bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic graft copolymerization. II. Graft copolymerization of β‐propiolactone onto acrylonitrile–sodium acrylate copolymer
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro
Published: April 2003

Polyacrylonitrile–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

The 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

Infrared 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

Ion‐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

The 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

Several 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

By 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

Fractions 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

This 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.
Free‐radical concentration in polymerizations
Authors: Vandegaer Jan E. , Douglas Damon G.
Published: April 2003

A method is described for deriving by digital computer a temperature program which, when applied to batch polymerization, will keep the supply of new free radicals constant throughout the main part of the reaction.
Preparation, glass transition temperature, and δ relaxation effect of poly(vinyl isonicotinate)
Authors: Pizzirani G. , Magagnini P. L.
Published: April 2003

Poly(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

It 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

A 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

The 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

Modified 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

sec‐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

A 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

Some 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

Introduction 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

The 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

It 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

Differential 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

Dynamic 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

Several 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

Some 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.
Large‐scale fractionation of poly(vinyl chloride) and characterization of the fractions
Authors: Pezzin G. , Sanmartin G. , Zilio‐Grandi F.
Published: April 2003

A large‐scale fractionation of poly(vinyl chloride) (3000 g.) has been carried out by a fractional precipitation method. The molecular weight distribution of some fractions has been controlled by refractionation. The fractions have been also characterized by viscometry, osmometry, light‐scattering, and glass transition temperature measurements. The data available in literature concerning the molecular weight characterization of poly(vinyl chloride) fractions have been critically reviewed. It has been shown that most of the viscometric and osmometric data are in good agreement when the molecular weights are below 105. Above 105 the literature discrepancies can be attributed to aggregation.
Preparation of permselective membranes by means of a radioinduced grafting. I. Cation‐selective
Authors: Munari S. , Vigo F. , Tealdo G. , Rossi C.
Published: April 2003

Permselective cationic membranes were prepared by a radioinduced grafting method of styrene onto PTFE, and a preirradiation technique was used. Some attempts were made to characterize the membranes. They show mechanical properties similar to the PTFE matrix, and good electrochemical behavior, i.e., good permselectivity, which, nevertheless, decreased with decreasing solutions concentration. Such behavior has been related to a larger swelling in diluted solutions. Swelling properties in aqueous solutions of KCl and some organic solvents are also reported.
Properties of random and block copolymers of butadiene and styrene. I. Dynamic properties and glassy transition temperatures
Authors: Kraus G. , Childers C. W. , Gruver J. T.
Published: April 2003

The effect of monomer sequence on physical properties was investigated for butadienestyrene solution copolymers made by organolithium initiation. The polymers varied from random copolymers of uniform composition along the polymer chain to ideal block polymers of specific block sequence arrangement and included rubbers of intermediate degrees of randomness. Uniform composition random copolymers exhibit a single glass transition temperature and a very narrow dynamic loss peak corresponding to this transition. The glass transition can be predicted from the styrene content and the microstructure of the butadiene portion of the rubber. Random copolymers in which composition varies along the polymer chain, and to some extent between molecules, exhibit a single glass transition, but the dynamic loss peak is broadened. The extent of this broadening is shown to be compatible with the sequence distribution, polymer segments of various compositions losing mobility at different temperatures. This indicates a tendency for association between segments of different temperatures. This indicates a tendency for association between segments of different chains which are similar in composition. Block copolymers display two transitions, corresponding to Tg for each type of block. The position and width of the dynamic loss peaks are related to block length and compositional purity of the blocks.
Changes in the reactivity of functional groups during polyesterification: A new approach to polymerization in fatty‐acid‐modified polyesters (alkyd resins)
Authors: Solomon D. H. , Loft B. C. , Swift Jean D.
Published: April 2003

