bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear viscoelastic behavior of cellulose acetate butyrate
Authors: Sharma M. G. , Wen P. R. 
Published: December 2004

AbstractCreep experiments under variable loading conditions are reported for tubular specimens of cellulose acetate butyrate. Experiments include the application of torque loading that corresponded to various loading programs. Results indicate that the material response in creep is nonlinear. The character of the results is described reasonably by assuming the behavior as linear and using the Botzmann superposition principle. However, the interpretation of the data based upon a non‐liner creep law and modified superposition principle yields better agreement with experiments in certain cases.
Degradation of polymeric compositions in vacuum to 10−9 mm Hg in evaporation and sliding friction experiments
Authors: Buckley D. H. , Hohnson R. L. 
Published: December 2004

AbstractSolid compositons studied included PTFE, PCFE, polyimides, both filled and unfilled, and fluorocarbon telomers. Evaporation experiments were conducted at ambient temperatures to fluorocarbon telomers. Evaporaton experiments were conducted at ambient temperatures to 1100°F and pressures to 10−8 mm Hg. Various molecular weights of different polymers were examined. Results indicate that evaporation rates in vacuum for polymers vary with molecular weight. Friction and wear experiments were conducted with a 3‐16‐inch‐radius rider hemisphere (usually polymer) sliding on a flat disk (various materials) at speeds to 1480 feet per minute with a 1000‐gram load on the rider specimen and at an ambient pressure of 10−9 mm Hg. Fillers were found to influence markedly the wear of PTFE and PCFE in vacuum as a result of changes in heat dissipation properties, but they showed little or no influence on friction.
Kinetics of spherulitic crystallization
Authors: Baer Eric , Collier J. R. , Carter D. R. 
Published: December 2004

AbstractPolymer crystallization is discussed with attention given to primary nucleation, spherulite growth, and bulk crystallization. Primary nucleation is the area of least knowledge, and the authors discuss the kinetics of nuclei appearance and recent observations concerning the effects of foreign materials and surfaces. Spherulitic growth rates are discussed in general and specifically with respect to data at low degrees of supercooling in conjunction with secondary nucleation theory. The Avrami Theory and its limitations are discussed in the interpretation of bulk crystallization data. The authors propose that n = 4 in all cases and that the Avrami Theory be used for calculating the primary nucleation rate, kn, not for determining n itself.
Thermal decomposition of unsaturated materials
Authors: Bailey W. J. 
Published: December 2004

AbstractUnsaturated polymers thermally degrade by a number of different mechanisms depending on the structure of the polymer and the experimental conditions. By use of deuterium tagging it was shown that polyisobutylene degrades stepwise from the end by a cyclic unimolecular mechanism. Volatile products from isotactic polypropylene contained 75% propane at 340°, 64% n‐pentane at 375° and 49% propylene plus 12% isobutylene at 495°. Polyethylene was shown to give mostly propylene at lower temperatures but gave a 60% yield of ethylene at 600°.
Polyimides—new high temperature polymers: H‐film, a polypyromellitimide film
Authors: Heacock J. F. , Berr C. E. 
Published: December 2004

AbstractH‐Film is a polypyromellitimide which results from polycondensation of pyromellitic dianhydride and an aromatic diamine. Its unique blend of thermal, physical, and electrical properties make it an outstanding candidate for a variety of electrical and non‐electrical end‐use applications. These properties recommend H‐Film for use as Class H (220°C) electrical insulation. Thermal aging of this polymeric film to embrittlement in air will require on the order of ten years at 250°C (482°F), one year at 275°C (527°F), and three months at 300°C (572°F). Even greater thermal durability in inert atmospheres has been observed. Our continuing thermal characterization studies on this polypyromellitimide have resulted in data relating to weight loss and decomposition products.
Structure‐property studies in polymer melt rheology
Authors: Huseby T. W. , Gogos C. G. 
Published: December 2004

