bluuebunny/crossref_metadata_2025 huggingface dataset:
Load‐compression behavior of brittle foams
Authors: Rusch K. C.
Published: April 2003

Quantitative relationships between the load‐compression behavior and the physical characteristics of the foam matrix, previously reported for flexible systems, have now been extended to brittle foams. The shape of the compression curve is expressed in terms of ψ(ε), a dimensionless function of the compressive strain, while the stiffness, or load‐bearing capacity, is defined by Ef, the apparent Young's modulus. Because the brittle matrix breaks–rather than flexes–when compressed, a brittle foam exhibits a flatter and wider plateau in the load‐compression curve than a rigid (but ductile) foam of equivalent density, cell geometry, and Ef. These differences are expressed quantitatively by ψ(ε). It is important to distinguish between brittle foams and rigid, but ductile, foams. Since both types may exhibit the same stiffness, this distinction, particularly significant in energy absorbing applications, often is not considered in designing foam structures. Using the relationships established in this report, it is now possible to delineate precisely the characteristics a brittle foam must possess to meet a given load‐compression specification.
A comparison of inlet‐ and exit‐region flow of viscoelastic fluids in capillary tubes
Authors: Oliver D. R. , Macsporran W. , Hiorns B. M.
Published: April 2003

It is shown, in confirmation of earlier work, that when a viscoelastic liquid flows into a capillary tube, a definite fraction of the inlet pressure drop is required to overcome effects of elastic origin. This pressure drop, ΔPE, is proportional to the same power of shear rate as the steady‐state first normal stress difference measured by means of the jet thrust method. The values of ΔPE are some 1.6–8.6 times higher than the values of the first normal stress difference, the amount depending on the fluid in use but not on the elastic power‐law exponent m. The importance of the extensional mode of deformation in entry region flow is discussed. It is shown by examining dilute polymer solutions after varying periods of degradation that changes in ΔPE are closely related to changes in the turbulence suppression characteristics of the solutions. The extensional mode of deformation is presumably important in both types of experiment. Both n‐pentanol and a mineral oil, tested in the same small‐diameter capillary tubes as the polymeric solutions, give well‐defined values of ΔPE, which are compared with previously published normal stress figures. The mineral oil is shown to develop particularly high stresses in elongational flow, though the viscous stresses were also higher than for the polymeric solutions used. Previous evidence of the existence of shear elasticity in organic liquids is listed and the potential importance of the case of mineral oil is emphasized.
Thermogravimetric and differential thermal analysis of cellulose, hemicellulose, and lignin
Authors: Ramiah M. V.
Published: April 2003

The thermal degradation of samples of cellulose, hemicellulose, and lignin have been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) between room temperature and 600°C. The results calculated from static and dynamic TGA indicated that the activation energyEfor thermal degradation for different cellulosic, hemicellulose, and lignin samples is in the range 36–60, 15–26, and 13–19 kcal/mole, respectively. DTA of all the wood components studied showed an endothermic tendency around 100°C in an atmosphere of flowing nitrogen and stationary air. However, in the presence of flowing oxygen this endothermic effect was absent. In the active pyrolysis temperature range in flowing nitrogen and stationary air atmospheres, thermal degradation of Avicel cellulose occurred via a sharp endothermic and a sharp exothermic process, the endothermic nadir and exothermic peak being at 320° and 360°C, respectively. In the presence of oxygen, combustion of Avicel cellulose occurred via two sharp exothermic processes. DTA studies of different cellulose samples in the presence of air showed that the shape of the curve depends on the sources from which the samples were prepared as well as on the presence of noncellulosic impurities. Potassium xylan recorded a sharp exothermic peak at 290°C in a nitrogen atmosphere, and in a stationary air atmosphere it yielded an additional peak at 410°C, while in the presence of oxygen the curve showed two sharp exothermic peaks. DTA traces of periodate lignin in flowing nitrogen and air were the same and showed two exothermic peaks at 320° and 410°C, while in the presence of oxygen there were two exothermic peaks in the temperature range 200°–500°C.
The effect of high energy radiation on the electrical characteristics of pyrrone polymers
Authors: Reucroft P. J. , Scott H. , Kronick P. L. , Serafin F. L.
Published: April 2003

Gamma radiation‐induced conductivity and permanent conductivity effects produced by high doses of 2 MeV electrons have been measured in two polyimidazopyrrolone polymers. Radiation‐induced conductivity levels are small compared to those found in many common insulating polymers. Permanent increases in dark conductivity produced by accumulated doses of 5×109 rad at temperatures up to 300°C are not sufficient to inhibit ultraviolet‐visible photoconductivity. High doses of 2 MeV electrons (5×109 rad) under the same temperature conditions produce no discernible effect on dielectric properties. Both radiation‐induced conductivity and permanent dark conductivity increases were much smaller in one polymer (BTDA–DAB), suggesting the possibility of optimizing radiation resistance in this class of polymers by means of chemical structure variation. The radiolytic and thermal stability reported previously for this class of polymers has been generally confirmed, with particular reference to electrical properties.
Slow crack growth in cellulose film
Authors: Hilyard N. C. , Crum J. L.
Published: April 2003