Gel‐point calculations based on the theory of polyesterification proposed by Flory do not agree with the experimental values even when Bobalek's concept of gel point as the first formation of infinite molecules (microgel) is used. Resins covering the range 30–60% oil length were prepared and examined by electron microscopy for the presence of microgel particles. The extent of reaction at which microgel forms is discussed in relation to the concept of equal reactivity. The conditions necessary for the formation of microgel particles and the significance of these observations to the basic assumptions used in developing the theory of polyesterification are discussed.
Graft copolymerization of methyl methacrylate and natural rubber
Authors: Ghosh Premamoy , Sengupta Pranab K.
Published: April 2003

Graft copolymerization of natural rubber and MMA was carried out in the presence of Bz2O2 or AIBN as thermal initiator and hydrogen peroxide or benzophenone as photosensitizer. From the overall copolymerization product, the rubber–PMMA graft copolymer fraction was isolated from unreacted rubber and free PMMA fractions and composition characterization of the separated fractions was done by determination of rubber unsaturation. The efficiency of grafting under different conditions has been calculated and compared.
Studies on the stretching of polypropylene film. I. Two‐step biaxial stretching
Authors: Okajima Saburo , Kurihara Kazuhiko , Homma Keisuke
Published: April 2003

A polypropylene film was stretched at 100–160°C., quenched to room temperature, and then restretched at the same temperature perpendicularly to the first stretching. The reorientation behavior was investigated by using optical and x‐ray methods. During the restretching the monoaxial orientation caused by the stretching is converted into a new monoaxial orientation through a balanced state, where npp = nps < nss. The more or less parallel orientation to the film surface of the polypropylene molecules, brought about by the first stretching, proceeds further on restretching. nss is a linear function of the degree of stretching in area vA. The inclination of this line is independent of the type of deformation, stretching, or restretching, provided the temperature is kept constant. At 160°C. the plot of nss versus thickness is less steep than it is at 100 or 130°C. The overall reorientation apparently proceeds according to Kratky's first deformation law. The x‐ray pattern of a res̀tretched film is a four‐point diagram which indicates the existence of a pair of reorientation axes inclined symmetrically against the stretching axis. The inclination grows larger with restretching, and the axes merge into the restretching axis at extreme restretching. This phenomenon is less pronounced when the restretching is carried out at higher temperatures. The density of the restretched film is determined mainly by the stretching temperature, but extreme restretching has a tendency to lower it very slightly.
Environmental stability of ABS plastics
Authors: Kelleher P. G. , Boyle D. J. , Gesner B. D.
Published: April 2003

Experiments with different ABS resins indicate that thermal stability in this class of polymers is dependent upon the ratio of styrene–acrylonitrile copolymer to polybutadiene rubber in the graft phase; resins containing more highly grafted rubber are more resistant to thermal oxidation. It is also found that in outdoor aging there is a minimum carbon black loading for these resins below which light screening is not effective.
Studies with thin membranes. III. Measurement of water permeabilities of parlodion membranes formed by the dip technique
Authors: Lakshminarayanaiah N.
Published: April 2003

Thin Parlodion membranes whose preparation and electrochemical properties have already been described are used to study permeation of water through them. All the membranes allowed water to go through them when subjected to gradients of mechanical pressure or chemical potential. Thicker membranes were less permeable to water than thinner membranes. The total water flow observed under the influence of an applied pressure was analyzed in terms of an existing theory due to Ticknor and found inadequate to describe the flow in thicker membranes containing low quantities of water, whereas the flow in thinner membranes of moderate water content was found to be made up of both viscous and diffusional components. On the contrary, analysis of both the total and isotopic diffusional flows from the standpoint of another theory due to Mauro showed that all membranes gave flows which were composed of both diffusional and viscous components, the proportion of the former in the total flow increasing with increasing thickness of the membrane. The permeability data have been used to derive values for both the average radius of membrane pores and the total number of such pores present in different membranes.
Kinetic analysis of the autohesion of raw SBR samples
Authors: Baumbach D. O.
Published: April 2003