AbstractVarious continuum theories of viscoelastic materials have predicted that extrudates issuing from a die will swell and this phenomenon is well known experimentally. One such continuum theory has been formulated by Pao in terms of relaxation times which can be evaluated independently in other tests. Since relaxation times are qualitatively understood in terms of molecular mechanisms, the swelling of extrudates can be given a molecular interpretation. We have found that the phenomenon originates from entanglement and those molecular motions characterized by relaxation times in the terminal zone of the viscoelastic spectrum. Extrudate swelling has been associated also with the capacity of materials to store energy. Since stored energy is also related to relaxation times, there must exist a functional relation between stored energy and swelling. For this same reason there must also exist a relation between swelling and recoverable strain. We have also presented in this paper some data concerning this latter relation.
Degradation of polymers by thermal gravimetric techniques
Authors: Levi D. W. , Reich L. , Lee H. T. 
Published: December 2004

AbstractThe techniques involved in dynamic thermal gravimetric analysis are reviewed. Methods of studying overall kinetics of degradation, especially with respect to evaluation of order of reaction and overall activation energy, are outlined. Some applications to polymers such as Teflon and epoxide resins are described. Since the use of thermal gravimetric results for evaluating thermal stability raises the problem of a suitable standard for describing decomposition, some indices of thermal stability of polymers are discussed.
Relationship between structure and mechanical properties of polyolefins
Authors: Matsuoka S. 
Published: December 2004

AbstractRecent studies of the morphology of semicrystalline polymers have demonstrated the inadequacy of the familiar fringed micelle concept. It is now generally recognized that polyolefins crystallize in a spherulitic form having a skeletal structure of coherent crystals with a fibrous habit. Crystallization occurs in two stages: (1) spherulitic growth of crystalline lamellae, and (2) partial crystallization of residual melt in regions between lamellae. The dependence of modulus on degree of crystallinity in polyethylene indicates that the crystalline network carries much of the elastic energy acquired when the plastic is subjected to stress. Two of the mechanical transitions are also related to morphological structure. The high temperature or α transition is attributed to motion within lamellae while the intermediate or β transition is attributed to motion in disordered regions between lamellae.
The deterioration of polypropylene by oxidative degradation
Authors: Oswald H. J. , Turi E. 
Published: December 2004

AbstractAn explanation is presented to account for the deterioration of the mechanical properties at very low concentrations of absorbed oxygen. The induction time as measured by the oxygen absorption technique overestimates the time to failure with respect to the mechanical properties. Furthermore, it is shown that the extrapolation of accelerated aging data as obtained at elevated temperatures should not be carried out below 50°C. Data are presented to show that an anti‐oxidant is one of the major constituents of a stabilizer system against UV radiation, because the oxidative degradation mechanism is involved. A modified oxygen uptake equipment is described which allows the simultaneous determination of the oxygen absorption and the deterioration of the mechanical properties on the same sample.
Fracture topography of brittle polymers
Authors: Newman Sanford B. 
Published: December 2004

AbstractFracture surfaces record the kinetics of failure at two levels in the structure of polymeric solids. The first is evidenced by the formation of geometric markings resulting from the interaction of the primary fracture front with secondary fractures developing radially just ahead of the primary fracture. These markings are often visible to the unaided eye and have minimal dimensions in the micron range. The second fracture phenomenon appears to involve the orientation of molecular chains or bundles. Such orientation manifests itself in the interference‐color producing film found on the fracture surfaces of poly (methylmethacrylate) and polystyrene. It is also apparent in the free or adherent film found on the surfaces of large fractured crazes. Some evidence is presented for the existence in these films of chain bundles 30A or less in diameter. It would seem that similar mechanisms are operating in the production of “craze matter” and of fracture surface films.
Weathering of epoxy resins systems
Authors: Pschorr F. E. , Cianciarulo A. N. 
Published: December 2004

