bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinking of silk fibroin by aqueous peroxydisulfate
Authors: Needles H. L. 
Published: April 2003

AbstractSilk fibroin is crosslinked by 0.1–1.0M ammonium peroxydisulfate at 70°C. or at 40°C. in the presence of silver ion. Induced decomposition of peroxydisulfate in the presence of fibroin is observed. Methylation of tyrosine in fibroin does not slow attack by peroxydisulfate, but crosslinking of the fibroin is prevented. Modification of tryptophan with α‐bromo‐5‐nitro‐2‐cresol does not prevent crosslinking by peroxydisulfate, however. The nature and sites of crosslinking in fibroin are suggested in light of physical and chemical data, amino acid analyses of crosslinked and control fibroins, and the known mode of decomposition of peroxydisulfate.
Study of the nitration of methyl cellulose
Authors: Bobinski Jack , Carignan Yvon P. 
Published: April 2003

AbstractA two‐step procedure for the preparation of methyl cellulose nitrate is described. The heterogeneity of the methylation step is reflected in the nonuniformity of the products obtained by nitration with either 98% nitric acid or a solution of 98% nitric acid in methylene chloride. On the basis of the experimental data it is calculated that methyl cellulose having a minimum degree of substitution of 1.8 is required for the preparation of a uniformly substituted methyl cellulose nitrate.
Ionic graft copolymerization. II. Graft copolymerization of β‐propiolactone onto acrylonitrile–sodium acrylate copolymer
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro 
Published: April 2003

AbstractPolyacrylonitrile–β‐propiolactone (βPL) graft copolymer was synthesized by means of ionic polymerization, in which polymerization of βPL was initiated by polyacrylonitrile containing a small amount of some reactive groups such as COOK, COONa, COOLi, and COOH. Lower electronegativity of the countercation favored higher total conversion and higher grafting percentage. The grafting percentage increased with the reaction time and concentration of reactive groups in the trunk polymer, but grafting efficiency varied very little under these conditions. In the bulk polymerization at 60°C., grafting efficiency was about 60%, but in the solution polymerization in toluene or dioxane, grafting efficiency was higher than in bulk or nitrobenzene.
Polyisocyanurate adhesives
Authors: Sandler Stanley R. 
Published: April 2003

AbstractThe preparation of polyisocyanurates by the polytrimerization of isocyanate prepolymers in the presence of organometallic catalysts leads to an increase in adhesive strength at 400°F. for bonding aluminum‐to‐aluminum. The trimerization efficiency of several other catalysts is briefly described.
Study of radiation‐induced graft polymerization of vinyl monomers to cellulose by infrared spectroscopy. I. Cellulose–polyacrylonitrile copolymers
Authors: Imrišová D. , Maryška S. 
Published: April 2003

AbstractInfrared spectral analysis has been applied for the study of cotton–polyacrylonitrile copolymers prepared by using the preirradiation method. The degree of grafting was determined from the absorption at 2249 cm.−1, which is characteristic of the polyacrylonitrile spectrum, with an accuracy of ± 1.5%.
Investigation by electron microscopy and x‐ray diffraction of the microstructure of permselective membranes made from polyethylene
Authors: De Körösy F. , Zeigerson E. 
Published: April 2003

AbstractIon‐permselective membranes containing polyethylene in their base material have been examined by direct transmission electron micrography and x‐ray diffraction. All of the electron micrographs showed white lines of about 100 A. thickness between somewhat thinner black lines composed of granules. These lines often occur as black‐white‐black triplets. We tentatively explain these structural elements by assuming that they are cross sections of the crystallite platelets, characteristic for polyethylene, reacted on both of their faces during sulfochlorination. It is known, that these platelets are about 100 A. thick, X‐ray diffraction experiments also showed the characteristic lines of polyethylene crystallites, their intensity decreasing after sulfonation. The velocity of heterogeneous sulfochlorination of polyethylene sheets decreases abruptly when the film contains 6% S and 7% Cl (after hydrolysis). This m̀eans six substituted sites on a chain element across the platelet for a 100% crystalline film and accordingly less for a partially amorphous material. It is known that five CH2 groups of each chain element are exposed at the surface of the platelets, in good agreement with our findings.
Fatigue under complicated load histories. Law of cumulative damage
Authors: Prevorsek Dusan C. , Brooks Michael L. 
Published: April 2003

