bluuebunny/crossref_metadata_2025_split huggingface dataset:
The plasticization of an epoxy resin by dibutylphthalate and water
Authors: Thomson K. W. , Wong T. , Broutman L. J. 
Published: May 2005

AbstractThe glass‐transition temperature of an epoxy resin cured at two different temperatures and plasticized with water and dibutylphthalate has been studied. Both modulus of elasticity and yield stress were measured as a function of temperature to determine the glass‐transition temperature. Drying a saturated material appeared to restore the glass‐transition temperature to its original value but some broadening of the transition occurred. The behavior of an undercured epoxy when saturated with water could not be predicted by theory. A substantial increase in the transition temperature was observed which may have been caused by the presence of water and an expanded structure.
Theoretical and experimental study of the molten polymer flow in the calender bank
Authors: Agassant J. F. , Espy M. 
Published: May 2005

AbstractThe flow of molten polymers in the calender bank has been computed using a finite‐element method with stream function and vorticity. Two nonsymmetrical‐recirculating regions have been obtained fully in agreement with the experimental observations on poly(vinyl chloride) melt banks. The pressure distribution along the flow axis is very close to the one obtained using the classical‐lubrication approximation.
Dynamic mechanical properties of some polyurethane‐acrylic copolymer interpenetrating polymer networks
Authors: Fox R. B. , Bitner J. L. , Hinkley J. A. , Carter W. 
Published: May 2005

AbstractDynamic mechanical properties have been investigated for interpenetrating‐network systems based on polyol‐cured polyurethanes (PU) and 2 to 1 n‐butyl acrylate‐n‐butyl methacrylate (Ac) networks. The systems were formed simultaneously (SIN) from all of the precursors and reactants for both networks in the same vessel, and sequentially (SIPN) by swelling a precured PU with the reactants that will form the Ac network. If the Ac network is formed after gelation of the PU, the IPNs are transparent and appear to have single T (tan δmax) between those of the homonetworks; visible‐phase separation occurs if the Ac is intentionally polymerized prior to PU gelation. Damping curves were lower and broader and the T (tan δmax) and rubber moduli were higher for the SIN than for the SIPN systems. Up to 65 percent Ac, the T (tan δmax) data for both SIN and SIPN fit the Gordon‐Taylor equation if a T (tan δmax) for the Ac homonetwork 7°C higher than observed is used, suggesting a higher crosslink density for the Ac network under these conditions. The differences in properties of the SIN and SIPN are assumed to be dependent on sample homogeneity and upon the presence of a tin catalyst in the SIN preparation. This can result in limited Ac‐network formation and consequent phase separation before PU gelation has occurred, and the catalyst may also increase the extent of interaction, such as grafting or hydrogen‐bond formation between the networks.
Free‐radical polymerization of methyl methacrylate in tubular reactors
Authors: Baillagou Pierre E. , Soong David S. 
Published: May 2005

AbstractMathematical modeling and experimental studies of the freeradical polymerization of methylmethacrylate in tubular reactors have been performed to ascertain the operating constraints, reactor behavior, and product quality of this process. This paper focuses on reactions at a temperature below the glass transition of poly(methyl methacrylate). This class of experiments is here referred to as low‐temperature runs, in contrast to above‐Tg polymerization. Reactor temperature and conversion histories of these low‐temperature experiments are successfully described by a rheokinetic model, incorporating both detailed considerations of velocity profile development in the reactor and conversion‐dependent kinetics. The limitations of this process are discussed in light of the complex fluid flow and heat transfer problems encountered in the system.
Rheokinetics for reactive polymer processing
Authors: Biesenberger J. A. , Kumar R. , Garritano R. , Starita J. M. 
Published: May 2005

AbstractAn important aspect of all reactive polymer processing methods, including reactive injection molding (RIM) and reactive extrusion (REX) is the dramatic increase in viscosity of the material being processed. This paper describes an instrument designed to study rheokinetics of polymerizations relevant to reactive processing. The instrument is capable of measuring simultaneously both viscosity (dynamic or “steady”) and reaction rate during isothermal polymerizations in a closed system. Design aspects of the instrument and some preliminary results are presented.
Nucleation of crystallization of polyester by catalyst remnants—a review
Authors: Lawton E. L. 
Published: May 2005

