Showing papers on "Polymer published in 1970"
TL;DR: Equilibrium absorbance-temperature transition, analytical buoyant density, and circular dichroism studies are reported on a variety of high molecular weight doublestranded DNA polymers containing defined repeating nucleotide sequences, providing further evidence that the structure of a DNA is dictated by its primary nucleotide sequence.
487 citations
TL;DR: In this paper, the authors showed that the protective films formed on Cu by benzotriazole were composed of a highly inert Cu benzotitriazolate (CuBTA) polymer.
347 citations
Patent•
08 Sep 1970
TL;DR: In this article, the authors describe a set of deterministic deterministic polymers, such as POLYMERIC MATERIALS, having a backbone and a backbone connecting different partitions.
Abstract: POLYMERIC MATERIALS HAVING A BACKBONE COMPRISING SEGMENTS CONTAINING POLY(PERFLUOROALKYLENE OXIDE) HAVING THE STRUCTURE -CF2-O-(CF2-CF2-O)M-(CF2-O)N-CF2- POSESSING UNUSUAL LOW TEMPERATURE FLEXIBILITY AS WELL AS GENERALLY GOOD HIGH TEMPERATURE STABILITY AND RESISTANCE TO SOLVENTS. MONOMERIC PRECURSORS AND METHODS OF PREPR ARATION OF SAID PRECURSORS AND POLYMERIC MATERIALS ARE DESCRIBED THE POLYMERS ARE USEFUL AS FILMS, SEALANTS, BINDERS AND AS MOLDED AND EXTRUDED ARTICLES SUCH AS GASKETS, ORINGS, AND HOSE-LININGS FOR CRYOGENIC APPLICATIONS.
326 citations
TL;DR: In this article, a general mechanism of adhesion to hydrophilic mineral surfaces has been devised from a study of silane coupling agents in reinforced plastics, based on which a dynamic equilibrium at the interface allows relaxation of thermal stresses.
Abstract: From a study of silane coupling agents in reinforced plastics, a general mechanism of adhesion to hydrophilic mineral surfaces has been devised. According to this theory, adhesion of polymers to dissimilar surfaces is described as a dynamic equilibrium of making and breaking of adhesion bonds between polymer segments and the surface through the agency of a low molecular weight material—usually water. A dynamic equilibrium at the interface allows relaxation of thermal stresses. Water resistance results from a favorable equilibrium toward bonding through polar groups in the polymer. Silanol groups generally give optimum bonding to hydrophilic mineral surfaces. Such a dynamic mechanism of adhesion not only explains many complex adhesion problems of plastics to mineral surfaces, but also is compatible with the adhesion of ice, barnacles and tooth plaque to surfaces in an aqueous environment and with the requirements for rubber reinforcement by finely divided particulate fillers.
280 citations
Patent•
15 Dec 1970TL;DR: Water-soluble vinyl addition polymers and gums may be rapidly dissolved in water by first dispersing these polymers into a water-in-oil emulsion and then inverting these emulsions in water as discussed by the authors.
Abstract: Water-soluble vinyl addition polymers and gums may be rapidly dissolved in water by first dispersing these polymers into a water-in-oil emulsion and then inverting these emulsions in water. The inversion of the emulsion releases the polymer into water as a solution.
235 citations
TL;DR: In this article, the stability of W/O type emulsions of the cyclohexane-water system stabilized with polyoxythylene nonylphenylether was studied as a function of temperature and of the hydrophilic chain length of the emulsifier.
203 citations
195 citations
TL;DR: In this paper, the pyrolysis of polyfurfuryl alcohol and phenolic polymers leading to glass-like carbon is studied in detail, and the effect of cross-linking of the polymers is shown by the modification with formaldehyde as well as by comparison with oxidized polyphenylene oxide.
TL;DR: Water-insoluble enzymes prepared by covalent coupling to organic polymers have been compared for storage stability under various conditions with enzymes insolubilized by civalent coupling to inorganic carriers including glass, colloidal silica, alumina, and hydroxyapatite.
TL;DR: In the many aromatic fluorophores examined, unlike a few nonaromatic ones, transfer is much decreased or altogether undetectable on excitation at the red edge of the absorption spectrum.
Abstract: Electronic energy transfer among identical molecules has been followed by the depolarization of the fluorescence in concentrated solutions as well as in dimers, polymers, and micelle systems. In the many aromatic fluorophores examined, unlike a few nonaromatic ones, transfer is much decreased or altogether undetectable on excitation at the red edge of the absorption spectrum. The phenomenon is not due to the transfer taking place during a small fraction of the total fluorescence lifetime, nor is it explainable by a decrease in overlap of absorption and emission upon edge excitation.