A simple photographic method for measuring the slow crack growth in transparent polymer film is described. Framing speeds up to 100 per second have been achieved. Experimental data for a cellulose film with centrally located initial cuts indicate that for 0 < t < 0.8tb, the crack length c increases with time t according to

where c0 is the initial cut size, K a constant, and tb the time to fracture.
Solution‐polymerized rubbers with superior breakdown properties
Authors: Uraneck C. A. , Short J. N.
Published: April 2003

Natural rubber breaks down readily during mechanical mixing, and rubber processors have traditionally made good use of this property. Emulsion SBR rubber breaks down with greater difficulty and some polybutadiene rubbers, not at all. This paper describes a new class of solution elastomers, both polybutadiene and butadiene–styrene copolymers, designed to undergo controlled breakdown during processing. They can be made by reacting active polymer lithium molecules with tin compounds to produce star‐shaped molecules containing a central tin atom connected by tin–carbon bonds. When such a product is mixed with an organic (stearic) acid, some of the tin bonds are ruptured and the desired breakdown occurs. The extent of breakdown can be controlled by the mixing conditions and the amount of organic acid employed. There are numerous applications in which these rubbers process more easily and display better properties than conventional rubbers. Data on breakdown under various conditions and physical properties of the compounds are presented in this paper.

In addition to the superior processing characteristics, these products introduce a new concept of elastomer breakdown. The breaking of a polymer chain at a carbon–tin bond by a chemical agent eliminates the need for breaking carbon–carbon bonds by mechanical energy or oxidative degradation. Accomplishing polymer breakdown by a controlled reaction, rather than by conventional means, has long been an unsolved problem of the rubber industry.
Energy‐absorbing characteristics of foamed polymers
Authors: Rusch K. C.
Published: April 2003

The energy‐absorbing characteristics of a foam are determined by its load–compression response, and hence reflect the geometric structure and physical properties of the matrix material. In this report, the energy‐absorbing characteristics are expressed in terms of three dimensionless quantities: (1) K, the energy‐absorbing efficiency, (2) I, the impact energy per unit volume divided by Ef, and (3) I/K, the maximum decelerating force per unit area divided by Ef, where Ef is the apparent Young's modulus. Using the calculation procedures described in this report, it is now possible to delineate the geometric structure and physical properties a foam matrix must possess to meet a given energy absorption specification. This approach shows that: (1) the energy‐absorbing characteristics of a brittle foam are superior to those of a ductile foam, (2) the optimum energy‐absorbing foam has a large cell size, a narrow cell size distribution, and a minimum number of reinforcing membranes between the cells, (3) foam composites offer no significant advantage over a single foam, and (4) the optimum energy‐absorbing region obtains over a tenfold change in impact velocity and can be extended in a given system only if the foam stiffness increases while the impact velocity is increased, as in a fluidfilled foam.
Inorganic polymers. IV. Reactions of poly(P‐phenylphosphonic imide). The replacement polymerization of poly(P‐phenylphosphonic imide) with piperazine
Authors: Shaw R. A. , Ogawa Takeshi
Published: April 2003

Poly(P‐phenylphosphonic imide) reacts with a variety of compounds containing reactive hydrogen atoms, due to the instability of the PNP linkage to such reagents. Utilization of this property of the polymer may provide convenient routes to prepare various types of P‐phenylphosphonic diamides, Ph(O)P(NH2)(NR′2), phosphonamidates, PhP(O)(NH2)(OR), etc. (R = H, alkyl, aryl, etc.). The reaction of the polyimide with piperazine results in a polymer containing
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structural units. The polymer thus obtained is however only partially soluble in the usual organic solvents, and this insolubility is probably due to crosslinking catalyzed by piperazine. The product polymer was found to be thermoplastic.
Studies on sublimation of disperse dye out of dyed polymers. II. Rate of sublimation and amorphous transition of polypropylene
Authors: Okajima Saburo , Sato Nobuhiko , Tasaka Motowo
Published: April 2003

The diffusion coefficient D of disperse dyes through unmodified polypropylene (dyed at 120° and 137°C) was measured at 50°–160°C in the dry system. The diffusion transition points indicated by the breaks in the log D versus 1/T°K were obtained at about 70°, 90°, and 115°C. The 70° and 115°C transitions are in good accordance with the transition temperature of smectic into monoclinic phase and with the temperature of abrupt change in lattice expansion of monoclinic crystal, respectively. These phenomena were explained on the basis of the intimate correspondence between amorphous and crystalline transitions, as expressed by one of us for poly(ethylene terephthalate). The 115°C transition was confirmed by the same sort of diffusion transition occurring, expectedly, at 83°C in the case of polyethylene, an abrupt increase in lattice expansion of which had been found at about 80°C. The diffusion transitions were also confirmed by dilatometry and shrinkage measurement. The 90°C transition has never been reported and it cannot be explained at present.
The sorption of poly(vinyl acetate) on cellulose. I. The nature and extent of the sorbed layer
Authors: Alince B. , Kuniak L. , Robertson A. A.
Published: April 2003

