bluuebunny/crossref_metadata_2025 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

The 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

The 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

Nucleation 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

Cogswell'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

A 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

The 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

The 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

Thermotropic 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

A 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

In 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

The 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

Stress 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

An 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

Single 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

Microbonding 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

The 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

This 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

In 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

This 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

In 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

The 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

A 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

In 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.
Analysis of the effects of internal heating and cooling during the rotational molding of plastics
Authors: Sun Da‐Wen , Crawford Roy J.
Published: May 2005

In rotational molding, shortening the cycle time is one of the most important requirements for increasing production rates and reducing product cost. A characteristic feature of the process is that the mold and plastic powder are heated from room temperature to the melting temperature of the plastic and then back to room temperature. In addition, in the vast majority of cases the heat input and subsequent heat extraction occur at the outside surface. In order to improve the heat transfer, this paper considers the effects of internal heating and cooling. A mathematical model has been developed in which an internal heating term can be incorporated. The experiments with rotomolding powders show that the predictions made by the model are accurate. In particular, it is found that the introduction of internal heating is very effective in shortening the cycle time and that the introduction of internal cooling in rotational molding provides a more uniform structure and less likelihood of warpage.
Measurement and correlation of mutual diffusion coefficients for styrene‐butadiene rubber(SBR)‐n‐nonane systems
Authors: Iwai Yoshio , Miyamoto Shinji , Ikeda Hideaki , Arai Yasuhiko , Kobuchi Shigetoshi , Sano Yuji
Published: May 2005

The mutual diffusion coefficients for styrene‐butadiene rubber(SBR)‐n‐nonane systems were measured using a sorption apparatus with a quartz spring at 100 and 130°C for mass fractions of n‐nonane ranging from 0 to 0.16. The mutual diffusion coefficients were correlated with good agreement by the free‐volume theory.
Dynamic mechanical properties of poly( ε‐caprolactam)/polypropylene alloy
Authors: Wippler C.
Published: May 2005

The results of a round‐robin testing on the dynamic mechanical properties of a poly(ε‐caprolactam)/polypropylene PA‐6/PP compatibilized blend (an alloy) are reported. The alloy was a commercial product (Orgalloy R‐6000, from Atochem). The samples were prepared by extrusion, injection or compression molding. The greatest difficulty in comparing the data arose from the moisture content since the position of the PA‐6 transition peaks depend on the drying conditions. For the extruded specimens only minor effects could be attributed to the anisotropy introduced by the extrusion process. Overall, there was good agreement between the contributing laboratories for the frequency dependence of the transition peaks, but agreement between the measured values of the storage moduli was poor. This discrepancy is suspected to be partially due to the differences in sample geometry and in the processing conditions.
Filling of a complex‐shaped mold with a viscoelastic polymer. Part II: Comparison with experimental data
Authors: Kamal M. R. , Papathanasiou Thanasis D.
Published: May 2005

An experimental program has been carried out on a reciprocating screw injection molding machine in order to establish the validity of a proposed mathematical model for the filling stage of injection molding. A cavity of complex shape with an insert and variable thickness was constructed and used in these experiments. Good agreement between predicted (through computer simulation) and observed (through short‐shot experiments and transducer response) results is obtained for free surface shapes and free surface locations with time. The theoretical pressure predictions are in fairly good agreement with experiments, with the maximum deviations occurring towards the end of filling and for longer filling times. This points towards the possibility that wall solidification during filling interacts with the flow processes across the gap of the cavity and makes necessary a more detailed characterization of the heat transfer at the melt/mold interface.
Pneumatic bursting characteristics of plastics films
Authors: Tseng H. H. , Lai F. S. , Lee C. K.
Published: May 2005

The bursting strength and inflated deflection of linear low density polyethylene (LLDPE), oriented polypropylene (OPP), flexible poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET), and polyurethane (PUR) films of different thicknesses were investigated with the pneumatic bursting method. The study showed the bursting air pressure is directly proportional to the thickness of LLDPE, OPP, and PET films. The effect of different membrane diameters on the change of the bursting properties in OPP and PUR film was also investigated. The results showed that the bursting properties are inversely proportional to the membrane diameter. Furthermore, biaxial stress‐strain exerted on the pole region of the tested films was studied. The results denoted that the relationship between the biaxial and uniaxial tensile stress‐strain was considered for two types of film: (1) Film that presented an isotropic tensile behavior showed that the tangential stress‐strain is higher than the tensile stress‐strain. (2) Film that presented an anisotropic tensile behavior showed that the tangential stress‐strain is determined by the weaker tensile stress‐strain values between two directions.
Model filled polymers. XIV: Effect of modifications of filler composition on rheology
Authors: Sun Liqing , Aklonis J. J. , Salovey R.
Published: May 2005