AbstractThe antimony catalyst content of poly(ethylene terephthalate) has an appreciable effect on the tendency of the polymer to crystallize upon cooling from the melt. Nucleation density increases significantly as antimony catalyst concentration increases. The crystallization tendency of the polymer at a given molecular weight correlates strongly with both the antimony content and the diethylene glycol comonomer content. The behavioral patterns of nucleation by catalyst remnants are similar in polyester prepared from terephthalic acid or dimethyl terephthalate. The antimony catalyst is deposited in the polyester matrix in a form suitable to nucleate quiescent crystallization. The differences in tendency to crystallize that correlate with catalyst and diethylene glycol comonomer content are reflected in the crystallinity of injection molded samples.
Effect of flow history on the morphology of thermotropic liquid crystalline copolyesters
Authors: Joseph Eugene G. , Wilkes Garth L. , Baird Donald G. 
Published: May 2005

AbstractMorphological studies have been carried out on a thermotropic liquid crystalline copolyester based on poly(ethylene terephthalate) (PET) and para hydroxybenzoate (PHB) that has been subjected to different types of flow histories. Wide angle X‐ray scattering investigations and chemical etching (n‐propylamine is the etchant) in conjunction with electron microscopy studies conducted on end gated injection molded plaques of the 60 percent PHB and 80 percent PHB copolyesters indicate that a highly oriented skin region and a less oriented core region is present. Chemical etching studies performed on microtomed layers of end gated and center gated plaques show that the etching is less pronounced in the skin region and is more pronounced in the core. The microtomed layers of the end gated injection molded plaques when analyzed by ESCA indicate the presence of a “PHB rich” skin region and a “PET” rich core region. Biaxial orientation, as denoted by WAXS measurements, is observed when the 60 percent PHB copolyester is squeezed between lubricated parallel plates.
Phase separation effects in processing of glass‐bead‐ and glass‐fiber‐filled thermoplastics by injection molding
Authors: Hegler R. P. , Mennig G. 
Published: May 2005

AbstractDumb‐bell specimens and rectangular boxes were used to study phase separation effects occurring in injection molding of glass‐bead and glass‐fiber‐filled thermoplastics. The separation effects were more pronounced with beads than with fibers and they increase with increasing bead diameter. The filler distribution is further influenced by mold geometry, filler concentration, matrix material, and processing conditions. If the use of fillers, which promote inhomogeneity, is unavoidable it is possible to improve the distribution of the rigid phase by a favorable choice of injection speed and melt temperature. With the theories available at present a qualitative interpretation of the origin of the observed separation phenomena is feasible.
A heat storage module with a polymer structural matrix
Authors: Feldman D. , Shapiro M. M. , Fazio P. 
Published: May 2005

AbstractTest results are presented for a matrix type phase change thermal storage tile module with no surface covering, intended to transfer heat directly to and from room air at small temperature differences. Heat is stored and released by melting and freezing mixtures of fatty acids, which constitute up to half the weight of the tile. The polymeric matrices tested were powders or granules of poly(vinyl chloride) (PVC), poly (vinyl acetate) (PVAc), poly(vinyl alcohol) (PVA), vinyl acetate‐vinyl chloride copolymer (VAc‐VC), and high density polyethylene (HDPE). The tiles keep their shape and dimensions without any weeping of liquid fatty acid, up to 37 or 51°C, depending on their composition. In the case of PVC and PVA, infrared spectra and differential scanning calorimetry indicate interactions between the polymer and the fatty acids, which may increase the surface tension and allow larger matrix pores before weeping begins. Some of the tiles were reinforced with glass fibers, and others with cellulose fibers. The best mechanical properties were obtained with 5 percent of long (85 to110 mm) glass fibers. Paraffin chloride and antimony trioxide served as satisfactory fire retardants.
Flame retardation of polypropylene: Effect of silane treated antimony compounds
Authors: Jha N. K. , Misra A. C. , Tiwary N. K. , Bajaj Pushpa 
Published: May 2005