The sorption of poly(vinyl acetate) from benzene solution onto cellulose fibers has been investigated with particular attention to the nature and extent of the sorbed layer of polymer. The cellulose substrate has been varied by swelling pretreatments with water, ethylenediamine, and 18% sodium hydroxide. The density of the sorbed polymer after drying was found to be similar to that of the bulk polymer (1.19–1.20 g/cm3). Water vapor sorption isotherms were used to evaluate the internal surface of cellulose and the decrease in the surface area accessible to water after sorption of the polymer. This decrease was considered equivalent to the area covered by sorbed polymer. The amount of polymer sorbed per unit area (5.0–5.5 mg PVAc sorbed from benzene per 1 m2 of cellulose surface) was found to be substantially independent of the amount of sorbed polymer and of the swelling pretreatment, indicating that the thickness of the sorbed layer was quite uniform (40–50 Å). A comparison of the thickness of the sorbed layer in the dry state with the thickness of a monolayer with polymer molecules lying flat on the solid surface indicated that the fraction of the polymer segments attached directly to the surface was about 0.10. The amount of polymer sorbed per unit area of cellulose and consequently the thickness of the sorbed layer and the fraction of attachment can be affected by the nature of the solvent from which the polymer is sorbed.
Effects of thermal history on the peel strength of linear polyethylene
Authors: Tordella John P.
Published: April 2003

Peel strength of linear polyethylene–aluminum bonds is strongly affected by thermal history. Slow cooling from the melt resulted in 10 lb/in. peel strength; quenching, in 50–90 lb/in.; annealing of quenched bonds reduced the peel strength to 30 lb/in. Adhesion to aluminum was obtained by treating the substrates in a solution of vinyl triethoxysilane. Cohesive failure occurred regardless of thermal treatment. The changes in peel strength were not due to changes in strength of the bulk polymer. Rather, the volume of polymer deformed in peeling seemed to correlate with strength. No correlation was found between peel strength and degree of crystallinity or of transcrystalline orientation. Segregation resulting in a weak boundary layer seems to be the probable cause of the dependence of peel strength on cooling rate, and changes in the tie molecule configuration, the cause of loss of strength on annealing.
Time‐dependent flow of quasi‐linear viscoelastic fluids
Authors: Chong J. S. , Franks R. G. E.
Published: April 2003

Transient flow behavior of an incompressible quasi‐linear viscoelastic fluid under suddenly applied constant pressure as well as under a periodic pressure gradient was investigated using a three‐parameter relaxation function. In the light of these solutions, the roll of viscoelastic relaxation in the overshooting of volumetric flow rate and the effect of viscoelastic parameters on the mean square velocity profile are discussed.
Some studies on the swelling behavior of polyethylene
Authors: Rogers Morris G.
Published: April 2003

When polymers are extruded from a capillary, the amount of extrudate swelling is generally found to be a function of shear rate and capillary dimensions. Experiments with polyethylene now show that when shear rate is replaced by an average transit time in the capillary, postextrusion swell becomes a function of transit time only. Plots of swell versus transit time are independent of the applied stress and reduce to a single line for capillaries of different dimensions. The swell was found to be dependent upon the average molecular weight and the molecular weight distribution. Little correlation, however, was found with the amount of high molecular weight fractions.
Crosslinking cotton cellulose with ethyleneurea derivatives having varying hydrogen‐bonding capabilities. II. Accessibility determinations
Authors: Stevens C. V. , Smith B. F.
Published: April 2003

In a continuation of previously reported work of the effect on cotton cellulose of ethyleneurea crosslinking agents modified with ring substituents of varying hydrogen‐bonding capabilities, accessibilities of the cellulosic hydroxylic protons to exchange with deuterium oxide vapor were determined by means of infrared spectroscopy. In analyzing these values with respect to previously reported data on physical properties of the treated fabrics, it was found that accessibility to deuterium oxide did not correlate with moisture regain of the resin‐treated samples as has been reported for physically modified celluloses. It appears that the different resins did have some effect on the structure of water adsorbed by the fiber and also that the solvent affected the manner in which the resins attached themselves to the cellulose and eliminated water from the structure. Values of accessibility were not found to correlate well with crease recovery, although a weak trend was indicated. Accessibility was found to decrease as the infrared band for ring stretching decreased.
Some thermodynamic aspects of polymer adhesion
Authors: Owens D. K.
Published: April 2003

Recently developed techniques permit the estimation of the surface free energy of polymers and the separation of this free energy into dispersion and hydrogen‐bonding components. These techniques have been used to calculate the thermodynamic reversible work of adhesion of a vinylidene chloride copolymer coating to propylene film. The changes in work of adhesion upon immersion of the coated polypropylene in water and surfactant solutions were calculated. When the calculated work of adhesion was negative, spontaneous separation of the coating from the polypropylene occurred upon immersion in all cases. When the calculated work of adhesion was positive, no separation was observed in agreement with theory.
A classification of hydrogen‐bonding solvents by sonic velocity measurements
Authors: Craver J. Kenneth
Published: April 2003

The relative hydrogen‐bonding capabilities (γw) of various solvents and mixtures were determined by measuring their effect upon a paper web using nondestructive sonic velocity techniques. Some exceptionally strong H‐bonding solvents are identified.
The radiation‐initiated solution polymerization of vinylidene fluoride
Authors: Doll W. W. , Lando J. B.
Published: April 2003

