bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of polynorbornene and ethylene‐propylene terpolymer blends
Authors: Wang C. S. 
Published: December 2004

AbstractIn this study characteristics of polynorbornene (PNR) and ethylene‐propylene terpolymer (EPDM) blends were examined in terms of compatibility, cocuring, and ozone resistance. For most of the blend compositions, two glass transition temperatures (Tg) at about −30 and −50°C were observed from differential scanning calorimetry data for both uncured and cured samples. The transitions correspond to the Tg's of the component polymers, suggesting that the blends are microheterogeneous. The two‐phase blends are difficult to cocure as evidenced by the fact that tensile strengths of the blends, when plotted as a function of blend composition, deviate from the linear or additive behavior. Improved cocuring of the blends, however, can be achieved by matching the cure rates of the components. The ozone resistance of the blends containing 25 percent or more EPDM was substantially improved as compared with that of PNR. Therefore, the newly developed PNR can be used for applications requiring ozone resistance by properly blending it with EPDM.
The dual‐mode solution and transport of water in poly(acrylonitrile)
Authors: Mauze G. R. , Stern S. A. 
Published: December 2004

AbstractSolubility (sorption) and transport measurements with water in solvent‐free poly (acrylonitrile)(PAN) (23) have been interpreted in terms of an extension of the “dual‐sorption” model for transport of small molecules in glassy polymers. Satisfactory agreement has been obtained between theory and experimental data. An earlier analysis of similar data for water in PAN containing 0.26 percent (by weight) of a residual solvent (1) has been compared with the present results in order to investigate the effects of residual solvent on the dual‐sorption and transport parameters for the water‐PAN system.
Elongation rheology of polyolefins and its relation to processability
Authors: Sebastian Donald H. , Dearborn John R. 
Published: December 2004

AbstractThe rheology of a variety of polyolefin resins, and resin blends, has been examined under conditions of constant strain rate elongation. These include high, low, and linear low density polyethylene, as well as polypropylene, commercially modified polypropylene, and elastomer blends with polypropylene. Two distinctly different classes of behavior are apparent in the viscosity growth patterns during uniaxial extension. Some resins display unbounded stress growth even at low strain rates. Others quickly attain a time independent value of extensional viscosity even at increased strain rates. The former behavior is identified with favorable blow molding behavior, while the latter was characteristic of resins unsuitable for such processing. The class of elongation behavior depends not only on resin type, but may be influenced by molecular weight distribution or blend morphology.
The influence of knit‐lines on the tensile properties of injection molded parts
Authors: Criens R. M. , Moslé H. G. 
Published: December 2004

AbstractWhen injection molding complex parts, often knit‐lines are formed during the mold filling stage. These knit‐lines are well‐known as particularly critical regions in the mold when mechanically loaded. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter and the effects of the knit‐lines on the tensile properties of injection molded plates with holes is quantified by the variation of a socalled knit‐line‐factor ak1. Finally, for PS a comparison of the influence of knit‐line‐formation by a splitted melt stream and by multi‐gating on the mechanical level is given.
Compounding extruders for improved polyblends
Authors: Eise Kurt , Curry John , Nangeroni James F. 
Published: December 2004

AbstractAn expanding application for compounding extruders is the production of materials with new and outstanding properties by blending two or more polymer components. Mixing is essential to control domain size and insure nongradient properties whether the components are miscible, multiphase with discreet domains, or multiphase with stratified structure. This paper will comment on important mechanisms for dispersion in single‐screw and twin‐screw compounding extruders. A theoretical model for mixing via kneading blocks in twin‐screw corotating extruders is experimentally verified. The pigment distribution was found experimentally to agree generally with theory. The commercially interesting polyblend systems and compounder geometries are more complicated than the theoretical model. Practical compounder design considerations for miscible, rubber‐toughened and two‐phase stratified systems are presented.
A novel technique for measuring the impact properties of a tough polyethylene
Authors: Truss R. W. , Duckett R. A. , Ward I. M. 
Published: December 2004

AbstractA novel technique is described which enables reliable fracture toughness measurements to be made in impact test on relatively small specimens of a tough polyethylene. Composite specimens have been made in which a tough polyethylene is sandwiched between two layers of a more brittle polyethylene. The overall fracture toughness is interpreted on the basis of simple additivity of the strain energy release rate associated with each of the component layers. Brittle plane strain failures were obtained for specimens in which the relative thickness of the layers was varied over a substantial range and the fracture toughness of each layer determined by suitable extrapolation. The fracture toughness of the brittle layer obtained in this way agreed well with direct measurements on that material.
Blending of polystyrene with styrene‐siloxane block and graft copolymers
Authors: Bajaj P. , Gupta D. C. , Varshney S. K. 
Published: December 2004