AbstractFlame retardation of polypropylene was accomplished by blending with antimony compounds (Sb2O3 and SbPO4) in conjunction with polyvinyl chloride (PVC) or ferric oxide. The compatibility and dispersion of antimony compounds in the polymer matrix was enhanced by using silane coupling agents, viz., vinyltriethoxysilane (A‐151) and γ‐aminopropyltriethoxysilane (A‐1100). Rheological properties of filled polypropylene were studied in the temperature range 180 to 220°C at shear rates of 29.5 to 119.5 sec−1. An increase in the melt viscosity was found in the filled polypropylene as compared to virgin polymer. Silanation of antimony compounds also influenced the melt rheology of flame retardant polypropylene. Incorporation of 6 phr Sb2O3 and 19 phr PVC raised the oxygen index of polypropylene to 22.9 and this sample was found to be self extinguishing in 65 s with a burning rate of 0.06 mm/s as compared to 1.1 mm/s for unfilled polypropylene. Though silanation of antimony compounds slightly reduced the oxygen index of flame retardant polypropylene, yield strain and flexural rigidity of injection molded samples was improved over unsilanated flame retardant polymer.
Moisture diffusion in epoxy resins Part I. Non‐Fickian sorption processes
Authors: Wong T. C. , Broutman L. J. 
Published: May 2005

AbstractDiffusion of water in a glassy epoxy resin has been studied by the sorption method. Film thickness scaling is used as a diagnostic tool for non‐Fickian sorption processes. A sorptiondesorption cycle effectively increases the preexisting free volume in the resin and renders the subsequent sorption process different from the original. The effect is understood by considering the time scale for diffusion and that for molecular relaxation of the glassy polymer network. A non‐Fickian sorption process is observed for an insufficiently cured resin and is caused by the resin undergoing further postcuring in the sorption process. It is shown that oxidation of the resin during sorption also gives rise to non‐Fickian processes previously described in the literature as diffusion anomalies for epoxies. It is further shown that the difference between sorption and resorption curves is not caused by irreversible damage to the resin but due to reversible changes in network conformations.
Transition mechanism from elastic deformation to plastic flow in poly(methyl methacrylate)
Authors: Nanzai Yukuo 
Published: May 2005

AbstractSudden changes of compressive strain‐rate on glassy poly(methyl methacrylate) lead to the conclusion that the post‐yield state under a constant stress is a state of steady flow in the polymer. Non‐linearity between the stress divided by temperature and the logarithm of strain rate for this steady plastic flow can successfully be analyzed using the Eyring equation with structural factors variable depending on stress and temperature. This analysis gives a unique functional relationship between the activation entropy and the activation enthalpy, which agrees fairly well with that for the melt derived from the WLF equation. This agreement provides a direct evidence verifying structural change of the glass into liquid‐like structure and enables us to recognize the conformational arrangement as an essential structural parameter controlling molecular mobility. Another experimental relation between the Eyring factors—the activation volume and the activation enthalpy—permits us to estimate the magnitude of an elementary volume for the molecular movement in the melt as a function of temperature. Moreover, the experimental finding of the steady flow in the glassy polymer motivated us to propose a transition mechanism from elastic deformation to plastic flow in which the internal viscosity or the activation volume is introduced as a single parameter representing the transient state of the structure.
Phenol/cresol‐formaldehyde resin characterization and contribution to product hardness
Authors: Brauman S. K. , Myers‐Acosta B. L. , Lokensgard P. C. , Steiner M. M. 
Published: May 2005

AbstractLot‐to‐lot variations in a phenol/cresol‐formaldehyde resin were fully characterized. Resin property‐product hardness relationships were examined to elucidate the cause of variable hardness in product insulators and to establish acceptance criteria for the resin. A high methylol content (ϕCH2OH), determined by quantitative carbon‐13 nuclear magnetic resonance (13C‐NMR), and a narrow molecular weight distribution (MWD), determined by size exclusion chromatography, were found necessary for resin to produce insulator meeting the minimum Shore D durometer specification of 40.
Nucleation in polymer crystallization: A physical or a chemical mechanism?
Authors: Mercier J. P. 
Published: May 2005