AbstractThis article presents data on outdoor weathering of unfilled epoxy resins. The data have been accumulated after five years of weathering. The anhydride cured epoxy resin system was least affected by outdoor exposure. In addition, systems with higher deflection temperatures were more resistant to attack by outdoor exposure than those of lower deflection temperatures. It was also evident that heat curing is better than curing at room temperature. Hardness, for all systems, decreased with exposure time. Microscopic examination of the exposed systems showed that surface change closely correlated with changes obtained in the mechanical and electrical properties tested in this program. Systems showing the greatest change also had the worst surface appearance.
The nature of time effects in solid polymeric systems
Authors: Andrews R. D. 
Published: December 2004

AbstractThe time‐dependent mechanical behavior of solid polymers can be classified into linear viscoelastic, nonlinear viscoelastic and rheological types. The linear viscoelastic theory has now been worked out in detail, and applies with particular success to amorphous polymers above their glass transition temperature. Examples of systems falling outside this category are principally discussed, including glassy, composite, and crystalline materials. These systems are characterized by the fact that structure and structural changes are playing a major role in the mechanical behavior. Specific theories must be developed in the future which adequately treat this type of behavior.
Stabilization of polypropylene
Authors: Hansen R. H. , De Benedictis T. , Martin W. M. 
Published: December 2004

AbstractThe effectiveness of polyproylene antioxidant systems in other than a simple oxidative environment has been studied. For example, it has been found that contact of stabilized propylene polymers with a number of materials, particularly with plasticized poly (vinyl chloride) and with copper and copper salts, markedly decreases the resistance of the composition toward oxidative degradation. The use of antioxidants having higher molecular weights results in improved retention of stabilization when polypropylene is used in contact with materials such as plasticized poly (vinyl chloride), presumably because partition of the antioxidant from the polypropylene composition is decreased. Antioxidant effectiveness in polypropylene compositions in contact with copper can be greatly increased by the addition of new and more effective copper inbibitors. The usefulness of copper compleming agents such as hydrazides, triazoles, tetrazoles, and derivatives of malonamide and oxamide are compared in polypropylene compositions containing copper dust and antioxidants.
Deformation and failure of plastics and elastomers
Authors: Smith Thor L. 
Published: December 2004

AbstractThe effect of various environmental conditions, other than chemical, on the mechanical properties of amorphous polymers is considered. The response of such polymers to an applied stress or strain depends on the mobility of polymeric chains which in turn is largely a function of free volume. The free volume varies with temperature, pressure, and plasticizer concentration; in the glassy state, it also depends on thermal history and tensile strain. These concepts are reviewed and some illustrative data, primarily from the published literature, are presented. A discussion is also given of the nonlinear viscoelastic properties (in uniaxial tension) of amorphous network polymers in the rubbery state. Methods for characterizing the ultimate tensile properties of such polymers are also described. Finally, some comments are made about the mechnical characteristics of polymers in the glassy state.
The use of visible and ultraviolet spectroscopy to identify carbonyl compunds in photodegraded plastics
Authors: Gray V. E. , Wright J. R. 
Published: December 2004

AbstractA method was developed for identifying certain carbonyl compounds formed in plastics during exposure to carbon‐ac or solar radiant energy. The reaction of aldehydes and certain ketones with phenylenediamines (o‐, m‐, p‐, and N, N‐dimethyl‐p‐) in glacial acetic acid was found to yield stable colored products whose transmittance spectra are charactersitic of the carbonyl compound. Similar colored products were also formed when exposed plastics were dissolved in acetic acid solutions of the diamine. A comparison of the spectra of solutions of the plastics with those from known carbonyl compounds facilitates identification. The method was applied to the identification of carbonyl compounds from photodegraded poly (methyl methacrylate) and cellulose acetatebutyrate.
Radiation‐induced solid state polymerization
Authors: Marans N. S. 
Published: December 2004

AbstractThe literature on radiation‐induced solid state polymerization has been increasing exponentially in the last five years. Major advances have been made in retention of crystalline morphology during polymerization, in stereospecific polymerization, in modification of reactivity ratios in copolymerization and in molecular weight control of the product. However, at the present time, no commercial products have resulted from the study of radiation‐induced solid state polymerization. Chemically induced polymerization techniques have been keeping abreast of this explosive development in the solid state polymerization field and have up to this time precluded the use in industry of solid state polymerization. The major potential at the present time appears to be in the area of producing fibers without additional processing.
Failure of polymeric materials under biaxial stress fields
Authors: Sharma M. G. 
Published: December 2004