A kinetic analysis of the autohesion of raw, cold, emulsion SBR rubbers having number‐average molecular weights ranging from 74,000 to 169,000 was undertaken by using the modified Wallace tackmeter. The autohesion was observed to be a reversible process following first‐order kinetics with respect to the formation of elementary area bonds. The application of greater contact pressures during autohesion increase in the kinetic work, bond strength, and time required for bond rupture. A practical aspect of the study shows that the contact time necessary to form a complete area bond is reduced by: (1) the annealing of samples to release internal stresses; (2) production of clean and very smooth surfaces; (3) equilibrating samples under pressure prior to joining them; (4) lowering the sample temperature. The raw SBR offering the best potential autohesive properties has a Mn of 133,000 and ML‐4 (212°F.) of 66.
Stress softening in natural rubber vulcanizates. Part V. The anomalous tensile behavior of natural rubber
Authors: Harwood J. A. C. , Payne A. R.
Published: April 2003

Stress‐strain cycling of natural rubber to high strains produces greater softening than amorphous rubbers, but only if the force on the sample is relaxed below a certain value during the cycle. This phenomenon, attributed to crystallization shows why nonrelaxing tests give a longer fatigue life than relaxing tests.
The use of porous glass as a column packing for gel permeation chromatography
Authors: Cantow M. J. R. , Johnson J. F.
Published: April 2003

Use of porous glass with a broad pore‐size distribution as a column packing for gel permeation chromatography has been investigated. The porous glass is readily available, and columns are packed easily and have excellent mechanical stability. Separations of polystyrene over molecular weight ranges of 500–2,000,000 have been obtained. Porous glass thus appears to be a useful packing material for gel permeation chromatography.
Size analysis of polymer latex powder. Comparison of results obtained by means of the I.C.I.–Joyce, Loebl disk centrifuge, the coulter counter, and the electron microscope
Authors: Eckhoff R. K.
Published: April 2003

The volume frequency size distribution of PVC latex powder was determined by means of three different methods, which all gave the same frequency maximum at about 0.8–0.9 μ diameter. While the electron microscope analysis, which allows the agglomerates to be resolved into individual primary particles, did not show any particles above 1.5 μ in a sample of 9000, both the Coulter counter and the disk centrifuge showed a considerable amount of larger particles.
Regulation of molecular weight of styrene–butadiene rubber. II. Influence of variation of polymerization recipe on the regulating efficiency of diisopropyl xanthogen disulfide
Authors: V´clavek Vladimíar
Published: April 2003

The influence of kind and amount of an anionic emulsifier, pH of water phase, addition of free rosin, and content of conjugated structures in rosin on the regulation efficiency of diisopropyl xanthogen disulfide in emulsion copolymerization of butadiene with styrene at +5°C. was studied. The apparent chain transfer constant C decreased in the order: Li+ > Na+ > K+, for the cations with the hydrolysis of rosin soap. This soap is replaceable with other anionic emulsifiers, C being dependent on the absorption area of one soap molecule. With increasing amount of soap the value of C decreased. With the decreasing pH of the water phase, the value of C increases. This fact can be explained by the increase in hydrolysis of carboxylic groups of rosin and oleate soaps and an increase in the permeability of the monomer–polymer particle surface to molecules of regulator. This tendency does not exist in the case of sulfonate‐type soaps. After addition of free rosin to the monomer phase, a similar increase in C is noted. The value of C increased also with an increase in the content of conjugated structures characterized by a value δ, which is related to the retardation of polymerization. The standard polymerization recipe at pH 10.8 is suitable from the point of view of using diisopropyl xanthogen disulfide as a molecular weight regulator.
Regulation of molecular weight of styrene–butadiene rubber. III. Choice of regulator from the homologous series of aliphatic mercaptans
Authors: Václavek Valdimír
Published: April 2003