AbstractThe applicability of Miner's law of cumulative damage to predict lifetimes in experiments involving complex load histories is examined. Lifetimes estimated by Σ ti/(tb)i = 1 are compared with those calculated by the expression for the time to rupture derived by Prevorsek and Lyons assuming that the time to rupture can be approximated by the time to form an unstable crack. For experiments in which the loading conditions became increasingly severe with time, lifetimes predicted by Miner's law are longer than those calculated from the rate of crack propagation, the opposite being found for experiments in which the loading conditions become decreasingly severe with time. Experimental data on hand are in agreement with these findings. Effects of changes in the structural parameters ρ, E, and ΔF* and of variations in the experimental conditions on the accuracy of the lifetime estimates are discussed.
Macrostructure and environment‐influenced surface layer in epoxy polymers
Authors: Cuthrell R. E. 
Published: April 2003

AbstractSeveral epoxy polymers were shown to be two‐phase systems; roughly spherical floccules arranged in layers in an interstitial fluid resembling the starting materials. The size of the floccules was found to be dependent on the initial rate of cure of a given polymer. The density, hardness, glass transition temperature, etching rate, and dielectric strength were related to the floccule size. The surface layer in the epoxy polymers and in several thermoplastic polymers was found to be different from the bulk material. The properties of the surface layer are dependent on the surface energy of the mold material and on the atmospheric environment. A gradient in properties was found to extend from the polymer surface several hundred microns into the bulk.
Transitions of polytetrafluoroethylene at about 90 and 130°C. studied by x‐ray diffraction and infrared spectra
Authors: Araki Yoshio 
Published: April 2003

AbstractBy means of x‐ray diffraction, the lattice spacing of the (100) plane for molded polytetrafluoroethylene was measured at different temperatures from 25 to 190°C. In the crystalline region, the linear expansion coefficient, in the direction perpendicular to the molecular chain axis, was obtained as 1.1 × 10−4°C.−1 below 60°C., as 1.2 × 10−4°C.−1 above 90°C., and as a minimum value of some 0.2 × 10−4°C.−1 at about 80°C. As the linear expansion coefficient of the crystalline region in bulk was observed as some 0.6 × 10−4°C.−1, the expansion coefficient in the direction of molecular chain axis must be negative except in the transition region near 80°C. The variation of molecular chain axis separation with temperature showed an irregularity at about 80°C. but none near 130°C. in the crystalline region. Infrared absorbance of film samples of PTFE was measured at different temperatures of 25 to 150°C. range for 518, 627, and 639 cm.−1 bands. On absorbance–temperature curves for those b̀ands, irregularities were observed near 30, 50, 90, and 130°C. Particularly with 518 cm.−1 band, a more crystalline sample gave more distinct irregularities near 50 and 90°C. than a less crystalline sample. The change at about 90°C. in infrared spectra may correspond to that obtained by x‐ray measurements near 80°C., which was thought to occur in the crystalline region. The results obtained by x‐ray and infrared measurements support the previous results by thermal, rheological, and dielectric methods: there exist first‐order transitions in the crystalline region at about 90°C. and second‐order transitions in the amorphous region at about 130°C.
Ultrasonic degradation of polysiloxane solutions
Authors: Shaw M. T. , Rodriguez F. 
Published: April 2003

AbstractFractions of dimethylsiloxane polymer with viscosity‐average molecular weights from 2.4 × 105 to 1.3 × 106 were dissolved in toluene in concentrations from 0.01 to 1.0 g./dl. These solutions were subjected to ultrasonic degradation at 20,000 cps for periods extending to as much as 960 min. in a water‐cooled reaction vessel. Gel permeation chromatography shows that samples with different initial distributions approach the same distribution after 120 min. of degradation. Dilution of the polymer from 1.0 to 0.01 g./dl. more than triples the degradation per gram of polymer but requires 10 times as much energy per gram of polymer to degrade from a number‐average molecular weight of 106 to 105. Increasing the power input from 36 to 72 w. almost doubles the degradation rate per gram of polymer.
Further aspects of the thermal degradation of epoxide resins
Authors: Keenan M. A. , Smith D. A. 
Published: April 2003