AbstractA preliminary study on the efficiency of styrene‐siloxane block and graft copolymer as toughening additives for polystyrene has been made. Block and graft copolymers of required molecular weight were synthesized for making compatible blends with polystyrene. Compatibility of these systems was evaluated through differential scanning calorimetry, thermo‐mechanical analysis, rheovibron studies, and scanning electron microscopy. A good miscibility of block and graft copolymers was confirmed by these methods. Higher work of rupture in these blended polystyrene samples further demonstrates the feasibility of styrene‐siloxane block and graft copolymers as good toughening material for a brittle polystyrene matrix. The mechanical properties have been related to the morphology and the amount of siloxane content in the blended polystyrene.
Improved bending fatigue life of Kevlar 29 braid by the use of an impregnating medium
Authors: D'Almeida J. R. Moraes , Hearn D. , Bunsell A. R. 
Published: December 2004

AbstractKevlar 29 fiber has been widely considered for the manufacture of very‐long high‐performance cables. Due to low transverse strength fiber‐on‐fiber rubbing leads to rapid deterioration. The usefulness of impregnating Kevlar 29 braids with resin to overcome this drawback has been evaluated by performing reverse bending fatigue tests. Braids of identical construction, one of them being impregnated with a polyurethane resin by a patented process, were fatigued to failure on a purpose‐built rig under varying applied loads. Fatigue tests were also carried out to 30 percent and 50 percent of total braid life and residual strength values measured. It was found that high applied loads (∼50 percent of ultimate) lead to premature braid failure dominated by a creep mechanism. Both braids showed similar behavior, although the impregnated braid was superior. At low applied loads, however, where the failure mechanisms was dominated by wear or internal abrasion, it was seen that resin impregnation could increase braid life by a factor of four. Resin impregnation coupled with bending fatigue significantly stiffens braids, as was demonstrated by tensile testing up to braid failure.
On the nature of polymer interfacesd and interphases
Authors: Sanchez Isaac C. 
Published: December 2004

AbstractAn abbreviated review of the current state of knowledge of polymer interfacial phenomena is given. Classical thermodynamics treats the interfacial zone (the interphase) as a “black box” and yields rigorous relationships among interfacial quantities. A recent reformulation of interphase thermodynamics, which eliminates the use of a Gibbs dividing surface, is shown to be an invaluable tool for investigating interfacial properties. Microscopic theories, such as the gradient theory, yield more details about what is in the black box, but the information is only approximate. The gradient theory has been used to: (1) relate the surface tension of a polymer liquid to its isothermal compressibility, (2) develop a quantitative theory of polymer liquid surface tension, and (3) determine the interfacial tension between two immiscible polymer liquids. The gradient theory will be shown to be in harmony with the microscopic theory of Helfand and co‐workers although the latter treats polymer interfaces from a completely different point of view.
Use of the lower critical solution temperature for the characterization of polymer mixtures and the study of their compatibility: Application to polyethylenes, polypropylene, and their copolymers
Authors: Varennes Suzanne , Charlet Gérard , Delmas Geneviève 
Published: December 2004

AbstractThe Lower Critical Solution Temperature (LCST) of polyethylene (PE), polypropylene (PP), and ethylene‐propylene block and random copolymers have been measured in heptanes. A thermogram related to the variation of the turbidity of the solution is obtained between 100 and 210°C. The temperature of the onset of the turbidity peak is defined as the LCST of the system. The width and the area of the turbidity peaks are tentatively associated with the polymer polydispersity and the amount of polymer involved in the phase separation. The thermograms of solutions containing both homopolymers show two distinct turbidity peaks situated at a 70°C interval. Correlations of molecular orientations in the concentrated phase, possible in PE systems but not in PP solutions, are at the origin of the lower LCST values for PE solutions. The LCST of copolymers are situated between those of the homopolymers but the dependence of the LCST on the copolymer ethylene content is different for block and random copolymers. Examples of thermograms are also given for mixtures of copolymers with PE and PP. By analysis of their thermograms, some commercial block EP copolymers were also found to contain PK and PP. This method seems well suited for characterizing polymer mixtures.
Hot water aging of polycarbonate
Authors: Narkis M. , Nicolais L. , Apicella A. , Bell J. P. 
Published: December 2004