The regulating efficiency of four aliphatic mercaptans was studied in emulsion copolymerization of butadiene with styrene, at +5°C. with the use of the redox system, diisopropylbenzene hydroperoxide–complexed ferrous iron–sodium formaldehyde sulfoxylate as an initiator and the sodium soap of disproportionated rosin as an emulsifier. The apparent transfer constants C of tertiary mercaptans decreased logarithmically with increasing length of molecule. This tendency is connected with the analogous dependency of solubilities of these compounds in water. The mercaptans did not affect the rate of polymerization. The value of C is independent of the amount of regulator used. With the value of C, the amount of regulator, and the conversion known, it is possible to predict the molecular weight of the polymers, except for the region of poor regulation, where the deteriorative influence of termination and crosslinking reactions takes place. The apparent transfer constant of tertiary dodecyl mercaptan decreased with increasing rate of polymerization. After elimination of diffuse processes, the value of the actual relative transfer constant was calculated. The tertiary dodecyl mercaptan has been selected as the most convenient molecular weight regulator for emulsion copolymerization of butadiene with styrene of all compounds studied for the system mentioned.
Effect of γ‐radiation on the thermal conductivity of polypropylene
Authors: Tomlinson J. N. , Kline D. E.
Published: April 2003

The effect of 60Co γ‐radiation on the thermal conductivity of polypropylene (PP) has been studied over the temperature range 0–160°C. for radiation doses of 600 and 1800 Mrad. The conductivity of unirradiated specimens rises from 4.5 × 10−4 cgs units (cal./cm.‐sec.‐°C.) at 0°C. to 4.8 × 10−4cgs units at 80°C. and subsequently decreases with temperature to a value of about 3.1 × 10−4cgs units at 160°C. Upon irradiation to 600 Mrad the thermal conductivity is lowered over the 0–150°C. temperature range. Above 90°C. the conductivity decreases with temperature and becomes relatively constant at 3.4 × 10−4 cgs units from 120 to 160°C. Differential scanning calorimeter (DCS) measurements from 30 to 200°C. show that irradiation to 600 Mrad lowers the energy associated with crystalline melting and shifts the endotherm melting peak from about 160 to 105°C. Irradiation to 1800 Mrad results in additional lowering of the thermal conductivity over the 50–160°C. range, a further decrease in area of the endothermic peak and a shift of its maximum peak position to about 75°C. The effects of radiation on the thermal conductivity of polypropylene are compared and correlated with the observed effects of radiation on the dynamic mechanical behavior.
Alkali solubility of carboxylated polymer emulsions
Authors: Muroi Soichi , Hosoi Keizo , Ishikawa Teruyuki
Published: April 2003

The solubility of carboxylated polymer emulsions in an aqueous alkaline solution was studied. The alkali solubility was shown to depend on the degree of carboxylation, the hydrophilic nature of the noncarboxylic main components, the degree of polymerization, the glass transition temperature, the chain configuration, and the dissolution temperature. Emulsions of the copolymer containing acrylic acid units showed considerably different dissolution behavior from those containing methacrylic acid units, possibly owing to the difference in the distribution state of carboxylic units inside the particle. It is deduced that methacrylic acid units are distributed more homogeneously inside the particle than acrylic acid units.
Thermal behavior of dimethyl‐m‐carboranyl–dimethylsiloxane copolymers
Authors: Delman A. D. , Stein A. A. , Kelly J. J. , Simms B. B.
Published: April 2003

The manner in which a series of silcarboranylene–siloxane polymers behave in air at elevated temperatures was investigated by thermogravimetric, isothermogravimetric, and differential thermal analyses techniques. Results indicate that methyl pendant groups on the polymers undergo thermal and oxidative degradations at temperatures under 600°C. Final weight losses of the polymers, however, are significantly lower than that shown by dimethylsiloxanes. The reduced volatility is attributed to the inhibition of thermooxidation by the m‐carboranylene group in the polymer molecules. This protective influence decreases apparently as the distance between the carborane nucleus and the methyl groups increases.
Polyelectrolyte complexes: Permeability to water and potential uses in ophthalmology
Authors: Refojo Miguel F.
Published: April 2003

