bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic interactions of branched polyethylene in polar and nonpolar systems
Authors: Cernia Enrico M. , Mancini Corrado , Saini Alberto 
Published: April 2003

AbstractThe thermodynamic properties of polymer solutions are frequently described in terms of the Flory‐Huggins equation. This equation includes a parameter χ, which depends upon the intermolecular forces acting between the molecules in a solution. The experimental determination of χ was performed by an improved microtechnique and extended to a wide range of polar and nonpolar diluents of polyethylene. Careful correlations are prescribed for calculating χ from pure‐component properties; they are based on an extension of the Hildebrand‐Scatchard theory of solutions and on the theory of intermolecular forces. Polar (τ) and nonpolar (δ) solubility parameters are presented for a variety of solvents. For polyethylene—nonpolar solvent systems we have emphasized the factor deciding the sign of heat of mixing, while for polyethylene‐polar solvent systems we have determined the contribution of dipole‐induced dipole interactions ψ (δτ) in interchange‐energy density B and, hence, χ.
Aromatic imide polymers for high‐temperature adhesives
Authors: Burgman H. A. , Freeman J. H. , Frost L. W. , Bower G. M. , Traynor E. J. , Ruffing C. R. 
Published: April 2003

AbstractDuring the past decade the aerospace industry has sought materials for bonding stainless‐steel and titanium alloys that have a high degree of thermal and oxidative stability. The Air Force Materials Laboratory has anticipated these requirements and sponsored many development programs aimed at achieving these goals. This paper describes the results of one such program devoted to development of high‐temperature adhesives from aromatic imide polymers. The family of polymeric materials known as aromatic polyimides possess excellent thermal and oxidative resistance at temperatures up to 650°F. Mechanical and electrical properties of glass‐fiber‐reinforced laminates prepared with these polymers have been reported. This work has been extended to the development of structural adhesives that will withstand long‐time exposure in air at 600°F. Stainless steel and titanium have been successfully bonded with adhesives made from aromatic imide and benzimidazole imide polymers. Bonds made with stainless steel have retained approximately 80% of their original strength at 600°F. after 1000 hr. of aging at 600°F. Adhesives made with benzimidazole imide polymers are the prepared materials for bonding titanium. Initial bond strengths of 1300 psi have been measured at 600°F. After 1000 hr. at 600°F. the bond strengths drop to 800 psi. The processing conditions for making a bond are quite moderate, except that a high temperature is required. The preparation and processing conditions associated with these adhesives are described. A large number of aromatic imide and amide‐imide polymers have been prepared and adhesives formulated. By comparing the bond strengths obtained with these adhesives it is possible to deduce the effect of molecular weight and various molecular components on bond strength.
Thermal degradation of polymer mixtures. I. Degradation of polystyrene–poly(methyl methacrylate) mixtures and a comparison with the degradation of styrene–methyl methacrylate copolymers
Authors: Grassie N. , McNeill I. C. , Cooke I. 
Published: April 2003

AbstractThe degradation behavior of mixtures of polystyrene and poly(methyl methacrylate) in the form of thin films cast from a solution containing both polymers has been compared with that of the individual polymers and of copolymers of the same monomer pair by means of thermal volatilization analysis (TVA) together with product analysis by gas‐liquid chromatography determinations of the molecular weight of the solid polymer residues. The results indicate no interaction between the polymers when degraded together. The polymer mixtures are readily distinguished from copolymers of the same overall composition by TVA.
A high hydroxyl group content found in high molecular weight fractions of poly(oxyethylene glycol)
Authors: Delmas G. 
Published: April 2003

AbstractThe results of a fractionation of high molecular weight poly(oxyethylene glycol) with the mixture benzene—isooctane are presented. The fractions are characterized by gel permeation chromatography (GPC), infrared spectroscopy, viscometry, and dialysis. A high hydroxyl content was found for the higher fractions, which is not compatible with a linear polyoxyethylene glycol molecule with hydroxyl endgroups. The presence of hydroxyl groups on the chain is improbable. The dialysis of the higher fractions in CCl4 and toluene shows that a surprising amount passes through the dialysis bag. The possibility of degradation of the polymer is considered. However, GPC analysis of the products of the dialysis suggest that the high molecular weight is made up of aggregates of middle‐sized molecules and low molecular weight ones, held together by hydrogen bonding between hydroxyl and ether groups. Some results of a fractionation in water with the lower critical solubility temperature at 99°C. are given.
Calorimetric behavior of methacrylic polymers
Authors: Griskey Richard G. , Hubbell Douglas O. 
Published: April 2003