AbstractInternal cracking and microvoids are shown to form during room temperature storage of polycarbonate samples that have previously been exposed to boiling water. These microcracks or microvoids are actually disc‐shaped pockets filled with water. This formation occurs due to the creation of water super‐saturation conditions by cooling water‐saturated specimens from 100°C to room temperature. As a result, water phase‐separation, clustering, and microvoiding result and lead to deterioration of the mechanical properties. Visual healing of the microcracks is also sometimes observed at room temperature, especially under a dry atmosphere. Water from the water‐filled pockets diffuses through the polycarbonate matrix to the external dry environment; the very thin emptied pockets then close and visually heal. This paper provides experimental data for the microvoiding process and clarifies the special mechanism of cracking/healing in polycarbonate samples.
Photodegradation of some poly(vinyl chloride) (PVC) blends: PVC/ethylene‐vinyl acetate (EVA) copolymers and PVC/butadiene‐acrylonitrile (NBR) copolymers
Authors: Skowronski T. , Rabek J. F. , Rånby B. 
Published: December 2004

AbstractPoly(vinyl chloride) (PVC) and its blends with polybutadiene‐acrylonitrile (NBR) (containing 21.7 weight‐percent acrylonitrile (AN), a heterogeneous two‐phase system; and containing 41.6 weight‐percent of AN, a homogeneous one‐phase system) and with polyethylene‐vinyl acetate (EVA) (containing 45 weight‐percent of vinyl acetate (VA), a heterogenous two‐phase system; and containing 65 weight‐percent VA, a homogeneous one‐phase system) were UV‐irradiated (at 3500 Å UV‐light (solar spectrum)). After UV irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVC/EVA. The phase structure plays an evident role on the UV degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni‐chelates photostabilizers.
Effect of prestrain on the subsequent thermal crystallization of a copolyester of lactic and glycolic acid
Authors: Mohajer Yousef , Wilkes Garth L. , Orler Bruce 
Published: December 2004

AbstractAn investigation was carried out in order to study the effect of prestrain on the subsequent crystallization of a specific copolyester based on lactic and glycolic acid. This polymer, which can be easily quenched into an amorphous glass, has a Tg of 43°C and when in crystalline form has a melting point of 210°C. Using amorphous films, samples were prestrained to various levels at temperatures not far above Tg. In some cases films were immediately quenched at the prestrain level so as to retain the elongation while others were allowed to immediately retract whereby they showed a relatively small degree of permanent Set. Utilizing birefringence, quenched samples whose initial elongation was maintained showed linear behavior with prestrain while those that retracted showed essentially zero birefringence until a prestrain of about 150 percent after which a small degree of positive birefringence resulted. Wide angle x‐ray diffraction (WAXS) showed no signs of crystallinity in all cases. These same films were then quickly taken to 150°C and rapidly crystallized. Again, one series of the prestrained samples were in the elongated state during crystallization whereas the second series was unrestrained during crystallization. Using microscopy and small angle light scattering (SALS), the morphological textures of these crystallized films were investigated. In all cases, spherulitic textures were observed of equivalent size up to a value of about 200 percent elongation the spherulite size systematically decreased with the prestrain an increase in clearly showing that prestrain had a pronounced effect upon the nucleation density. Increasing draw rate displayed a similar effect on nucleation density. Since spherulite size was noted to be the same in either series, it indicated that nucleation was induced as a result of the prestrain and remained irrelevant of whether the sample was allowed to relax or not. The morphology above the transitional state was similar to row structure common to polymers crystallized in the oriented state. WAXS and birefringence was applied to the crystallized materials and it was found that up until the transitional zone, no crystal orientation was observed in either series indicating that although nucleation density was strongly affected up until that point, no orientation was retained within the sample upon crystallization. A simplified model is used to explain the observed results.
Morphology of polyethylene‐polypropylene blends
Authors: Noel Oscar F. , Carley James F. 
Published: December 2004

AbstractThe morphology of blends of high‐density polyethylene (PE) and isotactic polypropylene (PP) was studied by mesans of optical and scanning‐electron microscopy. In the range of 10 to 90 percent by weight PE, these blends are two‐phase systems, the components of which crystallize separately into discrete phases. The presence of PE has a definite and pronounced effect on the crystalline structure of the PP, whose spherulitic structure becomes increasingly irregular and coarse with increasing PE content. The light transmission of these blends during melting and crystallization was also studied in an attempt to characterize them.
Isothermal swell of extrudate from annular dies; effects of die geometry, flow rate, and resin characteristics
Authors: Orbey N. , Dealy J. M. 
Published: December 2004

AbstractAn experimental study was made of the effects of die geometry and extrusion velocity on parison swell for three high‐density‐polyethylene blowmolding resins. Four annular dies were used: a straight, a diverging, and two converging dies. Diameter and thickness swells were measured as functions of time under isothermal conditions and in the absence of drawdown. This was accomplished by extruding into an oil having the same density and temperature as the extrudate. It was observed that 60 to 80 percent of the swell occurs in the first few seconds and that equilibrium swell is attained only after 5 to 8 minutes have elapsed. The diameter and thickness swells appear to be independent phenomena, as the relationship between them depends strongly on die design. The ranking of the resins in terms of the magnitude of the swell was found to be the same for all die geometries and extrusion rates used.
Inter‐ and intrachain elastic interactions in polymers and polymer blends
Authors: Lin Kenneth S. C. , Aklonis J. J. 
Published: December 2004

