ALBERT

Notes: The pulsed-gradient NMR method of Stejskal and Tanner was used to measure the diffusion of oil in synthetic cis-polyisoprene. The diffusion encounters no barriers with spacings at least up to several μm and generally displays free-volume behavior, obeying the WLF temperature dependence between -10°C and +130°C, and the Fujita-Doolittle concentration dependence between 10 and 90 vol-% oil.

Notes: A study was made of the effect of carboxylic monomers, such as itaconic acid, acrylic acid, and methacrylic acid, on the relative distribution of acid in the aqueous serum phase to that on the latex surface to that buried in the particle of carboxylated polystyrene latices prepared by emulsion polymerization. The relative acid distribution of the carboxylated latices was determined by the conductometric titration method of Hen. Effect of carboxylic monomer levels and latex particle size on acid distribution ratio are given. It is shown that itaconic acid, being the most hydrophilic and having the least solubility in styrene, tends to distribute itself in favor of the aqueous serum phase, while acrylic acid, which has limited solubility in styrene and being sufficiently hydrophilic, tends to prefer the particle surface predominantly. Methacrylic acid, being the most hydrophobic of the three carboxylic monomers studied and having good solubility in styrene, is shown to be concentrated inside the particle core. The observed results are compared with other similar findings in the literature and analyzed in the light of accepted mechanisms for emulsion polymerization of carboxylated styrene systems.

Notes: The uniplanar orientation of poly(p-phenylene terephthalamide) (PPTA) crystal was investigated by x-ray and infrared measurements. Thin PPTA films 3-15 μm thick were prepared by coagulating a sulfuric acid solution of PPTA with various coagulants. Two types of uniplanar orientation were observed, depending on the coagulant used. Thin film coagulated with water exhibits (0k0) uniplanar orientation and film coagulated with other coagulants such as methanol, ethanol, and acetone exhibits (h00) uniplanar orientation. These (h00) and (0k0) uniplanar orientations are formed with crystal modifications I and II, respectively. The (0k0) uniplanar orientation transforms to (h00) upon annealing, accompanying crystal transformation from modification II to modifications I. These uniplanar orientations may result from anisotropic crystal growth due to polymer-coagulant interaction along the hydrogen bond direction. The effect of these uniplanar orientations on the mechanical properties was also examined. The thin film having the (0k0) uniplanar orientation shows ductile fracture, whereas the one having the (h00) uniplanar orientation shows brittle fracture upon tensile deformation. These results are explained on the basis of the direction of the uniplanar orientation of the hydrogen-bonded sheet.

Notes: Poly(p-phenylene terephthalamide)(PTTA) films were prepared from sulfuric acid solution with various coagulants. X-ray diffraction and infrared absorption measurements revealed that the crystal structure of the film coagulated with water showed a new crystal modification II, which was different from the one previously reported by Northolt and Tadokoro et al. The latter structure is called here modification I. Modification II coagulated with water from a solution of lower polymer concentration irreversibly transformed to modification I upon annealing, whereas modification II prepared from highly concentrated solution was thermally stable and scarcely transformed to modification I upon annealing. A liquid crystal-like swollen structure was found in the intermediate stage of the formation of modification II. In this swollen state, x-ray diffraction revealed that water molecules are included in hydrogen-bonded planes and the intermolecular spacing along the van der Waals force direction was unaffected by the existence of the water and remained constant throughout the process of regeneration. Both modifications I and II were found to be stable on treatment with boiling solvents. The transformation of the swollen structure to modification I took place in boiling methanol and acetone.

Notes: The elastic properties of ethylene-propylene and ethylene-vinyl acetate copolymers crosslinked to different degrees were studied. A correction of the front factor with respect to temperature has been proposed for calculation of the concentration of network chains from shear modulus G. Deviations from the Gaussian approximation of the dependence of force on deformation were evaluated.

Notes: The thermoelastic properties of ethylene-propylene and ethylene-vinyl acetate copolymers crosslinked to different degrees were studied. An equation was proposed for calculating the relative contribution of the internal energy, fU/f, from the temperature dependence of shear modulus G. Analysis of a relation for calculating fU/f derived on the basis of the Mooney-Rivlin equation was made.

Notes: The melting and crystallization behavior of poly(tetramethylene terephthalate) and its copolymers with tetramethylene sebacate (≯ 20 mol %) has been studied using differential scanning calorimetry (DSC). The effect of the sebacate concentration on equilibrium melting temperature and crystallization behavior is discussed in terms of the theory of equilibrium crystallization of random copolymers. The multiple-melting behavior of these systems is described and interpreted in terms of the theory of equilibrium melting of chain-folded crystals, together with molecular fractionation during crystallization and melting and recrystallization during the DSC scan.

Notes: The specific surface areas of various particle size ranges of wood and peat were determined. The methods employed are mercury porosimetry, nitrogen adsorption, and solution isotherms. The results indicate that dye solution isotherms offer an accurate means of surface area measurement, however, the values obtained are dependent on (a) the chemical nature of the solute and adsorbent and (b) the molecular dimensions of the solute. Nitrogen isotherms indicate specific surfaces of (21 × 103)-(27 × 103) m2 kg-1 for wood depending on the particle size, while an area of 26.5 × 103 m2 kg-1 was obtained for peat independent of particle size. Acid dye isotherms yield specific surfaces considerably lower than nitrogen isotherm values; for wood (7.3 × 103)-(9.6 × 103) m2 kg-1 and for peat, (5.2 × 103)-(11.8 × 103) m2 kg-1. Basic dye studies, using wood, indicate surface areas similar in magnitude to those obtained from nitrogen isotherms. For peat, however, very large apparent surface areas are obtained (∼100 × 103 m2 kg-1) and are attributed to chemical interaction between dye molecules and adsorbent and stacking of dye molecules.

Notes: Polyethylene was drawn at temperatures ranging from 30° to 60°C in aggressive and nonaggressive environments. Fibrillation was found to occur in the aggressive environment, and this effect increased with temperature. The temperature effect was more prominent at lower strain rates. Thin films drawn in aggressive environments deformed inhomogeneously. Again, this effect was found to increase with increasing temperatures. Single crystal deformation was also found to be inhomogeneous, and “solvation” of the amorphous surface layer occurred in the presence of the aggressive environment. Infrared measurements of sorption under different loads indicated that there is an increase in the amount of sorbed materials with increasing load. Dynamic mechanical studies revealed the intracrystalline regions to be affected preferentially.

Notes: The effect of water vapor on a polyimide has been investigated in the temperature region of -190 to 325°C using an automated torsion pendulum. A damping peak, TH2O developes at -122°C (1 Hz) in the thermomechanical spectra of the polymer which is due to water-polymer interactions. The peak intensifies as the humidity of the conditioning atmosphere, at both 30° and at 325°C, increases and attains a limiting value at about 3000 ppmv H2O. The process is reversible. It is concluded that the number of sites in the polymer for interaction with water is low and limited (〈0.3 molecule H2O per polymer repeat unit) and, assuming direct proportionality between the intensity of the loss peak and the amount of water adsorbed, that the adsorption of water vapor follows the Langmuir isotherm.

Notes: A comprehensive experimental investigation is reported of the bulk polymerization of acrylonitrile (AN) to limiting conversion using 2,2′-azobisisobutyronitrile (AIBN) as initiator at 40°, 60°, and 80°C. Molecular weight development was followed by gel permeation chromatography (GPC).

Notes: Thermal analysis and kinetic studies have shown that oxidative reactions are responsible for acceleration in the rates of weight loss and depolymerization of cellulose on pyrolysis in air at temperatures below 300°C. The oxidative reactions include production of hydroperoxide, carbonyl, and carboxyl groups, which have been investigated at lower temperatures along with the rates of depolymerization and production of carbon monoxide and carbon dioxide. The experimental results are consistent with an autoxidation mechanism involving initiation, propagation, and decomposition reactions. At temperatures above 300°, the rate of pyrolysis is essentially the same in both air and nitrogen, indicating that thermal degradation is independent of the oxidative reactions.

Notes: The biological degradation of acrylonitrile-dimethylaminoethyl methacrylate and acrylonitrile-acrylic acid copolymers has been studied by evaluating copolymer films in a continuous in vitro rumen system. The copolymer films were examined before and after modification by reaction with ethylene oxide gas. The degradation of the acrylonitrile-dimethylaminoethyl methacrylate copolymer followed a pattern similar to that occurring on thermal degradation. Modification by reaction with ethylene oxide gas, which induces C=N conjugation, did not improve the resistance to degradation. The acrylonitrile-acrylic acid copolymer films disintegrated, but on prior modification by reaction with ethylene oxide they remained virtually unaltered. Modification of the acrylonitrile-acrylic acid copolymer results in crosslinking with an absence of C=N conjugation, leading to improved resistance to biological degradation.

