bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic mechanical evidence for the glass transition of high density polyethylene
Authors: Paauwe Neil A. , Knox Jack R. 
Published: December 2004

AbstractThe effects of shock cooling and swelling with carbon tetrachloride on the dynamic mechanical spectrum of high density polyethylene have been studied with a torsional pendulum. The resulting spectra have a well‐defined loss peak at −65°C which is associated with the glass transition of high density polyethylene. Similar experiments on polypropylene and low density polyethylene demonstrate the similar effects of these treatments on their glass transitions.
Rheovibron determination of the dynamic moduli of polymer melts
Authors: Shah Basit H. , Darby Ron 
Published: December 2004

AbstractThis article describes the use of the Rheovibron Model DDV‐III‐B with a parallel plate modification of the sample holders to obtain oscillatory data in the shear mode for several high density polyethylene melts. A detailed analysis of the Rheovibron to obtain the dynamic shear: moduli of polymer melts using the new sample holders is given, as well as a procedure for determining the instrument compliance and inertia parameters which must be considered in analysis of the data. Using the principle of time‐temperature superposition, the data are extended to an equivalent frequency range of 1500 rad/sec. These data are compared with those obtained using the Weis‐senberg Rheogoniometer Model R‐17 for the same polymers. It is concluded that reliable measurements for dynamic shear moduli for polymer melts using the Rheovibron Model DDV‐III‐B with the modified sample holders can be made for melts with indices of about 5 or less (i.e., zero shear viscosities of 6.0 × 104 poise or greater).
Induced photodegradation of styrene polymers: A survey
Authors: Sheldrick G. E. , Vogl O. 
Published: December 2004

AbstractAlthough polymeric materials have a relatively minor role in our solid waste disposal problems, they display a particular prominence as litter because of their environmental permanence, Photodegradation has been suggested as one possible solution, but considerable debate has centered on the need, costs, and limitations of such degradable systems. The chemical mechanisms involved in practical photodegradation are illustrated by a review of the oxidation schemes for normal and sensitized polystyrene. The different mechanisms associated with the use of additives, comonomers, and halogens are considered in some detail. A listing of patent literature relating specifically to photodegradable polystyrene is included in the review.
Impact strength of polymers: 1. The effect of thermal treatment and residual stress
Authors: Broutman Lawrence J. , Krishnakumar Suppayan M. 
Published: December 2004

AbstractThe effect of thermal annealing and quenching on the notched Izod impact strength of several polymers has been studied. Primary emphasis was placed on polycarbonate, but ABS, PVC, polysulfone, and polymethylmethacrylate were also studied. It was determined that residual stresses created by thermal quenching from above the glass transition temperature can have a great effect on impact strength for the polycarbonate, PVC, and polysulfone polymers studied. In fact, it is shown that the thickness transition observed in impact strength for polycarbonates is governed by the residual stresses and not by thickness. In polycarbonates, quenched sheets up to 3/8 in. in thickness have shown impact strengths of 18 ft‐lb/in. whereas sheets 1/8 in. in thickness can be embrittled by annealing, showing an impact strength of 2 ft‐lb/in. However, it has been shown that this embrittlement results from the absence of residual stress. Residual stresses having maximum values up to 3000 psi (in Compression) have been determined at the polycarbonate sheet surface using birefringence measurement techniques. The existence of these compressive stresses is postulated to restrict the extent of craze growth at the notch tip, and the impact specimen can yield rather than fail in a brittle manner if the stress state is sufficient.
Phase structure and continuity in polymer blends and composites
Authors: Sperling L. H. 
Published: December 2004

AbstractPolymer blends and composites are composed of two different components, and usually, two different phases. Sometimes one phase is continuous and the other clearly discontinuous. Often, however, both phases retain some degree of continuity, as in certain fiber reinforced composites, block copolymers, materials composed of alternating lamellae structures and interpenetrating networks. A semi‐empirical theory is developed to express mathematically not only the known structures, but also two‐phase morphologies not yet synthesized or characterized. Many structures both real and proposed are shown to exhibit dual phase continuity, although for most systems, one phase can be said to be “more continuous” and the other “less continuous”.
A study of chain addition polymerizations with temperature variations: II. Thermal runaway and instability—a computer study
Authors: Biesenberger J. A. , Capinpin R. , Yang J. C. 
Published: December 2004