Steady shear vxiscosity, dynamic moduli and the appearance of fracture surfaces of model composites, consisting of monodisperse crosslinked polymeric spheres of varied composition in a polymethyl‐methacrylate matrix, depend on the compatibility of filler particle and matrix. After intensive mixing, “compatible” systems form uniform and stable dispersions. Filler particles cluster in incompatible composites producing a highly non‐Newtonian response. At 40 w% filler, yield behavior results, with a yield stress of 3100 Pa for polystyrene particles and 1900 Pa for copolystyrene‐acetoxystyrene particles. The flow properties of compositionally complex particles from seeding are determined by particle surface composition.
Studies on miscibility of blends of ethylene methyl acrylate and polydimethyl siloxane rubber
Authors: Santra Robin N. , Roy Sanjoy , Bhowmick Anil K. , Nando G. B.
Published: May 2005

Blends of ethylene methyl acrylate (EMA) and poly(dimethylsiloxane) rubber (PDMS) are demonstrated to be miscible. The miscibility results in a single and composition‐dependent glass transition temperature. IR spectra of the blends provide direct evidence of chemical reaction between EMA and PDMS rubber.
Double Arm pulfrich refractometer: Application to the optical characterization of biaxially stretched polystyrene
Authors: Warenghem M. , Lefebvre J. M.
Published: May 2005

An experimental setup is presented that enables the whole optical characterization of an anisotropic medium to be achieved at the same spot. Based on total internal reflection measurements, the Double Arm Pulfrich Refractometer provides high precision simultaneous refractive index data, which are gathered without moving the sample. This technique is particularly well suited to the case of biaxial materials. Illustration of its potential is given on some preliminary orientation measurements of biaxially stretched polystyrene films.
Energy absorbing double‐beam concept for thermoplastic automotive bumpers
Authors: Stokes Vijay K.
Published: May 2005

Because of the inability of existing automotive bumpers to absorb energy during impacts over the supports, energy absorbers have to be used to make bumpers effective in barrier impacts. A parametric analysis of a novel double‐beam bumper concept has shown that its performance, in terms of energy absorption and impact forces, is insensitive to the location of the point of impact. Physical realizations of this concept, which may not require more material than existing designs, and which are particularly suited to thermoplastic materials, have been developed.
Reaction mechanisms of polyacrylonitrile on thermal treatment
Authors: Kim J. , Kim Y. C. , Ahn W. , Kim C. Y.
Published: May 2005

A high‐temperature radical scavenger, 2,2‐diphenyl‐l‐picryl hydrazyl (DPPH), has been used to study the reaction mechanisms of polyacrylonitrile (PAN) on thermal treatment. The effect of DPPH on the cyclization reaction of PAN in both air and nitrogen, investigated by differential scanning calorimetry (DSC), helped to verify the proposed reaction mechanisms, i.e., the free radical and the ionic ones. For PAN homopolymer, the peak temperature of the reaction exotherm shifted to higher temperatures and the heat of reaction was decreased with increasing DPPH concentration. For PAN copolymer with methylacrylate and itaconic acid, however, the effects of DPPH on DSC thermograms were insignificant. The effects of IPPH suggest that the reaction of the nitrile groups proceeds by free radicals for the homopolymer while by ions for the copolymer. The activation energies for the thermal reactions of PAN in both air and nitrogen were also estimated by the dynamic DSC method, and they proved to be highly dependent on reaction mechanism, environment of thermal treatment, and DPPH concentration.
A predictive model for the mechanical behavior of particulate composites. Part I: Model derivation
Authors: Vratsanos Lori Anderson , Farris Richard J.
Published: May 2005

