually. The formation of this new crystal lattice is hindered in the cellulose crystalline region due to the lack of freedom of the chains. The diffusion equation has been modified by substituting a crystallinity index for the rate of diffusion of solvent in a solvent–gel system and thus extending Sakurada's equation. A new mechanism has been proposed considering the simultaneous reactions in the amorphous and crystalline regions. This mechanism can explain the deviation of Sakurada's equation. The kinetics expressions are derived, based on the proposed mechanism. The kinetics of decrystallization of cellulose I is also presented. A satisfactory theoretical explanation is given for the fact that the fall of reaction rate occurs at the conclusion of decrystallization of the cellulose I structure.
Practical evaluation of the [η]–M relationship. II. Estimation of Kθ values of polymer solutions
Authors: Van Krevelen D. W. , Hoftyzer P. J. 
Published: April 2003

AbstractA method is proposed for the prediction of the intrinsic viscosity of θ solutions, based upon the constitution of the dissolved polymer. The method makes use of additive values for constitutional groups to calculate a quantity that represents the specific chain stiffness per main chain atom.
Basic gel‐permeation chromatography studies. I. Polymer degradation
Authors: Hendrickson J. G. 
Published: April 2003

AbstractPolymer degradation has been studied by using gel‐permeation chromatography (GPC) to measure the product distribution. The method is rapid and has a good accuracy that permits one to see most of the degradation products, as they elute at a point different from the starting material. In the cases studied, polystyrene cleavage has the result of random cleavage, as judged by the product distribution. A GPC curve to be expected from random cleavage has been put together to aid in the evaluation. Both wide and narrow molecular weight distribution polystyrenes have been studied after degradation. The narrow distribution products were degraded by peroxides, irradiation, and weathering. With the latter, the combination of simple fragments to form the starting portions of cromslinking were measured in small amounts. In none of the cases studied did degradation in solution produce crosslinked products. Kinetic rate studies were made that concerned the action of peroxides and inhibitors.
Phosphorus derivatives of methyl 2‐(chloromethyl)acrylate
Authors: Sherr Allan E. , Klein Harvey G. 
Published: April 2003

AbstractSeveral phosphorus derivatives of methyl 2‐(chloromethyl)acrylate, including three phosphonium salts and one phosphonate ester have been prepared. A brief study was made of their polymerization characteristics under free‐radical conditions. Several factors were noted which prevented the synthesis of methyl 2‐[(diethoxyphosphinyl)‐methyl]acrylate in high yields in initial experiments. Homopolymerization of these phosphorus derivatives does not take place readily in the presence of free‐radical initiators.
Surface treatment of polymers for adhesive bonding
Authors: Schonhorn H. , Hansen R. H. 
Published: April 2003

AbstractFurther studies of a new and highly effective method for the surface treatment of low surface energy polymers for adhesive bonding are reported. Mechanisms are suggested for the increase in the cohesive strength in the surface region of polyethylene when it is exposed to activated species of inert gases. The technique is unique because, in contrast with results obtained with other methods, bulk properties of the polymer such as color or tensile strength and elongation are unaffected and surface properties such as wettability and dielectric properties such as surface conductivity are essentially unchanged.
Effect of water on the mechanism of deformation of nylon 6
Authors: Boukal Ivo 
Published: April 2003

AbstractLattice spacings perpendicular to the molecular chain axes and crystallite orientation of dried and moist (boiled in water) bulk nylon 6 were determined by x‐ray diffraction under tension of 30–300 kg./cm.2. The deformation of the specimen was also measured. The lattice spacings are changed reversibly by the presence of water in nylon 6, but the elastic moduli of the lattice are not affected. The lattice elastic modulus in the direction of the hydrogen bonds is approximately double its value in the direction normal to the hydrogen bonds. The elastic modulus of the dried nylon 6 approaches the value of the lattice elastic modulus in the direction normal to the molecular axes, while the modulus of the moist nylon 6 is several times lower. From these facts, and especially from the relations between the lattice deformation, crystallite orientation, and specimen deformation, the principal differences in the deformation mechanism of dried and moist nylon 6 were deduced. The results obtained have also made possible some general conclusions about the crystalline structure of nylon 6 and the deformation mechanism of linear polymers.
Graft copolymerization onto protein by the ceric ion method. Studies on grafting site
Authors: Imai Yohji , Iwakura Yoshio 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate and acrylamide onto ovalbumin was carried out with redox system with ceric ion. Initiation of grafting occurred very rapidly, and the number of grafting sites reached a maximum after about 2 min. regardless of initial ceric ion concentration. The grafted polymer chains were separated by selective hydrolysis of the protein backbone with hydrochloric acid or protease in order to characterize the graft copolymers. The grafted polyacrylamide separated by the proteolytic digestion contained a carbohydrate residue at the end of the polymer molecule. The problem of grafting sites on ovalbumin is discussed.
Bonding polyethylene to metals
Authors: Vincent G. G. 
Published: April 2003

AbstractA process for adhering polyethylene to aluminum was developed which involves treating the aluminium substrate successively with chromic acid and then a selected organic acid. Certain organic acids utilized in this process appeared to produce a synergistic effect on the adhesion. This process, which required no modification or treatment of the polymer, resulted in peel strengths forty times greater than that obtained on untreated aluminum. Tensile shear values for the polyethylene–aluminum bond were greater than 2800 psi. The materials used for treating the metal in this system produced a maximum in the obtainable peel strength. Furthermore, minor changes in the etching acids resulted in drastic changes in the adhesion values.
The effect of thermal pretreatment on the strength of polycarbonate
Authors: Golden J. H. , Hammant B. L. , Hazell E. A. 
Published: April 2003

AbstractThe 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.
Determination of rates of thermal decomposition of polymerization initiators with a differential scanning calorimeter
Authors: Barrett K. E. J. 
Published: April 2003

AbstractA 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.
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

AbstractThe 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

AbstractThe 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.