The radiation‐initiated solution polymerization of vinylidene fluoride was examined in an effort to determine the effect of polymerization conditions on the head‐to‐head content of the resulting poly(vinylidene fluoride). No appreciable change was observed in the head‐to‐head content when this new type of polymerization was utilized. However, the polymers which resulted had melting points 10–15°C higher than those of the suspension‐polymerized poly(vinylidene fluoride), higher crystallinity, and, when trifluoroacetic acid was used as a solvent, a higher molecular weight.
On the rheological interpretation of die swell in molten polymers
Authors: Han Chang Dae
Published: April 2003

The reasons are given for the failure of the momentum method due to Metzner et al. to predict correct orders of magnitude in normal stress difference of polymer melts in simple shearing flow, and an expression is given for calculating the normal stress difference of polymer melts in steady fully‐developed flow from “exit pressure” measurements.
Dynamic mechanical properties, structure, and composition of impact polystyrene
Authors: Cigna G.
Published: April 2003

Two series of impact polystyrene were studied; they had been obtained by grafting and by mechanical mixing, at two different known polybutadiene levels. Their biphasic structure had been characterized by optical microscopy and physicochemical separation. The following factors were investigated: morphology and content of the dispersed phase and continuous phase, composition of the dispersed phase, and molecular weight of the continuous phase. The elastic shear modulus and mechanical damping were measured. It was found that the elastic shear modulus of the two series of materials does not depend on the total polybutadiene content, as is often suggested in the literature, but on the rubbery dispersed phase content. The polybutadiene concentration of this phase, although varying between 100% for the mechanical mixes and 34% for one of the grafted polymers, does not influence the mentioned correlation. The particle size of the dispersed phase and the molecular weight the continuous phase have very little or no influence. The found correlation agrees with the theories for the moduli of models consisting of dispersions of spheres or particles in a matrix, like those of Kerner,13 Hashin,14,15 and Mackenzie.18
Influence of diphenyl ether and water on the polymerization of isoprene with triisobutylaluminium and titanium tetrachloride
Authors: Gippin Morris
Published: April 2003

In the polymerization of isoprene with the i‐Bu3Al/TiCl4 catalyst at the mole ratio of 1.0 the diphenyl ether adduct of the i‐Bu3Al showed no effect on the catalyst efficiency. The ether did not improve the low efficiency of the catalyst at ratios slightly above 1.0, but below 1.0 it brought the catalyst activity up to optimum. The ether compensated for the deleterious effects upon the catalyst of low amounts of water present in the isoprene solution in hexane. At the Al/Ti mole ratio slightly above 1.0, water and diphenyl ether were found to act synergistically in raising catalyst efficiency. In addition, at or close to optimal operating Al/Ti mole ratios the diphenyl ether had a very marked effect in improving the polymerization rate. Polymer properties were generally unaffected by use of the ether‐coordinated catalyst.
Mechanism and kinetics of polyethylene crosslinking by α,α′‐bis(tert‐butylperoxy)‐p‐diisopropylbenzene
Authors: Šimúnková D. , Rado R. , Mlejnek O.
Published: April 2003

The study of the mechanism of polyethylene crosslinking is realized by a kinetic analysis of the α,α‐bis(tert‐butylperoxy)‐p‐diisopropylbenzene decomposition, as well as by the determination of its decomposition products and crosslink formation in the polymer. The experiments were carried out in a temperature range of 118°–148°C in both polyethylene and its low‐molecular model, n‐octane. From the results obtained it follows that the peroxide decomposition in both hydrocarbon media is kinetically a unimolecular reaction with an activation energy of 36 ± 2 kcal/mole and with an equivalent participation of both peroxidic groups, whereby a biradical formation is improbable. Macroradicals arise by a dehydrogenization reaction in which mainly primary oxyradicals of various types take part and methyl radicals are also formed by a transformation process of the former. Both types of radicals decay exclusively in a substitution reaction with polymer chains. The whole process is terminated by macroradical recombination so leading to crosslink formation in polyethylene.
Nitric acid attack on polypropylene. Weight and density changes and blister formation during the initial stages
Authors: Armond V. J. , Atkinson J. R.
Published: April 2003

Weight loss and density change results are presented to indicate the manner in which fuming nitric acid at 70°C attacks three grades of polypropylene of different crystallinity. The phenomenon of surface blistering is discussed in relation to the spherulitic structure at the surface of the bulk specimen.
A rheological study of the low molecular weight butyl polymer
Authors: Drexler Leonard H.
Published: April 2003

A rheological study has been performed to characterize the low molecular weight butyl polymers using a couette coni‐cylindrical viscometer. The bulk viscosity was determined as a function of temperature, weight‐average molecular weight, viscosity‐average molecular weight, and shear rate. The temperature dependence of the viscosity, while adequately represented by the Williams, Landel, and Ferry equation, is best described by an Arrhenius equation for the temperature range investigated. The viscosity is shown to vary with the 3.5th power of the weight‐average molecular weight above a critical molecular weight and to the 1st power below this molecular weight. Although the ratio of the weight‐average molecular weight to the number‐average molecular weight usually affects the flow properties of polymers, this was not true for the polymers investigated. The bulk viscosity was found to be independent of the molecular weight distribution for the temperature and shear rate range studied. It has been shown that a definite relationship exists between the bulk viscosity and the viscosity‐average molecular weight as determined by dilute solution viscosity. A mathematical model has been developed to relate these two parameters as a function of temperature and shear rate.
Time‐dependent effect of spherulite size on the tensile behavior of polypropylene
Authors: Remaly L. S. , Schultz J. M.
Published: April 2003