AbstractA computer study was made to determine the thermal ignition criteria and ignition boundaries for chain‐addition polymerization in a well‐mixed batch system using a simple kinetic model. The occurrence of thermal runaway was shown to be a function of initiator type, feed conditions, and heat transport parameters. It was found that thermal runaway does not occur early with respect to monomer and initiator conversions and that for strongly dead‐ending systems, the sensitivity characteristic of ignition disappears. The role of various dimensionless parameters in characterizing reaction behavior is also discussed.
Strain‐induced crystallization II. Subsequent fibrillar‐to‐lamellar transformation
Authors: Yeh G. S. Y. 
Published: December 2004

AbstractPart II discusses numerous examples of a morphological fibrillar‐to‐lamellar transformation that has reportedly been observed in stretched polymers upon additional thermal treatment (or TIC), Stretched polymers containing initially a typical fibrillar morphology for either crystallites in cold‐drawn polymers, crystallites induced by stretching, or simply non‐crystalline fibrils can yield a more or less lamellar morphology after the thermally‐induced transformation. There is no evidence of extended‐chain crystals present in either the original fibrils or the transformed lamellae; however, the extent of the transformation is strongly dictated by the annealing conditions and the stretch ratios, and therefore the local strains on tie molecules between the crystallites. Of particular interest is the observation of lamellar formation in conjunction with decreasing stress (or increasing length) during TIG under strain. This is in conflict with the generally expected stress increase if chain folding is presumed to occur during formation of lamellae, Consequently, it leads to the conclusion that lamellae form from prefolded structures during TIC. In the light of this surprising conclusion, available evidence on the presence of structure or non‐Gaussian chain segments in the amorphous state is also cited. Included are the most recent neutron scattering results from concentrated solutions of polystyrene.
Disruptive processes in the shear crystallization of poly(ethylene oxide)
Authors: Fritzsche A. K. , Price F. P. , Ulrich R. D. 
Published: December 2004

AbstractThe crystallization behavior of samples of poly(ethylene oxide) of varying molecular weights and molecular weight distributions has been studied under varying conditions of shear rate and temperature. These experiments have been carried out in two devices. One is a shearing parallel‐plate instrument that allows direct observation of the crystallizing medium. The other is a shearing concentric‐cylinder dilatometer. In general, shear enhanced the rates of crystallization and nucleation. However, conditions were encountered under which shear retarded crystallization and/or nucleation. Combination of the data from these two devices suggests that, under certain shearing and sample conditions, chain slippage and particle fracture lead to decreased apparent rates of nucleation and/or crystallization.
Flow‐induced crystallization of polypropylene in stretched ribbons
Authors: Andersen P. G. , Carr S. H. 
Published: December 2004

AbstractRibbons of molten polypropylene have been extruded into a thermostatted chamber and subjected to elongations ranging as high as 4400‐fold. Some of these ribbons have been shown to possess the unusual ability of recovering nearly all of the strain from large levels of stretch (≤100 percent). This property, as well as the magnitude of the tensile yield drop, has been found to be directly proportional to the uniaxial character of the flow present at the moment of crystallization. The structure in the final solid films has been characterized by wide angle X‐ray diffraction and crystal orientation distribution. Both of these factors have been found to be proportional to the character of flow at the moment of crystallization. Finally, the temperature in the thermostatted chamber has been shown to affect the character of the flow.
Structure studies of chemically etched poly(ethylene terephthalate) film
Authors: Adams G. C. 
Published: December 2004