AbstractPrimary nucleation is in general heterogeneous in polymer crystallization. In unseeded polymers, the crystallization originates from a very small concentration (<0.1 percent) of unknown submicroscopic heterogeneous nuclei. Only in three cases have the nucleation mechanisms been identified with precision. The first example is self‐nucleation, which relates to the nucleation of a polymer melt by fragments of its own crystals previously present in the melt. Another example of heterogeneous nucleation is represented by epitaxial nucleation of polymers on inorganic and organic substrates recently established by Lotz and Wittmann. More recently, it was discovered that finely divided organic salts added to reactive polymers do not behave as inert heterogeneous substrates but rather dissolve and cut molten macromolecules producing ionic chain ends which precipitate into the melt and form organized aggregates which are the true nucleating species. It is clearly shown that mechanisms of physical and chemical origin are involved in heterogeneous primary nucleation of polymer crystallization.
Internal antiplasticization in diglycidyl ether of bisphenol A diamino diphenyl methane non‐stoichiometric epoxy networks
Authors: Bellenger V. , Dhaoui W. , Verdu J. , Boye J. , Lacabanne C. 
Published: May 2005

AbstractDGEBA‐DDM (diglycicyl ether of bisphenol‐A‐diamino diphenyl methane) networks of various epoxide/amine molar ratios ranging from 0.7 to 1.4, were studied by density, quasi static (10−4 s−1), and ultrasonic (5 106 s−1) modulus, and thermostimulated creep measurements. Any step aside stoichiometry leads to an antiplasticization, e.g. an increase of the quasi static modulus, whereas Tg decreases. The previous interpretations (based on volumetric property considerations), of this phenomenon are questionable. The only common feature of all the antiplasticized systems is an unexplained decrease of the population of macro‐molecular segments involved in beta motions.
Polypropylene/polyethylene terephthalate blends compatibilized through functionalization
Authors: Xanthos M. , Young M. W. , Biesenberger J. A. 
Published: May 2005

AbstractIn attempts to improve the compatibility of polypropylene with polyethylene terephthalate, an acrylic acid functionalized polypropylene was evaluated as the blend component in polyblends containing 40 percent by weight polyethylene terephthalate and compared with an unmodified polypropylene. The preliminary experiments in a batch laboratory mixer were followed by compounding in a co‐rotating twin‐screw extruder. Additives such as magnesium acetate and p‐toluenesulfonic acid were evaluated as catalysts for potential interchange or esterification reactions that could occur in the melt. The blends were characterized through scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry, and for mechanical properties. The results show that the functionalized polypropylene promotes a fine dispersed phase morphology, improves processability and mechanical properties, and modifies the crystallization behavior of the polyester component. These effects are attributed to enhanced phase interactions resulting in reduced interfacial tension (calculated as a 4‐fold decrease). The presence of the additives does not, in general, improve any further the blend morphology and properties, or its processability.
Molecular design of multicomponent polymer systems. XVIII: Emulsification of high‐impact polystyrene and low density polyethylene blends into high‐impact alloys
Authors: Fayt R. , Teyssié P. H. 
Published: May 2005

AbstractThe interfacial activity of a hydrogenated polybutadiene‐polystyrene tapered diblock copolymer, (HPB‐b‐PS) is investigated in blends of a low density polyethylene (LDPE) with a high impact polystyrene (HIPS) prepared in the melt state on a two‐roll mill. Optical and scanning electron microscopy examinations of smoothed or fracture surfaces and also surfaces obtained after THF‐extraction of PS phases demonstrate that the copolymer promotes the dispersion and interfacial adhesion of the components, whatever the composition and is able to create and stabilize particular dispersions of the rubber particles in these blends. Tensile and Charpy impact properties are also very significantly improved. All these features demonstrate that the ductility and toughness of PS and LDPE/PS blends can be closely controlled by adequate combinations of rubber particles and a HPB‐b‐PS copolymer.
New approaches to the processing of rutile‐filled polyolefins
Authors: Duchesne D. , Schreiber H. P. , Johnson B. V. , Blong T. J. 
Published: May 2005