AbstractThe damped Debye lattice or damped torsional oscillator model for viscoelastic relaxation in the primary transition region takes into account elastic interchain interactions as well as the more usually invoked intrachain interactions. To test the importance of these interchain interactions, we have applied this model to compatible blends formed from atactic polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). Qualitative predictions of the variation of stress relaxation behavior of the blends as a function of PPO concentration have been made. Also, predictions concerning properties of these blends upon dilution suggest very distinctive behaviors. We have measured stress relaxation master curves in the primary transition region of PS‐PPO blends of various concentrations and have found that the predicted behavior is indeed observed. Furthermore, the unusual effects of dilution on the properties of these blends have been observed with dioctyl phthalate used as diluent. These results show that inter‐ as well as the more familiar intramolecular elastic interactions are important factors in determining viscoelastic behavior of bulk polymers in this transition region.
Liquid‐liquid equilibria in polymer blends–molecular weight effects
Authors: Somani R. H. , Shaw M. T. 
Published: December 2004

AbstractFlory's equation‐of‐state theory has been successfully used by several scientists to predict the qualitative nature of the liquid‐liquid phase equilibria in polymer blends. This theory in its most simple form requires characteristic PVT parameters for each component plus an interaction energy parameter for the mixture. The melt titration technique was used to measure the miscibility of a series of polystyrene fractions (Mw = 4000 to 1,800,000) in low density polyethylene. Because the PVT properties of both of these polymers are well known, the experimental results could be compared with the predicted equilibrium compositions from Flory's equation‐of‐state theory using the interaction energy as an adjustable parameter. This comparison led to the conclusion that the interaction energy parameter may have some molecular weight dependence.
Poly(butyleneterephthalate)‐poly(ethylene‐co‐vinylacetate) polymer blends. Part II
Authors: Pilati Francesco , Pezzin Giovanni 
Published: December 2004

AbstractThe more distinctive morphological features which appear in the micrographs of fracture surfaces of polymer blends of poly(butyleneterephthalate)(PBTP) with poly(ethylene‐covinylacetate) (EVA), obtained by polymerizing in different conditions dimethylterephthalate (DMT) and 1,4‐butanediol (4G) in the presence of EVA (with 4 percent w/w of vinylacetate, VA,), are shown and discussed. The micrograph investigation clearly points out that the adhesion between EVA particles and PBTP matrix increases with the extent of reaction between PBTP and EVA and, for the same time of reaction, by changing from an anchor to a paddle agitator. The mean diameter of the particles is also affected by time of reaction and by the geometry of the agitator, decreasing when the adhesion increases.
Computerization of wire insulating lines–An industrial approach
Authors: LeNir V. L. 
Published: December 2004

AbstractThe two main materials used for insulating wire are plastic and pulp. With the introduction of digital transmission techniques, there has been an increasing demand for improved cable quality, thereby stimulating an investigation of the insulating process in order to improve quality. The increasing availability of digital computers enabled mathematical models of the insulating process to be constructed, which together with experimental work, provided a basis for the installation of computerized control systems. This paper reviews three such models which were developed and are being used. These comprise a model for screw extrusion, a model for melt flow in the wire coating die, and a model for the subsequent cooling of the insulated wire (or cable). Relatively little work was done in the area of dynamic simulation of the insulating process and we found computer control systems could be relatively easily installed in production provided high level software process modules with interfaces to a high level programming language were available on the system. It was found that simplified control schemes were usually the most effective in production. Two computer control installations to illustrate this viewpoint are described—a multiline central computerized control system, and a single‐line microprocessor‐based system.
A study in injection molding dynamics
Authors: Kamal M. R. , Patterson W. Ian , Fara D. Abu , Haber A. 
Published: December 2004

AbstractSome aspects of injection‐molding dynamics were studied using a laboratory injection‐molding machine operated under the control of a microprocessor‐based servocontrol system. Two types of experiments were performed: deterministic tests which introduced step changes in the servovalve opening and stochastic tests using pseudo‐random binary sequence (PRBS) perturbations of the servovalve. Deterministic models were written for the hydraulic and nozzle pressures which were in good agreement with the experimental data. A stochastic transfer function‐noise model was obtained for the nozzle pressure, but an adequate model was not found for the hydraulic pressure. The agreement between the nozzle pressure stochastic model and the corresponding step test model was satisfactory.