TL;DR: In this article, the authors describe the properties of linear polyurethanes containing ionic centers at wide intervals, which are heteropolymers having a pronounced segment structure, and their properties are similar to those of crosslinked elastomers.
Abstract: Linear polyurethanes containing ionic centers at wide intervals are heteropolymers having a pronounced segment structure, i.e. ionomers. As a result of interactions between chains (Coulomb forces and hydrogen bonds), their properties are similar to those of crosslinked elastomers. They are strongly associated both in organic and in aqueous solutions. Polyurethane ionomers in polar organic solvents spontaneously form stable aqueous dispersions on addition of water, with the ionomer as the disperse phase. The particle size can be varied between 20 nm and 1 mm.
01 Feb 1970
TL;DR: In this article, a modification of the Good-Girafalco-Fowkes-Young equation is used to calculate nondispersion interactions I SL P at the interface for nine polymeric solids and four polar series of liquids.
Abstract: A modification of the Good-Girafalco-Fowkes-Young equation is used to calculate nondispersion interactions I SL P at the interface for nine polymeric solids and four polar series of liquids. The relationship of I SL P to work of adhesion W A and the spreading coefficient S e is shown. A linear relationship is found to exist between I SL P and γ L P , the nondispersion energy component of the liquids, for the series of polar liquids and the solids studied. The slopes of the I SL P vs. γ L P curves vary depending upon the polymer surface. Intercepts of the curves may be a measure of π s , the reduction in the surface energy of the solid resulting from adsorption of vapor from the liquid.
TL;DR: In this article, a mixture of poly(2,6-dimethyl-1,4-phenylene ether) (PPO) and atactic polystyrene (PS) has been prepared by mechanically mixing powders of the two polymers and subjecting the mixtures to three different thermal treatments.
Abstract: Blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPO) and atactic polystyrene (PS) have been prepared by mechanically mixing powders of the two polymers and subjecting the mixtures to three different thermal treatments. Three different compositions were studied by the dynamic mechanical and DSC techniques. The weight fractions of PPO in the mixtures were 0.25, 0.50 and 0.75. The dynamic mechanical measurements indicate that partial mixing took place but that two distinct phases, one rich in PS and the other in PPO, exist in all the mixtures studied. Each phase exhibits a characteristic relaxation peak associated with the glass transition of that phase. DSC measurements, on the other hand, reveal only a single glass transition apparently characteristic of the PS rich phase in each case. The results indicate that a given type of experiment will indicate compatibility or incompatibility depending upon the size of the molecular process it represents.
TL;DR: Theoretical analyses were made on the size distribution of tubular or helical polymers of globular protein molecules in the reversible polymerization and the relaxation time for such redistribution was estimated as a function of rate constants and the average degree of polymerization under various conditions.
TL;DR: In this article, the effects on partially hydrolyzed polyacrylamide by such parameters as solution salinity, flow rate, rock pore size, polymer molecular weight, mobility reduction, permeability by polymer solution, adsorption, and temperature were examined.
Abstract: Laboratory studies using silica powder, calcium carbonate powder, and crushed Berea sandstone examine the effects on partially hydrolyzed polyacrylamide by such parameters as solution salinity, flow rate, rock pore size, polymer molecular weight, mobility reduction, permeability by polymer solution, adsorption, and temperature. Three different polyacrylamides with varying molecular weights and degrees of hydrolysis were used in the study. The following conclusions were obtained: (1) calcium carbonate appears to have a greater affinity for polymer than does silica; (2) polymer adsorption increases with salt concentration; (3) polymer effectiveness in reducing mobility is greatest at lowest salinity and with highest average molecular weight; (4) as pores become smaller, polymer solutions are more effective in reducing mobility and permeability; (5) polymer solution mobility decreases markedly as the flow rate increases; (6) mechanical degradation begins to occur at very high fluid velocities and is especially pronounced in calcium containing solutions; and (7) increasing temperature seems to have little effect on mobility reduction by polymer within its range of thermal stability.
TL;DR: In this paper, the authors investigated the Crystallization kinetics of molten polyethylene subjected to a constant shear stress and showed that the rate of crystallization depends on the difference of entropy (Δs) between the crystalline and molten states.
Abstract: The Crystallization kinetics of molten polyethylene subjected to a constant shear stress were investigated theoretically and experimentally. The rate of crystallization depends on the difference of entropy (Δs) between the crystalline and molten state. The constant shear stress in the melt decreases Δs causing an abrupt increase in the rate of crystallization and a decrease of the thickness of the folded-chain lamellar crystals.
TL;DR: Theoretical expressions derived previously for molecular size distributions in multichain polymers are applied to binary silicate melts in this article, which is an extension of a previous approach which w...
