bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incremental modification of styrene‐butadiene rubber with tert‐nonyl mercaptan
Authors: Uraneck C. A. , Burleigh J. E. 
Published: April 2003

AbstractA model equation derived for the viscosity‐average degree of polymerization (P̄v) for the incremental addition of modifiers, P̄v = K{(exp{arx1} − 1) + [2/(2 + exp {x1r})]a(exp{arx2} − exp{arx1})}1/a indicates a minimum should occur in a curve of P̄v versus conversion at which the increments are added, x1. Incremental addition of commercial tert‐dodecyl mercaptan in the laboratory to SBR recipes at 5°C. showed effects contrary to those predicted by the model equation, but incremental addition experiments with tert‐nonyl mercaptans resulted in a minimum in viscosity versus x1 curves, changed the molecular weight distribution, and required 34 wt.‐% less mercaptan than did the tert‐dodecyl mercaptan control (all the tert‐dodecyl mercaptan added initially). Incremental addition of tert‐nonylmercaptan in pilot plant 20‐gal. autoclave reactors gave essentially the same results found in the laboratory bottle experiments. The stress‐strain and mixing properties of the incrementally modified polymer and the tert‐dodecyl mercaptanmodified control were essentially the same within experimental error. Conditions required for successful application of the incremental modifier technique are given.
Thermoplasticity of acetylated cotton yarn as influenced by degree of substitution, temperature, and other factors
Authors: Creely J. J. , Harbrink P. , Conrad C. M. 
Published: April 2003

AbstractThe relative degree of thermoplasticity of acetylated cotton yarns has been determined by a technique developed for the purpose. The interfering contribution of hydrogen bonding could be eliminated by a wetting‐out process. The yarns were acetylated to degrees of substitutions ranging from 0.77 to 2.93. Heat setting was applied either in vacuum or at atmospheric pressure in the presence of water vapor at temperatures in the range of 110–225°C. The thermoplasticity observed over a period of 30 days was permanent but readily removable by another application of heat setting. The effect of degree of substitution upon thermoplasticity could be represented by sigmoidal curves beginning at about DS = 1 and increasing rapidly and asymptotically to a maximum at about DS = 2.25. In vacuum or water vapor the maximum thermoplastic response occurred at 175°C., but the response was greater with water vapor. Under vacuum heating a very distinct minimum response occurs at 180°C., due to second‐order transition effect. Upon heating in the presence of water vapor a distinct minimum response occurs at 200°C. with secondary minima at 150 and 120°C. Prior crystallization (by heating to 200–225°C.) greatly reduces thermoplasticity due to reduction of the amorphous component, but does not completely eliminate it.
Effects of aging on some anionic initiators
Authors: Ladacki Michael 
Published: April 2003

AbstractThe effects of aging on sodium naphthalene and sodium α‐methylstyrene initiators, prepared in 1957, were investigated. The green sodium naphthalene had turned brown and faded; the aged sample failed to initiate the polymerization of α‐methylstyrene at low temperature. Naphthalene had been completely converted into dihydronaphthalene; the retention of the brown color reflected a relative stability of anions of the latter. The freshly prepared brown sodium‐dihydronaphthalene complex was also ineffective for polymerization of α‐methylstyrene. No evidence for the cleavage of the ether solvent (tetrahydrofuran) on aging was obtained. The aged sodium α‐methylstyrene initiator retained its vivid red color and effectiveness in the polymerization of α‐methylstyrene. The inherent better stability of dianions than of radical anions was thus confirmed. Since the sodium α‐methylstyrene initiator was actually a low molecular weight “living” polymer, the 7‐yr. aging test demonstrated, in effect, the “longevity” of living polymers. The structure of the “living tetramer” of α‐methylstyrene was discussed in the light of previous studies and present results. Apparent discrepancies were pointed out, and the necessity of more comprehensive studies was indicated.
Variable retention of water by dry wood
Authors: Hergt H. F. A. , Christensen G. N. 
Published: April 2003