The mechanical behavior of isotactic polypropylene following primary crystallization is known to be dependent on the aging time (e.g., at room temperature). This aging time effect is believed to be related to a form of additional crystallization (sometimes called secondary crystallization). We show in the present work that the aging characteristics depend on spherulite size and that indeed the spherulite size effects reported by others very likely reflect chain rearrangements upon aging, rather than some property associated with the as‐crystallized material.
Poisson's ratio for rigid plastic foams
Authors: Rinde J. A.
Published: April 2003

Poisson's ratio for several low‐density plastic foams has been determined in both tension and compression. For polystyrene bead foams and a polyurethane foam, Poisson's ratio is greater in tension than compression. In compression, Poisson's ratio is not linear, showing a larger value below the yield strain and a value near zero for high strains. For 0.05 and 0.10 g/cc polystyrene bead foam, Poisson's ratios are 1/3 in tension and 1/4 in compression below the yield strain; at higher strains, the value in compression is in the range 0.03–0.07.
Polymer fractionation by repeated extraction
Authors: Klein J. , Friedel H.
Published: April 2003

All current fractionation techniques—based on sol–gel equilibria—are characterized by a variation of the solvent power after each fractionation step in a discontinuous as well as in a continuous way. Overlapping of consecutive fractions is the consequence of this procedure. It can be shown that this overlapping can be diminished essentially by a multistage technique based on complete extraction at a given solvent power which then will be changed in discontinuous steps. As a further consequence, it is possible to obtain very homogeneous fractions of M̄w/M̄n < 1.03. A theoretical analysis of this technique on the basis of phase equilibrium data will be given, the results of which can be confirmed experimentally.
Dynamic young's and shear moduli of graphite fiber‐reinforced high‐temperature matrix resins
Authors: Dudek T. J.
Published: April 2003

The resonant frequencies of unidirectional graphite fiber‐reinforced polyimide (Skybond 703) and polyquinoxaline resin composite beams were determined. The Timoshenko beam theory was employed to compute both the longitudinal Young's modulus (E11) and the effective transverse‐longitudinal shear modulus (G12) from the set of resonant frequencies of the beams. E11, E22, and G12 were determined for a 64% by volume Modmor II‐reinforced polyimide (Skybound 703) composite, and E11 and G12 were determined for cured and postcured Modmor II‐reinforced polyquinoxaline (PQ) composites. Dynamic E11 and E22 results were found to agree with experimentally determined static flexural moduli. Voids present in these high‐temperature resin composites to an extent of 5–13% by volume appeared to lower the effective shear and longitudinal moduli of the composites.
Evaporation rate and equilibrium phase separation data in relation to casting conditions and performance of porous cellulose acetate reverse osmosis membranes
Authors: Kunst B. , Sourirajan S.
Published: April 2003

Quantitative data on solvent evaporation rates and equilibrium phase separation compositions corresponding to different film casting conditions are given, and the results are discussed with reference to reverse osmosis data on membrane performance. A typical evaporation rate curve plotted on a semilog scale consists of an initial linear part from whose slope evaporation rate constants b have been determined. For a given casting solution composition and temperature, an optimum value of b exists for best membrane performance, and identical values of b result in same membrane performance. Treating the casting solution as a polymer–solvent–nonsolvent ternary system, the data on equilibrium phase separation compositions have been plotted in a triangular diagram for solution temperatures of −10°, 0°, and 24°C. The data indicate that even small changes in solution temperature can bring about significant changes in solution structure and hence membrane performance, and useful conclusions on solution structure can be drawn from such phase equilibrium diagrams. The data and correlations presented here offer a quantitative confirmation of the governing significance of the solution structure‐evaporation rate concept relating to the mechanism of phase separation and pore formation in the surface region during the process of making reverse osmosis membranes.
Thermal decomposition products of cellulose
Authors: Tsuchiya Yoshio , Sumi Kikuo
Published: April 2003

Untreated and flame‐retardant‐treated cellulose were thermally decomposed under vacuum and the products were quantitatively analyzed by gas chromatography. An unidentified product at a retention index of 2270 (between 5‐methylfurfural and 5‐hydroxymethylfurfural), α‐ and β‐D‐glucose, and a group of “dimers” that have not been reported previously were found in this study. The identification of this unknown product should assist in studies on the thermal decomposition of cellulose and further the understanding of the mechanism of flame retardancy.
Solution viscosity–molecular weight relationship for polystyrene
Authors: Rogers Morris G.
Published: April 2003

