bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture toughness of a short‐fiber reinforced thermoplastic
Authors: Haskell W. E. , Petrie S. P. , Lewis R. W. 
Published: December 2004

AbstractThin plates of carbon short‐fiber reinforcement polycarbonate were injection molded. The mold was designed to produce a uniform melt flow across the cavity and an extended knock‐out pin was incorporated to form a circular hole at the center of the molded plate. The elastic constants of the plaques were determined using sections cut from the plate at different angles to the direction of flow. Analysis of the data showed that the plates could be treated macroscopically as being orthotropic. Microscopic observations revealed that the fiber orientation was primarily in the flow direction and was tangential in the vicinity surrounding the hole. The fracture toughness, as measured by the stress intensity (K), was determined using the compliance method. Experimental calibration curves were constructed at 0° and 90° to the axis of flow by loading specimens containing saw cuts of varying length. The resultant curves were non‐dimensionalized by incorporation of the elastic moduli, thickness, and width. The fracture toughness values were determined using a razor notch as a starter crack. The crack growth during testing was found to be stable, which could allow several determinations to be made on each plate. The effects of crack length, flow in the cavity, and fiber orientation around the hole were investigated. The fracture toughness was found to decrease with increasing crack length, but was not found to reach a limiting value within the practical range of testing. The effect of flow was also found to be significant. Specimens oriented 90° to the axis of flow showed higher toughness values. This was attributed to the fibers being oriented perpendicular to the axis of the crack. The samples tested with razor notches cut at the edge of the molded holes had still higher apparent toughness values. Similarly, this effect was explained by the higher fiber orientation shown with photomicrographs of specimens cut near the edge of the hole.
Phase relationships of rigid rod polymer/flexible coil polymer/solvent ternary systems
Authors: Hwang W‐F. , Wiff D. R. , Verschoore C. 
Published: December 2004

AbstractPhase diagrams of two types of rigid rod polymer/flexible coil polymer/methanesulfonic acid (MSA) ternary systems were determined by polarized optical microscopy at ambient conditions. The rigid rod polymer is a wholly aromatic high temperature resistant (no measurable Tg) poly (p‐phenylenebenzobisthiazole) (PPBT). One of the flexible coil polymers is a wholly aromatic high temperature resistant poly (2,5′(6′) benzimidazole) (ABPBI), the other is a thermoplastic poly[2,2′ ‐(1–4‐phenylene)‐6,6′ ‐bis (3‐phenyl‐quinoxaline)] (PPQ) with Tg of 359°C. The solvent is methane‐sulfonic acid (MSA). The experimentally determined critical concentration points, Ccr, are in excellent agreement with Flory's recent theory. Total phase segregation between the polymer pair in ternary solution was predicted and observed at C > Ccr. Different decomposition mechanisms of phase separation were observed as a function of concentration.
Morphology—properties relationships in binary polyamide 6/rubber blends: Influence of the addition of a functionalized rubber
Authors: Cimmino S. , D'Orazio L. , Greco R. , Maglio G. , Malinconico M. , Mancarella C. , Martuscelli E. , Palumbo R. , Ragosta G. 
Published: December 2004

AbstractThe modification of an amorphous random ethylene‐propylene rubbery copolymer (EPM) has been accomplished by solution grafting of maleic anhydride molecules promoted by radical initiators, The resulting EPM‐g‐succinic anhydride (EPM‐g‐SA) and EPM have been used to obtain binary polyamide 6/EPM or polyamide 6/EPM‐g‐SA and ternary polyamide 6/EPM/EPM‐g‐SA blends by melt mixing. The formation of an EPM‐g‐PA6 graft copolymer during the blend preparation has been assumed. Different blend morphologies were observed by scanning electron microscopy (SEM) according to the nature and content of the rubber used. The tensile mechanical properties and the impact behavior of the prepared blends were investigated and correlated with the SEM analysis of the fracture surfaces. Binary and ternary blends containing 20 percent by weight of total rubber show a significant improvement of the impact properties at low temperature (−20°C) when the rubber is partly or entirely EPM‐g‐SA. In the case of PA6/EPM‐g‐SA (80/20) blend these results are related to the presence of rubbery domains of very small size strongly adherent to the PA6 matrix. In the case of 80/10/10 ternary blends, a much more complicated overall morphology is observed. Such morphology is characterized by the presence of large EPM domains, likely containing some EPM‐g‐PA6 graft molecules acting as an interfacial agent, and domains of EPM‐g‐PA6 of smaller size strongly adherent to the matrix as in the previous case.
Rheological and mechanical behavior of the UHMWPE/MDPE mixtures
Authors: Dumoun M. M. , Utracki L. A. , Lara J. 
Published: December 2004

