bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on soapless emulsion copolymerization methyl methacrylate and n‐butyl acrylate
Authors: Pan Ting‐Chung , Kuo Jen‐Feng , Chen Chuh‐Yung 
Published: May 2005

AbstractThe soapless emulsion copolymerization of methyl methacrylate (MMA) and n‐butyl acrylate (n‐BuA) at four levels of monomer feed composition (f10) was studied. Conversion (X), average particle diameter (Dp), molecular weight distribution (MWD), surface charge density, and glass transition temperature (Tg) of the copolymer as a function of reaction time (t) were measured. The copolymers obtained even at low conversion, except for the run of (f10) = 90 wt. percent MMA, exhibit two Tgs in their DSC thermograms. Phase separation is found to occur in the latex particles during polymerization. The heterogeneous distribution of monomers in particles, in which a relatively rich MMA region exists in the shell and a relatively rich n‐BuA region exists in the core of the particles, is assumed to arise from phase separation. The average copolymer composition and the fraction of the two domains are estimated. The polymerizatrion course and particle size growth follow the linear X vs. t2 and Dp3/2 vs. t relationships, respectively. Although the coagulation of particles happens after around 30 percent conversion, the polymerization behaviors, except for increasing rates, are not affected.
Effects of phase separation on the mechanical properties of polystyrene/poly(vinyl methyl ether) blends
Authors: Kim J. H. , Karasz Frank E. , Malone M. F. 
Published: May 2005

AbstractThe effects of phase separation temperature and time on the tensile, dynamic mechanical, and tear properties of blends of polystyrene and poly(vinyl methyl ether) were investigated after phase separation above their respective cloud points with specified temperature‐annealing time protocols. The results are analyzed in terms of the phase connectivity, interfacial adhesion, and changes in the glass transition temperature.
Crystallization characteristics of isotactic polypropylene with and without nucleating agents
Authors: Kim Young Chul , Kim Chung Yup , Kim Sung Chul 
Published: May 2005

AbstractNucleation effects of two sorbitol derivatives on the crystallization of isotactic polypropylene (iPP) were studied by means of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). A nonisothermal crystallization kinetic equation was employed to analyze the crystallization characteristics of iPP with or without the nucleating agents from DSC crystallization thermograms. The equilibrium melting temperature of iPP necessary for the kinetic study was obtained by the extrapolation method to be 209°C. The nonisothermal crystallization kinetic analysis for the unnucleated iPP at different cooling rates was possible by assuming the spherulite growth initiated simultaneously by heterogeneous and homogeneous nucleation. On the other hand, the crystallization kinetics of the nucleated iPP could be described by the heterogeneous nucleation and growth process alone. The addition of the nucleating agents up to their saturation concentrations in iPP increased the crystallization peak temperature by 17°C, and the number of effective nuclei by three orders of magnitude. A high concentration of the nucleating agents caused agglomeration of the agents to lower the number of effective nuclei.
An assessment of cogswell's method for measurement of extensional viscosity
Authors: Kwag C. , Vlachopoulos J. 
Published: May 2005

AbstractCogswell's method for measurement of extensional viscosity by determining the entry pressure loss in capillary viscometry is critically examined. Comparisons are made between extensional viscosity values introduced in finite element calculations as input data and predictions based on the calculated entry pressure losses for polymer melts. The calculated pressure losses are in good agreement with experimental data by Laun and Schuch. An equation proposed by Cogswell and another by Binding are used in the extensional viscosity comparisons. The slope of the extensional viscosity versus stretch rate is predicted rather well, but the calculations can shift the results above or below the true values.
Properties and morphology of polystyrene and linear low density polyethylene polyblend and polyalloy
Authors: Teh J. W. , Rudin A. 
Published: May 2005