Complexes from poly(vinylbenzyltrimethylammonium chloride) and polystyrene‐sulfonate are transparent, water‐insoluble materials which offer interesting possibilities in ophthalmology for contact lenses and surgical implants. The permeability to water of a series of neutral polyelectrolyte complex membranes was determined. The measurements were carried out at relatively low pressure gradients (20–900 mm. Hg). The results are in good agreement with previously reported data obtained at higher pressures (6.9 atm. and higher). The refractive index of the complexes was also determined, and apparently a linear relationship exists between the refractive index and the amount of water in the complex: 70% water, nD 1.40; 45% water, nD 1.48; 35% water, nD 1.51. A polyelectrolyte complex membrane 0.09 mm. thick containing 60% water at equilibrium swelling will have a similar permeability to water as the endothelium of the cornea (1.55 × 10−11 cm.3/sec.‐dyne) at 35°C. The same membrane, but with a thickness of 0.03 mm., will have a permeability similar to that of the whole corneal stroma (4.9 × 10−11 cm.3/sec.‐dyne). At 0.21 mm. thickness the membrane will have a permeability similar to that of the epithelium (0.67 × 10−11 cm.3/sec.‐dyne).
On the crystallite orientation in jute and mesta fibers under different moisture conditions
Authors: Ray P. K.
Published: April 2003

The Hermans' average angle of orientation, the angle at 40% intensity, and the Hermans' orientation factor have been studied in raw and delignified jute and mesta fibers under different moisture conditions. It is observed that the average orientation of micelles in these fibers improves on moisture absorption and further improves when the moist fiber is subjected to tension, and that the action of water is more pronounced in delignified jute fibers. The derangement of a fraction of the regions, contributing to the x‐ray pattern of these fibers, and the releasing of internal stresses have been cited here as possible caused of the phenomenon.
Selection of proper mounting media for examining heterogeneous copolymers with the phase microscope
Authors: Bond R. H. , Hannah R. E.
Published: April 2003

A technique for examining heterogeneous copolymers with the phase microscope is described. This method is based on the use of a mounting medium that displays selective solubility toward the constituent materials, thereby masking one or more phases in order to provide suitable phase contrast and isolation of the constituent to be examined.
Thermal decomposition of additive polymerization initiators. I. Azobisisobutyronitrile
Authors: Sasaki Hideki , Nagayama Masako
Published: April 2003

We measured the rate of thermal decomposition of azobisisobutyronitrile (AIBN) from the rate of loss of 2,2‐diphenylpicrylhydrazyl (DPPH) on reaction of the free radicals formed by thermal decomposition of azobisisobutyronitrile (AIBN) in organic solvents with DPPH. There has been some doubt about the quantitative relation between AIBN and DPPH required to get the rate constant of thermal decomposition of AIBN. In the past, AIBN has been used in excess, and the rate constants measured by using DPPH are smaller than they ought to be. In our experiments we used as little of AIBN relative to DPPH as possible and obtained a value of 3.8 × 10−4 min.−1 at 50°C. as the rate constant of the first‐order reaction, which was shown satisfactorily by the linearity of the graph. We also obtained 32 kcal./mole as activation energy. We were also able to make clear the meaning of the result when a large quantity of AIBN was used.
Properties of random and block copolymers of butadiene and styrene. II. Melt flow
Authors: Kraus G. , Gruver J. T.
Published: April 2003

Flow curves, log (rate of shear) versus log (shear stress), as functions of temperature were obtained for several butadiene‐styrene copolymers of fixed (25%) styrene content, differing in monomer sequence distribution. A random copolymer of constant composition along the polymer chain and narrow molecular weight distribution (MWD) exhibited behavior similar to linear, narrow MWD polybutadienes; the flow was Newtonian at low shear stresses, and the flow curves for various temperatures were accurately superimposable by a shift along the log (shear rate) axis. In a random copolymer varying in composition along the polymer chain, non‐Newtonian behavior was more pronounced, and temperature‐shear rate superposition did not succeed, a trend further perpetuated in copolymer of a single long styrene block sequence. The latter resemble branched polymers, as would be expected from association of the styrene blocks. With two styrene blocks, association produces network structures below the glass transition of polystyrene with consequent loss of flow. Disruption of these associations above Tg (styrene) imparts the greatest thermoplasticity to these elastomers. There is evidence, however, that some of the associations persist at temperatures well in excess of Tg (styrene).
Programmed polymer light‐scattering data
Authors: Evans J. M. , Huglin M. B. , Lindley J.
Published: April 2003