AbstractThe paper reviews the various classical failure theories essentially developed for metals and then seeks to show that the same theories with slight modifications could be used to describe failure of polymeric materials. These modifications consist in the consideration of the effect of rate loading on failure behavior. In addition, the paper reports experimental results on failure of two polymeric materials under uniaxial tension loading and several biaxial stress fields corresponding to pure internal pressure, internal pressure combined with tension and torque loadings and several biaxial stress fields corresponding to pure internal pressure, internal pressure cobined with tension and torque loadings. The failure behavior under various stress fields has been studied for maximum principal rates ranging from 0.05 to 60 psi. sec. The predictions based on various criteria of faliure, which considers the effect of rate of loading, are compared with the experimental results. Finally, it is shown that failure behavior under triaxial stress fields can be reasonably predicted from biaxial stress failure data.
The phenomenon of draw resonance in polmeric melts. Part II—correlation to molecular parameters
Authors: Bergonzoni A. , DiCresce A. J. 
Published: December 2004

AbstractThe Phenomenon of draw resonance and the cyclic size fluctuation of an extruded shpae are related to basic changes in the “melt strength” (force per average cross‐sectional area required to draw the molten fiber down under fixed conditions). Melt strength values are obtained by a modified rheometer which consists of a vertical chamber to melt and hold the polymers at 190–250°C, a piston for extrusion, a take‐up system, a strain gauge to measure the drawdown force and a recorder for continuous force‐time plots. Melt strength increases with take‐off speed but not proportionally. At higher velocities, draw resonance is apparent through a sinusoidal‐like variation in fiber diameter. The amplitudes of melt strength and diameter waves are correlated with molecular weight, melt viscosity, swell, melt temperature and take‐off speeds.
Polymerization of 2‐allyl‐1‐methylenecyclohexane by the cyclic polymerization mechanism
Authors: Butler George B. , Miles Marion L. 
Published: December 2004

Abstract2‐Ally‐1‐methylenecyclohexane is a compound which is functionally capable of undergoing polymerization by the alternating intra‐intermolecular propagation mechanism to produce poly[1,8‐methylene[4.3.0] bicyclononane]. This monomer was synthesized and its polymerization through use of cationic and Ziegler‐type initiators was studied. Synthesis of the monomer was accomplished by the following reaction sequence: (1) conversion of cyclohexanone to 2‐allycyelohexanone by reaction wtih allyl bromide and sodium amide and (2) conversion of 2‐allycyclohexanone to the desired monomer by reaction with the phosphorane derived from methyltriphenylphosphonium bromide. Polymerizaton was accomplished by use of boron trifluoride resulting in 44% conversion to polymer, of which 94% was soluble. Through use of infrared and nuclear magnetic resonance techniques, the soluble portion of the polymer was shown to contain 54% of bicyclic units and the remainder to be non‐cyelized monomer units in which the residual unsaturation was composed predominantly of allyl groups.
Thermal and oxidative effects in polyethylenes above 200°C
Authors: Quackenbos H. M. 
Published: December 2004

AbstractThere is considerable literature on the behavior of polyethylene below 200°C and above 400°C. This paper presents results on both high and low density polyethylene between 2000 and 400°C, a range of practical import for various fabrication and processing steps. Practical exposure times may be short and the experimental procedures were designed to give meaningful results for times as low as 1 min. The principal effects are chain‐session and oxidation. Session was isolated by applying an atmosphere of pure nitrogen and proved uite shlow at 300°C but rapid at 400°C. The course of scission and produces discoloration, odor, and rising carbonyl content. A brief discussion is given of the role of diffusion in oxidation.
Development of an impact test for evaluation of weatherability of rigid plastics
Authors: Neuman R. C. 
Published: December 2004