AbstractA co‐rotating twin screw extruder was employed in melt mixing and reactive extrusion of polystyrene/linear low density polyethylene (PS/PE) blends. Blends of PS/PE in the ratio of 9: 1 were prepared under different conditions of shear mixing and with different concentrations of dicurnlyl peroxide (DP) and triallyl isocyanurate (TALC) coupling agent. The Charpy impact strength of unnotched samples of melt blends was found to be lower than that of the polystyrene and was not affected much by the different conditions of melt mixing at different rates of extrusion, screw speeds, and screw configurations. In the case of reaction‐extruded blends, the impact strength initially deteriorated with small addition of TAIC/DP, but improved with further increase in the level of TAIC/DP, exceeding that of polystyrene at an optimum concentration. With even further increase in TAIC/DP concentration, the impact strength again decreased. This was attributed to the different extents of coupling reactions of PE‐TAIC‐PE, PE‐TAIC‐PS, and PS‐TAIC‐PS with different levels of TAIC/DP. The interfacial adhesion of the incompatible PS‐PE was postulated to be improved by the graft copolymers formed during reactive extrusion. This observation was supported by melt rheology, thermal characterization, molecular weight, and fracture surface morphology studies.
Orientation of precrystallized poly(ethylene terephthalate)
Authors: Jabarin S. A. 
Published: May 2005

AbstractThe orientation characteristics of crystalline poly(ethylene terephthalate), PET, were studied as a function of degree of crystallinity, orientation temperature, and stretch ratio. Oriented samples were analyzed with respect to mechanical, shrinkage, and barrier properties. The results show that (a) significant impact property improvement can be achieved by orienting crystallized PET, (b) the modulus, ultimate strength, and yield stress increase with orientation of precrystallized PET, (c) the initial degree of crystallinity can affect the strain‐hardening properties of PET, and (d) the total amounts of shrinkage and shrinkage stress of stretched PET increase with increasing amounts of crystallinity before orientation.
Pultruded fiber reinforced thermoplastic poly(methyl methacrylate) composites. Part I. Correlation of processing parameters for optimizing the process
Authors: Ma Chen‐Chi M. , Chen Chin‐Hsing 
Published: May 2005

AbstractThe effect of processing parameters on the properties (tensile, flexural strength and modulus and impact strength, etc.) of pultruded fiber reinforced poly(methyl methacrylate) (PMMA) composites has been studied. The processing parameters investigated included pulling rate, die temperature, and postcure. Wetting of fibers by PMMA resin was complete, and the fiber bundles were evenly distributed in the PMMA matrix. The conversion, molecular weight and viscosity of MMA prepolymer were studied by 1H‐NMR, GPC and Brookfield viscometer. The optimum die temperature was determined from DSC diagram, molecular weight measurement and from the polymerization rate. The mechanical properties increased with the increasing postcure temperature and decreasing pulling rate and die temperature.
Injection mold flashing of liquid crystalline polymers
Authors: Wissbrun Kurt F. 
Published: May 2005

AbstractThermotropic polyesters, such as Vectra (Hoechst Celanese), have excellent moldability for intricate parts that require high precision of form, such as electronic connectors. Two apparently contradictory aspects of molding behavior contribute to the moldability. On the one hand, the low viscosity of the liquid crystalline polymer (LCP) at high shear rates favors ease of filling molds that contain long, thin paths. On the other, parts molded from LCP have little or no flash to interfere with the functioning of the parts.There has apparently been little work on the rheological aspects of flash formation. An approximate analysis is made by considering that the flash is the result of melt being extruded from the mold cavity into a slit at the mold parting line. The driving force for the extrusion is the injection pressure. The flow is assumed to be isothermal until solidification occurs, at a time that depends on the thickness of the slit, on the thermal diffusivity of the melt, the melt and mold temperatures, and on the solidification temperature of the material. The viscosity is assumed to have power‐law dependence on shear rate. It is found that when the aspect ratio (length to thickness) of the flash is small, its length is strongly dependent on the magnitude of the pressure drop at the contraction from the cavity to the slit.At the minimum pressure required to fill a mold, the flash length is predicted to be independent of the rheological and thermal properties of the melt, except for the power‐law exponent. Differences in end correction can, however, account for different tendencies to flash at equal moldability.Comparison of the model with Richardson's analysis of freezing in a cavity suggests a correlation of the thermal properties of the melt with his parameter c, which is related to mold filling ability. Tests of the model and possible refinements are suggested.
Optimization of the polymer melt thickness distribution on a cable of large diameter
Authors: Hanssen D. M. 
Published: May 2005