Notes: The mechanical degradation of pulp cellulose fiber was studied at ambient temperature and at 77°K. ESR findings reveal that mechanical degradation occurs via free-radical routes. Three types of mechanoradicals contributing singlet, doublet, and triplet ESR signals are identified. The singlet signals are derived from the alkoxy radicals at C4 positions as a consequence of the cleavage of glucosidic bonds, the radical pairs generated at C1 positions contributing the doublet signals. Triplet signals are derived from the C2 and C3 positions due to the cleavage of C2 and C3 bonds. Of these radicals, alkoxy radicals are the most stable at ambient temperature. Carbon radicals are capable of interacting rapidly with oxygen molecules to produce peroxy radical intermediates, where alkoxy radicals are inert toward oxygen molecules. ESR study also reveals that cellulose mechanoradicals are capable of initiating vinyl polymerization. MMA propagating radicals are identified when the monomers are in contact with cellulose mechanoradicals. The ability of mechanoradicals to initiate graft copolymerization from cellulose fiber is discussed.

Notes: Modified polyethyleneimine products are hydrophobic with products from monohalotin reactants soluble in HMPA, DMSO, CHCI3 and 2,4-pentanedione, while products from dihalotin reactants are insoluble in all solvents. Antifungal activity varies markedly with the nature of the tin moiety. For products from triphenyltin chloride, antifungal activity is widespread and suitable to about 40 ppb of the polymer, which is clearly acceptable for medical and industrial uses. Thus, such modified polymers can be used as retarders of fungi related rot and mildew. The products show moderate high-temperature stabilities.

Notes: A relatively simple, reproducible method for the determination of grafting in high-impact polystyrene (HIPS) shows that high- and low-graft HIPS exhibit differences in morphology following treatment with an oxidative etching solution. Because this method is quite sensitive to small differences, it yields a more definitive evaluation of grafting in the finished polymer than any other previously used analytical procedure. These differences have been quantified, and the data used to compare relative grafting in polystyrenes reinforced with the same or different rubber types. The method shows an increase in grafting when either the peroxide initiator feed level or 1,2-vinyl content of the polybutadiene is increased.

Notes: By treatment with alkali in 2-methoxyethanol, poly(vinyl chloride) is converted to an insoluble network structure. On subsequent oxidation with 65% HNO3, a water-soluble mixture of acids is obtained. Per 1000 carbon atoms of the original polymer chain, approximately 4 moles succinic acid, 2 moles glutaric acid, and 1 mole adipic acid are found. In spite of the fact that the occurrence of succinic acid is in the same order as tail-to-tail polymerization in PVC, it must be assumed that unexpected aggregation of more than two CH2 groups is due to rearrangement during the alkali treatment or the oxidation procedure.

Notes: A three-parameter equation is put forward to evaluate the [η] of polymer solution from a wide range of concentrations, up to a relative viscosity of 100. The equation is tested by viscometric data of polystyrene, poly(vinyl chloride), poly(1-vinylnaphthalene), poly(2-vinylnaphthalene), and poly(4-vinylbiphenyl) at different temperatures and in a variety of solvents including mixed solvents. A statistical method is employed to analyze the experimental data. It is found that the values of [η] obtained by the new equation are consistently lower than those derived from the Huggins equation. However, the discrepancy is not more than 3% on average, and it does not affect the values of Mark-Houwink constants significantly. Other parameters of the equation are also computed.

Notes: Extrusion die swell of natural rubber compounded with a wide variety of carbon blacks has been determined in a capillary rheometer using a long circular die. The range of variation of carbon black loading, surface area, and structure are, respectively, 10 to 60 phr, 44 to 124 m2/g, and 78 to 120 cc/100 g. The effective carbon black volume fraction ϕe not participating in the strain recovery leading to die swell is assumed to be the sum of the actual filler volume fraction and the fraction of unextractable rubber determined experimentally for each compound. Bagley and Duffey's analysis of extrusion die swell of unfilled polymers as unconstrained elastic recovery was adopted for a filled elastomeric system whose relative shear modulus (G/G0) is assumed to vary as (1 - ϕe)-N. The matrix shear modulus G0, originally introduced by Nakazima and Shida on the basis of a linearized approximation, will depend on the shear stress level because of nonlinear deformation. The power N will vary with shear stress which changes the orientation of carbon black aggregates. Except for these features, die swell data for a wide range of carbon black compounds fall on a single curve when plotted in the manner of the predicted relation between the wall shear stress, die swell, and ϕe. Replacing ϕe by Medalia's ϕ′ based on an equivalent sphere concept introduces a larger scatter around the mean curve.

Notes: The following experiment was performed based on the assumption that the characteristic structural features of high molecular weight poly(vinyl chloride) (PVC) should be present to the same extent in its low molecular weight fractions. Two PVC fractions of molecular weight, 1500 and 800, respectively, (0.14% of total polymer) were isolated from bulk PVC (Mn 32,000) by extraction with methanol. This extract was transformed into paraffins by a new hydrogenation method using an excess of Raney nickel in order to facilitate identification. 13C-NMR spectral data of the paraffins showed that almost 2 out of 1000 carbon atoms were linked to a side chain with more than five carbon atoms, and 5 out of 1000 carbon atoms were methyl branched. Gas chromatography-mass spectrometry (GC-MS) analyses confirmed that the low molecular weight paraffins consisted of a sequence of even-numbered homologs. These findings suggest indirectly that the surprisingly low degradation temperature of PVC is due to the arrangement of the chlorine atoms rather than to the branching of the alkyl chain.

Notes: The morphology associated with the liquid-induced crystallization of poly(ethylene terephthalate) (PET) blended either with poly(tetramethylene terephthalate) (PTMT), atactic polystyrene (APS), or polycarbonate of bisphenol A (PC) was studied, along with the effects of nucleating agents and polymer molecular weight on this type of crystallization in PET. It was found that melt-mixed blends of PET and either PTMT or PC led to an apparent well-mixed, two-component material in which some copolymer formation may be in evidence judging from the material superstructure. Blending PET with APS appeared to produce distinctly phase-separated materials in which PET could be crystallized and APS dissolved out of the structure as a result of treatment of the blend with certain types of liquid. The incorporation of nucleating agents into PET was shown to measurably influence the spherulitic character of the subsequently liquid-induced crystallized polymer. Finally, it was determined that liquid-induced crystallized PET samples with number-average molecular weights of 18,000 and 30,000 had identical characteristic morphology and apparent crystallization kinetics.

Notes: Two polyanions and two polycations were prepared by the esterification of poly(vinyl alcohol). Properties of their neutral polyelectrolyte complex membranes were compared with those of polyelectrolyte membranes. The charged state on the membranes was related closely to the mechanochemical reaction, the salt rejection, and the solution permeability. Both the salt rejection and the water flux of neutral polyelectrolyte complex memberanes were lower than those of the corresponding acidic or basic complex membranes.

Notes: Small-angle x-ray methods were used to evaluate macromolecular parameters such as specific inner surface of the dispersed phase; transversal lengths such as length of inhomogeneity and length of coherence; and the air fraction of the scattering particles in Sansevieria roxburghi; these parameters were found to be 12.76 × 10-6 Å-1, 549.9 Å, 15.21 Å, and 0.17%, respectively. A small-angle Kratky camera was used for the experimental measurements, and the theories of Kratky and Kratky and Porod were utilized to evaluate these parameters. The sample under investigation is treated as a densely packed colloidal system belonging to general micelle systems.

Notes: Various methods are described and compared for the determination of particle size distributions (PSD) in the submicron range by a technique known as hydrodynamic chromatography (HDC). Data are presented for a series of monodisperse latexes to establish the validity of the Mie theory of light scattering in describing the detector optical density signal. Analyses for the PSD involve corrections to the experimental HDC chromatograms for the effects of dispersion and are broadly classified as integral and numerical methods. Comparisons of calculations are made to chromatograms for polydisperse latexes as well as synthetic, discontinuous distributions and show the critical role of the optical density-particle size relationship in determining resolution and calculation stability. An integral method involving a non-Gaussian form for the dispersion function and a polynomial expansion for the chromatogram and an iterative numerical method involving modifications of a previously published technique are shown to give the best results for the PSD. The discussion includes an analysis of the possibility of improved signal resolution using turbidity in the absorption wavelength region and refractive index measurements. The conclusion is reached that increased resolution with turbidity is preferable to refractive index measurement since lower particle concentrations can be used.