AbstractAn attempt was made to melt incorporate ultra high molecular weight polyethylene, UHMWPE, into medium density polyethylene, MDPE. The behavior of the mixtures, containing up to 6 wt percent of UHMWPE, was examined using mechanical and rheological testing. The mechanical test results were found to contain large experimental errors, which makes interpretation very difficult. On the other hand, melt rheology studies, using dynamic and extensional deformations, gave direct insight into the extent and effect of blending. Degradation during the processing was evaluated by size exclusion chromatography. The degree of dispersion of the UHMWPE was examined under the optical microscope.
Thermally stimulated creep of polyethylene, polypropylene, copolymers, and blends
Authors: Demont P. , Chatain D. , Lacabanne C. , Ronarc'h D. , Moura J.‐L. 
Published: December 2004

AbstractThe technique of Thermo Stimulated Creep (TSC) has been applied to the study of anelastic properties of polyethylene, polypropylene, their copolymers and blends. In the temperature range −200 to 100°C, complex TSC peaks were observed in all samples, namely around 0°C, about the same temperature as for the homopolypolymer polypropylene. By applying “fractional stresses”, with a convenient choice or the loading program, these peaks have been experimentally resolved. Two components can be distinguished: 1. The “low temperature” component is characterized by mechanical retardation times following a compensation law. It has been attributed to microbrownian motions of polypropylene sequences liberated at the glass transition of the “true” amorphous regions. 2. The “high temperature” component which is influenced by thermal treatment has been assigned to microbrownian motions of polypropylene sequences liberated at the glass transition of the “constrained” amorphous regions. In block polymers, an additional TSC peak is observed around −50°C: it has been associated with the glass transition of ethylene‐propylene‐rubber (EPR) interphase. The coupling of this interphase with polyethylene and polypropylene phases is insured by diffusion of some ethylene and propylene sequences in‐EPR. At about −140°C, a TSC peak associated with the low temperature component of the glass transition of polyethylene can be distinguished in all the materials studied.
Thermokinetics of unsaturated polyester and vinyl ester resins
Authors: Lem Kwok‐Wai , Han Chang Dae 
Published: December 2004

AbstractAn experimental study was carried out to investigate the isothermal and non‐isothermal curing kinetics of unsaturated polyester and vinyl ester resins, using differential scanning calorimetry (DSC). Emphasis was put on investigating the effect of low‐profile additives on the curing kinetics of the thermo‐setting resins. For the study, a general‐purpose polyester resin and a vinyl ester resin were used, together with polyvinyl acetate (PVAc) as low‐profile additive, benzoyl peroxide as initiator, and N,N‐dimethyl aniline as promoter. It has been found that (1) the addition of the low‐profile thermoplastic‐additive decreases the rate of cure and, also, the final degree of cure of the resins, (2) the total heat of cure generated by isothermal cure is lower than that generated by non‐isothermal cure, and (3) the resin/initiator mixture with promoter exhibits two major exotherm peaks during non‐isothermal cure, but only a single exotherm peak during isothermal cure.
Concerning voids in polyimide
Authors: Russell T. P. 
Published: December 2004

AbstractSmall angle X‐ray scattering (SAXS) has been used to evaluate the size and concentration of voids in poly(N,N′‐bis‐(phenoxyphenyl)pyromellitimide), PMDA‐ODA. Analysis of the angular dependence of the scattering indicates the presence of voids ranging from 50 to 150 Å in radius. Integrated SAXS demonstrated that the volume fraction of voids was 7 × 10−4. These results were supported by measurements of the attenuation factor as a function of the sample thickness.
A study of aromatic polyester/chlorinated polymer blends
Authors: Aubin Madeleine , Prud'Homme Robert E. 
Published: December 2004