AbstractSpecific heats for poly(methyl methacrylate), poly(diethylaminoethyl methacrylate), poly(cyclohexyl methacrylate), poly(allyl methacrylate), and poly(ethyl acrylate) were measured from 120 to 300°C. with a drop calorimeter. It was found that existing solid‐state theories and equations were unable to correlate the data. The reason advanced was that such theories were developed for crystalline materials, which differed greatly from the amorphous polymers of the present work. A more successful approach was to use a correlation technique originally developed for organic liquids.
Thermal degradation of poly(phenylene sulfide) and perfluoropoly(phenylene sulfide)
Authors: Christopher N. S. J. , Cotter J. L. , Knight G. J. , Wright W. W. 
Published: April 2003

AbstractThe thermal and oxidative degradation of poly(phenylene sulfide) and perfluoropoly(phenylene sulfide) have been studied by a weight‐loss method. The products of breakdown in vacuum have also been analyzed. The poly(phenylene sulfide) is more thermally stable in inert and oxidizing atmospheres than the fully fluorinated analog. The breakdown products can be accounted for by chain scission and transfer reactions. The formation of a large proportion of residue implies that crosslinking reactions play an important part in the degradation.
A dynamic mechanical study of the effect of chemical variations on the internal mobility of linear epoxy resins (polyhydroxyethers)
Authors: Van Hoorn H. 
Published: April 2003

AbstractA series of polyhydroxyethers prepared from various bisphenols and their diglycidyl ethers has been investigated for dynamic mechanical behavior in a temperature range from −180°C. up to their glass‐rubber transition region, employing a torsion pendulum method for frequencies of about 0.1 hz and a vibrating‐reed method for frequencies of about 100 hz. Glass‐rubber transition temperatures ranged from 85 to 170°C. and are interpreted in terms of polarity, segment bulkiness, and packing capability of the polymer molecules. In most cases the activation energy of this transition was found to be extremely high, of the order of 500 kcal./mole. Fair consistency is found regarding the role played by methyl or chlorine substitution of the bisphenol rings, increasing bulkiness and steric hindrance, but reducing polar interaction. At least one and, in some cases, two secondary transitions were found well below the glass‐rubber transition region. One is ascribed to a change in mobility of the glyceryl ether segments common to all nonesterified polymers of the series. While this is in general agreement with the findings of other authors, we found a spread in transition temperature values (−70 to −102°C. at ≈ 1 hz) and activation energies which can be related to the detailed chemical structure of these polymers. With methyl substitution of the bisphenol rings of the highly polar polymers symmetry seems to be an important factor. In addition, another secondary transition appeared, which we ascribe to an onset of ring rotation.
Determination of polyolefin film properties from refractive index measurements. II. Birefringence
Authors: Schael George W. 
Published: April 2003

AbstractThe use of refractive index data for studying changes in oriented polyolefin films has been demonstrated. Application of this technique to oriented polypropylene and polyethylene films showed that the birefringence is a linear function of the refractive index in the direction of maximum orientation. By utilizing refractive index, density, and crystallinity data the crystalline refractive indices nc and (na + nb)/2 and polarizabilities α∥ and α⊥ could be estimated for polypropylene and polyethylene.
The effect of a low‐viscosity swelling liquid on the tensile strength of rubber
Authors: Grosch K. A. 
Published: April 2003