AbstractA numerical method for analysis of isothermal non‐Newtonian polymer melt flow in narrow channels of complex shape is described. This method is applied to the flow in a cable‐covering crosshead. The volumetric flow field is calculated and the melt thickness distribution proves to be strongly nonuniform. A series of modified cannel geometries are suggested and the volumetric flow rates in these channels are calculated. One of these channels, which gives a substantially more uniform unsulation thickness, is shown as an improved channel design.
Effect of filler content and additives on the extrudate swell of polyethylene pipe resin
Authors: Mijangos‐Santiago F. , Dealy J. M. 
Published: May 2005

AbstractIn certain extrusion operations, particularly the production of plastic pressure pipe, it would be desirable to be able to control the degree and direction of molecular orientation. While dies can be designed to generate various types of orientation, most of this is lost at the die exit due to extrudate swell. It is known that substantial loadings of nonreinforcing filler can inhibit swell, and the objective of this study was to examine the effects of particle size and loading and of the use of coupling agents on extrudatee swell of CaCO3‐filled medium‐density polyethylene pipe resin. Swell was measured as a function of time by extruding into oil having the same density and temperature as the extrudate. In addition, the storage and loss moduli of all samples were measured, and, the relaxation spectra were calculated. The maximum degree of swell suppression was observed for a compound containing 30 wt. percent of 0.4 micron particles treated with stearic acid. Surprisingly, the use of coupling agent increased the degree of swell.
Analysis of unsaturated polyester‐polyurethane interpenetrating polymer networks. I: Reaction kinetics and viscosity model
Authors: Lee Sun Suk , Kim Sung Chul 
Published: May 2005

AbstractThe reaction kinetics and viscosity behavior during the reaction injection molding (RIM) process of unsaturated polyester (UPE)‐Polyurethane (PU) interpenetrating polymer networks (IPNs) were studied. The interaction between the reactants of the component polymers was reflected in the reaction kinetic model. The intermediate reaction products having a certain conversion level were prepared in order to obtain the conversion dependence of viscosity. The composition dependence of blend viscosity was also evaluated for, the oligomeric mixture.
Visco‐elastic properties related to the phase morphology of 60/40 PC/SAN blend
Authors: Quintens D. , Groeninckx G. , Guest M. , Aerts L. 
Published: May 2005

AbstractStress relaxation and dynamic mechanical measurements have been performed on a 60/40 blend of polycarbonate of bisphenol A (PC) and poly (styrene‐co‐acrylonitrile) (SAN). This paper clearly demonstrates that the phase morphology of an immiscible co‐continuous polymer blend is an important parameter in determining visco‐elastic behavior. The dynamic mechanical properties are discussed in terms of the visco‐elastic form of a Kerner equation as a function of the reciprocal Chalkey parameter, which has been used to quantify the co‐continuous phase morphology. The effective volume fraction of the SAN phase has been found to decrease as the phase structure coarsens during annealing above Tg of both SAN and PC. This is probably the result of phase break‐up and subsequent inclusion of SAN domains in the PC matrix during the coarsening process, which modifies the structure produced during melt compounding and injection molding.
Anisotropic in‐plane permeability of fabric media
Authors: Chan Albert W. , Hwang Sun‐Tak 
Published: May 2005

AbstractAn elegant procedure is proposed for obtaining components of the orthotropic or anisotropic in‐plane permeability tensor from experimental data on flow front position and time. A radial flow geometry allows the shape of the advancing flow front to be dictated by the in‐plane permeability of the fabric media. The directional permeabilities in the fabric plane are directly calculated from fluid and fabric properties together with data from the mold filling experiment (resin injection pressure and flow front position with time). The simplicity of the apparatus and proposed analytical procedure permit easy testing and comparison of different types of fibrous media.
Fiber pull out experiments with thermoplastics
Authors: Piggott M. R. , Dai S. R. 
Published: May 2005