The 10% solution viscosity has been used extensively as a measure of molecular weight for the commercial production of polystyrene. Recently, poor correlations have been observed between 10% solution viscosity and molecular weight as measured by gel permeation chromatography. Lowering the concentration improves the correlation. At 0.2%, the log–log plot of viscosity versus molecular weight becomes linear.
Sulfoalkylation of a polybenzimidazole with propanesultone
Authors: Jenöszita  , Marvel C. S.
Published: April 2003

Poly‐2,2′‐(m‐phenylene)‐5,5′‐bisbenzimidazole has been alkylated with propanesultone to yield polymers which are readily dyed with basic dyes. Propanesultone has been used to convert cellulose, starch, phenolformaldehyde resin, and various vinyl copolymers into hydrophilic materials which dye readily or act as ion exchange resins.1–5 It seemed likely it would react with a polybenzimidazole to make the polymer more water absorptive and readily dyeable with basic dyes. Hence this work was undertaken.
Effect of mixing on melt flow properties of high‐density polyethylene
Authors: Hirata Sadao , Hasegawa Hiroshi , Kishimoto Akira
Published: April 2003

An investigation has been made into the effect of mixing by a screw extruder upon the molecular characteristics and the melt flow properties of high‐density polyethylene. The crosslinking between molecules predominates over the scission of a molecule at an early stage of mixing, but with further increase in the degree of mixing, this situation reverses itself to bring about the formation of branched polymers. Static flow and dynamic viscoelastic properties of molten high‐density polyethylene change considerably with increase in the degree of mixing. The apparent viscosity drops rather sharply after mixing. The dynamic properties for the original resin show smaller frequency dependence of the viscosity and larger dependence of the rigidity than those for extrudates. The relaxation spectra become broader with increase in mixing. These may mainly be due to the change of the molecular characteristics of high‐density polyethylene with mixing by an extruder.
Studies on nitroaniline–sulfuric acid compositions: Aphrogenic pyrostats
Authors: Poshkus A. C. , Parker J. A.
Published: April 2003

Nitroaniline‐sulfuric acid compositions, a source of a new class of aphrogenic pyrostats (intumescent fire‐quenching agents) have been studied. Thermogravimetric analysis of the compositions and their expansion products was carried out. The chemical compositions of the foams were determined, and considerable similarity was noted. Sulfur is present exclusively as sulfonic acid groups. Appreciable deamination occurs during expansion, particularly at higher acidic content. Sulfur dioxide and water are major gaseous constituents. Only 2‐ and 4‐nitroanilines can be converted into voluminous foams; they behave like difunctional monomers. 3‐Nitroaniline expands only slightly into brittle products; it acts like a trifunctional monomer.
Environmental stress relaxation studies of polymers: Effect of alcohols on polyethylene
Authors: Nisizawa Mizuho
Published: April 2003

The method of stress relaxation has been used to study stress decay behavior in polyethylene–alcohol systems. The behavior of stress decay in polyethylene under alcohols was observed and the respective activity forward stress decay of alcohols on polyethylene was obtained.
Weathering of plasticized poly(vinyl chloride)
Authors: Dunn P. , Oldfield D. , Stacewicz R. H.
Published: April 2003

A series of flexible plasticized poly(vinyl chloride) (PVC) compositions containing different organotin compounds and ultraviolet absorbers has been exposed for 4.5 years at four outdoor sites in Australia with widely differing climatic conditions. Loss of plasticizer by evaporation during the exposure was measured and an empirical correlation was found with the average daily maximum temperature at each site. The relative effectiveness of the organotin compounds and ultraviolet absorbers in preventing deterioration of the PVC was estimated by measuring the viscosity of the polymer after exposure. This method of assessment is compared with the results of mechanical tests on the specimens.
Functionality determination of hydroxyl–terminated butadiene prepolymers
Authors: Consaga John P.
Published: April 2003

Functionality of hydroxyl–terminated butadiene prepolymers (HTPB) was determined from gel point measurements as described by Strecker and French.2 Commercial HTPB samples had functionalities ranging from 1.9 to 2.6, with most of the material close to 2.0. In order to calculate functionality from gel point measurements, the hydroxyl content of the HTPB must be known. A method was developed which gave reproducible results. Curing agents used in the gel studies were viscous liquid poly‐functional isocyanates with functionalities of 2.00 and 2.50. An extensive study showed that no side reactions were occuring with the isocyanates at the temperatures employed. It is estimated that the precision of the method is ±0.80%. Functionality calculated by dividing molecular weight by equivalent weight results in lower values in all cases when compared to gel point measurements.
Adhesive bonding of polyethylene
Authors: Morris C. E. M.
Published: April 2003

The treatment of polyethylene film with aqueous ammonium peroxydisulfate solutions prior to adhesive bonding to aluminum has been studied. Such pretreatments resulted in the formation of adhesive joints of high strengths when bonded with a conventional epoxy adhesive. The effect on the tensile shear strength of adhesive joints of variations in the treatment time and temperature and the peroxydisulfate concentration has been examined. The use of certain catalysts for the reaction has also been studied. Tensile shear strengths at least as high as with other pretreatment methods have been obtained.
An investigation into the high temperature strength and reinforcement of natural rubber
Authors: Harwood J. A. C. , Payne A. R. , Whittaker R. E.
Published: April 2003