AbstractA macrostructure consisting of 1500 Å long network, elements has been studied in unoriented and oriented poly(ethylene terephthalate) film. The long dimension of the structure is oriented transverse to the stretch direction. A length to width ratio of approximately 10:1 is observed. The structure is observed by scanning electron microscopy after room temperature etching with n‐propylamine under special conditions. Also studied are weight loss measurements for up to 80 hrs of etching and molecular weight degradation by gel permeation chromatography. The induction time before weight loss commences depends on sample elongation and thermal history. A coincidence of the following times are observed: (I) commencement of weight loss, (2) development of a well‐defined macrostructure by SEM, and (3) completion of molecular weight degradation. Therefore, visual evidence of a macrostructure occurs when weight loss has commenced which requires degradation to products soluble in the etchant. The GPC curves vs rich time show that etched film oriented to a crystalline state possesses two molecular weight peaks. The peak for polymer in which no degradation occurred is replaced by a peak for polymer of nine to ten repeat units which is highly crystalline and, therefore, resistant to further attack.
Using system identification to determine the thermal properties of plastics
Authors: Peter John W. , Tarvin Ronald L. 
Published: December 2004

AbstractThis article describes a new experimental and analytical method for determining the specific heat and thermal coductivity of plastic materials. This method arrives at these temperature‐dependent properties by analyzing the thermal history of a slab of the plastic material. The procedure is as follows: 1) A partial differential equation model of the heat flow through the slab is established a priori. 2) A varying heat flux is a applied to the slab, and temperature readings throughout the plastic are recorded at fixed time intervals. 3) This temperature data is fed into a digital computer (along with the established mathematical model) and the required specific heat and thermal conductivity values are extracted. The extraction is done by using the maximum likelihood system identification technique.
Relationship between torque and capillary rheometer thermal stability measurements for PVC compounds
Authors: Collins E. A. , Metzger A. P. , Furgason R. R. 
Published: December 2004

AbstractA method is described to predict the time‐temperature behavior and hence thermal stability of PVC melts in a Brabender Plasticorder torque rheometer from basic rheological data(flow and thermal stability observations) obtained on an Instron capillary rheormeter. The predicted and experimentally determined values of the Brabender thermal stability are shown to be in good agreement.
Rotational molding heat transfer—an update
Authors: Throne James L. 
Published: December 2004

AbstractIn earlier works, a complicated circulation model was chosen to describe heat transfer to powder in a rotating mold. In order to satisfy the model, an experimentally‐determined empty mold temperature response was used. An alternate heat transfer model, in which the powder is assumed to be in static contact with the mold surface at all times, shows significant temperature deviation from the earlier model. The predicted time for complete sinter‐melting is much closer to earlier experimental data than the predicted times from the circulation model. The melting time is seen to follow the form given by the Goodman penetration model. Complete heating and cooling profiles are more easily generated using this static model, and a new interpretation of the air cooling step in the heat transfer cycle results.
The influence of anisotropic phase structure on the properties of crystalline polymers
Authors: Samuels Robert Joel 
Published: December 2004

AbstractBy combining quantitative molecular, microscopic and macroscopic information from an oriented crystalline polymer, it becomes possible to unify, predict, and explain not only processing behavior but such important material properties as failure, shrinkage, modulus, yielding, melting, and storage and loss moduli. Among the advantages gained by this approach are the ability to: (a) identify the particular phase of the two‐phase system which controls a given property‐(b) correlate internal structure quantitatively with a large number of seemingly different types of properties; (c) identify quantitative behavioral rules which are generally valid for Very different crystalline polymers; (d) clarify component roles such that new techniques and processes result; and (e) predict the properties of a crystalline polymer for structural states not previously tested. Using two dissimilar crystalline polymers, isotactic polypropylene and poly(ethylene terephthalate), as examples, the general validity and unifying power of the structural approaches is demonstrated.
The mechanism of the stereoregular polymerization of 2‐vinylimidazole and 2‐vinylbenzimidazole
Authors: Lando J. B. , Litt M. , Shimko T. , Kumar N. G. 
Published: December 2004