AbstractSingle glass and Kevlar fibers were embedded in a ductile low density polyethylene and the forces required to pull them out were measured. The plot of debonding force vs. embedded length was not a straight line, and involved a maximum Edear stress of up to 15 MPa, which was greater than the estimated shear strength of the polyethylene. Debonding appeared to be a brittle fracture process, with a work of fracture of 110 Jm−2or less.
Application of the microbond technique: Characterization of carbon fiber‐epoxy interfaces
Authors: Biro David A. , McLean Paul , Deslandes Yves 
Published: May 2005

AbstractMicrobonding has been applied to measure the interfacial shear strength, τ, between single carbon fiber and microdroplets of epoxy resins. The effect of thermoset cure and resin modification on this initial parameter for composite performance have been studied. The interfacial shear strength for the host fiber/epoxy system (T‐300/Epos 828) increased 3 fold from a B‐stage to a fully cured material. The addition of a toughening agent called “Fortifier P” to the host resin system increased T by 40%. Residual thermal stresses were calculated and their contribution to mechanical adhesion were related to friction components.
Crystallization behavior of polyphenylenesulfide
Authors: Budgell Derek R. , Day Michael 
Published: May 2005

AbstractThe crystallization behavior of poly(phenylene sulfide) (PPS) has been examined by differential scanning calorimetry as a function of melt temperature, residence time in the melt, and the presence of a liquid crystal polymer. The results suggest that the thermal history of the sample plays an important role in determining the crystallization kinetics. Short residence times at low melt temperatures and high melt temperatures alone resulted in a low value for the Avrami exponent n. The former effect was ascribed to incomplete melting of the polymer while the latter effect was attributed to thermal degradation. Blending a liquid crystal polymer, Vectra A950, with PPS had only a minor effect on the crystallization behavior.
Impact‐Induced delamination in [05, 905, 05] carbon fiber/polyetheretherketone composite laminates
Authors: Wang Hao , Vu‐Khanh Toan 
Published: May 2005

AbstractThis paper reports both experimental and numerical investigations on delamination mechanisms in [05, 905, 05] carbon fiber(CF)/poly(etheretherketone) (PEEK) laminate subjected to low‐velocity impact. It was found that the CF/PEEK composite exhibits the same damage mechanisms as epoxy‐based composites, but superior delamination resistance. For the crossply laminate, the impact delamination results from a Mode II interlaminar fracture process, and a close association exists between the interlaminar shear stress field and the delamination growth. The prediction of impact‐induced delamination sizes is discussed.
Effect of winding tension and cure schedule on residual stresses in radially‐thick fiber composite rings
Authors: Aleong C. , Munro M. 
Published: May 2005

AbstractIn filament winding, both the tension applied to the fiber strands and the subsequent cure schedule are important manufacturing variables that produce residual stresses and strains. A “radial cut method” was used to determine the circumferential and radial residual stress profiles in S2‐glass fiber/epoxy and E/XA‐A carbon fiber/epoxy circumferentially‐wound composite rings. Of particular interest in this study were radially‐thick composite rings in which the effect of cure schedules as well as constant and variable winding tension profiles on the radial residual stress profiles were evaluated. Several design‐oriented relationships for estimating the maximum radial residual stress were developed.
Dynamic modeling of the mold filling process in an injection molding machine
Authors: Chiu Cheng‐Ping , Shih Laming‐Chang , Wei Jong‐Hwei 
Published: May 2005

AbstractThis paper presents the development of a nonlinear mathematical model for the study of the mold filling process in an injection molding machine. The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics. The mold filling process can be approximated by the transient phenomenon of the non‐Newtonian fluids flowing through a closed conduit. The comparison between the experimental results and the theoretical simulation indicate that the nonlinear model is a reasonable representation of the mold filling dynamics when the acrylonitrile‐butadiene‐styrene (ABS) is injected into a disk shape mold. The actuation system dynamics of an injection molding machine are also investigated. The results indicate that the nonlinear model can also adequately predict the transient behavior of the actuation system.
Quantitative prediction of particle size of dispersed phase in elastomer‐plastic blends
Authors: Zhang Zhongyue , Qiao Jinliang 
Published: May 2005