Notes: Solvent barrier studies for fluorinated polyethylene have shown that the fluorinated surfaces reduce the rate of permeation for many solvents. The barrier property has been related to physical and chemical properties of the solvent. For instance, solvents having a dielectric constant between 7 and 10 were not retained as well as solvents with a dielectric constant less than 7.

Notes: Chemically modified cotton fabric samples having different amounts of aromatic amino groups were prepared. These modified samples were reacted with tetrakis(hydroxymethyl)phosphonium chloride (THPC) under a variety of conditions using the pad-dry-thermofixation technique. The extent of the reaction (expressed as %P) was dependent of the degree of chemical modification of cotton, temperature and time of heating, and pH of the treating bath as well as incorporation of Lyofix CHN (N-methylol finishing agent), MgCl2·6H2O (catalyst), and urea at various concentrations. THPC did react with the modified cotton having a nitrogen content over a range of 0.4%-1.3% even in the absence of catalyst at a temperature as low as 30°C for 10 min to impart durable flame resistance to cotton. Increasing the temperature up to 80°C enhanced considerably the extent of reaction; he latter remained practically constant upon further increase in temperature. The reaction was favored in acidic media (pH 4-6), whereas alkaline media (pH 9-11) inhibited it. Incorporation of Lyofix CHN (9%), MgCl26H2O (1%), and urea (5%) along with THPC (25%) in the treating bath required a curing temperature of 120°C and a curing time of 5 min to achieve a fabric containing as much as 2.7% phosphorus with excellent durable flame resistance. A tentative mechanism of the reaction between THPC and the modified cotton was also elicited.

Notes: The diffusion coefficient at zero concentration and the free volume parameters in Fujita's free volume theory were measured for benzene, hexane, and heptane in modified polyethylene films using an unsteady-state absorption technique. Films were modified by gamma irradiation, solvent conditioning, and post- and preirradiation conditioning. Dc=0 was found to drop with irradiation, the drop being larger the larger the molecular size of the diffusing molecule. A relationship for the dependance of Dc=0 on the crosslink density is proposed. Solvent conditioning led to an increase in Dc=0 directly proportional to the swelling power of the conditioning agent and to the molecular size of the diffusant molecule. In most cases, combined treatment resulted in an increase in Dc=0, the extent of which was dependent upon the relative effect of the swellant and the irradiation dose. In all cases, postirradiation conditioning led to values of Dc=0 higher than those obtained by preirradiation conditioning. The fractional free volume of the polymer was found to decrease with irradiation, showing a marked drop at low doses when reaching a state where the dose was of small effect. Changes in f(0,T) with conditioning and with combined treatment followed the same general pattern as Dc=0. β(T) was unaffected by any kind of treatment studied. Bd changed in practically the same manner as f(0,T) but in the opposite direction. A method is proposed for the optimum choice of a membrane modification procedure based on solubility and diffusivity results.

Notes: A dynamic absorption technique was employed to determine the solubility of benzene, hexane, and heptane in modified polyethylene films. Films were modified by solvent annealing, crosslinking, and combinations thereof. Solvent annealing was found to increase the solubility while crosslinking led to its diminution. The effect of combined treatment on the solubility was found to be dependent on the sequence of treatment, the swelling power of the conditioning agent, and the irradiation dose. A slight effect of the solvent-diffusant pair was also observed. The solubility of the various vapors in crosslinked films was found to vary linearly with temperature. Solubility of some vapors in some of the conditioned films showed maxima with respect to temperature. The changes in solubility were explained in terms of the relative changes in the molecular volume of the diffusant and of the segmental mobility of the network chains with the various experimental conditions.

Notes: Tetramethyl thiuram disulfide, which functions as an inhibitor of the zinc dialkyldithiocarbamate-accelerated sulfur vulcanization, has been investigated by Mooney scorch measurements at 120°C and continuous measurements in a Vuremo curometer at temperatures from 100 to 140°C. The inhibition effect is due to the formation of a complex with zinc dialkyldithiocarbamate. The stability of the complex was calculated using the Hückel method which includes charge self-consistency on the central atom. The calculations are in a good agreement with the experimental results which illustrate that tetramethylthiuram disulfide, unlike an actual prevulcanization inhibitor, plays a significant role in all the stages of vulcanization. It decreases the crosslinking rate and increases the ultimate extent of vulcanization and its activation energy.

Notes: Comparisons were made of differential scanning-calorimetric (DSC) thermograms of both liquid and powdered commercial phenol-formaldehyde resins. By a combination of the results from analyses under a variety of conditions, such as ambient pressure, high pressure, using freeze-dried samples, and also by direct observation of the resin-curing process in wood-veneer assemblies, the curing reactions of phenol-formaldehyde resins were found to differ for resol and novolac systems. At a heating rate of 10°C/min, the resol resin showed endothermic curing reactions at temperatures of about 150°C, while the novolac-type resin showed an exothermic peak maximum at about 160°C. Results are presented to show how DSC can be used to differentiate between a resol and novolac system.

Notes: p-Phenylene oxadiazole/N-methyl hydrazide copolymers were prepared by polymerization of terephthalic acid, dimethyl terephthalate, and hydrazine sulfate in fuming sulfuric acid, and coagulation of the polymer was obtained in aqueous sulfuric acid. Fibers spun from these copolymers have unusually high strength and modulus, making these materials attractive for the reinforcement of articles such as tires. Yarn tenacities of 16-21 gpd and moduli of 350-450 gpd were obtained. Yarn of these copolymers showed no significant degradation under conditions to which a tire cord material is subjected in tire building and end use. In their performance in vehicle tires, tire cords were found to be competitive with other reinforcing agents such as fiber glass, steel, and commercial poly(p-phenyleneterephthalamide).

Notes: The electrokinetic properties such as zeta potential, surface charge density, and surface conductivity of polyester fibers grafted with acrylic acid and acrylonitrile were measured when cationic dye solutions were streamed through. The presence of the cationic dyes on the surface of the fibers and their specific adsorption at the carboxylic groups in the acrylic acid graft copolymer produce lowering of zeta potential. The decrease in surface charge density as the percent graft increases is due to the decrease in surface area of the fibers due to the adsorption of the cationic dyes. The same trend is observed with acrylonitrile-grafted fibers. The surface conductivity of the acrylonitrile-grafted polyester fibers increases with increase in dye concentration of the streaming solution. The results for the 27.4% grafted sample differed from those of the 7.32% and 12.1% grafts, which is indicative of the formation of a three-dimensional network causing change in both the physical structure as well as the chemical nature of the surface of the substrate.

Notes: The deformational, swelling, and potentiometric behavior of ionized water-swollen gels of 2-hydroxyethyl methacrylate (HEMA)-methacrylic acid (MA) copolymers used in biomedical and separation applications was investigated. With increasing degrees of neutralization α, the swelling degree strongly increases and the modulus Gs decreases. For the copolymers with MA content ≥ 30 mole-%, the dependence of Gs on α passes through a minimum. Comparison of the results with the modified theory of rubber elasticity shows that the decrease in Gs at low concentrations of charges on the chain is controlled mainly by the degree of swelling. At higher α, both the finite extensibility of network chains, caused by a high degree of swelling, and electrostatic interactions contribute to Gs. The dependence of the interaction parameter χ on the volume fraction of polymer in the gel, v2, is independent of α and closely resembles the dependence obtained for other hydrophilic polymers.

Notes: Methods for the elucidation of the chemical components of polyurethane foams are described. Foam samples of 50 mg were hydrolyzed in aqueous base and the resulting mixture of polyols and polyamines was analyzed by chemical ionization mass spectrometry (CI-MS) and high-pressure liquid chromatography (HPLC). The aromatic polyamines, which were separated by HPLC, produced few fragment ions under methane chemical ionization and were identified without difficulty. Each propoxylated homolog in the mixture of polyols was detected by CI-MS techniques, and approximate molecular weight profiles are presented for each polyol studied. Chemical ionization spectra are listed for samples of standard polyols and of base-hydrolyzed isocyanates. The hydrolysis products from urethane foam formulations were easily related to the standard compounds via CI-MS. These methods should be applicable to polymeric materials containing urethane, urea, and ester link-ages.

Notes: The kinetics of grafting of acrylonitrile, acrylic acid, and vinyl acetate onto polyester fiber by catalytic initiation and radiation were studied. The energy of activation determined for acrylic acid grafting by the catalytic method was 10.7 kcal/mole and that for vinyl acetate grafting by the radiation method, 11.7 kcal/mole. In the case of acrylonitrile grafting by the catalytic method, the rate of grafting decreased with increase in temperature of grafting, showing the differential behavior of the precipitating type of polymer from that of homogeneous polymerization.