The failure criterion for amorphous polymers relating hysteresis at break with energy input to failure in tensile stress–strain tests was found to be obeyed only at very high or very low temperatures in natural rubber. Tensile results between about 80°C and 130°C show a high degree of scatter, and this behavior is attributed to the ability of natural rubber to crystallize at high strains. The modification of tensile properties by the addition of carbon black in natural rubber is also discussed and compared with published results from SBR. The effect of changing the degree of crosslinking on the failure properties in both dicumyl peroxide and sulfur‐cured vulcanizates of natural rubber is also considered. It is found that differences in failure properties can be accounted for by the use of a crosslinking parameter from simple rubber elasticity theory in some of the failure equations.
A new photoelastic method for evaluating durability of plastics
Authors: Ohishi Fujio
Published: April 2003

This work was undertaken to measure quantitatively the quality change and crack development caused by degradation of plastics with the new photoelastic scale (P scale) using split circular ring‐type specimens (C specimen). For an example, a polycarbonate specimen was used under various conditions—photodegradation, thermal degradation, solvent cracking, solvent action, and alkaline degradation. The results indicate that this method is useful for evaluating durability of plastics, and a merit of the method is to provide quick, convenient, nondestructive means of measurement with simple equipment. Besides, this C specimen is easily deflected by a spring plate with two holes. Therefore this method is also applicable to the investigation of effects of deformation on various degradations of plastics.
Energy absorption in polymeric foams. I. Prediction of impact behavior from instron data for foams with rate‐independent modulus
Authors: Meinecke Eberhard A. , Schwaber David M.
Published: April 2003

The processes of energy dissipation in polymeric foams are discussed. Theoretical considerations and experimental results show that impact behavior of foams with a rate independent modulus can accurately be predicted by Instron data.
The solubility of poly(vinylidene chloride) in solvent mixtures
Authors: Wessling Ritchie A.
Published: April 2003

Effective solvents for poly(vinylidene chloride) (PVDC) were obtained by mixing a polar aprotic solvent with a less polar solvent of cyclic structure. The polar components included sulfoxides, N,N‐dialkylamides, and N‐alkyl lactams. The cyclic cosolvents included aliphatic and aromatic hydrocarbons, ketones, ethers, and thioethers. The problem of solubility of a crystalline polymer in a mixed solvent was analyzed by extending the Flory theory of melting point depression to three component mixtures. The results predict that favorable mixtures arise when at least one of the components interacts strongly with the polymer but is nearly incompatible with the cosolvent. This is in qualitative agreement with the observed behavior of PVDC.
An improved block osmometer used to determine the molecular weight distribution of commercial poly(vinyl chloride)
Authors: Hayduk W. , Kelly B. D.
Published: April 2003

Commercial PVC was fractionated into five fractions by the incremental addition of a nonsolvent to the polymer solution. The number‐average molecular weights of the original sample and fractions were determined by osmometry. The weight‐average molecular weights of the sample and fractions were also determined by means of viscosity measurements and by the application of a Mark‐Houwink type of equation. From a knowledge of the polydispersity of each fraction and the assumption that the number distribution of molecular weights was Gaussian, the molecular weight distribution for the composite sample was determined. The block osmometer used incorporated most of the features found useful in earlier work to facilitate rapid and reliable osmotic pressure measurements. In addition, microvolume‐regulating valves were utilized in the capillary tube lines to permit an independent precise positioning of the interface level in either capillary.
Studies on tack of pressure‐sensitive adhesive tapes: On the surface contamination by adhesive mass after peeling
Authors: Toyama M. , Ito T. , Moriguchi H.
Published: April 2003

The presence of adhesive residue on the surface of various adherends after peeling has been confirmed using a tracer technique. Adhesive bonding is found to break by a cohesive mechanism, although the unbonding process seems apparently to be due to intersurface failure. This result supports the concept for adhesive bond breaking proposed in the preceding paper: The unbonding proceeds from the viscoelastic deformation of the adhesive mass around the wetted spots on the surface. As the number of spots in a unit area is controlled by surface energy, the tack value is dependent on the critical surface tension of the adherends.
Internal catalysis of reactions of activated vinyl compounds via tertiary amino substituents in cotton cellulose
Authors: Rowland Stanley P. , Brannan Mary Ann F.
Published: April 2003

The tertiary amino groups of 2‐diethylaminoethyl substituents in cotton cellulose have been found to be effective catalysts for reactions of activated vinyl compounds with cellulosic hydroxyl groups. These reactions proceed more slowly and to lesser extents at equilibrium than the corresponding reactions catalyzed by quaternary ammonium substituents. The crosslinking of cotton cellulose with divinyl sulfone is catalyzed by (C2H5)2NCH2CH2 substituents and by (C2H5)2NCH2CH(OH)CH2 substituents, with the development of moderate levels of wrinkle recovery. On the other hand, only the former substituents catalyze the reorganization of the crosslinkages during recure (160°C, 10 min), with substantial increases (40°) in wrinkle recovery angles. These same 2‐diethylaminoethyl substituents are effective in catalyzing the reorganization of crosslinkages from divinyl sulfone which are introduced into the cotton by conventional external catalysis (i.e., NaOH); this effectiveness can be overcome by the introduction of excessive crosslinkages into the cellulosic composition.
Separation of liquid mixtures by using polymer membranes. II. Permeation of aqueous alcohol solutions through cellophane and poly(vinyl alcohol)
Authors: Huang Robert Y. M. , Jarvis Neil R.
Published: April 2003