AbstractA large number of studies have been devoted in recent years to the miscibility behavior of linear polyesters with chlorinated polymers, including poly(vinyl chloride) (PVC), chlorinated PVC, chlorinated poly(ethylenes), and copolymers of vinylidene chloride (Saran). However, similar studies with aromatic polyesters are lacking. It is the purpose of this paper to compare the properties of blends made of poly(ethylene terephthalate), poly(butylene terephthalate) or poly(hexamethylene terephthalate) and of various chlorinated polymers. It is shown that a high concentration of chlorine atoms is required to achieve miscibility. Moreover, there is a “miscibility window” in terms of the carbonyl concentration of polyesters, immiscibility being found for carbonyl concentrations outside this window, A similar behavior was observed before for linear polyester/chlorinated polymer blends and for polyester/polycarbonate blends. Solid state small‐angle light scattering experiments were also conducted to follow the morphology of the blends as a function of composition. Spherulites were found but their size vary with composition.
Small angle scattering from ampholytic styrene ionomers
Authors: Clough S. B. , Cortelek D. , Nagabhushanam T. , Salamone J. C. , Watterson A. C. 
Published: December 2004

AbstractSmall angle neutron scattering experiments were made on an ionomer synthesized from perdeuterostyrene and an ion pair comonomer. A Debye plot based on data from the sample with lower ion concentration gave a correlation length of 5.3A. Clustering is not significant in this sample. With a higher concentration of ionic groups a peak in the scattering curve is interpreted as due to clusters about 20A in diameter. These studies along with X‐ray scattering and electron microscopy also indicate the presence of larger ion rich domains.
Tensile behavior of high‐density thermosetting polyester foams
Authors: Masi P. , Nicolais L. , Mazzola M. , Narkis M. 
Published: December 2004

AbstractThis paper shows that the tensile properties of high‐density stiff foams having cellular structures consisting of spherical voids can be described and predicted by simple rules. These rules are derived from other known and experimentally established relationships describing particulate systems of continuous glassy matrices containing a uniform dispersion of solid glass beads.
General treatment of polymer crystallization kinetics—Part 2. The kinetics of nonisothermal crystallization
Authors: Malkin A. Ya. , Beghishev V. P. , Keapin I. A. , Andrianova Z. S. 
Published: December 2004

AbstractThe isothermal macrokinetic equation of polymer crystallization has been generalized to cover nonisothermal situations as well. The process of nonisothermal crystallization of poly(caproamide) has been studied experimentally. It is shown that the macrokinetic equation of the autocatalytic type can be used to solve both direct and inverse problems of nonisothermal polymer crystallization. Use of the inverse approach has made it possible to establish the value of the constants of the new kinetic equation. The general statement of the problem of nonisothermal crystallization of polymers in an inhomogeneous temperature field is considered. Inhomogeneous temperature and conversion fields have been calculated for model products of different sizes and configurations.
Elastomeric properties of bimodal networks prepared by simultaneous curing‐filling technique
Authors: Tang M.‐Y. , Mark J. E. 
Published: December 2004

AbstractIf the tetraethylorthosilicate (TEOS) used to end link hydroxyl‐terminated poly(dimethylsiloxane) chains is present in excess, there are two effects on the resulting network structure. First, some of the excess TEOS hydrolyzes to give in situ precipitation of reinforcing silica particles. In addition, some can cause extension of the polymer chains, particularly of the shorter chains in the case of a bimodal network. In the present investigation, the ultimate strength and toughness of such bimodal networks was found to go through a maximum with increase in the amount of excess TEOS used in the curingfilling procedure.
History and development of engineering resins
Authors: Woodhams Raymond T. 
Published: December 2004