AbstractThe paper examines the effect of swelling on a number of different gum rubbers and rubbers filled with different types and concentrations of black. The observed decrease in strength with decreasing rubber fraction Vr (increasing swelling ratio) is, in the case of gum rubbers, associated with a decrease in internal friction. The incorporation of a black filler is shown to increase strength by hydrodynamic stiffening and by an increase in internal friction of the rubber network, and a simple reduction scheme of the data shows a close analogy between the strength as a function of Vr and the dynamic modulus of a rubber solution as a function of concentration. The results lead to a failure criterion, which describes the energy density at break as a simple function of the hysteresis near break.
Brabender Plasticorder studies of the process of crosslinking polyethylene
Authors: Narkis Moshe , Miltz Joseph 
Published: April 2003

AbstractThe process of crosslinking unfilled thermoplastic polyethylene has been followed with the aid of the Brabender Plasticorder. It is shown that extrusion conditions without any significant scorching can be obtained with this instrument. The maximum torque in the plastograms is discussed and shown not to be a correct criterion of crosslinking efficiency, since its value is influenced by a process of shear grinding of the crosslinked polymer. The crosslinking is further continued after the maximum torque is reached. The dependence of gel content on peroxide concentration is given.
Dynamic mechanical properties of some polymeric acid zinc salts
Authors: Fields J. E. , Nielsen L. E. 
Published: April 2003

AbstractMechanical properties, shear modulus, and damping of a series of polyacid divalent metal salts have been correlated with the degree of salt formation. The salts were prepared in situ by molding mixed powders of 94/6 acrylic acid–2‐ethylhexyl acrylate and zinc oxide at temperatures of 200–300°C. and pressures of 5,000–10,000 psi. Zinc oxide consumption was followed by x‐ray techniques. Compositions contained 25–200% of theory metal oxide as charged. Excesses, over theory, of metal oxide were shown to lead to the formation of substantial amounts of pendent half‐salts which are high damping and have temperature‐sensitive shear moduli. Only complete reaction as the di‐salt, at 300°C. and 10,000 psi, leads to low damping products with temperature‐insensitive high modulus. The modulus increase due to ionic bonding as the di‐salt, over that expected from classical filler action alone, ranged from 40 to 80%, depending upon the theory chosen to calculate filler action. The pendent half‐salt gives much smaller moduli increases and unreacted metal oxide appears to act as classical filler in an intertangled complex polyelectrolyte salt matrix. The modulus of the di‐salt was found to be 6–7 times higher than moduli for normal organic rigid polymers.
Flammability and thermal stability of isocyanate‐based polymers
Authors: Backus J. K. , Bernard D. L. , Darr W. C. , Saunders J. H. 
Published: April 2003

AbstractA series of model polyurethanes and polyureas, a polyamide, and a polyimide were prepared by reacting 4,4′‐diphenylmethane diisocyanate or polyisocyanates having similar polybenzyl structures with aliphatic or aromatic coreactants. Thermogravimetric analyses indicated that the flammability of the polymers was related to the formation of volatile flammable products during early stages of decomposition. Determinations of the heat evolved during differential thermal analyses and of the thermodynamic heats of combustion suggested that the extent and rate of reaction were among the important factors governing flame propagation. Flame‐resistant polymers were prepared by use of structural elements which were thermally stable and nonvolatile or which formed nonflammable decomposition products.
Reactions of carbon black. Part I. Nonthixotropic carbon black compositions
Authors: Takashina Naomitsu , Aida Tetsuo 
Published: April 2003

AbstractThe solution polymerization of butyl acrylate in the presence of a furnace black was found to produce a stable dispersion of carbon black which showed Newtonian flow, while the mixture prepared by mixing the same carbon black into a solution of poly(butyl acrylate) homopolymer had a large degree of thixotropy. A marked change in the viscosity of the reaction mixture was also observed at an early stage of polymerization when the initial mixture which was a moist mass with no fluidity, turned to a fluid easily stirred. The change in viscosity and the transition in flow behavior were carefully followed with a rotary cylinder type viscometer. The non‐Newtonian initial mixture was found to turn to a Newtonian fluid at low conversion of the monomer. Beside the adsorption of the homopolymer onto the surface of carbon black particles, which would occur also in mechanical mixing, the change in the flow behavior was estimated to be caused by the change in the shape and the size of the dispersed carbon black particles due to the change in the condition of the surface of the particles by which growing polymer radicals, as well as initiator radicals, were captured.
Growth, morphology, and reinforcement potential of low molecular weight crystals in amorphous polymeric matrices
Authors: Joseph Jacques R. , Kardos John L. , Nielsen Lawrence E. 
Published: April 2003