AbstractThis paper describes an investigation into the degradation of a purified epoxide based on the diglycidyl ether of bisphenol A hardened with p,p′‐diaminodiphenylmethane. The method used was that of hot‐wire pyrolysis followed by gas chromatography. Special attention was given to the problem of solid residues formed on the pyrolyzer tube, and evidence was found that these probably contain oligomers. Resonance‐stabilized free radicals also appear to be formed, and evidence is found to support the idea of dehydration during degradation, originally put forward by Lee. An attempt, based on first principles, is made to explain the degradation of epoxides, using evidence from previous work as well as that described in this paper.
Preparation, glass transition temperature, and δ relaxation effect of poly(vinyl isonicotinate)
Authors: Pizzirani G. , Magagnini P. L. 
Published: April 2003

AbstractPoly(vinyl isonicotinate) was prepared by esterification of poly(vinyl alcohol) with isonicotinoyl chloride in pyridine solution. Poly(vinyl nicotinate) was also prepared. Density, refractive index, and glass transition of the polymers were determined. The low temperature dynamic mechanical properties of poly(vinyl isonicotinate) are characterized by a relaxation effect which is associated with thermally excited motions of the pyridine rings (δ relaxation). The strong displacement of such a phenomenon toward higher temperatures, with respect to poly(vinyl benzoate), is interpreted as due to the elevated polarity of the pyridine ring.
Morphology of polymer of ethylene sulfide and its block copolymer with styrene
Authors: Balcerzyk E. , Pstrocki H. , Włodarski G. 
Published: April 2003

AbstractIt has been found that poly(ethylene sulfide) obtained by anionic polymerization in tetrahydrofuran assumes the shapes of platelets, microhedrites, microspherulites, or particles of irregular structure, depending upon the molecular weight of poly(ethylene sulfide). In the case of block copolymers of ethylene sulfide and styrene, the morphological form has been found to be dependent upon the composition of the copolymer.
Effect of the thermal history of polymers on their dynamic mechanical properties
Authors: Eldridge J. E. 
Published: April 2003

AbstractA torsion pendulum was used to compare quenched and annealed specimens of representative polymers with respect to their dynamic mechanical properties. Among amorphous polymers, the effects of thermal history appear to be both moderate and similar for different polymers. For some crystalline polymers, the effects of thermal history are again moderate. However, the effects are very great in one of the crystalline polymers selected, presumably because it is easily supercooled below its melting point.
Preparation of adherent films of poly‐p‐xylylenes on aluminum by electrolysis
Authors: Ross Sidney D. , Kelley Donald J. 
Published: April 2003

AbstractThe electrolysis of solutions of p‐methylbenzyltrimethylammonium nitrate or, better, p‐xylylenebis(trimethylammonium nitrate) or p‐xylylenebis(triphenylphosphonium chloride or bromide) in a polar organic solvent with an aluminum cathode and a platinum anode results in the formation of adherent coatings of poly‐p‐xylylene on the cathode. The mechanism of this reaction involves the electrochemical generation of p‐xylylene and its subsequent polymerization on the aluminum cathode. Competing reactions are formation of p‐xylene and reduction of the solvent.
Compressibility of elastomers with crystalline fillers and microvoid inhomogeneities related to various empirical equations of state for liquids and solids
Authors: Surland C. C. 
Published: April 2003

AbstractModified classical compressibility techniques are described which measure both the adiabatic and isothermal bulk moduli of polymers. These differ from familiar methods principally in the utilization of sensitive electronic deformation sensors (differential transformers) to assess volume changes, the autographic recording of pressure and volume changes during an essentially quasi‐static pressurization cycle. The uniaxial and volumetric methods both characterize the compressibility behavior of polymers in the relatively low pressure region (0–100 atm.). Compressibility data for several well‐known liquids and solids are reported. The nonlinear nature of the PV behavior of liquids are shown to be adequately characterized by a simple equation of state which is applicable to rubbery polymerics as well. Equations of state for polymers and filled polymers containing dispersed void inhomogeneities are discussed. Relationships based upon the infinitesimal theory of the deformations of an externally pressurized hollow sphere are compared with more complex equations of state which consider finite deformations at the center of a hollow sphere. It is concluded that the experimental data for the compressibility of voided solids containing less than 0.5% of initial void volume are best represented by the simpler equations of state derived from infinitesimal theory.
Preparation of sec‐butanol‐modified melamine–formaldehyde resin varnish
Authors: Motoyama Yoshiaki , Uchida Keiichi 
Published: April 2003