Abstract: Theoretical expressions derived previously for molecular size distributions in multichain polymers are applied to binary silicate melts. The treatment is an extension of a previous approach which w...
TL;DR: In this paper, the number of surface groups as determined by conductometric titration of the latex, plus the number buried within the particle, was less than the expected value of two per polymer molecule.
Abstract: Solute electrolyte and adsorbed emulsifier can be removed by ion exchange from polystyrene latices prepared with persulphate initiator. Rigorous purification of the ion-exchange resins is necessary to avoid contamination by leached polyelectrolytes. These ion-exchanged latices are stabilised by strong acid surface groups - sulphate end-groups of the polymer molecules. The number of surface groups as determined by conductometric titration of the latex, plus the number buried within the particle as determined by conductometric titration of the polymer in solution (or by X-ray fluorescence), is less than the expected value of two per polymer molecule. The other end-groups are shown to be hydroxyl groups by oxidation to the carboxyl form followed by ion exchange and titration. The total number of end-groups thus determined is close to two per molecule. As the pH of the polymerisation medium is decreased, the proportion of hydroxyl end-groups increases and that of the sulphate end-groups decreases. No carboxyl groups are detected in ion-exchanged latices prepared in a nitrogen atmosphere, independent of the nature of the emulsifier. The dye partition method gives end-group concentrations that are far lower than those determined by titration or X-ray fluorescence, probably because the formation of the dye end-group ion-pair is not complete. Finally, for latices prepared at relatively low emulsifier concentrations, the contribution of the sulphate end-groups to the surface charge density is significant and cannot be overlooked, as has been done in the past.
TL;DR: In this article, a torsion pendulum has been employed to investigate the low temperature relaxation in epoxy resins and in certain related rigid polymers, such as polycarbonate, polysulfone, polyimide, polyphenylene oxide, Bakelite, and a Friedel-Crafts polymer.
TL;DR: In this article, the authors studied the properties of high-flux ultrafiltration membranes with different macromolecular solutions and found that retention of polymers decreases with pressure and increases with agitation of the solution.
Abstract: Batch and flow recirculation cells were used to study the properties of high-flux ultrafiltration membranes with different macromolecular solutions. At low pressures, solutions of completely retained macromolecular solutes have a flux which is approximately the same as the flux of pure solvent. At higher pressures, the solution flux levels off. The flux, at the leveling-off period, is approximately inversely proportional to the solution concentration. In this plateau region the flux increases with temperature and agitation of the solution but decreases with time. These results are explained by the formation of a gel layer on the membrane surface during the filtration of macromolecular solutions. In ultrafiltration, in contrast to dialysis and GPC, a linear polymer penetrates the selective barrier more readily than does a globular protein of the same molecular weight. The difference may arise from the liquid shear stresses within the barrier medium due to the movement of fluid relative to the pore walls, which is large only in ultrafiltration. Also, retention of polymers was found to decrease with pressure and to increase with agitation of the solution.
TL;DR: In this article, the chemistry of these materials from the original polymer manufacturing through the various stages necessary to obtain the types of heat vulcanizing silicone rubber, room temperature vulcanising silicone rubber and silicone rubber adhesive most commonly used in medical applications.
Abstract: The medical grade silicones are probably the most widely used of all the synthetic polymers for permanently implanted subdermal devices. This paper reviews the chemistry of these materials from the original polymer manufacturing through the various stages necessary to obtain the types of heat vulcanizing silicone rubber, room temperature vulcanizing silicone rubber, and silicone rubber adhesive most commonly used in medical applications.
TL;DR: In this paper, a molecular structure approach was used to study the capillary flow instability resulting in extrudate distortion in polyethylene polymer melts, and it was found that the instability initiates at a critical value of elastic strain energy independent of (average) molecular weight.
Abstract: The capillary flow instability resulting in extrudate distortion has been studied for ethylene polymer melts using a molecular structure approach. It is found that the instability initiates at a critical value of elastic strain energy independent of (average) molecular weight for linear polyethylene. Once the flow breaks down, a slip interface within the melt is formed near the capillary wall, causing an abrupt increase in volumetric throughput. The velocity gradient within the melt remains continuous through the instability, however. Low molecular weight species present in the molecular weight distribution of linear polyethylene tend to suppress slip. Blends of linear and branched polyethylene exhibit instability behavior characteristic of both components throughout the entire range of composition. Results are discussed in terms of specific molecular mechanisms.
TL;DR: In this paper, the degradation of PMMA was investigated by extracting a polymer with toluene from the partially-degraded PMMA blend and it was found that chain scission had occurred, anhydride structures had been formed, and that the polymer showed differences in degradation behaviour compared with the original PMMA sample.