An ALGOL computer program has been devised to manipulate light‐scattering data from the Brice‐Phoenix photometer. The input consist of experimental values of the galvanometer deflections and filter factors used for each concentration c and angle of measurement θ. These are transformed to the appropriate variables in the fundamental equation including the particle scattering factor, viz: c/Qθ = (W/K*)M̄w−1[1 + (16/3) × π2n12λ〈S2〉 sin2 (θ/2)] + (W/K*)2A2c + (W/K*)3A3c2 in which Qθ is a corrected from of the Rayleigh ratio and (W/K*) is a composite constant term for the instrument and polymer–solvent system. By writing X̄ij for the variable c/Qθ at θi and cj, a function X is found by least squares to fit X̄ij, thus X = l + m sin (θ/2) + ncj + bcj2. The equations arising from minimizing ΣiK=1 ΣjL=1 (Xij − X̄ij)2 are solved by the computer to yield the best‐fitting coefficients l, m, n, and b. These can then be related simply to the molecular weight, root‐mean‐square radius of gyration, second and third virial coefficients, respectively. The final portion of the program is designed to check the fit of these coefficients. It yields a table of the differences between all experimental c/Qθ values and the coressponding ones obtained by inserting the derived l, m, n, and b into the fundamental equation. The procedure has been tested satisfactorily by using a well‐standardized sample of polystyrene in toluene at 30°C. and a wavelength of 436 mμ.
Polyurethanes derived from caprolactone polyesters and diamines
Authors: Magnusson Alan B.
Published: April 2003

Thermoplastic, light‐stable polyurethanes have been prepared by the interfacial poly‐condensation of secondary diamines with the bischloroformates of polyester diols derived from ε‐caprolactones. A straight‐line relationship was obtained from a logarithmic plot of inherent viscosity versus Mn. The effect of some structural variations on the properties of the polyurethanes is discussed. These variations included the molecular weight of the polyester diol, the initiator used in preparing the polyester diol, the introduction of a methyl substitutent on the caprolactone ring, and the structure of the diamine. Polyurethanes prepared from polyester diols of Mn from 2000–4000 are opaque, stiff materials which undergo a melting transition at 40–50°C. characteristic of the polyester component. Polyurethanes which are flexible and translucent at room temperature are obtained either by using a low molecular weight polyester diol or a copolyester diol containing > 25% methyl ε‐caprolactone. The polyurethanes described are soluble in several common solvents and can be cold‐drawn to produce material of high tensile strength. Thermal studies using DTA and TGA Show an exothermic reaction starting above 300°C. Rapid weight loss beginning at 300–330°C. and leveling off near 500°C. accounted for 85–90% of the total sample and is attributed to decomposition of the polyester Chains.
Structural characterization of vulcanizates. Part V. Determination of degree of chemical crosslinking of natural rubber gum vulcanizate networks
Authors: Bristow G. M. , Porter M.
Published: April 2003

A general treatment is given of the methods to be used in other parts of this series for calculating the degree of chemical crosslinking in natural rubber vulcanizates from stress–strain measurements in extension and from equilibrium volume swelling measurements. Corrections are required for the presence in the vulcanizate of appreciable quantities of particulate solids or soluble diluents and for the introduction of foreign atoms into the rubber network. For this purpose distinction is made between the rubber vulcanizate, the rubber matrix, the rubber network, and the rubber hydrocarbon component of the network. Expressions are derived, in terms of these concepts, for the Money‐Rivlin parameter, C1, measured on vulcanizates which have undergone various treatments.