Abstractsec‐Butanol was employed to prepare etherified methylol–melamine resins to be used in the coatings industry as crosslinking agents. Difficulties associated with slow rate of etherification as compared to the rate of polycondensation of methylol–melamine were overcome by finding the determining factors which controlled the two competitive reactions independently. Attempts were made to interpret the effects of various factors from a mechanistic point of view.
Some effects of cocatalyst structure on the anionic polymerization of ϵ‐caprolactam. II.
Authors: Scelia Richard P. , Schonfeld Steven E. , Donaruma L. Guy 
Published: April 2003

AbstractA study of the effect of catalyst (base) concentration and N‐acylcaprolactam cocatalyst size and substitution on the fast anionic polymerization of caprolactam indicated that a steric effect due to cocatalyst size exists, and perhaps an electronic effect due to cocatalyst substitution was noted. The rate of polymerization, degree of polymerization, and yield of polymer are related to these effects. It was also noted that at high base concentrations, the rate and degree of polymerization along with the product yields all decrease. These latter observations suggest that reinterpretation of some of the reaction mechanism data may be important if polymer degradation is not an appreciable factor during the reaction.
Epoxy resins from substituted benzoic acids–formaldehyde resins
Authors: Tanaka Yoshio , Kakiuchi Hiroshi 
Published: April 2003

AbstractSome polybasic acid derivatives were obtained from substituted benzoic acids such asp‐ ando‐toluic acids, andp‐formaldehyde in concentrated sulfuric acid by a method similar to that of Naokawa et al. The structure of these resinous substituted benzoic acid–formaldehyde materials was determined by a paper chromatography and infrared spectrum analysis, and found to bemagnified imagewheren= 0–2; R = H, R′, and R″ = H or CH3, respectively. New glycidyl‐ester‐type epoxy resins were prepared from these substituted benzoic acid–formaldehyde resins and epichlorohydrin in the presence of sodium hydroxide, using dioxane as a solvent. These resins were considered to have the general structure shown above, wheren= 0–2, , and R′ and R″ = H or CH3, respectively.
Anomalous depression of rubbery modulus through crosslinking
Authors: Cooper Stuart L. , Tobolsky Arthur V. 
Published: April 2003

AbstractIntroduction of primary covalent crosslinks into linear, segmented elastomers was followed by observing their modulus–temperature behavior. The behavior of the linear segmented polymers is explained by association of glassy segments into regions which act as filler and quasi‐crosslink. In several cases crosslinkage disrupts these regions and thereby lowers the “plateau” modulus.
Viscoelastic properties of plasticized amylose films
Authors: Nakamura Shigeo , Tobolsky A. V. 
Published: April 2003

AbstractThe viscoelastic properties of amylose films plasticized with dimethyl sulfoxide were studied. The modulus–temperature curves of dimethyl sulfoxide‐plasticized amylose are typical for semicrystalline polymers at the higher concentrations of amylose and pass to those of amorphous polymers with the decrease of amylose content. The glassy modulus is not affected by the incorporation of dimethyl sulfoxide, but the rubbery modulus and Tg are depressed with increased dimethyl sulfoxide. The change of Tg with plasticization can be represented by two approximately straight lines, one representing the lower concentration region of amylose and the other the higher one. The critical concentration is about 60% amylose. When the results of modulus–time measurements and x‐ray diffraction are considered together, in a system of amylose–dimethyl sulfoxide, amylose exists as a semicrystalline polymer at high concentrations of amylose, and it acts intermediate between semicrystalline and amorphous polymers at lower concentrations below about 60%. From an extrapolation of the data of Tg of plasticized amylose, Tg of pure amylose appears to be approximately 330°C. The viscoelastic properties of amylose films plasticized with dimethyl sulfoxide–sorbitol mixtures were also studied.
Method for separating intramolecular and intermolecular interactions which influence polymer glass temperatures
Authors: Wyman Donald P. 
Published: April 2003