AbstractWhen small wood (or cellulose) samples are vacuum‐dried at room temperature, their final weight is found to vary according to their previous sorption history. The weight variations, of up to 1%, are shown to be due to strongly retained water. A minimum weight is obtained reproducibly (± 0.01%) only when the wood is dried rapidly from the wetted state. When wood thus dried is exposed to water vapor and redried, water is retained even after drying for long periods or at higher temperatures (65°C.) and is removed only by again wetting and redrying the wood. The quantity of water retained is greatest after exposure to relative vapor pressures of approximately 0.5 and increases linearly with the square root of time of exposure up to at least 1000 hr. As some of these phenomena have been reported for the wool–water system also, it is possible that other polymers, particularly those which swell in water, may behave similarly. The significance of these results for the experimental determination of moisture content and the study of water sorption is discussed.
Intramolecular transfer of high energy in cellulose
Authors: Arthur Jett C. , Mares Trinidad 
Published: April 2003

AbstractThe intramolecular transfer of high energy in purified cotton cellulose has been demonstrated to occur over distances several times greater than the length of the b axis of a cellobiose unit. The electron spin resonance spectra of fibrous benzoylated cotton cellulose have shown that the concentrations of free radicals initiated in the cellulosic molecule by γ‐radiation from Co60 are decreased by the presence of substituted benzoyl groups spaced at least as far apart as 70–80 A. The retention of the breaking strength of fibrous cotton cellulose on exposure to γ‐radiation is increased by substitution of benzoyl groups on the cellulose molecule. The substitution of benzoyl groups, spaced at least as far apart as 10–20 A., results in about 80% retention of the initial strength of the fibrous cellulose at dosages as high as 1.3 × 1021 e.v./g. cellulose, as compared with about 20% retention of the initial strength of unsubstituted cellulose at the same dosage. Based on the breaking strengths of the irradiated fibrous celluloses, at a dosage of 1.3 × 1021 e.v./g. cellulose, the average calculated distances between molecular cleavages are increased from about 500 A. for unsubstituted cellulose to about 3000 A. for benzoylated cellulose (degree of substitution 2.0). These energy transfer effects in cellulose of high molecular weight indicate that polymeric carbohydrates can be radioprotected.
Crystallinity of ethylene–vinyl acetate copolymers
Authors: Kamath Pandurang M. , Wakefield Robert W. 
Published: April 2003

AbstractDetermination of crystallinity of ethylene–vinyl acetate copolymers according to the usual x‐ray diffraction method employed for polyethylene is very much hampered by the fact that these copolymers are usually largely amorphous and the Bragg reflections in their diffraction diagrams which are therefore broad and weak are drowned by the strong and dominant amorphous halo. As a consequence it is virtually impossible to carry out a realistic resolution of the total diffraction diagram into the individual Bragg reflections in the halo. In the method described in this paper this difficulty is successfully surmounted by taking advantage of the unique shape and placement of the amorphous halo with respect to the Bragg reflections in the diffraction diagrams of these copolymers. This rather fortunate situation permits a direct determination of amorphous content without having to take recourse to the cumbersome resolution of the Bragg reflections and hence one can obtain crystallinity indirectly.
Effect of zinc oxide concentration on the course of thiuram‐accelerated sulfur vulcanization
Authors: Ducháček Vratislav 
Published: April 2003

AbstractTetramethylthiuram disulfide‐accelerated sulfur vulcanization of natural rubber has been investigated. Continuous measurements in a Vuremo curemeter at 145°C were used to estimate the effects of zinc oxide concentration on the induction periods, on the first‐order rate constants, and on the ultimate extents of crosslinking, on the extents of degradation reaction (reversion), and on the extents of relaxation of vulcanizates at the cure temperature. The concentration of zinc oxide has practically no influence on the rate of thiuram‐accelerated sulfur cure. The values of the ultimate extents of crosslinking increase with increasing the zinc oxide content in the rubber compound up to a certain limit corresponding to the theoretical amount of zinc oxide which is necessary for the formation of zinc dimethyldithiocarbamate from tetramethylthiuram disulfide and zinc oxide during the vulcanization reaction. From the point of view of the reversion, however, this limit value of zinc oxide concentration is not sufficient. The relaxation measurements provide the same results. On the basis of these, for thiuram‐accelerated sulfur vulcanizations, the optimum zinc oxide content in the rubber mix of 2.5 phr has been calculated. This value is in very good agreement with the optimum value of zinc oxide concentration found for both sulfenamides and thiazoles‐accelerated sulfur cures.
The effect of competitive adsorption on the rate of diffusion
Authors: Hemming David F. , Collins John D. , Datyner Arved 
Published: April 2003