AbstractConformational energy calculations on poly(2‐vinylimidazole) (PVI) and poly (2‐vinylbenzimidazole) (FBI) indicated that the syndiotactic polymer would exhibit systematic intramolecular hydrogen bonding between side groups along the chain, while the isotactic polymers could not. This fact, together with our previous wor.k using solvent effects to produce highly syndiotactic poly(methacrylic acid) during radical polymerization, indicated that similar techniques could be applied in the radical polymerization, of 2‐vinylimidazole and 2‐vinylbenzimidazole. These mpnomers were polymerized over a wide temperature range using cobalt 60 gamma radiation as the initiator. The conditional probabilities obtained from NMR spectra of these polymers could be fit by second order Markov statistics (FBI) and extended second order Markov statistics (PVI). The difference reflects the effect of the bulkier benzimidazole side group. The nature of the conditional probabilities needed to fit the data for PVI suggest that the stereoregularity depended on the number of consecutive terminal r placements at the end of the growing radical. A marked solvent effect was observed was attributed to the hydrogen bonding strength of the solvent and its ability to disrupt the r directing polymer hydrogen bonding.
Nonlinear viscoelasticity of “hard elastic” polypropylene fibers
Authors: Chen Hyland Y‐L , Ko Frank K. , Lundberg John L. 
Published: December 2004

Abstract“Hard elastic” polypropylene fibers respond nonlinearly to stress at all strains. Low tenacities at break (less than 1 g/denier), low moduli of elasticity (slopes of stress‐strain curves from 2.8 to 28 g/denier), and large breaking extensions (over 800 percent) are characteristic of “hard elastic” fibers. Behavior in simple extension, cyclic extension, and stress relaxation can be represented by a quasi‐linear viscoelastic model which uses a continuous relaxation spectrum and a quasilinear relation between stress history T(t)and strain history λ(t):

where Te[λ(t)] is the elastic response. When creep data are available, this model should provide a unified representation of experimental observations.
The mechanical and thermal properties of graphite fiber reinforce polyphenylquinoxaline and polyimide composites
Authors: Sung Nak‐Ho , McGarry Frederick J. 
Published: December 2004

AbstractComparative studies were made on the fabrication characteristics, mechanical properties and thermal stabilities of three commercially available composite systems based on linear monoether polyphenylquinoxaline, P13N polyimide, and Skybond 703 polyimide, reinforced with Modmor II graphite fibers. Fabrication parameters and prepreg conditions were related to the properties of the laminates. Interlaminar shear strength and flexural properties were evaluated before and after the thermal aging at 600°F for periods up to 500 hrs. Thermal degradation of composites at various stages of thermal' aging was studied using optical and scanning electron microscopes.
Morphology and dynamic mechanical spectra of crystalline copolymers of ethylene and acenaphthylene
Authors: Bailey F. E. , Walter E. R. 
Published: December 2004

AbstractIn a previous paper, results of morphological studies using electron microscopy and X‐ray diffraction were reported concerning random and non‐random olefin copolymers of ethylene. As comonomers, relatively low concentrations of n‐alpha alkenes and 5‐methyl norbornene‐2 were used. It was tentatively concluded that one possibility for morphological changes observed in the n‐alpha alkene copolymers was a change in direction of chain folding. These studies have been continued with copolymers of ethylene and acenaphthylene. The intent was to pursue effects of vicinal substitution; however, the result was to produce ethylene copolymers of quite high comonomer content which were crystalline and showed no evidence of an independent beta mechanical transition. Further, definite evidence was found to indicate a change in the direction of chain folding in the polymer crystals.
Thermal analysis of dielectric insulation, ethylene/propylene rubbers, and cross‐linked polyethylenes decomposed in a nitrogen atmosphere
Authors: Abou‐Shaaban Rafiq R. A. , Haberfeld Joseph L. , Barrall Edward M. , Johnson Julian F. , Simonelli Anthony P. 
Published: December 2004

AbstractThe techniques of thermogravimetric and derivative thermogravimetric analyses have been applied to the determination of temperatures and heats of decompositions of four ethylene/propylene rubbers and seven cross‐linked polyethylenes in nitrogen. These materials are commonly used in the wire and ruble industry as dielectric insulation. The polymers were found to decompose in at least three overlapping stages. Each stage has an activation energy characteristic of the process. Differential thermal analysis was significantly less useful in this study due to the conflict of the endothermal heat of vaporization and the exothermal heat of decomposition.
Parameter testing of epoxy polymer concrete
Authors: Tolbert R. N. , Hackett R. M. , Baluch M. H. 
Published: December 2004