AbstractColor development in outdoor applications has been widely used as an indication of breakdown in plastic materials although this does not always indicate a change in physical properties. Appearance factors are easily and precisely evaluated by measuring color and surface changes. Measurement of physical property changes is more comples and more meaningful. An optimum test method should measure a property with time, environment and sample form. Ideally, the data should determine service life. The test specimen should be adaptable to a variety of samples. Of the many physical tests of weatherability, impact strength appears most interesting. An inexpensive Variable Impact Tester was Modified and Developed for Measuring the effect of aging on rigid PVC. Data are presented showing the relation between impact values and temperature, sample thickness, process conditions and various environmental exposures.
Pressure‐volume‐temperature behavior of polypropylene
Authors: Foster George N. , Waldman Nathan , Griskey Richard G. 
Published: December 2004

AbstractThe pressure‐volume‐temperature behavior for both solid and molten polypropylene was determined for pressures up to 618 atmospheres. These data were measured with a newly developed compressibility device capable of obtaining precise and accurate data. Compressibilities calculated from the experimental data compared favorably to the limited existing literature data. Constants were determined for the Spencer‐Gilmore polymer equation of state for both the solid and molten material.
Internal pressure measurements of diisooctylphthalate and dioctylsebacate
Authors: Bagley E. B. , Wood H. H. 
Published: December 2004

AbstractInternal pressure measurments have been made on two common plasticizers, di‐isoöctylphalate and dioctylsebacate, as a function of temperature. The ratios of internal pressure to cohesive energy density (as calculated by the method of Small) were 1.22 for dioctylsebacate and 1.17 for di‐isoöctylphthalate. As in the case of simpler molecules the product of internal pressure and the square of the specific volume was constant for each plasticizer over the temperature renge studied. This implies that even in the absence of any other effects both an upper and lower critical solution temperature would be expected in mixed systems if the coefficients of thermal expansion of the components of the mixed system are sufficiently different.
The impact behavior of rigid PVC compounds
Authors: Hyndman John R. 
Published: December 2004

AbstractMany rigid PVC compounds show a sharp transition from tough to brittle fracture with decreasing temperature in impact testing, and this temperature becomes a criterion of compound quality in addition to the impact strength observed at specific temperatures. This BT (brittle fracture) has been investigated individuall in commercial and experimental elastomer modified rigid PVC compounds. Factors affecting the BT include speciman thickness, composition and processing conditions. Apparently the discontinuity in impact behavior is a sudden manifestation of a gradual change, resulting in a near ten‐fold decrease in notched impact strength without any obvious change in properties. The BT provides a continuous scale for comparing impact properties of compounds, and is thus more versatile and sensitive than impact tests run at a single temperature.
Compressibility of bulk polymers
Authors: Warfield R. W. 
Published: December 2004

AbstractBulk compressibilities of a series of linear and crosslinked polymers have been measured, in a Matsuoka‐Maxwell apparatus, at pressures up to 10,000 atmospheres and at temperatures to 202°C. These polymers exhibited nonlinear compressibility characteristics and a maximium compressibility of about 15% at 10,000 atmospheres. At slow loading rates, data were obtained for the amorphous polymers which could be expressed as glass‐rubber phase gisgrams. The nature of the observed compressibilities are discussed and the usefulness of the data is indicated.
Fundamentals of plasticating extrusion. I. A theoretical model for melting
Authors: Tadmor Zehev 
Published: December 2004

AbstractA steady state model for melting in a screw extruder has been developed based on the assumption that a stable solid bed of polymer granules is melted by heat that is conducted from a hot barrel and heat that is generated by viscous dissipation in the film that separates the solid bed and the surface of the barrel. The solid bed gradually decreases in width, as it proceeds in the channel, until it disappears at which point the melting is terminated. The model predicts the solid bed width profile and the required length of melting in terms of physical properties, operating conditions, and geometry of the screw. The model has been tested based on experimental data.