Notes: An experimental study of the solution properties of poly(m-phenyleneisophthalamide) (MPD-I) in dimethylacetamide (DMA)/LiCl solutions is presented. Differential refractometry, light scattering photometry, dilute and concentrated solution viscometry, and normal stress experiments are reported and interpreted. This polymer in the concentration range investigated does not exhibit mesophase behavior in contrast to its para-linked analog. Generally, it behaves as a flexible polymer molecule; however, its capacity to become a polyelectrolyte strongly influences its behavior in the presence of LiCl. MPD-I is self-associated when dissolved in pure DMA but dissociates in DMA/LiCl solvent systems. The Zimm plots of MPD-I in DMA/LiCl solutions show distortion, probably due to polymer-salt interactions.

Notes: A polyhydrazide was prepared from terephthaldihydrazide (TDH) and terephthaloyl chloride (TCl) and copolyhydrazides from oxalicdihydrazide (ODH) and from TCl with a 50:50 molar mixture of ODH and TDH. The 50:50 copolymer gave superior spinning performance and fiber properties and was studied extensively as a candidate for tire cords. The best yarn tensile properties were 21.6 gpd (grams/denier) tenacity, 6% elongation, and 443 gpd modulus. Temperature resistance and creep resistance were good, while the resistance to uv light was only fair. Stability in rubber and adhesion to rubber were good. In radial tires built with equal-strength belts, mileage from tires having the copolymer cord in the belts was equal to that of steel-belted tires.

Notes: The effect of nine derivatives of salicylanilides on the elastic properties of ultraviolet-aged natural rubber have been investigated. The results are compared with similar blends without additives and also with reference samples containing phenyl salicylate. The compounds showed variable effects, but both o-Cl and p-OCH3 derivatives showed remarkable effects. They both help in the thermal crosslinking. Also, natural rubber samples containing these derivatives showed remarkable stability in tensile stress, elongation, and swelling.

Notes: A technique is described for producing a thick interlayer composite material composed of an epoxy resin as the matrix and an acrylic-coated fiberglass filler. Through the use of electrostatic forces, the fibers are encapsulated with a controlled, uniform layer(s) of the rubbery acrylic polymer. This coating is then crosslinked. These fibers are subsequently placed into the epoxy matrix, whereby the interfacial properties of the composite become modified. Rapid diffusion of the resin and curing agent results in an interpenetrating network being formed at the glass-epoxy interface. The placement of a uniform latex coating on the fiberglass surface results in improvements in the mechanical properties of the composite. Increases in damping, impact strength, and tensile properties are described.

Notes: In poly(vinyl alcohol) and polyacrylamide films containing the corresponding polymer-Cu2+ complexes, the reason why the films may gain surface electrical semiconductivity as high as 10-3 Ω-1 when treated with acetone solution of iodine was investigated. Optical and scanning electron microscope observations indicated that the coagulated polymer-Cu2+ complexes favor the appearance of the high conductivity and that the state of coagulation depends on the anions of the copper salts used as well as two parameters, F1 ≡ [Cu2+]/[MU] and F2 ≡ [OH-]/[Cu2+], where [MU] is the molar concentration of monomeric units of the polymer and [OH-] is that of hydroxide ions added. The effectiveness of the anions in causing coagulation decreases in the order of SO42- 〉 Cl- 〉 NO3- ≈ Br-. The whitish substance that appears on the film surface after the iodine treatment gives x-ray Debye-Scherrer rings characteristic of γ-CuI. The γ-CuI surface layer adheres to the film rather firmly, at least in polyacrylamide, and is responsible for the conductivity. By controlling the state of coagulation of the complexes and hence the formation of the γ-CuI surface layer, we have produced films with anisotropic surface electrical semiconductivity, i.e., σ∥ ≈ 10-4 Ω-1 and σ∥/σ⊥ = 1 ˜ 103. Optical and ESR spectra are also obtained to understand the mechanism of γ-CuI formation and to clarify the optical properties of the films.

Notes: Cation-exchange resins have been synthesized through the condensation of N-vinylcarbazole and poly(N-vinylcarbazole) with furfural in presence of anhydrous AlCl3 and subsequent sulfonation of the condensates. The resins have been characterized in respect to their polyfunctionality, exchange capacity, and thermal stability.

Notes: Polyethylenimine membranes consisting of linear polyethylenimine (PEI) and polyepichlorohydrin (PECH) were prepared by casting and heating an N,N-dimethylformamide solution of the two polymers under nitrogen at 100°C for 60 min. The membrane was also prepared by a heat-press method in a conventional manner. The cast membrane obtained was transparent. The membrane has a crosslinked structure due to the reaction between the secondary amino groups in PEI and the chloromethyl groups in PECH. Although a larger feed ratio of PEI/PECH gave membranes with a larger adsorption capacity for Cu2+ ions, the optimum ratio was 40/100 with respect to mechanical properties. A belt conveyor system using the PEI membrane was able to transport Cu2+ ions from one bath to another. In a diffusion dialysis against 1N HCl, the PEI membrane crosslinked rather tightly showed a specific ion-selective transfer character. For example, in Cu2+-Ca2+ system the permeability ratio Pcu/Pca was about 3.8. The selectivity arises from the difference between affinities (extractabilities) of PEI toward metal ions. The selectivity was changed depending on the pH value.

Notes: The pervaporation performances of membranes obtained by radiation grafting of N-vinylpyrrolidone onto poly(tetrafluoroethylene), polyethylene, polybutene, and poly(dimethylsiloxane) films were studied using a water-dioxane azeotropic mixture. The influence of the following parameters was examined: grafting ratios, radiation dose rates, nature of the base films, poly(tetrafluoroethylene) film-making methods, and structural transition. An attempt has been made to interpret the results in terms of variations in the number, size, and density of the grafted domains which form the diffusion paths for the permeating molecules. Based on this interpretation, a general rule is proposed for selecting adpated methods to prepare efficient pervaporation membranes.

Notes: High molecular weight polyisobutylene samples were degraded by milling at 320 K. The degradation process was followed by determining the course of the changes in molecular weight distributions (MWD) that were obtained by gel permeation chromatography. After long milling times degradation stops or at least the rate of rupture becomes extremely small, the molecular weight approaching an apparent minimum value (Mm) of 0.4 × 106. The rate of degradation decreases in the course of the first ½ to 1 hr from an initial value to one constant up to at least 3 hr if the maximum shear rate is higher than about 6 s-1. At lower shear rates the rate of scission is constant from the start. When milling is stopped for 24 hr, high initial rupture rate is observed on resumption of milling at high shear rate, again followed by a drop in rate to the same value as before the interruption. The initial rates are independent of shear rate, whereas the subsequent constant rates are proportional to the rate of shear. These observations are discussed in terms of an equilibrium between the formation of multimolecular “rheological units” and the tendency, due to thermal motion, to form a homogeneous entanglement network. The MWDs are compared with those calculated from a model based on a given relation between probability of scission (P) and molecular weight and an assumed probability distribution (Q) of rupture site along the length of the polymer moelecules. The observed MWDs are incompatible with those calculated from models in which Mm = 0 or in which breakage near the center of the molecule is favored. They agree rather well with computed MWDs based on the assumptions that P ∞ MW and Q is the symmetrical beta function between points along the molecule Mm removed from the ends, where Mm is (0.4-0.5) × 106. The mechanism of rupture appears to be the same for low and for high shear rates.

Notes: The kinetics of polycondensation and copolycondensation of terephthaloyl chloride with numerous bisphenols in α-chloronaphthalene solutions were examined. The values of activation energy E of the polycondensation processes were calculated. Isokinetic temperatures for different systems of monomers were determined. A series of syntheses of copolyesters at isokinetic temperature and other temperatures was carried out. The products obtained during the reaction were examined. It was found that at isokinetic temperature the composition of the products is independent of the extent of reaction, whereas at other temperatures it depends on the reactivity ratio of monomers used, as well as on the extent of reaction.

Notes: The state of cellulose as defined by its crystallinity, grinding, and average degree of polymerization (D.P.) highly influences the grafting yield. Grinding of cellulose with a Wiley mill results in decreased grafting, while grinding with a ball mill or treatment with ethylenediamine, both of which lead to decrystallization of cellulose, nearly inhibits the grafting reaction from taking place. On the other hand, decreased D.P. leads to increased grafting yield. The governing factor being attributed to the specific surface of the cellulose. Increased specific surface, as decreased D.P., brings about an increase in the active sites formed on the cellulose and hence an increase in the grafting yield. However, this occurs up to a limit beyond which further increase in the specific surface, respectively, the formed active sites, as grinding with a Wiley mill and decrystallization, brings about termination reactions through disproportionation and coupling of the exceedingly increased free radicals, and hence grafting is decreased or nearly inhibited. Drying of cellulose at 105°C resulted in decreased grafting yield. This was attributed to condensation of the cellulose structure. It has been also found that the grafting yield is influenced by the type and origin of cellulose whose reactivities differ for different monomers.