AbstractA brief perspective of the history and development of the plastics industry is outlined with special reference to engineering plastics and high performance resins. Since the birth of the synthetic plastics industry just over half a century ago, a myriad of polymeric structures have been created of which only a few generic types have attained commercial status. These basic resin types are combined in many ways as composites or blends to make available to industry over 6000 grades for use in fibers, films, coatings, adhesives, or molded shapes. Although plastics are characterized by their mechanical, electrical, chemical, or physical properties, it is their selling price that tends to dominate the volume production of each resin. Today, the modern plastics engineer employs remote‐access interactive computer databanks to conduct design and feasibility studies employing the full inventory of resin grades in his assessment. A final section reveals current attempts by researchers to impart extraordinary strength and modulus to conventional plastics by means of solid phase processing, whereby polymeric chains are uncoiled and aligned to produce remarkably tough materials which are likely to challenge the supremacy of steel.
Kinetics of acetylene polymerization and structures of polyacetylene
Authors: Chien James C. W. 
Published: December 2004

AbstractThe kinetics of acetylene polymerization have been studied as a function of monomer pressure, catalyst aging and concentration, Al/Ti ratio, and temperature. The rate constants of chain propagation and termination and their activation energies have been determined, The Mn of polyacetylene has been obtained using a radioquenching technique, and was found to vary from 500 to 250,000. Wide angle X‐ray diffraction showed the polymer to be highly crystalline but the crystallites are disordered. The crystal structures of cis and trans polyacetylene have been obtained from the fiber electron diffraction patterns. The c‐axis is the polymer chain axis which is along the fiber axis. The basic morphological entity is the microfibrils of 2 to 3 nm diameter which aggregate to form 20 to 30 nm fibrils.
The development of molecular orientation and morphological texture in thermotropic copolyesters
Authors: Viola G. G. , Baird D. G. , Wilkes G. L. 
Published: December 2004

AbstractLiquid crystalline polymers can be processed to form high strength/modulus materials. In processing these materials, it is apparent that molecular orientation is an important factor in determining the physical strength of the processed materials. In this study a systematic investigation was carried out to determine how a thermotropic copolyester of parahydroxybenzoic acid (PHB) and polyethylene terephthalate (PET) responds to two basic types of flows: shear and extensional flow. This was accomplished by preparing sheared and extended samples under controlled conditions of temperature and flow history. Sheared disks were prepared using a disk and plate geometry of a Rheometrics Mechanical Spectrometer (RMS model 605), while extended ribbons were prepared using a slit die attached to an Instron capillary rheometer. Two copolymerer compositions of 60 mole percent and 80 mol percent PHB were investigated. The sheared disks and extended ribbons were investigated for molecular orientation and morphological textures using wide angle x‐ray scattering (WAXS) and scanning electron microscopy (SEM) analysis, respectively. It was found that extensional flow has a greater capacity for orienting such materials than shear flow. Samples annealed at their softening points for 1 minute (240°C for the 60 mole percent PHB/PET copolymer and 300°C for the 80 mole percent PHB/PET copolymer) showed no significant loss of orientation, indicating that once orientation is produced it may remain in the melt for a long period of time. Sheared samples prepared by shearing the sample while cooling showed significantly higher degrees of orientation than those not cooled while being sheared. This may indicate that a minimum stress level exists for the production of orientation in shear flow.
An empirical correlation for polymer self‐diffusion data in the dilute and semidilute concentration regimes
Authors: Hanley Brian , Tirrell Matthew 
Published: December 2004

AbstractAn expression is presented which can be used to correlate and predict, in an empirical fashion, polymer self‐diffusion coefficients in solution over a wide range of concentrations and molecular weights, and whose parameters can be established with a minimal amount of data. Predictions thus made have been found to agree well with the limited amount of available experimental data over the entire concentration‐molecular weight spectrum studied to date. This is in marked contrast to other available expressions, whose validity is confined to a narrow range of concentrations and/or molecular weights.
Reaction kinetics of polyurethane‐polyester interpenetrating polymer network in the bulk polymerization
Authors: Hsu T. Jeffrey , Lee L. James 
Published: December 2004