AbstractEvidence is presented that the apparent diffusion coefficient of one penetrant can be increased by competition from another penetrant for the same adsorption sites in polyester. The competition is governed by the relative diffusivities of the penetrants and their affinities for the adsorption sites.
Thermal degradation of polymers. XII. Synthesis, polymerization and thermal characterization of polymers of m‐N,N‐dimethylaminostyrene in nitrogen
Authors: Opera S. , Still R. H. 
Published: April 2003

AbstractThe monomer m‐N,N‐dimethylaminostyrene has been synthesized from acetophenone and homopolymerized and copolymerized with styrene, using 2,2′‐azobisisobutyronitrile as free‐radical initiator. The polymers have been characterized by thermal analysis (DTA, DSC, and TG). Glass transition temperatures have been measured and activation energies for degradation in nitrogen have been established by a variety of methods for comparative purposes.
The photochemistry of 1‐benzoyl‐2‐naphthol and 6‐hydroxybenzanthrone and their effect on the rate of photo‐oxidation of polypropylene
Authors: Bentley P. , McKellar J. F. 
Published: April 2003

AbstractA comparison of the effect of two structurally similar additives, 1‐benzoyl‐2‐naphthol and 6‐hydroxybenzanthrone, on the rate of photo‐oxidation of polypropylene under conditions of simulated daylight shows that while 6‐hydroxybenzanthrone acts as a prodegradant, 1‐benzoyl‐2‐naphthol is a light stabilizer. Examination of the spectroscopic and photochemical properties of 1‐benzoyl‐2‐naphthol indicates that in fluid solution the photoexcited stabilizer is probably deactivated within the singlet manifold. In glassy solvents at 77°K, on the other hand, triplet formation does occur, but only in molecules in which the intermolecular hydrogen bond of the 1‐benzoyl‐2‐naphthol is disrupted.
Effect of four neighboring groups in kinetics of polymer reactions
Authors: Krishnaswami P. , Yadav D. P. 
Published: April 2003

AbstractAssuming that the rate of reaction of an unreacted site in polymer reactions depends upon whether the two immediate neighboring sites on either side (four neighboring sites in all) are reacted or unreacted, differential equations were obtained giving the rate of change of Nn with time (where Nn is the number of sequences of n consecutive unreacted sites with a reacted site at both ends) and solved numerically with the help of a computer. Nn was obtained as a function of time and also as a function of M, the total number of unreacted sites. Three sets of values of k were tried, one of these relating to autocatalytic reaction, one to autoretarding reaction, and one to the null case in which the reaction rates do not depend upon the neighbors.
Transitions and relaxations of linear polyesters related to poly(ethylene terephthalate). I. Melting
Authors: Yip Harry K. , Williams H. Leverne 
Published: April 2003

AbstractObservations obtained by other techniques were confirmed by DSC analyses. As the length of the methylene chain increased, Tm decreased, and crystallinity, heat capacity, and heat of fusion increased. The Tm and crystallinity of the isophthalate esters were lower than for the corresponding terephthalate esters. The values for an odd‐numbered methylene sequence were lower than for the adjacent even‐numbered members. A model was used to calculate the heat of fusion of theoretically 100% crystalline poly(hexamethylene isophthalate) and poly(decamethylene isophthalate).
The Tll (>Tg) transition of atactic polystyrene
Authors: Stadnicki S. J. , Gillham J. K. , Boyer R. F. 
Published: April 2003