AbstractThe technique of in situ crystallization of low molecular weight organic compounds from amorphous polymers was evaluated as a method of fabricating composite materials. Two workable systems, styrene–acrylonitrile copolymer (SAN)–acetanilide and SAN–anthracene, were found and their phase diagrams determined. In both systems kinetic studies revealed that the maximum crystallization rate takes place at large degrees of supercooling and that below these temperatures the mechanism is diffusion‐controlled. The temperature‐dependent crystal morphologies were characterized with electron microscopy, which showed three distinctly different morphologies for both systems. From dynamic mechanical measurements, it appears that the elastic moduli of organic crystals are about the same as those of organic polymers in the glassy state, and that relatively little reinforcement took place under the particular crystallization conditions employed.
The chemistry of sulfur curing. Part II. Kinetics of vulcanization of an EPDM elastomer accelerated by tetramethylthiuram monosulfide and disulfide
Authors: Wolfe James R. 
Published: April 2003

AbstractThe induction periods and maximum cure rates of an EPDM gum rubber were determined by using the Monsanto oscillating disk rheometer and correlated against the initial concentrations of curing ingredients. Sulfur curing systems accelerated by TMTM and TMTD were used. The maximum cure rates of the TMTM‐accelerated and the TMTD‐accelerated EPDM terpolymer compounds differed significantly only at low sulfur concentrations where the TMTM‐accelerated compounds had slower maximum cure rates. Above approximately the 1% concentration level, TMTM and TMTD were found increasingly to retard the maximum cure rates of the EPDM terpolymer compounds as the initial concentrations of the thiuram accelerators were increased. The maximum cure rates of the TMTM‐and TMTD‐accelerated terpolymer compounds were found to be variable order in initial accelerator concentration, second‐order in initial cure site concentration, approximately half‐order in initial sulfur concentration above 0.3% sulfur, and of a positive variable order in initial zinc oxide concentration.
Fracture behavior of rubber‐modified thermoplastics after aging
Authors: Bucknall C. B. , Street D. G. 
Published: April 2003

AbstractExperiments show that the effects of outdoor aging on rubber‐modified thermoplastics can be reproduced by laminating a layer of a glassy polymer onto the surface of unaged specimens. This technique is used to study the effects of fracture temperature, specimen geometry, and polymer composition on the impact strength of aged HIPS and ABS. Aging reduces the energy of crack initiation, so that the impact strength is determined by the crack‐propagation energy, which is in turn governed by the nature and concentration of the rubber and by the fracture temperature.
Gel in polyethylene
Authors: Mortimer George A. , Wade Dennis E. , Arnold Lloyd C. 
Published: April 2003

AbstractA quantitative test for the presence of gel (insoluble polymer) in polyethylene is described. A number of experiments were performed by using the test and on the polymers separated by the test. It is concluded that gel is crosslinked polyethylene in the form of discrete particles of significant size, the large ones, probably weighing up to at least 10 mg. Some crosslinks are broken by treatment with solvents above 200°C., and much of the gel is thus rendered permanently soluble. Gel is also insoluble in the reaction medium in which it is produced. Thus, even if the ethylene–polyethylene phase relationships would predict a homogeneous reaction, the reaction must be hetero‐geneous if gel is present. Therefore, kinetic treatments of ethylene polymerization which do not consider phase separation when gel is found in the reaction product are oversimplified.
Variation of refractive index of polystyrene with molecular weight: Effect on the determination of molecular weight distributions
Authors: Barrall E. M. , Cantow M. J. R. , Johnson J. F. 
Published: April 2003

AbstractSensitive refractive index measurements on solutions have indicated that the narrow molecular weight polystyrene samples prepared by the Mellon Institute method exhibit a small systematic molecular weight–refractive index dependence up to 300,000 and higher. This upper limit is higher than had previously been suggested. Sensible consistency is generally assumed above a few thousand molecular weight. The effect on this molecular weight–refractive index dependence on gel permeation chromatography and light‐scattering molecular weight measurements on polystyrene standards is illustrated.
Influence of cohesive forces on the glass transition temperatures of polymers
Authors: Lee W. A. , Sewell J. H. 
Published: April 2003