Notes: The viscoelastic melt behavior of poly(2,6-dimethyl-1,4-phenylene oxide) (PPOPPO is a registered trademark of the General Electric Company. resin), high-impact polystyrene (HIPS), and a 35-65 blend of these polymers has been characterized by measuring the steady shear viscosity and primary normal stress difference and the dynamic storage and loss moduli as functions of shear rate or frequency and temperature. Time-temperature superpositioning was used to generate master curves of each type of data for a reference temperature of 260°C. This procedure required five different empirical shift factors for each material. These shift factors show large differences between PPO resin and HIPS and exhibited large deviations from the WLF equation with universal constants. This result suggests that the temperature dependence of the relaxation processes in PPO resin is significantly different from the temperature dependence of HIPS relaxations. Flow activation energies computed from the viscosity data for PPO resin are much higher and more shear sensitive than those calculated for HIPS. The computed relaxation spectra clearly display the effect of long-time relaxation mechanisms associated with PPO molecules when compared to HIPS. The 35-65 blend exhibits general rheological compatibility with material parameters and responses intermediate between PPO resin and HIPS. This result is indicative of a high degree of segmental mixing for the two components in the blend.

Notes: The study of the adsorption of an organosiloxane onto a fumed silica was undertaken in order to improve our knowledge of the reinforcement of silicon rubbers by silica. IR and gas-phase chromatography techniques were used to characterize the adsorption of octamethyltetracyclosiloxane. At room temperature, the occurrence of hydrogen bonding between the solute and the adsorbent was shown. The amount of material adsorbed according to this mechanism was shown to be strongly dependent on temperature. The heats of adsorption at various covering ratios were calculated from the isotherms measured at temperatures close to 150°C.

Notes: The tensile mechanical properties of diethylenetriamine (DETA)-cured bisphenol-A-diglycidyl ether (DGEBA) epoxies prepared from 9, 11 and 13 phr DETA are reported as a function of thermal history, strain-rate and test temperature. These epoxies exhibit macroscopic yield stresses and 〉10% ultimate elongations. The mechanical properties of these epoxies exhibit a free-volume dependence as a function of thermal history. Annealing below Tg causes an increase in the macroscopic yield stress and a decrease in the ultimate elongation, whereas quenching from above Tg lowers the yield stress and increases the elongation. These mechanical property modifications are shown to be reversible with reversible thermal-anneal cycles. The activation volumes associated with Eyring's theory for stress-activated viscous flow for the DGEBA-DETA epoxies are within the range of values (9-12 nm3) reported for noncrosslinked polymers. These observations suggest that the DGEBA-DETA epoxies are not as highly crosslinked as would be expected from normal addition reactions of epoxide groups with primary and secondary amines. The formation of lower crosslink density networks is discussed in terms of potential chemical reactions.

Notes: The base-catalyzed sulfur-1,2-ethanedithiol reactions appear to follow pseudo first-order kinetics as determined by TGA. The activation energy has been determined to be 26.1 kcal/mol with either cyclo-octameric or catenapolymeric sulfur.

Notes: The aromatic polysulfone poly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyleneiso-propylidene-1,4-phenylene) (I) showed no change in flexural yield strength after doses of γ-radiation up to 600 Mrad in vacuum at 35,80, and 125°C (Tg = 190°C)). However, the flexural strength decreased markedly with doses above 100 Mrad on irradiation in air, to 40-60% of the initial value after 200-400 Mrad, depending on the sample and the irradiation conditions. Chain crosslinking was predominant over scission for irradiation in vacuum at all temperatures; (G(X), G(S), and G(S)/G(X) increased with the irradiation temperature, but G(S)/G(X) decreased to zero above Tg. Poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene) (II) behaved similarly, except that the flexural strength was found to be very dependent on the thermal treatment of the sample. This polymer showed a remarkable retention of its mechanical properties on irradiation up to 200°C (Tg = 230°C) in the absence of air, the flexural strength being retained up to 500 Mrad. Radiation annealing occurred at 35°C in vacuum and air and combined radiation and thermal annealing at 125 and 220°C. Progressive removal of surface layers from flexural test bars of I irradiated in air showed that the decrease in flexural strength with dose could be explained by a decrease in the molecular weight towards the surface resulting from radiation-oxidation reactions.

Notes: The effect of extent of degradation of poly(m-N,N-dimethylaminostyrene) on the quantity and molecular weight of the residue is described. Comparative studies on polystyrene and poly(m-N,N-dimethylaminostyrene) have indicated significant differences between the two polymers. Torsional braid analysis has shown the crosslinked residue from poly(m-N,N-dimethylaminostyrene), produced at temperatures greater than 150°C, to be obtained on the heating cycle rather than the cooling cycle, and mechanisms to account for this phenomenon are discussed. The physical form of the residue has been found to be molecular weight dependent, and this has been discussed in terms of the differences in “melt temperature” relative to the “onset temperature” for crosslinking. The quantity and composition of the fraction volatile at pyrolysis temperature, involatile at ambient temperature are discussed. The components of this fraction were identified by GPC and mass spectrometry and include oligomers containing the secondary amino function. Mechanisms involving N-alkyl and N-aryl scission are proposed to account for the observed products.

Notes: The technique for staining unsaturated additives within cotton fibers reacts osmium tetroxide with a sorbyl moiety which has been attached to the cellulose chain. Resulting electron micrographs indicate that contrast is considerably enhanced. Measurements of fibrillar size averaged 0.30 nm, closely approximating the values in the literature.

Notes: Zeta potential measurements by the streaming current method were performed on pulp (DP) fibers with or without irreversibly adsorbed monolayers of cationic polyelectrolyte. Factors affecting the electrokinetic properties of these fibers, such as the amount of adsorbed polymer, the polymer molecular weight (Mn 50,000 and 200,000), ionic strength (10-5 ∼ 10-2M KCl), and the pH of the streaming medium (KCl solution), were examined. As the amount of adsorbed polymer increased, the negative zeta potential of the fibers decreased until the polarity of the zeta potential was reversed to the positive side. A marked change in the value of zeta potential was not observed when the formation of the saturated monolayer was completed. The zeta potential also varied in proportion to an increase in the amount of polymer adsorbed. Experimental results are interpreted with reference to the origin of the surface charge, the amphoteric nature of the surface, the modes of adsorption, and the adsorbed polymer chain configuration. Possible effects of the adsorbed monolayer formation on the structural change of the electric double layer at the fiber surface are discussed. It is concluded that the formation of a monolayer of cationic polyelectrolytes on the negatively charged cellulose fibers under the condition of k1 〉 k2 (part I) provides a means to arbitrarily control the charge of the fibers until formation of a saturated monolayer.

Notes: A strong acid ferromagnetic cation-exchange resin based on styrene divinylbenzene polymer has been prepared and characterized.

Notes: The constants a,b of the equation log M̄n = a - b log [lim (ΔR/c)] in benzene and chloroform were obtained at 25, 37, and 45°C for the Knauer vapor osmometer and compared with those published by Brzeziňski et al. for the Mechrolab 302. It was found that the constant b in the above solvents had identical values, depending on the temperature used. The value of a depends on the resistance of the thermistors. The procedure used for obtaining lim (ΔR/c) from the concentration dependence is discussed. Comparison of the limiting slope dependence and the gradient dependence reveals the error of the zero point, which cannot always be eliminated by employing a procedure by Glover.

Notes: Grafting of 2-methyl-5-vinyl pyridine (MVP) onto partially carboxymethylated cotton having 6 meq COOH/100 g cellulose (PCMC) was effected by a Fe2+-H2O2 redox system. Different graft yields were obtained by varying MVP concentration from 10 to 100 wt % PCMC. In a subsequent step these graft copolymers were treated with epichlorohydrin. Dyeing of untreated cotton, PCMC, PCMC grafted with MVP, and epichlorohydrin-treated poly(MVP)-PCMC graft copolymers was carried out at room temperature (27°C) for varying lengths of time (2.5-60 min) in the absence of alkali catalyst or any other additives. Three reactive dyes, Procion Red M-GS, Procion Orange Brown H-2GS, and Remazole Brilliant Blue; a direct dye, Orangé Solophényle 2RL; and an acid dye, Erio Blue Marine 2GR were used at a concentration of 2% by weight of material. It was found that none of the three reactive dyes or the acid dye interacts with untreated cotton or PCMC. In contrast, the direct dye did. PCMC grafted with MVP, on the other hand, showed a substantial extent of dye exhaustion regardless of the dye used. After-treatment of poly(MVP)-PCMC graft copolymers with epichlorohydrin significantly enhanced the extent of dye exhaustion. The latter reacted almost 100% with all the dye examined, irrespective of the graft yield, which varied from 1.6% to 63%. Dyeings for reactive dyes withstood soaping for 1 hr at boil and extraction with 50% dimethylformamide, whereas dyeings for the direct dye and the acid dye failed to do so. It is believed that the presence of pyridine moieties in the graft act as an internal, built-in catalyst for expediting the reaction of reactive dyes with cellulose hydroxyls and behave as a weak base capable of salt-linkage formation in case of the acid and direct dyes.