AbstractTorsional braid analysis (TBA) (∼0.3 Hz) and differential thermal analysis (DTA) data are presented for the temperature for the region 0–200°C for two series of atactic polystyrenes with narrow molecular weight distributions: (a) anionic series, M̄n = 600–2×106, M̄w/M̄n ≃ 1.1; (b) fractionated thermal series, M̄n = 2,000–1.1×105, M̄w/M̄n < 1.25. Preliminary results on bimodal blends are also reported. Heating and cooling cycles were employed with TBA; only the heating mode was used with DTA. In addition to a dynamic mechanical loss peak at Tg, a higher temperature loss peak was also found. Designated the Tll or liquid–liquid transition (relaxation), its temperature is 1.1 to 1.2 Tg (°K) for polymers with molecular weight below the critical molecular weight (Mc) for chain entanglements. Above Mc ≃ 35,000, it rises steeply, being ≃200°C for M̄n = 110,000. The common dependence of Tg and Tll on M̄n−1 below Mc suggests a common molecular origin. The two facts, (a) that Tll > Tg and (b) that Tll reflects chain entanglements, further suggest that Tll involves a longer chain segment length and possibly the entire molecule. Comparison of Tll versus log M plots with T versus log M isoviscous state plots based on zero‐shear melt viscosity data from the literature implies that Tll measured by the TBA technique corresponds to an isoviscous state of 104–105 poises. The employment of narrow molecular weight polymers is presumably responsible for both the linear variation of the Tll transition with M̄n−1 (which suggests a free volume basis for the relaxation) and the form of the variation of the Tll transition with log M (which suggests an isoviscous basis for the relaxation). The sharpness of the Tll loss peak by TBA decreases with increasing molecular weight and dispersity. The DTA endothermic event corresponding to Tll is clearly related to the occurrence of flow since the fused films which result from heating granules to 200°C and cooling to R.T. do not reveal a Tll on reheating. If a fused film is crushed, a Tll event is observed on heating. For bimodal blends with M̄n < Mc for both components, the Tll transition was averaged; with one component less than and one greater than Mc, the Tll transitions of the components appeared to occur independently at temperatures corresponding to those of the isolated components. In accordance with Ueberreiter and Orthmann, Tg appears to separate a glassy state from a fixed liquid state, whereas Tll separates the fixed liquid from a true liquid state. Possible molecular interpretations for the Tll process are discussed. Systematic bodies of data from the literature which indicate the presence of the Tll process in other polymers are summarized.
Photopolymerization of methyl methacrylate in the presence of saccharide
Authors: Kubota Hitoshi , Ogiwara Yoshitaka , Matsuzaki Kei 
Published: April 2003

AbstractPhotopolymerization of methyl methacrylate (MMA) in aqueous solution of saccharide was investigated. Glucose, cellobiose, maltose, and fructose accelerated the photopolymerization in the hard glass system, but α‐methyl‐d‐glucoside was inactive. On the other hand, on remarkable effect of saccharide except fructose was observed in the quartz glass system. A conversion in the hard glass system increased with irradiation time and with concentration of saccharide, which showed the effect in the order of ketose > aldose > nonreducing saccharide. Scission of glucosidic bonds and decomposition of reducing groups of saccharide molecule took place in the quartz glass system, but there was no reduction in the reducing power of saccharide in the hard glass system. By studying the ESR of the photoirradiated system containing saccharide, MMA, and water, no radical of saccharide was found in hard glass systems, but an increase in growing radical of MMA was clearly observed in systems with the coexistence of ketose and aldose, while α‐methyl‐d‐glucoside was inactive. It is believed, therefore, that both ketose and aldose contribute effectively to initiate the photopolymerization without any change in their own structures. On the other hand, reducing groups of saccharide play a very important role in the sensitizing action of the initiation.
Deuteration of cotton fibers. I. Partially decrystallized celluloses
Authors: Lokhande H. T. 
Published: April 2003

AbstractDeuteration of cellulose in the fiber form has been studied by the new technique developed recently. Infrared spectra in the 3‐μ region were recorded to obtain four well‐resolved bands due to H‐bonded hydroxyl groups in the ordered regions. The peaks at 3298 and 3400 cm−1 were assigned to cellulose I, while those at 3445 and 3493 cm−1 were assigned to the cellulose II lattice structure. Cotton fibers containing both cellulose I and cellulose II lattice structures (50:50%) gave six bands in the 3‐μ region at 3230, 3298, 3350, 3400, 3445, and 3493 cm−1. Deuteration of swollen and decrystallized cotton fibers revealed that ethylenediamine brings about partial conversion of cellolose I lattice structure to cellulose II lattice structure, giving the characteristic cellulose II band at 3493 cm−1. Swelling mechanism with ethylenediamine to account for formation of cellulose II in cotton fibers has been put forward. Zinc chloride was found to retain the cellulose I structure intact. In both the decrystallized celluloses, the band at 3400 cm−1 has been found to be completely wiped out. This band has been assigned to the group of H bonds mainly lying in rather imperfectly ordered crystalline regions in the fiber structure, which are attacked first during swelling treatment by both the swelling agents irrespective of their different mechanisms of swelling.
Polyimide model compounds
Authors: Hodgkin J. H. 
Published: April 2003