AbstractKinetics of simultaneous interpenetrating networks (SIN) composed of a polyurethane resin (PU) and an unsaturated polyester resin was studied. A differential scanning calorimeter (DSC) was used to monitor the polymerization course. It was found that increasing the polyester content in a PU‐polyester SIN enhanced the polymerization of PU due to the “solvent effect” of polyester. On the other hand, increasing the PU content in the SIN retarded the polymerization of polyester due to the “cage effect” of PU. Polymerization sequence of the SIN could be controlled by employing different initiators for polyester reaction. The degree of crosslinking in each SIN component had a significant effect on the dynamics of the SIN formation and on the limiting conversion of the polyester reartion.
Shear and extensional flow of reinforced plastics in injection molding. II. Effects of die angle and bore diameter on entry pressure with bulk molding compound
Authors: Gibson A. G. , Williamson G. A. 
Published: December 2004

AbstractOrifice flow measurements have been performed at high strain rates on bulk molding compound (BMC) using convergent dies. A range of die angles and bore diameters was examined. Two models for flow behavior have been compared. It appears that, with BMC, there is a transition from constrained convergence to convergence with recirculation at a die semiangle of approximately 56 degrees.
Phase diagrams as a formulation guide in aqueous polymer/surfactant systems
Authors: Lochhead R. Y. , Warfield D. S. , Gasiewski C. 
Published: December 2004

AbstractPolymers are often formulated into detergent products in order to confer properties which facilitate processing and/or storage of the product, or to yield desirable attributes for the end‐user. Carbopol resin which consists essentially of polyacrylic acid, is one such polymer. Carbopol resin systems exhibit Bingham‐Body‐type rheology with measurable yield‐value and pronounced shear‐thinning at shear stresses above the yield value. These properties render Carbopol resins useful as a thickener and a suspending agent. Interaction with other components in a formulation, however, can radically alter the thickening and suspending properties of Carbopol resins. Phase diagrams of Carbopol resins with other major components of the system can guide the formulator away from areas where undesirable interactions, such as coacervate formation, can occur, and when presented in the form of contour diagrams they quantitatively map the physical properties of interest, enabling the formulator to be guided directly into the composition region which will best satisfy his requirements. The phase diagrams can also predict when different desirable properties cannot be simultaneously achieved and they can define the extent of compromise which may be necessary in formulation of the final product.
Equations of state of polymer
Authors: Cho Bongkee 
Published: December 2004

AbstractEquations of state for polymers above and below the glass transition temperature are derived. Comparisons of the predicted P‐V‐T relations with the experiment are quite favorable. From the obtained equations, both the Anderson‐Grüneisen constant and the Grüneisen constant can be determined, and the Tait equation is derived.
A kinetic study of the activated anionic polymerization of ε‐caprolactam
Authors: Lin D. J. , Ottino J. M. , Thomas E. L. 
Published: December 2004

AbstractThe diversities existing among published kinetic studies on activated anionic polymerization of ε‐caprolactam are closely examined. A kinetic model derived from a regular, linear reversible reaction mechanism is employed to explain the experimentally observed autocatalytic character of the polymerization system and to examine the dependence of the apparent activation energy on the experimental method. Several existing kinetic models tested with our experimental data show that the autocatalytic type rate equation best describes the polymerization process.
Three‐dimensional solidification and flow of polymers in curved square ducts
Authors: Ahmadian M. T. , Burmeister L. C. , Johnson R. W. 
Published: December 2004

AbstractSteady three‐dimensional laminar flow with and without partial solidification of an initially molten polymer in square ducts, both straight and with a 90‐degree curve, was numerically studied with a version of the SIMPLE algorithm. The non‐Newtonian characteristics of the fluid polymer were represented by a power‐law model. The temperature variation of fluid properties was taken into account. Viscous dissipation, being significant for all flow regimes studied, provided thermal energy input which was balanced by heat transfer outward across duct boundaries. For the non‐Newtonian fluid with solidification and variable viscosity, it was found that the effective heat transfer coefficient in the curved section of the square duct is larger than in a straight section; in the curved section, this coefficient is larger at the outside of the bend than at the inside. These findings are in agreement with measurements reported in the literature for similar situations. The combined mechanisms of solidification on the wall and viscous dissipation result in the possibility of two different flow rates for a specified pressure gradient. The flow channel that remains unfrozen in a curved square duct meanders within the confines of the duct much as a river meanders in its valley; the wave length of the meander is sensitive to the fluid flow rate and radius of curvature.