Notes: A new method is developed to estimate the reactivity ratios from composition-conversion data based on nonlinear regression. Previously published experimental data for the copolymerization of acrylic acid and acrylamide are analyzed by the new method and the results compared to those reported by the original investigators. Composition-conversion data were collected for this copolymerization system at intermediate conversion levels and over a limited range of compositions. Values for the reactivity ratios at 40°C were obtained from these data by the new algorithm and compared to the literature values.

Notes: It has been shown that the pyrolysis of cellulose at low pressure (1.5 Torr) can be described by a three reaction model. In this model, it is assumed that an “initiation reaction” leads to formation of an “active cellulose” which subsequently decomposes by two competitive first-order reactions, one yielding volatiles and the other char and a gaseous fraction. Over the temperature range of 259-341°C, the rate constants of these reactions, ki (for cellulose → “active cellulose”), kv (for “active cellulose” → “volatiles”), and kc (for “active cellulose” → char + the gaseous fraction) are given by ki = 1.7 × 1021e- (58,000/RT) min -1, kv = 1.9 × 1016e- (47,300/RT) min-1, and kc = 7.9 × 1011e- (36,600/RT) min-1, respectively.

Notes: A styrene-butadiene-styrene (20-60-20) linear block polymer was epoxidized in toluene and cyclohexane solutions with peroxyformic acid generated in situ. The epoxidized polymer, containing about 8% oxygen, exhibits greatly improved resistance to ASTM oils. It can be readily compounded with carbon black, and the unvulcanized stock is found to be comparable to vulcanized polychloroprene and nitrile rubber in tensile strength and resistance to ASTM oils and certain chemicals.

Notes: The useful life of a material depends on its environmental exposure. The diglycidyl ether of bisphenol A (DGEBA) cured with trimethoxyboroxine (TMB) was evaluated under various aging conditions. For isothermal aging, the main factor controlling weight loss appeared to be related to the diffusion of the degradation products (Eact = 22.1 kcal/mole). Chemical decomposition kinetic parameters were obtained using vacuum thermogravimetric analysis (TGA) on powder samples. The thermal decomposition activation energy and the reaction order of cured DGEBA were 37.5 kcal/mole and 1.05, respectively. The hydrolytic aging of this material was also kinetically analyzed, and it was concluded that the weight change was controlled by both water diffusion into the sample and diffusion of hydrolysis products from the sample. During hydrolytic aging below the glass transition temperature, the specimens gained weight up to 0.05 g based on 1-g unaged cured resin and then leveled off. At higher temperatures, the specimens initially gained weight and then began to lose weight, reaching a constant weight gain. The activation energies for water diffusion into the cured resin are 19.5 kcal/mole at temperatures above Tg and 21.5 kcal/mole at temperatures below Tg. The main hydrolysis product was boric acid from reaction of the boroxine ring with water. The time-temperature superposition principle was used for the weight loss study on isothermal and isothermal hydrolytic aging. The scale factor in this approach was found to be the ratio of the diffusion coefficient at the temperature of interest to that at a reference temperature.

Notes: Mechanical properties of electron beam-cured films were studied as a function of oligomer structure and monomer diluent. In films cast from polyester acrylourethane oligomers, increasing the chain length between the two acrylate groups on each end resulted in a decrease in breaking strength from 7000 psi to 1000 psi in Young's modulus from 200,000 psi to 700 psi, and in glass transition temperature from 50 to -25°C, while the ultimate elongation increased from 20% to 210%. These properties were virtually independent of dose above 1 Mrad. The elongations were compared with literature values at equivalent degrees of crosslinking and found to fall within the range, but on the low elongation side of the distribution. It was speculated that the crosslinks' functionality would equal the average degree of polymerization of the double bond at each end of the oligomer, resulting in multirayed, star-shaped crosslinks with less flexibility than those with the usual functionality of 3 or 4, and methods for reducing this functionality were investigated. Addition of active monomers effected only minor change, but diethylaminoethyl acrylate was found to be very helpful in increasing the extensibility of these films considerably. This behavior can be explained by assuming that this monomer has a significant chain transfer constant, which should reduce the degree of polymerization of acrylic endgroups, producing a looser structure.

Notes: PMR spectroscopy and lanthanide shift reagents were used to determine sequence distribution of units of poly(dimethyldian-phenolphtalein)terephthalate. The calculated values of degree of randomness confirm the theory that the copolyester obtained at the isokinetic temperature (200°C) has random distribution of comonomer units and copolyesters obtained at temperatures above and below this temperature have a tendency to form block units along the macromolecular chain.

Notes: Polyimide fibers were prepared by wet spinning of poly(p,p′ -diaminodiphenylmethanepyro-mellitamic acid). Density measurements and x-ray diffraction studies were carried out to study the structure of the resultant polyimide fibers. Polyamic acid as well as undrawn polyimide fibers were essentially amorphous with two amorphous haloes. Hot drawing of the fibers at 300°C resulted in increase in crystallinity, and a simultaneous decrease in density also took place. X-ray data revealed that meridional reflections correspond to the repeat unit length in the fiber. Scanning electron micrography studies indicated that polyamic acid fibers prepared by a wet-spinning technique developed voids during spinning which increased on cyclodehydration to the polyimide state. Hot drawing of fibers resulted in enlargement of these voids. However, a highly fibrillated structure was developed during drawing which could account for the strength of the fibers.

Notes: An experimental investigation on the aqueous polymerization of acrylamide with potassium persulfate initiator is reported. Molecular weight averages were measured by viscometry. Non-Newtonian effects were accounted for by extrapolation to high shear rates where the polymer solutions approximated Newtonian behavior. Values for the transfer constants to the acrylamide monomer and to the persulfate initiator were estimated at 25 and 40°C and compared to literature values.

Notes: The iodine-initiated, solid-state copolymerization of the tetraoxane-1,3-dioxolane-methylal system has been studied by measuring the molecular weight distribution of the copolymer. The molecular weight distribution of the copolymer is found to be strongly dependent on the addition method of the 1,3-dioxolane-methylal solution to tetraoxane. The copolymer obtained by the one-addition copolymerization has a molecular weight distribution curve that shows a very broad distribution, with a discernible shoulder; and the copolymer obtained by the continuous-addition copolymerization has a very sharp curve. Particle size of the copolymer also influences the molecular weight distribution. For the one-addition copolymerization, the larger the particle size of the copolymer, the broader the molecular weight distribution. For the continuous-addition copolymerization, however, the molecular weight distribution is nearly constant regardless of particle size. The dependence of the molecular weight distribution on the polymerization time and the concentrations of iodine, 1,3-dioxolane, and methylal is discussed in detail. These results suggest that this copolymerization system is characterized by a reaction that proceeds from the surface to the center of the tetraoxane crystals.

Notes: Starch xanthate with degrees of substitution (D.S.) ranging from 0.12 to 0.56 reacted with vinyl monomers (acrolein, acrylamide, acrylic acid, acrylonitrile, methyl acrylate, or styrene) and hydrogen peroxide to form aqueous gels of starch-polyvinyl monomer graft copolymer. The same reactions conducted in a rubber latex medium resulted in a self-acidifying, self-heating, and self-foaming coagulation to give a foam rubber. Such products were formed from several synthetic latices (NBR, SBR, polyisoprene, and polychloroprene types) and natural rubber latex; noted for each were the effects of the D.S., of monomer and peroxide concentrations, and of starch:elastomer ratios. The dried foams were evaluated by standard strength tests. Foam rubber of acceptable extensibility and enhanced tensile strength (up to 110 psi) was obtained with 0.12-0.15 D.S. xanthate and with proper balance of vinyl monomer, peroxide, and starch:elastomer ratio. Resilience was fair to good, but compression set was rather poor compared to most foam rubbers of general use.