AbstractThe relationship between cohesive energy (c.e.) or cohesive energy density (c.e.d.) and the glass transition tenperature (Tg) of polymers has been re‐examined on the basis of literature data. For polymers with Tg above 25°C., there is no correlation between published or calculated values of c.e. or c.e.d. and Tg. However, for the rest of the polymers there is a linear relationship between c.e.d. and Tg, and a broad relationship between c.e. and Tg. These results imply that c.e.d. is the regulating, though not the only, factor in determining Tg's up to values of approximately 25°C.
ESR study of reactions of cellulose with ·OH generated by Fe+2/H2O2
Authors: Arthur Jett C. , Hinojosa Oscar , Bains M. S. 
Published: April 2003

AbstractIt was demonstrated by ESR spectroscopy that the Fe+2/H2O2 system gave a reactive species which generated an ESR triplet spectrum or sorbitol similar to that generated by hydroxyl radicals from the Ti+3/H3O2 system. An ESR spectrum was obtained for the hydroxyl radicals generated by the latter system. However, the lifetime of hydroxyl radicals, generated by the Fe+2/H2O2 system, was apparently very short, and an ESR spectrum for the hydroxyl radicals, generated by this system, was not observed. The Fe+2/H2O2 system also generated triplet spectra with cotton cellulose I, cotton cellulose II, and microcrystalline cellulose, suggesting that a hydrogen atom had been abstracted from the hydroxyl group on carbon C6, or possibly the hydrogen atom on carbon C5. The ESR spectrum generated on microcrystalline cellulose was less intense than those generated on cellulose I and II. On initiation of graft polymerization of the activated cellulose with acrylonitrile, the triplet spectrum disappeared and was replaced by two strong singlet spectra. One of the singlet spectra was likely generated on carbon C1 or C4 on depolymerization of the cellulose molecule, and the other was probably generated on the end of the growing polyacrylonitrile molecular chain. The absence of a triplet spectrum gave direct evidence for the order in which the acrylonitrile monomer was being grafted onto the cellulose molecule. The mechanisms proposed by Haber and Weiss for the reactions generated in the Fe+2/H2O2 system were generally supported.
Compressibility and other thermodynamic properties of polymers
Authors: Surland C. C. 
Published: April 2003

AbstractExperimental methods for estimating the thermodynamic derivative, (∂T/∂P)s, of both liquids and solids are described and discussed. The adiabatic heating parameter is shown to be useful, in conjunction with other more commonly measured properties, for estimating the heat capacity, Cp = T(∂S/∂T)p, and the internal pressure, Pi = (∂U/∂V)T. The principles for applying adiabatic heating measurements to the characterization of polymers are given with data for several common liquids and for filled and unfilled polyurethane rubbers.
Mechanochemical degradation of an EPDM polymer
Authors: Baranwal Krishna 
Published: April 2003

AbstractA mill‐mastication study of an EPDM polymer (DuPont, Nordel 1070) was conducted in the mill‐roll temperature range of 68–480°F. The extent of degradation was determined by dilute‐solution viscosity measurements. The role of oxygen in the polymer mastication was followed by infrared spectroscopy. The breakdown of the EPDM polymer on the mill is minimum in the temperature range of 185–315°F. Up to 315°F. the increase in temperature leads to a decreased amount of degradation. During cold mastication mechanical breakdown occurs. The use of a free‐radical acceptor shows that this type of breakdown is caused by the mechanical rupture of CC bonds in the polymer chain. At and above 350°F. thermooxidative degradation becomes dominant, the polymer degrading drastically, and the higher the temperature, the greater the extent of degradation for the same period of mastication. Infrared spectroscopy shows that hot mastication results in decreased double‐bond concentration and increased amounts of carbonyl and, possibly, anhydride and lactone groups. Of the carbonyl groups formed 30% are due to the oxidation of double bonds in terpolymer and 70% to the oxidation of the main chain. A mechanism is proposed to account for these observations.