The permeation and separation characteristics of four different alcohol—water systems through cellophane and poly(vinyl alcohol) membranes were investigated. The homologous series of linear alcohols n‐propanol, ethanol, and methanol as well as isopropanol were studied. A specially designed permeation cell was used to study permeation rates at temperatures ranging from 30° to 50°C. The dependency of both permeation and separation on the molecular size and shape of the permeating species was discussed qualitatively. The temperature dependence of the permeation rate for both pure compounds and binary mixtures was expressed by Arrhenius‐type relationships. The rate was found to increase with increasing temperature while the separation decreased. Activation energies of 4–9 kcal/mole were calculated for alcohol—water solutions through cellophane, and of 8–15 kcal/through poly(vinyl alcohol). Departure of permeation rates from the ideal rates were discussed in terms of permeation “enhancement” or “depression.” These phenomena were explained in terms of both the plasticizing action of water and the “clustering” of water molecules within the polymer network.
Rheological interpretation of heat generation associated with fatigue of polycarbonate
Authors: Higuchi Masakazu , Imai Yasufumi
Published: April 2003

Temperature change was measured of polycarbonate under monotonically increasing tensile and pulsating tensile loads. In the former case, the specimen temperature began to rise when an appreciable amount of viscoelastic strain was noticed on the stress—strain diagram. The rise, θv, could be formulated as a function of the viscoelastic strain, εv:

In fatigue tests, the average temperature began to rise immediately after the decrease due to the thermoelastic effect. The amount of the heat generation, σ, was nearly constant for each cycle throughout the fatigue process and has a relation to the fatigue life, Nf, (αa)·Nf = constant, where a is another adjustable constant. From a rheological aspect of dissipation energy, the equation is transformed to a relation between the viscoelastic strain and the fatigue life as εV1/2 · Nf = constant, which is similar to the one for metals given by Manson and Coffin.6 The temperature rise in the fatigue was also related to the viscoelastic strain. The relation is of the same form as for static tension but less by a factor of one order.
A boat‐casting technique for the preparation of very thin plastic films suitable for optical studies
Authors: Humphrey J. S.
Published: April 2003

A meniscus coating technique utilizing a Teflon “boat” for dispensing a viscous solution of a polymer in a volatile solvent upon a suitable substrate provides very thin plastic films (>ca. 0.5 μm) which are usually of acceptable optical quality for spectrophotometric measurements.
Enhancing the permeation characteristics of polyethylene by membrane irradiation in the fully swollen state
Authors: Siegel Richard D. , Coughlin Robert W.
Published: April 2003

Fully swollen, low‐density polyethylene films were irradiated, vacuum dried, reswollen, and subsequently permeability tested using tritiated toluene and benzene as penetrants. The treatment improved the permeability of polyethylene up to 88%, with the enhancement strongly dependent on the choice of the irradiation solvent. These results suggest a potentially practical process for improving the performance of semipermeable membranes.
Electroplating on crystalline polypropylene. II. Injection molding and adhesion
Authors: Fitchmun D. R. , Newman S. , Wiggle R.
Published: April 2003

This paper describes the effect of injection molding conditions (melt temperature, mold temperature, and fill time) and etch conditions on metal adhesion in electroplated isotactic polypropylene (PP). It is found that injection molding PP homopolymer produces a lamellar surface morphology which can consistently develop after‐plated peel strengths of 30 lb/in or better as measured by the Jacquet peel test. Surface etching of PP homopolymer prior to plating develops crack patterns characteristic of injection molding; a directional crack pattern is always evident in specimen surfaces crystallized under shear. The surface pattern is developed in the oxidative process by swelling of amorphous material, followed by oxidative dissolution and oxidative stress cracking. Additionally, the depth and number of the surface cracks is a function of the solvent swell and acid etch times. Crack depth increases in lamellar surfaces as the sample immersion times are increased; however, as crack depth increases, crack density decreases.

Metal‐to‐polymer adhesion, as measured by the peel test, represents a balance between crack depth and diminished surface strength incurred in the oxidative cracking process. Although peel adhesion usually increases with crack depth, overetching may actually reduce adhesion even though the crack depth has been increased. Any advantage from deeper cracks may, therefore, be offset by a loss in the surface strength of the polymer. Comparison of the surface and cross‐sectional crack patterns in TiO2‐filled PP indicates that the surface morphology is similar to that of unfilled polymer. Molding conditions that produce the desired morphology is similar to that of unfilled polymer. Molding conditions that produce the desired morphology are important for high peel adhesion values but appear to be less critical than in unfilled PP. A propylene–ethylene copolymer (90/10) developed 12–15 lb/in. peel adhesion—50% lower than for the filled and unfilled homopolymer when molded under similar conditions; peel adhesion in this composite system is, however, relatively insensitive to changes in molding conditions. Aging of 2–3 weeks after plating is required for maximum peel adhesion in all samples studied.