A method for predicting the highly nonlinear stress‐strain behavior and dilatation induced by cavitation of highly filled particulate composites from constituent properties has been developed. The approach presented uses a variation of linear elasticity throughout and has no adjustable parameters, unlike the methods currently used, which require large numbers of fitting factors and complicated nonlinear analyses. An energy balance derived from the first law of thermodynamics calculates critical strain values at which filler particles will debond when subjected to deformation. Repeated calculations of critical strain values using re‐evaluated material properties accounting for the damage caused by debonding give very nonlinear stress‐strain and dilatation curves. Experimentally observed dependencies on particle size, filler concentration, adhesion, and matrix and filler properties are correctly predicted. The method can be generalized for any state of stress or particle shape. Comparisons of experimental data with the model results give good agreement.
Thickness‐direction thermal expansion of polyimide films
Authors: Tong H. M. , Saenger K. L. , Su G. W.
Published: May 2005

The coefficient of thermal expansion (CTE) for thin polymer films is a property of considerable practical importance. In contrast to the abundance of CTE data in the in‐plane or film direction, data in the thickness or z‐direction is rarely available, in part due to the high sensitivity required for measurement of the small thickness changes involved. In this paper, we will describe both a capacitance change and a Fabry‐Perot laser interferometric method for measuring z‐direction CTE's. Results are presented for a variety of commercially available polyimide films of thickness 50 to 130 μm. Upilex and Kapton were found to have z‐direction CTE's of about 55 and 81 ppm/°C, respectively. These CTE's for the thickness direction are many times higher than the corresponding values in the in‐plane direction. This anisotropy is attributed to the preferential in‐plane molecular orientation of the polymer chains.
Estimation of critical stability parameters by asymptotic analysis in multilayer extrusion
Authors: Anturkar Nitin R. , Wilkes James O. , Papanastasiou Tasos C.
Published: May 2005

In industrial coextrusion operations, multiple layers are frequently brought in contact with each other at different temperatures to “match” viscosities and to reduce interfacial instability. Here, a linear stability analysis of multilayer plane Poiseuille flow is carried out for real, specific polymer melts in terms of process parameters, such as temperatures and flow rates. However, heat transfer across the layers is neglected as a first approximation. Previously, it was observed that below a certain Reynolds number and above a certain relaxation time, the flow‐rate ratio (or the depth ratio), above which the flow is stable to all wavelengths, can be estimated by the long‐wavelength asymptotic analysis (1,3). The Reynolds numbers for the industrial flows are smaller, and the relaxation times are larger than the corresponding critical values by several orders of magnitude. Therefore, the critical stability parameters can be estimated in the present study for industrial cases using the asymptotic stability analysis at long wavelengths. Although a large number of earlier parametric studies of model fluids indicate the influence of various theological parameters, only the viscosity stratification plays an important role in the interfacial instability within the operating range of industrial coextrusion processes.
Impact toughening mechanisms in rubber‐dispersed polymer alloy
Authors: Okamoto Y. , Miyagi H. , Uno T. , Amemiya Y.
Published: May 2005

The toughening mechanisms of rubber‐dispersed polymer alloys were investigated with respect to two factors: (i) characteristic ratio, C∞, as a measure of chain flexibility of the polymer matrix and (ii) the rubber particle size in high impact polystyrene/poly(2,6‐dimethyl‐ 1,4‐phenylene ether) blend systems. Measurements of the specific gravity, synchrotron radiation small angle X‐ray scattering (SR‐SAXS) tests, and finite element analysis were carried out to gain understanding of plastic deformation (crazing and shear yielding) of these materials. Shear yielding was found to be enhanced when the C∞ value of the matrix polymer was relatively low and the rubber particles were small (submicron). From these results, we presumed the impact energy absorption mechanisms to be governed by these two factors.
Effects of kinetic and transport parameters on accelerated migration of reactive additive from plastic sheet
Authors: Atiqullah M. , Shamsur Rahman A. K. M. , Zaidi S. M. J.
Published: May 2005

The effects of kinetic parameters Hatta number Ha and ϕ, and transport parameters Biot number Bi and ψ on the migration of a reactive additive have been modeled. The convective boundary layer can be considered inert to fully reactive for Ha → 0 to 2, respectively. The migration is controlled by diffusion, reaction rate, equilibrium partitioning of the migrant between the plastic film and the solvent, and boundary layer resistance, depending on the time scale and values of the above parameters. For a nonreactive boundary layer, at high Bi, migration is initially diffusion‐controlled but becomes reaction‐rate controlled at later times. However, under similar conditions, a slight increase in the reactivity of the boundary layer immediately changes the transport process from diffusion‐controlled to reaction rate‐controlled. With further increase in reactivity, migration spontaneously reaches equilibrium. At low Bi, equilibrium partitioning and reactive depletion of the migrant in the fluid phase change predominantly to boundary layer‐controlling mass transport phenomenon. For a given sampling time (τ = 1.0), the migration increases with the increase in Bi only for a reactive boundary layer. At low Bi and (τ = 1.0), migration decreases only up to ϕ ≅ 0.3 for nonreactive to partially reactive boundary layer, but for intermediate and high Bi, ϕ and Ha do not influence migration.
High temperature thermosets based on the cocuring of a novel spirodilactam bisallylether and bismaleimide
Authors: Chuah Hoe H. , Wang P. C.
Published: May 2005