Notes: Styrene (St) was polymerized in the presence of poly(p-nitrophenyl acrylate) (PNPA) with azobisisobutyronitrile as an initiator to prepare graft copolymers through the chain transfer reaction of growing polystyrene (PSt) radicals to the aromatic nitro groups on PNPA. The maximum number of branches attained was 16.4 (Pn of PNPA was 1780), which corresponds to 108 monomer units per PSt branch. This is far less than the value of 43, previously obtained for poly(vinyl p-nitrobenzoate) as a trunk polymer. Therefore, several model compounds for trunk polymers were prepared, and the chain transfer constants of PSt radicals to these model compounds were determined. As a result of the Hammett plot, it is concluded that higher electron attracting property of the substituents increases the reactivity of nitro groups to the growing PSt radicals, resulting in more highly branched graft copolymers.

Notes: The effects of molecular structure and cooling conditions on the severity of draw resonance was investigated by carrying out carefully controlled melt spinning experiments. For the study, two types of polymeric materials were used: one which exhibits viscoelastic behavior (high-density polyethylene, polypropylene, and polystyrene), and the other which exhibits almost Newtonian behavior [nylon-6 and poly(ethylene terephthalate)]. In order to investigate the effect of cooling on the severity of draw resonance, different methods of cooling the molten threadline were employed. In one set of experiments, isothermal chambers of various lengths (3, 6, and 12 in.) were attached to the spinnerette face, so that the molten threadline, upon exiting from the spinnerette, began to cool in the ambient air only after it had passed through the isothermal chamber. This method of cooling is called “delayed cooling,” providing both an isothermal region (inside the isothermal chamber) where only stretching occurs, and a nonisothermal region (outside the isothermal chamber) where both stretching and cooling occur simultaneously. In other experiments, the temperature profile of the molten threadline was controlled by adjusting the temperature of the heated chamber. This method of cooling provides a gradual drop of the threadline temperature, compared to the more sudden drop when spinning into a cold environment provided at the spinnerette exit. The severity of draw resonance was recorded on movie film, and the thread tension was measured with a low-force load cell transducer and recorded on a chart recorder. The temperature of the threadline along the spin direction was measured using a fiber optical probe attached to a Vanzetti Infrared Thermal Monitoring System (Model TM-1). It was found that the severity of draw resonance depended on the molecular structure and the way the molten threadline was cooled. Of particular interest is the observation that, for the viscoelastic materials investigated, cooling destabilized the molten threadline outside the isothermal chamber. This gave rise to more severe resonant behavior, at and above the critical draw-down ratio, in contradiction to the theoretical prediction by Fisher and Denn. It was observed, also, that the elasticity of the materials tended to destabilize the molten threadline (i.e., it increased the severity of draw resonance), again in contradiction to the theoretical prediction of Fisher and Denn. It is believed that morphological changes of polymers may play an important role in the occurrence of draw resonance when a melt threadline is stretched under cooling. Our study indicated that a good understanding of draw resonance of viscoelastic fluids requires more careful study than the classical hydrodynamic stability analysis reported by Fisher and Denn. They based their analysis on several convenient and yet unjustified assumptions, and solely on phenomenological considerations. We suggest that future theoretical analysis of draw resonance be carried out by considering a fluid model with a nonlinear memory function in order to properly account for the deformation history of the fluid, and the relaxation and cooling processes in the die swell region and the region below it.

Notes: The pulsed field gradient spin echo method was used to measure the diffusion of ten paraffin hydrocarbons in several uncrosslinked rubbers at 51°C. We obtain various free volume parameters from the concentration dependences, establish the approximate proportionality of the translational friction coefficient to paraffin molecular weight, and confirm the equal intrinsic efficiency of the diffusion mechanism of decane and hexadecane in rubbers.

Notes: Uniform dispersions of high-molecular-weight poly(dimethylsiloxane) (PDMS) in a matrix of poly(styrene-co-acrylonitrile) (SAN) are prepared where the degree of crosslinking in the elastomer and its extent of grafting to the SAN matrix are controlled. This gives an impact resistant plastic at ambient and low temperatures which is resistant to outdoor exposure. The Tg of PDMS is shown to be greatly reduced when grafted to the SAN matrix. Plots of impact resistance versus shift factor aT of the elastomer added for toughening coincide for PDMS and polybutadiene over a 150°C temperature range.

Notes: Compositions for good antifogging and mar-resistant coatings were investigated. A mixture of hydrolyzed aminoalkylalkoxysilane and hydrophilic vinyl monomer was the best combination. Control of suitable viscosity for coating was carried out conveniently by irradiation. The prepolymer was coated and cured by heating to form an antifogging membrane on various base materials such as inorganic glass, CR-39 resin, and poly(methyl methacrylate). These conditions were studied in relation to some physical properties of the membrane. It was found that antifogging and mar-resistant properties were inconsistent in many cases. A possible way to achieve the best balance between the two properties is discussed.

Notes: Sisal (Agave sisalana) fibers were graft copolymerized with certain vinyl monomers (methyl acrylate, ethyl acrylate and methyl methacrylate) using gamma irradiation and ceric ammonium nitrate as initiation techniques. Examinations of the surface topology and the internal structure of the grafted fibers made by scanning electron microscopy. The results derived from the SEM observations on transverse sections of the grafted fibers were supplemented by information obtained by polarized light microscopy. Polymer was deposited not only on the surface of the fiber substrate, but also in the lumen, the middle lamellae, and throughout the cell wall network of the multicellular aggregates. The degree of polymer inclusion in the lumen (which is the most conspicuous of all the available internal sites) was found to depend on the percentage graft copolymer add-on, as well as on the previous history of the fiber (natural or chemically modified). The mechanical properties of the grafted fibers were investigated (by means of an Instron tensile tester).

Notes: Photoinitiated, free-radical reaction of cotton fabric with vinyl phosphonate oligomer (molecular weight 500-1000) and N-methylolacrylamide monomer from aqueous solutions to form copolymer gave a textile product that had flame resistance (FF 5-74 test). The initiating free radicals were formed on the cellulose molecule when cotton fabric was exposed to ultraviolet radiation. The effects of wavelengths of ultraviolet radiation (254, 300, and 350 nm), reaction time (0-9 ksec), solids in solution (10%-60%), atmosphere (air, nitrogen, and oxygen), and oligomer-to-monomer concentration (1:0.00 to 1:1.20 mole ratio) on efficiency of monomer and oligomer conversion to copolymer (maximum efficiency 70%-80%) were determined. Evaluation of the flame resistant cotton fabric by transmission electron microscopy showed deposits of copolymer throughout the cross sections of the fibers. However, scanning electron microscopy and energy-dispersive x-ray analysis showed that copolymer and phosphorus tended to be more concentrated between and on the surfaces of the fibers.

Notes: Copolymerization of ethylene chlorophosphonite (ECP) with 2-phenyl-1,3-dioxolane (PhD) and the flame-retardant effect of the copolymer on polyester fabric were investigated. (1) Copolymerization occurred without added catalyzer. The number-average molecular weight ranged from 600 to 1000. 1H-nmr and ir spectra for the copolymers showed that their structures varied depending on feed composition (ECP/PhD ratio): ECP/PhD less than or equal to 1 yielded an alternating copolymer having the structure and at ECP/PhD ratios greater than 1, some insertion reaction of ECP into polymer I occurred. (2) Selectivity of flame retardation could be observed. The copolymer with structure I was an effective flame retardant for polyester fabric but useless for cotton fabric. Its effectiveness in polyester fabric was superior to that of TBPP.

Notes: The accuracy of the parallel-plate approximation to represent various viscous flows of non-Newtonian fluids between coaxial cylinders is investigated. Four types of flow are considered: tangential drag flow, tangential pressure flow, and axial pressure flow. The solutions for flow between parallel plates are compared with the exact solutions, and the errors are plotted against radius ratio for a number of values of the power-law index to provide an indication of the range of usefulness of the parallel-plate analogy.

Notes: The maximum crosslink density for the dioxime-butyl vulcanizate was obtained at equimolar quantity of the dioxime and red lead. The formation of each quinoid crosslink required about 1.25 molecule of p-quinone dioxime dibenzoate. The vulcanizates consisted mainly of the anil-type crosslink. It was estimated that about 20% of the combined dinitro compounds was wasted in the form of the pendent groups. The vulcanization mechanisms are also discussed.

Notes: The possibilities of comparing the GPC curves of two or more polymers were studied, and the method of “distinguished points” (DPs) is suggested for this purpose. The features of these DP values as random variables were investigated. According to the experimental results they meet the requirements of the statistical tests applied in this text. In order to indicate the significant deviation or the agreement of the DP values of GPC curves of two polymers, the sequential U and t tests are suggested, because with these methods the number of the necessary parallel measurements is considerably decreased, and one can also decide on the magnitude of the variation on must be able to detect, while in the case of more than two polymers the methods of the analysis of variance can be utilized. The molecular weight ranges in which significant differences occur can also be determined. The described methods were tested by materials of known molecular weight distributions.