AbstractIt is shown that the glass temperature (Tg) for homopolymers of the type CH2CXYcan be expressed by a simple additive equation involving two terms: (1) a parameter E which is directly related to the molar cohesion energy and (2) a parameter Es* which is a measure of restricted rotation about valence bonds. Es*, at least for a large number of polymers, is related to the Mark‐Houwink Kθ value (as measured in θ solvents at Tθ) via anti‐log Es* ∝ 1/Kθ2/3. It is also shown that for homologous series [e.g., poly(n‐alkyl methacrylates)], there is a constant relationship between E and antilog Es*. The Tg values for copolymers may be estimated by a simple weighted (via mole fraction) summation of the E and Es* values of the components. When used in this form, a linear variation between Tg and composition is assumed, which may not be strictly correct but still yields useful approximations.
The melting of 66 nylon: Observations by differential thermal analysis
Authors: Hybart F. J. , Platt J. D. 
Published: April 2003

AbstractDifferential thermal analyses of many 66 nylon samples have shown two endotherms in the melting range. This effect occurs with drawn nylon yarn, as previously observed by White, and also with annealed and precipitated nylon samples. Methods for the preparation of these samples are reported. At 242°C. the development from the melt of crystalline material which gives two melting peaks is associated with annealing rather than with the primary crystallization process. Previous observations of multiple melting peaks with other polymers are discussed.
Dynamic mechanical properties of a TiO2‐filled crosslinked epoxy resin from 20–90°C.
Authors: Galperin I. 
Published: April 2003

AbstractDynamic mechanical measurements were made with a torsional pendulum of a TiO filled epoxy polymer (crosslinked with hexamethylene diamine) over a temperature range from 20–90°C., at filler concentrations of 0–40 wt.‐%. The second‐order transition temperature (Tg) was raised as the filler content increased. The behavior of TiO2 filler results in a long‐range immobilization of the highly crosslinked system with resultant increases in shear modulus (higher G′) as well as decreased capacity for energy dissipation (lower damping factor). The out‐of‐phase modulus (G″) increased with filler content as well. The magnitudes of the slope parameters Hr (representing G′ data above Tg) and Hg (representing G′ data below Tg) decreased with greater filler content. The possibility is set forth that the TiO2 filler causes a different distribution of mobility around the nitrogen junction as well as a change in the effective number of CH2 units between crosslinks.
Environment‐influenced surface layer in polymers
Authors: Cuthrell R. E. 
Published: April 2003

AbstractSeveral epoxy polymers, poly(methyl methacrylate), a highly plasticized polyethylene, and a polyethylene of molecular weight 2500 were found to be influenced to a considerable depth from the surface by the mold material or the atmospheric environment. The results presented are interpreted in terms of a diffuse double layer induced by the mold in the polymer surface region. These environmental effects appear to be greatest for the epoxy systems and are evident to a lesser extent, progressively, as the molded polymer is changed to materials of higher purity or narrower molecular weight range.
Investigation of fast‐setting acrylic adhesives for bonding attachments to human tooth surfaces
Authors: Snyder William H. , Wilson Charles E. , Newman George V. , Semen John 
Published: April 2003

AbstractSome of the problems encountered in adhesive bonding of plastic attachments to human tooth surfaces were investigated. Acrylic adhesives based on poly(methyl methacrylate)–methyl methacrylate monomer mixtures with benzoyl peroxide initiation and N,N‐dimethylaniline acceleration were utilized. Both homopolymers and copolymers were investigated. Recently extracted upper central incisors were employed in the bonding experiments. Bond strengths were improved by pretreating the tooth surfaces with mineral acids such as H3PO4. Surface wetting by the liquid adhesive was shown to be improved by the acid treatment. The molecular weight of polymer or copolymer employed in the liquid adhesive had an important effect on bond strengths. The optimum molecular weight for obtaining maximum bond strengths was around 20,000 g./mole. Water immersion of the bonded specimens at 37°C. for periods up to 6 weeks had a deleterious effect on bond strengths. Nevertheless, it was shown that some of the adhesives formed reasonably strong bonds for periods exceeding 6 months even with water immersion.