AbstractThe ultimate strength of polymer concrete was investigated utilizing epichlorohydrin/bisphenol A‐type epoxy resin. Parameters were tested in an effort to conclude how variation of a specific parameter would affect the compressive strength of the polymer concrete. The parameter testing included studies to determine the effect of the polymer loading; the catalyst; the exothermic reaction; aggregate type, gradation and moisture content; curing age; and aggregate additives of portland cement and lime‐stone powder.
Mechanical properties of biaxially oriented poly(vinyl chloride)
Authors: Brady Thomas E. 
Published: December 2004

AbstractThis report describes the influence, of (a) degree of biaxial orientation, (b) stretching rate, and (c) stretching temperature on the tensile, dynamic mechanical and dielectric properties of non‐impact modified PVC. A new parameter designated “planar strain” is used to correlate anisotropic property values with both equal and unequal biaxial stretching in a single two‐dimensional plot, thereby providing a direct comparison of the effects of two or more biaxial stretching ratios. It is shown that optimum stretching conditions depend to some extent upon end use and that a 2 × 2 stretch ratio is optimum for impact resistance. The actual property/processing condition relationships exhibit very complicated interactions and are correlated empirically in this study. The dynamic measurements suggest that overall local segmental beta motion is increased after orientation but that the relative chain alignment makes it more difficult to activate this motion.
The quantitative differential thermal analysis determination of polyolefin stabilization
Authors: Wight F. R. 
Published: December 2004

AbstractQuantitative Differential, Thermal Analysis has been used in the wire and cable industry for determining the degree of oxidative stability of polyolefins for quality control purposes in lieu of a direct antioxidant analysis, However, it has never been shown whether the presence of each additive in a stabilizer package could be detected by this method. The results presented here indicate that the presence of a primary antioxidant and a copper inhibitor in combination can be detected separately by comparing the oxidative induction times in copper and aluminum pans. The addition of a thioester synergist such as distearyl thiodipropionate, DSTDP, is evidenced by an increased induction time in aluminum pans. However, the presence of DSTDP makes it impossible by this method to determine whether an effective level of copper inhibitor is present since the sample shows a reduced stability on copper compared to aluminum. One of two factors can be invoked to explain these results: a) DSTDP interferes with the complexing ability of the copper inhibitor or b) the copper‐inhibitor complex retards the synergistic effect of the DSTDP. In either case, this factor is not important at lower temperatures since oxygen uptake data at 130°C indicate that DSTDP is an effective synergist in the presence of copper.
Open cell poly(vinyl chloride) foams by mechanical frothing of plastisols
Authors: Deanin Rudolph D. , Calcuttawala Aziz H. , Kapasi Vikram C. 
Published: December 2004

AbstractPVC plastisols were formulated with silicone surfactant, mechanically shipped to form froths, and oven‐fused to form open‐cell foams. These were much softer than conventional chemically‐blown foams which contain mixtures of open and closed cells. Increasing plasticizer content and decreasing foam density also had the expected softening effects on foam properties.
Azidosilane polymer—filler coupling agent
Authors: McFarren Gerald A. , Sanderson Thomas F. , Schappell Frederick G. 
Published: December 2004

AbstractThis new coupling agent shows promise for use in reinforcing hydrocarbon type polymers, such as polyolefins and polystyrene, with glass fibers and inexpensive mineral fillers. Sulfonyl azide derivatives readily form durable bonds to many thermoplastics at normal extrusion and molding temperatures, without the use of peroxide or sulfur‐type curing agents. Alkoxy silanes, attached to the sulfonyl azide, hydrolyze in the known manner forming bonds to inorganic fillers. Using commercial compounding and injection molding procedures, 40 wt percent of mineral fillers containing 1 percentofan azidosilane coupling agent were incorporated in polypropylene. Very substantial improvements in tensile, flexural and heat distortion properties were obtained with little loss in impact strength. An initial evaluation in a filled polystyrene showed significant, but less dramatic, improvements.