AbstractThe performance of a fluorocarbon elastomer processing additive in rutile‐filled linear low density polyethylene (LLDPE) compounds was evaluated by capillary rheometry, and blown film extrusion. Different compounding sequences were considered and their effects on the performance of the processing additive in the presence of various rutiles examined. Lower apparent melt viscosities and higher shear rates for the onset of melt fracture were observed when using certain surface treated rutiles. The nature of the surface coating applied to rutiles was found to have a great influence on the Theological properties of the filled compounds and on the dispersibility of the solids. The acid‐base characteristics of rutiles were determined by inverse gas chromatography techniques, and inherent agglomeration indexes for the pigments were measured by an application of powder rheology principles. It was found that those rutiles with high agglomeration indexes or those with highly basic surfaces interfered the most with the processing additive. Mechanisms by which rutile dispersibility and acid‐base character influence the effectiveness of the fluorocarbon elastomer processing additive are discussed.
Prediction of fiber orientation in injection molded parts of short‐fiber‐reinforced thermoplastics
Authors: Matsuoka Takaaki , Takabatake Jun‐Ichi , Inoue Yoshinori , Takahashi Hideroh 
Published: May 2005

AbstractFiber orientation induced by injection mold filling of short‐fiber‐reinforced thermoplastics (FRTP) causes anisotropy in material properties and warps molded parts. Predicting fiber orientation is important for part and mold design to produce sound molded parts. A numerical scheme is presented to predict fiber orientation in three‐dimensional thin‐walled molded parts of FRTP. Folgar and Tucker's orientation equation is used to represent planar orientation behavior of rigid cylindrical fibers in concentrated suspensions. The equation is solved about a distribution function of fiber orientation by using a finite difference method with input of velocity data from a mold filling analysis. The mold filling is assumed to be nonisothermal Hele‐Shaw flow of a non‐Newtonian fluid and analyzed by using a finite element method. To define a degree of fiber orientation, an orientation parameter is calculated from the distribution function against a typical orientation angle. Computed orientation parameters were compared with measured thermal expansion coefficients for molded square plates of glass‐fiber‐reinforced polypropylene. A good correlation was found.
Solidification behavior and recovery kinetics of liquid crystalline polymers
Authors: Done D. , Baird D. G. 
Published: May 2005

AbstractThe supercooling behavior of three thermotropic liquid crystalline polymers (TLCP's), 60 mole% p‐hydroxybenzoic acid and 40 mole% poly(ethyleneterephthalate), 60/40 PHB/PET, 80 mole% p‐hydroxybenzoic acid and 20 mole% poly(ethyleneterephthalate), 80/20 PHB/PET and a copolyester of 73 mole% p‐hydroxybenzoic acid and 27 mole% of 2‐hydroxy‐6‐naphthoic acid, Vectra A900, was studied by means of both rheological and thermal methods. 60/40 PHB/PET and Vectra A900 exhibited a degree of supercooling as high as 80°C while there was only 20°C of supercooling for 80/20 PHB/PET. The degree of supercooling for the blends of 60/40 PHB/PET and 80/20 PHB/PET also decreased with the increase in 80/20 PHB/PET content. The increase in G′ as the temperature decreased was more gradual for 60/40 PHB/PET and Vectra A900 than that for 80/20 PHB/PET, which was beneficial from a processing point of view. The solidification of the LCP melt was attributed to both the crystallization and the freezing of the mesophase. The degree of crystallinity for all three TLCP's was very small, less than 5%, as measured by the DSC. It was found that both 60/40 PHB/PET and Vectra A900 showed an induction period of a few minutes during solidification while 80/20 PHB/PET solidified continuously at the test temperature. Therefore, 60/40 PHB/PET and Vectra A900 seem to be more suitable for use in processes such as blow molding and film blowing than 80/20 PHB/PET.
Injection molding of polypropylene/polycarbonate blends
Authors: Fisa B. , Favis B. D. , Bourgeois S. 
Published: May 2005

AbstractThis work deals with the effects of material and processing parameters on the mechanical behavior and morphology of noncompatlbilized polypropylene‐polycarbonate (PP‐PC) blends. The blends containing between 0 and 40 vol. percent of polycarbonate were compounded using a twin screw extruder and converted by injection molding using molds with rectangular as well as dogbone shaped cavities. The blends exhibit a complex skin‐core morphology which evolves with the composition. Despite the absence of interfacial adhesion, the low strain modulus increases with PC concentration and follows approximately the Takayanagi model for systems with perfect adhesion. A slight increase of stiffness and strength with increasing PP/PC viscosity ratio is also observed. Weldline strength of these blends is generally poor and decreases with the increasing PC concentration.