Spirodilactam bisallylether is a new high temperature performance monomer. It melts at 154°C, and is thermally inactive in forming a homopolymer. However, it reacts readily with a bismaleimide via “ene” reaction. Therefore, it could be used as a comonomer and an effective toughening modifier for bismaleimide. The properties of the blends of spirodilactam bisallylether and 4,4'‐bismaleimidodiphenyl‐methane were studied. The cocured resins have high glass transition temperature, > 300°C. By adding 30 to 40 mole % of the bisallylether, the compact tension toughness of the bismaleimide was improved to 0.7 MPa‐m1/2. Therefore, the resins have a combination of high glass transition temperature and toughness. They also showed good flexural properties. Despite the high water absorption, 5 to 7%, the resins retained high hot/wet flexural properties because of the high glass transition.
Viscoelasticity of some engineering plastics analyzed with the modified stress‐optical rule
Authors: Hwang Eui Jeong , Inoue Tadashi , Osaki Kunihiro
Published: May 2005

The complex Young's modulus, E*(ω), and the complex strain‐optical coefficient, O*(ω), of poly(ether sulfone) (PES), polysulfone (PSF), and polyethermide (PEI), were measured over the frequency range 1 to 130 Hz. The data were analyzed with a modified stress‐optical rule: The Young's modulus was decomposed into two complex functions, E(ω) and E(ω); the modified stress‐optical coefficient, CR and CG, associated with the rubber (R) and glass (G) components, respectively, were determined. The results for six polymers, including polystyrene, poly(α‐methyl styrene), and bisphenol A polycarbonate were compared with each other. One of the coefficients, CR, equivalent to the stress‐optical coefficient in melts, mainly depended on the way in which phenyl groups were connected to the chain. The other, CG, was in the range of 20 to 40 Brewsters, and did not strongly depend on the details of polymer structure. The component function, E(ω), which was located in the glassy region and originated from the high glassy modulus, was almost the same in shape when plotted against ω with double logarithmic scales. The R component, E(ω), located at the long time end of the glass‐to‐rubber transition zone, was slightly sensitive to the molecular structure of polymers.
A closer look at the MWD‐viscosity transform
Authors: Shaw Montgomery T. , Tuminello William H.
Published: May 2005

While there is abundant evidence that the molecular weight distribution (MWD) of a linear polymer has an influence on the shape of the viscosity function, the ability to convert the viscosity function to an MWD has been questioned. Using strictly numerical techniques, we have shown that the viscosity function can be transformed to the MWD, but always with some distortion. However, distinct bimodality can be qualitatively preserved through both the MWD‐viscosity and viscocity‐MWD transforms.
Analysis of a reactor with surface renewal for poly(ethylene terephthalate) synthesis
Authors: Yoon K. H. , Park O. O.
Published: May 2005

A mathematical model of a polycondensation reactor that can be used in the final stage for poly(ethylene terephthalate) (PET) is established and compared with experimental data obtained from a laboratory scale reactor with film renewal. Detailed side reactions are considered along with the diffusional removal of the small molecules through thin film. Among several kinetic constants, the polycondensation reaction rate constant k1(= k8) and diester group degradation reaction rate constant k7 have an influence over the degree of polymerization. The values of k1(= k8) and k7 for 0.05 wt% Sb2O3 were obtained as curve‐fit values: (1) k1(= k8) = 3.4 × 106 exp(− 18.500/RT′) (L/mol‐min); (2) k7 = 1.3 × 1011 exp(− 37,800/RT′) (min−1). Effects of the film exposure time, reduced pressure of vacuum, temperature, the initial terephthalic acid (TPA)/ethylene glycol (EG) mole ratio, the initial degree of polymerization, and catalysts were well explained by the model.
The effect of annealing on stretched trans‐1,4‐polyisoprene networks
Authors: Chou Der‐Gun , Smith K. J.
Published: May 2005