AbstractIn investigating the relationship between the particle size of the dispersed phase in a polymer blend and the physical properties of the resulting product, the effects of conditions of blending, viscosity difference, and volume fraction, etc., are usually observed and studied. This approach is uncertain since blending is a complex process. From a theoretical background similar to that of N. Tokita's, but using a different mathematical and experimental treatment, a complex factor composed of shear rate, apparent viscosity of the system, and volume fraction of the dispersed phase is proposed. This factor is found to provide a linear relation with the mean radius of dispersed particles as expressed by

where R is the mean particle radius in the dispersed phase; S is shear rate of mixing;, V is apparent viscosity of the system; F is volume fraction of the dispersed phase; B is an experimental constant relating to breaking energy of the dispersed phase and interfacial tension; and A is also a constant relating to interfacial tension and the probability that a collision will result in a coalescence.
Photoinitiated crosslinking of low density polyethylene I: Reaction and kinetics
Authors: Qing Yan , Wenying Xu , Rånby Bengt 
Published: May 2005

AbstractThe kinetics of the reaction in photocrosslinking of the low density polyethylene‐benzophenone‐triallyl cyanurate (LDPE‐BP‐TAC) system was studied by theoretically deriving a kinetic equation and comparing it with the results from crosslinking, extraction and swelling experiments. It was found that the rate of crosslinking is proportional to the square of light intensity. The roles of the crosslinker (TAC) were to capture the excited initiators efficiently to form free radicals and to act as a carrier of the active radicals. The ratio of degradation/ crosslinking was extrapolated to be around 0.28, and compared with 0.44 in the γ‐irradiation process for the same material.
Slit die flow measurements of a liquid crystalline polyesteramide and its blends with polyarylate
Authors: Zaldua Ane , Muñoz Eudenia , Peña Juan J. , Santamaria Anton 
Published: May 2005

AbstractA commercial thermotropic polyesteramide and its blends with polyarylate are the object of a slit die flow rheological study. The measurements are carried out at 280°C, a temperature slightly above the melting temperature of the thermotropic, covering a shear rate range 10−1 s−1 to 102s−1. Except in the case of the thermotropic polymer, the pressure profiles are upward parabolic which is attributed to the dependence of the viscosity on pressure. The most striking result is the observed downward curvature in pressure profiles obtained for the liquid crystalline polyesteramide: no explanation is given for this phenomenon, for the present. The elasticity of the polymer melts is expressed in terms of the exit pressure and the extrudate swell. The thermotropic polyesteramide presents negative values of both parameters (e.g. samples shrink instead of swell). Viscosity and elasticity present negative deviation from linearity when plotted against composition; this reduction in the rheological functions, caused by the addition of liquid crystal, is more pronounced at high shear rates.
Viscoelastic properties of a 60 mol% para‐hydroxybenzoic acid/40 mol% poly(ethylene terephthalate) liquid crystalline copolyester. I: Effect of temperature history
Authors: Hayase S. , Driscoll P. , Masuda T. 
Published: May 2005

AbstractIn this paper, the rheology of a 60 mol% para‐hydroxybenzoic acid (PHB)/40 mol% poly(ethylene terephthalate) (PET) copolyester (herein referred to as PHB60/PET40) produced by Unitika Co., Japan, was investigated using viscoelastic property temperature sweeps. In addition to the large‐scale hysteresis (super‐cooling) of viscoelastic properties that has also been seen with other PHB‐based materials, in which it is possible for several PHB linkages to occur side by side along the polymer backbone (most notably the PHB60/PET40 polymer produced by Tennessee Eastman), smaller‐scale viscoelastic transitions, one present in heating, and believed to be associated with the partial isotropization of liquid crystalline material, and the other apparent on cooling, occurring at a lower temperature than the first and thought to be associated with the opposite process, were observed. When overall mol% PHB composition along individual chains is considered, the well‐defined appearance of the additional smaller‐scale rheological transitions seen here is believed to be due to a unimodal composition distribution, rather than a bimodal distribution of which there is increasing evidence in the Tennessee Eastman materials. This difference is believed to be caused by differences in the preparation technique used for the Unitika version of the polymer.