Notes: Thermogravimetric (TGA) and infrared (IR) analyses were used to determine the thermal stability of a polymer system consisting of styrene-acrylonitrile-acrylamide-trimethylolpropane trimethacrylate. This study indicates that increases in curing temperature and the use of two initiators with different activities decreases the percentages of unreacted monomers. This increases the thermal stability of the polymer. To prove this, dynamic and isothermal TGA were used. The change in typical functional groups found by IR spectra also confirms this observation.

Notes: The flow behavior of four cellulose acetate-acetone solutions varying from 20.00% to 28.18% solids concentration was observed using flow visualization techniques at 24°C with an industrial-type dry spinning system. Fibrous particulate matter entertained in the solutions and crossed polars revealed the streamlines and the birefringence due to flow in glass spinnerets. The streamlines of the four solutions were radially convergent at all obtainable throughputs. The crossed polars revealed a cone of birefringence with the order of the interference colors decreasing upstream of the capillary inlet. The intensity and extent of birefringence varied somewhat with concentration and throughput. Except for kneeing, the emerging extrudates were undeformed. The kneeing was not a result of flow instability a t the capillary inlet but was due to another, undetermined instability. A separate study of the kneeing revealed both a concentration dependence and hysteresis. The birefringence of the emerging extrudates was a function of both concentration and throughput, and it yielded some information about the structure of the solutions.

Notes: The influence of drawing and molecular weight in a narrow range on the several structural-mechanical properties of acrylic fibers have been investigated. Drawing of fibers (λ = 3x-6,5x) leads to a considerable increase of tenacity. These data were explained with the orientation and perfection of structure. It was found that the molecular weight in closer range influences the density, perfection of structure, and the stability of fibers to repetitive deformation. The results show that the diversions of the average molecular weight, in the manufacture of commercial acrylic fibers, must be negligible.

Notes: The compressive creep rate of polyurethane foams was found to be a complex function of deflection and time. The complexity has been shown to be related to the buckling of the cell struts as the foam is compressed. Of the parameters normally varied in the foam formulation, both the polyol molecular weight and the water content of the foam formulation seemed to have a measureable effect on the creep rate.

Notes: A series of new acetylene-terminated phenylquinoxaline oligomers and diacetylene compounds have been prepared utilizing 4-(3-ethynylphenoxy)benzil. The amorphous materials with molecular weights from 500 to 1460 exhibited softening in the 25-160°C range with a strong polymerization exotherm reaching a maximum at 270-290°C. The addition nonvolatile cure provides materials which show excellent thermoxidative stability and processability for high-temperature matrix and adhesive resins.

Notes: The ionic crosslinking of poly(acrylic acid) for dialysis and reverse osmosis applications has been studied. A new dry technique has been developed that is faster than the wet technique reported in the previous paper to synthesize aluminum/poly(acrylic acid) membranes. It is based on casting a solution containing both the aluminum salt and the unneutralized poly(acrylic acid) (PAA) and subjecting the cast film to a heat treatment (curing step) to promote ionic crosslinking. Postcuring treatment in nonsolvents for PAA such as acetone induced structural modifications in the membrane. Membranes with optical clarity ranging from colorless and transparent to white and opaque were obtained and were characterized by their water and aluminum contents. Transport properties of these membranes were investigated and indicated a selective rejection of ionic solutes such as NaCl compared to organic solutes such as ethylene glycols. Typical results for reverse osmosis under static conditions at fluxes of 1250 g/hm2 (0.75 U.S. gallons/ft2-day) gave rejections of 85% for a feed of 0.1% (by wt.) NaCl at 600 psi. Much lower rejection (28%) for ethylene glycol suggests the possible use of these membranes in the fractionation of mixtures of ionic and nonionic solutes by reverse osmosis.

Notes: The porosity of suspension copolymers of methacrylic acid (MA) and divinylbenzene (DVB) has been studied. The copolymers were prepared both directly from monomer blends and with toluene or n-octane as inert diluents. The pore volume and radii of pores were larger for copolymers containing 5.0% of DVB than those for copolymers containing 9.1% of DVB. The volume and radii of pores increased with increasing diluent content, but the effect of n-octane was more pronounced than that of toluene. Based on considerations of monomer reactivities and copolymer-diluent and copolymer-unreacted monomer interactions, the following model of structure of MA and DVB copolymers has been proposed: The copolymers are composed of microgels interconnected into a rigid skeletonlike structure, surrounded by lightly crosslinked and unentangled poly(methacrylic acid) chains.

Notes: The breaking mechanism of nylon-6 yarn is investigated, and the breakage of the yarn under simple tensile loading conditions is compared to that of a filament caused by the same loading. The simple model yarn consisting of seven filaments was prepared for this purpose. The yarn was ruptured at a low rate of extension, and the fracture morphologies of the filaments in the yarn were inspected by a scanning electron microscopy. These morphologies are clearly different from those of the filaments broken individually under the same testing conditions used for the yarn. Various kinds of appearances are obtained in the yarn, for example, a large V-shaped notch is observed, the controlled ductile tearing region is developed across the filament at a large angle to its axis, and the ruptured end is expanded into a plane which is perpendicular to its axis. These causes are discussed in detail to understand the breaking mechanism of the yarn.

Notes: The curing reaction of a thermoset polyester was investigated by using the isothermal and dynamic techniques of differential scanning calorimetry (DSC). The heats of reaction (at different curing temperatures) and a kinetic expression of the crosslinking reaction are presented and compared to the results of the previous studies. The proposed kinetic model can be utilized to obtain the rates of heat generation and the extent of cure at different cure temperatures and time. The overall activation energy of the curing reaction was calculated on the basis of experimental data as 17.0 kcal/mole and the overall reaction rate constant as 2.60 × 109 exp (-17,000/RT) min-1.

Notes: Transport properties were determined for various Loeb-type membranes which exhibit strong structure differences from one to another. Using linear relations of thermodynamics of irreversible processes for the homogeneous ones, correlations were found between the specific transport coefficients and the states of water in the membrane medium. In the case of heterogeneous membranes a schematic multilayer model, using in an appropriate way Darcy's law, was worked out in accordance with electron micrographs of membrane cross sections. It enables us to correlate the membrane hydraulic permeability with the relative extent of four typical structures A, B, C, and D. In addition, this model provides both the hydraulic specific permeabilities of these types of structure and their hydration characteristics.

Notes: The reaction kinetics of emulsion polymerization of vinyl acetate (VAc) monomer have been studied by using intermittent γ radiation. The purpose of this technique is to take advantage of the poly merization reaction which still continues after the radiation production has been stopped, as expected by the Smith-Ewart rate theory. Tween 20 (polyoxyethylene sorbitan monolaurate), was used as the emulsifier. The polymer conversion was determined by using the dilatometric method. The polymerization rate Rp decreased with increase in emulsifier content. The Smith-Ewart rate theory cannot explain the experimental evidence satisfactorily. The average polymerization rate Rp between 20% and 80% conversion is a function of irradiation dose rate and can be written $$ \overline {R_p } = a_1 I^{a_2 } $$ where a1 and a2 is a constant in which the value depends on the emulsifier content in the emulsion and I is the irradiation dose rate.

Notes: Homopolymerization and copolymerization of α,β,β-trifluoroacrylonitrile (FAN) with γ-olefins were carried out in bulk by γ-ray irradiation at 25°C. FAN gives very small quantities of brown and greasy low molecular weight polymer. Cyano groups in FAN polymer were found to be readily hydrolyzed to acid amide groups in the atmosphere. FAN was found to copolymerize with ethylene, propylene, and isobutylene via a radical mechanism to form equimolar copolymers in a wide range of monomer compositions. The polymerization rate increases linearly with FAN fraction in the monomer mixture. These copolymers are also hydrolyzed in the atmosphere, and the hydrolysis proceeds with more difficulty for the copolymer with higher α-olefin. The reactivity ratios r1 (FAN) and r2 (α-olefin) were determined to be 0.01 and 0.12 for the FAN/ethylene copolymerization and 0.01 and 0.07 for the FAN/propylene copolymerization. These results confirm that an alternating copolymerization takes place in the FAN/α-olefin system.

Notes: The extent of DVB grafting onto cellulose fabric increases with total gamma radiation dose up to 10-15 kGy while it decreases with the radiation dose rate. A quantitative analysis of DVB grafting has been attempted by means of IR spectroscopy using the baseline method. Characteristic bands were selected in the spectra of copolymers, namely, the cellulose band at 1160 cm-1 and DVB band at 798 cm-1. The former band decreased and the latter increased with the degree of copolymerization, and the values were in accordance with the calibration straight line. An attempt to graft DVB onto cotton fabric previously grafted with styrene showed greater extent of copolymerization than with pure fabric.