Variations of stress with temperature for stretched networks of trans‐polyisoprene networks in the crystallization region are reported. Such profiles are characteristically U‐shaped with the stress at lower temperatures often climbing to high levels. Valley widths of the profiles narrow as annealing temperature increases to about 50°C, then widen at yet higher temperatures. The degree of crystallization at 22°C is 37% and independent of deformation and annealing temperature. The β crystal form is overwhelmingly present with traces of other crystal forms appearing only at high deformations. The theory of stress‐induced crystallization provides a good description of experimental results provided the nucleation parameter σ is dependent upon deformation. Therefore, the data provide good qualitative support for the theory in its current form.
Mechanical properties and deformation mechanism of polyoxymethylene chain in the crystalline state
Authors: Tashiro Kohji , Kobayashi Masamichi , Tadokoro Hiroyuki
Published: May 2005

The true crystallite modulus of polyoxymethylene (POM) was evaluated experimentally and thoeretically as a function of temperature. The mechanical deformation mechanism of POM was lattice‐dynamically predicted and confirmed by measuring the stress‐induced vibrational frequency shifts of the infrared and Raman spectra, which were interpreted on the basis of anharmonic potential field.
Functionalized elastomeric compatibilizer in PA 6/PP blends and binary interactions between compatibilizer and polymer
Authors: Holsti‐Miettinen R. M. , Seppälä J. V. , Ikkala O. T. , Reima I. T.
Published: May 2005

Superior impact properties were obtained when maleic anhydride grafted styrene ethylene/butylene styrene block copolymer (SEBS‐g‐MAH) was used as a compatibilizer in blends of polyamide 6 (PA 6) and isotactic polypropylene (PP), where polyamide was the majority phase and polypropylene the minority phase. The optimum impact properties were achieved when the weight relation PA:PP was 80:20 and 10 wt% SEBS‐g‐MAH was added. The blend morphology was systematically investigated. Transmission electron microscopy (TEM) indicated that the compatibilizer forms a cellular structure in the PA phase in addition to acting as an interfacial agent between the two polymer phases. In this cellular‐like morphology the compatibilizer appears to form the continuous phase, while polyamide and polypropylene form separate dispersions. In microscopy, PA appeared as a fine dispersion and PP as a coarse dispersion. The mechanical properties indicated that in fact PA, too, is continuous, and the blend can be interpreted as possessing a modified semi‐interpenetrating network (IPN) structure with separate secondary dispersion of PP. The coarser PP dispersion plays an essential role in impact modification. Binary blends of the compatibilizer and one blend component were also investigated separately. The same cellular structure was observed in the binary PA/SEBS‐g‐MAH blends, and SEBS‐g‐MAH again appeared to form the continuous phase when the elastomer concentration was at least 10 to 20 wt%. By contrast, in PP/SEBS‐g‐MAH only conventional dispersion of elastomeric SEBS‐g‐MAH was observed up to 40 wt% elastomer. Impact strength was improved and the elastic modulus was lowered in both PA/SEBS‐g‐MAH and PP/SEBS‐g‐MAH blends when the elastomer content was increased. The changes in modulus indicate that the semi‐IPN‐like structure is formed in the binary PA/SEBS‐g‐MAH blends as well as in the ternary structure.
Semianalytical solution for epoxy‐amine curing in the presence of nonisothermal effects
Authors: Gupta Sanjay , Agarwal B. D. , Kumar Anil
Published: May 2005

The curing of epoxy‐amine polymer has been modeled by the reaction of functional groups, and the mole balance of these is governed by a set of six nonlinear differential equations. In this work, we have first developed a complete analytical solution for isothermal curing. For nonisothermal curing, we have divided the domain of hydroxyl group concentration β into small increments Δβ and adopted our analytical results for this domain. In addition, we solved the energy balance equation analytically and obtained the temperature rise for Δβ. We have compared our results with those obtained from the Runge Kutta numerical solutions. We have shown that our semianalytical technique is about a thousand times more efficient and faster.
A property trend study of polybenzimidazole using molecular modeling
Authors: Iwamoto N.
Published: May 2005

Molecular mechanics and dynamics have become a standard analysis tool used in drug design and synthesis, but it has not generally been used as part of structural and mechanical analysis. The need for such tools is an obvious extension of structure‐property correlations known in polymer formulation, engineering, and manufacture. This study probes the use of mechanics and dynamics techniques to help explain property trends found in hydrated polybenzimidazole (PBI).