AbstractPyromellitic dianhydride was reacted with various substituted aryl amines, under conditions similar to those used for polyimide formation. Yields of model imides have been greatly improved over those found in previous studies. The work has shown that the major impurities formed when the reactions were performed in solutions of N,N‐dimethylformamide or N,N‐dimethylacetamide were adducts containing chemically bound solvent residues.
Electroinitiated polymerization of methyl methacrylate in aqueous sulfuric acid
Authors: Pistoia Gianfranco , Ricci Alessandro , Voso Maria Antonietta 
Published: April 2003

AbstractThe polymerization of methyl methacrylate electroinitiated at the cathode was examined in concentrated solutions of the monomer containing aqueous sulfuric acid. The initiating reaction is not due to the formation of hydrogen atoms, as demonstrated by varying the nature of the cathode and of the acid, but involves the participation of the polymeric peroxide contained in the monomer. The cathodic material greatly affects the molecular weights and the yields, as does the composition of the solutions. Lead cathodes, which proved to be particularly efficient, showed phenomena of adsorption of both monomer and polymer. Kinetic curves are similar to those obtained in conventional radical polymerizations of MMA; a marked gel effect, limiting the termination reaction and leading to very high molecular weights, was observed.
Kinetics of the acid‐catalyzed phenol–formaldehyde reaction
Authors: Malhotra H. C. , Avinash  
Published: April 2003

AbstractA kinetic study of the reaction of phenol with formaldehyde has been carried out at temperatures of 65° ± 0.05°C, 70° ± 0.05°C, 75° ± 0.05°C, and 80° ± 0.05°C using hydrochloric acid as catalyst. The pH maintained was 1.14, 1.32, 2.20, and 3.00. The reaction follows a second‐order rate law. The rate is found to increase with decrease in pH. The overall rate constants are resolved into step rate constants. The values of the Arrhenius parameters and the entropy of activation for the overall reaction as well as for the step reactions have been calculated. A mechanism conforming to the energies and entropies of activation of the reaction has also been suggested.
Conversion factors in dilatometric data of polymerization reactions
Authors: Adicoff A. , Yee R. 
Published: April 2003

AbstractVarious factors in the conversion of dilatometric data to the extent of polymerization have been considered. These factors are volume additivity, density additivity, difference between the thermal coefficients of monomer and polymer, molecular weight, and degree of crosslinkage. Equations relating the dilatometric readings to the extent of polymerization have been derived. These equations can be used for reactions where the polymerization may be stopped short of complete polymerization. They can also be used for polymerization where the initial portion of the reaction is difficult to record.
Plumbite‐treated cotton in formation of glassy materials
Authors: Ward Truman L. , Benerito Ruth R. 
Published: April 2003

AbstractGlass‐like materials containing carbon were produced by heating plumbite‐treated cotton fabrics in a limited oxygen atmosphere while in contact with a surface having a high silica content. Although the new materials were changed to a clear glassy state, they retained the design and shape of the fabric weave and were hard, brittle, acid resistant, and alkali resistant. Surface smoothness of the new materials and release from the high silicon‐content materials on which they were made depended on lead content of the plumbite‐treated cotton fabric. High lead contents produced smoother surfaces and better release. This information was applied in producing glass‐like write‐on labels for laboratory glassware or individual flakes of the new material. Direct heat from a Bunsen‐type burner caused the new glass‐like materials to become metallic gold in color without altering other properties. Indirect heat reversed the color to the original. ESCA and x‐ray fluorescence examinations showed the atom ratio of lead to silicon to be 2.5:1 for those made from high lead‐content fabric. Substantial carbon was present in all lead levels.