bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and polymerization of tris(alkylamino)‐silance with epoxy prepolymers
Authors: Bilow N. , Murphy R. F. , Patterson W. J. 
Published: April 2003

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

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

AbstractCellulose acetate reverse osmosis membranes, 600–2800 A. thick, have been prepared on glass surfaces by dipping a clean glass plate into a dilute solution of cellulose acetate. After drying, the membranes are floated of onto a water surface and placed on molecular filter supports. Theoretical salt rejections, as calculated from the solution‐diffusion model of membrane transport for cellulose acetate, were obtained with imperfection‐free membranes.
Oxidative aging of natural rubber vulcanizates. Part II. Effect of vulcanizate structure
Authors: Bell C. L. M. , Cunneen J. I. 
Published: April 2003

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

AbstractUnsaturated polyester resins containing water were prepared through two steps: formation of a stable W/O emulsion of polyester prepolymer and subsequent polymerization of the emulsion. In this paper, conditions for formation of the resins from the W/O type emulsion and the heat‐protection properties of the resulting water‐containing resins are reported. The stability of the emulsions was measured, and the results are discussed in relation to the gelation time, since the polymerization of the emulsions is required to proceed faster than their disintegration. It was found that with increasing viscosity of the emulsions their stability increases and the gelation time shortens. The above requirement is fulfilled at almost all regions of emulsifier concentration where stable W/O emulsions are formed. Water‐containing unsaturated polyester resins exhibit a remarkable heat‐protection effect at elevated temperatures (500 and 2500°C.) in comparison with polyester resins not containing water.
Aminobutadienes. XII. A method for modification of polypropylene fiber by graft copolymerization with 1‐phthalimido‐1,3‐butadiene by thermal mastication
Authors: Terada Akira 
Published: April 2003

AbstractThe high reactivity of 1‐phthalimido‐1,3‐butadiene for either homopolymerization or copolymerization was applied to prepare a graft copolymer with isotactic polypropylene using a roll mill. Five reaction systems containing the monomer 0, 1, 3, 5 and 10% in polypropylene were allowed to react at 175°C. under atmospheric pressure for 10 min. to give the graft copolymers. The resulting resin, tough and rigid, was melt‐spun to give a single filament. This filament was extracted with 1,2‐dichloroethane to remove the remaining monomer and homopolymer. The percentage of the grafted monomer against the feed was determined by ultraviolet spectroscopy. This modified method did not result in gel formation or decreased viscosity. Accordingly, spinning could be easily carried out. After fivefold stretching of the filament in hot water of 95°C., the tensile strength was almost identical to that of a sample obtained from the original polypropylene. However, a considerable decrease in elongation was observed. The filament can be dyed uniformly with some basic dyes at a rate proportional to the imidobutadiene contents. After hydrazinolysis, the filament acts as an anion‐exchange fiber and imbibes acid dyes homogeneously throughout.
Intrinsic viscosity of polymer solutions at high shear rates
Authors: Ram A. , Siegman A. 
Published: April 2003

AbstractAlthough low‐shear intrinsic viscosity is a well‐accepted tool for polymer characterization, it often happens (particularly with increasing molecular weights) that it is easier to detect the high‐shear (second) Newtonian viscosity η2 rather than its low shear counterpart. It has also been predicted that because of a higher degree of order, due to disentanglement and orientation, high‐shear viscosity data should simplify the prevailing correlations. The possibility of using high‐shear viscometric data for polymer characterization was examined by determining intrinsic viscosities for several polyisobutylene samples through extrapolation of the high‐shear ultimate viscosity numbers, UVN, to zero concentration: [η]2 = lim UVNC → 0 = limC → 0 (η2–ηs)/ηsC where ηs is the viscosity of the pure solvent. Five samples of unfractionated polyisobutylene (molecular weights of 1.1 × 106–6.6 × 106) in toluene, kerosene, decalin, and gas oil at concentrations of 0.05–2.4 g./dl. were studied. Higher dilution was avoided because of the problem of onset of turbulence. The absence of shear degradation was ascertained by measuring low‐shear intrinsic viscosity data before and after the polymer was exposed to high‐shear conditions. The data show two types of behavior: for the lower molecular weight samples in the low‐viscosity solvents the UVN decreases linearly with dilution, and for the higher molecular weights and higher solvent viscosities the UVN increases with high dilution, i.e., shows an upturn effect. The first type of data can be successfully correlated with appropriate molecular weights by using a typical Mark‐Houwink equation. The exponents in these relationships are in the range of 0.28–0.64, increasing systematically with decrease of solvent viscosity and independent of the “goodness” of the latter. The data that show an upturn effect are not currently amenable to reliable extrapolation techniques. The upturn, however, predicts the conformation of very flexible, isolated polymer chains in viscous solvents under conditions of high shear.